In vitro and in vivo activity of cefiderocol against Achromobacter spp. and Burkholderia cepacia complex, including carbapenem-non-susceptible isolates

Achromobacter spp. and Burkholderia cepacia complex (Bcc) are rare but diverse opportunistic pathogens associated with serious infections, which are often multidrug resistant. This study compared the in vitro antibacterial activity of the siderophore antibiotic cefiderocol against Achromobacter spp. and Bcc isolates with that of other approved antibacterial drugs, including ceftazidime-avibactam, ciprofloxacin, colistin, imipenem-relebactam, and meropenem-vaborbactam. Isolates were collected in the SIDERO multinational surveillance program. Among 334 Achromobacter spp. isolates [76.6% from respiratory tract infections (RTIs)], cefiderocol had minimum inhibitory concentration (MIC)50/90 of 0.06/0.5 µg/mL overall and 0.5/4 µg/mL against 52 (15.6%) carbapenem-non-susceptible (Carb-NS) isolates. Eleven (3.3%) Achromobacter spp. isolates overall and 6 (11.5%) Carb-NS isolates were not susceptible to cefiderocol. Among 425 Bcc isolates (73.4% from RTIs), cefiderocol had MIC50/90 of ≤0.03/0.5 µg/mL overall and ≤0.03/1 µg/mL against 184 (43.3%) Carb-NS isolates. Twenty-two (5.2%) Bcc isolates overall and 13 (7.1%) Carb-NS isolates were not susceptible to cefiderocol. Cumulative MIC distributions showed cefiderocol to be the most active of the agents tested in vitro against both Achromobacter spp. and Bcc. In a neutropenic murine lung infection model and a humanized pharmacokinetic immunocompetent rat lung infection model, cefiderocol showed significant bactericidal activity against two meropenem-resistant Achromobacter xylosoxidans strains compared with untreated controls (P < 0.05) and vehicle-treated controls (P < 0.05), respectively. Meropenem, piperacillin-tazobactam, ceftazidime, and ciprofloxacin comparators showed no significant activity in these models. The results suggest that cefiderocol could be a possible treatment option for RTIs caused by Achromobacter spp. and Bcc.

Heteroresistance to cefiderocol in carbapenem-resistant Acinetobacter baumannii in the CREDIBLE-CR study was not linked to clinical outcomes: a post hoc analysis

IMPORTANCE

The population analysis profiling (PAP) test is considered the "gold standard" method to detect heteroresistance. It exposes bacteria to increasing concentrations of antibiotics at high cell densities to detect any minority resistant subpopulations that might be missed by the low inoculums used for reference susceptibility tests. However, its clinical relevance has not been well established. In the CREDIBLE-CR study, a numerically increased all-cause mortality was observed in the cefiderocol arm relative to the best available therapy arm for patients with Acinetobacter spp. infections. Heteroresistance has independently been proposed by another research group as a potential explanation of the mortality difference. An analysis of the baseline carbapenem-resistant Acinetobacter calcoaceticus-baumannii complex isolates from patients treated with cefiderocol in the CREDIBLE-CR study showed the highest clinical cure rate and the lowest mortality for patients with PAP-heteroresistant isolates compared with PAP-susceptible or PAP-resistant isolates. These findings contradict the abovementioned hypothesis that heteroresistance contributed to the increased mortality.

In vitro efficacy of humanized regimen of flomoxef against extended-spectrum β-lactamase-producing Escherichia coli and Klebsiella pneumoniae

This study compared the efficacy of flomoxef with other β-lactam antibiotics against extended-spectrum β-lactamases (ESBL)-producing bacteria of clinical relevance. First, the prevalence and β-lactamase genotypes of ESBL-producing strains among Escherichia coli and Klebsiella pneumoniae isolates collected in Japan from 2004 to 2018 were investigated. High MIC90 values (>64 µg/mL) of ceftriaxone, cefepime, and ceftazidime and low MIC90 values (≤0.06-2 µg/mL) of flomoxef, cefmetazole, and meropenem against both species were observed. Second, a chemostat model was used to analyze the efficacy of humanized regimens of three oxacephem/cephamycin antibiotics (flomoxef, cefmetazole, cefoxitin) and two other antibiotics (meropenem and piperacillin/tazobactam) in suppressing the growth of five ESBL-producing E. coli and two K. pneumoniae strains. Flomoxef, piperacillin/tazobactam, and meropenem showed good bactericidal effects with >4 log10 CFU/mL reduction without bacterial regrowth at 24 h even when the MIC of test isolates was >MIC90. Cefmetazole and cefoxitin resulted in regrowth of test isolates with MIC ≥MIC90 at 24 h. Cefmetazole, cefoxitin, flomoxef, and meropenem showed increased MICs for regrown samples. A clear relationship between the proportion of time that the free drug concentration exceeded the MIC (%fT>MIC) and antibiotic efficacy was found for flomoxef, cefoxitin, and cefmetazole, and flomoxef had the highest %fT>MIC, whereas discrepancies between Clinical and Laboratory Standards Institute breakpoint and bactericidal activity were observed for cefmetazole. Flomoxef was effective in preventing the growth of all ESBL-producing strains, even those with an MIC eight times the MIC90. Thus, flomoxef may be a good alternative to meropenem in context of carbapenems sparing stewardship.

Cefiderocol Treatment for Patients with Multidrug- and Carbapenem-Resistant Pseudomonas aeruginosa Infections in the Compassionate Use Program

Cefiderocol is an option for infections caused by multidrug-resistant Pseudomonas aeruginosa, but its in vitro activity against these isolates and its clinical effectiveness for isolates with MICs of >1 μg/mL is unclear. We investigated the in vitro activity of cefiderocol against P. aeruginosa isolates collected from patients treated with cefiderocol through the compassionate use program and assessed physician-reported clinical response and 28-day all-cause mortality by cefiderocol MIC values. P. aeruginosa isolates underwent susceptibility testing to cefiderocol and comparator agents by using reference broth microdilution. U.S. Food and Drug Administration (FDA; susceptible, ≤1 μg/mL) and Clinical and Laboratory Standards Institute (CLSI; susceptible, ≤4 μg/mL) cefiderocol breakpoints were applied. Additionally, molecular characterization of β-lactamase genes was performed. Clinical response and vital status were reported by treating physicians. Forty-six patients with P. aeruginosa infections were evaluated. Twenty-nine (63%) and 42 (91%) isolates were susceptible to cefiderocol using FDA and CLSI breakpoints, respectively. Thirty-seven (80%) and 32 (70%) isolates were not susceptible to ceftolozane-tazobactam and ceftazidime-avibactam, respectively. The clinical response rate was 69% (20/29) with a cefiderocol MIC of ≤1 μg/mL, 69% (9/13) with a cefiderocol MIC of 2 to 4 μg/mL, and 100% (4/4) with an MIC of ≥8 μg/mL, while day 28 all-cause mortality rates were 23% (6/26; MIC ≤ 1 μg/mL), 33% (4/12; MIC, 2 to 4 μg/mL), and 0% (0/4; MIC ≥8 μg/mL), respectively. Cefiderocol was active in vitro against most P. aeruginosa isolated from patients with limited or no alternative therapies. Patients with cefiderocol MICs of 2 to 4 μg/mL did not have significantly worse outcomes than those with MICs of ≤1 μg/mL.

In vitro activity of cefiderocol against MBL-producing Gram-negative bacteria collected in North America and Europe in five consecutive annual multinational SIDERO-WT surveillance studies (2014-2019)

OBJECTIVES

To evaluate the in vitro antibacterial activity of cefiderocol, a siderophore cephalosporin against MBL-producing clinical isolates.

METHODS

MBL-producing strains were selected from clinical isolates of Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii complex collected in North America and Europe in five consecutive annual multinational SIDERO-WT surveillance studies from 2014 to 2019. MICs of cefiderocol and comparator agents were determined by the broth microdilution method according to the CLSI guideline.

RESULTS

A total of 452 MBL-producing strains consisting of 200 Enterobacterales, 227 P. aeruginosa and 25 A. baumannii complex were identified. The highest number of MBL-producing Enterobacterales strains were detected in Greece. MBL-producing strains of both P. aeruginosa and A. baumannii complex were isolated most frequently in Russia. For Enterobacterales, 91.5% or 67.5% of MBL-producing strains had cefiderocol MIC values ≤4 mg/L (CLSI susceptibility breakpoint) or ≤2 mg/L (EUCAST susceptibility breakpoint), respectively. All MIC values of cefiderocol for MBL-producing P. aeruginosa strains were ≤4 mg/L (CLSI susceptibility breakpoint), and 97.4% of them had cefiderocol MIC values ≤2 mg/L (EUCAST susceptibility breakpoint). For A. baumannii complex, 60.0% or 44.0% of MBL-producing strains had cefiderocol MIC values ≤4 mg/L (CLSI susceptibility breakpoint) or ≤2 mg/L (EUCAST pharmacokinetic-pharmacodynamic susceptibility breakpoint), respectively. Against all types of MBL-producing strains, MIC distribution curves of cefiderocol were located in the lowest numerical values, compared with other β-lactams and β-lactam/β-lactamase inhibitor combinations tested and ciprofloxacin.

CONCLUSIONS

Although the types of MBL-producing strains isolated by country varied, cefiderocol showed potent in vitro activity against all types of MBL-producing Gram-negative bacteria regardless of the bacterial species.

The prospective role of cefiderocol in the management of carbapenem-resistant Acinetobacter baumannii infections: review of the evidence

Carbapenem-resistant Acinetobacter baumannii (CRAB) has been classified by the World Health Organization as being in the critical category of pathogens requiring urgent new antibiotic treatment options. Cefiderocol, the first approved siderophore cephalosporin, was designed for the treatment of CR Gram-negative pathogens, particularly the non-fermenting species A. baumannii and Pseudomonas aeruginosa. Cefiderocol is mostly stable against hydrolysis by serine- and metallo-beta-lactamases, which are leading causes of carbapenem resistance. This review collates the available evidence on the in vitro activity, pharmacokinetics/pharmacodynamics, and efficacy and safety of cefiderocol, and outlines its current role in the management of CRAB infections. In vitro surveillance data show susceptibility rates of >90% for cefiderocol against CRAB isolates as well as in vitro synergism with a variety of antibiotics that are recommended in guidelines. The clinical efficacy of cefiderocol monotherapy against CRAB infections has been demonstrated in the descriptive, open-label CREDIBLE-CR and the non-inferiority, double-blind APEKS-NP randomised clinical trials and in real-world cases in patients with underlying health problems. To date, the frequency of on-therapy development of resistance to cefiderocol in A. baumannii appears to be low, but monitoring is highly recommended. Within current treatment guidelines for moderate-to-severe CRAB infections, cefiderocol is recommended for infections in which other antibiotics failed and in combination with other active antibiotics. In vivo preclinical data support the combination of sulbactam or avibactam with cefiderocol to enhance efficacy and to suppress emergence of resistance to cefiderocol. The benefit of combination therapy in clinical setting is yet to be determined in prospective studies.

In Vitro Activity of Cefiderocol Against Meropenem-Nonsusceptible Gram-Negative Bacilli with Defined β-Lactamase Carriage: SIDERO-WT Surveillance Studies, 2014-2019

We examined the in vitro susceptibility of meropenem-nonsusceptible Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex isolates from five consecutive annual SIDERO-WT surveillance studies (2014-2019) to cefiderocol and comparator agents in the context of their carbapenemase carriage. 1,003 Enterobacterales, 1,758 P. aeruginosa, and 2,809 A. baumannii complex isolates from North America and Europe that were meropenem nonsusceptible (CLSI M100, 2022) were molecularly characterized for β-lactamase content by PCR followed by Sanger sequencing or by whole genome sequencing. Among Enterobacterales, 91.5% of metallo-β-lactamase (MBL)-producing, 98.4% of KPC-producing, 97.3% of OXA-48 group-producing, and 98.7% of carbapenemase-negative, meropenem-nonsusceptible isolates were cefiderocol susceptible (MIC ≤4 mg/L). Among P. aeruginosa, 100% of MBL-producing, 100% of GES carbapenemase-producing, and 99.8% of carbapenemase-negative, meropenem-nonsusceptible isolates were cefiderocol susceptible (MIC ≤4 mg/L). Among A. baumannii complex, 60.0% of MBL-producing, 95.6% of OXA-23 group-producing, 89.5% of OXA-24 group-producing, 100% of OXA-58 group-producing, and 95.5% of carbapenemase-negative, meropenem-nonsusceptible isolates were cefiderocol susceptible (MIC ≤4 mg/L). Cefiderocol was inactive against A. baumannii complex isolates carrying a PER or VEB β-lactamase (n = 103; 15.5% susceptible). Ceftazidime-avibactam and ceftolozane-tazobactam were inactive against MBL-carrying and A. baumannii complex isolates; ceftolozane-tazobactam was also inactive against serine carbapenemase-carrying Enterobacterales and P. aeruginosa. In summary, cefiderocol was highly active in vitro against Gram-negative isolates carrying MBLs and serine carbapenemases, as well as carbapenemase-negative, meropenem-nonsusceptible isolates.

In vitro antibacterial activities of cefiderocol against Gram-negative clinical strains isolated from China in 2020

OBJECTIVES

Cefiderocol (CFDC) is a parenteral siderophore cephalosporin that is active against Gram-negative bacteria, including carbapenem-resistant isolates. We report the in vitro activity of CFDC and other antibiotics against 1738 clinical isolates of Gram-negative bacilli (GNB) provided by five medical centres in five provinces of China in 2020 METHODS: Antibiotic susceptibility testing was performed using the Clinical and Laboratory Standards Institute broth microdilution method.

RESULTS

Against Pseudomonas aeruginosa and Acinetobacter Spp., the CFDC concentration inhibiting the growth of 90% of the isolates (MIC₉₀) (0.5 μg/mL) was identical and did not change by the carbapenem resistance phenotype. The susceptibility rate of P. aeruginosa and Acinetobacter Spp. to CFDC was high (> 98%) and was similar against isolates with and without meropenem resistance. The MIC of CFDC for all Stenotrophomonas maltophilia isolates (20 isolates) was ≤1 μg/mL and the MIC₉₀ was 0.12 μg/mL. Considerable differences were noted in the susceptibility to CFDC between all tested Enterobacterales isolates and meropenem-non-susceptible Enterobacterales isolates. The MIC₉₀ of CFDC was 1 μg/mL for all tested Enterobacterales isolates and 8 μg/mL for meropenem-non-susceptible Enterobacterales isolates.

CONCLUSIONS

CFDC demonstrated potent in vitro activity against a recent collection of clinical isolates, including meropenem-non-susceptible isolates, obtained from medical centres in mainland China.

In vivo efficacy & resistance prevention of cefiderocol in combination with ceftazidime/avibactam, ampicillin/sulbactam or meropenem using human-simulated regimens versus Acinetobacter baumannii

OBJECTIVE

Evaluate the in vivo efficacy and resistance prevention of cefiderocol in combination with ceftazidime/avibactam, ampicillin/sulbactam and meropenem using human-simulated regimens (HSR) in the murine infection model.

METHODS

In total, 15 clinical A. baumannii were assessed: cefiderocol MICs, 2 mg/L (previously developed resistance on therapy), n = 3; 8 mg/L, n = 2; ≥32 mg/L, n = 10 (including VEB and PER-harbouring isolates). Mice received inactive control, cefiderocol, cefiderocol + ceftazidime/avibactam (C-CZA), cefiderocol + ampicillin/sulbactam (C-SAM) or cefiderocol + meropenem (C-MEM) HSRs. The mean change in log10 cfu/thigh compared with starting inoculum was assessed. Resistance development on treatment was a >4-fold increase in MIC relative control animals. In vitro activities of combinations were assessed by disc stacking.

RESULTS

Against cefiderocol-non-susceptible isolates, combinations produced significant kill with C-CZA -3.75 ± 0.37 reduction in log10 cfu/thigh, C-SAM produced -3.55 ± 0.50 and C-MEM produced -2.18 ± 1.75 relative to baseline. Elevated MICs in cefiderocol treated animals occurred in three out of three isolates with MICs of 2 mg/L. Of these isolates, one developed elevated MICs with C-MEM compared with none treated with C-CZA or C-SAM. Disc stacking with C-CZA or C-SAM returned all isolates to at least the CLSI intermediate breakpoint, which may correlate with in vivo efficacy.

CONCLUSIONS

Against cefiderocol-non-susceptible isolates, cefiderocol + ceftazidime/avibactam or ampicillin/sulbactam HSR produced in vivo kill against all 12 cefiderocol-non-susceptible isolates. Cefiderocol with ceftazidime/avibactam or ampicillin/sulbactam prevented the development of resistance during treatment against cefiderocol-high-end-susceptible isolates with a propensity for resistance on therapy. These data support the clinical evaluation of cefiderocol with ceftazidime/avibactam or ampicillin/sulbactam against A. baumannii, including multi-drug-resistant isolates.

1721. In Vitro Activity of Cefiderocol against IMP-Producing Enterobacterales Isolated in Japan

Background

Beta-lactam resistance is a major worldwide concern. Metallo-β-lactamases (MBLs) are a group of enzymes that can inactivate most commonly used β-lactam antibiotics including carbapenems and are not affected by new β-lactamase inhibitors. Therefore, treating infections caused by MBL producing strains is difficult. Imipenemase (IMP) type MBL is a rare family of acquired carbapenemases detected from Enterobacterales globally, however, it has been detected and become a major therapeutic concern in clinical settings mainly in East Asia including Japan [1]. Cefiderocol (CFDC) is a novel injectable siderophore cephalosporin antibiotic with potent activity against a wide variety of carbapenem resistant strains including both serine- and metallo-type carbapenemase-producers. We evaluated in vitro activity of CFDC and comparator agents against IMP-producing Enterobacterales isolated in Japan.

Methods

A total of 150 IMP-producing strains consisting of 48 Escherichia coli, 34 Klebsiella pneumoniae, 29 Klebsiella oxytoca, 21 Enterobacter cloacae, 7 Citrobacter freundii, 7 Serratia marcescens, 2 Providencia rettgeri, 1 Klebsiella aerogenes, and 1 Morganella morganii were tested. The minimum inhibitory concentrations (MICs) were determined for CFDC, ceftazidime-avibactam (CZA), ceftolozane-tazobactam (C/T), imipenem-relebactam (I-R), meropenem (MEM), and amikacin (AMK) by broth microdilution according to CLSI guidelines. CFDC was tested in iron-depleted cation-adjusted Mueller-Hinton broth.

Results

MIC50 and MIC90 of CFDC were 0.25 and 1 µg/mL, respectively. MICs of CFDC for all tested strains ranged from ≤ 0.03 to 4 µg/mL, which showed all strains were susceptible to CFDC based on the CLSI breakpoint (≤ 4 µg/mL). On the other hand, MIC90s of CZA, C/T, I-R, MEM, and AMK were &gt; 32/4, &gt; 32/4, 8/4, &gt; 32, and 4 µg/mL, respectively. The susceptibilities were 98.0% for AMK, 66.0% for I-R, and &lt; 10% for CZA, C/T and MEM.

Conclusion

CFDC had potent in vitro activity against IMP-producing Enterobacterales collected from Japan, indicating CFDC has high potential for treating infections caused by these difficult-to-treat strains.

Reference: 1. Logan, LK. et al., J Infect Dis. 2017 Feb 15;215(suppl 1):S28-S36.

Disclosures

Hidenori Yamashiro, Shionogi & Co., Ltd.: Employee Ryuichiro Nakai, n/a, Shionogi TechnoAdvance Research CO., LTD.: Employee Miki Takemura, n/a, Shionogi: Employee Yoshinori Yamano, PhD, Shionogi: Employee.

609. In vivo efficacy of human simulated exposures of cefiderocol (FDC) in combination with ceftazidime/avibactam (CZA) or meropenem (MEM) using in a 72 hour murine thigh infection model

Background

Acinetobacter baumannii continues to challenge clinicians as multi-drug resistance limits therapeutic options. CFDC possesses potent in vitro and in vivo activity however combination therapy has been recommended for A. baumannii due to its propensity for multiple resistance mechanisms. The present study utilized clinically relevant exposures of CFDC (2 g IV q8h 3 h infusion) in combination with CZA (2.5 g IV q8h 2 h infusion) or MEM (2 g IV q8h 3h infusion) to evaluate the bactericidal activity and resistance prevention.

Methods

15 clinical A. baumannii with the following FDC MICs were assessed: 2 mg/L, n = 3; 8 mg/L, n = 2; ≥ 32 mg/L, n = 10). CZA MICs ranged from 16 - >64 mg/L while MEM MICs ranged from 4 - >64 mg/L. Groups of 6 mice received sham control, CFDC HSR, CFDC + CZA HSR, or CFDC + MEM HSR for 72 h. 1 thigh per mouse was harvested to elucidated bacterial burden at 0 h (baseline) and at 72 h (or when the animal succumbed to infection). Efficacy of the combinations was assessed as change in log₁₀ CFU/thigh relative to CFDC HSR. Development of resistance was defined as > 4 fold increase in MIC relative to that from control animals.

Results

Untreated controls resulted in robust growth (3.48±0.67). Against isolates with CFDC MICs of 2 mg/L, 2/3 reached 1-log₁₀ kill with CFDC HSR relative to baseline compared with 1/2 and 0/10 isolates with FDC MICs of 8 mg/L and ≥ 32 mg/L, respectively. Against all 15 isolates, CFDC + CZA HSR produced significant kill with a mean -4.77±1.93 reduction in log₁₀ CFU/thigh relative to CFDC treated mice (15/15 ≥1-log₁₀ kill relative to baseline). Similarly, CFDC + MEM HSR produced a mean reduction of -4.13±2.50 relative to CFDC treated mice (12/15 ≥1-log₁₀ kill relative to baseline). Elevated MICs in CFDC treated animals occurred in 3/3 isolates with baseline MICs of 2 mg/L. Of these isolates, 1 developed elevated MICs with CFDC + CZA HSR compared with no isolates with CFDC + MEM HSR. Figure 1.

Change in log10 CFU/thigh relative to 0 h control after treatment with cefiderocol HSR, cefiderocol + ceftazidime/avibactam HSR, or cefiderocol + meropenem HSR in the 72 h murine thigh infection model. Cefiderocol MICs are displayed in parentheses.

Conclusion

The present study using clinical exposures of CFDC, CZA, and MEM suggest the enhanced microbiologic activity of these combinations relative to CFDC alone. Combinations also prevented the development of elevated MICs against 2/3 and 3/3 susceptible isolates with CFDC + CZA and CFDC + MEM, respectively. These data support the clinical evaluation of such combinations against A. baumannii with high CFDC MICs.

Disclosures

Christian M. Gill, PharmD, Shionogi: Grant/Research Support Miki Takemura, n/a, Shionogi: Employee Christopher M. Longshaw, PhD, Shionogi: Employee Yoshinori Yamano, PhD, Shionogi: Employee Roger Echols, MD, Shionogi: Advisor/Consultant Roger Echols, MD, Shionogi: Advisor/Consultant Roger Echols, MD, Shionogi: Advisor/Consultant David P. Nicolau, PharmD, Shionogi: Grant/Research Support.

1715. In Vitro Antibacterial Activity of Cefiderocol against Difficult-to-treat Resistant (DTR) Gram-negative Pathogens in United States from SENTRY Antimicrobial Surveillance Program in 2020/2021

Background

Difficult-to-treat resistant (DTR) isolates are defined as resistance to all first-line high-efficacy, low-toxicity antibiotics (penicillins, cephalosporins, carbapenems and quinolones), leaving physicians with limited treatment options. Cefiderocol (CFDC) is a siderophore cephalosporin with activity against a wide variety of Gram-negative bacteria, including carbapenem-resistant Enterobacterales and non-fermenters. We evaluated the in vitro activity of cefiderocol against DTR isolates collected in United States as part of SENTRY surveillance program in 2020 and 2021.

In vitro susceptibility of cefiderocol and comparator agents to DTR isolates

Methods

Susceptibility testing was performed by broth microdilution according to CLSI guidelines. All antibiotics were tested in cation-adjusted Mueller-Hinton broth (CAMHB) except for CFDC, for which iron-depleted CAMHB was used. Susceptibility rate (%) was determined according to CLSI breakpoints, and DTR pathogens were defined as being resistant to cefepime, ceftazidime ceftriaxone (only for Enterobacterales), imipenem, meropenem, ciprofloxacin and levofloxacin according to CLSI/FDA breakpoints.

Results

Among a total of 8,328 Enterobacterales, 2,241 Pseudomonas aeruginosa, and 586 Acinetobacter calcoaceticus-baumannii complex (ACB) clinical isolates from the United States, 50 Enterobacterales (0.6%), 36 P. aeruginosa (1.6%) and 114 ACB (19.5%) isolates showed a DTR phenotype, respectively. CFDC demonstrated its potent in vitro activity against these DTR isolates with MIC₉₀ of ≤4 μg/mL with a susceptibility rate of ≥92% except for DTR ACB based on FDA breakpoint (75.4%). In contrast, MIC₉₀s of β-lactam/β-lactamase inhibitor combination drugs showed lower activity (Table).

Conclusion

Cefiderocol demonstrated potent in vitro activity against DTR isolates of Enterobacterales, P. aeruginosa and ACB, indicating cefiderocol has high potential for treating infections caused by these difficult-to-treat strains.

Disclosures

Yoshinori Yamano, PhD, Shionogi: Employee Miki Takemura, n/a, Shionogi: Employee Dee Shortridge, PhD, AbbVie: Grant/Research Support|JMI Laboratory: Employee|Melinta: Grant/Research Support|Menarini: Grant/Research Support|Shionogi: Grant/Research Support Christine M. Slover, PharmD, Shionogi: Employee Christopher M. Longshaw, PhD, Shionogi: Employee Roger Echols, MD, Shionogi: Advisor/Consultant Roger Echols, MD, Shionogi: Advisor/Consultant Roger Echols, MD, Shionogi: Advisor/Consultant.

1711. In Vitro Activity of Cefiderocol Against US Achromobacter spp. and Burkholderia spp. Clinical Isolates from the SENTRY Surveillance Program 2020-2021

Background

Infections caused by Achromobacter spp. and Burkholderia spp. have limited clinical treatment options due to the intrinsic resistance of these non-fermenters to several antimicrobial agents. These pathogens are known to cause severe nosocomial infections such as bloodstream infections and pneumonia in immunocompromised patients. Cefiderocol (CFDC) is a siderophore cephalosporin antibiotic approved in the US and Europe, with potent activity against Gram-negative bacteria including carbapenem-resistant strains. We evaluated the in vitro activity of CFDC and comparator agents against Achromobacter spp. and Burkholderia spp. clinical isolates, collected from hospitalized patients in US medical centers as part of the SENTRY Antimicrobial Surveillance Program.

Methods

Susceptibility testing for CFDC and comparators were performed by broth microdilution according to the CLSI guidance. CFDC was tested in iron-depleted cation-adjusted Mueller Hinton broth. The susceptibilities of CFDC and comparators against a total of 78 strains of Achromobacter spp. and a total of 99 strains of Burkholderia spp. isolated in the US between 2020 to 2021 were analyzed. CLSI breakpoints were used where available. Isolate identification was provided by the submitting site and confirmed at JMI Laboratories using MALDI-TOF.

Results

The minimum inhibitory concentration (MIC) range, MIC50/90, and susceptible rate for CFDC and comparators for Achromobacter spp. and Burkholderia spp. are shown in the Table 1 and 2, respectively. CFDC inhibited the growth of all 78 Achromobacter spp. isolates tested at ≤4 µg/mL and showed MIC90 of 0.5 μg/mL. CFDC inhibited the growth of 96% (95/99) of Burkholderia spp. isolates tested at ≤4 µg/mL and showed MIC90 of 1 μg/mL. There were 4 strains with high CFDC MIC (≥16 µg/mL), 3 of which were Burkholderia gladioli and 1 was Burkholderia multivorans. Table 1Activity of cefiderocol and comparator antimicrobial agents tested against 78 Achromobacter spp. isolates collected from medical centers in the US during 2020 and 2021Table 2Activity of cefiderocol and comparator antimicrobial agents tested against 99 Burkholderia spp. isolates collected from medical centers in the US during 2020 and 2021

Conclusion

CFDC demonstrated potent in vitro activity against Achromobacter spp. and Burkholderia spp. collected in the US between 2020 and 2021, indicating that CFDC has high potential for treating infections caused by these pathogens.

Disclosures

Miki Takemura, n/a, Shionogi: Employee Dee Shortridge, PhD, AbbVie: Grant/Research Support|JMI Laboratory: Employee|Melinta: Grant/Research Support|Menarini: Grant/Research Support|Shionogi: Grant/Research Support Christine M. Slover, PharmD, Shionogi: Employee Christopher M. Longshaw, PhD, Shionogi: Employee Roger Echols, MD, Shionogi: Advisor/Consultant Roger Echols, MD, Shionogi: Advisor/Consultant Roger Echols, MD, Shionogi: Advisor/Consultant Yoshinori Yamano, PhD, Shionogi: Employee.

1734. Susceptibility of Cefiderocol between US Census Regions against Gram-Negative Organisms collected from the SENTRY Surveillance Program: 2020-2021

Background

Cefiderocol (CFDC) is a siderophore-conjugated cephalosporin with broad activity against Gram-negative (GN) bacteria, including multidrug-resistant organisms. GN bacteria such as Enterobacterales (ENT), Pseudomonas aeruginosa (PsA), Acinetobacter baumannii complex (ABC), and Stenotrophomonas maltophilia (StM) can be challenging to treat and are often carbapenem-resistant (CR). Regional susceptibility of CFDC and comparators were investigated against US GN isolates collected in 2020-2021 as part of the SENTRY Antimicrobial Surveillance Program.

Methods

GN pathogens were consecutively collected from 32 US hospitals between 2020 to 2021. Susceptibility testing was performed using the broth microdilution method. CFDC was tested in iron-depleted cation-adjusted Mueller-Hinton broth. FDA or CLSI breakpoints were used where available. Other agents tested included the beta-lactam/beta-lactamase inhibitor (BL/BLI) combinations ceftazidime-avibactam, ceftolozane-tazobactam, imipenem-relebactam, meropenem-vaborbactam, piperacillin-tazobactam, and ampicillin-sulbactam. CR-PsA, or CRAB was defined as meropenem resistant while CRE was defined as imipenem or meropenem resistant by CLSI breakpoints.

Results

A total of 8328 ENT, 2241 PsA, 586 ABC, and 404 StM were collected. For ENT and PsA, CFDC susceptibility between the 9 US Census regions remained above 98% susceptible by CLSI or FDA breakpoints in all regions (Table 1). Amongst the BL/BLI combinations, the majority had >90% susceptibility across regions except for piperacillin-tazobactam with 79.7% for ENT and 65.9% for PsA in the MidAtlantic by FDA breakpoints. For ABC and StM, CFDC susceptibility was > 88% across all regions. For CR pathogens, 96 CRE, 327 CR-PsA, and 199 CRAB were collected. CFDC had >87.5% susceptibility in all regions for CRE and CR-PSA. For CRAB, 4 regions were > 87.5% by FDA breakpoints and the lowest was 63.6% in 11 isolates in the Mountain region (Table 2). For CRAB, every BL/BLI had susceptibility ≤27.3% in every region. Ampicillin-sulbactam had 27.3% susceptibility in the Mountain region. Table 1

Susceptibility of Cefiderocol against Enterobacterales, Pseudomonas aeruginosa, Acinetobacter baumannii complex and Stenotrophomonas maltiphilia isolates in the cefiderocol program collected from medical centers in the USA Table 2:

Susceptibility of cefiderocol against CRE, CR Pseudomonas aeruginosa, and CR Acinetobacter baumannii complex isolates in the cefiderocol program collected from medical centers in the USA

Conclusion

US GN isolates, including CR pathogens, had high susceptibilities to CFDC across the US census regions. CFDC remains an important treatment option for GN infections in all US census regions.

Disclosures

Frank H. Kung, PhD, Shionogi Inc: Employee Sean Nguyen, n/a, Shionogi: Employee Christine M. Slover, PharmD, Shionogi: Employee Dee Shortridge, PhD, AbbVie: Grant/Research Support|JMI Laboratory: Employee|Melinta: Grant/Research Support|Menarini: Grant/Research Support|Shionogi: Grant/Research Support Jennifer M. Streit, BS, MT(ASCP), Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Shionogi: Grant/Research Support Roger Echols, MD, Shionogi: Advisor/Consultant Roger Echols, MD, Shionogi: Advisor/Consultant Roger Echols, MD, Shionogi: Advisor/Consultant Miki Takemura, n/a, Shionogi: Employee Yoshinori Yamano, PhD, Shionogi: Employee.

660. In vitro activity of cefiderocol against difficult-to-treat resistance European Gram-negative bacterial pathogens from the multi-national sentinel surveillance study, SENTRY in 2020 and 2021

Background

Difficult-to-treat resistance (DTR) organisms are defined as non-susceptible to all first-line high-efficacy, low-toxicity antibiotics (penicillins, cephalosporins, carbapenems and fluoroquinolones), leaving physicians with limited treatment options. Cefiderocol is a parenteral siderophore cephalosporin with potent activity against aerobic Gram-negative pathogens, including carbapenem-resistant strains. We evaluated the in vitro activity of cefiderocol and comparators against DTR pathogens collected in Europe by the SENTRY surveillance study in 2020 and 2021.

Methods

A total of 11434 clinical isolates of Gram-negative bacilli were systematically collected from 16 EU countries, Israel and Turkey in 2020 and 2021. Minimum inhibitory concentrations (MICs) were determined by broth microdilution for a panel of twenty-two antibiotics according to CLSI guidelines. All antibiotics were tested in cation-adjusted Mueller-Hinton broth (CAMHB) except for cefiderocol, for which iron-depleted CAMHB was used. Susceptibility was determined according to CLSI breakpoints, and DTR pathogens were defined as being resistant to cefepime, ceftazidime ceftriaxone, imipenem, meropenem, ciprofloxacin and levofloxacin according to CLSI breakpoints.

Results

Among 11434 Gram-negative isolates collected in 2020 and 2021, 792 (7.0%) were resistant to all 1^st line therapy including cephalosporins, carbapenems and fluoroquinolone and could be defined as DTR. DTR was most frequently observed in Acinetobacter spp. (530/931, 56.9%), Enterobacterales (201/7739, 2.6%) and Pseudomonas aeruginosa (61/2440, 2.5. Based on CLSI breakpoints, cefiderocol was the most active antibiotic tested against DTR-Acinetobacter spp. (MIC₉₀= 2mg/L, 97.4% susceptibility). Ampicillin/sulbactam was active in less than 1% of the DTR-Acinetobacter spp isolates. None of the drugs recommended by the IDSA for the treatment of resistant Gram-negative infections were as potent as cefiderocol (Table 1).

Conclusion

Cefiderocol was the only treatment option with demonstrated in vitro activity against more than 95% of all the tested DTR Gram-negative pathogens with limited treatment options.

Disclosures

Anne Laurence Santerre Henriksen, PhD, Shionogi: Contractor|UTILITY therapeutics Ltd: Advisor/Consultant Christopher M. Longshaw, PhD, Shionogi: Employee Dee Shortridge, PhD, AbbVie: Grant/Research Support|JMI Laboratory: Employee|Melinta: Grant/Research Support|Menarini: Grant/Research Support|Shionogi: Grant/Research Support Jennifer M. Streit, BS, MT(ASCP), Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Shionogi: Grant/Research Support Miki Takemura, n/a, Shionogi: Employee Yoshinori Yamano, PhD, Shionogi: Employee.

Cefiderocol for the Treatment of Infections Due to Metallo-B-lactamase-Producing Pathogens in the CREDIBLE-CR and APEKS-NP Phase 3 Randomized Studies

In the CREDIBLE-CR and APEKS-NP studies, cefiderocol treatment was effective against gram-negative bacteria producing metallo-B-lactamases; rates of clinical cure (70.8% [17/24]), microbiological eradication (58.3% [14/24]), and day 28 all-cause mortality (12.5% [3/24]) compared favorably with comparators of best-available therapy and high-dose meropenem (40.0% [4/10], 30.0% [3/10], and 50.0% [5/10], respectively).

[Corporate Efforts to Research and Develop Therapeutic Agents for Infectious Diseases That Threaten Human]

Overcoming serious infectious diseases such as malaria, tuberculosis, and other neglected tropical diseases (NTDs) that threaten human life around the world is an important issue in global health. Most of these diseases are concentrated in developing and low-income countries, and in order to reinforce drug discovery activities, pharmaceutical companies are actively promoting industry-academia-government partnerships and utilizing funds to stimulate global health activities. In this presentation, three examples of our drug discovery activities are introduced. The first is participation in the Booster project led by Drugs for Neglected Diseases initiative (DNDi) aimed at creating therapeutic agents for leishmaniasis and Chagas disease, an effort supported by the Global Health Innovative Technology (GHIT) Fund. As domestic and overseas pharmaceutical companies participate in the project and provide their own compounds, it is possible to obtain structure-activity relationship information in a short period of time and improve compound potency. We collaborated with DNDi to create a lead compound from one hit compound, and contributed to further enhancement of its activity. The remaining two are collaborations with academia for the creation of new therapeutic agents or vaccines: a joint research project with Hokkaido University Research Center for Zoonosis Control for emerging viral diseases, and a collaboration with Nagasaki University in malaria. In each case, our researchers were based at the university, establishing close working collaborations with the university researchers. Novel solutions for serious infectious diseases are expected by the combination of the high-level basic research capabilities of academia and the drug discovery know-how and original compound libraries possessed by pharmaceutical companies.

Assessment of sustained efficacy and resistance emergence under human-simulated exposure of cefiderocol against Acinetobacter baumannii using in vitro chemostat and in vivo murine infection models

Objectives

This study evaluated the sustained kill and potential for resistance development of Acinetobacter baumannii exposed to human-simulated exposure of cefiderocol over 72 h in in vitro and in vivo infection models.

Methods

Seven A. baumannii isolates with cefiderocol MICs of 0.12-2 mg/L were tested. The sustained bactericidal activity compared with the initial inoculum and the resistance appearance over 72 h treatment were evaluated in both an in vitro chemostat and an in vivo murine thigh infection model under the human-simulated exposure of cefiderocol (2 g every 8 h as 3 h infusion).

Results

In the in vitro model, regrowth was observed against all seven tested isolates and resistance emergence (>2 dilution MIC increase) was observed in five test isolates. Conversely, sustained killing over 72 h and no resistance emergence were observed in six of seven tested isolates in vivo. The mechanism of one resistant isolate that appeared only in the in vitro chemostat studies was a mutation in the tonB-exbB-exbD region, which contributes to the energy transduction on the iron transporters. The resistance acquisition mechanisms of other isolates have not been identified.

Conclusions

The discrepancy in the sustained efficacy and resistance emergence between in vitro and in vivo models was observed for A. baumannii. Although the resistance mechanisms in vitro have not been fully identified, sustained efficacy without resistance emergence was observed in vivo for six of seven isolates. These studies reveal the in vivo bactericidal activity and the low potential for development of resistance among A. baumannii evaluated under human-simulated exposures.

Cefiderocol: EUCAST criteria for disc diffusion and broth microdilution for antimicrobial susceptibility testing

OBJECTIVES

The reproducibility of cefiderocol MIC determination using broth microdilution (BMD) in iron-depleted CAMHB (ID-CAMHB) was investigated, and the EUCAST disc diffusion (DD) method for cefiderocol susceptibility testing was developed and validated against reference BMD.

METHODS

Cefiderocol values were determined for wild-type (WT) and non-WT isolates using BMD plates with ID-CAMHB (Thermo Scientific, Oakwood, USA) per EUCAST guidelines. DD was performed using standard EUCAST methodology on unsupplemented Mueller-Hinton agar with cefiderocol 30 μg discs. Control agents were included in all tests. MICs were correlated with zone diameters (ZD), and ZD breakpoints (BP) best corresponding to the MIC BPs were determined. Areas of technical uncertainty (ATU) were included where appropriate. External laboratory validation of cefiderocol DD was performed per the EUCAST SOP 9.2.

RESULTS

MIC and ZD distributions for cefiderocol against WT isolates were established. Cefiderocol ZD BPs were set at susceptible ≥22 mm, resistant <22 mm for Enterobacterales and Pseudomonas aeruginosa and ATUs were decided. For Acinetobacter baumannii and Stenotrophomonas maltophilia, ZD cut-off values of ≥17 mm and ≥20 mm corresponded to MIC values of ≤2 and ≤0.5 mg/L, respectively. Cefiderocol ZDs for Escherichia coli ATCC 25922 (target 27 mm) and P. aeruginosa ATCC 27853 (target 26 mm) were within ±3 mm of the target values. For DD, there was no problematic variation between discs, media or laboratories.

CONCLUSIONS

DD is a robust and easy-to-perform method for cefiderocol susceptibility testing. For isolates with results in the ATU, an MIC test should be performed to confirm the results.

Mechanisms of Reduced Susceptibility to Cefiderocol Among Isolates from the CREDIBLE-CR and APEKS-NP Clinical Trials

The objective of this study was to characterize isolates with reduced susceptibility to cefiderocol in patients receiving cefiderocol for nosocomial pneumonia or carbapenem-resistant infections in the Phase 3 APEKS-NP and CREDIBLE-CR studies. Susceptibility testing of isolates was conducted at a central laboratory, and post-treatment changes were evaluated according to available breakpoints for cefiderocol. Whole-genome sequencing and multilocus sequence typing were performed for isolates to confirm their origin and identify mutations. Five (APEKS-NP) and nine (CREDIBLE-CR) isolates demonstrated a ≥ 4-fold minimum inhibitory concentration (MIC) increase compared with genetically related baseline isolates; most remained susceptible to cefiderocol despite the ≥4-fold MIC increase. Mutations in β-lactamases or penicillin-binding protein (PBP) were identified in 4/14 isolates: one Enterobacter cloacae (amino acid [AA] substitution [A313P] in ACT-17); two Acinetobacter baumannii (one PBP3 AA substitution [H370Y], one with OXA-23 substitutions [N85I and P225S]); and one Pseudomonas aeruginosa (PDC-30 [4AA deletion "TPMA" position 316-319]). Cloning experiments using isogenic Escherichia coli strains containing wild-type and those mutant cephalosporinase enzymes show that the mutant enzymes may contribute to decreased susceptibility to cefiderocol. Pharmacokinetic data were available for nine patients, for whom cefiderocol exposures exceeded 100% fT > 4 × MIC. No clear pattern between mutations and development or extent of MIC increases was observed. No mutations were identified in genes related to iron transport, including fiu, cirA, piuA/C, and pirA, among recovered Gram-negative isolates. Clinicaltrials.gov: APEKS-NP: NCT03032380; CREDIBLE-CR: NCT02714595.

Characterisation of cefiderocol-non-susceptible Acinetobacter baumannii isolates from Taiwan

OBJECTIVES

Cefiderocol (CFDC), a siderophore cephalosporin, is active against Gram-negative bacteria including carbapenem-resistant Acinetobacter baumannii (CRAB). In this study, 100 CRAB isolates from patients with bacteraemia in Taiwan were characterised, among which 21 CFDC-non-susceptible isolates were identified with a minimum inhibitory concentration (MIC) of ≥8 mg/L.

METHODS

The effect of avibactam on CFDC activity was evaluated using broth microdilution methods according to Clinical and Laboratory Standards Institute (CLSI) guidelines. Whole-genome sequencing (WGS) was performed on all CFDC-non-susceptible isolates (MIC ≥ 8 mg/L) for multilocus sequence typing (MLST) analysis, possession of β-lactamase genes and identification of possible variations in the PiuA iron transporter.

RESULTS

Addition of avibactam, a diazabicyclooctane inhibitor for serine-type β-lactamases, resulted in a ≥8-fold decrease in the CFDC MIC for 15 of 21 CFDC-non-susceptible isolates compared with only 1 of 79 CFDC-susceptible isolates (MIC ≤ 4 mg/L). WGS analysis confirmed that all CFDC-non-susceptible isolates harboured multiple β-lactamases including ADC-30 homologues, OXA-23 and OXA-66. One isolate with a high MIC (>32 mg/L) had a PER-type extended-spectrum β-lactamase (ESBL) gene. Twenty other isolates belonged to ST455, ST473 and ST787. Among these, thirteen ST455 isolates were deficient in PiuA, a siderophore uptake receptor that may be required for optimal penetration of CFDC.

CONCLUSION

MICs of CFDC-non-susceptible CRAB isolates from Taiwan could be significantly decreased to susceptible levels by the addition of avibactam, suggesting the involvement of β-lactamases in resistance. Among the 21 CFDC-non-susceptible isolates, 1 isolate had a PER-type ESBL gene and 13 isolates lacked a PiuA iron siderophore transporter.

In vitro activity of cefiderocol against Gram-negative bacterial pathogens in Germany

OBJECTIVES

Widespread antimicrobial resistance in Gram-negative bacteria (GNB), particularly carbapenem resistance, represents a major clinical challenge. Cefiderocol is a novel siderophore cephalosporin active against all carbapenemase classes.

METHODS

We evaluated the in vitro activity of cefiderocol and other antibacterial agents (ceftazidime/avibactam, ceftolozane/tazobactam, colistin and meropenem) against GNB isolates collected in Germany (2013-2018) as part of two multinational studies. Antimicrobial susceptibility testing was performed by broth microdilution. Minimum inhibitory concentrations were interpreted according to EUCAST breakpoints.

RESULTS

Cefiderocol had high activity against GNB isolates (N = 2298), encompassing both Enterobacterales (n = 1562) and non-fermenter species (n = 736), and maintained high activity against carbapenem-resistant strains (n = 211). The activity of cefiderocol against Enterobacterales was equivalent to that of ceftazidime/avibactam and colistin, while ceftolozane/tazobactam was somewhat less active. Against non-fermenter species, cefiderocol displayed equivalent activity to colistin; both of these agents were more active than ceftazidime/avibactam and ceftolozane/tazobactam. Colistin had similar activity to cefiderocol against the majority of species. These patterns of activity were echoed in carbapenem-resistant isolates. The high activity of cefiderocol was independent of infection site, whereas other antibacterial agents demonstrated slightly lower activity against isolates causing pneumonia compared with those from other key infection sites.

CONCLUSION

Cefiderocol exhibited consistently high in vitro activity against a variety of GNB isolates collected in Germany, including resistant phenotypes, across multiple infection sites. These data suggest that cefiderocol is an effective choice of antibacterial agent in patients with GNB infection, regardless of species and resistance phenotype to other agents.

In vitro activity of the novel siderophore cephalosporin, cefiderocol, in Gram-negative pathogens in Europe by site of infection

OBJECTIVES

We assessed the activity of the novel siderophore cephalosporin, cefiderocol and selected other antibacterial agents against Gram-negative bacterial isolates in Europe.

METHODS

Isolates were obtained between 2013 and 2018 from European countries participating in the SIDERO-WT and SIDERO-Proteeae multinational surveillance studies. Isolates were categorised by infection site, focusing on bloodstream infections, hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP), complicated intra-abdominal infections and complicated urinary tract infections. Cefiderocol activity was compared with ceftazidime-avibactam, ceftolozane-tazobactam, colistin and meropenem using standard susceptibility testing methods. European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints were used to interpret susceptibility data.

RESULTS

Isolates (n = 20 911) were collected from 145 sites in 24 countries in Europe, the highest proportion (34%) being from patients with HABP/VABP. Enterobacterales (66.6% of isolates) were more frequent than glucose non-fermenting species (33.4%) overall, with some differences between infection sites. Across all infection sites, the MIC50/MIC90 for cefiderocol was ≤0.5/≤2 mg/L for Enterobacter spp., ≤0.25/<2 mg/L for Klebsiella spp., 0.12/2 mg/L for Acinetobacter spp., ≤0.25/1 mg/L for Pseudomonas aeruginosa and ≤0.12/≤0.5 mg/L for Stenotrophomonas maltophilia. Across all infection sites, cefiderocol MICs were ≤2 mg/L for ≥96% of Enterobacter spp., ≥95% of Klebsiella spp., ≥90% of Acinetobacter spp. and ≥99% of Pseudomonas aeruginosa and Stenotrophomonas maltophilia isolates. Cefiderocol maintained high activity in carbapenem-resistant isolates, and the difference in activity between carbapenem-resistant (percentage susceptibility at EUCAST breakpoint: E. coli 77.8%, Klebsiella spp. 69.2%, Pseudomonas aeruginosa 97.5%, Acinetobacter spp. 90.7%, Stenotrophomonas maltophilia 99.6%) and carbapenem-susceptible (percentage susceptibility at EUCAST breakpoint: E. coli 99.4%, Klebsiella spp. 98.0%, Pseudomonas aeruginosa 99.7%, Acinetobacter spp. 94.9%) isolates was lower for cefiderocol than other agents.

CONCLUSIONS

Cefiderocol had excellent activity against all Gram-negative species, independent of key infection site and carbapenem MIC. Cefiderocol is a useful addition to the therapeutic options available for these difficult-to-treat infections.

In Vitro Susceptibility of Gram-Negative Pathogens to Cefiderocol in Five Consecutive Annual Multinational SIDERO-WT Surveillance Studies, 2014 to 2019

We report in vitro susceptibility data from five consecutive annual SIDERO-WT surveillance studies (2014 to 2019) for cefiderocol and comparators tested against Gram-negative clinical isolates from North America and Europe. CLSI broth microdilution was used to determine MICs for Enterobacterales (n = 31,896), Pseudomonas aeruginosa (n = 7,700), Acinetobacter baumannii complex (n = 5,225), Stenotrophomonas maltophilia (n = 2,030), and Burkholderia cepacia complex (n = 425). MICs were interpreted by CLSI-approved clinical breakpoints (February 2021). Cefiderocol inhibited 99.8, 96.7, 91.6, and 97.7% of all Enterobacterales, meropenem-nonsusceptible, ceftazidime-avibactam-nonsusceptible, and ceftolozane-tazobactam-nonsusceptible isolates, respectively, at ≤4 μg/mL (susceptible breakpoint). Cefiderocol inhibited 99.9, 99.8, 100, and 99.8% of all P. aeruginosa, meropenem-nonsusceptible, ceftazidime-avibactam-nonsusceptible, and ceftolozane-tazobactam-nonsusceptible isolates, respectively, at ≤4 μg/mL (susceptible breakpoint). Cefiderocol inhibited 96.0% of all A. baumannii complex isolates and 94.2% of meropenem-nonsusceptible isolates at ≤4 μg/mL (susceptible breakpoint) and 98.6% of S. maltophilia isolates at ≤1 μg/mL (susceptible breakpoint). B. cepacia complex isolates were tested with a MIC50 of ≤0.03 μg/mL and MIC90 of 0.5 μg/mL. Annual cefiderocol percent susceptible rates for Enterobacterales (North America range, 99.6 to 100%/year; Europe range, 99.3 to 99.9%/year) and P. aeruginosa (North America range, 99.8 to 100%; Europe range, 99.9 to 100%) were unchanged from 2014 to 2019. Annual percent susceptible rates for A. baumannii complex demonstrated sporadic, nondirectional differences (North America range, 97.5 to 100%; Europe range, 90.4 to 97.5%); the wider range for Europe (∼7%) was due to isolates from Russia. Annual percent susceptible rates for S. maltophilia showed minor, nondirectional differences (North America range, 96.4 to 100%; Europe range, 95.6 to 100%). We conclude that clinical isolates of Enterobacterales (99.8% susceptible), P. aeruginosa (99.9%), A. baumannii (96.0%), and S. maltophilia (98.6%) collected in North America and Europe from 2014 to 2019 were highly susceptible to cefiderocol.

1256. Clinical Response by Minimum Inhibitory Concentrations in Carbapenem-Resistant Pseudomonas aeruginosa Infections under Cefiderocol Compassionate Use Program

Background

Cefiderocol (CFDC) has been developed for the treatment of serious infections caused by drug-resistant aerobic Gram-negative pathogens, including carbapenem-resistant (CR) Pseudomonas aeruginosa (CRPA). The current CFDC susceptibility breakpoints for P. aeruginosa differ between US Food and Drug Administration (FDA) and Clinical and Laboratory Standards Institute (CLSI) (Table). Data characterizing the impact of CFDC minimum inhibitory concentrations (MICs) on the clinical responses of patients treated with CFDC for CRPA are sparse.

Methods

We reviewed patients treated with compassionate-use CFDC (2 g, q8h or renally adjusted dosages) for infections caused by CRPA with no alternative treatment options. CFDC minimum inhibitory concentrations (MICs) were evaluated according to CLSI guidelines in iron-depleted cation-adjusted Müller–Hinton broth for available CRPA isolates. We then assessed physician-reported clinical responses to CFDC therapy and stratified results by CFDC MIC.

Results

There were 71 patients overall with CRPA treated with CFDC. Treatment duration ranged from 1 to 132 days. For the subset of 33 patients for whom CFDC MIC values were available, the most common infection sites were the respiratory tract (n=15), blood (n=12), and urinary tract (n=4). Patients could have had an infection at ≥1 sites and in other locations. CFDC MIC range was ≤0.03– >64 µg/mL. The modal MIC value was 2 µg/mL (n=13; Table). CRPA isolates were susceptible to CFDC in 13/33 patients (39.4%) based on the FDA breakpoint (MIC ≤1 µg/mL) and in 31/33 patients (93.9%) based on the CLSI breakpoint (MIC ≤4 µg/mL). Clinical response was reported for 15/18 patients (83.3%) who had infections with CFDC MICs of 2–4 µg/mL, organisms that are considered susceptible by CLSI but not by FDA breakpoints (Table). Clinical response was reported in 6/13 patients (46.1%) with infections with CFDC MIC ≤1 µg/mL and in 1 of 2 patients (50.0%) with CFDC MIC ≥8 µg/mL (Table). 21 (63.6%) patients survived to Day 28 and there were no trends in mortality by CFDC MIC.

Conclusion

Clinical response rate was high for CRPA infections with CFDC MICs of 2–4 µg/mL, supporting the higher CLSI susceptibility breakpoint.

Disclosures

Michael J. Satlin, MD, MS, Achaogen (Consultant)Allergan (Research Grant or Support)BioFire Diagnostics (Research Grant or Support)Merck (Research Grant or Support)Shionogi (Consultant) David Fam, PharmD, Shionogi (Employee) Roger Echols, MD, Shionogi (Consultant) Christopher Longshaw, PhD, Shionogi (Employee) Miki Takemura, MS, SHIONOGI & CO., LTD. (Employee) Yoshinori Yamano, PhD, Shionogi (Employee)

1065. Efficacy of Cefiderocol in Experimental Stenotrophomonas maltophilia Pneumonia in Persistently Neutropenic Rabbits

Background

Stenotrophomonas maltophilia causes lethal pneumonia, bacteremia, and sepsis in immunocompromised patients. As a standard of care, trimethoprim-sulfamethoxazole (T/S) is considered to be the first-line therapy for Stenotrophomonas pneumonia. Cefiderocol (CFDC) is a new parenteral siderophore cephalosporin that is transported through the outer cell membrane as a siderophore mimic that then inhibits Gram-negative cell wall biosynthesis. CFDC has potent activity in vitro against S. maltophilia; however, little is known about its in vivo activity against Stenotrophomonas pneumonia in immunocompromised hosts. We therefore studied CFDC in comparison to TS in the persistently neutropenic rabbit model of Stenotrophomonas pneumonia. This rabbit model, in contrast to conventional murine models, reflects the human pattern of infection more accurately over time.

Methods

We initially studied the plasma pharmacokinetics of CFDC in non-infected and infected animals. Stenotrophomonas pneumonia was established by direct endotracheal inoculation of S. maltophilia 1×10¹⁰ CFUs for tracheobronchial colonization that evolved into bronchopneumonia. Experimental groups consisted of CFDC, T/S, and untreated controls (UC). Rabbits received CFDC at 120 mg/kg IV Q8h and T/S at 5 mg/kg IV Q12h. Profound persistent neutropenia was maintained with cytosine arabinoside. Treatment was continued for 10 days.

Results

There were no significant differences between non-infected and infected rabbits in CFDC pharmacokinetics. Rabbits treated with CFDC and T/S demonstrated significant decreases of residual pulmonary and BAL bacterial burden vs UC (p≤0.001). CFDC achieved full clearance of S. maltophilia from lung tissue and BAL. This antibacterial activity coincided with significant reduction of lung weights (marker of organism-mediated pulmonary injury) in the CFDC group vs T/S and UC (p< 0.01). Survival was prolonged in the CFDC treatment group with 87% survival in comparison to that of T/S (25%) and UC (0%) (p< 0.01).

Table 1. Efficacy of Cefiderocol in Experimental Stenotrophomonas maltophilia Pneumonia in Persistency Neutropenic Rabbits

Conclusion

Cefiderocol is highly active in treatment of experimental S. maltophilia pneumonia in persistently neutropenic rabbits, thus laying the foundation for future clinical investigations against this lethal infection.

Disclosures

Naoki Ishibashi, MD, Shionogi, Inc. (Employee) Benjamin Georgiades, n/a, Shionogi, Inc. (Consultant) Roger Echols, MD, Shionogi (Consultant) Robert A. Bonomo, MD, entasis (Research Grant or Support)Merck (Grant/Research Support)NIH (Grant/Research Support)VA Merit Award (Grant/Research Support)VenatoRx (Grant/Research Support) Yoshinori Yamano, PhD, Shionogi (Employee) Thomas J. Walsh, MD, PhD (hon), Scynexis (Consultant, Grant/Research Support)Shionogi (Consultant, Grant/Research Support)

1287. Double Disk Diffusion Study to Evaluate the Synergistic Effect Between Cefiderocol and Ceftazidime-Avibactam Against Cefiderocol-Non-susceptible Acinetobacter baumannii

Background

Cefiderocol (CFDC), a siderophore cephalosporin, has broad coverage of Gram-negative bacteria and has been approved for clinical use in USA and Europe. The SIDERO-WT surveillance studies showed that CFDC shows &gt;95% susceptibility against Acinetobacter baumannii. Against many of CFDC non-susceptible isolates, most of which had blaPER gene, the combination use of avibactam significantly decreased the MIC by broth microdilution (BMD). In this study, we evaluated the appropriate methodology to evaluate the synergistic effect by disk diffusion studies.

Methods

The susceptibility testing was conducted as recommended by the CLSI using CFDC non-susceptible isolates (MIC of &gt;4 µg/mL based on CLSI breakpoint). The MIC by BMD was determined using iron-depleted cation-adjusted Mueller-Hinton broth, in the presence or absence of 4 µg/mL of avibactam. The disk diffusion was evaluated using Mueller-Hinton agar, and the synergy was evaluated by using disk stacking methods. For disk stacking methods, CFDC disk was placed on agar on which bacterial suspension of 0.5 McFarland units was spread, then the ceftazidime-avibactam (CZA) disks was stacked on the top, followed by adding a drop (30 µL) of saline on the stacked disks. As an alternative method, CZA was immersed in saline for 1 second instead of adding a drop of saline, followed by the stacking on the top. The disk zone size was determined after 24-hour incubation at 37°C.

Results

Against blaPER-positive A. baumannii which showed &gt;64 µg/mL MIC of CFDC and CZA, CFDC MIC decreased to 0.25 µg/mL in the presence of avibactam. The disk diffusion methods also showed isolates resistant to CFDC and CZA and showed susceptiblilty disk zone to CFDC by stacking both disks. On the other hand, against blaNDM-positive A. baumannii which showed 64 µg/mL MIC of CFDC and CZA, the disk diffusion methods showed resistance even when stacking both disks. Against multiple isolates, the MIC of CFDC without or with avibactam was correlated well with the disk zone produced by CFDC disk alone or stacked with CZA disks, respectively (Figure).

Conclusion

The synergistic effect between CFDC and avibactam by BMD methods could be detected by disk stacking methodology using CFDC and CZA disks.

Disclosures

Yoshinori Yamano, PhD, Shionogi (Employee) Miki Takemura, MS, SHIONOGI & CO., LTD. (Employee) Roger Echols, MD, Shionogi (Consultant) Christopher Longshaw, PhD, Shionogi (Employee)

789. Susceptibility of Phenotypic Subsets of Pseudomonas aeruginosa Isolates to Cefiderocol and Comparator Agents from SIDERO-WT 2014-2019

Background

Multidrug-resistant (MDR) phenotypes are frequently observed among P. aeruginosa (PsA) isolated from hospitalized patients. This study describes the in vitro activities of cefiderocol (CFDC) and comparator agents against various non-susceptible (NS) phenotypic subsets of MDR PsA isolates from the SIDERO-WT multi-national surveillance program.

Methods

Clinical PsA isolates were collected from North America (NA) and Europe in 2014-2019 and tested for susceptibility at a central laboratory. MICs (μg/ml) were determined for CFDC, ceftazidime-avibactam (CZA), ceftolozane-tazobactam (C/T), colistin, cefepime, meropenem (MEM), and ciprofloxacin by broth microdilution according to CLSI guidelines. Aztreonam-avibactam (avibactam fixed concentration of 4 µg/ml) and imipenem/relebactam (I/R) were only tested during SIDERO-WT Year 5 (i.e. 2019). Susceptibility was interpreted according to current FDA and 2021 CLSI breakpoints.

Results

The different phenotypic subsets and susceptibility of tested compounds are shown in the table. Among 7700 PsA isolates, 47.7% and 23% were from respiratory and gastrointestinal sources of infection. CFDC inhibited 97.5% and 99.9% of all PsA at its FDA-S and CLSI-S MIC breakpoint of ≤1 and ≤4, respectively. CFDC had the lowest MIC90 of all tested agents and &gt;99% S at an MIC ≤4 for all phenotypic subsets. At a MIC ≤1, CFDC displayed high susceptibility rates against all subsets including ≥88% S against CZA-NS, C/T-NS, I/R-NS, and MEM+I/R-NS isolates. Against MDR subsets, comparator agents consistently demonstrated lower activity than CFDC; 88% of MEM+C/T-NS and MEM+CZA-NS isolates had a CFDC MIC≤1 while 15.6% and 20.3% were S to I/R, respectively. 86% of MEM+CZA+C/T-NS and 80.4% CZA+C/T+I/R-NS isolates were S to CFDC. CFDC inhibited 98.1% and 99.4% of PsA isolates from NA (n = 3548) at a MIC of ≤1 and ≤4, respectively. In NA isolates that were MEM+C/T-NS; 85.7% of PsA isolates had a MIC ≤1 to CFDC and 33.3% and 28.6% were S to CZA and I/R, respectively.

Conclusion

CFDC demonstrated potent in vitro activity against a variety of phenotypic subsets of MDR P. aeruginosa isolates as compared to agents that are commonly used to treat MDR PsA infections including strains NS to other agents. These data support the use of CFDC as an important treatment option for MDR PsA.

Disclosures

Sean Nguyen, PharmD, Shionogi Inc (Employee) David Fam, PharmD, Shionogi (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Meredith Hackel, PhD MPH, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Roger Echols, MD, Shionogi (Consultant) Yoshinori Yamano, PhD, Shionogi (Employee)

1066. In Vitro and in Vivo Antimicrobial Activity of Cefiderocol and Comparators against Achromobacter spp

Background

Achromobacter spp. is intrinsically resistant to multiple antibiotics, and the treatment options are limited. Cefiderocol (CFDC), a siderophore cephalosporin approved in US and EU, is active against a wide variety of aerobic Gram-negative bacteria, including carbapenem-resistant strains. In this study, in vitro and in vivo antibacterial activity of CFDC against Achromobacter spp. was evaluated.

Methods

A total of 334 global isolates collected by IHMA from 39 countries in 2015-2019 were used. Minimum inhibitory concentrations (MICs) of CFDC and comparators were determined by broth microdilution method using iron-depleted CAMHB or CAMHB, respectively, as recommended by CLSI guidelines. In vivo efficacy of CFDC was compared with meropenem (MEM), piperacillin-tazobactam (PIP/TAZ), ceftazidime (CAZ), and ciprofloxacin (CIP) in a neutropenic murine lung infection model (n=5), and compared with MEM in a immunocompetent rat lung infection model (n=3-7) caused by 2 A. xylosoxydans. In the murine model, treatment was given 2, 5, and 8 hours post-infection, and the numbers of viable cfu in lungs were determined 24 hours post-infection. In the rat model, the humanized PK in plasma resulting from CFDC 2 g every 8 h (3-h infusion) or meropenem 1 g every 8 h (0.5-h infusion) were recreated via continuous intravenous infusion for 4 days, following which cfu in lungs were determined.

Results

CFDC showed in vitro activity with MIC_50/90 of 0.06/0.5 µg/mL against 334 Achromobacter spp. Only 7 isolates (2.1%) had MICs > 4 µg/mL. These were the lowest values among all compound tested (Table). In the murine model, CFDC caused > 1.5 log₁₀ decrease of viable cfu in lungs at 100 mg/kg dose (%fT >MIC: < 50%) from baseline control against both of strains (CFDC MIC: 0.5 and 2 µg/mL) (P< 0.05). No decrease of cfu in lungs was observed for the comparators at 100 mg/kg (MEM, PIP/TAZ, CAZ, and CIP MICs were >16, >64, >32, and >8 µg/mL, respectively). In the rat model, humanized CFDC dosing reduced the viable cfu by >1 log₁₀ CFU/lung compared with baseline controls (P< 0.05). MEM showed no significant activity.

In vitro activity of CFDC and comparator agents against Achromobacter spp.

334 Achromobacter spp. isolates collected from 2015 and 2019. The majority of isolates tested were A. xylosoxidans (312/334; 93.4%), followed by A. insolitus (11/334; 3.3%), Achromobacter sp. (8/334; 2.4%), A. denitrificans (2/334; 0.6%), and A. piechaudii (1/334; 0.3%).

Conclusion

CFDC showed potent in vivo efficacy reflecting in vitro activity against A. xylosoxidans. The results suggested that CFDC has the potential to be an effective therapeutic option for Achromobacter spp. infections.

Disclosures

Ryuichiro Nakai, MSc, Shionogi TechnoAdvance Research & Co., Ltd. (Employee) Ayaka makino, BSc, Shionogi TechnoAdvance Research & Co., Ltd. (Employee) Toriko Yoshitomi, -, Shionogi TechnoAdvance Research & Co., Ltd. (Employee) Rio Nakamura, BSc, Shionogi TechnoAdvance Research & Co., Ltd. (Employee) Meredith Hackel, PhD MPH, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Miki Takemura, MS, SHIONOGI & CO., LTD. (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Yoshinori Yamano, PhD, Shionogi (Employee)

1058. In Vitro and In Vivo Antibacterial Activity of Cefiderocol against Burkholderia spp

Background

Burkholderia spp. is an opportunistic pathogen associated with respiratory infections. Cefiderocol (CFDC), a siderophore cephalosporin approved in US and EU, is active in vitro against carbapenem-resistant Gram-negative bacteria including Burkholderia spp. This study examined in vitro and in vivo activity of CFDC against Burkholderia spp.

Methods

MICs of CFDC and 13 marketed antibacterial drugs against 462 clinical isolates of Burkholderia spp. collected in 2014 - 2019 in 13 countries were determined by broth microdilution method according to CLSI guidelines. Only for CFDC, iron-depleted CAMHB was used. In a rat lung infection model, B. cepacia ATCC 25416 (CFDC MIC: ≤ 0.031 μg/mL, MEM MIC: 4 μg/mL) was used. Male CD (SD, immunocompetent, n=4-5) rats were infected by intrabronchial inoculation of the bacterial suspension including 1% nutrient agar. The humanized PK in plasma by administration of CFDC 2 g every 8 h (3-h infusion) and MEM 1 g every 8 h (0.5-h infusion) were recreated via the continuous intravenous infusion for 4 days, and the viable cfu in lungs were counted.

Results

Against 462 strains, including 185 MEM non-susceptible isolates, CFDC showed MIC₅₀/MIC₉₀ of ≤ 0.031/1 µg/mL, which was the lowest among the tested antibiotics. Among 185 MEM non-susceptible isolates, 94% of the isolates exhibited ≤ 4 µg/mL of CFDC MIC. In a rat lung infection model, CFDC and MEM showed bactericidal activity with 2.8 and 2.4 log₁₀ CFU/lung decrease compared with non-treated control, respectively. By recreating the humanized PK exposure in this model, 100% and ca.35% of fT >MIC of CFDC and MEM in plasma has been achieved, respectively. The bactericidal activities of both compounds vs B. cepacia ATCC 25416 would be reasonable because the fT >MIC achieved in this model exceeds the target fT >MIC (75% for CFDC and 26% for MEM against Acinetobacter baumannii, respectively) required to cause 1 log₁₀ reduction in murine thigh infection models^1,2).

1) M. Sabet. 2019. AAC 2) R. Nakamura. 2019. AAC

In vitro activity of CFDC and comparator agents against Burkholderia spp.

Conclusion

CFDC has potential for treating respiratory tract infections caused by Burkholderia spp. In critically ill patients, the recommended dosing regimen achieves 100% of fT >MIC of ≤ 4 ug/mL³⁾.3) N. Kawaguchi. 2021. AAC

Disclosures

Merime Oota, BSc, Shionogi TechnoAdvance Research & Co., Ltd. (Employee) Toriko Yoshitomi, -, Shionogi TechnoAdvance Research & Co., Ltd. (Employee) Rio Nakamura, BSc, Shionogi TechnoAdvance Research & Co., Ltd. (Employee) Miki Takemura, MS, SHIONOGI & CO., LTD. (Employee) Yoshinori Yamano, PhD, Shionogi (Employee) Meredith Hackel, PhD MPH, IHMA (Employee)Pfizer, Inc. (Independent Contractor) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Independent Contractor)

1106. Evaluation of Penetration of Cefiderocol into Cerebrospinal Fluid Using a Rat Meningitis Model

Background

Central nervous system (CNS) infections caused by Gram-negative bacteria (GNB) are sometimes hard to treat due to antibiotic resistance and difficulty with penetration into cerebrospinal fluid (CSF). Cefiderocol (CFDC) which was approved by the FDA and the EMA in 2019 to 2020 is a siderophore cephalosporin with potent activity against various GNB including carbapenem-resistant strains. In this study, we evaluated the penetration of CFDC into CSF using a rat meningitis model.

Methods

To induce meningitis, the anesthetized immunocompetent rats were infected by intracisternal inoculation of a bacterial suspension of 8.7×10¹ CFU of E. coli SR200138. 200 mg/kg or 50 mg/kg of CFDC was administered via tail vein bolus injection to uninfected rats (n=4/sampling point) and rats with meningitis (n=4/sampling point) 24 hours after infection. CSF was collected by cisternal puncture and blood was collected from heart. The samplings were performed 0.25, 0.5, 1, 3, and 5 hours after dosing. The concentrations of CFDC in plasma and CSF for individuals were determined by LC/MS/MS. PK parameters for the average values in plasma and CSF were calculated.

Results

CFDC concentration and the PK parameters are shown in Figure and Table, respectively. The penetration of CFDC from plasma to CSF was observed in both uninfected and meningitis groups, and the penetration rates increased in the rats withs meningitis (AUC_CSF/AUC_plasma: 0.149-0.183) compared with the uninfected rats (AUC_CSF/AUC_plasma: 0.0508-0.0588). The penetration rates of CFDC in the meningitis were comparable to those of piperacillin, cefepime, and meropenem in human (0.32, 0.103, and 0.39 in strongly inflamed meninges, respectively) [1]. In both groups, elimination of CFDC from CSF was slower compared with that from plasma as seen with other β-lactam antibiotics such as meropenem, suggesting that T_{> MIC}, an indicator that correlates with the efficacy of β-lactams, may be higher in CSF [2].

Table. PK Parameters of Cefiderocol after Intravenous Bolus Administration in Uninfected Rats and Rats with Meningitis

Figure. Concentrations of Cefiderocol after Intravenous Bolus Administration in Uninfected Rats and Rats with Meningitis

Conclusion

It was confirmed that CFDC penetrates into CSF from plasma in a rat model and the penetration rate was increased 3-fold in meningitis.

References

1. Nau, R. et al. Clin Microbiol Rev. 2010 Oct;23(4):858–883.

2. Nau, R. et al. Antimicrob Agents Chemother. 1998 Aug;42(8):2012–2016.

Disclosures

Miki Takemura, MS, SHIONOGI & CO., LTD. (Employee) Sachi Kanazawa, PhD, Shionogi & Co., Ltd. (Employee) Naoki Kohira, PhD, Shionogi & Co., Ltd. (Employee) Yuki Aoe, BS, Shionogi TechnoAdvance Research Co., Ltd. (Employee) Atsushi Morimoto, n/a, Shionogi TechnoAdvance Research Co., Ltd. (Employee) Kana Horiuchi, MPharm, Shionogi & Co., Ltd. (Employee) Yuji Inoue, MPharm, Shionogi & Co., Ltd. (Employee) Yoshinori Yamano, PhD, Shionogi (Employee)

Discrepancy in sustained efficacy and resistance emergence under human-simulated exposure of cefiderocol against Stenotrophomonas maltophilia between in vitro chemostat and in vivo murine infection models

OBJECTIVES

The present study evaluated the sustained kill and the potential for resistance development of Stenotrophomonas maltophilia exposed to a human-simulated exposure of cefiderocol over 72 h in in vitro and in vivo infection models.

METHODS

A total of seven S. maltophilia isolates with cefiderocol MICs of 0.03-0.5 mg/L were utilized. The sustained bactericidal activity compared with the initial inoculum and the appearance of resistance after the 72 h treatment were evaluated in both an in vitro chemostat model (four strains) and an in vivo murine thigh infection model (six strains) under the human-simulated exposure of cefiderocol (2 g every 8 h as a 3 h infusion).

RESULTS

In the in vitro model, regrowth was observed for three of four tested isolates and resistance emergence (>2-dilution MIC increase) was observed for all of the four test isolates. Conversely, sustained killing over 72 h and no resistance emergence were observed for all of the six tested isolates in the in vivo models. The mechanism of all resistant isolates that appeared only in the in vitro chemostat studies was a mutation in the tonB-exbB-exbD region, which contributes to the energy transduction on the iron transporters.

CONCLUSIONS

The discrepancy in the sustained efficacy and resistance emergence between in vivo and in vitro models appears to be due to the resistance acquisition mechanism caused by mutation in the tonB-exbB-exbD region developing in the enriched media utilized in vitro. These studies reveal the in vivo bactericidal activity and the low potential for development of resistance among Stenotrophomonas evaluated under human-simulated exposures.

In Vitro Activity and In Vivo Efficacy of Cefiderocol against Stenotrophomonas maltophilia

Cefiderocol is a novel siderophore cephalosporin antibiotic with broad coverage against difficult-to-treat Gram-negative bacteria, including those resistant to carbapenems. Its activity against Stenotrophomonas maltophilia was investigated in vitro against clinical isolates and in lung infection models using strains either resistant (SR202006) or susceptible (SR201934, SR200614) to trimethoprim-sulfamethoxazole. Cefiderocol demonstrated potent in vitro activity against all 217 S. maltophilia clinical isolates tested (MIC50, 0.063 μg/ml; MIC90, 0.25 μg/ml). Cefiderocol also demonstrated low MICs against the trimethoprim-sulfamethoxazole-resistant S. maltophilia strains (i.e., SR202006; MIC, 0.125 μg/ml). In a neutropenic mouse lung infection model, cefiderocol (30 mg/kg body weight and 100 mg/kg) demonstrated a significant, dose-dependent reduction in the lung viable bacteria cell count compared with untreated controls in S. maltophilia infection and was the only antibiotic tested to show a similar significant effect in a trimethoprim-sulfamethoxazole-resistant S. maltophilia infection. In immunocompetent rat lung infection models of S. maltophilia, humanized dosing of cefiderocol (2 g every 8 h) and meropenem (1 g every 8 h) revealed pharmacokinetic profiles similar to those in human subjects, and the humanized cefiderocol dosing significantly reduced the lung viable bacteria cell count compared with baseline controls, which received no intervention. Together, the results from these studies suggest that cefiderocol could provide an effective alternative treatment option for S. maltophilia infections in the lower respiratory tract, particularly strains resistant to empirical antibiotics, such as trimethoprim-sulfamethoxazole or minocycline.

164. in Vitro Antibacterial Activity of Cefiderocol Against Non-fermenter Clinical Strains Collected in North America and Europe from Multinational Surveillance Studies SIDERO-WT-2014–2018

Background

Non-fermenting Gram-negative bacilli (NFGNB), such as Pseudomonas aeruginosa, Acinetobacter baumannii-complex (ABC), Stenotrophomonas maltophilia, and Burkholderia cepacia-complex (BCC), are recognized as difficult-to-treat organisms due to acquired and intrinsic antimicrobial resistance. This study evaluated the in vitro activity of cefiderocol (CFDC), a novel parenteral siderophore cephalosporin, and comparator agents against NFGNB clinical isolates collected in 2014–2018 as part of the multinational SIDERO-WT surveillance program.

Methods

12,293 non-fermenter clinical isolates, including 5310 from North America and 6983 from Europe, were tested for antimicrobial susceptibility. Minimum inhibitory concentrations (MICs) were determined for CFDC, cefepime (FEP), ceftazidime-avibactam (CZA), ceftolozane-tazobactam (C/T), meropenem-vaborbactam (MVB), meropenem (MEM), ciprofloxacin (CIP), colistin (CST), and trimethoprim-sulfamethoxazole (SXT) by broth microdilution according to Clinical Laboratory and Standards Institute (CLSI) guidelines. MICs for aztreonam-avibactam (ATM/AVI; ATM in the presence of 4 μg/mL AVI), MVB, and SXT were determined only for SIDERO-WT 2018 strains. As per CLSI guidelines, CFDC was tested in iron-depleted media, and carbapenem-non-susceptible (CarbNS) isolates were defined as non-susceptible to MEM.

Results

CFDC demonstrated in vitro activity with MIC₉₀s of 0.25–2 µg/mL against clinical isolates of P. aeruginosa, ABC, S. maltophilia, and BCC, including CarbNS subsets. MIC₉₀s of CFDC against CarbNS P. aeruginosa (N=1416), CarbNS ABC (N=2274), S. maltophilia (N=1565), and CarbNS BCC (N=80) were 1, 2, 0.5, and 2 μg/mL, respectively, which were the lowest among the tested compounds (Table). The MIC₉₀ differences between all isolates and CarbNS subsets were ≤2-fold for P. aeruginosa and ABC, showing that CFDC is active against CarbNS subsets as well as carbapenem-susceptible isolates. However, an 8-fold MIC₉₀ difference between all isolates and CarbNS subsets was observed for BCC.

Conclusion

In 4 years of consecutive multinational surveillance studies, CFDC was the most active agent among antimicrobials tested against a wide range of NFGNB, including CarbNS strains.

Disclosures

Yuuta Ukai, MSc, Shionogi & Co., Ltd. (Employee) Rio Nakamura, BSc, Shionogi & Co., Ltd. (Employee) Merime Oota, BSc, Shionogi & Co., Ltd. (Employee) Roger Echols, MD, Shionogi Inc. (Consultant) Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor)

1269. Differences in Interpretative Breakpoints Between CLSI, FDA and EUCAST Impact Reporting of Susceptibility and Resistance to Cefiderocol

Background

Cefiderocol (CFDC) is a siderophore cephalosporin with broad coverage of aerobic Gram-negative (GN) bacteria. Provisional breakpoints (BP) were approved by CLSI in 2018, with FDA and EUCAST providing clinical BP in 2019 and 2020, respectively; however, BPs differ markedly between organizations, reflecting differences in labelling, PK/PD standards and availability of clinical study data during regulatory review. Here we compare susceptibility rates based on these different BPs.

Methods

Susceptibility rates for each bacterial species were determined using CFDC BP from each organization and the MICs of 28,629 GN clinical isolates from 3 consecutive years of SIDERO-WT surveillance studies (2014–17). The analysis used all isolates and sub-grouped isolates based on meropenem (MEM) susceptibility (CLSI BP) or carbapenemase production.

Results

Within the overall Enterobacterales group, ≥98.5% isolates were interpreted as susceptible to CFDC regardless of BP used. However, the proportion of susceptible differed significantly (82.5–98.6%) when applied to MEM-non-susceptible (NS) isolates. Similarly, against most carbapenemase producers, susceptibility ranged from 80 to 100%, however for NDM producers, only 51% of isolates were defined as susceptible by FDA or EUCAST BP vs 84% using the CLSI BP. Against Pseudomonas aeruginosa including MEM-NS isolates, susceptibility was ≥94% despite different BPs recommended by FDA (1 mg/L), EUCAST (2 mg/L) and CLSI (4 mg/L). This changed the proportion of IMP-producing isolates classified as susceptible from 100% (CLSI) and 81% (EUCAST) to only 19% (FDA). Against other non-fermenters, susceptibility was ≥91% irrespective of BP used.

Table 1. Susceptibility rates against Enterobacterales based on breakpoints from each organization

Table 2. Susceptibility rates against non-fermenters based on breakpoints from each organization

Conclusion

Differences in BPs between FDA, CLSI and EUCAST could impact on the reporting of susceptibility or resistance to CFDC, particularly for MEM-NS isolates. PK/PD model simulations support 100% fT >MIC up to an MIC of 4 mg/L, and in Phase 3 trials the mean trough concentration of unbound cefiderocol was >4 mg/L. The potential impact of these differences on clinical decision making are important as the greatest clinical utility for CDFC is expected to be in patients with carbapenem-resistant GN infections due to limited treatment options.

Disclosures

Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Christopher Longshaw, PhD, Shionogi B.V. (Employee) Roger Echols, MD, Shionogi Inc. (Consultant)

1252. In Vitro Activity of Cefiderocol Against Metallo-β-Lactamase-Producing Gram-Negative Bacteria Collected in North America and Europe Between 2014 and 2017: SIDERO-WT-2014–2016 Studies

Background

Metallo-β-lactamases (MBLs; eg, NDM, VIM, and IMP) can inactivate most commonly-used β-lactam antibiotics, including carbapenems. Infections caused by MBL producers are difficult to treat due to their resistance to many antibiotics. Cefiderocol (CFDC) is a siderophore cephalosporin antibiotic approved in the USA in 2019, with potent activity against carbapenem-resistant Gram-negative bacteria (GNB), including both serine- and metallo-carbapenemase positive strains. We evaluated the in vitro activity of CFDC and comparator agents against MBL-producing strains of GNB from North America and Europe in 3 years’ of consecutive surveillance studies (SIDERO-WT-2014–2016).

Methods

Susceptibility testing for CFDC, ceftazidime-avibactam (CZA), ceftolozane-tazobactam (C/T), meropenem (MEM), cefepime (FEP), ciprofloxacin (CIP), and colistin (CST) was performed by broth microdilution according to CLSI guidance. CFDC was tested in iron-depleted medium. A total of 275 MBL-producing strains, consisting of 120 Enterobacterales (45 NDM; 75 VIM), 5 NDM-producing Acinetobacter baumannii, and 150 Pseudomonas aeruginosa (134 VIM; 16 IMP), identified among 4985 (654 Enterobacterales and 4331 non-fermenters) MEM non-susceptible (based on CLSI breakpoints) strains were used for the current analysis.

Results

The minimum inhibitory concentration (MIC) range and MIC₉₀ for CFDC and comparators for each MBL-producing organism group are shown in the Table. Against NDM-producing Enterobacterales, of which 42% and 33% were isolated in Turkey and Russia, respectively, CFDC inhibited the growth of 84% of isolates tested at ≤4 µg/mL. CFDC MIC₉₀ was 4 μg/mL for VIM-producing Enterobacterales (41% and 31% isolated in Greece and Italy, respectively), 1 μg/mL for VIM-producing P. aeruginosa (50% isolated in Russia), and 4 μg/mL for IMP-producing P. aeruginosa (88% isolated in Czech Republic). Other comparators (except for CST) were not active against these MBL producers.

Table. MIC range and MIC90 (μg/mL) for CFDC and comparators of MBL-producing organisms

Conclusion

CFDC inhibited the growth of 100% of MBL-positive GNB at ≤8 mg/mL and showed MIC₉₀ of 4 μg/mL against all 275 MBL producers, indicating that CFDC has high potential for treating infections caused by these difficult-to-treat strains.

Disclosures

Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Krystyna Kazmierczak, PhD, Shionogi & Co., Ltd. (Independent Contractor) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor) Roger Echols, MD, Shionogi Inc. (Consultant) Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee)

1626. Synergistic Effect of Cefiderocol with Other Antibiotics Against PER-Producing Acinetobacter baumannii Isolates from the Multinational SIDERO-WT Studies

Background

Cefiderocol (CFDC), a novel siderophore cephalosporin, showed potent activity at minimum inhibitory concentrations (MICs) of ≤4 μg/mL against ≥99% of Gram-negative isolates in the multinational SIDERO-WT studies. PER-producing Acinetobacter baumannii, mainly from Russia, showed high CFDC MICs of 8– >64 μg/mL. This study evaluated the synergistic effects of CFDC combined with other antibiotics against PER-producing A. baumannii isolates with high CFDC MICs.

Methods

Two isolates of PER-producing A. baumannii with resistance to CFDC (MIC 16 μg/mL), meropenem (MEM; MIC 64 μg/mL), ceftazidime-avibactam (CZA; MIC 64/4 μg/mL), amikacin (AMK; MIC 32 or 64 μg/mL), and ciprofloxacin (CIP; MIC ≥64 μg/mL) were tested. Against ampicillin-sulbactam (SAM), one isolate was resistant (MIC 32/64 μg/mL) and another was susceptible (MIC 8/16 μg/mL). Effects of CFDC combined with other antibiotics were evaluated by checkerboard assay and chemostat model reproducing humanized antibiotic exposure. The checkerboard assay used a single agent (e.g. ceftazidime [CAZ], avibactam [AVI], ampicillin [AMP] or sulbactam [SUL]). Iron-depleted cation-adjusted Mueller‒Hinton broth was used as the standard medium for CFDC, as recommended by the Clinical Laboratory and Standards Institute.

Results

Against both isolates, synergy with CFDC was seen for two β-lactamase inhibitors, AVI and SUL, with a fractional inhibitory concentration (FIC) index of 0.026–0.033 and 0.26–0.27, respectively. A synergistic to additive effect was seen for MEM and AMK, with an FIC index of 0.53–0.75 and 0.25–0.52, respectively. In the chemostat model, regrowth during 24-h treatment was observed with single agents (CFDC 2 g, q8h, 3-h infusion; MEM 2 g, q8h, 1-h infusion; CZA 2 g, q8h, 2-h infusion; SAM 3 g, q8h, 3-h infusion; AMK 15 mg/kg, q8h, 3-h infusion) for both isolates, including the SAM-susceptible isolate. However, no regrowth was seen when CFDC was combined with CZA, MEM, SAM or AMK.

Conclusion

The most potent synergy was seen between CFDC and AVI against PER-producing A. baumannii with a decreased MIC to ≤1 µg/mL for all isolates, followed by SUL and MEM. Under humanized pharmacokinetic exposure, combination of CFDC and CZA, MEM, SAM or AMK is expected to be effective against PER-producing A. baumannii in spite of high CFDC MICs.

Disclosures

Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Naomi Anan, MSc, Shionogi & Co., Ltd. (Employee) Rio Nakamura, BSc, Shionogi & Co., Ltd. (Employee) Roger Echols, MD, Shionogi Inc. (Consultant)

165. Cefiderocol Treatment for Serious Infections Caused by Carbapenem-resistant Bacteria: Post-hoc Analysis of Outcomes by Pathogen in the CREDIBLE-CR Study

Background

The efficacy and safety of cefiderocol (CFDC), a novel siderophore cephalosporin, for the treatment of serious infections due to carbapenem-resistant (CR) Gram-negative pathogens was assessed in the CREDIBLE-CR study. The current analysis evaluated clinical and microbiological outcomes by baseline CR pathogen.

Methods

An open-label, prospective, randomised 2:1, Phase 3 study (CREDIBLE-CR; NCT02714595) was conducted in adult patients with hospital-acquired, ventilator-associated, and healthcare-associated pneumonia, bloodstream infections or sepsis, and complicated urinary tract infections caused by CR Gram-negative pathogens. Patients received either intravenous (IV) CFDC 2g, q8h, 3-h infusion, or IV best available therapy (BAT: up to 3 drugs in combination), for 7–14 days (extendable to 21 days). Clinical and microbiological outcomes were assessed in the CR microbiological intent-to-treat (CR-MITT) population by CR pathogen, baseline MIC and by mechanism of carbapenem resistance at test of cure (TOC). Only summary statistics were collected.

Results

In the CR-MITT population (CFDC N=80; BAT N=38), Acinetobacter baumannii (46.3% and 44.7%), Klebsiella pneumoniae (33.8% and 31.5%), and Pseudomonas aeruginosa (15% and 26%) were the most frequent pathogens in CFDC and BAT arms, respectively. For all CR pathogens, clinical cure rates were achieved in 52.5% in the CFDC arm and 50.0% in the BAT arm at TOC; rates were similar between treatment arms by baseline CR pathogen (Table 1). Numerically higher clinical cure and microbiological outcomes were observed with CFDC for Enterobacterales (Table 1), especially against NDM-producing bacteria or those with porin-channel mutations (Table 1). CFDC MIC values ranged between ≤0.03 and 4 μg/mL, except for one pathogen (Table 2). Microbiological outcomes for CR A. baumannii, CR K. pneumoniae, and CR P. aeruginosa at TOC by baseline MICs of ≤4 μg/mL ranged between 0–40%, 0–100%, and 0–100%, respectively; at MIC ≤4 μg/mL, clinical and microbiological outcomes were equal (Table 2).

Conclusion

CFDC, via a novel mechanism of entry and its stability against β-lactamases, was effective against serious infections caused by CR pathogens with various resistance mechanisms or baseline MIC values.

Disclosures

Yuko Matsunaga, MD, Shionogi Inc. (Employee) Mari Ariyasu, BPharm, Shionogi & Co., Ltd. (Employee) Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Kiichiro Toyoizumi, PhD, Shionogi & Co., Ltd. (Employee) Masahiro Kinoshita, MPharm, Shionogi & Co., Ltd. (Employee) Roger Echols, MD, Shionogi Inc. (Consultant) Tsutae Den Nagata, MD, Shionogi & Co., Ltd. (Employee)

1266. Characterization of Shifts in Minimum Inhibitory Concentrations During Treatment with Cefiderocol or Comparators in the Phase 3 CREDIBLE-CR and APEKS-NP Studies

Background

Cefiderocol (CFDC) is a novel siderophore cephalosporin developed to treat serious carbapenem-resistant (CR) Gram-negative (GN) infections.

Methods

In CREDIBLE-CR (NCT02714595), adults with serious infections caused by CR GN pathogens received CFDC 2 g, q8h, 3-h infusion, or best available therapy (BAT). In APEKS-NP (NCT03032380), adults with nosocomial pneumonia received CFDC or high-dose, extended-infusion meropenem (each 2 g, q8h, 3-h infusion). All treatments were given for 7‒14 days (extendable to 21 days). Biospecimens were collected before the first dose of study drug and at subsequent visits for assessments, and minimum inhibitory concentrations (MIC) to various antibiotics, including CFDC and carbapenems, were determined. Isolates with an increased MIC were evaluated by RT-PCR or whole genome sequencing (WGS) for CFDC resistance-related genes or mutations. Results for genetically related isolates with an elevated MIC during therapy are shown.

Results

On-therapy ≥4-fold CFDC MIC increase was found in 12 out of 106 (CREDIBLE-CR; Table 1) and 7 out of 159 (APEKS-NP; Table 2) isolates, respectively. For most isolates, CFDC MIC increased by 4–8-fold but remained ≤4 µg/mL. Specific mutations which could explain CFDC MIC increases were found in only 3 isolates. Mutations in iron-transport related genes were not identified. Mutation in CFDC target gene PBP-3 was identified in 1 A. baumannii isolate. Class-C enzyme mutation was observed in 2 isolates (CREDIBLE-CR: PDC-30 in P. aeruginosa; APEKS-NP: ACT-17 in E. cloacae), although the contribution to CFDC MIC increase has not been confirmed. In the BAT arm in CREDIBLE-CR, 6 out of 46 isolates had ≥4-fold MIC increase; all post-treatment isolates were resistant to BAT agents (Table 1), although WGS was not conducted for these isolates. In the meropenem arm in APEKS-NP, 5 out of 164 isolates had ≥4-fold MIC increase (Table 2).

Table 1. MIC changes in CREDIBLE-CR

Conclusion

Among isolates with ≥4-fold MIC increase during CFDC treatment, actual CFDC MIC values remained relatively low for most isolates. Frequency of MIC increase in BAT or meropenem arms was similar to that of CFDC, but the magnitude was greater. Acquisition of contributory mechanism has not been identified except for the mutation in PBP 3 and some β-lactamases.

Disclosures

Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Yuko Matsunaga, MD, Shionogi Inc. (Employee) Mari Ariyasu, BPharm, Shionogi & Co., Ltd. (Employee) Roger Echols, MD, Shionogi Inc. (Consultant) Tsutae Den Nagata, MD, Shionogi & Co., Ltd. (Employee)

1455. Potential Mechanisms of Cefiderocol MIC Increase in Enterobacterales in In Vitro Resistance Acquisition Studies

Background

Cefiderocol (CFDC) is a novel siderophore, iron-chelating cephalosporin, which is transported into bacteria via iron transporters. CFDC has potent in vitro and in vivo activity against all aerobic Gram-negative bacteria, including carbapenem-resistant strains. To date, clinical isolates with cefiderocol MIC >4 µg/mL have been found infrequently, in which the presence of a few β-lactamases or altered iron transport was found. We investigated potential new mechanisms causing CFDC MIC increases in non-clinical studies.

Methods

The mutation positions were determined by whole genome sequencing using four K. pneumoniae mutants including two KPC producers and one NDM producer that had shown CFDC MIC increases in previous in vitro resistance-acquisition studies. The mutant strains were obtained at the frequency of 10^-7 to < 10^-8 by spreading bacteria on standard Mueller‒Hinton agar medium containing CFDC at concentrations of 10× MIC, with or without apo-transferrin (20 μg/mL). CFDC MIC was determined by broth microdilution using iron-depleted cation-adjusted Mueller-Hinton broth based on Clinical and Laboratory Standards Institute guidelines. The emergence of MIC increase mutants was also assessed by in vitro chemostat models under humanized plasma pharmacokinetic exposures of CFDC.

Results

The possible resistance mechanisms were investigated. Mutation of baeS or envZ, sensors of two-component regulation systems, were found in three or two mutants among the tested four isolates, respectively, and caused the MIC to increase by 4–32-fold. The altered expression level of specific genes by the baeS or envZ mutation could affect CFDC susceptibility, but the specific genes have not been identified. In addition, the mutation of exbD, an accessory protein related to iron transport, was identified in one case and caused the MIC to increase by >8-fold. In vitro chemostat studies using two isolates (one NDM producer and one KPC producer) showed no resistance acquisition during 24-hour exposure.

Table. Overview of mutation emergence in five isolates of K. pneumoniae

Conclusion

The mutation of two-component regulation systems (BaeSR and OmpR/EnvZ) and iron transport-related proteins were shown to be possible mechanisms causing CFDC MIC increases, but these mutants did not appear under human exposures.

Disclosures

Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Rio Nakamura, BSc, Shionogi & Co., Ltd. (Employee) Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Roger Echols, MD, Shionogi Inc. (Consultant)

1452. Molecular Profile of β-Lactamase Genes and Siderophore-Dependent Iron Transporter Genes of Cefiderocol High MIC Isolates from SIDERO-WT Studies

Background

Cefiderocol (CFDC) is a novel siderophore cephalosporin with efficacy against Gram-negative (GN) bacteria, including carbapenem-resistant Enterobacterales and non-glucose-fermenters such as Pseudomonas aeruginosa and Acinetobacter baumannii. In consecutive multinational surveillance (SIDERO-WT) studies (2014–2017), CFDC demonstrated activity with minimum inhibitory concentrations (MICs) of ≤4 mg/mL against 99.4% of 28,629 GN clinical isolates. We conducted molecular characterization of 161 isolates with CFDC MICs >4 mg/mL from the SIDERO-WT studies.

Methods

A total of 161 isolates underwent whole genome sequencing by Illumina Hiseq. Analyses were done using the CLC genomics workbench (Qiagen) for possible resistance-related genes (e.g. β-lactamases, porin channels or penicillin-binding protein genes) and some TonB-dependent siderophore uptake receptor genes (fiu, cir, piu, pir). Fiu and Cir in Escherichia coli and Piu in P. aeruginosa are the iron transporters involved in CFDC transport.

Results

Of 161 isolates with CFDC MIC >4 mg/mL, 128 were A. baumannii, 22 Enterobacterales, 7 Burkholderia multivorans, 2 P. aeruginosa, and 2 Stenotrophomonas maltophilia. Genes encoding PER/VEB extended-spectrum β-lactamases and NDM-type metallo-β-lactamases were detected in some isolates, but other β-lactamase genes (bla) were not shown to be linked to high CFDC MICs. bla_PER/bla_VEB were found only in A. baumannii and bla_NDM was found in A. baumannii and Klebsiella pneumoniae. In 128 A. baumannii isolates, 103 harbored PER or VEB, including PER positive isolates from Russia (n=87) and Turkey (n=6) and 4 VEB positive isolates from USA. Nine NDM-positive isolates (7 K. pneumoniae, 2 A. baumannii) were found. Disruption of iron transport genes was also detected in some isolates, including piuA (11 A. baumannii, 1 P. aeruginosa), pirA (2 A. baumannii), and fiuA (4 B. multivorans, 1 Proteus mirabilis). No cir homologs were found in 2 B. multivorans.

Conclusion

PER and NDM could reduce susceptibility to CFDC, as such isolates have been seen in some countries. Iron transporter disruption was also observed in some isolates with high CFDC MICs; the contribution of these deficiencies in A. baumannii and B. multivorans requires further study.

Disclosures

Yoshinori Yamano, PhD, Shionogi & Co., Ltd. (Employee) Miki Takemura, MSc, Shionogi & Co., Ltd. (Employee) Krystyna Kazmierczak, PhD, Shionogi & Co., Ltd. (Independent Contractor) Mark G G. Wise, PhD, Shionogi & Co., Ltd. (Independent Contractor) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor) Roger Echols, MD, Shionogi Inc. (Consultant)

Activities of Cefiderocol with Simulated Human Plasma Concentrations against Carbapenem-Resistant Gram-Negative Bacilli in an In Vitro Chemostat Model

Activities of cefiderocol under simulated human plasma concentrations at the recommended dosing regimen of 2 g every 8 h with a 3-h infusion were evaluated using an in vitro chemostat model. Against a total of 6 meropenem-resistant Gram-negative strains with cefiderocol MICs of 0.5 to 4 μg/ml, including metallo-β-lactamase producers and carbapenem-resistant Acinetobacter baumannii, cefiderocol treatment showed a bactericidal effect within 8 h and sustained efficacy with no marked bacterial regrowth over 24 h.

Escherichia coli strains possessing a four amino acid YRIN insertion in PBP3 identified as part of the SIDERO-WT-2014 surveillance study

Background

In addition to carbapenemases, dissemination of recently reported Escherichia coli lineages possessing a four amino acid insertion in PBP3 (encoded by ftsI) that confers reduced susceptibility to PBP3-targeted β-lactams, such as ceftazidime, can pose a threat of antimicrobial resistance.

Objectives

To evaluate genotypic and phenotypic characteristics of E. coli possessing the mutated PBP3 collected during SIDERO-WT-2014 surveillance.

Methods

A subset of 65 E. coli clinical isolates with MICs ≥2 mg/L for ceftazidime/avibactam, ceftolozane/tazobactam or cefiderocol, among a total of 1529 isolates from the multinational surveillance study, were subjected to gene analysis and antimicrobial susceptibility testing. Isogenic PBP3 mutants were constructed to confirm experimentally an impact on antimicrobial susceptibility.

Results

Eleven strains possessing a YRIN-inserted PBP3 were identified, consisting of nine strains collected from the same hospital in Turkey (ST1284) and one each from the USA and Italy (ST361). Strains associated with each ST lineage possessed similar genetic backgrounds including β-lactamase genotypes; all nine strains from Turkey carried CMY-42, OXA-1 and the OXA-181 carbapenemase (five strains additionally carried CTX-M-15 ESBL), whereas the two other strains carried CMY-42 and TEM-1, indicating dissemination driven by selective pressure. The presence of the YRIN insertion contributed to reduced susceptibility to aztreonam, ceftazidime, cefepime and ceftolozane/tazobactam, although the strains remained susceptible to ceftazidime/avibactam despite relatively high MICs.

Conclusions

E. coli strains of both ST1284 and ST361 lineages, possessing YRIN-inserted PBP3, are disseminating in several regions. The YRIN insertion in PBP3 occurred with multiple β-lactamases, which indicates frequent cross-resistance to other β-lactams.

Reduced susceptibility mechanism to cefiderocol, a siderophore cephalosporin, among clinical isolates from a global surveillance programme (SIDERO-WT-2014)

OBJECTIVE

To investigate possible mechanistic factors to explain cefiderocol (CFDC) non-susceptibility, we characterized 38 clinical isolates with a CFDC minimum inhibitory concentration (MIC) of >4μg/mL from a multi-national surveillance study.

METHODS

The MIC measurement in the presence of β-lactamase inhibitors and whole genome sequencing were performed.

RESULTS

The MIC decrease of CFDC by β-lactamase inhibitors was observed against all of the test isolates. Among the 38 isolates, NDM and PER genes were observed in 5 and 25 isolates, respectively. No other β-lactamases responsible for high MIC were identified in the other eight isolates. The MIC of CDFC against Escherichia coli isogenic strains introduced with NDM and PER β-lactamase increased by ≥16-fold, suggesting the contribution of NDM and PER to the non-susceptibility to CFDC. Against NDM producers, a ≥8-fold MIC increase was observed only when both serine- and metallo-type β-lactamase inhibitors were added. In addition, many of the PER or NDM producers remained susceptible to CFDC. These results suggested that the presence of only NDM or PER would not lead to non-susceptibility to CFDC and that multiple factors would be related to CFDC resistance.

CONCLUSION

Multiple factors including NDM and PER could be related to reduced susceptibility to CFDC.

In vitro activity of the siderophore cephalosporin, cefiderocol, against molecularly characterized, carbapenem-non-susceptible Gram-negative bacteria from Europe

Objectives

Many carbapenem-resistant (CR) Gram-negative (GN) pathogens exhibit MDR, meaning few therapeutic options are available for CR-GN infections. Cefiderocol, a siderophore cephalosporin, has demonstrated in vitro efficacy against CR-GN bacteria. In the SIDERO-CR-2014–2016 surveillance study, European clinical isolates comprising carbapenem-non-susceptible (CarbNS) Enterobacterales and MDR non-fermenters were tested against cefiderocol and comparators.

Methods

Cefiderocol MICs were determined using iron-depleted CAMHB, and comparators using CAMHB, per recommended CLSI methodology. Carbapenemase gene profiles were determined using PCR.

Results

Isolates (N = 870) from 23 European countries comprised CarbNS Enterobacterales (n = 457), MDR Pseudomonas aeruginosa (n = 177) and MDR Acinetobacter baumannii (n = 236). The most common carbapenemases were KPC (52%), OXA-48-like (19%), VIM (14%) and NDM (8%) in Enterobacterales, VIM (41%) in P. aeruginosa and OXA-23-like (57%) and OXA-24/40-like (37%) in A. baumannii. Most carbapenemase-producing isolates (65%) co-carried ESBLs. Approximately half of P. aeruginosa isolates were negative for carbapenemases, compared with 10% of Enterobacterales and 3% of A. baumannii. A similar proportion of Enterobacterales were susceptible to cefiderocol (81.6%; 79.0% of VIM producers; 51.4% of NDM producers; based on EUCAST breakpoint values) compared with comparator antimicrobial agents, including colistin (76.4%; 93.5% of VIM producers; 78.4% of NDM producers) and ceftazidime/avibactam (76.6%; 1.6% of VIM producers; 2.7% of NDM producers). Of P. aeruginosa isolates, 98.3% were susceptible to cefiderocol (100% of VIM producers), similar to colistin (100%). Against A. baumannii, 94.9% had cefiderocol MIC ≤2 mg/L and 93.6% of isolates were susceptible to colistin.

Conclusions

Cefiderocol demonstrated potent activity against CarbNS and MDR GN bacteria, including non-fermenters and a wide variety of MBL- and serine-β-lactamase-producing strains.

THU0023 DETAILED PROFILE OF CO-OCCURRENCE OF RELAPSING POLYCHONDRITIS AND AUTOIMMUNE THYROID DISEASE

Background:

Relapsing polychondritis (RP) is a rare inflammatory disease, which is characterized by recurrent inflammation and destruction of cartilage tissues. RP also has the profile of autoimmune disease and is often complicated with other autoimmune disease. Autoimmune thyroid disease (AITD) is one of common autoimmune diseases, which consists of Graves’ disease (GD) and Hashimoto’s thyroiditis (HT). While RP is reported to be complicated with AITD1), there has been no study on detailed profile of co-occurrence of RP and AITD.

Objectives:

We aimed to reveal whether there is common (statistically significant) co-occurrence of RP and AITD. We also analyzed clinical and genetic profiles characterizing the co-occurrence.

Methods:

We recruited 117 patients with RP and checked their medical records in order to obtain the information about compilation of AITD and clinical features. In addition, we genotyped Human Leucocyte Antigen (HLA) A, B Cw, DRB1, DQB1 and DPB1 alleles for 88 of the 117 patients. Co-occurrence ratio was compared with prevalence of AITD in the Japanese population. Associations of co-occurrence of AITD with clinical manifestations or HLA alleles were analyzed among the patients.

Results:

Among the 117 patients with RP, 5 (4.3%) and 6 (5.1%) patients had GD and HT, respectively. Patients with RP were more likely to be complicated with GD (p=1.04×10-3, OR: 7.15, 95%CI 2.68~ 18.14) but not with HT (p=0.50, 95%CI 0.59~1.27), compared with prevalence in general Japanese population (0.62% and 5.9%, respectively2)). RP patients with GD showed a trend to have nasal involvement (100% vs 45.5%, p=0.023, OR: 2.58, 95%CI 1.09~∞). We did not observe any differences in clinical manifestation in patients with RP and HT. HLA- DPB1*02:02 demonstrated a trend toward GD complication (20% vs 2.3%, p=0.035, OR: 10.41, 95%CI 1.23~65.38). There were no association of HLA in the complication of HT among patients with RP.

Conclusion:

Patients with RP have high co-occurrence ratio of GD. Patients with the two diseases may be characterized by nasal involvement and HLA-DPB1*02:02.

References:

[1]Kung AW et al. Graves’ ophthalmopathy and relapsing polychondritis. Clin Exp Rheumatol. 1995 Jul-Aug;13(4):501-3.

[2]Nagataki S et al. Thyroid diseases among atomic bomb survivors in Nagasaki. JAMA. 1994 Aug 3;272(5):364-70.

Disclosure of Interests:

Toshiki Nakajima Speakers bureau: Bristol-Myers Squibb and Novartis, Hajime Yoshifuji Grant/research support from: Astellas Pharma. (Outside the field of the present study.), Speakers bureau: Chugai Pharmaceutical. (Outside the field of the present study.), Yoshihisa Yamano: None declared, Hiroshi Handa: None declared, Koichiro Ohmura Grant/research support from: Astellas Pharma, AYUMI Pharmaceutical, Chugai Pharmaceutical, Daiichi Sankyo, Eisai, Japan Blood Products Organization, Mitsubishi Tanabe Pharma, Nippon Kayaku, Nippon Shinyaku, Sanofi, and Takeda Pharmaceutical., Speakers bureau: AbbVie, Actelion Pharmaceuticals Japan, Asahi Kasei Pharma, AYUMI Pharmaceutical, Bristol-Myers Squibb, Chugai Pharmaceutical, Eisai, Eli Lilly and Company, GlaxoSmithKline, Janssen Pharmaceutical, Mitsubishi Tanabe Pharma, Novartis Pharma, and Sanofi., Tsuneyo Mimori: None declared, Chikashi Terao Grant/research support from: Actelion, Speakers bureau: Asteras, Asahi Kasei Pharma, Ono and Tanabe-Mitsubishi