Infectious Diseases Society of America 2022 Guidance on the Treatment of Extended-Spectrum β-lactamase Producing Enterobacterales (ESBL-E), Carbapenem-Resistant Enterobacterales (CRE), and Pseudomonas aeruginosa with Difficult-to-Treat Resistance (DTR-P. aeruginosa)

Targeting bacterial efflux pump effectively enhances the efficacy of Ru-based antibacterial agents against Gram-negative pathogen

The rise of antibiotic resistance has posed a great threat to human's life, thus develop novel antibacterial agents is urgently needed. It worthies to noted that Ru-based antibacterial agents often showed robust potency against Gram-positive pathogens, disrupted bacterial membrane and avoided bacterial resistance, making they promising antibiotic candidates. However, they are generally less active when applied to negative pathogens. To address this problem, a Ru-based metalloantibiotic (RuN) modified with a nitrothiophene moiety, which can target bacterial efflux pump, was designed and evaluated in this work. A series of assays demonstrated that RuN not only fully retained the advantages of Ru-based agents, such as destroyed bacterial membrane and induced reactive oxygen species production, but also can targeted bacterial efflux pumps. Of course, these properties make it effective in killing both Gram-positive and negative pathogens, its MIC values against Staphylococcus aureus and Escherichia coli lies at 3.125 and 6.25 μg/mL, respectively. Importantly, RuN also showed low toxicity and has robust anti-infective potency in two animal infection models. Together, our results paved an alternative way to enhance the anti-infective efficacy of Ru-based agents against resistant negative bacteria.

Risk factors and molecular epidemiology of colonizing carbapenem-resistant Enterobacterales in pediatric inpatient in Shenzhen, China

OBJECTIVES

The spread of CRE has been rapid on a global scale and represents a significant challenge in nosocomial infections worldwide. The aim is to evaluate the risk factors for CRE colonization and to describe the molecular and clinical characteristics of CRE colonization in pediatric inpatients in Shenzhen, China.

METHODS

We collected stool specimens from 2474 randomly selected pediatric inpatient hospitalized in 2 pediatric hospitals in Shenzhen between January 2023 and December 2023 for subsequent microbiological analysis, including microbial culture, species identification, antimicrobial sensitivity testing, genetic characterization and multilocus sequence typing (MLST). In addition, we conducted a case-control study to identify potential risk factors for gastrointestinal CRE colonization.

RESULTS

Of the 2474 non-replicating pediatric stool specimens collected, 3.6 % (n = 90) test positive for CRE. The most dominant CRE species were Escherichia coli (n = 67, 74.5 %), and Klebsiella pneumoniae (n = 17, 19.0 %). Multidrug resistance and carbapenemase production were observed in most CRE isolates. In CR E. coli and CR K. pneumoniae, the blaNDM was the predominant resistance gene, accounting for 95.5 % and 76.5 %, respectively. MLST showed considerable clonal diversity among the CR E. coli and CR K. pneumoniae isolates and the most common ST in CR E. coli was ST48 (n = 6, 9.0 %) and ST35 in CR K. pneumoniae (n = 4, 23.5 %).

CONCLUSIONS

This study once again shows that pediatric inpatients in South China were colonized by a diversity of CRE strains, increasing the likelihood of difficult-to-treat infections. Hospitals and competent authorities should take appropriate public health measures, to prevent the further spread of CRE.

Efficacy and Safety of Aerosol Inhalation of Colistin Sulfate for the Treatment of Carbapenem-Resistant Klebsiella pneumoniae Infection in the Peri-Operative Period of Liver Transplantation: A Single-Center Retrospective Study

Objective: This study intended to evaluate the clinical efficacy and safety of colistin sulfate aerosol inhalation in combination with ceftazidime-avibactam for the treatment of pulmonary carbapenem-resistant Klebsiella pneumoniae (CRKP) infection during the peri-operative period of liver transplantation. Materials and Methods: A retrospective analysis was designed to investigate 52 patients who developed pulmonary CRKP infection after liver transplantation between December 1, 2019, and November 30, 2022. On the basis of whether they received colistin sulfate aerosol inhalation, the patients were divided into the treatment group (n = 29) and the control group (n = 23). The baseline information, infection status, CRKP enzyme type, inflammatory markers, liver and kidney function, and prognosis were compared and analyzed. Results: There were no significant differences in patient characteristics, infection status, and drug resistance enzyme type between the treatment group (treated with colistin sulfate aerosol inhalation and ceftazidime and avibactam sodium for injection) and the control group (treated with ceftazidime and avibactam sodium for injection alone). Colistin sulfate aerosol inhalation treatment reduced concentrations of inflammatory markers, with post-treatment white blood cell count, procalcitonin, and C-reactive protein significantly lower than pre-treatment levels (p < 0.05). Except for C-reactive protein at 14 days (p = 0.032), the two groups had no significant differences in other indicators. There were no significant differences in alanine aminotransferase, aspartate aminotransferase, total bilirubin, and glomerular filtration rate after treatment, indicating no discernible alteration in liver and kidney function. In addition, the treatment group took a significantly shorter time to normalize body temperature compared with the control group (p = 0.025), but there were no significant differences in the cure with no colonization rate and all-cause mortality rate between the two groups. Conclusions: The combination of colistin sulfate aerosol inhalation and ceftazidime and avibactam sodium for injection is effective in treating pulmonary CRKP infection during the peri-operative period of liver transplantation. It does not impose an additional burden on liver and kidney function, providing a new treatment option for this type of infection.

Switch to amoxicillin-clavulanate oral therapy in urinary tract infection caused by extended-spectrum beta-lactamase-producing Escherichia coli: Assessment by chronic phase technetium-99m dimercaptosuccinic acid renal Scintigraphy images

The incidence of urinary tract infection (UTI) caused by extensive beta-lactamase-producing Escherichia coli (ESBL-EC) is increasing, including in children. However, the available oral antibiotic treatment options for ESBL-EC are limited. Herein, we report the cases of two children diagnosed with UTI caused by ESBL-EC (ESBL-UTI) who were switched from empirical intravenous antibiotics in UTI to amoxicillin-clavulanic acid (AMPC/CVA) (14:1) after the causative organism was found to be ESBL-EC. A 3-month-old infant and an 8-month-old infant were admitted to our hospital with the chief complaint of fever. In both cases, UTI was suspected based on urinalysis results, and intravenous cefotaxime was started as an empiric antibiotic. In both cases, ESBL-EC was detected in urine culture, and the diagnosis of ESBL-UTI was confirmed. Results of antimicrobial susceptibility testing showed resistance to cefotaxime, but fever resolution was obtained in both cases following administration of intravenous cefotaxime. Since fever resolution was achieved, the antimicrobial was switched to oral AMPC/CVA (14:1) monotherapy with reference to antimicrobial susceptibility testing, and the two patients were discharged on days 5-6 of hospitalization. Antimicrobials were administered intravenously and orally for a total of 2 weeks. Chronic-phase technetium-99m dimercaptosuccinic acid renal scintigraphy showed no renal scarring. ESBL-UTI may require 2 weeks of intravenous antibacterial therapy, but in this case, both patients could be treated without renal scarring after conversion to oral AMPC/CVA alone. Since this is important to shorten the length of hospital stay, we will study the effect of this treatment modality in more cases in the future.

The in vitro Activity of Omadacycline Alone and in Combination Against Carbapenem-Resistant Klebsiella pneumoniae

Objective

This study aimed to evaluate the in vitro activity of omadacycline (OMC) and OMC-based combination therapy against carbapenem-resistant Klebsiella pneumoniae (CRKP).

Methods

The broth microdilution assay assessed the in vitro susceptibility of CRKP to OMC. The checkerboard assay was performed to evaluate the activity of OMC combined with polymyxin B (PB), amikacin (AN), or meropenem (MEM) against KPC-producing (class A) CRKP strains, and OMC combined with PB, aztreonam (ATM), MEM, or AN against class B and class A plus class B CRKP strains. Synergistic effects of OMC and PB were further evaluated by time-kill assays in the KPC-producing CRKP strains.

Results

Broth microdilution assays revealed a notable variation in susceptibility between KPC-producing and class B CRKP strains, with MIC50/90 of 32/32 mg/L and 0.5/8 mg/L, respectively. Although KPC-producing CRKP strains were resistant to OMC, a synergistic effect was observed in 37.5% of KPC-producing CRKP strains when OMC was combined with PB. In the nine KPC-producing CRKP strains, time-kill assays found that cell densities of six strains (66.7%) decreased by 3.61 ± 0.23 log10 CFU/mL compared to the initial inoculum after 2 hours of PB exposure. The cell densities further decreased by an average of 2.38 ± 0.23 log10 CFU/mL when the six strains were exposed to OMC plus PB, confirming their potent synergism.

Conclusion

OMC monotherapy is ineffective against KPC-producing CRKP strains, but OMC plus PB has a potent synergistic effect on them, suggesting that OMC plus PB is the preferred combination therapy against KPC-producing CRKP in vitro.

Activity of cefiderocol in combination with tetracycline analogues against carbapenem-resistant Acinetobacter baumannii

Therapeutic options for carbapenem-resistant Acinetobacter baumannii (CA-AB) are quite limited. Cefiderocol, a novel siderophore cephalosporin, has shown potent in vitro activity against CR-AB, and new tetracycline analogues such as eravacycline and omadacycline have been available in recent years. However, the synergism of cefiderocol with tetracycline analogues against CR-AB has not been well investigated. In this study, we evaluated the in vitro synergistic activity of cefiderocol in combination with tetracycline analogues (minocycline, tigecycline, eravacycline and omadacycline) against 48 clinical isolates of CR-AB by checkerboard methods and time-kill assays. Then we further verified the in vitro results with neutropenic murine thigh-infection models. Among 48 tested isolates tested with checkerboard methods, 35.4%, 33.3%, 50.0% and 37.5% showed synergistic interactions (FICI ≤ 0.5) in cefiderocol-minocycline combination, cefiderocol-tigecycline combination, cefiderocol-eravacycline combination and cefiderocol-omadacycline combination, respectively. None of the combinations exhibited any antagonistic interactions. In the time-kill assays, cefiderocol combined with tetracycline analogues showed synergistic effects in most isolates. Animal models found that combination therapy could reduce cell counts by nearly 2 log10 CFU/thigh compared with the monotherapy in the AB-2 isolate who was susceptible to minocycline (MIC = 4 mg/l). But for the AB-26 who was resistant to minocycline, the decrease of bacterial cell counts was less than 1 log10 CFU/thigh compared with cefiderocol monotherapy in the cefiderocol-minocycline, cefiderocol-tigecycline and cefiderocol-omadacycline therapies; while the cefiderocol-eravacycline combination could still reduce the bacterial cell counts nearly 2 log10 CFU/thigh compared with the monotherapy. In summary, the cefiderocol-eravacycline combination seems to be a promising therapeutic strategy for treating CR-AB infections.

Characterization of a Novel KPC-2 Variant, KPC-228, Conferring Resistance to Ceftazidime-Avibactam in an ST11-KL64 Hypervirulent Klebsiella pneumoniae

With the widespread clinical use of ceftazidime-avibactam (CZA), reports of resistance have increased continuously, posing immense threats to public health worldwide. In this study, we explored the underlying mechanisms leading to the development of CZA resistance in an ST11-KL64 hypervirulent Klebsiella pneumoniae CRE146 that harbored the blaKPC-228 gene. Twelve carbapenem-resistant Klebsiella pneumoniae (CRKP) strains were isolated from the same patient, including K. pneumoniae CRE146. Whole genome sequencing (WGS), phylogenetic analysis, blaKPC gene cloning and pACYC-KPC construction assays were conducted to further explore the molecular mechanisms of CZA resistance. Quantitative siderophore production assay, string test, capsule quantification and Galleria mellonella in vivo infection model were applied to verify the level of pathogenicity of K. pneumoniae CRE146. This strain carried key virulence factors, iutA-iucABCD operon and rmpA gene. Compared to the wild-type KPC-2 carbapenemase, the novel KPC-228 enzyme exhibited a deletion of four amino acids in the Ω-loop (del_167-170_ELNS). In addition, the emergence of CZA resistance appeared to be associated with drug exposure, and we observed the in vivo evolution of wild-type KPC-2 to KPC-228 and then the reversion to its original wild-type KPC-2. The blaKPC-228 gene was located within the double IS26 flanking the ISKpn6-blaKPC-228-ISKpn27 core structure and carried on an IncFII/IncR-type plasmid. Notably, CRE146 exhibited high-level resistance to CZA (64/4 mg/L) but increased susceptibility to meropenem (1 mg/L) and imipenem (0.5 mg/L) respectively. PACYC-KPC plasmids were constructed and expressed in K. pneumoniae ATCC13883. Compared to K. pneumoniae ATCC13883 harboring blaKPC-2, K. pneumoniae ATCC13883 harboring blaKPC-228 exhibited a high-level resistance to CZA (32/4 mg/L) and increased susceptibility to meropenem (1 mg/L) and imipenem (0.5 mg/L). Interestingly, K. pneumoniae ATCC13883 harboring blaKPC-228 showed a significant decrease in their resistance to all β-lactamases tested except CZA and ceftazidime. In conclusion, we reported a novel KPC variant, KPC-228, in a clinical ST11-KL64 hypervirulent K. pneumoniae strain, which conferred CZA resistance, possibly through enhancing ceftazidime affinity and reducing avibactam binding. The blaKPC-228 can mutate back to blaKPC-2 under carbapenem pressure, which was very detrimental to clinical treatment. This strain carried both resistance and virulence genes, posing a major challenge in clinical management.

The antibacterial and anti-biofilm effects of novel synthetized nitroimidazole compounds against methicillin-resistant Staphylococcus aureus and carbapenem-resistant Escherichia coli and Klebsiella pneumonia in vitro and in silico

The antibiotic resistance and biofilm formation by bacterial pathogens has led to failure in infections elimination. This study aimed to assess the antibacterial and anti-biofilm properties of novel synthesized nitroimidazole compounds (8a-8o). In this study, nitroimidazole compounds were synthesized via the A3 coupling reaction of sample substrates in the presence of copper-doped silica cuprous sulfate (CDSCS). Fifteen and two carbapenemase producing Escherichia coli and Klebsiella pneumonia (CP-E. coli and CP-K. pneumonia, respectively) and one methicillin-resistant Staphylococcus aureus (MRSA) and one methicillin-susceptible S. aureus (MSSA) plus standard strain of each isolate were included. The antibacterial effects of these compounds demonstrated that the lowest minimum inhibitory and bactericidal concentrations (MIC/MBC, respectively) levels corresponded to compound 8g against S. aureus (1/2 µg/mL) and K. pneumonia (8/32 µg/mL) standard and clinical strains and confirmed by in silico assessment. This was comparable to those of metronidazole being 32-128 µg/mL against K. pneumonia and 32-64 µg/mL against S. aureus. In comparison to metronidazole, against CP-E. coli, compounds 8i and 8m had significantly higher antibacterial effects (p < 0.001) and against CP-K. pneumonia, compounds 8a-8j and 8l-8o had significantly higher (p < 0.0001) antibacterial effects. Compound 8g exhibited significantly higher antibacterial effects against MSSA and compounds 8b (p < 0.001), 8c (p < 0.001), 8d (p < 0.001), 8e (p < 0.001) and 8g (p < 0.0001) exerted significantly higher antibacterial effects than metronidazole against MRSA. Moreover, potential anti-biofilm effects was corresponded to compounds 8a, 8b, 8c, 8e, 8f, 8g, 8i, 8k, 8m and 8n. Considering the antibacterial and anti-biofilm effects of novel synthesized compounds evaluated in this study, further assessments is warranted to verify their properties in vivo and clinical trials in the future.

How do we respond to the threat of multidrug-resistant bacteria? Comparison of antibiotic appraisals from 2016 to 2020 of the French, English, and German HTA agencies

Antimicrobial resistance (AMR) has become a worldwide growing concern over the past decades. Thus, encouraging manufacturers to develop new antibiotics is needed. We hypothesised that transparency on the regulatory appraisals of antibiotics would provide an incentive to pharmaceutical development. We thus aimed at reporting the French health technology assessment (HTA) opinions and reimbursement decision on antibiotics to those German (G-BA) and English (NICE) HTA bodies.A qualitative analysis of the Transparency Committee of the French National Authority for Health (TC-HAS) opinions regarding antibiotics assessment between 2016 and 2020 was performed. Decisions of reimbursement by TC-HAS were compared to those from G-BA and NICE when available. TC-HAS recognized a clinical benefit (CB) for 15/15 evaluated indications, a clinical added value for 9/15, and a public health interest for 8/15. Among the valued antibiotics by HAS, 5 were recommended for restricted use as a "reserve" to protect against the risk of resistance emergence. A comparison of HTA opinions was possible across HTA for only 8 antibiotics. The G-BA granted a reserve status for 4 drugs and NICE a reserve with restricted use for 5 antibiotics. Three of these antibiotics were positioned similarly by the English, German, and French HTA bodies. This qualitative analysis of HTA opinions between different European HTA bodies shows a consistent reimbursement decision of antibiotics against MDR bacteria and tuberculosis besides the differences in the applied assessment methods. This work also shows how HTA bodies could recognize a clinical added value in a context of the emergence of antibiotic resistance.

Genomic insights on cgMLST markers, drug resistance, and urease cluster of Proteus mirabilis strains

Proteus mirabilis, a significant pathogenic bacterium within the Enterobacteriaceae family, is widely distributed across various natural environments. This study conducted a genomic comparison analysis of 1,267 strains of P. mirabilis using extensive genome data from public databases. The objective was to elucidate the pan-genomic structure of P. mirabilis, revealing the composition and distribution of core and accessory gene families among different strains. Additionally, an attempt was made to construct a core genome multilocus sequence typing scheme specific to this species in order to enhance the precision of describing genetic diversity and evolutionary relationships. Furthermore, the study delved into the mechanisms of resistance of P. mirabilis to carbapenems and quinolones. Our findings underscore significant challenges posed by P. mirabilis in terms of antibiotic resistance, with widespread resistance observed particularly against beta-lactams and an increasing trend in resistance to carbapenems and quinolones. These results highlight the severity of P. mirabilis as a pathogen and underscore its rapid evolution and adaptability in developing resistance. This study aims to deepen our understanding of the antibiotic resistance of P. mirabilis, providing important insights for the development of future antimicrobial drugs, promoting effective treatment and control of this pathogen, and mitigating its threat to human health.

IMPORTANCE

The bacterium Proteus mirabilis is a common pathogenic bacterium that is known to cause a variety of human infections. The drug-resistant genes carried by P. mirabilis present a significant challenge to clinical treatment, particularly in regard to the organism's notable resistance to commonly used beta-lactam and quinolone drugs. Furthermore, the prevalence of the urease gene cluster of P. mirabilis at the urease gene level may be associated with the formation of kidney stones. The objective of the study is to analyze the bacterium's drug resistance, urease gene clusters, and gene distribution in genomes in order to facilitate the development of antimicrobial drugs and improve the treatment and control of P. mirabilis infections.

Antimicrobial peptide Hs02 with rapid bactericidal, anti-biofilm, and anti-inflammatory activity against carbapenem-resistant Klebsiella pneumoniae and Escherichia coli

Carbapenem-resistant Klebsiella pneumoniae (CRKP) and Escherichia coli (CREC) are frequently detected in clinical settings, restricting the use of carbapenems. Therefore, there is an urgent need for new antimicrobial strategies to address infections caused by CRKP and CREC. This study investigated the antibacterial, anti-biofilm, and anti-inflammatory effects of the cationic antimicrobial peptide Hs02, along with its potential antimicrobial mechanisms against CRKP and CREC. The results revealed that Hs02 had a low minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against CRKP and CREC, effectively eliminating the bacteria within 30 min. Moreover, Hs02 significantly prevents biofilm formation and disrupts the established biofilms. Further mechanistic studies demonstrated that Hs02 specifically targeted and bound to bacterial outer membrane lipopolysaccharides (LPS), disrupted membrane permeability and integrity, which led to intracellular reactive oxygen species (ROS) accumulation. Furthermore, Hs02 neutralized LPS, thereby suppressing the production of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β in murine macrophage RAW 264.7 cells. In vitro, hemolysis and cytotoxicity assays confirmed Hs02's safety at the tested concentrations and proved that Hs02 improved the survival rate of Galleria mellonella larvae. In conclusion, the findings suggest that Hs02's interaction with LPS and the resulting disruption of membrane integrity may be key factors driving its rapid bactericidal and anti-inflammatory effects.

IMPORTANCE

Eukaryotic antimicrobial peptides are typically amphipathic peptides consisting of approximately 50 amino acids. Many macromolecular proteins in our body contain polypeptide sequences that show characteristics similar to those of antimicrobial peptides. The present research highlights a gap in the current literature regarding the mechanisms by which the intragenic antimicrobial peptide Hs02, derived from human proteins, exerts its rapid bactericidal and anti-inflammatory effects. The findings demonstrate that lipopolysaccharide (LPS) is a key target of Hs02's antimicrobial activity and that its ability to neutralize LPS is crucial for its anti-inflammatory effects.

Molecular characterization of ST15 carbapenem-resistant Klebsiella pneumoniae isolated in a single patient

BACKGROUND

The carbapenem-resistant Klebsiella pneumoniae (CRKP) poses a serious threat to antibiotic applicability and public health. During treatment, K. pneumoniae (KP) frequently exhibits shifts in drug-resistant phenotypes, complicating clinical treatment as it transitions from sensitivity to resistance. In this study, we analysed the clinical and molecular characteristics of drug resistance changes in KP strains isolated from a single patient, and the potential mechanisms underlying these resistance changes.

METHODS

Antimicrobial susceptibility test and string test were conducted to evaluate the resistant and virulent characterization of the strains. Pulsed-field gel electrophoresis (PFGE) was used to investigate the homology relationship between the strains. The whole genome sequencing and phylogenetic analysis of 9 representative isolates was also performed. The transfer ability of the drug-resistant plasmid was studied by plasmid conjugation experiment. The transconjugants were verified by polymerase chain reaction amplification of specific genes, antimicrobial susceptibility test and PFGE.

RESULTS

Our results revealed that 9 KP strains, isolated from the same patient, exhibited 'resistance-sensitivity-resistance-sensitivity' alternately to carbapenems. The differences in DNA fingerprint bands among the nine KP isolates were ≤3, which can be classified as the same PFGE type. Phylogenetic analysis showed that these 9 strains constituted a distinct branch within the phylogenetic tree. All nine KP strains belonged to the ST15-KL19 clone. Six of the strains were classified as CRKP, all of which carried 11 drug resistance genes: oqxB, oqxA, fosA6, aac(3)-lld, blaSHV-28, blaKPC-2, blaOXA-1, mph(A), tet(A), catB3 and aac(6')-lb-cr, mediating drug resistance to quinolones, fosfomycin, aminoglycosides, β-lactam, carbapenems, macrolides and chloramphenicol, belonging to multi-drug resistant bacteria. The carbapenem-resistant plasmid p2-KP3762-1 was found to transfer within species, from CRKP to hypervirulent KPRJF293HA, carbapenem-sensitive KP KP3657 and Escherichia coli C600 at a frequency of (1.19 ± 1.58) ×10-6, (1.09 ± 1.38) ×10-7 and (10.9 ± 9.53) ×10-6 respectively, resulting in the dissemination of carbapenem resistance genes.

CONCLUSIONS

In this study, KP strains isolated from a single patient exhibited an alternating phenotype of resistant-sensitive-resistant-sensitive to carbapenems. The 9 KP isolates share a high degree of genetic similarity. The plasmid p2-KP3762-1, harbouring the carbapenem resistance gene blaKPC-2, may undergo inter-strain and inter-clone transfer via conjugation in the patient during treatment. Furthermore, our findings suggest that the pathogens in this patient are likely to have a common ancestral origin.

Inoculum effect of cefiderocol against NDM-1 producing Escherichia coli in vitro and in a murine model of peritonitis

INTRODUCTION

Cefiderocol is a siderophore cephalosporin active in vitro against carbapenemase-producing Enterobacterales, including New Delhi metallo-β-lactamases (NDM-1). A significant impact of the size of bacterial inoculum on its efficacy has been described in vitro, the clinical impact of which is unclear. Here, we analyse the inoculum effect of cefiderocol against E. coli-NDM-1 in vitro and in a murine peritonitis model.

MATERIALS AND METHODS

Escherichia coli 62-pTOPO and its isogenic variant expressing NDM-1, 62-pTOPO-NDM, were constructed from a clinical strain. MICs and bactericidal kinetics were determined at standard (105 cfu/mL) and high inoculum (107 cfu/mL). The in vivo effect was assessed in a severe murine peritonitis model, comparing low (106 cfu/mL) and high (108 cfu/mL) inoculum. Survival rates, organ sterilization and bacterial counts in spleen and peritoneal fluid were compared.

RESULTS

Cefiderocol MICs for 62-pTOPO and 62-pTOPO-NDM at standard and high inoculum were 0.008, 2, 2 and 1024 mg/L, respectively. Bactericidal activity was not achieved in vitro for 62-pTOPO-NDM at high inoculum with high cefiderocol concentrations (16 mg/L). In vivo, for 62-pTOPO-NDM, no difference was found in survival, organ sterilization or bacterial counts between low and high inoculum. For 62-pTOPO, no difference was observed in survival, despite less organ sterilization and higher bacterial counts in organs with the high inoculum.

CONCLUSION

A significant inoculum effect of cefiderocol was observed in vitro for 62-pTOPO and 62-pTOPO-NDM. However, the effectiveness of cefiderocol was not reduced in vivo with a high bacterial inoculum. In vitro inoculum effect of cefiderocol may not be clinically significant.

Genomic epidemiology and ceftazidime-avibactam high-level resistance mechanisms of Pseudomonas aeruginosa in China from 2010 to 2022

Ceftazidime-avibactam (CZA) resistance is a huge threat in the clinic; however, the underlying mechanism responsible for high-level CZA resistance in Pseudomonas aeruginosa (PA) isolates remains unknown. In this study, a total of 5,763 P. aeruginosa isolates were collected from 2010 to 2022 to investigate the ceftazidime-avibactam (CZA) high-level resistance mechanisms of Pseudomonas aeruginosa (PA) isolates in China. Fifty-six PER-producing isolates were identified, including 50 isolates carrying blaPER-1 in PA, and 6 isolates carrying blaPER-4. Of these, 82.1% (46/56) were classified as DTR-PA isolates, and 76.79% (43/56) were resistant to CZA. Importantly, blaPER-1 and blaPER-4 overexpression led to 16-fold and >1024-fold increases in the MICs of CZA, respectively. WGS revealed that the blaPER-1 gene was located in two different transferable IncP-2-type plasmids and chromosomes, whereas blaPER-4 was found only on chromosomes and was carried by a class 1 integron embedded in a Tn6485-like transposon. Overexpression of efflux pumps may be associated with high-level CZA resistance in blaPER-1-positive strains. Kinetic parameter analysis revealed that PER-4 exhibited a similar kcat/Km with ceftazidime and a high (∼3359-fold) IC50 value with avibactam compared to PER-1. Our study found that overexpression of PER-1 combined with enhanced efflux pump expression and the low affinity of PER-4 for avibactam contributes to high-level resistance to CZA. Additionally, the Tn6485-like transposon plays a significant role in disseminating blaPER. Urgent active surveillance is required to prevent the further spread of high-level CZA resistance in DTR-PA isolates.

Cefiderocol as rescue therapy in a cancer immunosuppressed critically ill child: Case description and literature review

Severe infections caused by multidrug-resistant bacteria have underscored the urgent need for innovative treatment approaches. Novel antimicrobials like cefiderocol have emerged as effective options, but their use in children remains largely unexplored. In this brief report, we describe a severe case of sepsis in a child with an oncohematological disease, caused by a highly drug-resistant strain of Klebsiella pneumoniae. The addition of cefiderocol to other therapies resulted in a successful outcome. Additionally, we provide a literature review of previously published cases involving children treated with this new antibiotic. In our patient, cefiderocol was both safe and effective in combating the multidrug-resistant pathogen. However, further research is needed to better define the indications and safety profile of this novel antibiotic.

KPC variants conferring resistance to ceftazidime-avibactam in Pseudomonas aeruginosa strains

BACKGROUND

This study aimed to characterize three KPC variants (KPC-33, KPC-100, and KPC-201) obtained from a clinical isolate of Pseudomonas aeruginosa (#700), along with two induced strains C109 and C108.

METHODS

Genomic DNAs of #700 (ST235), C109 (ST463), and C108 (ST1076) were sequenced using Illumina and Oxford Nanopore technologies. The transferability and stability of the plasmid was assessed through conjugation experiments and plasmid stability experiments, respectively. Minimum inhibitory concentrations of bacterial strains were determined using broth microdilution methods. In vitro induction was performed using ceftazidime-avibactam (CZA) at concentrations of 6/4 µg/ml. Linear genomic alignments were visualized using Easyfig, and protein structure modeling of the novel KPC variant (KPC-201) was conducted using PyMol.

RESULTS

The plasmids carrying the KPC variants in the three CZA-resistant strains (C109, C108, and #700) had sizes of 39,251 bp (KPC-100), 394,978 bp (KPC-201), and 48,994 bp (KPC-33). All three plasmids belonged to the IncP-like incompatibility (Inc) groups, and the plasmid exhibited relatively high plasmid stability, KPC-33 and KPC-201-harboring plasmids were successfully transferred to the recipient strain P. aeruginosa PAO1rifR. The genetic environments of the three blaKPC genes differed from each other. The mobile elements of the three blaKPC genes were as follows, TnAS1-IS26-ΔISKpn27-blaKPC-33-ISKpn6-IS26, IS6-ΔISKpn27-blaKPC-100-ISKpn6-IS26-Tn3-IS26, and IS6100-ISKpn27-blaKPC-201-ISKpn6-TnAS1. Notably, the length of ΔISKpn27 upstream of the blaKPC-33 and blaKPC-100 genes were remarkably short, measuring 114 bp and 56 bp, respectively, deviating significantly from typical lengths associated with ISKpn27 elements. Moreover, the novel KPC variant, KPC-201, featured a deletion of amino acids LDR at positions 161-163 in KPC-3, resulting in a looser pocket structure contributing to its avibactam resistance.

CONCLUSIONS

KPC-201, identified as a novel KPC variant, exhibits resistance to CZA. The presence of multiple mobile elements surrounding the blaKPC-variant genes on stable plasmids is concerning. Urgent preventive measures are crucial to curb its dissemination in clinical settings.

Determination of the presence of carbapenemase enzymes in carbapenem-resistant Pseudomonas aeruginosa isolates by susceptibility test based algorithm

PURPOSE

Phenotypic methods have been proposed for the detection of carbapenemase production. These tests can have slower turnaround times. With the sensitivity-based algorithm described by Gill et al. will be possible to detect the carbapenemase.

METHODS

Carbapenem-resistant Pseudomonas aeruginosa (CRPA) isolates from three hospitals between January 2017 and December 2021 were included. The modified carbapenemase-inactivation-method(mCIM) and two algorithms were used, defined as "primary algorithm, i.e. ceftazidime and cefepime non-susceptible in addition to imipenem or meropenem resistance" and "secondary algorithm, i.e. ceftolozane/tazobactam non-susceptible in addition to imipenem or meropenem resistance". PCR testing was performed on all isolates.

RESULTS

256 CRPA isolates were included in the study. When the primary or secondary algorithm criteria were applied, there were 173 isolates that met one or both of them. Of these, 29 were CIM-positive isolates.

CONCLUSION

In our study, the use of the algorithm reduced the need for CIM testing by 32 %.

New antibiotics in clinical pipeline for treating infections caused by metallo-β-lactamases producing Gram-negative bacteria

PURPOSE OF REVIEW

To discuss novel antibiotics under clinical development, focusing on agents showing in-vitro activity against metallo-β-lactamases (MBL)-producing carbapenem-resistant Gram-negative bacteria (CR-GNB).

RECENT FINDINGS

Currently, only a few approved agents show activity, alone or in synergistic combinations, against MBL-producing CR-GNB. If approved by regulatory agencies in case of favorable results from ongoing (and, for some agents, already completed) phase-3 studies, some novel β-lactam/β-lactamase inhibitor (BL/BLI) combinations could become available in the next few years as additional important options for treating MBL-producing CR-GNB infections. Additional interesting agents that belong both to BL/BLI combinations and to antibiotic classes other than BL and BL/BLI combinations have also shown activity against MBL-producing CR-GNB, with most of them being in early phases of clinical development.

SUMMARY

Improving the use of these novel agents through virtuous antimicrobial stewardship frameworks able to guarantee both the efficacious treatment of infections requiring their use and the avoidance of their use whenever not necessary remains a challenge of utmost importance that should not be overlooked.

Resistance mechanism of Escherichia coli strains with different ampicillin resistance levels

Antibiotic resistance is an important problem that threatens medical treatment. Differences in the resistance levels of microorganisms cause great difficulties in understanding the mechanisms of antibiotic resistance. Therefore, the molecular reasons underlying the differences in the level of antibiotic resistance need to be clarified. For this purpose, genomic and transcriptomic analyses were performed on three Escherichia coli strains with varying degrees of adaptive resistance to ampicillin. Whole-genome sequencing of strains with different levels of resistance detected five mutations in strains with 10-fold resistance and two additional mutations in strains with 95-fold resistance. Overall, three of the seven mutations occurred as a single base change, while the other four occurred as insertions or deletions. While it was thought that 10-fold resistance was achieved by the effect of mutations in the ftsI, marAR, and rpoC genes, it was found that 95-fold resistance was achieved by the synergistic effect of five mutations and the ampC mutation. In addition, when the general transcriptomic profiles were examined, it was found that similar transcriptomic responses were elicited in strains with different levels of resistance. This study will improve our view of resistance mechanisms in bacteria with different levels of resistance and provide the basis for our understanding of the molecular mechanism of antibiotic resistance in ampicillin-resistant E. coli strains. KEY POINTS: •The mutation of the ampC promoter may act synergistically with other mutations and lead to higher resistance. •Similar transcriptomic responses to ampicillin are induced in strains with different levels of resistance. •Low antibiotic concentrations are the steps that allow rapid achievement of high antibiotic resistance.

Ceftazidime-avibactam versus other antimicrobial agents for treatment of Multidrug-resistant Pseudomonas aeruginosa: a systematic review and meta-analysis

OBJECTIVES

Multidrug-resistant Pseudomonas aeruginosa (MDR-PA) is a life-threatening infection with limited treatment options. This is the first meta-analysis of recently published data to compare the clinical outcomes of ceftazidime-avibactam (CAZ-AVI) with other antimicrobial agents in treating MDR-PA infections.

DESIGN

Systematic review and meta-analysis.

DATA SOURCES

PubMed, Embase and the Cochrane Library have been systematically reviewed, for publications in the English language, from database inception to July 2023.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies comparing CAZ-AVI outcomes with other antimicrobial agents were included. In-hospital mortality & 30-day mortality were assessed as the main outcomes.

DATA EXTRACTION AND SYNTHESIS

Literature screening, data extraction, and the quality evaluation of studies were conducted by two researchers independently, with disagreements resolved by another researcher. The Newcastle-Ottawa Scale was used to assess the bias risk for the included studies. Review Manager V.5.4 was employed for the meta-analysis.

RESULTS

The meta-analysis included four retrospective studies, enrolling 1934 patients. The CAZ-AVI group demonstrated significantly lower in-hospital mortality (risk ratio (RR) = 0.60, 95% CI:0.37-0.97, I2 = 74%, p = 0.04) in three studies with 1444 patients and lower 30-day mortality, in 438 patients from three studies (RR = 0.54, 95% CI:0.28-1.05, I2 = 67%, p = 0.07). No significant difference in clinical success, microbiological success, length of hospital, and ICU stay was observed.

CONCLUSIONS

This meta-analysis demonstrated that CAZ-AVI treatment significantly lowered in-hospital mortality compared with other antimicrobial agents in MDR-PA infections. However, the analysis only included a few observational studies and high-quality, randomized controlled trials are needed to investigate further the scope of CAZ-AVI in MDR-PA  infections.

Emergence of cefiderocol resistance during therapy in NDM-5-producing Klebsiella pneumoniae isolates harboring siderophore receptors mutations

Cefiderocol, a siderophore-conjugated cephalosporine, is a promising drug used to treat infection with carbapenem-resistant gram-negative bacteria. Here, we report a case of pneumonia induced by multiple gram-negative pathogens, including a carbapenem-resistant Klebsiella pneumoniae developing cefiderocol resistance within 32 days of cefiderocol therapy. Whole genome sequencing of three consecutive K. pneumoniae isolates revealed that the bacteria were isogenic and were carrying several broad-spectrum β-lactamases (blaNDM5 and blaCTX-M-15). Two isolates with elevated minimum inhibitory concentration against cefiderocol harbored mutations in genes encoding siderophore: one in the cirA gene and one in both the cirA and the fiu genes. The combination of a metallo-β-lactamase background and mutations in siderophore receptors was associated with phenotypic resistance to cefiderocol.

A Novel Variant of KPC-179 Conferring Ceftazidime-Avibactam Resistance in a Carbapenem-Resistant Klebsiella pneumoniae Isolate

Objective

Ceftazidime-avibactam (CZA) is a novel β-lactam/β-lactamase inhibitor with activity against carbapenem-resistant Klebsiella pneumoniae (CRKP) that produce Klebsiella pneumoniae carbapenemase (KPC). In this study, we report the first cases of CZA resistance to develop during treatment of CRKP infections and identify the resistance mechanism.

Methods

APB/EDTA and NG-Test CARBA5 were used to detect the production of carbapenemase, whole-genome sequencing (WGS) and conjugation experiment were used to identify potential resistance mechanisms of CZA-susceptible (HX1032) and -resistant (HX1192) K. pneumoniae isolates.

Results

HX1192 K. pneumoniae was not recognized by APB/EDTA and NG-Test CARBA5 phenotypic assays, WGS revealed it carrying a novel KPC variant, KPC-179, molecular analysis highlighted a G394A mutation, and an ATC insertion at 543 in the blaKPC-2 gene, resulting in an A133T substitution and insertion of the amino acid S at Ambler position 183 in the protein sequence. Remarkably, this mutation restored susceptibility of imipenem (MIC = 0.25 mg/L).

Conclusion

Our study highlights the importance of monitoring susceptibility during CZA treatment and accurately detecting KPC variants.

[Clinical characteristics and risk factors of carbapenem-resistant Pseudomonas aeruginosa infection in children]

OBJECTIVES

To investigate the clinical characteristics of carbapenem-resistant Pseudomonas aeruginosa (CRPA) infection in children and the risk factors for such infection.

METHODS

A retrospective analysis was conducted among 60 children with CRPA infection (CRPA group) who were hospitalized in Shenzhen Children's Hospital, China Medical University, from January 2018 to September 2023, and 82 children with carbapenem-sensitive Pseudomonas aeruginosa infection during the same period were randomly selected as the control group. A multivariate logistic regression analysis was used to investigate the risk factors for CRPA infection.

RESULTS

Among the 60 children with CRPA infection, 31 (52%) were admitted to the intensive care unit (ICU), and the lower respiratory tract was the main detection site in 32 children (53%). The univariate analysis showed that sex, history of invasive treatment within 1 year, antibiotic use before admission, presence of underlying condition, ICU admission, invasive procedure after admission, antibiotic use for >14 days, and the type of antibiotics used of ≥3 were associated with CRPA infection (P<0.05). The multivariate logistic regression analysis showed that the history of invasive treatment within 1 year (OR=3.228, P<0.05), antibiotic use before admission (OR=4.052, P<0.05), antibiotic use for >14 days (OR=4.961, P<0.05), and the type of antibiotics used of ≥3 (OR=3.687, P<0.05) were independent risk factors for CRPA infection in children.

CONCLUSIONS

CRPA infection in children may be associated with a history of invasive treatment within the past year, antibiotic use before admission, duration of antibiotic use after admission, and the diversity of antibiotic types used.

Antimicrobial Resistance Profile of Zoonotic Clinically Relevant WHO Priority Pathogens

The World Health Organization announced critically important bacterial and fungal pathogens displaying alarming levels of antimicrobial resistance, which currently represent difficult-to-treat cases of morbidity. Within this grouping, the ESKAPE pathogens (Enterococcus faecium, Staphylococcus aureus, Klebsiella pneumoniae, Acinetobacter baumannii, Pseudomonas aeruginosa, and Enterobacter species) are causative of significant morbidity and mortality. Studies described herein demonstrate the presence of critically important fungal and ESKAPE bacterial species in companion animals which are zoonotic in nature. The relationship between the environment, animals, and human infectious disease has long been recognized as part of One Health. This research investigates the resistance patterns of isolated zoonotic pathogens using recognized in vitro methodologies, namely disk diffusion, minimum inhibitory concentration testing, and genetic screening. Antibiotic susceptibility testing and gene analysis demonstrated an association between multi-drug resistance and extended beta spectrum lactamase production in critical-priority bacteria. Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, and Pseudomonas aeruginosa exhibit great levels of multi-drug resistance. Fungal isolates demonstrated high levels of resistance, with Amphotericin B proving the most effective antifungal agent investigated. The level of antimicrobial resistance present in clinically relevant bacterial and fungal pathogens isolated from animal cases of morbidity in this study is alarming. In conclusion, this study shows that animals can act as a reservoir facilitating the transmission of antibiotic-resistant pathogens and genes zoonotically.

Inhibition of Pseudomonas aeruginosa Carbonic Anhydrases, Exploring Ciprofloxacin Functionalization Toward New Antibacterial Agents: An In-Depth Multidisciplinary Study

Ciprofloxacin (CPX) is one of the most employed antibiotics in clinics to date. However, the rise of drug-resistant bacteria is dramatically impairing its efficacy, especially against life-threatening pathogens, such as Pseudomonas aeruginosa. This Gram-negative bacterium is an opportunistic pathogen, often infecting immuno-compromised patients with severe or fatal outcomes. The evidence of the possibility of exploiting Carbonic Anhydrase (CA, EC: 4.2.1.1) enzymes as pharmacological targets along with their role in P. aeruginosa virulence inspired the derivatization of CPX with peculiar CA-inhibiting chemotypes. Thus, a large library of CPX derivatives was synthesized and tested on a panel of bacterial CAs and human isoenzymes I and II. Selected derivatives were evaluated for antibacterial activity, revealing bactericidal and antibiofilm properties for some compounds. Importantly, promising preliminary absorption, distribution, metabolism, and excretion (ADME) properties in vitro were found and no cytotoxicity was detected for some representative compounds when tested in Galleria mellonella larvae.

Navigating antibiotic therapy in acute cholangitis: Best practices and new insights

Globally, antibiotic resistance is linked to increased morbidity, mortality, and healthcare costs, which necessitates further research on optimal antibiotic usage. Acute cholangitis (AC), a common cause of community-acquired bacteremia, often requires antimicrobial therapy. Therefore, studying the appropriate use of antibiotics for AC is considered crucial for suppressing the emergence of resistant bacteria and reducing adverse antibiotic-associated events. The Tokyo Guidelines 2018 (TG18) recommend 4-7 days of antibiotics post-biliary drainage. However, this lacks strong evidence and is based primarily on various evidence and expert opinions. Recent retrospective studies advocate for a shorter 1-3-day antibiotic course for AC, thereby prompting a need to reassess the treatment duration to balance therapeutic efficacy and minimize resistance and adverse effects. Choosing the appropriate duration and antibiotics based on susceptibility to pathogens causing cholangitis is important. Awareness of local resistance patterns and understanding patients' risks of resistant pathogens are prerequisite for effective treatment. We must explore the applicability of these guidelines in specific scenarios such as severe AC, positive blood cultures, fever, or hilar biliary obstructions due to malignancy. This comprehensive review considers both the duration and type of antibiotics and aims to enhance treatment outcomes while reducing the risk of resistant bacterial infections.

Clinical pilot of bacterial transcriptional profiling as a combined genotypic and phenotypic antimicrobial susceptibility test

Antimicrobial resistance is a growing health threat, but standard methods for determining antibiotic susceptibility are slow and can delay optimal treatment, which is especially consequential in severe infections such as bacteremia. Novel approaches for rapid susceptibility profiling have emerged that characterize either bacterial response to antibiotics (phenotype) or detect specific resistance genes (genotype). Genotypic and Phenotypic AST through RNA detection (GoPhAST-R) is a novel assay, performed directly on positive blood cultures, that integrates rapid transcriptional response profiling with the detection of key resistance gene transcripts, thereby providing simultaneous data on both phenotype and genotype. Here, we performed the first clinical pilot of GoPhAST-R on 42 positive blood cultures: 26 growing Escherichia coli, 15 growing Klebsiella pneumoniae, and 1 with both. An aliquot of each positive blood culture was exposed to nine different antibiotics, lysed, and underwent rapid transcriptional profiling on the NanoString platform; results were analyzed using an in-house susceptibility classification algorithm. GoPhAST-R achieved 95% overall agreement with standard antimicrobial susceptibility testing methods, with the highest agreement for beta-lactams (98%) and the lowest for fluoroquinolones (88%). Epidemic resistance genes including the extended spectrum beta-lactamase blaCTX-M-15 and the carbapenemase blaKPC were also detected within the population. This study demonstrates the clinical feasibility of using transcriptional response profiling for rapid resistance determination, although further validation with larger and more diverse bacterial populations will be essential in future work. GoPhAST-R represents a promising new approach for rapid and comprehensive antibiotic susceptibility testing in clinical settings.IMPORTANCEExposure to antibiotics causes differential transcriptional signatures in susceptible vs resistant bacteria. These differences can be leveraged to rapidly predict resistance profiles of Escherichia coli and Klebsiella pneumoniae in clinically positive blood cultures.

Evaluation of gradient strip diffusion for susceptibility testing of aztreonam-avibactam in metallo-β-lactamase-producing Enterobacterales

The emergence of metallo-β-lactamase (MBL)-producing Enterobacterales presents unique clinical treatment challenges. Recently developed β-lactam/ β-lactamase inhibitor combination agents, while effective against other carbapenemase-producing organisms, are notably ineffective against MBL producers. While MBLs do not hydrolyze monobactams (aztreonam), many MBL-producing organisms are resistant to aztreonam through alternate mechanisms, leaving cefiderocol as the sole monotherapy treatment option recommended for MBL producers. Recent guidelines for the treatment of MBL-harboring organisms have added combination therapy with aztreonam and ceftazidime-avibactam, using ceftazidime-avibactam as a source of the β-lactamase inhibitor avibactam. Current laboratory testing options for the combination of aztreonam-avibactam are limited to broth microdilution (BMD) and broth disk elution (BDE) methods, which are not practical in most clinical laboratories. In this study, we evaluated the performance of aztreonam/avibactam gradient strips on 103 MBL-producing Enterobacterales patient isolates as well as an additional 31 isolates from the CDC AR Bank. All MBL Enterobacterales patient isolates included in this study harbored a New Delhi metallo-β-lactamase (blaNDM) gene. Essential agreement of gradient strip minimal inhibitory concentrations (MICs) for patient isolates compared to BMD was 93.2%. While there are no established breakpoints for aztreonam-avibactam, category agreement (CA) for patient isolates was 97.1% when using the CLSI aztreonam breakpoints. There were no major or very major errors observed. There were three minor errors. Precision for aztreonam-avibactam gradient strip diffusion was 100%. These data demonstrate that the use of gradient strip diffusion for aztreonam-avibactam MIC determination in MBL-producing Enterobacterales is a viable option for clinical laboratories.

Impact of adequate empirical combination therapy on mortality in septic shock due to Pseudomonas aeruginosa bloodstream infections: a multicentre retrospective cohort study

OBJECTIVES

To determine the association of adequate empirical combination therapy (AECT) with 30-day all-cause mortality in patients with septic shock due to Pseudomonas aeruginosa bloodstream infections (BSI).

METHODS

This multicentre, retrospective cohort study analysed data from 14 public hospitals in Italy, including all consecutive adult patients admitted during 2021-2022 with septic shock due to P. aeruginosa BSI. We compared the outcomes of patients receiving AECT to those on adequate empirical monotherapy (AEMT) using Cox regression analyses.

RESULTS

Of the 98 patients who received adequate empirical antibiotic treatment for septic shock due to P. aeruginosa BSI, 24 underwent AECT and 74 were given AEMT. AECT was associated with a lower 30-day all-cause mortality (25%, six out of 24) compared to AEMT (56.8%, 42 out of 74; P = 0.007). Multivariate Cox regression analysis indicated AECT as the only factor significantly associated with improved survival (aHR 0.30; 95% CI 0.12-0.71; P = 0.006). By contrast, the use of monotherapy or combination therapy in the definitive regimen did not influence mortality (aHR 0.73; 95% CI 0.25-2.14; P = 0.568).

CONCLUSIONS

AECT may be associated with reduced mortality compared to monotherapy in septic shock patients due to P. aeruginosa BSI. However, the administration of definitive adequate monotherapy or combination therapy yields similar outcomes, suggesting that once susceptibility is documented, switching to a single active in vitro drug is safe and feasible. Further studies are recommended to validate these findings.

Comparative evaluation of early treatment with ceftolozane/tazobactam versus ceftazidime/avibactam for non-COVID-19 patients with pneumonia due to multidrug-resistant Pseudomonas aeruginosa

BACKGROUND

Ceftolozane/tazobactam and ceftazidime/avibactam are commonly used in patients with MDR-Pseudomonas aeruginosa (PSA) pneumonia (PNA). This study compared outcomes between non-COVID-19 hospitalized patients with MDR-PSA PNA who received ceftolozane/tazobactam or ceftazidime/avibactam.

METHODS

The study included non-COVID-19 adult hospitalized patients with MDR-PSA PNA in the PINC AI Healthcare Database (2016-22) who received ceftolozane/tazobactam or ceftazidime/avibactam within 3 days of index culture for ≥2 days. Outcomes were mortality, recurrent MDR-PSA PNA, discharge destination, post-index culture day length of stay (LOS) and costs (in US dollars, USD), and hospital readmission.

RESULTS

The final sample included 197 patients (117 ceftolozane/tazobactam, 80 ceftazidime/avibactam). No significant differences were observed in mortality and post-index culture LOS and costs between groups. In the multivariable analyses, patients who received ceftolozane/tazobactam versus ceftazidime/avibactam had lower recurrent MDR-PSA PNA (7.9% versus 18.0%, P = 0.03) and 60 day PNA-related readmissions (11.1% versus 28.5%, P = 0.03) and were more likely to be discharged home (25.8% versus 9.8%, P = 0.03). Compared with ceftazidime/avibactam patients, ceftolozane/tazobactam patients had lower adjusted median total antibiotic costs (5052 USD versus 8099 USD, P = 0.003) and lower adjusted median comparator (ceftolozane/tazobactam or ceftazidime/avibactam) antibiotic costs (3938 USD versus 6441 USD, P = 0.005). In the desirability of outcome ranking (DOOR) analysis, a ceftolozane/tazobactam-treated patient was more likely to have a more favourable outcome than a ceftazidime/avibactam-treated patient [DOOR probability: 59.6% (95% CI: 52.5%-66.8%)].

CONCLUSIONS

Early treatment with ceftolozane/tazobactam may offer some clinical and cost benefits over ceftazidime/avibactam in patients with MDR-PSA PNA. Further large-scale studies are necessary to comprehensively understand the outcomes associated with these treatments for MDR-PSA PNA.

Effectiveness of short treatment duration for carbapenemase-producing Enterobacterales in bloodstream-infections: A retrospective cohort study

OBJECTIVE

We analyse the effectiveness of short courses of adequate treatment in patients with episodes of carbapenemase-producing Enterobacterales bloodstream-infections (CPE-BSI).

METHODS

Patients with first monomicrobial CPE-BSI episodes who received ≥72 h of appropriate treatment from 2014-2022 were selected. Detection of CPE was established on the basis of phenotypic antibiogram and confirmation by PCR and/or immunochromatographic methods. Patients were classified in short treatment group (STG) those who received 3-10 days of appropriate treatment, and long treatment (LTG) those receiving >10 days. Unfavourable outcome consisted in a composite of global 30-day mortality and/or persistent bacteremia and/or recurrent bacteremia. Inverse probability of treatment weighting (IPTW) analysis was performed to compare the outcome between the two study groups.

RESULTS

We included 105 CPE-BSI episodes: 99 were caused by OXA-48-like, 4 VIM and 2 KPC carbapenemases. Thirty-nine patients (37.1%) were included in the STG and 66 (62.9%) in LTG. The STG group presented frequent treatment with ceftazidime-avibactam (43.6% vs. 24.2%, P = 0.03) and lower in-hospital stay (21 days vs. 32 days, P = 0.02). Overall, 28 patients (26.7%) presented unfavourable outcome: IPTW analysis showed no differences in the outcome between STG to LTG groups (24.2% vs. 30.8%, weighted-risk difference 6.6%, P = 0.44). Patients with unfavourable outcome presented more frequently source other than urinary-biliary (46.4% vs. 23.4%, P = 0.02), received less frequently ceftazidime-avibactam (14.3% vs. 37.7%, P = 0.02) and presented frequently with absence of source control when indicated (28.6% vs. 13.0%, P = 0.06).

CONCLUSIONS

Short treatment durations for CPE-BSI episodes may be effective, as long as they are appropriate and source control is performed.

Development and validation of a pentaplex PCR assay for rapid detection of blaCTX-M, blaOXA-1, blaCMY, blaNDM and the PBP3 insert in Enterobacterales

BACKGROUND

There is a high diversity of beta-lactamases in gram negative pathogens, making them difficult to treat. In the presence of OXA-1 and ampC, PTZ is no longer clinically relevant when treating Enterobacterales expressing ESBLs. Further, MBL infections are often treated with the combination of ceftazidime/avibactam with aztreonam. . It has recently been reported that NDM-expressing E. coli isolates co-harboring PBP3 insert develops resistance to this triple combination.

METHODS

A pentaplex PCR is developed and validated to simultaneously detect blaCTX-M, blaOXA-1, blaCMY, blaNDM, and the PBP3 insert in whole genome sequenced E. coli and K. pneumoniae isolates. In addition, the isolates chosen for pentaplex PCR evaluation were tested for their minimum inhibitory concentrations (MICs) against piperacillin/tazobactam, cefoperazone/sulbactam (C/S), ertapenem, imipenem, meropenem, ceftazidime/avibactam, aztreonam/avibactam, cefepime/taniborbactam, and cefiderocol.

RESULTS

The developed pentaplex PCR showed 100 % reproducibility with the antimicrobial resistance profile generated from whole genome sequenced data. PTZ and C/S are not effective against ESBL and/or OXA-1 expressing E. coli and K. pneumoniae isolates and do not offer any activity against CMY co-producers. Further, the combined effect of CMY, NDM and PBP3 inserts impacts aztreonam/avibactam activity and reduces the susceptibility to 40 % in E. coli isolates. While, aztreonam/avibactam showed potent activity against NDM-expressing K. pneumoniae isolates. Importantly, cefepime/taniborbactam and cefiderocol showed limited activity against NDM-expressing E. coli and K. pneumoniae isolates.

CONCLUSION

The pentaplex PCR was effective in detecting four beta-lactamases (blaCTX-M, blaOXA-1, blaCMY, blaNDM) as well as PBP3 inserts. It is expected that using pentaplex PCR as a diagnostic test for resistance detection in clinical practice will improve patient outcomes by providing prompt and targeted treatment.

Unusual and complicated peritonitis: Your questions answered

Effective treatment of infections is a growing challenge owing to antimicrobial resistance. Peritoneal dialysis (PD) patients experience more frequent hospitalisations than the general population and have greater exposure to antibiotics, making them particularly vulnerable to this threat. Over the last decade, we have noted a surge in cases of complicated peritoneal dialysis-associated peritonitis (PD peritonitis) caused by antimicrobial-resistant organisms, including extended-spectrum beta-lactamase (ESBL), AmpC beta-lactamase-producing Enterobacterales, Pseudomonas aeruginosa and fungi. Practitioners must be alert to these organisms, seek early recognition of these resistance patterns and make timely adjustments in order to avoid delay in treatment that may increase risk of PD catheter removal and technique failure. We present a case of successful treatment of ESBL peritonitis, highlight its challenges, while providing guidance on management of other unusual and complicated PD peritonitis.

Ceftazidime/avibactam alone or in combination with an aminoglycoside for treatment of carbapenem-resistant Enterobacterales infections: A retrospective cohort study

BACKGROUND

Ceftazidime/avibactam is one of the preferred treatment options for carbapenem-resistant Enterobacterales (CRE). However, the benefit of combining ceftazidime/avibactam with another antibiotic remains unclear.

OBJECTIVES

To identify variables associated with treatment failure during the use of ceftazidime/avibactam for CRE infections and assess the effect of combining an aminoglycoside with ceftazidime/avibactam.

METHODS

This was a retrospective cohort study of patients with a positive CRE culture treated with ceftazidime/avibactam between 2015 and 2021 in 134 Veterans Affairs (VA) facilities. The primary outcome was 30-day mortality and the secondary outcome was in-hospital mortality. A subanalysis in patients who received an aminoglycoside was also performed.

RESULTS

A total of 303 patients were included. The overall 30-day and in-hospital mortality rates were 12.5% and 24.1%, respectively. Age (aOR 1.052, 95% CI 1.013-1.093), presence in the ICU (aOR 2.704, 95% CI 1.071-6.830), and receipt of an aminoglycoside prior to initiation of ceftazidime/avibactam (aOR 4.512, 95% CI 1.797-11.327) were independently associated with 30-day mortality. In the subgroup of patients that received an aminoglycoside (n = 77), their use in combination with ceftazidime/avibactam had a 30-day mortality aOR of 0.321 (95% CI, 0.089-1.155).

CONCLUSION

In veterans treated with ceftazidime/avibactam for CRE infections, increased age, receipt of an empiric aminoglycoside, and presence in the ICU at the time of index culture were associated with higher 30-day mortality. Among patients who received an aminoglycoside, their use in combination with ceftazidime/avibactam trended toward protectiveness of 30-day mortality, suggesting a potential role for this combination to treat CRE infections in patients who are more severely ill.

First case report of a vertebral osteomyelitis caused by carbapenem-resistant Enterobacter cloacae treated with imipenem/cilastatin/relebactam prolonged infusion then meropenem/vaborbactam in continuous infusion

Introduction

Bone and joint infections (BJIs) caused by multidrug-resistant bacteria are becoming more frequent. However, data on the use of novel β-lactam/β-lactamase inhibitors, such as imipenem/cilastatin/relebactam (I-R) and meropenem/vaborbactam (MVB), to treat BJIs is lacking. Furthermore, prolonged infusions of these β-lactams should theoretically optimize pharmacokinetic/pharmacodynamics target in these indications, but there are currently no reports on this type of infusions, especially in the setting of BJI.

Case Presentation

We report a case of a vertebral osteomyelitis caused by carbapenem-resistant Enterobacter cloacae successfully treated with extended-infusion of I-R (1.25 g q6h over 2 h), then with continuous infusion of MVB (2 g q4h as over 4 h). Therapeutic drug monitoring confirmed that extended-infusion of I-R and continuous infusion of MVB achieved serum concentrations up to 12 mg/L of imipenem and 19 mg/L of meropenem, respectively.

Conclusion

The favourable outcome of this patient treated for a vertebral osteomyelitis caused by carbapenem-resistant E. cloacae suggest that extended- and continuous infusions of I-R and MVB, are promising regimens for treatment of BJIs caused by carbapenem-resistant Enterobacterales.

Risk factors and drug resistance of adult community-onset urinary tract infections caused by Escherichia coli-producing extended-spectrum β-lactamase in the Chongqing region, China: a retrospective case-control study

OBJECTIVE

To evaluate the prevalence, resistance and risk factors of community-onset urinary tract infections (COUTIs) caused by extended-spectrum β-lactamase-producing Escherichia coli (ESBL-EC) for providing a basis for the selection of clinical therapeutic agents.

DESIGN

A retrospective case-control study.

SETTING

The Affiliated Dazu Hospital of Chongqing Medical University (also known as The People's Hospital of Dazu Chongqing), a 1000-bed tertiary hospital in China.

DATA AND PARTICIPANTS

This study encompassed adult patients diagnosed with community-acquired urinary tract infections (UTIs) caused by E. coli between May 2017 and December 2022 with exclusion criteria including incomplete clinical data, disagreement to participate in the study, hospitalisation duration exceeding 48 hours prior to confirmation of diagnosis and prior history of urinary tract infection caused by E. coli.

OUTCOME MEASURES

The risk factors for COUTIs caused by ESBL-EC were evaluated using a case-control design, defining patients who were diagnosed with UTIs and had an ESBL-positive urine culture as the case group and patients who were diagnosed with UTIs and had an ESBL-negative urine culture as the control group. Perform drug susceptibility testing and resistance analysis on isolated ESBL-EC.

RESULTS

In total, 394 cases of COUTIs caused by E. coli were included; 192 cases were ESBL-positive with a detection rate of 48.7% (192/394). Parenchymal tumour, history of urolithiasis stone fragmentation, history of urological surgery, hospitalisation within 6 months, indwelling catheter outside the hospital and antibiotic use (mainly third-generation cephalosporins) were the factors significantly associated with COUTIs caused by ESBL-EC (p<0.05) through logistic regression for univariate analysis. Multivariate analysis revealed that a history of urolithiasis stone fragmentation (OR=2.450; 95% CI: 1.342 to 4.473; p=0.004), urological surgery (OR=3.102; 95% CI: 1.534 to 6.270; p=0.002), indwelling catheter outside hospital (OR=2.059; 95% CI: 1.025 to 4.133; p=0.042), hospitalisation within 6 months (OR=2.127; 95% CI: 1.207 to 3.748; p=0.009) and use of third-generation cephalosporins (OR=1.903; 95% CI: 1.069 to 3.389; p=0.029) were the independent risk factors for COUTIs caused by ESBL-EC. The results of the drug susceptibility testing revealed that ESBL-EC exhibited the highest resistance rates to ampicillin, ceftriaxone and cefixime, all at 100%. Mezlocillin followed with a resistance rate of 98.7%. On the other hand, ESBL-EC strains displayed the highest sensitivity to carbapenem antibiotics (imipenem, meropenem, ertapenem) and amikacin, all at 100%. Sensitivity rates were also high for cefotetan at 96.6%, piperacillin/tazobactam at 95.3% and nitrofurantoin at 87.9%.

CONCLUSIONS

Our results revealed high ESBL-EC detection rates. COUTIs caused by ESBL-EC are more likely to occur in patients with parenchymal tumour, a history of urolithiasis stone fragmentation, a history of urological surgery, hospitalisation within 6 months, indwelling catheter outside the hospital and use of third-generation cephalosporins. These patients were highly resistant to penicillins, cephalosporins and quinolones.

Prevalence and clinical significance of the genotypic carriage among ESBL phenotype-negative Escherichia coli and Klebsiella pneumoniae clinical isolates in bacteremia: a study in a Malaysian tertiary center

Background

Antimicrobial resistance (AMR) can lead to fatal consequences. AMR genes carriage by phenotypically susceptible bacteria, such as Extended-Spectrum β-Lactamases (ESBL)s in Enterobacteriaceae, have potential implications for AMR spread and therapeutic outcomes. This phenomenon should be investigated.

Methods

Positive blood cultures from hospitalized patients in a Malaysian tertiary center between April 2022 and March 2023 were reviewed. A total of 137 clinical isolates of Escherichia coli (E.coli), Klebsiella pneumoniae (K.pneumoniae), and Klebsiella oxytoca were included. The antibiotic susceptibility and ESBL phenotypes were determined by disk diffusion method and the identification of genotypes by multiplex polymerase chain reaction. The clinical characteristics and outcome information were extracted by reviewing patients' medical records to evaluate the clinical significance of the ESBL genotype-positive but phenotype-negative isolates in bacteremia.

Results

All 137 isolates were positive for at least one genotype (bla CTX-M, n = 71, 51.8%; bla SHV, n = 87, 63.5%; bla TEM, n = 95, 69.3%; bla OXA-1, n = 38, 27.7%). While bla CTX-M was proportionately higher in the ESBL phenotype-positive isolates than ESBL phenotype-negative isolates (33/37, 89.2% vs 38/100, 38%; p < 0.001), more than half of those harboring bla CTX-M remained susceptible to third-generation cephalosporins (3GC). The sensitivity (Sen) of bla CTX-M for ESBL phenotypes prediction was 89.19% (95% confidence interval [CI], 74.58 - 96.97%); however, specificity (Sp) was low (46.47%; 95% CI 39.75 - 53.32). The patient characteristics were similar among 98 ESBL phenotype-negative cases, except that the non-bla CTX-M carrier group had significantly more renal impairment (0/37 vs 7/61, p = 0.043) and gastrointestinal sources of bacteremia (9/37 vs 27/61, p = 0.047). No differences were observed in infection severity, in-hospital mortality, and length of stay (LOS) between the bla CTX-M and non-bla CTX-M carrier groups.

Conclusion

The current study provides insight into the gene carriage in E.coli and Klebsiella species clinical isolates, including bla CTX-M genotypes in antibiotic-susceptible strains from a Malaysian hospital. The ESBL encoding genotypes such as bla CTX-M presented substantially beyond one-third of the ESBL phenotype-negative or 3GC susceptible E.coli and K.pneumoniae isolated from bloodstream infection. Although clinical outcomes were not worsened with bla CTX-M genotype-positive but ESBL phenotype-negative isolates in bacteremia, the potential implications for AMR spread deserve further investigation.

Sociodemographic disparities in antibiotic-resistant outpatient urine cultures in a Boston hospital, 2015-2020: a cross-sectional analysis

BACKGROUND

Antibiotic resistance in uropathogens has rapidly escalated over time, complicating treatment and increasing morbidity and mortality. Few studies have explored how the social determinants of health may be associated with patients' risks for acquiring antibiotic-resistant (AR) uropathogens.

METHODS

We identified urine cultures collected from outpatients presenting to Tufts Medical Center Primary Care Practices between 2015 and 2020. Specimens were included if patients' age, sex, and residential address were recorded in the electronic medical record (EMR) and if their urine culture yielded Enterococcus spp. or one or more gram-negative bacterial organism(s) or for which antibiotic susceptibility profiling and species identification was conducted. We abstracted patients' sociodemographic characteristics from the EMR and used US Census Bureau data to identify characteristics about patients' census tracts of residence. We evaluated associations between individual- and neighborhood-level characteristics and patients' risk of having a urine culture resistant to (1) three or more antibiotic classes (i.e., multidrug resistant [MDR]), (2) first-line treatments, (3) fluoroquinolones, (4) aminoglycosides, or (5) ceftriaxone using logistic regression models and a Bonferroni correction to account for multiple hypothesis testing.

RESULTS

We included urine cultures from 1,306 unique outpatients, most of whom were female (89%). Patients largely self-identified as Non-Hispanic White (36%), Asian (15%), or Non-Hispanic Black (11%). Over 60% lived in an environmental justice-designated census tract. Most included isolates were Escherichia coli (76%) or Klebsiella pneumoniae (7%). Using public insurance increased patients' odds of having a uropathogen resistant to first-line antibiotics, but living in a limited-income neighborhood reduced patients' odds of having a MDR uropathogen by 47%. We noted a strong but non-significant positive trend between speaking a language other than English and having an aminoglycoside-resistant uropathogen (p-value = 0.02). Most notably, after controlling for other factors, we observed no statistically significant associations between race or ethnicity and AR uropathogens.

CONCLUSION

The social determinants of health may play important and intersecting roles in determining a patient's risk of having a resistant uropathogens that is more challenging or expensive to treat. It is crucial to acknowledge how race is likely to be a proxy for other factors affecting health, and to consider that some groups may be disproportionately impacted by antibiotic resistance.

Innovative approaches in phenotypic beta-lactamase detection for personalised infection management

Beta-lactamase-producing Enterobacteriaceae present a significant therapeutic challenge. Current developments in phenotypic diagnostics focus primarily on rapid minimum inhibitory concentration (MIC) determination. There is a requirement for rapid phenotypic diagnostics to improve antimicrobial susceptibility tests (AST) and aid prescribing decisions. Phenotypic AST are limited in their ability to characterise beta-lactamase-producing Enterobacteriaceae in detail. Despite advances in rapid AST, gaps and opportunities remain for developing additional diagnostic approaches that facilitate personalised antimicrobial prescribing. In this perspective, we highlight the state-of-the-art in beta-lactamase detection, identify gaps in current practice, and discuss barriers for innovation within this field.

Analytical and clinical validation of direct detection of antimicrobial resistance markers by plasma microbial cell-free DNA sequencing

Sequencing of plasma microbial cell-free DNA (mcfDNA) has gained increased acceptance as a valuable adjunct to standard-of-care testing for diagnosis of infections throughout the body. Here, we report the analytical and clinical validation of a novel application of mcfDNA sequencing, the non-invasive detection of seven common antimicrobial resistance (AMR) genetic markers in 18 important pathogens. The AMR markers include SCCmec, mecA, mecC, vanA, vanB, blaCTX-M, and blaKPC. The AMR markers were computationally linked to the pathogens detected. Analytical validation showed high reproducibility (100%), inclusivity (54 to 100%), and exclusivity (100%). Clinical accuracy was assessed with 114 unique plasma samples from patients at seven study sites with concordant culture results for target bacteria from a variety of specimen types and correlated with available phenotypic antimicrobial susceptibility test results and genotypic results. The positive percent agreement (PPA), negative percent agreement (NPA), and diagnostic yield (DY) were estimated for each AMR marker. DY was defined as the percentage of tests that yielded an actionable result of either detected or not detected. The results for the combination of SCCmec and mecA for staphylococci were PPA 19/20 (95.0%), NPA 21/22 (95.4%), DY 42/60 (70.0%); vanA for enterococci were PPA 3/3 (100%), NPA 2/2 (100%), DY 5/6 (83.3%); blaCTX-M for gram-negative bacilli were PPA 5/6 (83.3%), NPA 29/29 (100%), DY 35/49 (71.4%); and blaKPC for gram-negative bacilli were PPA 0/2 (0%), NPA: 23/23 (100%), DY 25/44 (56.8%). The addition of AMR capability to plasma mcfDNA sequencing should provide clinicians with an effective new culture-independent tool for optimization of therapy.

IMPORTANCE

This manuscript is ideally suited for the Innovative Diagnostic Methods sections as it reports the analytical and clinical validation of a novel application of plasma microbial cell-free DNA sequencing for direct detection of seven selected antimicrobial resistance markers in 18 target pathogens. Clearly, it has potential clinical utility in optimizing therapy and was incorporated into the Karius test workflow in September 2023. In addition, the workflow could readily be adapted to expand the number of target bacteria and antimicrobial resistance markers as needed.

Optimizing Treatment Strategies for Carbapenem-Resistant Acinetobacter Baumannii-Associated Pneumonia: A Multicenter Study in Chinese Hospitals

Purpose

To evaluate the clinical outcomes and safety of tigecycline (TGC) plus cefoperazone/sulbactam (CPS) or TGC monotherapy in patients with hospital-acquired pneumonia (HAP) caused by Carbapenem-Resistant Acinetobacter baumannii (CRAB).

Methods

This was a retrospective analysis of multicenter data from 62 Chinese hospitals with CRAB HAP. Risk factors for receiving TGC with CPS therapy and predictors of mortality were assessed using multivariate logistic and Cox regression analyses, respectively. Propensity score matching (PSM) evaluated the efficacy and safety of antimicrobial regimens.

Results

A total of the 180 patients were included, with 95 receiving TGC monotherapy and 85 receiving combination therapy. Multivariate logistic regression analysis revealed that older age (P = 0.011), and intensive care unit (ICU) admission (P = 0.007) were significant risk factors for combination therapy. Multivariate Cox regression demonstrated that combination therapy was associated with a significantly higher risk of 90-day mortality (P = 0.031). Patients in the standard-dose TGC (SDT) plus CPS subgroup had significantly higher rates of SOFA scores ≥ 7 (P = 0.009) and MV used (P = 0.028), as well as higher 30-/90-day mortality compared to high-dose TGC (HDT) plus CPS group. TGC plus CPS significantly reduced CRP levels (P = 0.009), while the variations in ALT, TBIL, Cr, Hb, and PLT levels did not differ between different antimicrobial regimens after PSM.

Conclusion

HDT and CPS combination therapy was more effective in patients with advanced age and more severe condition. Safety profiles of different antimicrobial regimens were similar with liver, kidneys, and coagulation functions.

Multicenter evaluation of activity of aztreonam in combination with avibactam, relebactam, and vaborbactam against metallo-β-lactamase-producing carbapenem-resistant gram-negative bacilli

Treatment options for carbapenem-resistant gram-negative bacilli (CR-GNB), especially metallo-β-lactamase (MBL)-producing CR-GNB, are limited. Aztreonam (ATM) in combination with avibactam (AVI) has shown potential for treating MBL-producing carbapenem-resistant Enterobacterales (CREs) and Stenotrophomonas maltophilia. However, data on ATM in combination with other β-lactamase inhibitors (BLIs) are limited. We performed a multicenter study to evaluate the in vitro activities of ATM in combination with AVI, vaborbactam (VAB), relebactam (REL), tazobactam (TAZ) as well as with their commercially available formulations against CREs and S. maltophilia using broth microdilution. AVI restored ATM activity for MBL-producing CREs (ATM: 9.8% vs ATM-AVI: 78.0%) and S. maltophilia (ATM: 0% vs ATM-AVI: 93.3%). REL also moderately restored activity of ATM in MBL-producing CREs (ATM: 9.8% vs ATM-REL: 42.7%) and S. maltophilia (ATM: 0% vs ATM-REL: 68.9%). VAB and TAZ demonstrated very limited effect on the activity of ATM against CR-GNB evaluated. The combination of ATM with ceftazidime-AVI (CAZ-AVI) demonstrated maximum activity against CREs. Although ATM-CAZ-AVI is the most potent regimen available for CREs and S. maltophilia, ATM-IMI-REL might be a reasonable alternative.

In vitro activity of cefepime-enmetazobactam on carbapenem-resistant gram negatives

OBJECTIVES

Cefepime-enmetazobactam is a new β-lactam/βlactamase inhibitor combination with broad-spectrum activity against multidrug-resistant Enterobacterales, including extended-spectrum β-lactamase producers. This study evaluated the in vitro activity of cefepime-enmetazobactam towards a collection of carbapenem-resistant Enterobacterales (CRE), Pseudomonas aeruginosa and Acinetobacter baumannii compared to the other β-lactam/β-lactamase inhibitor combinations.

METHODS

The MIC of cefepime, cefepime-enmetazobactam, ceftazidime, ceftazidime-avibactam, meropenem, meropenem-vaborbactam, imipenem, imipenem-relebactam, and ertapenem were determined by broth microdilution on 2212 CRE, including 2089 carbapenemase producers (1000 OXA-48-like, 49 KPC, 697 NDM, 180 VIM, 1 IMP, 9 IMI, and 158 multiple carbapenemases) and 123 CRE that do not produce carbapenemase received at the French National Reference Centre (from March 1, 2023 to August 31, 2023), 50 P. aeruginosa, and 30 A. baumannii. All strains were fully sequenced.

RESULTS

We confirmed the absence of inhibitory activity of enmetazobactam towards metallo-β-lactamases. Cefepime-enmetazobactam and ceftazidime-avibactam exhibited a similar susceptibility (96.7% vs. 99.5%, respectively) on OXA-48-producers. Cefepime-enmetazobactam exhibited 66.9% and 63.3% susceptibility for CRE non-EPC and KPC, whereas those rates rose to 96.7%/95.9%, 93.4%/95.9%, and 95.9%/98.0% for ceftazidime-avibactam, imipenem-relebactam, and meropenem-vaborbactam, respectively. Low MICs (≤0.25 mg/L) were obtained for ceftazidime-avibactam-resistant KPC variants. Cefepime-enmetazobactam did not display a significant added value when compared with cefepime alone on Pseudomonas aeruginosa and Acinetobacter baumannii.

DISCUSSION

OXA-48 producers displayed high susceptibility to cefepime-enmetazobactam, which is similar to ceftazidime-avibactam, including for OXA-48 producers that coproduce a ceftazidime hydrolyzing enzyme (extended-spectrum β-lactamases or AmpC). In vivo experiments have to be implemented to confirm if cefepime-enmetazobactam might be a relevant alternative to ceftazidime-avibactam for the treatment of infections caused by OXA-48 producers.

Bacteriophage vB_kpnS-Kpn15: Unveiling its potential triumph against extended-spectrum beta-lactamase-producing Klebsiella pneumoniae - Unraveling efficacy through innovative animal alternate models

Aim -To isolate bacteriophages targeting extended-spectrum beta-lactamase-producing K. pneumoniae and evaluate their effectiveness across diverse models, incorporating innovative alternatives in animal testing.

METHODS AND RESULTS

vB_kpnS-Kpn15 was isolated from sewage sample from Thane district. It produced a clear plaques on K. pneumoniae ATCC 700603. It has a flexible, non-contractile long tail and an icosahedral head and the Siphoviridae family of viruses in the order Caudovirales matched all of its structural criteria. Sequencing of vB_kpnS-Kpn15 revealed a 48,404 bp genome. The vB_KpnS-Kpn15 genome was found to contain 50 hypothetical proteins, of which 16 were found to possess different functions. The vB_KpnS-Kpn15 was also found to possess enzymes for its DNA synthesis. It was found to be lytic for the planktonic cells of K. pneumoniae and bactericidal for up to 48 h and potentially affected established K. pneumoniae biofilms. It demonstrated a broad host range and caused lytic zones on about 46 % of K. pneumoniae multi-drug resistant strains. In an in vitro wound and burn infection model, phage vB_kpnS-Kpn15 in combination with other phages resulted in successful cell proliferation and wound healing. Based on vB_kpnS-Kpn15's lytic properties, it can be incorporated in a bacteriophage cocktail to combat ESBL strains.

CONCLUSIONS

The phages isolated during this research are better candidates for phage therapy, and therefore provide new and exciting options for the successful control of antibiotic-resistant bacterial infections in the future. The utilization of animal alternative models in this study elucidates cellular proliferation and migration, underscoring its significance in screening novel drugs with potential applications in the treatment of wound and burn infections.

SIGNIFICANCE AND IMPACT OF THE RESEARCH

The findings of this research have implications for the creation of innovative, promising strategies to treat ESBL K. pneumoniae infections.

Mediastinitis caused by an NDM-1 Escherichia coli in a child with Dacron Sano shunt after pulmonary atresia with ventricular septal defect surgery treated with combination of aztreonam-avibactam

Carbapenem-resistant Enterobacterales are being reported increasingly and cause nosocomial infections, which may include postoperative mediastinitis. This paper reports a case of postoperative mediastinitis caused by an Escherichia coli NDM-1 carbapenemase producer in a 13-month-old boy with DiGeorge syndrome. The infection was managed with surgical debridement and antibiotherapy with aztreonam, ceftazidime-avibactam and IV fosfomycin for 6 weeks. The evolution was favourable, without relapse over 10 weeks of follow-up.

Monitoring of Pseudomonas aeruginosa mutational resistome dynamics using an enrichment panel for direct sequencing of clinical samples

BACKGROUND

Pseudomonas aeruginosa is a major cause of hospital-acquired and chronic infections, characterised by an extraordinary capacity to develop antimicrobial resistance through the selection of chromosomal mutations, leading to treatment failure. Here, we designed and tested a hybridisation-based capture system for the enrichment of genes of interest before sequencing to monitor resistant populations genomics directly from clinical samples.

METHODS

A panel for enrichment before sequencing of close to 200 genes related to P. aeruginosa antimicrobial resistance, multilocus sequence typing, mutability or virulence was designed, synthesised (KAPA HyperCap, Roche) and initially validated in vitro using a multidrug-resistant ST175 isolate and representative isolates from major P. aeruginosa clades. In vivo testing included ventilator associated pneumonia by MDR P. aeruginosa in ICU (3-10 sequential samples from 3 patients) and chronic respiratory infection by hypermutable P. aeruginosa in cystic fibrosis (8 sequential samples from a single patient covering a 4-year period). Results from direct sequencing with the enrichment panel were compared with those of whole genome sequencing (WGS) and phenotypic profiling of 10 isolated colonies per sample.

FINDINGS

In vitro assays confirmed the selectivity of the enrichment panel and the correct identification of the vast mutational resistome of ST175, including specific mutations even when introduced in a 1:100 proportion. In vivo performance was at least equivalent to sequencing 10 colonies per sample, including the accurate identification of the sequence types and the basal and acquired mutational resistome. To note, specific resistance mutations, such as those in ampC leading to resistance to novel β-lactams, could be traced even at frequencies of 1%. Moreover, the coselection of mutator populations and antibiotic resistance mutations, predicted in theoretical and in vitro studies, was evidenced in vivo.

INTERPRETATION

This proof-of-concept study demonstrates that resistance genomics of P. aeruginosa can be analysed directly from clinical samples, determining not only a considerable reduction in turnaround time and cost from a diagnostics perspective, but also an unprecedented potency for accurate monitoring of in vivo population dynamics in bacterial infections.

FUNDING

Instituto de Salud Carlos III, Ministerio de Ciencia e Innovación and Unión Europea-NextGenerationEU.

Recent Trends in Therapeutic Drug Monitoring of Peptide Antibiotics

Antimicrobial peptides take a specific position in the field of antibiotics (ATBs), however, from a large number of available molecules only a few of them were approved and are used in clinics. These therapeutic modalities play a crucial role in the management of diseases caused by multidrug-resistant bacterial pathogens and represent the last-line therapy for bacterial infections. Therefore, there is a demand for a rationale use of such ATBs based on optimization of the dosing strategy to minimize the risk of resistance and ensure the sustainable efficacy of the drug in real clinical practice. Therapeutic drug monitoring, as a measurement of drug concentration in the body fluids or tissues, results in the optimization of the patient´s medication and therapy outcome. This strategy is beneficial and could result in tailored therapy for different types of infection and the prolongation of the use and efficacy of ATBs in hospitals. This review paper provides an actual overview of approved antimicrobial peptides used in clinical practice and covers current trends in their analysis by convenient and advanced methodologies used for their identification and/or quantitation in biological matrices for therapeutic drug monitoring purposes. Special emphasis is given to the methods with perspective clinical outcomes.

Measuring the Direct Medical Costs of Hospital-Onset Infections Using an Analogy Costing Framework

BACKGROUND

The majority of recent estimates on the direct medical cost attributable to hospital-onset infections (HOIs) has focused on device- or procedure-associated HOIs. The attributable costs of HOIs that are not associated with device use or procedures have not been extensively studied.

OBJECTIVE

We developed simulation models of attributable cost for 16 HOIs and estimated the total direct medical cost, including nondevice-related HOIs in the USA for 2011 and 2015.

DATA AND METHODS

We used total discharge costs associated with HOI-related hospitalization from the National Inpatient Sample and applied an analogy costing methodology to develop simulation models of the costs attributable to HOIs. The mean attributable cost estimate from the simulation analysis was then multiplied by previously published estimates of the number of HOIs for 2011 and 2015 to generate national estimates of direct medical costs.

RESULTS

After adjusting all estimates to 2017 US dollars, attributable cost estimates for select nondevice-related infections attributable cost estimates ranged from $7661 for ear, eye, nose, throat, and mouth (EENTM) infections to $27,709 for cardiovascular system infections in 2011; and from $8394 for EENTM to $26,445 for central nervous system infections in 2016 (based on 2015 incidence data). The national direct medical costs for all HOIs were $14.6 billion in 2011 and $12.1 billion in 2016. Nondevice- and nonprocedure-associated HOIs comprise approximately 26-28% of total HOI costs.

CONCLUSION

Results suggest that nondevice- and nonprocedure-related HOIs result in considerable costs to the healthcare system.