Treatment of Infections by OXA-48-Producing Enterobacteriaceae

Advancements in Immunology and Microbiology Research: A Comprehensive Exploration of Key Areas

Immunology and microbiology research has witnessed remarkable growth and innovation globally, playing a pivotal role in advancing our understanding of immune mechanisms, disease pathogenesis, and therapeutic interventions. This manuscript presents a comprehensive exploration of the key areas in immunology research, spanning from the utilisation of bacterial proteins as antibody reagents to the intricate realms of clinical immunology and disease management. The utilisation of bacterial immunoglobulin-binding proteins (IBPs), including protein A (SpA), protein G (SpG), and protein L (SpL), has revolutionised serological diagnostics, showing promise in early disease detection and precision medicine. Microbiological studies have shed light on antimicrobial resistance patterns, particularly the emergence of extended-spectrum beta-lactamases (ESBLs), guiding antimicrobial stewardship programmes and informing therapeutic strategies. Clinical immunology research has elucidated the molecular pathways underlying immune-mediated disorders, resulting in tailored management strategies for conditions such as severe combined immunodeficiency (SCID), neuropsychiatric systemic lupus erythematosus (NPSLE), etc. Additionally, significant efforts in vaccine development against tuberculosis and HIV are highlighted, underscoring the ongoing global pursuit of effective preventive measures against these infectious diseases. In summary, immunology and microbiology research have provided significant contributions to global healthcare, fostering collaboration, innovation, and improved patient outcomes.

Non-KPC Attributes of Newer β-lactam/β-lactamase Inhibitors, Part 1: Enterobacterales and Pseudomonas aeruginosa

Gram-negative antibiotic resistance continues to grow as a global problem due to the evolution and spread of β-lactamases. The early β-lactamase inhibitors (BLIs) are characterized by spectra limited to class A β-lactamases and ineffective against carbapenemases and most extended spectrum β-lactamases. In order to address this therapeutic need, newer BLIs were developed with the goal of treating carbapenemase producing, carbapenem resistant organisms (CRO), specifically targeting the Klebsiella pneumoniae carbapenemase (KPC). These BL/BLI combination drugs, avibactam/avibactam, meropenem/vaborbactam, and imipenem/relebactam, have proven to be indispensable tools in this effort. However, non-KPC mechanisms of resistance are rising in prevalence and increasingly challenging to treat. It is critical for clinicians to understand the unique spectra of these BL/BLIs with respect to non-KPC CRO. In Part 1of this 2-part series, we describe the non-KPC attributes of the newer BL/BLIs with a focus on utility against Enterobacterales and Pseudomonas aeruginosa.

Carbapenem-resistant Enterobacterales in wastewater resources and healthy carriers: A survey in Iran

The carbapenem-resistant Enterobacterales (CRE) pose a pressing public health concern. Here, we investigated the frequency of CRE bacteria, carbapenemase-encoding genes, and the molecular epidemiology of carbapenemase-resistant Escherichia coli in wastewater resources and healthy carriers in Iran. Out of 617 Enterobacterales bacteria, 24% were carbapenem-resistant. The prevalence of CRE bacteria in livestock and poultry wastewater at 34% and hospital wastewater at 33% was significantly higher (P ≤ 0.05) than those in healthy carriers and municipal wastewater at 22 and 17%, respectively. The overall colonization rate of CRE in healthy individuals was 22%. Regarding individual Enterobacterales species, the following percentages of isolates were found to be CRE: E. coli (18%), Citrobacter spp. (24%), Klebsiella pneumoniae (28%), Proteus spp. (40%), Enterobacter spp. (25%), Yersinia spp. (17%), Hafnia spp. (31%), Providencia spp. (21%), and Serratia spp. (36%). The blaOXA-48 gene was detected in 97% of CRE isolates, while the blaNDM and blaVIM genes were detected in 24 and 3% of isolates, respectively. The B2 phylogroup was the most prominent group identified in carbapenem-resistant E. coli isolates, accounting for 80% of isolates. High prevalence of CRE with transmissible carbapenemase genes among healthy people and wastewater in Iran underscores the need for assertive measures to prevent further dissemination.

A computational odyssey: uncovering classical β-lactamase inhibitors in dry fruits

In the antibacterial arsenal, β-lactams have held a prominent position, but increasing resistance due to unauthorized use and genetic factors requires new strategies. Combining β-lactamase inhibitors with broad-spectrum β-lactams proves effective in combating this resistance. ESBL producers demand new inhibitors, leading to the exploration of plant-derived secondary metabolites for potent β-lactam antibiotics or alternative inhibitors. Using virtual screening, molecular docking, ADMET analysis, and molecular dynamic simulation, this study actively analyzed the inhibitory activity of figs, cashews, walnuts, and peanuts against SHV-1, NDM-1, KPC-2, and OXA-48 β-lactamases. Using AutoDock Vina, the docking affinities of various compounds for target enzymes were initially screened, revealing 12 bioactive compounds with higher affinities for the target enzymes compared to Avibactam and Tazobactam. Top-scoring metabolites, including Oleanolic acid, Protocatechuic acid, and Tannin, were subjected to MD simulation studies to further analyze the stability of the docked complexes using WebGro. The simulation coordinates, in terms of RMSD, RMSF, SASA, Rg, and hydrogen bonds formed, showed that these phytocompounds are stable enough to retain in the active sites at various orientations. The PCA and FEL analysis also showed the stability of the dynamic motion of Cα residues of phytochemical-bound enzymes. The pharmacokinetic analysis of the top phytochemicals was performed to analyze their bioavailability and toxicity. This study provides new insights into the therapeutic potential of phytochemicals of selected dry fruits and contributes to future experimental studies to identify βL inhibitors from plants.Communicated by Ramaswamy H. Sarma.

Combination Therapy for OXA-48 Carbapenemase-Producing Klebsiella Pneumoniae Bloodstream Infections in Premature Infant: A Case Report and Literature Review

The prevalence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has been increasing in recent years. Chinese Infectious Disease Surveillance of Pediatrics (ISPED) showed that in 2022, its resistance rate to meropenem was 18.5%. However, there is limited data available on the treatment of CRKP infection in neonates. In this study, we present a case involving a premature infant infected with OXA-48-producing Klebsiella pneumoniae. The combined susceptibility test revealed a significant synergistic effect between ceftazidime-avibactam(CAZ-AVI), and aztreonam(ATM). The infection was successfully treated with a combination of CAZ-AVI, ATM, and fosfomycin. This case represents the first reported instance of sepsis in a premature infant caused by OXA-48-producing Klebsiella pneumoniae in China. The objective of our study is to evaluate the effectiveness and safety of combination therapy in treating CRKP infections in premature infants. We hope that the findings of this study will provide valuable insights for clinicians in their treatment approach.

In vitro activity of ceftazidime-avibactam and comparators against OXA-48-like Enterobacterales collected between 2016 and 2020

Oxacillinases (OXA)-48-like β-lactamases are one of the most common resistance determinants among carbapenem-resistant Enterobacterales reported globally. Moreover, there is no standard treatment available against organisms producing OXA-48-like enzymes, and they are sometimes difficult to detect, making treatment challenging. The objective of this study was to evaluate the distribution and antimicrobial susceptibility of blaOXA-48-like Enterobacterales isolates against ceftazidime-avibactam (CAZ-AVI) and a panel of comparators collected worldwide from 2016 to 2020 as a part of the Antimicrobial Testing Leadership and Surveillance program. Among all the Enterobacterales isolates collected, 1.8% (1,690/94,052) carried blaOXA-48-like, and a majority of those were identified as K. pneumoniae (86.5%, 1,462/1,690). Among all the blaOXA-48-like isolates, 88.9% (1,502/1,690) were extended-spectrum β-lactamase (ESBL)-positive, 20.7% (350/1,690) were metallo-β-lactamase (MBL)-positive, and 8.9% (150/1,690) were ESBL- and MBL-negative. There were 10 different variants of the OXA-48-like family of enzymes detected, with the major variant being blaOXA-48 (50.2%, 848/1,690), blaOXA-232 (29.3%, 496/1,690), and blaOXA-181 (18.0%, 304/1,690). Overall, all the blaOXA-48-like isolates showed a susceptibility of 78.6% to CAZ-AVI. Importantly, high susceptibility to CAZ-AVI was shown by all the blaOXA-48 type, MBL-negative isolates (n = 1,380, ≥99.0%), and all the MBL-negative isolates (n = 1,300, ≥97.6%) of the major variants (blaOXA-48, blaOXA-232, and blaOXA-181) studied. Among the comparator agents, all isolates showed good susceptibility to only tigecycline (>95.0%) and colistin (>78.6%). Considering the limited treatment options available, CAZ-AVI could be considered as a potential treatment option against blaOXA-48-like Enterobacterales. However, routine surveillance and appropriate stewardship strategies for these organisms may help identify emerging resistance mechanisms and effective treatment of infections.

IMPORTANCE

Resistance to carbapenems among Enterobacterales is often due to the production of enzymes that are members of the oxacillinases (OXA)-48-like family. These organisms can also be resistant to other classes of drugs and are difficult to identify and treat. This study evaluated the activity of the drug ceftazidime-avibactam (CAZ-AVI) and other comparator agents against a global collection of Enterobacterales that produce OXA-48-like enzymes. CAZ-AVI was active against blaOXA-48-like Enterobacterales, and only colistin and tigecycline were similarly active among the comparator agents, highlighting the limited treatment options against these organisms. Continued surveillance of the distribution of these OXA 48-like producing Enterobacterales and monitoring of resistance patterns along with the implementation of antimicrobial stewardship measures to guide antibiotic use and appropriate treatment are necessary to avoid drug resistance among these organisms.

Assessing O.K.N.V.I. RESIST‑5 performance for post‑mortem biological samples: A prospective pilot study

In recent years, the emergence of carbapenem-resistant strains has been increasing worldwide, including in Romania. Rapid tests for post-mortem examinations have been researched and currently have several applications. In the present study, we aimed to test the performance of O.K.N.V.I. RESIST-5 tests on impure post-mortem biological samples compared with a standard of pure cultures. When a death occurs during hospitalization and the issue of malpractice arises, the medico-legal practice would benefit from rapid tests applicable to post-mortem samples. Thus, detection and differentiation of the five targeted carbapenemases, namely oxacilinase-48, Klebsiella pneumoniae carbapenemase, New Delhi metallo-β-lactamase, Verona integron-encoded metallo-β-lactamase and imipenemase, could be useful in guiding sampling for third-party microbiological assessment and could also be an asset from an epidemiological standpoint. The present prospective and observational pilot study included medico-legal autopsy cases performed at Mina Minovici National Institute of Legal Medicine (Romania) between June and July 2022. A total of two sets of O.K.N.V.I. RESIST-5 tests were performed: Test I, which was performed on-site from biological samples obtained during autopsy; and Test II, which was performed on pure cultures after sample inoculation and incubation. Total of 39 O.K.N.V.I. RESIST-5 rapid tests were performed on 19 biological samples, at least one sample per case. The O.K.N.V.I. RESIST-5 tests performed on-site showed an overall sensitivity of 92.3% with a 100% specificity. The results obtained through rapid tests using post-mortem impure samples were comparable to the results obtained from sample cultures with good sensitivity and specificity. Through post-mortem screening for carbapenem resistance, it would be possible to narrow down the number of cases that require further bacteriological assessment.

Comparison of genotypic and phenotypic antimicrobial profile in carbapenemases producing Klebsiella pneumoniae

BACKGROUND AND AIM

Prompt administration of appropriate antibiotic therapy is crucial in improving outcomes, particularly in cases sustained by multi-drug resistant strains. Although phenotypic antimicrobial susceptibility testing (AST) represents the gold standard to address antibiotics treatment, the long time required to obtained affordable results could negatively affect the prognosis. In contrast, rapid genotypic AST provide essential information for treatment and surveillance program. In order to evaluate the potential adoption of rapid AST in clinical routine, we compared the genotypic and phenotypic antimicrobial profiles of different K.pneumoniae strains, characterized by different expression of carbapenemases-encoding genes.

METHODS

A set of 109 strains of Cr-Kp were tested for the antimicrobial drugs by the automatized Vitek II system and, in parallel, to the new combination of β-lactams/β-lactamases inhibitors (BL/BLI) by Etest. An antimicrobial resistance index (ARI) was calculated for each strain, assigning each 1 or 0 points based on observed resistance/susceptibility, and dividing the total by the number of antibiotics tested. Kruskal-Wallis test, followed by Dunn's post hoc test (Bonferroni correction), were used to compare quantitative variables among resistance gene subgroups.

RESULTS

We observed a higher ARI score in KPC/OXA-48 strains, similar profile in KPC alone and KPC/CTX-M groups and a significant lower resistance in no-carbapenemases-producing group. Same trend was observed in AST for BL/BLI.

CONCLUSIONS

These preliminary results showed a close link between genotypic and phenotypic AST, supporting the adoption of rapid AST in cases of severe infections, ensuring to saving time and providing, the surveillance of MDR strains and improving stewardship programs.

High prevalence of OXA-48-like and NDM carbapenemases among carbapenem resistant Klebsiella pneumoniae of clinical origin from Iran

Background and Objectives

Klebsiella pneumoniae is increasingly developing resistance to last-resort antibiotics such as carbapenems. This study aimed to investigate the dissemination of common carbapenemase encoding genes among 48 clinical isolates of carbapenem-resistant Klebsiella pneumoniae (CRKP).

Materials and Methods

Antimicrobial susceptibility testing was performed by broth dilution and disc diffusion methods. The phenotypic evaluation of carbapenemase production was performed by using Modified Carbapenem Inactivation Method. Presence of carbapenemase encoding genes blaKPC, blaNDM, blaOXA-48-like , blaIMP, and blaVIM was screened by PCR.

Results

Overall, carbapenemases were produced in all CRKP isolates. The blaOXA-48-like and blaNDM were the most prevalent genes detected among all and 66.6% (n=32) of CRKP isolates respectively. The blaVIM was detected in only one isolate co-harboring NDM and OXA-48-like carbapenemases. The blaKPC and blaIMP genes were not identified in any of the isolates. While tigecycline was the most active agent against CRKP isolates with low resistance rate (4.1%), high rate of resistance was observed to colistin (66.6%), amikacin (79%) and most of other tested antimicrobials.

Conclusion

Our results revealed predominant prevalence of OXA-48-like and NDM carbapenemases among CRKP clinical isolates. High rate of resistance to last-resort agents such as colistin among CRKP isolates is a source of great concern.

Hospital-Acquired Infections Caused by Carbapenem-Resistant Enterobacteriaceae: An Observational Study

Worldwide, hospital-acquired infections (HAIs) are continuously rising within healthcare settings, leading to high mortality and morbidity rates. Many hospitals have reported the spread of carbapenemases globally, specifically within the E. coli and K. pneumoniae species. This study was aimed at analyzing the state of hospital-acquired, carbapenem-resistant E. coli and K. pneumoniae in the United Kingdom between 2009 and 2021. Moreover, the study analyzed the most efficacious approaches to patient management for controlling the carbapenem-resistant Enterobacteriaceae (CRE) spread. Initially, 1094 articles were identified as relevant for screening, and among them, 49 papers were eligible for full-text screening, with a total of 14 articles meeting the inclusion criteria. The information was recorded from published articles through PubMed, the Web of Science, Scopus, Science Direct, and the Cochrane library and was used to search for hospital-acquired carbapenem-resistant E. coli and K pneumoniae in the UK between 2009 and 2021, in order to evaluate the spread of CRE in hospitals. The total number of carbapenem-resistant E. coli was 1083 and this was 2053 for carbapenem-resistant K. pneumoniae in more than 63 UK hospitals. KPC was the dominant carbapenemase produced by K. pneumoniae. The results showed that the treatment options considered depended on the type of carbapenemase produced; K. pneumoniae showed more resistance to a treatment options, i.e., Colistin, than the other carbapenemase. The current state of the UK is at minimal risk for a CRE outbreak; however, appropriate treatment and infection control measures are highly required to prevent this CRE spread at the regional and global levels. The present study findings have an important message for physicians, healthcare workers, and policymakers about hospital-acquired carbapenem-resistant E. coli and K. pneumoniae spread and approaches to patient management.

Uropathogenic Escherichia coli endeavors: an insight into the characteristic features, resistance mechanism, and treatment choice

Uropathogenic Escherichia coli (UPEC) are the strains diverted from the intestinal status and account mainly for uropathogenicity. This pathotype has gained specifications in structure and virulence to turn into a competent uropathogenic organism. Biofilm formation and antibiotic resistance play an important role in the organism's persistence in the urinary tract. Increased consumption of carbapenem prescribed for multidrug-resistant (MDR) and Extended-spectrum-beta lactamase (ESBL)-producing UPECs, has added to the expansion of resistance. The World Health Organization (WHO) and Centre for Disease Control (CDC) placed the Carbapenem-resistant Enterobacteriaceae (CRE) on their treatment priority lists. Understanding both patterns of pathogenicity, and multiple drug resistance may provide guidance for the rational use of anti-bacterial agents in the clinic. Developing an effective vaccine, adherence-inhibiting compounds, cranberry juice, and probiotics are non-antibiotical approaches proposed for the treatment of drug-resistant UTIs. We aimed to review the distinguishing characteristics, current therapeutic options and promising non-antibiotical approaches against ESBL-producing and CRE UPECs.

Characterisation of OXA-48-like carbapenemases in Escherichia coli and Klebsiella pneumoniae from North India

The oxacillinase-48 (OXA-48)-like carbapenemases are class D β-lactamases and increasingly reported in Enterobacterial species. The detection of these carbapenemases is challenging and little information is available on the epidemiology and plasmid characteristics of OXA-48-like carbapenemase producers. We detected the presence of OXA-48-like carbapenemases in 500 clinical isolates of Escherichia coli and Klebsiella pneumoniae, followed by detection of other carbapenemases, extended spectrum β-lactamases (ESBLs) and 16S rRNA methyltransferases in OXA-48 producers. Clonal relatedness was studied using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Finally, plasmid characterisation was performed through conjugation experiment, S1-PFGE and Southern hybridisation. Around 40% of E. coli and K. pneumoniae isolates harboured OXA-48-like β-lactamases. Two OXA-48 allele variants, OXA-232 and OXA-181 were detected in our study. OXA-48 producers co-harbored diverse drug-resistant genes belonging to other classes of carbapenemases, ESBLs and 16S rRNA methyltransferases. OXA-48-like carbapenemase producers exhibited high clonal diversity. Bla OXA-48 carrying plasmids were conjugative, untypable and their size was ~ 45 kb and ~ 104.5 kb in E. coli and K. pneumoniae respectively. In conclusion, OXA-48-like carbapenemases have emerged as major cause of carbapenem resistance in Enterobacteriaceae and probably still being under reported. Strict surveillance and adequate detection methods are needed to prevent the dissemination of OXA-48-like carbapenemases.

Carbapenemase-producing Klebsiella pneumoniae in community settings: a cross-sectional study in Belgrade, Serbia

Aim: The types of carbapenemases and clonal relatedness among community isolates of carbapenemase-producing Klebsiella pneumoniae in Belgrade, Serbia, were determined. Materials & methods: During the period 2016-2020, K. pneumoniae community isolates were screened for carbapenemases, and carbapenemase production was confirmed by multiplex PCR. Clonality was determined based on genetic profiles obtained by enterobacterial repetitive intergenic consensus PCR. Results: Carbapenemase genes were detected in 114 of 4800 isolates (2.4%). The most frequent gene was blaOXA-48-like. Most isolates (70.5%) were grouped in ten clusters. Cluster 11 contained 16.4% of all blaOXA-48-like-positive isolates, and all blaKPC-positive isolates were grouped in one cluster. Conclusion: Laboratory-based detection and surveillance are highly recommended in order to control the spread of resistance in community settings.

Clinical Management of a Pandrug-Resistant OXA-48 Klebsiella pneumoniae Infection in the Pediatric Intensive Care Unit

Background: Carbapenem-resistant Klebsiella pneumoniae (CRKP) is one of the serious forms of health care-associated infection. Pan-drug resistant (PDR) CRKP infections can cause severe infections. Mortality and treatment costs in the pediatric intensive care unit (PICU) are high. This study aims to share our experience regarding the treatment of oxacillinase (OXA)-48-positive PDR-CRKP infection in our 20-bed tertiary PICU with isolated rooms and 1 nurse for every 2-3 patients. Methods: Patient demographic characteristics, underlying diseases, previous infections, source of infection PDR-CRKP, treatment modalities, measures used, and outcomes were recorded. Findings: Eleven patients (eight men and three women) were found to have PDR OXA-48-positive CRKP. Because of the simultaneous detection of PDR-CRKP in three patients and the rapid spread of the disease, it was classified as a clinical outbreak, and strict infection control measures were taken. Combination therapy with double carbapenemase (meropenem and imipenem), amikacin, colistin, and tigecycline was used for treatment. The mean duration of treatment and isolation was 15.7 and 65.4 days, respectively. No treatment-related complication was observed, only one patient died, and the mortality rate was 9%. Conclusions: This severe clinical outbreak can be successfully treated with effective treatment with combined antibiotics and strict adherence to infection control measures. ClinicalTrial.gov ID: 28/01/2022 - 1/5.

OXA-48 Carbapenemase-Producing Salmonella typhimurium Nosocomial Bacteremia in the Intensive Care Unit: A Case Report and Review of the Literature

Salmonella enterica serovar Typhimurium is a gram-negative bacterium mainly involved in foodborne diseases. Several pathways of antimicrobial resistance have been recently identified in this strain. This article reports a case of a patient hospitalized in intensive care who underwent emergency trauma surgery. During his hospitalization, he developed a nosocomial bacteremia from a surgical wound infection. The cytobacteriological examination of the surgical site and the blood culture isolated Salmonella spp. susceptible to third-generation cephalosporins, resistant to ertapenem, and with decreased sensitivity to imipenem. The carbapenemase test was positive for blaOXA-48. The serotyping identified Salmonella enterica serovar Typhimurium. The patient's response to antibiotics was favorable.

Phenotypes, genotypes and breakpoints: an assessment of β-lactam/β-lactamase inhibitor combinations against OXA-48

BACKGROUND

Two of the three recently approved β-lactam agent (BL)/β-lactamase inhibitor (BLI) combinations have higher CLSI susceptibility breakpoints (ceftazidime/avibactam 8 mg/L; meropenem/vaborbactam 4 mg/L) compared with the BL alone (ceftazidime 4 mg/L; meropenem 1 mg/L). This can lead to a therapeutic grey area on susceptibility reports depending on resistance mechanism. For instance, a meropenem-resistant OXA-48 isolate (MIC 4 mg/L) may appear as meropenem/vaborbactam-susceptible (MIC 4 mg/L) despite vaborbactam's lack of OXA-48 inhibitory activity.

METHODS

OXA-48-positive (n = 51) and OXA-48-negative (KPC, n = 5; Klebsiella pneumoniae wild-type, n = 1) Enterobacterales were utilized. Susceptibility tests (broth microdilution) were conducted with ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam, as well as their respective BL partner. Antimicrobial activity of all six agents was evaluated in the murine neutropenic thigh model using clinically relevant exposures. Efficacy was assessed as the change in bacterial growth at 24 h, compared with 0 h controls.

RESULTS

On average, the three BL/BLI agents resulted in robust bacteria killing among OXA-48-negative isolates. Among OXA-48-positive isolates, poor in vivo activity with imipenem/relebactam was concordant with its resistant phenotypic profile. Variable meropenem/vaborbactam activity was observed among isolates with a 'susceptible' MIC of 4 mg/L. Only 30% (7/23) of isolates at meropenem/vaborbactam MICs of 2 and 4 mg/L met the ≥1-log bacterial reduction threshold predictive of clinical efficacy in serious infections. In contrast, ceftazidime/avibactam resulted in marked bacterial density reduction across the range of MICs, and 96% (49/51) of isolates exceeded the ≥1-log bacterial reduction threshold.

CONCLUSIONS

Data demonstrate that current imipenem/relebactam and ceftazidime/avibactam CLSI breakpoints are appropriate. Data also suggest that higher meropenem/vaborbactam breakpoints relative to meropenem can translate to potentially poor clinical outcomes in patients infected with OXA-48-harbouring isolates.

Antibiotic Susceptibility Patterns for Carbapenem-Resistant Enterobacteriaceae

Carbapenem is a broad-spectrum beta-lactam antibiotic considered the last choice for the treatment of antibiotic-resistant Gram-negative bacteria. Thus, the increasing rate of carbapenem resistance (CR) in Enterobacteriaceae is an urgent public health threat. This study aimed to evaluate the antibiotic susceptibility pattern of carbapenem-resistant Enterobacteriaceae (CRE) to new and old antibiotics. In this study, Klebsiella pneumoniae, E. coli, and Enterobacter spp. were collected from 10 hospitals in Iran for one year. CRE is recognized by resistance to meropenem and/or imipenem disk after identification of the collected bacteria. Antibiotic susceptibility of CRE against fosfomycin, rifampin, metronidazole, tigecycline, and aztreonam was detected by disk diffusion method and colistin by MIC. In this study, 1222 E. coli, 696 K. pneumoniae, and 621 Enterobacter spp. were collected from 10 hospitals in Iran in one year. Fifty-four E. coli (4.4%), 84 K. pneumoniae (12%), and 51 Enterobacter spp. (8.2%) were CRE. All CRE strains were resistant to metronidazole and rifampicin. Tigecycline has the highest sensitivity on CRE and levofloxacin for Enterobacter spp. Tigecycline showed an acceptable effectiveness rate of sensitivity on the CRE strain. Therefore, we suggest that clinicians consider this valuable antibiotic to treat CRE.

Prevalence of Carbapenem-Resistant Enterobacteriaceae in Western Saudi Arabia and Increasing Trends in the Antimicrobial Resistance of Enterobacteriaceae

PURPOSE

 The aim of the study is to estimate the prevalence rate of carbapenem-resistant Enterobacteriaceae (CRE) and to determine the types of carbapenemase genes present in patients admitted to King Abdulaziz Medical City (KAMC-J) and King Abdulaziz University Hospital (KAUH), both in Jeddah, Saudi Arabia.

METHODS

 A total of 180 isolates were analyzed which were included on the basis of retrospective chart review of patients from KAMC-J and KAUH between 1^st April 2017 to 30^th March 2019. The prevalence of carbapenemase genes ( ^blaIMP, ^blaVIM, ^blaKPC, ^blaNDM-1, and ^blaOXA-48) was evaluated by Xpert® Carba-R (Cepheid, Sunnyvale, CA, USA). We assessed the CRE prevalence and described their susceptibility to antimicrobial agents based on antibiogram reports.  Results: Klebsiella pneumoniae showed a higher frequency of ^bla OXA-48 (79%) than ^bla NDM (11.7%) genes (p=0.007). The CRE prevalence in KAUH was 8% in 2017 and increased to 13% in 2018. In KAMC-J, the prevalence was 57% in 2018 and 61% in 2019. K. pneumoniae was found to be the most frequently isolated causative organism followed by Escherichia coli . The  ^bla OXA-48 (76.1%) gene was predominant among overall isolates followed by ^bla NDM (13.9%); both genes coexisted in 6.1% of the isolates.

CONCLUSION

 During the study period, the prevalence of CRE considerably rose in the two tertiary care institutions from western Saudi Arabia. In the CRE isolates, ^bla OXA-48 was discovered to be the most common gene. We recommend an antimicrobial resistance surveillance system to detect the emergence of resistant genes through use of new rapid diagnostic tests and monitor antimicrobial use in order to improve clinical outcomes of CRE infections given the severity of infection associated with the CRE isolates as well as the limited treatment options available.

Genetic diversity and prevalence of extended-spectrum beta-lactamase-producing Escherichia coli and Klebsiella pneumoniae in aquatic environments receiving untreated hospital effluents

The spread of extended-spectrum beta-lactamase (ESBL)-producing bacteria in the environment has been recognized as a challenge to public health. The aim of the present study was to assess the occurrence of ESBL-producing Escherichia coli and Klebsiella pneumoniae from selected water bodies receiving hospital effluents in Kerala, India. Nearly 69.8% of Enterobacteriaceae isolates were multi-drug resistant by the Kirby-Bauer disc diffusion method. The double disc synergy test was used to detect the ESBL production and the genes responsible for imparting resistance were detected by PCR. Conjugation experiments confirmed the mechanism of plasmid-mediated transfer of resistance. The prevalence of ESBL production in E. coli and K. pneumoniae was 49.2 and 46.8%, respectively. Among the ESBL-encoding genes, bla_CTX-M was the most prevalent group followed by bla_TEM, bla_OXA, bla_CMY, and bla_SHV. The results suggest that healthcare settings are one of the key contributors to the spread of ESBL-producing bacteria, not only through cross-transmission and ingestion of antibiotics but also through the discharge of waste without a proper treatment, leading to harmful effects on the aquatic environment. The high prevalence of ESBL-producing Enterobacteriaceae with resistance genes in public water bodies even post-treatment poses a serious threat.

Preferred β-lactone synthesis can explain high rate of false-negative results in the detection of OXA-48-like carbapenemases

The resistance to carbapenems is usually mediated by enzymes hydrolyzing β-lactam ring. Recently, an alternative way of the modification of the antibiotic, a β-lactone formation by OXA-48-like enzymes, in some carbapenems was identified. We focused our study on a deep analysis of OXA-48-like-producing Enterobacterales, especially strains showing poor hydrolytic activity. In this study, well characterized 74 isolates of Enterobacterales resistant to carbapenems were used. Carbapenemase activity was determined by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), liquid chromatography/mass spectrometry (LC-MS), Carba-NP test and modified Carbapenem Inactivation Method (mCIM). As meropenem-derived β-lactone possesses the same molecular weight as native meropenem (MW 383.46 g/mol), β-lactonization cannot be directly detected by MALDI-TOF MS. In the spectra, however, the peaks of m/z = 340.5 and 362.5 representing decarboxylated β-lactone and its sodium adduct were detected in 25 out of 35 OXA-48-like producers. In the rest 10 isolates, decarboxylated hydrolytic product (m/z = 358.5) and its sodium adduct (m/z = 380.5) have been detected. The peak of m/z = 362.5 was detected in 3 strains co-producing OXA-48-like and NDM-1 carbapenemases. The respective signal was identified in no strain producing class A or class B carbapenemase alone showing its specificity for OXA-48-like carbapenemases. Using LC-MS, we were able to identify meropenem-derived β-lactone directly according to the different retention time. All strains with a predominant β-lactone production showed negative results of Carba NP test. In this study, we have demonstrated that the strains producing OXA-48-like carbapenemases showing false-negative results using Carba NP test and MALDI-TOF MS preferentially produced meropenem-derived β-lactone. We also identified β-lactone-specific peak in MALDI-TOF MS spectra and demonstrated the ability of LC-MS to detect meropenem-derived β-lactone.

Clinical Risk Factors and Microbiological and Intestinal Characteristics of Carbapenemase-Producing Enterobacteriaceae Colonization and Subsequent Infection

Gastrointestinal colonization with carbapenem-resistant Enterobacteriaceae (CRE) is always a prerequisite for the development of translocated infections. Here, we sought to screen for fecal carriage of CRE and identify the risk factors for CRE colonization as well as subsequent translocated pneumonia in critically ill patients admitted to the intensive care unit (ICU) of a university hospital in China. We further focused on the intestinal flora composition and fecal metabolic profiles in CRE rectal colonization and translocated infection patients. Animal models of gastrointestinal colonization with a carbapenemase-producing Klebsiella pneumoniae (carbapenem-resistant K. pneumoniae [CRKP]) clinical isolate expressing green fluorescent protein (GFP) were established, and systemic infection was subsequently traced using an in vivo imaging system (IVIS). The intestinal barrier, inflammatory factors, and infiltrating immune cells were further investigated. In this study, we screened 54 patients hospitalized in the ICU with CRE rectal colonization, and 50% of the colonized patients developed CRE-associated pneumonia, in line with the significantly high mortality rate. Upon multivariate analysis, risk factors associated with subsequent pneumonia caused by CRE in patients with fecal colonization included enteral feeding and carbapenem exposure. Furthermore, CRKP colonization and translocated infection influenced the diversity and community composition of the intestinal microbiome. Downregulated propionate and butyrate probably play important and multiangle roles in regulating immune cell infiltration, inflammatory factor expression, and mucus and intestinal epithelial barrier integrity. Although the risk factors and intestinal biomarkers for subsequent infections among CRE-colonized patients were explored, further work is needed to elucidate the complicated mechanisms. IMPORTANCE Carbapenem-resistant Enterobacteriaceae have emerged as a major threat to modern medicine, and the spread of carbapenem-resistant Enterobacteriaceae is a clinical and public health problem. Gastrointestinal colonization by potential pathogens is always a prerequisite for the development of translocated infections, and there is a growing need to assess clinical risk factors and microbiological and intestinal characteristics to prevent the development of clinical infection by carbapenem-resistant Enterobacteriaceae.

First Isolates of OXA-48-Like Carbapenemase-Producing Enterobacteriaceae in A Specialized Cancer Center

BACKGROUND

OXA-48-like carbapenemases have been found in a growing and varied number of carbapenemase-producing Enterobacteriaceae (CPE) isolates, and they are spreading to several countries. Although this oxacillinase leads to weak resistance to carbapenems without affecting broad-spectrum cephalosporin activity, when they are associated with other resistance mechanisms, the level of resistance to these antibiotics may be significantly higher. This weak resistance against carbapenems and cephalosporins, along with the absence of other resistance mechanisms, could render OXA-48-like harboring isolates undetected in the laboratory routine. In addition, the lack of a specific screening test for this enzyme complicates the detection of these isolates. This report characterizes the first isolates of OXA-48-like CPE detected in our laboratory.

MATERIALS AND METHODS

The study was carried out at the Instituto Nacional de Enfermedades Neoplasicas, Lima - Peru, between March and December 2021. OXA-48-like CPE isolates were detected as part of the routine microbiological study, and clinical data were obtained by reviewing medical records. The automated microbiological system provides the bacterial identification and antimicrobial susceptibility profile by the dilution method. Additionally, the column chromatography test is used to detect carbapenemase enzymes, including OXA-48-like. Finally, the molecular identification of the OXA-48-like enzyme was carried out by Polymerase Chain Reaction PCR amplification for the bla_OXA-48-like.

RESULTS

Seven OXA-48-like CPE strains were isolated. Notably, in all cases, the automated system issued a minimum inhibitory concentration (MIC) of ≥1 ug/mL for ertapenem and a MIC of >64/4 ug/mL for piperacillin/tazobactam. In addition, resistance category to imipenem and meropenem was found (2/7), at least one indeterminate category for any of these carbapenems (5/7), and other serine β-lactamases such as Extended-spectrum beta-lactamases (3/7) and AmpC (3/7). The immunochromatographic study confirmed the presence of the OXA-48-like enzyme in all isolates, while class A and class B were ruled out for them. Finally, the multiplex PCR, for the five isolates that could be recovered, showed amplification for carbapenemase OXA-48-like, while none of the other carpabemases was amplified for class A or class B carbapenemase genes.

CONCLUSION

We confirm the emergence of OXA-48-like CPE isolates in our cancer center and highlight the need to implement surveillance and detection measures of these strains, for controlling their dissemination. We found practical and inexpensive methodologies for the detection of OXA-48-like CPE: (1) the finding of resistance to ertapenem and piperacillin/tazobactam in the antibiogram in the absence of class A and B carbapenemases, for screening and (2) immunochromatographic study, for confirmation.

Best practices: Appropriate use of the new β-lactam/β-lactamase inhibitor combinations, ceftazidime-avibactam and ceftolozane-tazobactam in South Africa

Antibiotic stewardship of hospital-acquired infections because of difficult-to-treat resistant (DTR) Gram-negative bacteria is a global challenge. Their increasing prevalence in South Africa has required a shift in prescribing in recent years towards colistin, an antibiotic of last resort. High toxicity levels and developing resistance to colistin are narrowing treatment options further. Recently, two new β-lactam/β-lactamase inhibitor combinations, ceftazidime-avibactam and ceftolozane-tazobactam were registered in South Africa, bringing hope of new options for management of these life-threatening infections. However, with increased use in the private sector, increasing levels of resistance to ceftazidime-avibactam are already being witnessed, putting their long-term viability as treatment options of last resort, in jeopardy. This review focuses on how these two vital new antibiotics should be stewarded within a framework that recognises the resistance mechanisms currently predominant in South Africa's multi-drug and DTR Gram-negative bacteria. Moreover, the withholding of their use for resistant infections that can be treated with currently available antibiotics is a critical part of stewardship, if these antibiotics are to be conserved in the long term.

First report of Klebsiella pneumoniae co-producing OXA-181, CTX-M-55, and MCR-8 isolated from the patient with bacteremia

The worldwide spread of carbapenem-resistant Enterobacteriaceae (CRE) has led to a major challenge to human health. In this case, colistin is often used to treat the infection caused by CRE. However, the coexistence of genes conferring resistance to carbapenem and colistin is of great concern. In this work, we reported the coexistence of blaOXA-181, blaCTX-M-55, and mcr-8 in an ST273 Klebsiella pneumoniae isolate for the first time. The species identification was performed using MALDI-TOF MS, and the presence of various antimicrobial resistance genes (ARGs) and virulence genes were detected by PCR and whole-genome sequencing. Antimicrobial susceptibility testing showed that K. pneumoniae 5589 was resistant to aztreonam, imipenem, meropenem, ceftriaxone, cefotaxime, ceftazidime, levofloxacin, ciprofloxacin, gentamicin, piperacillin-tazobactam, cefepime, and polymyxin B, but sensitive to amikacin. S1-pulsed-field gel electrophoresis (PFGE) and Southern blotting revealed the mcr-8 gene was carried on a ~ 138 kb plasmid with a conserved structure (IS903B-ymoA-inhA-mcr-8-copR-baeS-dgkA-ampC). In addition, blaOXA-181 was found on another ~51 kb plasmid with a composite transposon flanked by insertion sequence IS26. The in vitro conjugation experiments and plasmid sequence probe indicated that the plasmid p5589-OXA-181 and the p5589-mcr-8 were conjugative, which may contribute to the propagation of ARGs. Relevant detection and investigation measures should be taken to control the prevalence of pathogens coharboring blaOXA-181, blaCTX-M-55 and mcr-8.

Phenotypes, genotypes and breakpoints: an assessment of β-lactam/ β-lactamase inhibitor combinations against OXA-48

BACKGROUND

Two out of the three recently approved β-lactam (BL)/β-lactamase inhibitors (BLIs) have higher CLSI susceptibility breakpoints (ceftazidime/avibactam 8 mg/L; meropenem/vaborbactam 4 mg/L) compared with the BL alone (ceftazidime 4 mg/L; meropenem 1 mg/L). This can lead to a therapeutic grey area on susceptibility reports depending on resistance mechanism. For instance, a meropenem-resistant OXA-48 isolate (MIC 4 mg/L) may appear as meropenem/vaborbactam-susceptible (MIC 4 mg/L) despite vaborbactam's lack of OXA-48 inhibitory activity.

METHODS

OXA-48-positive (n = 51) and OXA-48-negative (KPC, n = 5; Klebsiella pneumoniae WT, n = 1) Enterobacterales were utilized. Susceptibility tests (broth microdilution) were conducted with ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam, as well as their respective BL partner. Antimicrobial activity of all six agents was evaluated in the murine neutropenic thigh model using clinically relevant exposures. Efficacy was assessed as the change in bacterial growth at 24 h, compared with 0 h controls.

RESULTS

On average, the three BL/BLI agents resulted in robust bacteria killing among OXA-48-negative isolates. Among OXA-48-positive isolates, poor in vivo activity with imipenem/relebactam was concordant with its resistant phenotypic profile. Variable meropenem/vaborbactam activity was observed among isolates with a 'susceptible' MIC of 4 mg/L. Only 30% (7/23) of isolates at meropenem/vaborbactam MICs of 2 and 4 mg/L met the ≥1 log bacterial reduction threshold predictive of clinical efficacy in serious infections. In contrast, ceftazidime/avibactam resulted in marked bacterial density reduction across the range of MICs and 73% (37/51) of isolates exceeded the ≥1 log bacterial reduction threshold.

CONCLUSIONS

Data demonstrate that current imipenem/relebactam and ceftazidime/avibactam CLSI breakpoints are appropriate. Data also suggest that higher meropenem/vaborbactam breakpoints relative to meropenem can translate to potentially poor clinical outcomes in patients infected with OXA-48-harbouring isolates.

Development of Microfluidic Chip-Based Loop-Mediated Isothermal Amplification (LAMP) Method for Detection of Carbapenemase Producing Bacteria

The rapid and accurate diagnostic methods to identify carbapenemase-producing organisms (CPO) is of great importance for controlling the CPO infection. Herein, we have developed a microfluidic chip-based technique to detect CPO and assessed its clinical value in detecting CPO directly from blood cultures (BCs). The detection performance of the microfluidic chip-based LAMP amplification method was analyzed retrospectively on a collection of 192 isolates including molecularly characterized 108 CPO and 84 non-CPO and prospectively on a collection of 133 positive BCs with or without CPO suspicion, respectively. In the retrospective study, the microfluidic chip-based LAMP amplification method exhibited 87.5% accuracy (95% CI [82.0–91.5]), 97.7% sensitivity (95% CI [91.2–99.6]), 78.8% specificity (95% CI [69.5–86.0]), 79.6% positive predictive value (PPV) (95% CI [70.6–86.5]) and 97.6% negative predictive value (NPV) (95% CI [90.9–99.6]). Among the 192 isolates, 22 (11.5%) false-positives (FP) and 2 (1.0%) false negatives (FN) were observed. In the prospective study, the 133 routine isolates of positive BCs including 18 meropenem-resistant CPO and 115 non-CPO were assessed, and 4 FP were observed in non-CPO and CPO, respectively. The current method showed a total detection performance of 94.0% accuracy (95% CI [88.4–97.1]), 100.0% sensitivity (95% CI [73.2–100.0]), 93.2% specificity (95% CI [86.7–96.8]), 63.6% PPV (95% CI [40.8–82.0]) and 100.0% NPV (95% CI [95.8–100.0]). In summary, the microfluidic chip-based LAMP amplification method is reliable for the rapid screening and detection of CPO with high accuracy, sensitivity, and specificity, and could easily be implemented in clinical microbiology laboratories.

IMPORTANCE Rapid and accurate identification of CPO may reduce the genetic exchanges among bacteria and prevent further dissemination of carbapenemases to non-CPO. The current method had designed microfluidic chip-based LAMP amplification method for multiplex detection of carbapenemase genes and evaluated the detection performance of the newly method. The current method can rapidly screen and detect CPO with high accuracy, sensitivity, and specificity, and could easily be implemented in clinical microbiology laboratories, as this will reduce the carbapenem resistance issues worldwide.

OXA-48-Like β-Lactamases: Global Epidemiology, Treatment Options, and Development Pipeline

Modern medicine is threatened by the rising tide of antimicrobial resistance, especially among Gram-negative bacteria, where resistance to β-lactams is most often mediated by β-lactamases. The penicillin and cephalosporin ascendancies were, in their turn, ended by the proliferation of TEM penicillinases and CTX-M extended-spectrum β-lactamases. These class A β-lactamases have long been considered the most important. For carbapenems, however, the threat is increasingly from the insidious rise of a class D carbapenemase, OXA-48, and its close relatives. Over the past 20 years, OXA-48 and "OXA-48-like" enzymes have proliferated to become the most prevalent enterobacterial carbapenemases across much of Europe, Northern Africa, and the Middle East. OXA-48-like enzymes are notoriously difficult to detect because they often cause only low-level in vitro resistance to carbapenems, meaning that the true burden is likely underestimated. Despite this, they are associated with carbapenem treatment failures. A highly conserved incompatibility complex IncL plasmid scaffold often carries bla_OXA-48 and may carry other antimicrobial resistance genes, leaving limited treatment options. High conjugation efficiency means that this plasmid is sometimes carried by multiple Enterobacterales in a single patient. Producers evade most β-lactam-β-lactamase inhibitor combinations, though promising agents have recently been licensed, notably ceftazidime-avibactam and cefiderocol. The molecular machinery enabling global spread, current treatment options, and the development pipeline of potential new therapies for Enterobacterales that produce OXA-48-like β-lactamases form the focus of this review.

Ceftazidime-avibactam treatment in bacteremia caused by OXA-48 carbapenemase-producing Klebsiella pneumoniae

Therapeutic options for bacteremia caused by carbapenem-resistant Enterobacterales (CRE) OXA-48-type are limited. The objective of this study was to analyze clinical success of CAZ-AVI compared with best available therapy (BAT) in patients with Klebsiella pneumoniae carbapenemase-producing OXA-48-type bacteremia (CRKp-OXA-48). We conducted a retrospective, single-center observational study in adult patients with CRKp-OXA-48 between December 2015 and May 2019. We collected the patients' clinical and epidemiological characteristics, antibiotic treatment (CAZ-AVI vs. BAT), and evolution. Factors associated with clinical success were analyzed using binary logistic regression. The study included 76 patients with CRKp-OXA-48-type bacteremia 33 received CAZ-AVI and 43 BAT. CAZ-AVI was mainly used in monotherapy (91%). Clinical success was more common in patients < 70-year-old (OR 4.79, 95% CI [1.435-16.002], p = 0.011) and CAZ-AVI treatment (OR 6.69, 95% CI [1.68-26.604], p = 0.007). Kaplan-Meier survival curve of 14-day mortality showed a lower mortality in patients who received CAZ-AVI (log rank 0.013). However, CAZ-AVI did not achieve statistical difference in IPTW for 14- and 30-day mortality (aOR 0.1, 95% CI [0.02-1.22], p = 0.076 and aOR 1.7, 95% CI [0.48-5.98], p = 0.413, respectively). CAZ-AVI treatment might be associated with a greater clinical success in CRKp-OXA-48 bacteremia.

Comparison of carbapenem minimum inhibitory concentrations of OXA-48-like Klebsiella pneumoniae by Sensititre, Vitek 2, MicroScan and Etest

OBJECTIVES

The aim of this laboratory-based study was to compare carbapenem minimum inhibitory concentrations (MICs) yielded by Sensititre, Vitek 2, MicroScan WalkAway plus and Etest for OXA-48-like Klebsiella pneumoniae isolates.

METHODS

Analysis was performed for categorical agreement for ertapenem, meropenem and imipenem, and the proportion of isolates with MICs ≤8μg/mL and the MIC50/MIC90 for meropenem and imipenem, from a convenience sample of 82 deduplicated blood culture OXA-48-like K. pneumoniae isolates.

RESULTS

The proportion of isolates testing susceptible to ertapenem by Etest (19/82, 23.1%) differed from Sensititre/Vitek (0/82) and MicroScan (2/82, 2.4%) (p<0.001 for all). For meropenem the proportion of isolates susceptible by Etest (31/82, 37.8%) differed from Sensititre/Vitek (16/82, 19.5%) (p=0.015). There was variation in the proportion of isolates that tested imipenem susceptible when comparing Sensititre (9/82, 11%) and Vitek (8/82, 9.8%) to MicroScan (27/82, 32.9%), p=0.001 and p<0.001, respectively, Sensititre and Vitek to Etest (45/82, 54.9%), p<0.001 for both, and MicroScan to Etest, p=0.007. The proportion of isolates with meropenem MICs ≤8μg/mL with Sensititre and Vitek differed significantly from Etest, 58.5% and 85.4%, respectively, p<0.001. A 2-fold difference between the Sensititre and Vitek meropenem and imipenem MIC at which ≥50% of isolates were inhibited compared to the MicroScan, and a 4-fold difference compared to Etest, was present.

CONCLUSIONS

Substantial variability in carbapenem MICs for OXA-48-like CPE isolates by the four methods was demonstrated. Performance characteristics verification of MIC methods in use for the predominant CPE type is required by laboratories to optimise accuracy of carbapenem reporting.

Ceftolozane/tazobactam for hospital-acquired/ventilator-associated bacterial pneumonia due to ESBL-producing Enterobacterales: a subgroup analysis of the ASPECT-NP clinical trial

BACKGROUND

After the MERINO trial with piperacillin/tazobactam, the efficacy of β-lactam/tazobactam combinations in serious infections involving extended-spectrum β-lactamase (ESBL)-producing pathogens merits special evaluation.

OBJECTIVES

To further confirm the efficacy of ceftolozane/tazobactam in treating hospital-acquired/ventilator-associated bacterial pneumonia (HABP/VABP) involving ESBL-positive and/or AmpC-producing Enterobacterales.

METHODS

Retrospective subgroup analysis of the ASPECT-NP trial comparing ceftolozane/tazobactam with meropenem for treating HABP/VABP in mechanically ventilated adults (ClinicalTrials.gov NCT02070757). ESBLs were identified using whole genome sequencing. Chromosomal AmpC production was quantified employing a high-sensitivity mRNA transcription assay.

RESULTS

Overall, 61/726 (8.4%) participants had all baseline lower respiratory tract (LRT) isolates susceptible to both study treatments and ≥1 baseline ESBL-positive/AmpC-overproducing Enterobacterales isolate. In this subgroup (ceftolozane/tazobactam n = 30, meropenem n = 31), baseline characteristics were generally comparable between treatment arms. The most frequent ESBL-positive and/or AmpC-overproducing Enterobacterales isolates (ceftolozane/tazobactam n = 31, meropenem n = 35) overall were Klebsiella pneumoniae (50.0%), Escherichia coli (22.7%), and Proteus mirabilis (7.6%). The most prevalent ESBLs were CTX-M-15 (75.8%), other CTX-M (19.7%), and SHV (4.5%); 10.6% of isolates overproduced chromosomal AmpC. Overall, 28 day all-cause mortality was 6.7% (2/30) with ceftolozane/tazobactam and 32.3% (10/31) with meropenem (25.6% difference, 95% CI: 5.54 to 43.84). Clinical cure rate at test-of-cure, 7-14 days after end of therapy, was 73.3% (22/30) with ceftolozane/tazobactam and 61.3% (19/31) with meropenem (12.0% difference, 95% CI: -11.21 to +33.51). Per-isolate microbiological response at test-of-cure was 64.5% (20/31) with ceftolozane/tazobactam and 74.3% (26/35) with meropenem (-9.8% difference, 95% CI: -30.80 to +12.00).

CONCLUSIONS

These data confirm ceftolozane/tazobactam as an effective treatment option for HABP/VABP involving ceftolozane/tazobactam-susceptible ESBL-positive and/or AmpC-producing Enterobacterales.

Using Targeted Liquid Chromatography-Tandem Mass Spectrometry to Rapidly Detect β-Lactam, Aminoglycoside, and Fluoroquinolone Resistance Mechanisms in Blood Cultures Growing E. coli or K. pneumoniae

New and rapid antimicrobial susceptibility/resistance testing methods are required for bacteria from positive blood cultures. In this study, a multiplex-targeted liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay was developed and validated for the detection of β-lactam, aminoglycoside, and fluoroquinolone resistance mechanisms in blood cultures growing Escherichia coli or Klebsiella pneumoniae complex. Selected targets were the β-lactamases SHV, TEM, OXA-1-like, CTX-M-1-like, CMY-2-like, chromosomal E. coli AmpC (cAmpC), OXA-48-like, NDM, VIM, and KPC; the aminoglycoside-modifying enzymes AAC(3)-Ia, AAC(3)-II, AAC(3)-IV, AAC(3)-VI, AAC(6′)-Ib, ANT(2′′)-I, and APH(3′)-VI; the 16S-RMTases ArmA, RmtB, RmtC, and RmtF; the quinolone resistance mechanisms QnrA, QnrB, AAC(6′)-Ib-cr; the wildtype quinolone resistance determining region of GyrA; and the E. coli porins OmpC and OmpF. The developed assay was evaluated using 100 prospectively collected positive blood cultures, and 148 negative blood culture samples spiked with isolates previously collected from blood cultures or isolates carrying less prevalent resistance mechanisms. The time to result was approximately 3 h. LC-MS/MS results were compared with whole-genome sequencing and antimicrobial susceptibility testing results. Overall, there was a high agreement between LC-MS/MS results and whole-genome sequencing results. In addition, the majority of susceptible and non-susceptible phenotypes were correctly predicted based on LC-MS/MS results. Exceptions were the predictions for ciprofloxacin and amoxicillin/clavulanic acid that matched with the phenotype in 85.9 and 63.7% of the isolates, respectively. Targeted LC-MS/MS based on parallel reaction monitoring can be applied for the rapid and accurate detection of various resistance mechanisms in blood cultures growing E. coli or K. pneumoniae complex.

Efficacy and In Vitro Activity of Novel Antibiotics for Infections With Carbapenem-Resistant Gram-Negative Pathogens

Infections by Gram-negative multi-drug resistant (MDR) bacterial species are difficult to treat using available antibiotics. Overuse of carbapenems has contributed to widespread resistance to these antibiotics; as a result, carbapenem-resistant Enterobacterales (CRE), A. baumannii (CRAB), and P. aeruginosa (CRPA) have become common causes of healthcare-associated infections. Carbapenems, tigecycline, and colistin are the last resource antibiotics currently used; however, multiple reports of resistance to these antimicrobial agents have been documented worldwide. Recently, new antibiotics have been evaluated against Gram-negatives, including plazomicin (a new aminoglycoside) to treat CRE infection, eravacycline (a novel tetracycline) with in vitro activity against CRAB, and cefiderocol (a synthetic conjugate) for the treatment of nosocomial pneumonia by carbapenem-non-susceptible Gram-negative isolates. Furthermore, combinations of known β-lactams with recently developed β-lactam inhibitors, such as ceftazidime-avibactam, ceftolozane-tazobactam, ceftazidime-tazobactam, and meropenem-vaborbactam, has been suggested for the treatment of infections by extended-spectrum β-lactamases, carbapenemases, and AmpC producer bacteria. Nonetheless, they are not active against all carbapenemases, and there are reports of resistance to these combinations in clinical isolates.This review summarizes and discusses the in vitro and clinical evidence of the recently approved antibiotics, β-lactam inhibitors, and those in advanced phases of development for treating MDR infections caused by Gram-negative multi-drug resistant (MDR) bacterial species.

Inoculum effect of Enterobacterales co-expressing OXA-48 and CTX-M on the susceptibility to ceftazidime/avibactam and meropenem

BACKGROUND

The treatment of infections caused by OXA-48/CTX-M-coproducing Enterobacterales may be based on new beta-lactam/beta-lactamase inhibitors, such as ceftazidime/avibactam (CZA), or on high dose of meropenem (MER). However, bacterial density at the infection site may vary widely, and the inoculum effect of such antimicrobial strategies has never been specifically investigated. To determine if CZA or MER susceptibilities are impacted by high inocula of Enterobacterales co-expressing both enzymes: OXA-48 like and CTX-M.

METHODS

Determination of an inoculum effect was performed with a standard inoculum of 10⁸ CFU/mL (0.5 McFarland) as recommended by EUCAST guidelines and compared to a twofold increase as well as a tenfold increase (1 McFarland and 5 McFarland respectively).

RESULTS

Thirty-nine isolates of ceftazidime-resistant Enterobacterales were included of which 27 (70%) co-expressed OXA-48 + CTX-M-15, 6 (15%) OXA-48 + CTX-M-14, and 6 (15%) OXA-181 + CTX-M-15. The susceptibility to the CZA combination was preserved whatever the inoculum used. Regarding MER, 24 (61.5%) of the isolates were susceptible to MER with the standard inoculum, 19 (48.7%) with a twofold increase, and only 15 (38.5%) with a tenfold increase.

CONCLUSION

We showed that in vitro inoculum effect was observed with meropenem but not with CZA for OXA-48- combined with CTX-M-producing Enterobacterales.

Antimicrobial Activity of Ceftazidime-Avibactam and Comparators against Pathogens Harboring OXA-48 and AmpC Alone or in Combination with Other β-Lactamases Collected from Phase 3 Clinical Trials and an International Surveillance Program

In vitro activities of ceftazidime-avibactam (CAZ-AVI) and key comparators against AmpC-overproducing Enterobacterales and Pseudomonas aeruginosa isolates from four Phase 3 clinical trials and against OXA-48-producing Enterobacterales with multiple resistance mechanisms from the Antimicrobial Testing Leadership and Surveillance (ATLAS) program were evaluated. Susceptibility to CAZ-AVI and comparators was determined by reference broth microdilution methods. Clinical response at test of cure (TOC) was assessed in patients from Phase 3 trials with baseline OXA-48-producing Enterobacterales or AmpC-overproducing Enterobacterales and P. aeruginosa treated with CAZ-AVI or comparators. Against 77 AmpC-overproducing Enterobacterales isolates from Phase 3 trials, meropenem-vaborbactam (98.7% susceptible [S]), CAZ-AVI (96.1% S), and meropenem (96.1% S) had similar in vitro activity and were more active than ceftolozane-tazobactam (24.7% S). Clinical cure rates in patients with baseline AmpC-overproducing Enterobacterales were 80.7% (n = 21/26) and 85.0% (n = 17/20) for CAZ-AVI and comparators. Against 53 AmpC-overproducing P. aeruginosa isolates from Phase 3 trials, CAZ-AVI (73.6% S) was more active in vitro than ceftolozane-tazobactam (58.5% S) and meropenem (37.7% S). Clinical cure rates in patients with baseline AmpC-overproducing P. aeruginosa were 85.7% (n = 12/14) and 75.0% (n = 9/12) for CAZ-AVI and comparators, respectively. Of 113 OXA-48-producing isolates from the ATLAS program, 99.1% were susceptible to CAZ-AVI. Four patients with baseline OXA-48-producing Klebsiella pneumoniae isolates treated with CAZ-AVI in Phase 3 trials were clinical cures at TOC and had favorable microbiological response. CAZ-AVI was among the most active agents against AmpC-overproducing P. aeruginosa and Enterobacterales and had greater in vitro activity against OXA-48-producing Enterobacterales than meropenem-vaborbactam, meropenem, ceftolozane-tazobactam, and other comparators.

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

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

A retrospective observational cohort study of the clinical epidemiology of bloodstream infections due to carbapenem-resistant Klebsiella pneumoniae in an OXA-48 endemic setting

We aimed to characterize the epidemiology and clinical outcomes of patients with bloodstream infections (BSIs) due to carbapenem-resistant Klebsiella pneumoniae (CRKP) in an OXA-48 predominant environment. This was a retrospective single-center cohort study including all consecutive patients with CRKP BSIs treated between 01.01.2014 and 31.12.2018. Multivariate analysis, subgroup analysis and propensity score-matched analysis were employed to analyze 30-day mortality as the primary outcome. Clinical cure at day 14 was also analyzed in the whole cohort. 124 patients with unique isolates met all the inclusion criteria. OXA-48 was the most common type of carbapenemase (85.5%). Inappropriate therapy was significantly associated with 30-day mortality (70.6% vs. 39.7%; adjusted odds ratio [aOR], 4.65; 95% Confidence Interval [CI], 1.50-14.40; p = 0.008) and 14-day clinical failure (78.5% vs. 56.2%; aOR, 3.14; 95% CI, 1.09-9.02; p = 0.033) in multivariate analyses. Among those treated appropriately, the 30-day mortality rates were similar in monotherapy and combination therapy arms (OR, 2.85; 95% CI, 0.68-11.95; p = 0.15). INCREMENT CPE mortality score (aOR, 1.16; 95% CI, 1.01-1.33; p = 0.029), sepsis at the onset of BSI (aOR, 2.90; 95% CI, 1.02-8.27; p = 0.046), and inappropriate therapy (aOR, 4.65; 95% CI, 1.50-14.40; p = 0.008) were identified as independent risk factors for 30-day mortality. Colistin resistance in CRKP had no significant impact on 30-day mortality. These results were also confirmed in all propensity score-matched analyses and sensitivity analyses. Appropriate regimens were associated with better clinical outcomes than were inappropriate therapies in BSIs with CRKP possessing OXA-48, dominantly.

OUP accepted manuscript

Objectives

Ertapenem has proven to be an effective antimicrobial; however, increasing enzyme-mediated resistance has been noted. Combination with zidebactam, a β-lactam enhancer, is restorative. Human-simulated regimens (HSRs) of ertapenem and zidebactam alone and in combination (WCK 6777; 2 g/2 g q24h) were assessed for efficacy against carbapenemase-producing Klebsiella pneumoniae (CP-KP) in the pneumonia model.

Methods

Infected ICR mice were rendered neutropenic and exposed to various doses of ertapenem and zidebactam alone and in combination to develop the HSRs that were subsequently confirmed in additional pharmacokinetic studies. Twenty-one CP-KP (KPC or OXA-48-like producers) with WCK 6777 MICs of 1–8 mg/L were utilized. Mice were treated for 24 h with saline or HSRs of ertapenem, zidebactam and WCK 6777. Efficacy was defined as change in mean lung bacterial density relative to 0 h.

Results

Confirmatory pharmacokinetic analysis showed agreement between predicted human exposures (%fT_>MIC) and those achieved in vivo for all three HSRs. The 0 h bacterial density across all isolates was 6.69 ± 0.31 log₁₀ cfu/lungs. At 24 h, densities increased by 2.57 ± 0.50, 2.2 ± 0.60 and 2.05 ± 0.71 log₁₀ cfu/lungs in the 24 h control, ertapenem HSR and zidebactam HSR groups, respectively. Overall, 18/21 of the isolates exposed to the WCK 6777 HSR displayed a killing profile that exceeded the translational benchmark for efficacy of a 1 log₁₀ cfu reduction. Among the remaining three isolates, two displayed ∼0.5 log₁₀ kill and stasis was observed in the third.

Conclusions

Human-simulated exposures of WCK 6777 demonstrated potent in vivo activity against CP-KP, including those with WCK 6777 MICs up to 8 mg/L.

Multicenter surveillance of in vitro activities of cefepime-zidebactam, cefepime-enmetazobactam, omadacycline, eravacycline, and comparator antibiotics against Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex causing bloodstream infection in Taiwan, 2020

OBJECTIVES

: To determine the in vitro activities of novel and comparator antibiotics against gram-negative bacteria (GNB) in Taiwan.

METHODS

: Isolates of Escherichia coli (n = 335), Klebsiella pneumoniae (n = 316; 144 isolates with hyperviscosity characteristics), Pseudomonas aeruginosa (n = 271), Acinetobacter baumannii complex species (n = 187), and non-typhoidal Salmonella species (n = 226), Shigella species (n = 13) from miscellaneous culture sources were collected in 2020 in Taiwan. The MICs of the isolates to test antibiotics were determined using the broth microdilution method. GeneXpert was used to detect genes encoding carbapenemases among the carbapenem-non-susceptible (NS) Enterobacterales isolates.

RESULTS

: The MIC values of the cefepime-enmetazobactam combination against extended-spectrum β-lactamase-producing E. coli and K. pneumoniae isolates (MIC₉₀ ≤ 0.5 mg/L), bla_KPC-harboring E. coli isolates (0.25 mg/L; n = 2), and 80% of bla_OXA-48-like gene-harboring K. pneumoniae isolates (≤2 mg/L) were low. The MIC ranges of the cefepime-zidebactam against carbapenemase-producing Enterobacterales isolates (irrespective of the carbapenemase type [MIC₉₀ ≤ 4 mg/L]) and carbapenem-NS or ceftolozane-tazobactam-NS P. aeruginosa isolates (MIC₉₀ value, 8 mg/L) were significantly lower than those of the cefepime-enmetazobactam.

CONCLUSIONS

: The efficacy of novel antibiotics against important drug-resistant GNB must be monitored and validated during the clinical treatment of patients.

In Vitro Synergism of Azithromycin Combination with Antibiotics against OXA-48-Producing Klebsiella pneumoniae Clinical Isolates

Carbapenem-resistant Klebsiella pneumoniae has globally emerged as an urgent threat leading to the limitation for treatment. K. pneumoniae carrying blaOXA-48, which plays a broad magnitude of carbapenem susceptibility, is widely concerned. This study aimed to characterize related carbapenem resistance mechanisms and forage for new antibiotic combinations to combat blaOXA-48-carrying K. pneumoniae. Among nine isolates, there were two major clones and a singleton identified by ERIC-PCR. Most isolates were resistant to ertapenem (MIC range: 2->256 mg/L), but two isolates were susceptible to imipenem and meropenem (MIC range: 0.5-1 mg/L). All blaOXA-48-carrying plasmids conferred carbapenem resistance in Escherichia coli transformants. Two ertapenem-susceptible isolates carried both outer membrane proteins (OMPs), OmpK35 and OmpK36. Lack of at least an OMP was present in imipenem-resistant isolates. We evaluated the in vitro activity of an overlooked antibiotic, azithromycin, in combination with other antibiotics. Remarkably, azithromycin exhibited synergism with colistin and fosfomycin by 88.89% and 77.78%, respectively. Bacterial regrowth occurred after exposure to colistin or azithromycin alone. Interestingly, most isolates were killed, reaching synergism by this combination. In conclusion, the combination of azithromycin and colistin may be an alternative strategy in dealing with blaOXA-48-carrying K. pneumoniae infection during a recent shortage of newly effective antibiotic development.

Increasing frequency of OXA-48-producing Enterobacterales worldwide and activity of ceftazidime/avibactam, meropenem/vaborbactam and comparators against these isolates

OBJECTIVES

To investigate the increase in the rates of OXA-48-like-producing isolates during 3 years of global surveillance.

METHODS

Among 55?>162 Enterobacterales isolates, 354 carbapenem-resistant isolates carried genes encoding OXA-48-like enzymes. Isolates were susceptibility tested for ceftazidime/avibactam and comparators by broth microdilution methods. Analysis of β-lactam resistance mechanisms and MLST was performed in silico using WGS data.

RESULTS

OXA-48-like-producing isolates increased from 0.5% (94/18 656) in 2016 to 0.9% (169/18?>808) in 2018. OXA-48 was the most common variant; isolates primarily were Klebsiella pneumoniae (318/354 isolates) from Europe and adjacent countries. MLST analysis revealed a diversity of STs, but K. pneumoniae belonging to ST395, ST23 and ST11 were observed most frequently. Thirty-nine isolates harboured MBLs and were resistant to most agents tested. The presence of blaCTX-M-15 (258 isolates), OmpK35 nonsense mutations (232) and OmpK36 alterations (316) was common among OXA-48 producers. Ceftazidime, cefepime and aztreonam susceptibility rates, when applying CLSI breakpoints, were 12%-15% lower for isolates carrying ESBLs alone and with either or both OmpK35 stop codons and OmpK36 alterations. Meropenem and, remarkably, meropenem/vaborbactam were affected by specific OmpK36 alterations when a deleterious mutation also was observed in OmpK35. These mechanisms caused a decrease of 12%-42% in the susceptibility rates for meropenem and meropenem/vaborbactam. Ceftazidime/avibactam susceptibility rates were >98.9%, regardless of the presence of additional β-lactam resistance mechanisms.

CONCLUSIONS

Guidelines for the treatment of infections caused by OXA-48-producing isolates are scarce and, as the dissemination of these isolates continues, studies are needed to help physicians understand treatment options for these infections.

Emergence of 16S rRNA methyltransferases among carbapenemase-producing Enterobacterales in Spain studied by whole-genome sequencing

The emergence of 16S rRNA methyltransferases (RMTs) in Gram-negative pathogens bearing other clinically relevant resistance mechanisms, such as carbapenemase-producing Enterobacterales (CPE), is becoming an alarming concern. We investigated the prevalence, antimicrobial susceptibility, resistance mechanisms, molecular epidemiology and genetic support of RMTs in CPE isolates from Spain. This study included a collection of 468 CPE isolates recovered during 2018 from 32 participating Spanish hospitals. MICs were determined using the broth microdilution method, the agar dilution method (fosfomycin) or MIC gradient strips (plazomicin). All isolates were subjected to hybrid whole-genome sequencing (WGS). Sequence types (STs), core genome phylogenetic relatedness, horizontally acquired resistance mechanisms, plasmid analysis and the genetic environment of RMTs were determined in silico from WGS data in all RMT-positive isolates. Among the 468 CPE isolates evaluated, 24 isolates (5.1%) recovered from nine different hospitals spanning five Spanish regions showed resistance to all aminoglycosides and were positive for an RMT (21 RmtF, 2 ArmA and 1 RmtC). All RMT-producers showed high-level resistance to all aminoglycosides, including plazomicin, and in most cases exhibited an extensively drug-resistant susceptibility profile. The RMT-positive isolates showed low genetic diversity and were global clones of Klebsiella pneumoniae (ST147, ST101, ST395) and Enterobacter cloacae (ST93) bearing bla_OXA-48, bla_NDM-1 or bla_VIM-1 carbapenemase genes. RMTs were harboured in five different multidrug resistance plasmids and linked to efficient mobile genetic elements. Our findings highlight that RMTs are emerging among clinical CPE isolates from Spain and their spread should be monitored to preserve the future clinical utility of aminoglycosides and plazomicin.

An evidence-based multidisciplinary approach focused at creating algorithms for targeted therapy of infection-related ventilator associated complications (IVACs) caused by Enterobacterales in critically ill adult patients

INTRODUCTION

Prompt implementation of appropriate targeted antibiotic therapy representsa valuable approach in improving clinical and ecological outcome in critically septic patients. Thismultidisciplinary opinion article aims to develop evidence-based algorithms for targeted antibiotictherapy of infection-related ventilator associated complications (IVACs) caused by Enterobacterales,which are among the most common pathogens associated with these conditions.

AREAS COVERED

A multidisciplinary team of four experts had several rounds of assessment for developingalgorithms devoted to targeted antimicrobial therapy of IVACs caused by Enterobacterales.A literature search was performed on PubMed-MEDLINE (until March 2021) to provide evidence forsupporting therapeutic choices. Quality and strength of evidence was established according toa hierarchical scale of the study design. Six different algorithms with associated recommendations concerning therapeutic choice and dosing optimization were suggested according to the susceptibilitypattern of Enterobacterales: multi-susceptible, extended-spectrum beta-lactamase (ESBL)-producing,AmpC beta-lactamase-producing, Klebsiella pneumoniae carbapenemase (KPC)-producing, OXA-48-producing, and metallo-beta-lactamase (MBL)-producing Enterobacterales.

EXPERT OPINION

The implementation of algorithms focused on prompt revision of antibiotic regimensguided by results of conventional and rapid diagnostic methodologies, appropriate place in therapy ofnovel beta-lactams, implementation of strategies for sparing the broadest-spectrum antibiotics, and PK/PD optimization of antibiotic dosing regimens is strongly suggested.

Characterization of Antimicrobial Resistance Patterns of Klebsiella pneumoniae Isolates Obtained from Wound Infections

CDATA[Background: Multidrug resistance among ESBL producing isolates has limited the administration of proper antibiotics. It is, therefore, important to monitor the resistance patterns of Klebsiella pneumoniae isolates and provide infection control strategies to prevent nosocomial outbreaks. This study was aimed to determine antimicrobial resistance patterns of K. pneumoniae isolates obtained from wound infections of patients in Tehran, Iran.

METHODS

A total of 102 K. pneumoniae isolates were obtained from wound infections of patients in Tehran, Iran. The production of phenotypic ESBL and carbapenemase was assessed using the double-disc synergy test (DDST) and modified Hodge test (MHT), respectively. PCR was performed for the detection of ESBL, carbapenemase, quinolone and aminoglycoside resistance genes.

RESULTS

Forty-six (45.1%) and 23 (22.5%) isolates, out of the 102 isolates, were phenotypically detected as ESBL and carbapenemase producers, respectively. The PCR results showed that 80/102 (78.4%) and 51/102 (50%) isolates possessed at least one of the assessed ESBL and carbapenemase genes, respectively. Quinolone resistance determinants (QRDs) and aac(6')-Ib genes were found amongst 50 (49%) and 67 (65.7%) isolates, respectively. Four isolates carried bla_TEM, bla_SHV, bla_CTX-M, qnrB, qnrS and aac(6')-Ib genes, simultaneously.

CONCLUSION

Due to the presence of multiple resistance genes among some K. pneumoniae strains, antibiotic agents should be used with caution to preserve their efficacy in case of life-threatening infections.

Extended Spectrum Beta-Lactamase (ESBL) Produced by Gram-Negative Bacteria in Trinidad and Tobago

Gram-negative bacterial infections are a global health problem. The production of beta-lactamase is still the most vital factor leading to beta-lactam resistance. In Trinidad and Tobago, extended spectrum beta-lactamase (ESBL) production has been detected and reported mainly in the isolates of Klebsiella pneumoniae and Escherichia coli and constitutes a public health emergency that causes high morbidity and mortality in some patients. In this literature review, the authors cover vast information on ESBL frequency and laboratory detection using both conventional and molecular methods from clinical data. The aim is to make the reader reflect on how the actual knowledge can be used for rapid detection and understanding of the spread of antimicrobial resistance problems stemming from ESBL production among common Gram-negative organisms in the health care system.

Evaluation of the Performances of the Rapid Test RESIST-5 O.O.K.N.V Used for the Detection of Carbapenemases-Producing Enterobacterales

Background: The emergence of carbapenemase-producing Enterobacterales (CPE) is a public health problem, requiring rapid and reliable diagnostic methods. The aim is to compare the new rapid immunochromatographic (IC) test: RESIST-5 O.O.K.N.V with PCR and the predictive model of EUCAST algorithm for the detection of CPE. Methods: A longitudinal cross-sectional study was carried out in the bacteriology-virology laboratory of the Ibn Rochd-Casablanca University Hospital, from 1 February 2019 to 28 February 2020, concerning strains with reduced sensitivity to Ertapenem. The identification of bacterial species was carried out according to the standard criteria of microbiology and antibiogram according to CASFM-EUCAST 2019 recommendations. The sensitivity and specificity of the rapid IC test were calculated. Results: The results of the new IC test showed a sensitivity and specificity of 100% for the detection of OXA-48 and NDM. These carbapenemases were detected simultaneously with a sensitivity and specificity of 100%. OXA-48 was the most common carbapenemas found (36%), followed by NDM (24%) and (13.4%) cases of OXA-48 and NDM coexistence. Conclusion: The rapid IC test could be a rapid and effective diagnostic tool for detecting the most common carbapenemases in our context, and to accelerate the implementation of adequate antibiotic therapy and infection control measures in patients with CPE infections

Rapid personalized AMR diagnostics using two-dimensional antibiotic resistance profiling strategy employing a thermometric NDM-1 biosensor

Antimicrobial resistance (AMR) threatens global public health and modern surgical medicine. Expression of β-lactamase genes is the major mechanism by which pathogens become antibiotic resistant. Pathogens expressing extended spectrum β-lactamases (ESBL) and carbapenemases (CP) are especially difficult to treat and are associated with increased hospitalization and mortality rates. Despite considerable effort, identification of ESBLs and CPs in a clinically relevant timeframe remains challenging. In this study, a two-dimensional AMR profiling assay strategy was developed employing panels of antibiotics (penicillins, cephamycins, oximino-cephalosporins and carbapenems) and β-lactamases inhibitors (avibactam and EDTA). The assay required the development of a novel biosensor that employed New Delhi metallo-β-lactamase-1 (NDM-1) as the sensing element. Functionally probing β-lactamase activity using substrates and inhibitors combinatorically increased the informational content that enabled the development of assays capable of simultaneous, differential identification of multiple β-lactamases expressed in a single bacterial isolate. More specifically, the assay enabled the simultaneous identification of ESBL and CP in mock samples, as well as in an engineered construct which co-expressed these β-lactamases. The NDM-1 biosensor assay was 16 times and 8 times more sensitive than the ESBL Nordmann/Dortet/Poirel (NDP) and Carba Nordmann/Poirel (NP) assays, respectively. In a retrospective study, NDM-1 biosensor assays were able to differentially identify ESBLs, metallo-CPs and serine-CPs β-lactamases in 23 clinical isolates with 100% accuracy. An assay algorithm was developed which accelerated data analytics reducing turnaround to <1 h. The assay strategy integrated with AI-based data analytics has the potential to provide physicians with a comprehensive readout of patient AMR status.

In vivo activity of WCK 4282 (high-dose cefepime/tazobactam) against serine β-lactamase-producing Enterobacterales and Pseudomonas aeruginosa in the neutropenic murine thigh infection model

OBJECTIVES

WCK 4282, high-dose cefepime/tazobactam, possesses potent in vitro activity against Gram-negative organisms including ESBL- and cephalosporinase-harbouring strains. The purpose of this evaluation was to investigate the in vivo activity of human-simulated exposures of WCK 4282 against serine-β-lactamase-harbouring Enterobacterales and Pseudomonas aeruginosa.

METHODS

Nineteen clinical isolates were evaluated (ESBL/cephalosporinase producers, n = 8 Escherichia coli, n = 4 P. aeruginosa; KPC producers, n = 3 Klebsiella pneumoniae, n = 1 Klebsiella aerogenes; OXA-48/181 producers, n = 2 K. pneumoniae, n = 1 E. coli). WCK 4282 MICs ranged from 4 to 32 mg/L compared with 16 to >128 mg/L for cefepime. Thigh-infected neutropenic mice received cefepime, WCK 4282 or sham control over 24 h prior to harvest. Cefepime and tazobactam dosing regimens produced plasma profiles of fAUC, fT>MIC and fCmax similar to human exposure after WCK 4282 2/2 g every 8 h (1.5 h infusion).

RESULTS

Bacterial burdens (log10 cfu/thigh) were 5.81 ± 0.36 at 0 h and 9.29 ± 0.88 at 24 h in untreated controls. WCK 4282 produced potent activity against ESBL/cephalosporinase-producing strains with WCK 4282 MIC ≤16 mg/L; mean changes in log10 cfu/thigh from 0 h were -1.70 ± 0.77 and +1.86 ± 2.03 log10 cfu/thigh for WCK 4282 and cefepime human-simulated regimens, respectively. WCK 4282 produced variable activity against serine-carbapenemase-harbouring isolates. For the KPC-harbouring strains, WCK 4282 produced bacteriostasis with a mean -0.1 ± 0.61 log10 cfu/thigh. Against OXA-48/181-harbouring isolates, WCK 4282 produced a range of change in bacterial burden of -1.23 ± 0.33 to +1.04 ± 0.7 log10 cfu/thigh.

CONCLUSIONS

Human-simulated exposures of WCK 4282 produced in vivo efficacy against ESBL/cephalosporinase-producing, piperacillin/tazobactam- and ceftolozane/tazobactam-non-susceptible Enterobacterales and P. aeruginosa. These findings support further development of this combination as a carbapenem-sparing agent.

An Evidence-Based Multidisciplinary Approach Focused at Creating Algorithms for Targeted Therapy of BSIs, cUTIs, and cIAIs Caused by Enterobacterales in Critically Ill Adult Patients

Prompt implementation of appropriate targeted antibiotic therapy represents a valuable approach in improving clinical and ecological outcome in critically septic patients. This multidisciplinary opinion article focused at developing evidence-based algorithms for targeted antibiotic therapy of bloodstream (BSIs), complicated urinary tract (cUTIs), and complicated intrabdominal infections (cIAIs) caused by Enterobacterales. The aim was to provide a guidance for intensive care physicians either in appropriately placing novel antibiotics or in considering strategies for sparing the broadest-spectrum antibiotics. A multidisciplinary team of experts (one intensive care physician, one infectious disease consultant, one clinical microbiologist and one MD clinical pharmacologist), performed several rounds of assessment to reach agreement in developing six different algorithms according to the susceptibility pattern (one each for multi-susceptible, extended-spectrum beta-lactamase-producing, AmpC beta-lactamase-producing, Klebsiella pneumoniae carbapenemase (KPC)-producing, OXA-48-producing, and Metallo-beta-lactamase (MBL)-producing Enterobacterales). Whenever multiple therapeutic options were feasible, a hierarchical scale was established. Recommendations on antibiotic dosing optimization were also provided. In order to retrieve evidence-based support for the therapeutic choices proposed in the algorithms, a comprehensive literature search was performed by a researcher on PubMed-MEDLINE from inception until March 2021. Quality and strength of evidence was established according to a hierarchical scale of the study design. Only articles published in English were included. It is expected that these algorithms, by allowing prompt revision of antibiotic regimens whenever feasible, appropriate place in therapy of novel beta-lactams, implementation of strategies for sparing the broadest-spectrum antibiotics, and pharmacokinetic/pharmacodynamic optimization of antibiotic dosing regimens, may be helpful either in improving clinical outcome or in containing the spread of antimicrobial resistance.