AmpC Production Research Articles

Building an International One Health Strain Level Database to Characterise the Epidemiology of AMR Threats: ESBL—AmpC Producing E. coli as An Example—Challenges and Perspectives

Antimicrobial resistance (AMR) is one of the top public health threats nowadays. Among the most important AMR pathogens, Escherichia coli resistant to extended spectrum cephalosporins (ESC-EC) is a perfect example of the One Health problem due to its global distribution in animal, human, and environmental sources and its resistant phenotype, derived from the carriage of plasmid-borne extended-spectrum and AmpC β-lactamases, which limits the choice of effective antimicrobial therapies. The epidemiology of ESC-EC infection is complex as a result of the multiple possible sources involved in its transmission, and its study would require databases ideally comprising information from animal (livestock, companion, wildlife), human, and environmental sources. Here, we present the steps taken to assemble a database with phenotypic and genetic information on 10,763 ESC-EC isolates retrieved from multiple sources provided by 13 partners located in eight European countries, in the frame of the DiSCoVeR Joint Research project funded by the One Health European Joint Programme (OH-EJP), along with its strengths and limitations. This database represents a first step to help in the assessment of different geographical and temporal trends and transmission dynamics in animals and humans. The work performed highlights aspects that should be considered in future international efforts, such as the one presented here.

Characterization of Carbapenem-Resistant Escherichia Coli and Klebsiella : A Role For Ampc-Producing Isolates

Aim: This study aimed to investigate the role of AmpC enzymes in carbapenem resistance among AmpC/extended-spectrum β-lactamase (ESBL)-producing clinical isolates of Escherichia coli and Klebsiella spp. Methods: Fifty-six bacterial strains that were AmpC producers were examined. The antibiotic susceptibility test was performed by the disk diffusion and E-test. The prevalence of the plasmid carbapenemase was determined using PCR. Results: The resistance to meropenem in the AmpC+/ESBL+ group was 64%, higher than that reported for the AmpC-/ESBL+ group. Ten isolates of the carbapenem-resistant AmpC producers were negative for carbapenemase-encoding genes. Conclusion: Carbapenem resistance among AmpC-producing isolates with negative results for carbapenemase-encoding genes potentially demonstrates the role of AmpC enzymes among these isolates.

Plasmid-Mediated Colistin Resistance Genes mcr-1 and mcr-4 in Multidrug-Resistant Escherichia coli Strains Isolated from a Healthy Pig in Portugal.

Antimicrobial resistance encoded by mobile colistin resistance (mcr) genes is a global and emergent threat. In this study, we report the occurrence of two different populations of colistin-resistant Escherichia coli harboring mcr-1 and mcr-4 variants in the intestinal microbiome of a healthy pig. Following antimicrobial susceptibility determination, the presence of mcr genes in two E. coli strains, isolated according to different selective microbiological procedures, was screened by PCR. Whole-genome sequencing confirmed that both strains were multidrug-resistant; INIAV_002EC was an AmpC producer carrying blaCMY-2, blaTEM-1B, qnrS1, mcr-1.1 genes, and INIAV_001EC carrying blaTEM-1A, tetB, and mcr-4.1 genes, along with mutations in quinolone resistance-determining regions. In addition, both strains harbored sul3, dfrA, and aadA1 determinants. Further genome analysis revealed different plasmid replicons associated with the mcr genes, IncX4 associated with mcr-1.1, and ColE10 with mcr-4.1. In addition, other replicons, including IncFIA, IncI1-Iγ, IncX1, IncY, in INIAV_002EC, and IncX1, IncI1, and p0111, in INIAV_001EC, were identified. Furthermore, both strains belonged to ST215 serotype O68:H12 and ST156 serotype O25:H28, respectively. This finding highlights the pig gut flora as a potential reservoir of mobile colistin resistance genes and reports the presence of the mcr-4.1 gene found for the first time in Portugal.

BACTERIOLOGY AND ANTIMICROBIAL SUSCEPTIBILITY OF OSTEOARTICULAR INFECTIONS AT A REGIONAL PAEDIATRIC UNIT IN SOUTH AFRICA

Osteoarticular infections (OAI) are a common cause of morbidity in children, and as opposed to adults is usually caused by haematogenous spread. The bacteriology of OAI in children is not well described in the South African context, therefore this study was designed to determine the bacteriology of OAI in our population.All patients that underwent surgery for the treatment of OAI over a 3-year period were identified and those with positive cultures where organisms were identified from tissue, pus, fluid or blood were included. Duplicate cultures from the same patient were excluded if the organism and antibiotic susceptibility profile was the same. Patients were categorised according to age and class of infection (Septic arthritis, acute osteomyelitis, fracture related infection, post-operative sepsis and chronic osteomyelitis) and organisms were stratified according to these categories.We identified 132 organisms from 123 samples collected from 86 patients. Most cultured organisms were from children older than 3-years with acute haematogenous septic arthritis, osteomyelitis, or both. Methicillin sensitive Staphylococcus aureus accounted for 56% (74/132) of organisms cultured. There were no cases of MRSA. The Enterobacterales accounted for 17% (22/132) of organisms cultured, mostly in the fracture related and post-operative infection groups. Of these, 6 each were extended spectrum B-lactamase producers and AmpC producers. There were no carbapenemase producing Enterobacterales. Kingella kingae was not isolated in any patient.Methicillin sensitive S. aureus is the most common infecting organism in paediatric OAI and an anti-staphylococcal penicillin such as cloxacillin or flucloxacillin is the most appropriate empiric treatment for haematogenous OAI in our environment. In fracture related or post-operative infections, Enterobacterales were more frequently cultured, and treatment should be guided by culture and susceptibility results.

Evaluation of ceftolozane-tazobactam susceptibility on a French nationwide collection of Enterobacterales

Ceftolozane-tazobactam (C/T) proved its efficacy for the treatment of infections caused by non-carbapenemase producing Pseudomonas aeruginosa and Enterobacterales. Here, we aimed to provide susceptibility data on a large series of Enterobacterales since the revision of EUCAST categorization breakpoints in 2020. First, C/T susceptibility was determined on characterized Enterobacterales resistant to third generation cephalosporins (3GCs) (extended spectrum β-lactamase [ESBL] production or different levels of AmpC overexpression) (n=213) and carbapenem-resistant Enterobacterales (CRE) (n=259), including 170 carbapenemase producers (CPE). Then, 1632 consecutive clinical Enterobacterales responsible for infection were prospectively collected in 23 French hospitals. C/T susceptibility was determined by E-test® (biomérieux) and broth microdilution (BMD) (Sensititre™, Thermo Scientific) to perform method comparison. Within the collection isolates, 88% of 3GC resistant strains were susceptible to C/T, with important variation depending on the resistance mechanism: 93% vs. 13% susceptibility for CTX-M and SHV-ESBL producers, respectively. Only 20% of the CRE were susceptible to C/T. Among CPE, 80% of OXA-48-like producers were susceptible to C/T, whereas all metallo-β-lactamase producers were resistant. The prospective study revealed that 95.6% of clinical isolates were susceptible to C/T. Method comparison performed on these 1632 clinical isolates demonstrated 99% of categorization agreement between MIC to C/T determined by E-test® in comparison with the BMD (reference) and only 74% of essential agreement. Overall, C/T showed good activity against wild-type Enterobacterales, AmpC producers, and ESBL-producing Escherichia coli but is less active against ESBL-producing Klebsiella pneumoniae, and CRE. E-test® led to an underestimation of the MICs in comparison to the BMD reference.

High-dose Cefepime vs Carbapenems for Bacteremia Caused by Enterobacterales With Moderate to High Risk of Clinically Significant AmpC β-lactamase Production.

Limited data suggest that serious infections caused by Enterobacterales with a moderate to high risk of clinically significant AmpC production can be successfully treated with cefepime if the cefepime minimum inhibitory concentration (MIC) is ≤2 µg/mL. However, isolates with a cefepime-susceptible dose-dependent (SDD) MIC of 4-8 µg/mL should receive a carbapenem due to target attainment and extended-spectrum β-lactamase (ESBL) concerns. This was a retrospective cohort study of hospitalized patients with E. cloacae, K. aerogenes, or C. freundii bacteremia from January 2015 to March 2022 receiving high-dose cefepime or a carbapenem. Cox regression models were used with incorporation of inverse probability of treatment weighting and time-varying covariates. Of the 315 patients included, 169 received cefepime and 146 received a carbapenem (ertapenem n = 90, meropenem n = 56). Cefepime was not associated with an increased risk of 30-day mortality compared with carbapenem therapy (adjusted hazard ratio [aHR], 1.45; 95% CI, 0.79-2.14), which was consistent for patients with cefepime SDD isolates (aHR, 1.19; 95% CI, 0.52-1.77). Multivariable weighted Cox models identified Pitt bacteremia score >4 (aHR, 1.41; 95% CI, 1.04-1.92), deep infection (aHR, 2.27; 95% CI, 1.21-4.32), and ceftriaxone-resistant AmpC-E (aHR, 1.32; 95% CI, 1.03-1.59) to be independent predictors associated with increased mortality risk, while receipt of prolonged-infusion β-lactam was protective (aHR, 0.67; 95% CI, 0.40-0.89). Among patients with bacteremia caused by Enterobacterales with moderate to high risk of clinically significant AmpC production, these data demonstrate similar risk of 30-day mortality for high-dose cefepime or a carbapenem as definitive β-lactam therapy.

Phenotypic Characterization of Carbapenemase-Producing Enterobacteriaceae Strains in a Referral Teaching Hospital in Yaoundé, Cameroon

Background: Carbapenemase-producing Enterobacteriaceae (CPE) are an important and increasing threat to global health. They are nowadays more encountered routinely in hospitals and cause high morbidity and mortality due to limited therapeutic alternatives. This study sought to determine the prevalence of CPE in Yaoundé teaching hospital, Cameroon, and the associated risk factors. Materials and Method: To achieve this goal, a descriptive cross-sectional study coupled to an analytical component with consecutive collection of Enterobacteria strains was carried out during a three-month period (from 27th July to 24th October 2018) in the University Teaching Hospital of Yaoundé, Cameroon. The oxidase and biochemical identification tests using a miniaturized Api 20 E system were performed on colonies grown on Eosin Methylene Blue (EMB) medium and subcultured on nutrient agar. Drug susceptibility testing was carried out according to the Antibiogram Committee of the French Society of Microbiology (CA-SFM 2018.V.2.0). The detection of carbapenemase production was performed by the CA-SFM 2018 algorithm for the screening of carbapenemase-producing enterobacteriaceae and its classification by inhibitory synergy tests. Results: Out of the 104 isolates, Escherichia coli (50%) was the most prevalent species, followed by Klebsiella pneumoniae (37.5%) and Citrobacter frendii (12.5%). Drugs susceptibility patterns showed a high resistance to penicillins group (97.4% to amoxicillin), cephalosporins (68.4% to cefotaxim, 58.1% to cefixim, 60.7% to ceftazidim, 57.1% of cefoxitin) and aztreonam (55.7%). However, 11.9% carbapenems related resistance was noticed: 14.4% to imipenem, 13.8% to ertapenem and 7.5% to meropenem. Numerous co-resistance to quinolones (65.8%), fluoroquinolones (49.6%), aminoglycosides (49.6%) and cotrimoxazole (71.8%) were also observed. From 104 isolates, AmpC production represented 23.08% (25/104) and 36.54% (38/104) were ESBL-isolates. The overall prevalence of CPE was 25% (26/104) with K.pneumoniae predominant (61.53%). Besides, Class A and class B carbapenemase were mainly produced with respectively 20% (21/104) and 5% (5/104). Univariate analysis revealed a significant association of carbapenemase production to Klebsiella pneumoniae (p = 0.01), ESBL and AmpC production ((P = 0.01 and P = 0.001 respectively) while that association was only significant to Klebsiella spp (p = 0.04) and AmpC production (p = 0.02) in multivariate analysis. Conclusion: The multi-resistance of Enterobacteriaceae to antibiotics in Cameroon has considerably increased. More attention should be paid to those bacteria to stall antimicrobial resistance spread.

Characterization of Extended Spectrum β-lactamase and AmpC Producing Organisms Isolated from a Third Level Hospital Patients in Dominican Republic

Extended-spectrum β-lactamases (ESBLs) producing Enterobacteriaceae have become a challenge for clinicians as they frequently show co-resistance to other antibiotic classes. AmpC-type β-lactamases (AmpCs), tend to be more difficult to treat as they could be induced during antibiotic therapy. To characterize ESBLs and AmpCs producing organisms, we collected clinical samples identified through MicroScan® as members of the Enterobacteriaceae family and ESBLs producers, following Clinical Laboratory Standards Institute indications, from January through March 2021, in a third level hospital in Santiago de Los Caballeros, Dominican Republic. Samples underwent manual confirmation via ESBL + AmpC screen discs kit (Liofichelm® srl, Italy) and a genotype analysis was done by DNA extraction for detection of specific genes related with ESBL ((blaSHV, blaTEM, blaCTX, and blaCMY-4) or AmpC (CIT, MOX, DHA and FOX) expression. 54 samples were confirmed as ESBL and/or AmpC producers with Escherichia coli as the most frequent (33/61%) followed by Klebsiella sp. (9/17%). blaCTX was detected in 29 (67%) isolates, followed by blaTEM (23/53%) and blaSHV (18 /40%) . Among the AmpC encoding genes, DHA and CIT gene pools were detected in 3 (7%) and 2 (5%) of the samples, respectively. Two or more genes were detected in 19 (44%) samples. All the AmpC genes were found in an isolate which already had, at least, two other β-lactamase encoding genes. In this cohort, ESBLs and AmpCs -producing organisms with multiple resistance genes were detected. Efforts to curb antibiotic availability and to establish antimicrobial stewardship programs are needed.

Multi-drug Resistance, β-Lactamases Production, and Coexistence of bla NDM-1 and mcr-1 in Escherichia coli Clinical Isolates From a Referral Hospital in Kathmandu, Nepal.

The ability of pathogenic Escherichia coli to produce carbapenemase enzymes is a characteristic that allows them to resist various antibiotics, including last-resort antibiotics like colistin and carbapenem. Our objectives were to identify rapidly developing antibiotic resistance (AR), assess β-lactamases production, and detect mcr-1 and bla NDM-1 genes in the isolates. A prospective cross-sectional study was carried out in a referral hospital located in Kathmandu from November 2019 to December 2020 using standard laboratory and molecular protocols. Among 77 total E. coli isolates, 64 (83.1%) of them were categorized as MDR. Phenotypically 13 (20.3%) colistin-resistant, 30 (46.9%) ESBL and 8 (12.5%) AmpC producers, and 5 (7.8%) ESBL/AmpC co-producers were distributed among MDR-E. coli. Minimum inhibitory concentrations (MIC) against the majority of MDR isolates were exhibited at 1 g/L. Of these 77 E. coli isolates, 24 (31.2%) were carbapenem-resistant. Among these carbapenem-resistant bacteria, 11 (45.9%) isolates were reported to be colistin-resistant, while 15 (62.5%) and 2 (8.3%) were MBL and KPC producers, respectively. Out of 15 MBL producers, 6 (40%) harbored bla NDM-1, and 8 (61.5%) out of 13 colistin-resistant pathogens possessed mcr-1. The resistance by colistin- and carbapenem were statistically associated (P < .001). However, only 2 (18.2%) of the co-resistant bacteria were found to have both genes. Our study revealed the highly prevalent MDR and the carbapenem-resistant E. coli and emphasized that the pathogens possess a wide range of capabilities to synthesize β-lactamases. These findings could assist to expand the understanding of AR in terms of enzyme production.

124. Activity of Novel b-Lactam/b-Lactamase Inhibitor (BL/BLI) Combinations Against AmpC-Producing Species Collected in United States Hospitals

Abstract Background Therapeutic options for Enterobacterales species known to overexpress chromosomal AmpC (AmpC producers) are limited since these organisms can develop resistance to BLs during therapy. Novel BL/BLIs, such as meropenem-vaborbactam (MEV), ceftazidime-avibactam (CZA), and imipenem-relebactam (IMR), display activity against isolates producing serine-carbapenemases, extended-spectrum β-lactamases, and AmpC enzymes. In this study, we evaluated the activity of novel BL/BLIs against a collection of AmpC producers collected in from US hospitals during 2021. Activity of newer BL/BLI combinations against AmpC producers Methods A total of 1,252 AmpC producers including were consecutively collected in 31 US hospitals. Isolates were susceptibility tested by reference broth microdilution methods. CLSI breakpoints were applied. Results The activity of new BL/BLIs is summarized displayed in the Figure. MEV (MIC50/90, 0.03/0.06 mg/L) and amikacin were the most active agents tested against these isolates, inhibiting 99.8%. CZA (MIC50/90, 0.12/0.5 mg/L) inhibited 99.5%. IMR (MIC50/90, 0.12/1 mg/L) was active against 95.9%. Cefepime and meropenem were active against 92.0% and 97.6% of these isolates, respectively. Piperacillin-tazobactam and ceftolozane-tazobactam (MIC50/90, 0.5/8 mg/L) displayed activity against 76.4% and 83.6% of the AmpC producers, respectively. Tigecycline was active against 96.8% of the isolates; only 53.8% of the isolates had a colistin MIC of ≤2 mg/L. A total of 39 (3.2%) AmpC producers were nonsusceptible to imipenem and/or meropenem. MEV (MIC50/90, 0.25/2 mg/L) was active against 92.3%. IRL (MIC50/90, 0.25/2 mg/L) and CZA (MIC50/90, 1/ &amp;gt; 32 mg/L) were active against 89.7% of the carbapenem nonsusceptible AmpC producers. Against cefepime-resistant AmpC producers (n=45; 3.6%), MEV, IMR, and CZA had 93.3%, 88.9%, and 86.7% activity. Conclusion Infections caused by AmpC producers often are challenging to treat. Understanding the activity of new BL/BLIs is important as the use of cefepime and meropenem can also lead to resistance to these agents. MEV, IRL, and CZA displayed good activity against AmpC producers. When analyzing carbapenem-nonsusceptible or cefepime-resistant isolates, MEV was slightly more active but more potent than other BL/BLI combinations. Disclosures Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Jennifer M. Streit, BS, MT(ASCP), Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Shionogi: Grant/Research Support Cecilia G. Carvalhaes, MD, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support Rodrigo E. Mendes, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Nabriva Therapeutics: Grant/Research Support|Office for Assistant Secretary of Defense for Health Affairs: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support|Spero Therapeutics: Grant/Research Support Dee Shortridge, PhD, AbbVie: Grant/Research Support|JMI Laboratory: Employee|Melinta: Grant/Research Support|Menarini: Grant/Research Support|Shionogi: Grant/Research Support.

2111. Impact of Colonization by Multi Drug Resistant Bacteria on Graft Survival, Risk of Infection, and Mortality in Recipients of Solid Organ Transplant: Systematic Review and Meta-analysis

Abstract Background Colonization with multi-drug resistant bacteria (MDR) in solid organ transplant (SOT) recipients increases the risk of post-transplant bacterial infection. MDR colonization impact on graft survival and mortality is not well established. Methods A search was executed by an expert librarian on PROSPERO, OVID Medline, Ovid EMBASE, Wiley Cochrane Library, ProQuest dissertations and Theses Global and SCOPUS, from inception until October 26, 2021. Adult SOT colonized with Methicillin resistant Staphylococcus aureus (MRSA), Vancomycin-resistant Enterococci (VRE), Extended-spectrum beta-lactamase (ESBL) or AmpC producing bacteria, carbapenem resistant Enterobacteriaceae (CRE), or MDR Pseudomonas were included and compared to non-colonized SOT. Pairs of reviewers screened abstracts and full studies for inclusion, and extracted data independently. We used RevMan to conduct a meta-analysis using random effects models to calculate the pooled risk ratio (RR) with 95% confidence interval (CI) for the incidence of infection, mortality, and graft failure. Statistical heterogeneity was determined using the I2 statistic. Figure-1 PRISMA chart, systemic review and metanalysis on Impact Of Colonization By Multi Drug Resistant Bacteria on Graft Survival, Risk of Infection, and Mortality in Recipients of Solid Organ Transplant. Results 59 articles spanning from 1989 to 2021 were included (Figure-1). Liver transplant (43 studies) and VRE colonization (17 studies) were the most common organ and MDR pathogen. MDR surveillance was performed by culture (71%) and PCR (6.7%). In liver transplant recipients, VRE and MRSA colonization were associated with increased infection risk, but not mortality (VRE infection: RR= 2.40 (95%CI 1.54-3.73; p&amp;lt; 0.001), I2= 66%; VRE mortality: RR= 1.64 (95%CI 0.88-3.05; p=0.12), I2= 44%; MRSA infection: RR= 4.07 (95%CI 2.66-6.24; p&amp;lt; 0.001), I2= 59%; MRSA mortality RR=1.47 (95%CI 0.79-2.76; p=0.23), I2= 35%). ESBL and CRE colonization were associated with increased risk of infection (ESBL: RR=9.87 (6.12-15.93); p&amp;lt; 0.001), I2=13%; CRE: RR= 13.64 (95%CI 5.73-32.47); p&amp;lt; 0.001), I2= 66%). CRE colonization was associated with increased mortality, RR=5.79 (95% CI 1.80-18.63; p=0.003), I2=0%. Conclusion While colonization with MRSA and VRE in liver transplant was not associated with increase mortality, CRE colonization was associated with almost 6-fold increased risk of death. These data should be taken into account when stratifying the risk of transplant. Disclosures Carlos Cervera, Associate Professor, Astra-Zeneca: Advisor/Consultant|AVIR Pharma: Grant/Research Support|AVIR Pharma: Honoraria|Lilly: Advisor/Consultant|Merck: Advisor/Consultant|Merck: Grant/Research Support|Merck: Honoraria|Sunovion: Advisor/Consultant|Takeda: Advisor/Consultant|Takeda: Honoraria|VerityPharma: Advisor/Consultant Dima Kabbani, MD, MSc, AVIR Pharma: Grant/Research Support|AVIR Pharma: Honoraria|GSK: Honoraria|Merck: Grant/Research Support.

1863. Treatment and Outcomes of Cefoxitin-Non-Susceptible Serratia marcescens, Klebsiella aerogenes, Citrobacter freundii, Enterobacter cloacae, and Morganella morganii Bacteremia with Piperacillin/Tazobactam Versus Cefepime or Carbapenem in Immunocompromised Patients

Abstract Background A recent guidance suggested “caution if prescribing piperacillin-tazobactam for serious infections caused by organisms at high risk of significant AmpC production” and that the preferred antibiotic choice should be either cefepime or a carbapenem, despite an admitted lack of definitive evidence. Examination of this question in immunocompromised patients may provide such evidence. Methods This was a retrospective, single-center study conducted from January 2016 to December 2021. We included immunocompromised patients aged 18 years or older who had a laboratory confirmed blood culture positive for Enterobacterales showing non-susceptibility to cefoxitin and were definitively treated with piperacillin-tazobactam, cefepime, or a carbapenem. The primary endpoint was a composite of clinical or microbiological failure, which was comprised of in-hospital 30-day mortality, white blood count &amp;gt;12 x 109/L or temperature &amp;gt;38°C on days 5-7, microbiological failure on days 3-5, or microbiological recurrence/relapse on days 5-30. Results We identified 81 patients who were included for analysis. Baseline characteristics between arms were similar between groups except for more frequent severe neutropenia (p=0.010) and higher Pitt bacteremia scores (p=0.042) in the cefepime/carbapenem group. Within the piperacillin/tazobactam arm, 17 of 35 (48.6%) had clinical or microbiological failure, compared to 17 of 46 (37.0%) patients in the carbapenem/cefepime arm (p=0.294). Microbiological failure occurred in 4 of 35 (11.4%) patients treated with piperacillin/tazobactam compared to 0 of 46 (0%) patients treated with a carbapenem/cefepime (p=0.019). In multivariate analysis, patients treated with a carbapenem/cefepime had a 69% lower odds of clinical or microbiological failure compared to those treated with piperacillin/tazobactam (OR = 0.31; 95% confidence interval, 0.10-0.98). Conclusion In immunocompromised patients with bacteremia due to cefoxitin-non-susceptible Serratia marcescens, Klebsiella aerogenes, Citrobacter freundii, Enterobacter cloacae, or Morganella morganii, definitive treatment with piperacillin/tazobactam was associated with a higher likelihood of microbiological failure compared with treatment with a carbapenem or cefepime. Disclosures All Authors: No reported disclosures.

Detection of ESBL and AmpC producing Klebsiella pneumoniae ST11 and ST147 from urinary tract infections in Iran.

In the present study a total of 200 Klebsiella pneumoniae isolates were collected from patients with urinary tract infections (UTIs) in Tehran, Iran. Antibiotic resistance was determined by disk diffusion and broth dilution methods. Detection of extended-spectrum β-lactamases (ESBLs) and AmpCs was performed using phenotypic tests. Polymerase chain reaction (PCR) was applied to detect the ESBL, AmpC, and integron genes. Analysis of AmpC and cassette arrays of integron genes was performed using DNA sequencing. Plasmids were analyzed by PCR-based replicon typing and conjugation. Pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST) were applied to explore the genomic relatedness among the isolates. The highest levels of resistance were observed against ampicillin (100%), followed by piperacillin (57.5%), ceftazidime (46%), trimethoprim/sulfamethoxazole (44%), ciprofloxacin (32.5%), and imipenem (19%). Approximately, 66.5% of isolates harbored at least one of the beta-lactamase genes (blaTEM, blaSHV, blaCTX-M, and blaOXA-1). In addition, 22.5% of isolates carried at least one of the AmpC genes including blaDHA and blaCIT. Integron class I was the most prevalent integron among resistant isolates. According to the results of replicon typing, IncFII, IncL/M, and IncA/C were the most frequent replicons, respectively. All selected isolates were able to transfer blaCTX-M, also two isolates transferred the blaDHA-1 gene to Escherichia coli K12 through conjugation. Finally, 21 isolates were categorized into 4 pulsotypes and 11 unique clusters in PFGE. MLST identified ST147 and ST11 sequence types but ST147 was the most prevalent in the current study.

Fosfomycin susceptibility among Escherichia coli causing urinary tract infection in a tertiary care centre in Western Maharashtra

Background and objective: Urinary tract infection(UTI) is one of the most common bacterial infections encountered in clinical practice. UTIs caused by extended-spectrum beta-lactamase (ESBL) AmpC and metallo-beta-lactamase (MBL) producing Escherichia coli (E. coli) are difficult to treat. Fosfomycin is an old antibiotic that has excellent bactericidal activity against a wide range of bacteria. This study aimed to determine the fosfomycin susceptibility of E. coli causing UTI in a tertiary care hospital in Western Maharashtra, India. Material and methods: The study was conducted at a tertiary care center in Pune, a city of Western Maharashtra, India. Urine samples from UTI cases yielding significant (&gt; 1x 105 cfu/ml) growth of E. coli were included in study. E. coli isolates were tested for susceptibility to fosfomycin and a panel of antimicrobial agents by Kirby Bauer disc diffusion method. All the isolates were tested for production of ESBL, AmpC and MBL. Result: A total of 88 E. coli were isolated of which, 47 (53.40%) and 41 (46.59%) were from male and female patients respectively. Of the total E. coli isolates, 58 (65.9%) were from in-patient cases. Multi-drug resistance was found in 69 (78.40%) isolates and remaining 19 (21.6%) were resistant to different antimicrobials tested. All (100%) the MDR and non-MDR isolates were sensitive to fosfomycin. Highest resistance was present against nalidixic acid (93.8%) while resistance was least against nitrofurantoin (15.91%), piperacillin/tazobactam (17.1%) and meropenem (18.18%). Of the total, 35 (50.72%) isolates were both AmpC and ESBL producers while 11 (15.94%) and 8 (11.59%) were only AmpC and ESBL producers respectively. MBL was positive in 15 (21.73%) of E. coli isolates. All those isolates tested sensitive to fosfomycin. Conclusion: The study revealed that fosfomycin had excellent activity against MDR E. coli causing UTI in our area. IMC J Med Sci. 2023; 17(1): 008. DOI: https://doi.org/10.55010/imcjms.17.008 *Correspondence: Dr. Sameena Khan, Department of Microbiology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India. E-mail: sameenak27@gmail.com

Therapeutic options for extended-spectrum β-lactamases (ESBLs), AmpC β-lactamases producing Escherichia coli and Klebsiella sp. isolated from various clinical samples

Escherichia coli and Klebsiella sp. are the predominant species isolated from clinical samples. Recent and proper understanding of the antibiotic susceptibility pattern of extended-spectrum β-lactamases (ESBL) and AmpC β-lactamases (AmpC) producing E. coli and Klebsiella sp. will prevent the distribution and future incidence of ESBL and AmpC. We designed this study to understand antibiotic susceptibility patterns of ESBL and AmpC producing E. coli and Klebsiella sp. isolated from a tertiary care hospital in North India. A cross-sectional study was conducted from March 2021 to February 2022. Guring this period, various clinical samples were collected and further tested for ESBL producing E. coli and Klebsiella sp. by using the Double disc Synergy test, whereas AmpC was detected by the Boronic acid disk potentiation method. Their antibiotic susceptibility patterns were noted. Various clinical specimens were collected, in which 37.95% were shown growth of bacteria. Among them, 46.67% of E. coli and 25.21% of Klebsiella sp. were identified by standard laboratory protocol. ESBL producing isolates were 44.37% and 34.20% in E. coli and Klebsiella sp., respectively. Whereas AmpC production was detected in 18.27% of E. coli and 29.36% of Klebsiella sp. ESBL and AmpC producing E. coli and Klebsiella sp. isolated from pus, blood, and sputum samples showed the highest sensitivity towards colistin, tigecycline, and imipenem while in urine samples imipenem, meropenem showed the highest sensitivity. Susceptibility patterns of ESBL and AmpC producing E. coli and Klebsiella sp. from various clinical specimens enhance hospital infection management and help clinicians to prescribe the appropriate antibiotics. The carbapenem, nitrofurantoin, colistin and tigecycline were showed highest susceptible against ESBL and AmpC producing E. coli and Klebsiella sp.

Detection of beta-lactam antibiotic resistance in aquatic Enterobacteriaceae isolates

Abstract Production of the beta-lactamase enzymes is the primary resistance mechanism caused by unconcious consumption of the beta-lactam group of antibiotics in Enterobacteriaceae. Combined disc tests were performed for extended-spectrum beta-lactamase (ESBL) confirmation (n = 15) and class C beta-lactamase (AmpC) confirmation (n = 6) after the disc diffusion test was applied in a total of 27 Enterobacteriaceae strains from Western Black Sea, Lake Manyas and Lake Iznik. Plasmid-mediated blaTEM, blaSHV, blaCTX-M , blaIMP genes, CIT, MOX, FOX gene groups and chromosomal blaAmpc gene of E. cloacae were investigated using the polymerase chain reaction (PCR). Three E. coli strains were shown to produce ESBL, while one E.coli and three E. cloacae strains were confirmed for AmpC production by disc tests. blaTEM (n = 2), blaSHV (n = 4), blaCTX-M (n = 2), blaTEM + blaSHV (n = 1), blaCTX-M + CIT (n = 1), blaSHV + CIT (n = 1) genes and/or gene groups were detected in 11 E. coli isolates; while blaSHV (n = 3) was observed in three Klebsiella strains (two K. oxytoca and one K. pneumoniae). With this study, the aquatic environments of Turkey were proved to be the reservoirs of antibiotic-resistance determinants of plasmid-mediated beta-lactamases in environmental wild-type bacteria transmitted by horizontal gene transfer.

Antibiotic Resistance of Clinical Klebsiella Isolates from Tertiary Care Hospital

Klebsiella is a pathogen that causes a significantly high number of community-acquired and hospital-acquired infections, with infections being one of the leading causes of death in ICU patients worldwide due to increasing antibiotic-resistance and a lack of therapeutic options. A total of 230 Klebsiella spp. were collected from various clinical samples. After initial identification, the drug-resistant strain was subjected to standard Clinical Laboratory and Standards Institute methods such as Kirby–Bauer disc diffusion. All isolates were screened and confirmed for ESBL/AmpC β-lactamase/carbapenemase production. The isolated Klebsiella spp. were found to be K. pneumonia (89%), K. oxytoca (6.5%), and K. aerogenes (4.5%). Among the 230 isolates, 80 (34.7%) isolates were found to be ESBL producers via screening; of these, 53 (23.5%) were verified by a confirmatory test. Moreover, 115 isolates (50%) were screened as AmpC producers; of these, 23 isolates (10%) were verified by a confirmatory test. Carbapenemase producers accounted for 69 (30%) isolates, identified by screening; 25 (10.86%) were verified by a confirmatory test. ESBL producers accounted for the majority of Klebsiella spp. isolates, followed by carbapenem and AmpC producing strains.

Dissemination of High-Risk Clones Enterobacterales among Bulgarian Fecal Carriage Isolates

The gastrointestinal tract is an important reservoir of high-risk Enterobacteria clones and a driver of antimicrobial resistance in hospitals. In this study, patients from six hospitals in four major Bulgarian towns were included in this study. Overall, 205 cefotaxime-resistant isolates (35.3%) of Enterobacterales order were detected in fecal samples among 580 patients during the period of 2017-2019. ESBL/carbapenemase/plasmidic AmpC producer rates were 28.8%, 2.4%, and 1.2%, respectively. A wide variety of ESBLs: CTX-M-15 (41%), CTX-M-3 (24%), CTX-M-27 (11%), and CTX-M-14 (4%) was found. The carbapenemases identified in this study were New Delhi metalo-β-lactamase (NDM)-1 (5.4%) and Klebsiella carbapenemase (KPC)-2 (1.5%). Most NDM-1 isolates also produced CTX-M-15/-3 and CMY-4 β-lactamases. They belonged to ST11 Klebsiella pneumoniae clone. The epidemiology typing revealed three main high-risk K. pneumoniae clones (26%)-ST11, ST258, and ST15 and five main Escherichia coli clones-ST131 (41.7%), ST38, ST95, ST405, and ST69. Sixty-one percent of ST131 isolates were from the highly virulent epidemic clone O25b:H4-ST131. Phylotyping revealed that 69% of E. coli isolates belonged to the virulent B2 and D groups. Almost all (15/16) Enterobacter isolates were identified as E. hormaechei and the most common ST type was ST90. Among all of the isolates, a high ESBL/carbapenemases/plasmid AmpC (32.4%) prevalence was observed. A significant proportion of the isolates (37%) were members of high-risk clones including two pan-drug-resistant K. pneumoniae ST11 NDM-1 producing isolates. Due to extensive antibiotic usage during COVID-19, the situation may worsen, so routine screenings and strict infection control measures should be widely implemented.

Genome-associations of extended-spectrum ß-lactamase producing (ESBL) or AmpC producing E. coli in small and medium pig farms from Khon Kaen province, Thailand

Thailand is undergoing rapid intensification of livestock production where small subsistence farms and medium sized commercial farms coexist. In medium farms, antimicrobials are prescribed by a veterinarian, whereas in small farms antimicrobial use remains largely unsupervised. The impact of these differences as well as other farming practices on the emergence and composition of antimicrobial resistance genes (ARGs) remains largely unknown. We analyzed 363 genomes of extended-spectrum ß-lactamase producing (ESBL) and/or AmpC producing Escherichia coli recovered from humans and pigs at small and medium farms from the Khon Kaen province, Thailand. We tested for genome-wide associations to identify links between ARGs, host, and farm size. Pig isolates from small farms were associated with mcr and qnr genes conferring resistance to colistin and fluoroquinolones, respectively. In contrast, pig isolates from medium farms were associated with ARGs conferring resistance to drugs commonly used on medium farms (i.e., streptomycin). ESBL plasmids from small farms co-carried ARGs conferring resistance to critically important antimicrobials more frequently compared to plasmid from medium farms. Frequent ARG combinations included blaCTX-M-55 + qnrS1 (29.8% vs 17.5% in small and medium farms, respectively), blaCTX-M-55 + qnrS1 + mcr-3.19 (5% vs 0%), blaCTX-M-14 + qnrS1 (9.3% vs 6.2%), and blaCTX-M-14 + qnrS1 + mcr-1.1 (3.1% vs 0%). The co-location on plasmids of ARGs conferring resistance to critically important antimicrobials as defined by the World Health Organization is concerning, and actions to curb their spread are urgently needed. Legislation on limiting antimicrobial sales and initiatives to better inform farmers and veterinarians on appropriate antimicrobial usage and farm biosecurity could help reduce antimicrobial use on farms.

Long-Term Effects of Single-Dose Cephalosporin or Macrolide Use on the Prevalence of AmpC and Extended-Spectrum β-Lactamase Producing Escherichia coli in the Feces of Beef Cattle.

Extended-spectrum-β-lactamase (ESBL) and AmpC-lactamase-producing Enterobacteriaceae are serious public health threats. Due to an increasing number of reports of ESBL and AmpC producing Escherichia coli in agricultural settings, it is critical to understand the relationship between the use of two of the highest priority critically important human antibiotics (e.g., third generation cephalosporins [3GC] and macrolides) in food animals and their potential contribution to the selection of ESBL/AmpC E. coli. The objective of our randomized controlled feedlot trial was to measure the effects of ceftiofur crystalline-free acid and tulathromycin on 3GC resistant fecal E. coli populations in cattle before and at various time points after treatment up to and including at slaughter. Multi-level mixed-effects linear regression showed no effect of ceftiofur and tulathromycin on 3GC E. coli CFU counts at slaughter (Day 99); however, a significant (p < 0.05) population shift was observed from susceptible to 3GC resistant E. coli immediately after ceftiofur administration (Day 7). Among 799 fecal samples screened using selective media, 17.7% were ESBL/AmpC E. coli positive, which were further tested for phenotypic antibiotic susceptibility. The majority of the isolates from these plates were multidrug-resistant (94.3%) and expressed either AmpC (78.1%) or ESBL (28.1%) phenotype. A subset of isolates was whole-genome sequenced (n = 20) and identified to harbor chromosomal and/or plasmidal bla genes such as CMY-2, CTX-M, and TEM. Our findings show a time-dependent selection of antibiotics on 3GC-resistant E. coli. High prevalence of multidrug-resistant ESBL/AmpC E. coli found in cattle feces highlights the importance of prudent use of antibiotics in livestock.