Comparison of antimicrobial activity between ceftolozane-tazobactam and ceftazidime-avibactam against multidrug-resistant isolates of Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa

Antimicrobial Resistance Profiles of Pseudomonas aeruginosa in the Arabian Gulf Region Over a 12-Year Period (2010-2021)

OBJECTIVES

To evaluate literature from a 12-year period (2010-2021) on the antimicrobial resistance profile of Pseudomonas aeruginosa from the Arabian Gulf countries (Bahrain, Kuwait, Oman, Qatar, Saudi Arabia, and the United Arab Emirates).

METHODS

An electronic literature search was conducted for articles on antimicrobial resistance in P. aeruginosa and associated phenotypes, covering the period of 1st January 2010 to 1st December 2021.

RESULTS

Antimicrobial resistance in the Arabian Gulf was highest to meropenem (10.3-45.7%) and lowest to colistin (0.0-0.8%), among the agents tested. Annual data showed that ceftazidime resistance (Kuwait), piperacillin-tazobactam non-susceptibility (Qatar), and aztreonam, imipenem, and meropenem resistance (Saudi Arabia) increased by 12-17%. Multiple mechanisms of carbapenem resistance were identified and multiple clones were detected, including high-risk clones such as ST235. The most common carbapenemases detected were the VIM-type metallo-β-lactamases.

CONCLUSIONS

Among P. aeruginosa in the Arabian Gulf countries, resistance to meropenem was higher than to the other agents tested, and meropenem resistance increased in Saudi Arabia during the study period. Resistance to colistin, a classic antibiotic used to treat Pseudomonas spp. infections, remained low. The VIM-type β-lactamase genes were dominant. We recommend local and regional antimicrobial resistance surveillance programs to detect the emergence of resistance genes and to monitor antimicrobial resistance trends in P. aeruginosa.

Molecular characterization and descriptive analysis of carbapenemase-producing Gram-negative rod infections in Bogota, Colombia

In this study, the genetic differences and clinical impact of the carbapenemase-encoding genes among the community and healthcare-acquired infections were assessed. This retrospective, multicenter cohort study was conducted in Colombia and included patients infected with carbapenem-resistant Gram-negative rods between 2017 and 2021. Carbapenem resistance was identified by Vitek, and carbapenemase-encoding genes were identified by whole-genome sequencing (WGS) to classify the alleles and sequence types (STs). Descriptive statistics were used to determine the association of any pathogen or gene with clinical outcomes. A total of 248 patients were included, of which only 0.8% (2/248) had community-acquired infections. Regarding the identified bacteria, the most prevalent pathogens were Pseudomonas aeruginosa and Klebsiella pneumoniae. In the WGS analysis, 228 isolates passed all the quality criteria and were analyzed. The principal carbapenemase-encoding gene was blaKPC, specifically blaKPC-2 [38.6% (88/228)] and blaKPC-3 [36.4% (83/228)]. These were frequently detected in co-concurrence with blaVIM-2 and blaNDM-1 in healthcare-acquired infections. Notably, the only identified allele among community-acquired infections was blaKPC-3 [50.0% (1/2)]. In reference to the STs, 78 were identified, of which Pseudomonas aeruginosa ST111 was mainly related to blaKPC-3. Klebsiella pneumoniae ST512, ST258, ST14, and ST1082 were exclusively associated with blaKPC-3. Finally, no particular carbapenemase-encoding gene was associated with worse clinical outcomes. The most identified genes in carbapenemase-producing Gram-negative rods were blaKPC-2 and blaKPC-3, both related to gene co-occurrence and diverse STs in the healthcare environment. Patients had several systemic complications and poor clinical outcomes that were not associated with a particular gene.IMPORTANCEAntimicrobial resistance is a pandemic and a worldwide public health problem, especially carbapenem resistance in low- and middle-income countries. Limited data regarding the molecular characteristics and clinical outcomes of patients infected with these bacteria are available. Thus, our study described the carbapenemase-encoding genes among community- and healthcare-acquired infections. Notably, the co-occurrence of carbapenemase-encoding genes was frequently identified. We also found 78 distinct sequence types, of which two were novel Pseudomonas aeruginosa, which could represent challenges in treating these infections. Our study shows that in low and middle-income countries, such as Colombia, the burden of carbapenem resistance in Gram-negative rods is a concern for public health, and regardless of the allele, these infections are associated with poor clinical outcomes. Thus, studies assessing local epidemiology, prevention strategies (including trials), and underpinning genetic mechanisms are urgently needed, especially in low and middle-income countries.

Antimicrobial resistance profiles of Pseudomonas aeruginosa, Escherichia coli and Klebsiella pneumoniae strains isolated from broiler chickens

Globally, the spread of multidrug-resistant Pseudomonas aeruginosa, Escherichia coli, and Klebsiella pneumoniae from food to humans poses a severe threat to public health. The aim of this study was to assess the co-occurrence of colistin and β-lactamase resistance genes in E. coli, K. pneumoniae, and P. aeruginosa strains isolated from faeces of abattoir broiler chickens. The E. coli, P. aeruginosa and K. pneumoniae isolates were successfully detected from faecal samples by polymerase chain reaction (PCR) at infection rates of 60.7%, 22.5% and 16.7% respectively. The isolates displayed the highest levels of antibiotic resistance (AR) against ampicillin (82.3%) and amoxicillin-clavulanic acid (74.2%) for E. coli, followed by cefoxitin (70.6%) for K. pneumoniae, whilst P. aeruginosa displayed 26.1% antibiotic resistance (AR) against both ampicillin and colistin sulphate. The colistin mcr-1 gene was harboured by 46.8%, 47.1% and 21.7%, E. coli, K. pneumonia and P. aeruginosa isolates respectively. Ten out of 62 (16.1%), 6/17 (35.3%), 4/23 (17.4%) isolates were phenotypically classified as ESBL E. coli, K. pneumoniae, and P. aeruginosa respectively. The ESBL-E. coli isolates respectively possessed blaCTX-M (60%), blaTEM (20%) and blaCTX-M-9 (10%) genes. The ESBL-K. pneumoniae harboured, blaCTX-M (50%), blaOXA (33%), blaCARB (17%), and blaCTX-M-9 (17%) genes respectively, whilst, P. aeruginosa isolates respectively carried blaTEM (75%), blaCTX-M (50%), blaOXA (25%) and blaCARB (25%) genes. Molecular analysis identified the blaCTX-Mβ-lactamase-encoding genes collectively from E. coli, P. aeruginosa, K. pneumoniae isolates. Colistin and β-lactamase genes were present in only 16.7%, 6.9%, and 2.9% of E. coli, K. pneumoniae, and P. aeruginosa isolates, respectively. A total of 17, 7 and 3 isolates for E. coli, K. pneumoniae and P. aeruginosa respectively carried both colistin and β-lactamase antibiotics resistant genes. This is a public health threat that points to a challenge in the treatment of infections caused by these zoonotic bacteria. Data generated from this study will contribute to formulation of new strategies for combating spread of E. coli, K. pneumoniae, and P. aeruginosa isolates as well as prevention of their AR development.

In vitro activity of antibiotics potentially effective against difficult-to-treat strains of Gram-negative rods: retrospective study

Bacterial resistance surveillance is one of the main outputs of microbiological laboratories and its results are important part of antimicrobial stewardship (AMS). In this study, the susceptibility of specific bacteria to selected antimicrobial agents was tested. The susceptibility of 90 unique isolates of pathogens of critical priority obtained from clinically valid samples of ICU patients in 2017-2021 was tested. 50% of these fulfilled difficult-to-treat resistance (DTR) criteria and 50% were susceptible to all antibiotics included in the definition. 10 Enterobacterales strains met DTR criteria, and 2 (20%) were resistant to colistin (COL), 2 (20%) to cefiderocol (FCR), 7 (70%) to imipenem/cilastatin/relebactam (I/R), 3 (30%) to ceftazidime/avibactam (CAT) and 5 (50%) to fosfomycin (FOS). For Enterobacterales we also tested aztreonam/avibactam (AZA) for which there are no breakpoints yet. The highest MIC of AZA observed was 1 mg/l, MIC range in the susceptible cohort was 0.032-0.064 mg/l and in the DTR cohort (incl. class B beta-lactamase producers) it was 0.064-1 mg/l. Two (13.3%) isolates of Pseudomonas aeruginosa (15 DTR strains) were resistant to COL, 1 (6.7%) to FCR, 13 (86.7%) to I/R, 5 (33.3%) to CAT, and 5 (33.3%) to ceftolozane/tazobactam. All isolates of Acinetobacter baumannii with DTR were susceptible to COL and FCR, and at the same time resistant to I/R and ampicillin/sulbactam. New antimicrobial agents are not 100% effective against DTR. Therefore, it is necessary to perform susceptibility testing of these antibiotics, use the data for surveillance (including local surveillance) and conform to AMS standards.

Novel β-lactam-β-lactamase inhibitors as monotherapy versus combination for the treatment of drug-resistant Pseudomonas aeruginosa infections: A multicenter cohort study

BACKGROUND

Data comparing the clinical outcomes of novel β-lactam-β-lactamase inhibitors given in combination versus monotherapy for the treatment of multidrug-resistant (MDR) P. aeruginosa infections are lacking.

METHOD

This retrospective cohort study included patients who received novel β-lactam-β-lactamase inhibitors as monotherapy or in combination for the treatment of MDR P. aeruginosa infections. The study was conducted between 2017 and 2022 in 6 tertiary care hospitals in Saudi Arabia. Overall in-hospital mortality, 30-day mortality, clinical cure, and acute kidney injury (AKI) were compared between recipients of monotherapy versus combination using multivariate logistic regression analysis.

RESULT

118 patients and 82 patients were included in monotherapy and combination therapy arms, respectively. The cohort represented an ill population with 56% in the intensive care unit and 37% in septic shock. A total of 19% of patients presented with bacteremia. Compared to monotherapy, combination therapy did not significantly differ in clinical cure (57% vs. 68%; P = 0.313; OR, 0.63; 95% CI, 0.36-1.14) in-hospital mortality (45% vs. 37%; P = 0.267; OR, 1.38; 95% CI, 0.78-2.45), or 30-day mortality (27% vs. 24%; P = 0.619; OR, 1.18; 95% CI, 0.62-1.25). However, AKI (32% vs. 12%; P = 0.0006; OR, 3.45; 95% CI, 1.67-7.13) was significantly more common in patients who received combination therapy.

CONCLUSION

Novel β-lactam-β-lactamase inhibitors when used in combination with other antibiotics did not add clinical benefit compared to their use as monotherapy in the treatment of MDR P. aeruginosa infections. A Combination regimen was associated with an increased risk of nephrotoxicity.

Antimicrobial and Diagnostic Stewardship of the Novel β-Lactam/β-Lactamase Inhibitors for Infections Due to Carbapenem-Resistant Enterobacterales Species and Pseudomonas aeruginosa

Carbapenem-resistant Gram-negative bacterial infections are a major public health threat due to the limited therapeutic options available. The introduction of the new β-lactam/β-lactamase inhibitors (BL/BLIs) has, however, altered the treatment options for such pathogens. Thus, four new BL/BLI combinations-namely, ceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactam, and ceftolozane/tazobactam-have been approved for infections attributed to carbapenem-resistant Enterobacterales species and Pseudomonas aeruginosa. Nevertheless, although these antimicrobials are increasingly being used in place of other drugs such as polymyxins, their optimal clinical use is still challenging. Furthermore, there is evidence that resistance to these agents might be increasing, so urgent measures should be taken to ensure their continued effectiveness. Therefore, clinical laboratories play an important role in the judicious use of these new antimicrobial combinations by detecting and characterizing carbapenem resistance, resolving the presence and type of carbapenemase production, and accurately determining the minimum inhibitor concentrations (MICs) for BL/BLIs. These three targets must be met to ensure optimal BL/BLIs use and prevent unnecessary exposure that could lead to the development of resistance. At the same time, laboratories must ensure that results are interpreted in a timely manner to avoid delays in appropriate treatment that might be detrimental to patient safety. Thus, we herein present an overview of the indications and current applications of the new antimicrobial combinations and explore the diagnostic limitations regarding both carbapenem resistance detection and the interpretation of MIC results. Moreover, we suggest the use of alternative narrower-spectrum antibiotics based on susceptibility testing and present data regarding the effect of synergies between BL/BLIs and other antimicrobials. Finally, in order to address the absence of a standardized approach to using the novel BL/BLIs, we propose a diagnostic and therapeutic algorithm, which can be modified based on local epidemiological criteria. This framework could also be expanded to incorporate other new antimicrobials, such as cefiderocol, or currently unavailable BL/BLIs such as aztreonam/avibactam and cefepime/taniborbactam.

Carbapenem-resistant Klebsiella pneumoniae outbreak with monoclonal spread: Evaluation of resistance genes and ceftazidime-avibactam susceptibility

PURPOSE

The aim of this study was to investigate ceftazidime-avibactam (CAZ-AVI) susceptibility, carbapenemase genes, and clonal relationship in carbapenem-resistant Klebsiella pneumoniae (CrKp) isolates.

METHODS

A total of 28 non-repetitive CrKp isolates with positive carbapenemase production determined by the modified carbapenem inactivation method (mCIM), were included in the study. Identification of the isolates was performed with MALDI-TOF MS (VITEK-MS, bioMerieux, France). The automated system (VITEK-2, bioMerieux) and gradient diffusion test (Etest, bioMerieux) were used to determine antibiotic susceptibility. The mCIM was performed according to CLSI (2021) recommendations. CAZ-AVI susceptibility was carried out using the standard disc diffusion method. Results were evaluated according to EUCAST 2022 criteria. The blaOXA-48, blaNDM, blaKPC, blaIMP and blaVIM genes were investigated by multiplex PCR. The clonal relationship between isolates was determined by both AP-PCR and PFGE methods.

RESULTS

Of the total 28 isolates, 89.3% were susceptible to CAZ-AVI. blaOXA-48 gene was found in 85.7% of the isolates, blaOXA-48+blaNDM gene in 10.7%, and blaNDM gene in 3.6%. blaKPC, blaIMP and blaVIM genes were not detected. Three clusters with three different genotypes were determined by the PFGE method. The largest cluster was Genotype A (n:24), followed by Genotype B (n:3), and Genotype C (n:1). AP-PCR was highly compatible with PFGE. The isolates of Genotype A, mostly from the intensive care unit (ICU), were evaluated as outbreak strains with monoclonal dissemination.

CONCLUSIONS

OXA-48 remains the most frequently detected enzyme in CrKp strains in our country. The ceftazidime-avibactam susceptibility rate of 89.3% indicates that this antibiotic is still effective against CrKp isolates. The unnoticed outbreak detected in our study revealed the severity of intra-hospital cross-contamination affecting different wards, including the ICU. Therefore, in order to limit the spread of CrKp isolates, it is of great importance to implement strict infection control measures, and molecular surveillance programs, especially in the ICU.

Ceftolozane-Tazobactam Versus Ceftazidime-Avibactam for the Treatment of Infections Caused by Multidrug-Resistant Pseudomonas aeruginosa: a Multicenter Cohort Study

Ceftolozane-tazobactam (C-T) and ceftazidime-avibactam (CAZ-AVI) are two novel antimicrobials that retain activity against resistant Pseudomonas aeruginosa. The comparative effectiveness and safety of C-T versus CAZ-AVI remain unknown. A retrospective, multicenter cohort study was performed in six tertiary centers in Saudi Arabia and included patients who received either C-T or CAZ-AVI for infections due to multidrug-resistant (MDR) P. aeruginosa. Overall in-hospital mortality, 30-day mortality, and clinical cure were the main study outcomes. Safety outcomes were also evaluated. A multivariate analysis using logistic regression was used to determine the independent impact of treatment on the main outcomes of interest. We enrolled 200 patients in the study (100 in each treatment arm). A total of 56% were in the intensive care unit, 48% were mechanically ventilated, and 37% were in septic shock. Approximately 19% of patients had bacteremia. Combination therapy was administered to 41% of the patients. The differences between the C-T and CAZ-AVI groups did not reach statistical significance in the overall in-hospital mortality (44% versus 37%; P = 0.314; OR, 1.34; 95% CI, 0.76 to 2.36), 30-day mortality (27% versus 23%; P = 0.514; OR, 1.24; 95% CI, 0.65 to 2.35), clinical cure (61% versus 66%; P = 0.463; OR, 0.81; 95% CI, 0.43 to 1.49), or acute kidney injury (23% versus 17%; P = 0.289; OR, 1.46; 95% CI, 0.69 to 3.14), even after adjusting for differences between the two groups. C-T and CAZ-AVI did not significantly differ in terms of safety and effectiveness, and they serve as potential options for the treatment of infections caused by MDR P. aeruginosa.

Feasibility of Using Ceftazidime-Avibactam as a Therapeutic Option for Bloodstream Infections Caused by Multidrug-Resistant Enterobacterales and Pseudomonas aeruginosa Based on Its Susceptibility Profile

Background In the era of increased antimicrobial resistance, there are limited therapeutic options available for the treatment of bacteremia caused by multidrug-resistant organisms (MDROs). This study aims to find out the feasibility of using ceftazidime/avibactam (CZA) as a therapeutic option for bloodstream infections caused by multidrug-resistant (MDR) Enterobacterales and Pseudomonas aeruginosa based on its susceptibility profile. Materials and methods The isolates were routinely subjected to antimicrobial susceptibility testing (AST) by an automated AST system (VITEK-2). Those isolates found as MDR (resistant to at least one drug for ≥3 antimicrobial classes) were tested against CZA by Kirby-Bauer's disk diffusion (kb-DD) method. Results A total number of 293 MDR Enterobacterales and 31 MDR P. aeruginosa isolates were included. Of these, 87.3% of isolates were found as carbapenem-resistant (CR), whereas 12.7% of isolates were found as carbapenem susceptible. About 30.6% of MDROs were susceptible to CZA. Among carbapenem-resistant organisms (CROs), CR Klebsiella pneumoniae(33.5%) is most susceptible to CZA, compared to CR P. aeruginosa(0%)and CREscherichia coli(3.2%). Among the MDR isolates that were susceptible to CZA (30.6%), the majority had poor susceptibility against other β-lactam-β-lactamase inhibitor (BL-BLI) agents. Among all antimicrobial agents tested against CROs, colistin (96%) was found to have the best susceptibility profile. Conclusion It is observed that CZA is an acceptable therapeutic option for the treatment of bacteremia caused by MDROs, especially CROs. Therefore, it is important for the laboratories to perform the AST for CZA if the healthcare settings intend to use CZA for the management of such "difficult-to-treat" bloodstream infections.

Ertapenem Supplemented Selective Media as a New Strategy to Distinguish β-Lactam-Resistant Enterobacterales: Application to Clinical and Wastewater Samples

The increase in carbapenem-resistant Enterobacterales (CRE) is mostly driven by the spread of carbapenemase-producing (CP) strains. In New Caledonia, the majority of carbapenemases found are IMP-type carbapenemases that are difficult to detect on routine selective media. In this study, a culture-based method with ertapenem selection is proposed to distinguish non-CRE, non-CP-CRE, and CP-CRE from samples with very high bacterial loads. Firstly, assays were carried out with phenotypically well-characterized β-lactam-resistant Enterobacterales isolates. Then, this approach was applied to clinical and environmental samples. Presumptive CP-CRE isolates were finally identified, and the presence of a carbapenemase was assessed. In a collection of 27 phenotypically well-characterized β-lactam-resistant Enterobacterales, an ertapenem concentration of 0.5 µg·mL^-1 allowed distinguishing CRE from non-CRE. A concentration of 4 µg·mL^-1 allowed distinguishing CP-CRE from non-CP-CRE after nine hours of incubation. These methods allowed isolating 18 CP-CRE from hospital effluents, including the first detection of a KPC in New Caledonia. All these elements show that this cost-effective strategy to distinguish β-lactam-resistant Enterobacterales provides fast and reliable results. This could be applied in the Pacific islands or other resource-limited settings, where limited data are available.

Evaluation of in-vitro susceptibility of ß-lactam-resistant Gram-negative bacilli to ceftazidime-avibactam and ceftolozane-tazobactam from clinical samples of a general hospital in southern Brazil

BACKGROUND

The spread of carbapenemase- and extended-spectrum β-lactamase (ESBL)-producing gram-negative bacilli (GNB) represent a global public health threat that limits therapeutic options for hospitalized patients. This study aimed to evaluate the in-vitro susceptibility of β-lactam-resistant GNB to ceftazidime-avibactam (C/A) and ceftolozane-tazobactam (C/T), and investigate the molecular determinants of resistance.

METHODS

Overall, 101 clinical isolates of Enterobacterales and Pseudomonas aeruginosa collected from a general hospital in Brazil were analyzed. Susceptibility to the antimicrobial agents was evaluated using an automated method, and the minimum inhibitory concentrations (MIC50/90) of C/A and C/T were determined using Etest®. The β-lactamase-encoding genes were investigated using polymerase chain reaction.

RESULTS

High susceptibility to C/A and C/T was observed among ESBL-producing Enterobacterales (100% and 97.3% for CLSI and 83.8% for BRCAST, respectively) and carbapenem-resistant P. aeruginosa (92.3% and 87.2%, respectively). Carbapenemase-producing Klebsiella pneumoniae exhibited high resistance to C/T (80%- CLSI or 100%- BRCAST) but high susceptibility to C/A (93.4%). All carbapenem-resistant K. pneumoniae isolates were susceptible to C/A, whereas only one isolate was susceptible to C/T. Both antimicrobials were inactive against metallo-β-lactamase-producing K. pneumoniae isolates. Resistance genes were concomitantly identified in 44 (44.9%) isolates, with bla CTX-M and bla SHV being the most common.

CONCLUSIONS

C/A and C/T were active against microorganisms with β-lactam-resistant phenotypes, except when resistance was mediated by metallo-β-lactamases. Most C/A- and C/T-resistant isolates concomitantly carried two or more β-lactamase-encoding genes (62.5% and 77.4%, respectively).

Activity of ceftolozane/tazobactam against clinical isolates of Pseudomonas aeruginosa from patients in the Middle East and Africa - Study for Monitoring Antimicrobial Resistance Trends (SMART) 2017-2020

OBJECTIVES

We evaluated the activity of ceftolozane/tazobactam (C/T), and comparators against clinical Pseudomonas aeruginosa isolates collected for the global Study for Monitoring Antimicrobial Resistance Trends (SMART) surveillance program in ten countries in the Middle East and Africa to augment scarce standardized surveillance data in this region.

METHODS

Minimum inhibitory concentrations (MICs) were determined using Clinical and Laboratory Standards Institute broth microdilution and interpreted with European Committee on Antimicrobial Susceptibility Testing breakpoints. P. aeruginosa isolates testing with C/T MIC >4 mg/l or imipenem MIC >2 mg/l were screened for β-lactamase genes.

RESULTS

C/T was active against 91.4% and 87.0% of P. aeruginosa isolates from the Middle East and Africa, respectively (14-21 and 7-16 percentage points higher than most β-lactam comparators, respectively). Considerable variation in susceptibility was seen across countries, which largely correlated with the observed prevalence of carbapenemases and/or extended-spectrum β-lactamases. Differences across countries were smaller for C/T than for the β-lactam comparators, ranging from 81% C/T-susceptible among isolates from Jordan to 95% for Qatar. Among subsets resistant to meropenem, ceftazidime, or piperacillin/tazobactam, C/T maintained activity against 51-73% of isolates from the Middle East and against 27-54% from Africa (where metallo-β-lactamase and GES carbapenemase rates were higher).

CONCLUSION

Given the desirability of β-lactam use among clinicians, C/T represents an important option in the treatment of infections caused by P. aeruginosa.

Clinical carbapenem-resistant Klebsiella pneumoniae isolates simultaneously harboring blaNDM-1, blaOXA types and qnrS genes from the Kingdom of Bahrain: Resistance profile and genetic environment

The prevalence of Carbapenem-resistant Klebsiella pneumoniae (CRKP) is currently increasing worldwide, prompting WHO to classify it as an urgent public health threat. CRKP is considered a difficult to treat organism owing to limited therapeutic options. In this study, a total of 24 CRKP clinical isolates were randomly collected from Salmaniya Medical Complex, Bahrain. Bacterial identification and antibiotic susceptibility testing were performed, on MALDI-TOF and VITEK-2 compact, respectively. The isolates were screened for carbapenem resistance markers (bla_NDM,bla_OXA-23,bla_OXA-48 and bla_OXA-51) and plasmid-mediated quinolone resistance genes (qnrA, qnrB, and qnrS) by monoplex PCR. On the other hand, only colistin-resistant isolates (n=12) were screened for MCR-1, MCR-2 and MCR-3 genes by monoplex PCR. Moreover, the Genetic environment of bla_NDM, integrons analysis, and molecular characterization of plasmids was also performed. Antibiotic susceptibility revealed that all the isolates (100%) were resistant to ceftolozane/tazobactam, piperacillin/tazobactam, 96% resistant to ceftazidime, trimethoprim/sulfamethoxazole, 92% resistant to meropenem, gentamicin and cefepime, 88% resistant to ciprofloxacin, imipenem, and 37% resistant to amikacin. Ceftazidime/avibactam showed the least resistance (12%). 75% (n=12/16) were resistant to colistin and 44% (n=7/16) showed intermediate susceptibility to tigecycline. The detection of resistant determinants showed that the majority (95.8%) of CRKP harbored bla_NDM-1, followed by bla_OXA-48 (91.6%) bla_OXA-51 (45.8%), and bla_OXA-23 (41.6%). Sequencing of the bla_NDM amplicons revealed the presence of bla_NDM-1. Alarmingly, 100% of isolates showed the presence of qnrS. These predominant genes were distributed in various combinations wherein the majority were bla_NDM-1 + bla_OXA-51+ qnrS + bla_OXA-48 (n =10, 41.7%), bla_NDM-1 + bla_OXA-23+ qnrS + bla_OXA-48 (n=8, 33.3%), among others. In conclusion, the resistance rate to most antibiotics is very high in our region, including colistin and tigecycline, and the genetic environment of CRKP is complex with the carriage of multiple resistance markers. Resistance to ceftazidime/avibactam is uncommon and hence can be used as a valuable option for empirical therapy. Molecular data on resistance markers and the genetic environment of CRKP is lacking from this geographical region; this would be the first report addressing the subject matter. Surveillance and strict infection control strategies should be reinforced in clinical settings to curb the emergence and spread of such isolates.

John TJL, Ghazi IM. Is Cefoxitin a Carbapenem Sparing Agent in the Management of Urinary Tract Infections Caused by ESBL Producing Enterobacterales?

Background: Cefoxitin has shown in vitro activity against Extended-Spectrum β-Lactamase (ESBL) producing Enterobacterales. Outcome data regarding cefoxitin as a carbapenem sparing agent in the management of urinary tract infections (UTI) are scarce. We sought to evaluate the clinical and microbiologic efficacy of cefoxitin as compared to ertapenem. Methods: A retrospective observational study was conducted at our quaternary care institution between May 2015 and March 2019. We identified all patients who received cefoxitin for the treatment of UTI during the study period and used Charlson Comorbidity Index to select a matching cohort from patients who received ertapenem. Primary end points were clinical and microbiological cure. Results: Thirty patients who received cefoxitin were matched with 55 patients who received ertapenem. Clinical cure was marginally in favor of ertapenem: 83.2% in cefoxitin group versus 96.8% in ertapenem group (P = .042). However, 90-day recurrence was in favor of cefoxitin: 13.5% in cefoxitin group versus 34.8% in ertapenem group (P = .045). Microbiologic cure was not significant between the 2 groups with 88.6% success in cefoxitin versus 100% in ertapenem. Additionally, the group difference on 30-day recurrence or relapse rates and the 90-day mortality rate were not clinically significant. Conclusion: Cefoxitin achieved similar microbiologic cure rate when compared to ertapenem for the treatment of UTI caused by ESBL-producing Enterobacterales. No significant differences were found in 30-day recurrence/relapse or mortality rates. Larger randomized controlled trials are required to identify the clinical sittings in which cefoxitin could be used as a carbapenem-sparing agent in the treatment of UTI.

The Role of Colistin in the Era of New β-Lactam/β-Lactamase Inhibitor Combinations

With the current crisis related to the emergence of carbapenem-resistant Gram-negative bacteria (CR-GNB), classical treatment approaches with so-called “old-fashion antibiotics” are generally unsatisfactory. Newly approved β-lactam/β-lactamase inhibitors (BLBLIs) should be considered as the first-line treatment options for carbapenem-resistant Enterobacterales (CRE) and carbapenem-resistant Pseudomonas aeruginosa (CRPA) infections. However, colistin can be prescribed for uncomplicated lower urinary tract infections caused by CR-GNB by relying on its pharmacokinetic and pharmacodynamic properties. Similarly, colistin can still be regarded as an alternative therapy for infections caused by carbapenem-resistant Acinetobacter baumannii (CRAB) until new and effective agents are approved. Using colistin in combination regimens (i.e., including at least two in vitro active agents) can be considered in CRAB infections, and CRE infections with high risk of mortality. In conclusion, new BLBLIs have largely replaced colistin for the treatment of CR-GNB infections. Nevertheless, colistin may be needed for the treatment of CRAB infections and in the setting where the new BLBLIs are currently unavailable. In addition, with the advent of rapid diagnostic methods and novel antimicrobials, the application of personalized medicine has gained significant importance in the treatment of CRE infections.

Ceftazidime/Avibactam versus Polymyxin B in the Challenge of Carbapenem-Resistant Pseudomonas aeruginosa Infection

Purpose

Ceftazidime/avibactam (CAZ/AVI) monotherapy and polymyxin B-based combination therapy are currently two treatment options for patients with carbapenem-resistant Pseudomonas aeruginosa (CRPA) infection; however, few studies have contrasted the relative efficacy of the two antibiotic regimens. The purpose of this study was to compare the effectiveness of CAZ/AVI and polymyxin B against CRPA infection and analyze the independent predictors of 30-day mortality or survival.

Patients and Methods

This single-center retrospective observational study included patients with CRPA infection treated with CAZ/AVI or polymyxin B between January 2018 and December 2020. The primary outcomes were the 14-day and 30-day mortality. The secondary outcomes were in-hospital mortality and bacterial clearance. Baseline characteristics and outcomes were compared between the two groups, and COX regression analysis was used to identify predictors of 30-day mortality.

Results

A total of 136 patients with CRPA infection were enrolled, including 51 patients in the CAZ/AVI group and 85 patients in the polymyxin B group. The 14-day mortality (5.9% vs 27.1%, p=0.002), 30-day mortality (13.7% vs 47.1%, p<0.001) and in-hospital mortality (29.4% vs 60.0%, p=0.001) in the CAZ/AVI group were significantly lower than the polymyxin B group. The bacterial clearance rate (45.1% vs 12.9%, p<0.001) in the CAZ/AVI group were higher than in the polymyxin B group. After adjustment by propensity score matching, the CAV/AVI group still had lower 30-day mortality (14.3% vs 42.9%, p=0.018) and higher bacterial clearance rate (42.9% vs 14.3%, p=0.018) than the polymyxin B group. The multivariate COX analysis showed that the age was identified as independent predictor of 30-day mortality while CAZ/AVI therapy and central venous catheterization emerged as independent predictors of 30-day survival.

Conclusion

CAZ/AVI therapy was superior to polymyxin B therapy for patients with CRPA infection, and provided significant survival benefits, but further larger studies were needed to substantiate our findings.

New β-Lactam Antibiotics and Ceragenins - A Study to Assess Their Potential in Treatment of Infections Caused by Multidrug-Resistant Strains of Pseudomonas aeruginosa

Background

The increasing number of infections caused by antibiotic resistant strains of Pseudomonas aeruginosa posed a very serious challenge for clinical practice. This standing is driving scientists to develop new antibiotics against these microorganisms.

Methods

In this study, we measured the MIC/MBC values and estimated the ability of tested molecules to prevent bacterial biofilm formation to explore the effectiveness of β-lactam antibiotics ceftolozane/tazobactam, ceftazidime/avibactam, meropenem/vaborbactam, and ceragenins CSA-13, CSA-44, and CSA-131 against 150 clinical isolates of Pseudomonas aeruginosa that were divided into five groups, based on their antibiotic resistance profiles to beta-lactams. Selected strains of microorganisms from each group were also subjected to prolonged incubations (20 passages) with ceragenins to probe the development of resistance towards those molecules. Cytotoxicity of tested ceragenins was evaluated using human red blood cell (RBCs) hemolysis and microscopy observations of human lung epithelial A549 cells after ceragenin treatment. Poloxamer 407 (pluronic F-127) at concentrations ranging from 0.5% to 5% was tested as a potential drug delivery substrate to reduce ceragenin toxicity.

Results

Collected data proved that ceragenins at low concentrations are highly active against clinical strains of Pseudomonas aeruginosa regardless of their resistance mechanisms to conventional antibiotics. Ceragenins also show low potential for resistance development, high antibiofilm activity, and controlled toxicity when used together with poloxamer 407.

Conclusion

This data strongly supports the need for further study directed to develop this group of molecules as new antibiotics to fighting infections caused by antibiotic resistant strains of Pseudomonas aeruginosa.

Comparison of novel rapid diagnostic of blood culture identification and antimicrobial susceptibility testing by Accelerate Pheno system and BioFire FilmArray Blood Culture Identification and BioFire FilmArray Blood Culture Identification 2 panels

Background

Conventional turnaround time (TAT) for positive blood culture (PBC) identification (ID) and antimicrobial susceptibility testing (AST) is 2–3 days. We evaluated the TAT and ID/AST performance using clinical and seeded samples directly from PBC bottles with different commercial approaches: (1) Accelerate Pheno® system (Pheno) for ID/AST; (2) BioFire® FilmArray® Blood Culture Identification (BCID) Panel and/ or BCID2 for ID; (3) direct AST by VITEK® 2 (direct AST); and (4) overnight culture using VITEK® 2 colony AST.

Results

A total of 141 PBC samples were included in this evaluation. Using MALDI-TOF (Bruker MALDI Biotyper) as the reference method for ID, the overall monomicrobial ID sensitivity/specificity are as follows: Pheno 97.9/99.9%; BCID 100/100%; and BCID2 100/100%, respectively. For AST performance, broth microdilution (BMD) was used as the reference method. For gram-negatives, overall categorical and essential agreements (CA/EA) for each method were: Pheno 90.3/93.2%; direct AST 92.6/88.5%; colony AST 94.4/89.5%, respectively. For gram-positives, the overall CA/EAs were as follows: Pheno 97.2/98.89%; direct AST 97.2/100%; colony AST 97.2/100%, respectively. The BCID/BCID2 and direct AST TATs were around 9–20 h (1/9-19 h for ID with resistance markers/AST), with 15 min/sample hands-on time. In comparison, Pheno TATs were around 8–10 h (1.5/7 h for ID/AST) with 2 min/sample hands-on time, maintains a clinically relevant fast report of antibiotic minimal inhibitory concentration (MIC) and allows for less TAT and hands-on time.

Conclusion

In conclusion, to the best of our knowledge, this is the first study conducted as such in Asia; all studied approaches achieved satisfactory performance, factors such as TAT, panel of antibiotics choices and hands-on time should be considered for the selection of appropriate rapid ID and AST of PBC methods in different laboratory settings.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02403-y.

The ERACE-PA Global Surveillance Program: Ceftolozane/tazobactam and Ceftazidime/avibactam in vitro Activity against a Global Collection of Carbapenem-resistant Pseudomonas aeruginosa

The cephalosporin-β-lactamase-inhibitor-combinations, ceftolozane/tazobactam and ceftazidime/avibactam, have revolutionized treatment of carbapenem-resistant Pseudomonas aeruginosa (CR-PA). A contemporary assessment of their in vitro potency against a global CR-PA collection and an assessment of carbapenemase diversity are warranted. Isolates determined as CR-PA by the submitting site were collected from 2019-2021 (17 centers in 12 countries) during the ERACE-PA Global Surveillance Program. Broth microdilution MICs were assessed per CLSI standards for ceftolozane/tazobactam, ceftazidime/avibactam, ceftazidime, and cefepime. Phenotypic carbapenemase testing was conducted (modified carbapenem inactivation method (mCIM)). mCIM positive isolates underwent genotypic carbapenemase testing using the CarbaR, the CarbaR NxG, or whole genome sequencing. The MIC50/90 was reported as well as percent susceptible (CLSI and EUCAST interpretation). Of the 807 isolates, 265 (33%) tested carbapenemase-positive phenotypically. Of these, 228 (86%) were genotypically positive for a carbapenemase with the most common being VIM followed by GES. In the entire cohort of CR-PA, ceftolozane/tazobactam and ceftazidime/avibactam had MIC50/90 values of 2/ > 64 and 4/64 mg/L, respectively. Ceftazidime/avibactam was the most active agent with 72% susceptibility per CLSI compared with 63% for ceftolozane/tazobactam. For comparison, 46% of CR-PA were susceptible to ceftazidime and cefepime. Against carbapenemase-negative isolates, 88 and 91% of isolates were susceptible to ceftolozane/tazobactam and ceftazidime/avibactam, respectively. Ceftolozane/tazobactam and ceftazidime/avibactam remained highly active against carbapenem-resistant P. aeruginosa, particularly in the absence of carbapenemases. The contemporary ERACE-PA Global Program cohort with 33% carbapenemase positivity including diverse enzymology will be useful to assess therapeutic options in these clinically challenging organisms with limited therapies.

Clinical Distribution Characteristics of 1439 Carbapenem-Resistant Escherichia coli Strains in China: Drug Resistance, Geographical Distribution, Antibiotic MIC50/90

Purpose

To explore the clinical distribution characteristics and antimicrobial susceptibilities of carbapenem-resistant Escherichia coli (CR-ECO) in Hebei Province, China, from 2017 to 2019, and provide data on the treatment of this bacterial infection and the prevention of its spread.

Materials and Methods

A total of 1439 CR-ECO strains were collected from 2017 to 2019 in Hebei Province, China. Drug sensitivity tests were performed using the minimum inhibitory concentration (MIC) method, and the data were analyzed statistically using WHONET5.6 software.

Results

A total of 54,377 strains of Escherichia coli were isolated in Hebei Province from 2017 to 2019, of which 1439 strains were CR-ECO (2.65%). The highest proportion (33.78%) of strains was isolated from urine, and the detection rate showed a slow downward trend over the past 3 years. CR-ECO was mainly detected in densely populated and economically developed areas. Of all the patients, 54.2% were from the medical ward; the ratio of male to female patients with CR-ECO infections was 1.35:1; elderly patients and adults accounted for 59.6% and 30.8%, respectively, whereas minors and newborns accounted for 4.9% and 4.7%, respectively. For CR-ECO, the drug resistance rates to β-lactams were all higher than 80% and there was an annual increasing trend, while the drug resistance rates to quinolones remained nearly unchanged. The rate of resistance to aminoglycosides was relatively low, especially to amikacin (approximately 22%). The MIC50 of other antibacterial drugs, except amikacin, was equal to or higher than the break point of drug resistance.

Conclusion

From 2017 to 2019, the isolation rate of CR-ECO in Hebei Province, China, remained stable; however, the drug resistance rate showed an upward trend, primarily in cases of urinary tract infections in older men; the resistance rate to amikacin was the lowest.

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Emerging Status of Multidrug-Resistant Bacteria and Fungi in the Arabian Peninsula

Simple Summary

The incidence and developing status of multidrug-resistant bacteria and fungi, as well as their related mortality, is reviewed by a systematic published literature search from nine countries in the Arabian Peninsula. In order to analyse the emerging status and mortality, a total of 382 research articles were selected from a comprehensive screening of 1705 papers. More than 850 deaths reported since 2010 in the Arabian Peninsula due to the infection of multidrug-resistant bacteria and fungi. Multidrug-resistant bacteria Acinetobacter baumannii, Mycobacterium tuberculosis, Staphylococcus aureus, and fungi Candida auris are the most prevalent and causing high deaths. To control these infections and associated deaths in the Arabian Peninsula, continuous preventive measures, accurate methods for early diagnosis of infection, active surveillance, constant monitoring, developing vaccines, eradicating multidrug resistance modulators, and data sharing among countries are required.

Abstract

We aimed to identify the prevalence and emerging status of multidrug-resistant bacteria and fungi and their associated mortality in nine countries in the Arabian Peninsula. Original research articles and case studies regarding multidrug-resistant bacteria and fungi in the Arabian Peninsula, published during the last 10 years, were retrieved from PubMed and Scopus. A total of 382 studies were included as per the inclusion and exclusion criteria, as well as the PRISMA guidelines, from a thorough screening of 1705 articles, in order to analyse the emerging status and mortality. The emerging nature of >120 multidrug-resistant (MDR) bacteria and fungi in the Arabian Peninsula is a serious concern that requires continuous monitoring and immediate preventive measures. More than 50% (n = 453) of multidrug-resistant, microbe-associated mortality (n = 871) in the Arabian Peninsula was due to MDR Acinetobacter baumannii, Mycobacterium tuberculosis and Staphylococcus aureus infection. Overall, a 16.51% mortality was reported among MDR-infected patients in the Arabian Peninsula from the 382 articles of this registered systematic review. MDR A. baumannii (5600 isolates) prevailed in all the nine countries of the Arabian Peninsula and was one of the fastest emerging MDR bacteria with the highest mortality (n = 210). A total of 13,087 Mycobacterium tuberculosis isolates were reported in the region. Candida auris (580 strains) is the most prevalent among the MDR fungal pathogen in the Arabian Peninsula, having caused 54 mortalities. Active surveillance, constant monitoring, the development of a candidate vaccine, an early diagnosis of MDR infection, the elimination of multidrug resistance modulators and uninterrupted preventive measures with enhanced data sharing are mandatory to control MDR infection and associated diseases of the Arabian Peninsula. Accurate and rapid detection methods are needed to differentiate MDR strain from other strains of the species. This review summarises the logical relation, prevalence, emerging status and associated mortality of MDR microbes in the Arabian Peninsula.

In-Vitro Selection of Ceftazidime/Avibactam Resistance in OXA-48-Like-Expressing Klebsiella pneumoniae: In-Vitro and In-Vivo Fitness, Genetic Basis and Activities of β-Lactam Plus Novel β-Lactamase Inhibitor or β-Lactam Enhancer Combinations

Ceftazidime/avibactam uniquely demonstrates activity against both KPC and OXA-48-like carbapenemase-expressing Enterobacterales. Clinical resistance to ceftazidime/avibactam in KPC-producers was foreseen in in-vitro resistance studies. Herein, we assessed the resistance selection propensity of ceftazidime/avibactam in K. pneumoniae expressing OXA-48-like β-lactamases (n = 10), employing serial transfer approach. Ceftazidime/avibactam MICs (0.25–4 mg/L) increased to 16–256 mg/L after 15 daily-sequential transfers. The whole genome sequence analysis of terminal mutants showed modifications in proteins linked to efflux (AcrB/AcrD/EmrA/Mdt), outer membrane permeability (OmpK36) and/or stress response pathways (CpxA/EnvZ/RpoE). In-vitro growth properties of all the ceftazidime/avibactam-selected mutants were comparable to their respective parents and they retained the ability to cause pulmonary infection in neutropenic mice. Against these mutants, we explored the activities of various combinations of β-lactams (ceftazidime or cefepime) with structurally diverse β-lactamase inhibitors or a β-lactam enhancer, zidebactam. Zidebactam, in combination with either cefepime or ceftazidime, overcame ceftazidime/avibactam resistance (MIC range 0.5–8 mg/L), while cefepime/avibactam was the second best (MIC: 0.5–16 mg/L) in yielding lower MICs. The present work revealed the possibility of ceftazidime/avibactam resistance in OXA-48-like K. pneumoniae through mutations in proteins involved in efflux and/or porins without concomitant fitness cost mandating astute monitoring of ceftazidime/avibactam resistance among OXA-48 genotypes.

Stenotrophomonas maltophilia bacteraemia: 61 cases in a tertiary hospital in Denmark

BACKGROUND

Stenotrophomonas maltophilia is an opportunistic pathogen and a dreaded cause of bacteraemia with 30-day mortality rates ranging from 14 to 69%. The purpose of this cohort study was to evaluate outcomes of S. maltophilia bacteraemia, at Rigshospitalet, a tertiary hospital in Copenhagen, Denmark.

METHODS

We included all patients with a blood culture positive for S. maltophilia, from January 1, 2015 to April 1, 2020. We extracted data on antimicrobial susceptibility, treatment, central venous catheter intervention and severe haematological disease.

RESULTS

Sixty-one cases of S. maltophilia bacteraemia were identified. The overall 90-day mortality was 18%. Sixty percent of patients had a central venous catheter intervention performed. Seventy-nine percent of patients were treated with trimethoprim/sulfamethoxazole (TMP/SMX). Patients with central venous catheter intervention had significantly better survival than those without (HR: 0.16 [95% CI: 0.03-0.73]). Severe haematological disease and patients, who received intensive care unit (ICU) care, were at higher risk of death than other patients (HR: 5.93 [95% CI: 1.18 - 29.94] and HR: 8.37 [95% CI: 1.79 - 39.20], respectively). We found no evidence that any antibiotic regime was superior with regard to 90-day mortality.

CONCLUSIONS

We did not find evidence to support a change in the current standard-of-care regimen of TMP/SMX and CVC removal. Larger clinical trials are needed to guide such recommendations.

Epidemiology of Multidrug-Resistant Pseudomonas aeruginosa in the Middle East and North Africa Region

Over the last decades, there has been a dramatic global increase in multidrug-resistant (MDR) pathogens particularly among Gram-negative bacteria (GNB). Pseudomonas aeruginosa is responsible for various health care-associated infections, while MDR P. aeruginosa causes significant morbidity and mortality. Middle East and North Africa (MENA) represent an unexplored geographical region for the study of drug resistance since many of these countries are at crossroads of high volume of travel, diverse expatriate populations, as well as high antibiotic consumption despite attempts to implement antimicrobial stewardship programs. This minireview analyzes epidemiology, microbiological, and genomic characteristics of MDR P. aeruginosa in the MENA region. Published data on MDR P. aeruginosa prevalence, antimicrobial resistance patterns, and genetic profiles from studies published during the past 10 years from 19 MENA countries have been included in this minireview. There is wide variation in the epidemiology of MDR P. aeruginosa in the MENA region in terms of prevalence, antimicrobial characteristics, as well as genetic profiles. Overall, there is high prevalence of MDR P. aeruginosa seen in the majority of the countries in the MENA region with similarities between neighboring countries, which might reflect comparable population and antibiotic-prescribing cultures. Isolates from critical care units are significantly resistant particularly from certain countries such as Saudi Arabia, Egypt, Libya, Syria, and Lebanon with high-level resistance to cephalosporins, carbapenems, and aminoglycosides. Colistin susceptibility patterns remains high apart from countries with high-level antibiotic resistance such as Saudi Arabia, Syria, and Egypt.

Novel Cephalosporins in Septic Subjects and Severe Infections: Present Findings and Future Perspective

In past decade, cephalosporins have developed significantly, and data regarding novel cephalosporins (i.e., ceftobiprole, ceftaroline, ceftolozane/tazobactam, ceftazidime/avibactam, and cefiderocol) within septic and bacteremic subjects are rising. These compounds generally offer very promising in vitro microbiological susceptibility, although the variability among gram-negative and -positive strains of different cohorts is noticed in the literature. We require further pharmacological data to measure the best dose in order to prevent sub-therapeutic drug levels in critically ill patients. These new compounds in theory are the sparing solution in the Enterobacteriales infection group for different antimicrobial classes such as aminoglycosides notably within endovascular and GNB-bacteremias, as well as colistin and carbapenem-sparing strategies, favoring good safety profile molecules. Moreover, new cephalosporins are the basis for the actual indications to open up new and exciting prospects for serious infections in the future. In future, patients will be addressed with the desirable approach to sepsis and serious infections in terms of their clinical situation, inherent features of the host, the sensitivity profile, and local epidemiology, for which evidence of the use of new cephalosporin in the treatment of severe infections will fill the remaining gaps.

Nosocomial Pneumonia in the Era of Multidrug-Resistance: Updates in Diagnosis and Management

Nosocomial pneumonia (NP), including hospital-acquired pneumonia in non-intubated patients and ventilator-associated pneumonia, is one of the most frequent hospital-acquired infections, especially in the intensive care unit. NP has a significant impact on morbidity, mortality and health care costs, especially when the implicated pathogens are multidrug-resistant ones. This narrative review aims to critically review what is new in the field of NP, specifically, diagnosis and antibiotic treatment. Regarding novel imaging modalities, the current role of lung ultrasound and low radiation computed tomography are discussed, while regarding etiological diagnosis, recent developments in rapid microbiological confirmation, such as syndromic rapid multiplex Polymerase Chain Reaction panels are presented and compared with conventional cultures. Additionally, the volatile compounds/electronic nose, a promising diagnostic tool for the future is briefly presented. With respect to NP management, antibiotics approved for the indication of NP during the last decade are discussed, namely, ceftobiprole medocaril, telavancin, ceftolozane/tazobactam, ceftazidime/avibactam, and meropenem/vaborbactam.

Comparative in vitro effectiveness of ceftolozane/tazobactam against pediatric gram-negative drug-resistant isolates

Ceftolozane/tazobactam (C/T), a cephalosporin/beta-lactamase inhibitor combination, was evaluated in vitro vs. 10 comparators against 299 pediatric extended-spectrum-cephalosporin-resistant or carbapenem-resistant (ESC-R/CR) Gram-negative Enterobacteriaceae from three freestanding pediatric centers. Isolates were from urine or other sterile sites of children and adolescents through 21 years of age. Susceptibilities were assayed by microbroth dilution via custom Sensititre plates (Thermo Fisher Scientific). Susceptibility was determined using the Sensititre Vizion® system (Thermo Fisher Scientific). Susceptibility breakpoint criteria were those of the Clinical and Laboratory Standards Institute (CLSI) for 2017, except for colistin (EUCAST 2019). Overall, 87.5% isolates were C/T susceptible (MIC ≤2 μg/ml; MIC_50/90, 0.25/4 μg/ml). Susceptibility to C/T was detected more frequently as compared to all other antimicrobials tested except for colistin (95.4%) and meropenem (97.4%). Percent susceptibility to C/T was high for E. coli (91%) and Klebsiella spp. (73.3%). C/T demonstrated good in-vitro activity and high potency against most beta-lactam resistant pediatric Enterobacteriaceae from three geographically diverse U.S. regions.

In vitro and in vivo antibacterial activity assays of carvacrol: A candidate for development of innovative treatments against KPC-producing Klebsiella pneumoniae

Dissemination of carbapenem-resistant Klebsiella pneumoniae poses a threat to the successful treatment of bacterial diseases and increases the need for new antibacterial agents development. The objective of this study was to determine the antimicrobial activity of carvacrol against multidrug-resistant K. pneumoniae. Carbapenemase production was detected by MALDI-TOF. The PCR and sequencing showed that the bla_KPC-2,bla_OXA-48, bla_NDM-1, bla_CTX-M-8 genes were present in carbapenem-resistant K. pneumoniae strains. The polymyxin-resistant K. pneumoniae strain exhibited alterations in mgrB gene. The antimicrobial activity of carvacrol was evaluated in vitro using broth microdilution and time-kill methods. For this, carbapenem-resistant K. pneumoniae and polymyxin-resistant strains, were evaluated. The in vitro results showed that carvacrol had antimicrobial activity against all isolates evaluated. The survival curves showed that carvacrol eradicated all of the bacterial cells within 4 h. The antimicrobial effect of carvacrol in vivo was determined using a mouse model of infection with Klebsiella pneumoniae carbapenemase (KPC). The treatment with carvacrol was associated with increased survival, and significantly reduced bacterial load in peritoneal lavage. In addition, groups treated with carvacrol, had a significant reduction in the total numbers of white cell and significantly increased of platelets when compared to the untreated group. In vivo and in vitro studies showed that carvacrol regimens exhibited significant antimicrobial activity against KPC-producing K. pneumoniae, making it an interesting candidate for development of alternative treatments.

High incidence of MDR and XDR Pseudomonas aeruginosa isolates obtained from patients with ventilator-associated pneumonia in Greece, Italy and Spain as part of the MagicBullet clinical trial

OBJECTIVES

To characterize the antimicrobial susceptibility, molecular epidemiology and carbapenem resistance mechanisms in Pseudomonas aeruginosa isolates recovered from respiratory tract samples from patients with ventilator-associated pneumonia enrolled in the MagicBullet clinical trial.

METHODS

Isolates were collected from 53 patients from 12 hospitals in Spain, Italy and Greece. Susceptibility was determined using broth microdilution and Etest. MALDI-TOF MS was used to detect carbapenemase activity and carbapenemases were identified by PCR and sequencing. Molecular epidemiology was investigated using PFGE and MLST.

RESULTS

Of the 53 isolates, 2 (3.8%) were considered pandrug resistant (PDR), 19 (35.8%) were XDR and 16 (30.2%) were MDR. Most (88.9%) of the isolates from Greece were MDR, XDR or PDR, whereas fewer of the isolates from Spain (33.3%) and Italy (43.5%) showed antibiotic resistance. Three Greek isolates were resistant to colistin. Overall, the rates of resistance of P. aeruginosa isolates to imipenem, ciprofloxacin, ceftolozane/tazobactam and ceftazidime/avibactam were 64.1%, 54.7%, 22.6% and 24.5%, respectively. All isolates resistant to ceftolozane/tazobactam and ceftazidime/avibactam (Greece, n = 10; and Italy, n = 2) carried blaVIM-2. Spanish isolates were susceptible to the new drug combinations. Forty-eight restriction patterns and 27 STs were documented. Sixty percent of isolates belonged to six STs, including the high-risk clones ST-111, ST-175 and ST-235.

CONCLUSIONS

MDR/XDR isolates were highly prevalent, particularly in Greece. The most effective antibiotic against P. aeruginosa was colistin, followed by ceftolozane/tazobactam and ceftazidime/avibactam. blaVIM-2 is associated with resistance to ceftolozane/tazobactam and ceftazidime/avibactam, and related to highly resistant phenotypes. ST-111 was the most frequent and disseminated clone and the clonal diversity was lower in XDR and PDR strains.

A rare emergence of resistance to ceftolozane/tazobactam in Klebsiella pneumoniae causing urinary tract infection

The management of infections caused by carbapenem-resistant organisms has been a challenge. We report a rare emergence of resistance to the novel beta-lactam/ beta-lactamase combination ceftolozane/tazobactam by Klebsiella pneumoniae, causing urinary tract infection. The K. pneumoniae, in this case, was reported to be sensitive to the other novel beta-lactam/ beta-lactamase combination of ceftazidime/avibactam. The timely administration of ceftazidime/avibactam resulted in prompt clinical resolution of the urinary tract infection caused by an extensively drug-resistant K. pneumoniae.

Rare Multidrug-resistant Pseudomonas aeruginosa Identified in a U.S. Deployed Service Member Following Host-nation Medical Treatment

Decision-making related to the utilization of host-nation medical resources in austere forward-deployed environments is complex. Clinical circumstances, local medical intelligence availability, transportation assets, uncertainty regarding standard-of-care variations, military/host-nation funding complications, and regional security concerns all factor into consideration. A case of a U.S. active duty military service member who suffered a cardiac arrest on a military base in Southwest Asia is described in this report. After return of circulation following defibrillation, he was administered thrombolytic therapy for an electrocardiogram-identified ST-elevation myocardial infarction and transported to a local host-nation cardiac hospital for emergent percutaneous coronary intervention. During his subsequent transportation back to the USA, surveillance testing identified that he was colonized with a rare strain of Pseudomonas aeruginosa, demonstrating New Delhi metallo-beta-lactamase-1 and 16S RNA methyltransferase-2 enzymes, which confer significant resistance to carbapenem and aminoglycoside antibiotics, respectively.1-3 This combination of antibiotic resistance has been reported very rarely in the medical literature and has never been reported within the deployed military health system until now. The risk of exposure to multidrug-resistant organisms was not a factor initially considered in the decision to utilize host-nation medical resources in this case, which provided lesson learned and raised new questions, for future operational medical planning.

New β-Lactam-β-Lactamase Inhibitor Combinations

The limited armamentarium against drug-resistant Gram-negative bacilli has led to the development of several novel β-lactam-β-lactamase inhibitor combinations (BLBLIs). In this review, we summarize their spectrum of in vitro activities, mechanisms of resistance, and pharmacokinetic-pharmacodynamic (PK-PD) characteristics. A summary of available clinical data is provided per drug. Four approved BLBLIs are discussed in detail. All are options for treating multidrug-resistant (MDR) Enterobacterales and Pseudomonas aeruginosa Ceftazidime-avibactam is a potential drug for treating Enterobacterales producing extended-spectrum β-lactamase (ESBL), Klebsiella pneumoniae carbapenemase (KPC), AmpC, and some class D β-lactamases (OXA-48) in addition to carbapenem-resistant Pseudomonas aeruginosa Ceftolozane-tazobactam is a treatment option mainly for carbapenem-resistant P. aeruginosa (non-carbapenemase producing), with some activity against ESBL-producing Enterobacterales Meropenem-vaborbactam has emerged as treatment option for Enterobacterales producing ESBL, KPC, or AmpC, with similar activity as meropenem against P. aeruginosa Imipenem-relebactam has documented activity against Enterobacterales producing ESBL, KPC, and AmpC, with the combination having some additional activity against P. aeruginosa relative to imipenem. None of these drugs present in vitro activity against Enterobacterales or P. aeruginosa producing metallo-β-lactamase (MBL) or against carbapenemase-producing Acinetobacter baumannii Clinical data regarding the use of these drugs to treat MDR bacteria are limited and rely mostly on nonrandomized studies. An overview on eight BLBLIs in development is also provided. These drugs provide various levels of in vitro coverage of carbapenem-resistant Enterobacterales, with several drugs presenting in vitro activity against MBLs (cefepime-zidebactam, aztreonam-avibactam, meropenem-nacubactam, and cefepime-taniborbactam). Among these drugs, some also present in vitro activity against carbapenem-resistant P. aeruginosa (cefepime-zidebactam and cefepime-taniborbactam) and A. baumannii (cefepime-zidebactam and sulbactam-durlobactam).

Evaluation of in vitro activity of ceftazidime/avibactam and ceftolozane/tazobactam against MDR Pseudomonas aeruginosa isolates from Qatar

OBJECTIVES

To investigate the in vitro activity of ceftazidime/avibactam and ceftolozane/tazobactam against clinical isolates of MDR Pseudomonas aeruginosa from Qatar, as well as the mechanisms of resistance.

METHODS

MDR P. aeruginosa isolated between October 2014 and September 2015 from all public hospitals in Qatar were included. The BD PhoenixTM system was used for identification and initial antimicrobial susceptibility testing, while Liofilchem MIC Test Strips (Liofilchem, Roseto degli Abruzzi, Italy) were used for confirmation of ceftazidime/avibactam and ceftolozane/tazobactam susceptibility. Ten ceftazidime/avibactam- and/or ceftolozane/tazobactam-resistant isolates were randomly selected for WGS.

RESULTS

A total of 205 MDR P. aeruginosa isolates were included. Of these, 141 (68.8%) were susceptible to ceftazidime/avibactam, 129 (62.9%) were susceptible to ceftolozane/tazobactam, 121 (59.0%) were susceptible to both and 56 (27.3%) were susceptible to neither. Twenty (9.8%) isolates were susceptible to ceftazidime/avibactam but not to ceftolozane/tazobactam and only 8 (3.9%) were susceptible to ceftolozane/tazobactam but not to ceftazidime/avibactam. Less than 50% of XDR isolates were susceptible to ceftazidime/avibactam or ceftolozane/tazobactam. The 10 sequenced isolates belonged to six different STs and all produced AmpC and OXA enzymes; 5 (50%) produced ESBL and 4 (40%) produced VIM enzymes.

CONCLUSIONS

MDR P. aeruginosa susceptibility rates to ceftazidime/avibactam and ceftolozane/tazobactam were higher than those to all existing antipseudomonal agents, except colistin, but were less than 50% in extremely resistant isolates. Non-susceptibility to ceftazidime/avibactam and ceftolozane/tazobactam was largely due to the production of ESBL and VIM enzymes. Ceftazidime/avibactam and ceftolozane/tazobactam are possible options for some patients with MDR P. aeruginosa in Qatar.

Treatment of Bloodstream Infections Due to Gram-Negative Bacteria with Difficult-to-Treat Resistance

The rising incidence of bloodstream infections (BSI) due to Gram-negative bacteria (GNB) with difficult-to-treat resistance (DTR) has been recognized as a global emergency. The aim of this review is to provide a comprehensive assessment of the mechanisms of antibiotic resistance, epidemiology and treatment options for BSI caused by GNB with DTR, namely extended-spectrum Beta-lactamase-producing Enterobacteriales; carbapenem-resistant Enterobacteriales; DTR Pseudomonas aeruginosa; and DTR Acinetobacter baumannii.

In vitro efficacy of ceftazidime-avibactam, aztreonam-avibactam and other rescue antibiotics against carbapenem-resistant Enterobacterales from the Arabian Peninsula

OBJECTIVES

Our aim was to assess the susceptibility of carbapenem-resistant Enterobacterales (CRE) from the Arabian Peninsula to a broad spectrum of antibiotics, including fosfomycin, ceftazidime-avibactam, and aztreonam-avibactam.

METHODS

1192 non-repeat CRE isolated in 2009-2017 from 33 hospitals in five countries of the Arabian Peninsula were tested. The minimum inhibitory concentration of 14 antibiotics was determined. Carbapenemase and 16S methylase genes were detected by PCR. Clonality was assessed by PFGE.

RESULTS

The highest rate of susceptibility was detected to aztreonam-avibactam (95.5%) followed by colistin (79.8%), fosfomycin (71.8%) and tigecycline (59.9%). Isolates co-producing two carbapenemases (12.4%) were the least susceptible. Aminoglycoside susceptibility was affected by the frequent production of a 16S methylase. Susceptibility to ceftazidime-avibactam was impacted by the high rate of metallo-beta-lactamase producers (46.3%), while aztreonam-avibactam resistance occurred mostly in clonally unrelated, carbapenemase non-producing Escherichia coli.

CONCLUSION

Of the currently available drugs: colistin, tigecycline, and ceftazidime-avibactam co-administered with aztreonam appear to be the most effective to treat CRE infections. However, the presence of non-clonal CRE isolates, in which avibactam does not lower the aztreonam MIC below the clinical breakpoint, is of notable concern. Based on the relatively high rate of fosfomycin susceptibility, it would be desirable to license parenteral fosfomycin in the region.

New cephalosporins for the treatment of pneumonia in internal medicine wards

The burden of hospital admission for pneumonia in internal medicine wards may not be underestimated; otherwise, cases of pneumonia are a frequent indication for antimicrobial prescriptions. Community- and hospital-acquired pneumonia are characterized by high healthcare costs, morbidity and non-negligible rates of fatality. The overcoming prevalence of resistant gram-negative and positive bacteria (e.g., methicillin-resistant Staphylococcus aureus, penicillin and ceftriaxone-resistant Streptococcus pneumoniae, extended-spectrum β-lactamases and carbapenemases producing Enterobacteriaceae) has made the most of the first-line agents ineffective for treating lower respiratory tract infections. A broad-spectrum of activity, favourable pulmonary penetration, harmlessness and avoiding in some cases a combination therapy, characterise new cephalosporins such as ceftolozane/tazobactam, ceftobiprole, ceftazidime/avibactam and ceftaroline. We aimed to summarise the role and place in therapy of new cephalosporins in community- and hospital-acquired pneumonia within the setting of internal medicine wards. The “universal pneumonia antibiotic strategy” is no longer acceptable for treating lung infections. Antimicrobial therapy should be individualized considering local antimicrobial resistance and epidemiology, the stage of the illness and potential host factors predisposing to a high risk for specific pathogens.

Drugs for Gram-Negative Bugs From 2010-2019: A Decade in Review

A literature review spanning January 1, 2010, to December 31, 2019, was conducted using the PubMed and ISI Web of Science databases to determine the breadth of publication activity in the area of gram-negative bacteria antimicrobial therapy. The number of articles was used as a reflection of scholarly activity. First, PubMed was searched using the following Medical Subject Headings (MeSH): antibacterial agents, Enterobacteriaceae, Acinetobacter, and Pseudomonas. A total of 12 643 articles were identified within PubMed, and 77 862 articles were identified within ISI Web of Science that included these terms. Second, these articles were categorized by antibiotic class to identify relative contributions to the literature by drug category. Third, these studies were used to identify key trends in the treatment of gram-negative bacterial infections from the past decade. This review highlights advances made in the past 10 years in antibacterial pharmacotherapy and some of the challenges that await the next decade of practice.

In Vitro Synergistic Effect and Mutant Prevention Concentrations of Cefepime Alone or in Combination with Sulbactam Against OXA-48-positive Klebsiella pneumoniae Isolates

The aim of this study is to investigate the combination of cefepime and sulbactam. Sulbactam, when administered , will effectively inhibit all Extended-spectrum beta lactamases (ESBLs) of the microorganism, while cefepime will inhibit the growth of the resistant microorganisms since it will not be hydrolyzed by OXA-48. Forty OXA-48-producing K. pneumoniae strains were investigated for their Minimum inhibitory concentrations (MICs) for carbapenems, cefepime, and cefepime + sulbactam by broth microdilution method. Also, the mutant prevention concentration (MPC)s of cefepime alone or in combination with sulbactam was determined. Additionally, the bactericidal activities of cefepime and cefepime + sulbactam were evaluated by the time-kill curve (TKC) assay against selected strains. Also, the in vitro synergistic activity of cefepime + sulbactam combination was determined by TKC. Based on MIC results, up to 35/40 and 34/40 of the strains were resistant to carbapenems and cefepime, respectively. Cefepime + sulbactam MIC range was lower than those for cefepime alone against all the studied isolates. Moreover, cefepime + sulbactam combination presented lower MPC values than cefepime alone. The synergistic interactions of cefepime + sulbactam were also achieved against studied strains at 24 h. No antagonism was observed against studied K. pneumoniae strains. The findings of this study displayed that cefepime + sulbactam combination had synergistic or additive effect against OXA-48-producing K. pneumoniae strains. Additionally, it was first observed that this combination could display a lower MPC than cefepime alone. Further investigations may be helpful for understanding the effectiveness of cefepime + sulbactam combinations for OXA-48-positive carbapenem-resistant K. pneumoniae isolates.

Synergistic activities of ceftazidime-avibactam in combination with different antibiotics against colistin-nonsusceptible clinical strains of Pseudomonas aeruginosa

Background: This study aims to analyse the effect of ceftazidime-avibactam plus various antibiotics against multidrug-resistant (MDR) Pseudomonas aeruginosa isolated from Intensive Care Units.Methods: 40 non-duplicate P. aeruginosa isolates were screened for their MICs of ceftazidime, ceftazidime-avibactam, colistin, levofloxacin, doripenem and tobramycin. MICs were determined by the broth microdilution method. The in vitro bactericidal activities of ceftazidime-avibactam compared to studied antibiotics were also determined by time-kill curve assays both at 1xMIC and at 4xMIC against carbapenemase-producing or -not producing six colistin-nonsusceptible MDR clinical strains of P. aeruginosa. Additionally, synergistic interactions were investigated by the time-kill curve assay.Results: The MIC₉₀ values for ceftazidime, ceftazidime-avibactam, colistin, levofloxacin, doripenem and tobramycin against MDR P. aeruginosa isolates were found to be >256, 64, 8, 64, 128, and >256 mg/L, respectively. The minimum bactericidal concentration₉₀ values for those antibiotics were also >256, 64, 16, 128, 256, and >256 mg/L, respectively. While doripenem, tobramycin and levofloxacin were bactericidal (>3 log₁₀ killing) against the 2/6, 3/6 and 1/6 P. aeruginosa isolates at 4xMIC concentrations, respectively, levofloxacin and tobramycin were bactericidal against only one isolate (1/6) at 1xMIC concentrations at 24 h. The synergistic interactions of these antimicrobial agents were also achieved with ceftazidime/avibactam + colistin (4/6), ceftazidime/avibactam + tobramycin (3/6), and ceftazidime/avibactam + levofloxacin (3/6) combinations. No antagonism was observed against studied P. aeruginosa strains.Conclusions: The findings of this study suggest that ceftazidime/avibactam with colistin, or tobramycin, were effective against colistin-nonsusceptible strains. This combination therapy could be an alternative antibiotic therapy for resistant P. aeruginosa strains.

First Study of Antimicrobial Activity of Ceftazidime-Avibactam and Ceftolozane-Tazobactam Against Pseudomonas aeruginosa Isolated from Patients with Urinary Tract Infection in Tehran, Iran

Purpose

Pseudomonas aeruginosa causes complicated and/or nosocomial UTI. These infections are usually associated with severe and multi-drug resistant P. aeruginosa isolates. As there is no study about the activity of novel antibiotics ceftazidime-avibactam (CZA) and ceftolozane-tazobactam (C/T) against P. aeruginosa isolates in Iran, we aimed to evaluate for the first time the efficacy of these agents against P. aeruginosa isolated from patients with UTI in Iran. Then, the genetic diversity of the resistant isolates was assayed.

Methods

In this study, a total of 200 P. aeruginosa isolates were collected from patients with UTI in Tehran, Iran. Disk diffusion and Minimum Inhibitory Concentration (MIC) methods were applied to determine the resistance of the isolates to CZA, C/T, and the other antibiotics. Extended-spectrum β-lactamases (ESBLs) and Metallo Beta Lactamase (MBL) production were assayed by Combination disk diffusion test (CDDT). Polymerase chain reaction (PCR) was carried out to detect the resistance genes, including beta-lactamases and carbapenemases genes. Finally, genomic analysis of the isolates was performed using the Pulse field gel electrophoresis (PFGE).

Results

Among the isolates, 16 (8%) were resistant to CZA and C/T that MIC confirmed it. The resistant isolates showed high resistance to the other classes of antibiotics. Among the resistant isolates, 31.2% and 75% were ESBL and MBL producers, respectively. The prevalence of bla_OXA10, bla_VIM, bla_OXA48, bla_OXA2, and bla_CTX-M was 100%, 50%, 31.2%, 25%, and 12.5%. Furthermore, two isolates (12.5%) harbored bla_PER and bla_NDM genes. The resistant isolates were grouped into 14 distinct pulsotypes and two shared pulsotypes were found.

Conclusion

Ceftazidime-avibactam and ceftolozane-tazobactam showed high activity against the P. aeruginosa isolated from patients with UTI in Iran. The low rate of resistance to the antibiotics is also alarming and should be considered to avoid further spreading of the antibiotic resistance among the P. aeruginosa and the other bacteria.

Clinical outcomes of ceftazidime-avibactam in lung transplant recipients with infections caused by extensively drug-resistant gram-negative bacilli

Background

Infections produced by extensively drug-resistant (XDR) gram-negative bacilli (GNB) in solid organ transplant (SOT) are an important cause of morbidity and mortality. Ceftazidime/avibactam (CAZ-AVI) is a novel β-lactam/β-lactamase combination antibiotic with anti-GNB activity, but experience in real clinical practice with CAZ-AVI in lung transplant (LT) recipients is limited.

Methods

We conducted a retrospective study of patients with XDR-GNB infection who received at least 3 days of CAZ-AVI in the Department of Lung Transplantation Between December 2017 and December 2018 at China-Japan friendship hospital (CJFH). The general information, clinical manifestations, laboratory examinations, treatment course, and outcomes were summarized.

Results

A total of 10 patients who underwent LT at our center were included. They were all males with a mean age 51 years. Infections after LT included pneumonia and/or tracheobronchitis [n=9; 90% (9/10)], cholecystitis and blood stream infection (BSI) (n=1, patient 8). In these 10 LT recipients, the incidence of various airway complications was 70% (7/10). Carbapenem-resistant Klebsialla pneumoniae (CRKP) was the predominant pathogen, being detected in 9 patients. Multilocus sequence typing (MLST) analysis showed that all 9 CRKP isolates belonged to ST11. Six patients (6/10, 60%) started CAZ-AVI as salvage therapy after a first-line treatment with other antimicrobials. CAZ-AVI was administered as monotherapy or in combination regimens in 20% (2/10) and 80% (8/10) of patients respectively. There were no difference in temperature before and after CAZ-AVI treatment (P>0.05). White blood cell (WBC) at 7 days, and procalcitonin (PCT) at 7 days and 14 days significantly dropped (P<0.05). After 7-14 days of CAZ-AVI treatment, the PaO₂/FiO₂ratio (P/F ratio) significantly improved (P<0.05). Nine patients (9/10, 90%) obtained negative microbiologic culture of CRKP/CRPA, with a median time to was 6.7 days (range, 1-15 days). However, 5 patients (5/10, 50%) had relapse of CRKP/CRPA infections in the respiratory tract regardless of whether negative microbiologic culture was obtained or not. The 30-day survival rate was 100%, and the 90-day survival rate was 90% (1/10). No severe adverse events related to CAZ-AVI occurred.

Conclusions

CAZ-AVI treatment of CRKP/ CRPA infection in LT recipients was associated with high rates of clinical success, survival, and safety, but recurrent CRKP/CRPA infections in the respiratory tract did occur.

Ceftolozane-tazobactam- and ceftazidime-avibactam-resistant Pseudomonas aeruginosa mastoiditis

Pseudomonas aeruginosa is an important bacterial cause of a variety of infections and is associated with high morbidity and mortality. Infections caused by this bacterium are becoming more difficult to treat due to increasing resistance to many of the available antibiotics. Ceftolozane–tazobactam and ceftazidime–avibactam are two new cephalosporin/β-lactamase inhibitor combination antimicrobials that have demonstrated excellent in vitro activity against several multi-drug-resistant pathogens, including multi-drug-resistant P. aeruginosa. Cases of infections with isolates of multi-drug-resistant P. aeruginosa that are resistant to both of these antimicrobials have rarely been reported. We report a case of mastoiditis caused by P. aeruginosa that was resistant to both ceftolozane–tazobactam and ceftazidime–avibactam.

Considerations and Caveats in Combating ESKAPE Pathogens against Nosocomial Infections

ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are among the most common opportunistic pathogens in nosocomial infections. ESKAPE pathogens distinguish themselves from normal ones by developing a high level of antibiotic resistance that involves multiple mechanisms. Contemporary therapeutic strategies which are potential options in combating ESKAPE bacteria need further investigation. Herein, a broad overview of the antimicrobial research on ESKAPE pathogens over the past five years is provided with prospective clinical applications.

In vitro activity of ceftolozane-tazobactam and ceftazidime-avibactam against clinical isolates of meropenem-non-susceptible Pseudomonas aeruginosa: A two-centre study

OBJECTIVES

This study aimed to compare the activity of ceftazidime-avibactam (C/A), ceftolozane-tazobactam (C/T) and three anti-pseudomonal β-lactams (piperacillin-tazobactam, ceftazidime and cefepime) against a collection of meropenem-non-susceptible Pseudomonas aeruginosa (P. aeruginosa) clinical isolates recovered from two centres in Turkey.

METHODS

A total of 102 unique patient isolates of meropenem-non-susceptible P. aeruginosa were included in the study. MICs of antimicrobials were determined by the gradient diffusion method.

RESULTS

Overall susceptibility rates for C/A and C/T were 83.3% and 82.4%, respectively. Both C/A and C/T had better activity than any one of the three anti-pseudomonal β-lactams. According to the MIC₅₀ values, C/T was the most potent agent against isolates. Although the susceptibility rates of isolates to C/T and C/A were similar, C/T (MIC₅₀, 1 μg/mL) was four-fold more potent than C/A (MIC₅₀, 4 μg/mL). The MIC₅₀ values of C/A and C/T for the isolates that were non-susceptible to three β-lactams were significantly higher than those for isolates that were non-susceptible to zero, one or two β-lactams. Also, the C/A MIC₅₀ value for the isolates that were non-susceptible to two β-lactams was higher than that for isolates which were non-susceptible to one β-lactam.

CONCLUSIONS

C/A and C/T showed good activity against meropenem-non-susceptible P. aeruginosa isolates. However, resistance to these agents was not uncommon among these isolates. The overall β-lactam susceptibility profile of isolates seems to have an effect on the probability of susceptibility to C/A and C/T. Antimicrobial susceptibility testing should be performed for C/A and C/T if these agents are considered for treatment of infections caused by meropenem-non-susceptible P. aeruginosa.

Longitudinal analysis of the in vitro activity of ceftazidime/avibactam versus Enterobacteriaceae, 2012-2016

OBJECTIVES

The in vitro activities of ceftazidime/avibactam and comparator antimicrobial agents were analysed against 59 828 Enterobacteriaceae isolates collected by 190 centres from all global regions except North America from 2012-2016 as part of the International Network for Optimal Resistance Monitoring (INFORM) global surveillance programme.

METHODS

Antimicrobial susceptibility testing was performed using Clinical and Laboratory Standards Institute broth microdilution panels at a central reference laboratory, except for isolates collected in China that were tested using frozen, dehydrated broth microdilution panels at a central laboratory in China. The presence of extended-spectrum β-lactamases (ESBLs) was confirmed by multiplex PCR assays.

RESULTS

Ceftazidime/avibactam was the most active agent against all Enterobacteriaceae (MIC₉₀, ≤1mg/L, ≥98.4% susceptibility). High rates of susceptibility (>88%) were observed amongst Citrobacter freundii, Citrobacter spp., Enterobacter spp., Escherichia coli, Klebsiella pneumoniae and Klebsiella oxytoca to colistin, meropenem, amikacin and tigecycline. Ceftazidime/avibactam showed consistent in vitro activity against ESBL-positive isolates of E. coli (n=5674; MIC₉₀, 0.5mg/L, 99.5% susceptible), K. pneumoniae (n=7097; MIC₉₀, 2mg/L, 97.0% susceptible) and K. oxytoca (n = 565; MIC₉₀, 1mg/L, 96.8% susceptible). Isolates identified as metallo-β-lactamase-positive (n=242) were not susceptible to ceftazidime/avibactam but were susceptible to tigecycline (76.9%) and colistin (n=194 isolates tested; 92.8%).

CONCLUSIONS

Clinical Enterobacteriaceae isolates, including ESBL-positive phenotypes, collected globally (excluding North America) from 2012-2016 were highly susceptible to ceftazidime/avibactam, suggesting it is a useful agent for serious infections caused by multidrug-resistant organisms belonging to the family Enterobacteriaceae when therapeutic options are limited.