Carbapenem Non-susceptible Isolates Research Articles

In vitro activity assessment of cefiderocol against Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter spp., including β-lactam nonsusceptible molecularly characterized isolates, collected from 2020 to 2021 in the United States and European hospitals.

This study reports the activity of cefiderocol against Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter spp. isolates collected from the United States and Europe, including Israel and Turkey, from 2020 to 2021. Among Enterobacterales, 2.8% were carbapenem nonsusceptible (CNSE); cefiderocol inhibited 96.6%/85.1% [Clinical Laboratory Standards Institute (CLSI)/European Committee on Antimicrobial Susceptibility Testing (EUCAST) breakpoints] of these isolates. Imipenem-relebactam, meropenem-vaborbactam, and ceftazidime-avibactam displayed susceptibilities lower than cefiderocol against CNSE isolates (67.4-84.6% susceptible, CLSI). Cefiderocol was the only agent active against CNSE isolates carrying metallo-β-lactamase (MBL) carbapenemase or multiple carbapenemase genes (84.6%-92.3% susceptible, CLSI). Approximately 18% of carbapenem-susceptible Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis carried extended-spectrum-β-lactamases and/or plasmid-borne AmpC-encoding genes; cefiderocol inhibited 99.8%-100.0% (CLSI) of these genotypic groups. Multi-drug resistance (MDR) phenotypes were observed in 16.9% and 52.5% of P. aeruginosa and A. baumannii-calcoaceticus isolates, respectively. Carbapenemase genes were rare (4.9%) among cephalosporin and/or carbapenem nonsusceptible P. aeruginosa, compared to 87.6% carriage in A. baumannii-calcoaceticus, respectively. Against the MDR and carbapenemase-carrying P. aeruginosa and A. baumannii-calcoaceticus subsets, cefiderocol was active against 98.6%/98.7% and 97.1%/97.4% (CLSI), respectively. Only 69 isolates (0.3%) across all species groups were identified as cefiderocol nonsusceptible per CLSI criteria (>4 mg/L). Cefiderocol was the most active agent in vitro against Enterobacterales, P. aeruginosa, and Acinetobacter spp., with uniform activity against all phenotypic- and genotypic-resistant subsets. Coupled with the low incidence of nonsusceptibility observed across species groups, these results demonstrate cefiderocol as an important option for treating infections caused by pathogens with diverse mechanisms of resistance in US and European hospitals.IMPORTANCEThe worldwide spread of multi-drug-resistant Pseudomonas aeruginosa and carbapenem-resistant Enterobacterales and Acinetobacter spp. poses a serious challenge in healthcare settings as infections caused by these organisms are commonly refractory to many frontline therapeutic agents. Multiple global health organizations highlighted these pathogens as critical priorities for new antibiotic development, thus necessitating continued surveillance of the activities of currently available antimicrobial agents and circulating mechanisms of resistance. To meet this need, this study phenotypically and genotypically characterized priority Gram-negative pathogens collected from patients in US and European hospitals to examine the activity of cefiderocol and other currently available treatment options, including carbapenems and β-lactam-β-lactamase inhibitor combinations. The results presented here provide a detailed perspective to healthcare practitioners of cefiderocol's broad applicability, manifested in high activity and low nonsusceptibility rates, across phenotypic and genotypic organism groups relative to other agents and further support its use against the most intransigent infections.

Evaluation of the BD Phoenix Carbapenemase-Producing Organism Panels for the Detection of Carbapenemase Producers in Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa.

The classification of carbapenemases can help guide therapy. The present study evaluated the performance of the CPO detection test, included in the BD Phoenix™ NMIC-501 panel for the detection and classification of carbapenemases on the representative molecularly characterized strains collection from Mexico. Carbapenem non-susceptible isolates collected in Mexico were included. The clinical isolates (n = 484) comprised Klebsiella pneumoniae (n = 154), Escherichia coli (n = 150), and P. aeruginosa (n = 180). BD Phoenix CPO NMIC-504 and NMIC-501 panels were used for the identification of species, antimicrobial susceptibility tests, and detection of CPOs. For the detection of carbapenemase-encoding genes, E. coli and K. pneumoniae were evaluated using PCR assays for blaNDM-1, blaKPC, blaVIM, blaIMP, and blaOXA-48-like. For P. aeruginosa, blaVIM, blaIMP, and blaGES were detected using PCR. Regarding E. coli, the CPO panels had a sensitivity of 70% and specificity of 83.33% for the detection of a class B carbapenemase (blaNDM in the molecular test). Regarding K. pneumoniae, the panels had a sensitivity of 75% and specificity of 100% for the detection of a class A carbapenemase (blaKPC in the molecular test). The Phoenix NMIC-501 panels are reliable for detecting class B carbapenemases in E. coli. The carbapenemase classification in K. pneumoniae for class A carbapenemases has a high specificity and PPV; thus, a positive result is of high value.

Imipenem and meropenem influence the Las/Rhl quorum-sensing systems in clinical isolates of Pseudomonas aeruginosa.

The present study was conducted to study the influence of imipenem and meropenem at subinhibitory concentration on the transcriptional response of Las/Rhl quorum-sensing systems in isolates of Pseudomonas aeruginosa. In the present study, six representative carbapenem nonsusceptible clinical isolates of P. aeruginosa were obtained. The agar dilution method was used to determine the minimum inhibitory concentration against imipenem and meropenem. The bacterial isolates were then cultured up to the early log phase in fresh Luria Bertani (LB) broths at 37°C with and without 2 µg mL-1 imipenem and meropenem, respectively. mRNA was then isolated from the bacterial isolates and was immediately reverse-transcribed to cDNA. The relative quantity of the expression of the lasI, lasR, rhlI, and rhlR genes was assessed by quantitative real-time Polymerase Chain Reaction (PCR) using the ΔΔCt method. The transcriptional response of the lasI and lasR genes was upregulated at subinhibitory concentration of meropenem. In contrast, the transcriptional response of the lasI, lasR, and rhlR genes was downregulated at subinhibitory concentration of imipenem as compared to the expression in untreated isolates. The data obtained in the current study showcased the ability of imipenem and meropenem to influence the response of the quorum-sensing genes at subinhibitory concentration.

Comparison of prevalence, resistance, biofilm-forming ability and virulence between carbapenem-non-susceptible and carbepenem-susceptible Enterobacter cloacae complex in clusters

This study aimed to explore the differences of prevalence, resistance, biofilm, and virulence between carbapenem nonsusceptible and susceptible Enterobacter cloacae complex (ECC) in different clusters. Ninety-one carbapenem nonsusceptible isolates and an equal number of susceptible isolates as well as their clinical information were collected from a university teaching hospital in China. The strains were divided into different clusters according to the analysis based on hsp60. Agar dilution method was used to determine the MICs of common antibiotics. Crystal violet assay was used to measure biofilm-forming ability. Galleria mellonella infection model and PCR of virulence genes were used to evaluate the virulence. The isolates were divided into 12 clusters based on the hsp60 analysis. Cluster VIII accounted for a predominant and higher proportion of carbapenem nonsusceptible isolates than the other clusters. The same clusters exhibited different resistance rates in carbapenem nonsusceptible and susceptible isolates. Moreover, carbapenem nonsusceptible isolates carried fewer virulence genes than susceptible isolates, and cluster II in carbapenem nonsusceptible isolates didn't carry the detected virulence genes. The virulence of clusters I, III, VIII, and IX was significantly different between the nonsusceptible and susceptible isolates, as evaluated using the Galleria mellonella infection model. Cluster VIII accounted for a predominant and higher proportion as well as higher resistance, biofilm formation ability, and pathogenicity in carbapenem nonsusceptible isolates than the other clusters. This finding indicated the necessity to identify subgroups of ECC and provide better advice and guidance for the use of carbapenem.

Carbapenem-resistant Enterobacterales susceptibility patterns to new antimicrobials: A single-center analysis

Background: Multidrug-resistant bacteria are of high concern, and empiric antimicrobial choice for infections caused by these pathogens, while awaiting susceptibilities, is increasingly encountered. We describe the susceptibility patterns of ceftazidime-avibactam (CZA), imipenem-rel-ebactam (I-R), meropenem-vaborbactam (MVB), cefiderocol (FDC), ceftolozone-tazobactam (C/T), minocycline (MIN), and tigecycline (TGC) for carbapenem-resistant Enterobacterales at an academic medical center. Methods: We performed a single-center analysis of Enterobacterales isolates from 110 hospitalized adult patients who had CZA, I-R, MVB, FDC, MIN, or TGC susceptibility testing performed between October 2020 and September 2022. The study included 1 isolate per patient per infection site per year. Isolates were divided into carbapenem susceptible and non susceptible categories. For carbapenem nonsusceptible isolates, phenotypic confirmatory testing of carbapenem nonsusceptibility was performed using disk diffusion, gradient diffusion, and/or broth microdilution. Interpretive categories were applied using CLSI- or FDA-approved break-points where applicable. Carbapenemase testing was also performed using the modified carbapenem inactivation method (mCIM) and, where applicable, this testing was confirmed at the Massachusetts State Public Health Laboratory using genotypic methods. Results: In total, 125 unique isolates were reviewed: 34 meropenem-susceptible and 91 meropenem-intermediate or resistant isolates. CZA, I-R, MVB, and FDC were active against all tested meropenem-susceptible isolates; however, 50% of tested isolates were susceptible to C/T. MIN and TGC, when tested, were active against 2 of 11 isolates (18%) and 14 of 16 isolates (86%), respectively. Of 91 meropenem-nonsusceptible isolates, most tested isolates were susceptible to MVB (59 of 72, 82%), followed by CZA (63 of 82, 77%), I-R (8 of 11, 73%), FDC (9 of 16, 56%), and C/T (1 of 12, 8%). TGC retained activity against 78 of 81 (96%) tested isolates. In contrast, MIN retained activity against 8 of 45 isolates (18%). Additionally, all (28 of 28, 100%) isolates that were nonsusceptible to at least 1 novel agent (CZA, I-R, MVB, FDC, or C/T) remained susceptible to TGC. State laboratory confirmatory testing was available for 75 isolates. Of 43 mCIM-positive isolates, all 28 KPC-producing isolates were susceptible to CZA, I-R, MVB, FDC and TGC. Conclusions: Among Enterobacterales, CZA, MVB, and I-R retained activity against most non-NDM CRE isolates in this local analysis, with comparable susceptibilities. TGC demonstrated excellent susceptibility for CRE and meropenem-susceptible isolates, offering an alternative for nonbloodstream infections. Choice of empiric agent with a newβ-lactam, β-lactam–β-lactamase inhibitors, or TGC appear to be reasonable empiric therapeutic options at our institution. CT and MIN warrant confirmatory testing prior to use due to low susceptibility rates among meropenem nonsusceptible isolates.Disclosures: None

Carbapenem resistance among Gram-negative isolates collected from patients in ICU and non-ICU hospital wards in Hong Kong: SMART 2017–2020

To estimate carbapenem resistance in Pseudomonas aeruginosa and Enterobacterales isolated from infected patients in intensive-care unit (ICU) and non-ICU hospital wards in Hong Kong. Isolates of P. aeruginosa (ICU, n=35; non-ICU, n=264) and Enterobacterales (ICU, n=129; non-ICU, n=1390) were collected in four Hong Kong hospitals in 2017-2020. CLSI broth microdilution MICs were interpreted by CLSI 2021 M100 breakpoints. β-lactamase genes were identified in imipenem-, imipenem/relebactam-, and ceftolozane/tazobactam-non-susceptible isolates. Ceftolozane/tazobactam demonstrated potent in vitro activity against both P. aeruginosa (ICU, 88.6%; non-ICU, 98.5%) and Enterobacterales (96.1% susceptible; 97.1%). Percent susceptible values for P. aeruginosa isolates from ICU and non-ICU patients were: meropenem (ICU, 74.3%; non-ICU, 84.1%) and imipenem (68.6%; 73.1%). Only one of 77 isolates tested for β-lactamase genes carried a carbapenemase (VIM-2). Percent susceptible values for Enterobacterales isolates from ICU and non-ICU patients were: meropenem (100%; 99.4%), ertapenem (100%; 98.0%), and imipenem (88.4%; 88.6%). 62 Enterobacterales isolates were tested for β-lactamase genes. Only three isolates carried a carbapenemase gene; two (both Escherichia coli) were metallo-β-lactamase-positive (both NDM-5) and one (Klebsiella pneumoniae) was OXA-48-like-positive. Carbapenem-nonsusceptible isolates of P. aeruginosa were common (>15% of isolates). P. aeruginosa percent susceptible values to ceftolozane/tazobactam (97.3% susceptible overall) were ≥14% higher than carbapenems for both ICU and non-ICU isolates. Carbapenemases were rare among both P. aeruginosa (one isolate) and Enterobacterales (three isolates). Most Enterobacterales isolates tested from ICU and non-ICU patients in Hong Kong hospitals in 2017-2020 were susceptible to meropenem and ertapenem (≥98%); imipenem was less active (89% susceptible).

2036. Dual VIM-producing Proteus mirabilis, Including a Novel VIM-75, Among Elderly Patients in a Medical Center from Hungary: Report from the 2020 SENTRY Antimicrobial Surveillance Program

Abstract Background Nonsusceptibility of Proteus mirabilis to imipenem allows this pathogen evade surveillance for carbapenemases. Metallo-beta-lactamases of the VIM family are widespread among Enterobacterales in Europe. We identified an outbreak of P. mirabilis carrying 2 VIM enzymes among elderly patients from a medical center in Hungary. Methods A total of 16 P. mirabilis isolates were received from Hungary during 2020 as part of the SENTRY Antimicrobial Surveillance Program. Isolates were susceptibility tested by the CLSI reference broth microdilution method. Carbapenem-nonsusceptible isolates were submitted to whole genome sequencing, screened for resistance mechanisms, and evaluated for core genome multi-locus sequence typing (cgMLST). Results Among the 16 P. mirabilis isolates from Hungary, 5 carbapenem-nonsusceptible, multidrug-resistant isolates (3 from urinary tract infections and 1 each from bloodstream infection and pneumonia) were identified from patients 66-92 years old. Four of these 5 isolates were listed as community acquired. All isolates were resistant to ceftriaxone (MIC, > 8 mg/L), cefepime (16- > 32), imipenem ( > 8), gentamicin ( > 16), levofloxacin (16- > 32), nitrofurantoin ( > 64), trimethoprim/sulfamethoxazole ( > 4), and plazomicin ( > 128), but susceptible to meropenem (0.25-0.5) and ertapenem (0.03-0.25). Isolates carried blaVIM-4 and blaVIM-75 on a class 1 integron within IS26 and separated by aac(6’)-IIc. IS26 was located on a compound plasmid carrying other resistance-encoding genes, including armA. The integron structure is identical to the blaVIM-4 and blaVIM-1-carrying integron described from a Vibrio cholerae isolated from a seagull in France in 2015 (KR262557). blaVIM-75 is a single amino acid variant (Q60R) of blaVIM-1. All isolates carried mutations in the QRDR (gyrA_S83I, parC_S84I). Based on cgMLST analysis, these 5 P. mirabilis isolates were highly similar, with only 7-19 SNPs detected. Conclusion The outbreak of multidrug-resistant P. mirabilis isolates carrying blaVIM-4 and blaVIM-75 in a Hungarian medical center is a cause of concern. Surveillance should be performed to understand the spread of and treatment options for infections caused by carbapenem-nonsusceptible P. mirabilis. Disclosures Lalitagauri M. Deshpande, PhD, Melinta: Grant/Research Support|Pfizer: Grant/Research Support Katalin Burián, MD, JMI Laboratories: Grant/Research Support Ilona Dóczi Csányi, MD, JMI Laboratories: Grant/Research Support 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.

89. On-going impact of the SARS-CoV-2 pandemic on the evolution of carbapenemase-producing Enterobacterales in Ontario, Canada

Abstract Background The spread of carbapenemase-producing Enterobacterales (CPE) is global threat. Numerous outbreaks of CPE have been reported during the COVID-19 pandemic. We describe the impact of of the SARS-CoV-2 pandemic on the emergence of CPE in south-central Ontario, Canada. Incidence of clinical isolates of CPE and isolates with different CPE genes in Toronto/Peel region, 2017–2021. The upper panel shows the incidence of patients with clinical isolates of CPE by year and quarter from q4 2007 to q1 2022. The lower panel shows the incidence of patients with clinical isolates with different carbapenemase genes by fiscal year during the same period. Methods TIBDN has performed population-based surveillance for CPE in Toronto/Peel region (pop 4.5M) from first identified isolate in 2007. All laboratories test/refer all carbapenem non-susceptible Enterobacterial isolates for identification of CPE. Hospital charts are reviewed and patients/physicians interviewed. Population data are obtained from Statistics Canada. Results From 10/2007 to 3/31/2022, 1367 persons colonized or infected with CPE were identified. Their median age was 68.7yrs (IQR 54–78yrs); 761 (56%) were male. 772 (56%) were colonized when first identified; 115 (8.4%) were bacteremic at identification or subsequently developed bacteremia. The most common organisms were E. coli (651, 48%), K. pneumoniae (436, 32%), Enterobacter spp. (146, 11%), Citrobacter spp (62, 5%); the most common genes were NDM±OXA-48 (722, 53%), OXA-48-like (341, 25%), KPC (225, 16%), VIM (44, 3%). The incidence of CPE infections increased steadily until 3/2020 then declined by 61% and remained stable until 3/2022 (Figure, upper panel). The decline was greater for E. coli (56% decrease), K. pneumoniae (62%) than for Enterobacter spp. (30%) and other species (19%). It occurred in all genes in 2020; however, KPC containing organisms increased again in 2021 (Figure, lower panel). Conclusion The advent of the COVID-19 pandemic was associated with an immediate, substantial decline in the incidence of patients with CPE in our population area. This decline occurred in both isolates with genes usually occurring in cases imported from other countries, and in those usually occurring in cases associated with transmission within Canadian hospitals. Decreased travel and enhanced infection prevention and control in hospitals may both have contributed to reductions in CPE during the pandemic. Disclosures All Authors: No reported disclosures.

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/ > 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.

Molecular Epidemiology of New Delhi Metallo-β-Lactamase-Producing Escherichia coli in Food-Producing Animals in China

We conducted a molecular surveillance study for carbapenem-resistant Enterobacteriaceae (CRE) colonization in food-producing animals in China that included primarily swine and poultry for three consecutive years. A total of 2,771 samples from food-producing animals and their surrounding environments were collected from different regions in China from 2015 to 2017. Enrichment cultures supplemented with meropenem were used to isolate carbapenem non-susceptible isolates and these were subsequently identified by MALDI-TOF MS. Resistance phenotypes and genotypes were confirmed using antimicrobial susceptibility testing and molecular biological techniques. Genomic characteristics of the carbapenemase-producing isolates were investigated using whole genome sequencing (WGS) and bioinformatic analysis. In total, 88 NDM-positive Enterobacteriaceae were identified from 2,771 samples and 96.6% were Escherichia coli. The New Delhi metallo-β-lactamase (NDM)-positive E. coli displayed a diversity of sequence types (ST), and ST48 and ST165 were the most prevalent. Three variants of blaNDM (blaNDM-1, blaNDM-4, and blaNDM-5) were detected and WGS indicated that blaNDM-5 predominated and was carried primarily on IncX3 plasmids. All these isolates were also multiply-drug resistant. These results revealed that food-producing animals in China are an important reservoir for NDM-positive E. coli and pose a potential threat to public health.

Genomic Characterization of Carbapenem-Non-susceptible Pseudomonas aeruginosa Clinical Isolates From Saudi Arabia Revealed a Global Dissemination of GES-5-Producing ST235 and VIM-2-Producing ST233 Sub-Lineages.

Carbapenem-resistant P. aeruginosa has become a major clinical problem due to limited treatment options. However, studies assessing the trends in the molecular epidemiology and mechanisms of antibiotic resistance in this pathogen are lacking in Saudi Arabia. Here, we reported the genome characterization in a global context of carbapenem non-susceptible clinical isolates from a nationally representative survey. The antibiotic resistance profiles of the isolates (n = 635) collected over 14 months between March 2018 and April 2019 from different geographical regions of Saudi Arabia showed resistance rates to relevant β-lactams, aminoglycosides and quinolones ranging between 6.93 and 27.56%. Overall, 22.52% (143/635) of the isolates exhibited resistance to both imipenem and meropenem that were mainly explained by porin loss and efflux overexpression. However, 18.18% of resistant isolates harbored genes encoding GES (69.23%), VIM (23.07%), NDM (3.85%) or OXA-48-like (3.85%) carbapenemases. Most common GES-positive isolates produced GESs −5, −15 or −1 and all belonged to ST235 whereas the VIM-positive isolates produced mainly VIM-2 and belonged to ST233 or ST257. GES and VIM producers were detected at different sampling periods and in different surveyed regions. Interestingly, a genome-wide comparison revealed that the GES-positive ST235 and VIM-2-positive ST233 genomes sequenced in this study and those available through public databases from various locations worldwide, constituted each a phylogenetically closely related sub-lineage. Profiles of virulence determinants, antimicrobial resistance genes and associated mobile elements confirmed relatedness within each of these two different sub-lineages. Sequence analysis located the blaGES gene in nearly all studied genomes (95.4%) in the same integrative conjugative element that also harbored the acc(6′)-Ib, aph(3′)-XV, aadA6, sul1, tet(G), and catB resistance genes while blaVIM–2 in most (98.89%) ST233-positive genomes was co-located with aac(6′)-I1, dfrB-5, and aac(3′)-Id in the same class I integron. The study findings revealed the global spread of GES-5 ST235 and VIM-2 ST233 sub-lineages and highlighted the importance of routine detection of rare β-lactamases.

Does cefiderocol heteroresistance explain the discrepancy between the APEKS-NP and CREDIBLE-CR clinical trial results?

Does cefiderocol heteroresistance explain the discrepancy between the APEKS-NP and CREDIBLE-CR clinical trial results?

In-Vitro Efficacy of Cefiderocol in Carbapenem-Non-Susceptible Gram-Negative Bacilli of Different Genotypes in Sub-Region of North Rhine Westphalia, Germany.

In the last two decades, the worldwide dissemination of multidrug-resistant Gram-negative bacteria (MDR-GNB) has continued. Therapy options for such infections caused by MDR-GNB remain scarce, and only few new antimicrobial agents have been granted market approval. Cefiderocol has been approved for the treatment of infections associated with aerobic GNB with limited therapy options. This study evaluated the in vitro efficacy of cefiderocol against carbapenem-non-susceptible clinical GNB isolates from Germany. A total of 115 non-duplicate carbapenem-nonsusceptible GNB isolates, 61 (53.05%) of which were Enterobacterales species and 54 (46.95%) were non-fermenters (Acinetobacter baumanii and Pseudomonas aeruginosa), were investigated for their cefiderocol susceptibility. Minimum inhibitory concentrations (MICs) for cefiderocol were determined by disk diffusion, according to EUCAST (European committee for antimicrobial susceptibility testing). Susceptibility rates were based on EUCAST breakpoints. In the absence of a species-specific breakpoint, pharmacokinetic/-dynamic breakpoints were used. The most common pathogen was A. baumannii (33.91%), followed by Klebsiella pneumoniae (31.3%), P. aeruginosa (13.04%) and Escherichia coli (9.57%). Overall, 83.6% (51/61) of the Enterobacterales and 81.48% (44/54) of the non-fermenters were susceptible towards cefiderocol. In total, 20 species of Enterobacterales and non-fermenting GNB were resistant towards cefiderocol, irrespective of the isolation year (2014 to 2021). Moreover, the majority of the resistant isolates were among the OXA-23 producing A. baumannii (n = 7/26; 26.92%) from patients hospitalized during 2018 and 2019. Cefiderocol demonstrated high in vitro susceptibility rates against a wide range of carbapenem-non-susceptible GNB, including carbapenemase-producing isolates. Cefiderocol exhibited stability against hydrolysis by all carbapenemases, including metallo-β-lactamases (MBLs), except that few OXA-producing isolates exhibited resistance towards cefiderocol.

Molecular Mechanisms and Epidemiology of Carbapenem-Resistant Enterobacter cloacae Complex Isolated from Chinese Patients During 2004-2018.

BackgroundThe emergence and spread of carbapenem-resistant Enterobacter cloacae complex (ECC) have posed a serious threat to human health worldwide. This study aimed to investigate the molecular mechanism of carbapenem resistance and its prevalence among ECC in China.MethodsA total of 1314 ECC clinical isolates were collected from the First Affiliated Hospital of Wenzhou Medical University from 2004 to 2018. Sensitivity to antibiotics was determined using the agar dilution method. The production of carbapenemases and the prevalence of resistance-associated genes were investigated using PCR. The expression of outer membrane porin (OMP) genes (ompC/ompF) and cephalosporinase gene ampC was analyzed by quantitative real-time PCR. The effect of efflux pump mechanism on carbapenem resistance was tested. ECC was typed by multilocus sequence typing (MLST).ResultsIn this study, 113 carbapenem-nonsusceptible ECC strains were identified. The prevalence rates of carbapenemase genes blaKPC-2 and blaNDM were 12.4% (14/113) and 17.7% (20/113), and that of the extended-spectrum β-lactamase (ESBL) genes blaCTX-M, blaTEM, and blaSHV were 28.3% (32/113), 27.4% (31/113), and 14.2% (16/113), respectively. Among 67 carbapenem-nonsusceptible ECC isolates producing non-carbapenemase, low expression of ompC/ompF and overexpression of ampC were found in 46 and 40 strains, respectively. In addition, the carbapenem resistance was related to the overexpression of the efflux pump in the study. Finally, the 113 carbapenem-nonsusceptible ECC strains were categorized into 39 different sequence types using MLST.ConclusionCarbapenem-nonsusceptible ECC strains producing non-carbapenemase were predominant. The low expression of OMP with the overexpression of cephalosporinase or production of ESBLs and overexpression of efflux pump might contribute to the resistance to carbapenem for carbapenem-nonsusceptible ECC strains producing non-carbapenemase. The blaNDM and blaKPC comprised the principal resistance mechanism of carbapenemase-producing ECC in the hospital, causing a threat to public health. Therefore, monitoring programs to prevent the emergence and further spread of antibiotic resistance are urgently needed.

Resistance profiling of metallo-betalactamase genes in clinical isolates of Enterobacteriaceae: Emergence of multidrug resistance

BackgroundClass B metallo-β-lactamases (MBLs) can hydrolyze commonly used β-lactam-based antibiotics. The objective of this study was to determine the frequency of carbapenem resistance genes coding for MBLs in Enterobacteriaceae isolates. MethodsEnterobacteriaceae were isolated from clinical specimens from patients referring to clinical centers of Isfahan, Iran, since July 2018 to November 2019. Antibiotic susceptibility was determined by the E-test method. Also, the minimum inhibitory concentrations (MICs) of meropenem and imipenem were calculated by the E-test method in carbapenem-resistant isolates. Then, the frequency of multi-drug resistance (MDR) Enterobacteriaceae isolates was determined. Prevalence of the MBLs genes was investigated using PCR and enterobacterial repetitive intergenic consensus (ERIC)-PCR was done to determine the clonal relatedness of the isolates. ResultsTotally, 215, 70, 28, and 18 Escherichia coli, Enterobacter spp., Citrobacter spp. and Serratia spp. were isolated from 3500 clinical specimens, respectively. The isolates were collected from wound and abscess, respiratory samples, CSF, blood, and urine.The rate of carbapenem non-susceptible isolates of E. coli, Enterobacter, Citrobacter, and Serratia were as follows, respectively: 9 (4.2%), 4 (5.7%), 1 (3.6%), and 1 (5.6%). Multi-drug resistance (MDR) frequency among E. coli, Enterobacter, Citrobacter and Serratia isolates was 59.5%, 44%, 53.5%, and 55.5%, respectively. Moreover, blaNDM-1, blaIMP-1, and blaVIM-1 genes were detected in three E. coli isolates. Nine non-susceptible E. coli and 4 non-susceptible Enterobacter isolates were categorized into two main clusters according to the results of ERIC-PCR. ConclusionAccording to the results of the present study systematic surveillance to detect MβL producing bacteria and rational prescription and use of carbapenems could be helpful to prevent the spread of carbapenem resistance.

Frequency of blaIMP and blaSPM Metallo-β-Lactamase Genes among Carbapenem-Resistant Pseudomonas aeruginosa Clinical Isolates in Sari, North of Iran.

Metallo-β-lactamases (MBLs) play a major role in the resistance of Pseudomonas aeruginosa to carbapenems. We investigated the antibiotic susceptibility patterns and frequency of MBLs genes (blaIMP and blaSPM) in carbapenem-resistant P. aeruginosa clinical isolates in Sari, Iran. The isolates were identified using standard microbiological tests, and their antibiotic susceptibility pattern was determined by the disk agar diffusion method according CLSI criteria. Phenotypic identification of MBL-producing strains assessed by the combined disk test (CDT). Then, polymerase chain reaction (PCR) was used to detect the presence of blaIMP and blaSPM genes. The highest and lowest levels of antibiotic resistance were observed against gentamicin (40%) and piperacillin-tazobactam (13%), respectively. Besides, 40 isolates (40%) had the multi-drug resistant (MDR) phenotype, while 5 (12.5%) MDR isolates were resistant to all antibiotics tested. The results of the CDT showed that among 43 carbapenem non-susceptible clinical isolates of P. aeruginosa, 33 (76.74%) isolates were MBL-producing strains. Also, the frequency of the blaIMP gene among 43 carbapenem non susceptible isolates was determined to be 6.97%, while none of these isolates carried the blaSPM gene. Due to the high prevalence of carbapenem-resistant and MDR P. aeruginosa in this study, routine antibiotic susceptibility testing and phenotypic identification of carbapenemase production by this bacterium are necessary for the proper selection of antibiotics.

Plasmid analysis of NDM metallo-β-lactamase-producing Enterobacterales isolated in Vietnam.

Carbapenem-resistant Enterobacterales (CRE) represent a serious threat to public health due to the lack of treatment and high mortality. The rate of antimicrobial resistance of Enterobacterales isolates to major antimicrobials, including carbapenems, is much higher in Vietnam than in Western countries, but the reasons remain unknown due to the lack of genomic epidemiology research. A previous study suggested that carbapenem resistance genes, such as the carbapenemase gene blaNDM, spread via plasmids among Enterobacterales in Vietnam. In this study, we characterized blaNDM-carrying plasmids in Enterobacterales isolated in Vietnam, and identified several possible cases of horizontal transfer of plasmids both within and among species of bacteria. Twenty-five carbapenem-nonsusceptible isolates from a medical institution in Hanoi were sequenced on Illumina short-read sequencers, and 13 blaNDM-positive isolates, including isolates of Klebsiella pneumoniae, Escherichia coli, Citrobacter freundii, Morganella morganii, and Proteus mirabilis, were further sequenced on an Oxford Nanopore Technologies long-read sequencer to obtain complete plasmid sequences. Almost identical 73 kb IncFII(pSE11)::IncN hybrid plasmids carrying blaNDM-1 were found in a P. mirabilis isolate and an M. morganii isolate. A 112 kb IncFII(pRSB107)::IncN hybrid plasmid carrying blaNDM-1 in an E. coli isolate had partially identical sequences with a 39 kb IncR plasmid carrying blaNDM-1 and an 88 kb IncFII(pHN7A8)::IncN hybrid plasmid in a C. freundii isolate. 148–149 kb IncFIA(Hl1)::IncA/C2 plasmids and 75–76 kb IncFII(Yp) plasmids, both carrying blaNDM-1 were shared among three sequence type 11 (ST11) isolates and three ST395 isolates of K. pneumoniae, respectively. Most of the plasmids co-carried genes conferring resistance to clinically relevant antimicrobials, including third-generation cephalosporins, aminoglycosides, and fluoroquinolones, in addition to blaNDM-1. These results provide insight into the genetic basis of CRE in Vietnam, and could help control nosocomial infections.

Evaluation of the BD Phoenix CPO detect panel for prediction of Ambler class carbapenemases

Rapid detection of carbapenemases as a cause of resistance is beneficial for infection control and antimicrobial therapy. The BD Phoenix NMIC-502 panel and CPO detect test identifies presence of carbapenemases in Enterobacterales such as Klebsiella pneumoniae and assigns them to Ambler classes. To evaluate the performance of the CPO detect panel, we employed a European collection of 1222 K. pneumoniae including carbapenem non-susceptible and susceptible clinical isolates from 26 countries, for which draft genomes were available after Illumina sequencing and the presence of carbapenemase genes had been identified by ARIBA gene calling. The CPO panel detected 488 out of 494 carbapenemase-encoding isolates as positive and six as negative. One-hundred and two isolates were tested positive for carbapenemase in the absence of any carbapenemase gene. The CPO panel identified 229 out of 230 KPC-positive isolates as carbapenemase producing and classified 62 of these as class A enzyme. Similarly, the CPO panel correctly specified 167 of 182 as class D. Regarding metallo-beta-lactamases, the CPO panel assigned 78 of 90 MBL positive isolates to class B enzymes. The sensitivity of the CPO panel in detecting carbapenemase activity was 99.5%, 97.7% and 98.3% for class A, B and D enzymes, respectively. The sensitivity in assignation to Ambler class A, B and D was 27%, 86% and 91%, respectively. An overall sensitivity of 98.8% and specificity of 86% in unclassified detection of carbapenemases was observed, with frequent false positive detection of carbapenemase producing organisms, thus rendering further confirmatory tests necessary.

The prediction values of carbapenemase detection methods and carbapenem susceptibility testing for clinical outcomes of patients with Acinetobacter bacteremia under carbapenem treatment.

Carbapenem-resistant Acinetobacter species have emerged as notorious pathogens causing nosocomial infections. Several phenotypic methods have been developed for detecting carbapenemase production in Enterobacteriaceae. The accuracy of these methods in the prediction of carbapenemase production in Acinetobacter species has not been studied well. This retrospective study enrolled adult patients with Acinetobacter bacteremia from four medical centers in Taiwan between 2012 and 2016. Their demographics and clinical outcomes were recorded. The carbapenem susceptibility of the Acinetobacter species was determined using the agar diffusion method. The carbapenemase genes were detected by PCR. Four phenotypic methods, including the modified Hodge test (MHT), modified carbapenem inactivation method (mCIM), Carba NP test, and CarbAcineto NP test were carried out to determine the production of carbapenemase. We analyzed 257 adults who received initial carbapenem monotherapy for the treatment of Acinetobacter bacteremia. Shock within three days of bacteremia and acquisition of carbapenem non-susceptible isolates were independently associated with a higher 14-day and 30-day mortality in patients with Acinetobacter bacteremia. Among the four phenotypic tests for carbapenemase detection, MHT using the imipenem disc displayed the greatest sensitivity (94%; 95% confidence interval [CI], 89-97%) and specificity (81%; 95% CI, 73-88%) for predicting imipenem non-susceptibility. Carbapenem non-susceptibility and shock were independent risk factors for mortality in patients with Acinetobacter bacteremia. The MHT could predict the carbapenem susceptibility of Acinetobacter isolates. It is a cheap and quick assay, which could be applied in clinical practice.

Detection of diverse carbapenem and multidrug resistance genes and high-risk strain types among carbapenem non-susceptible clinical isolates of target gram-negative bacteria in Kenya.

Carbapenem-resistant gram-negative bacteria are an increasingly significant clinical threat globally. This risk may be underestimated in Kenya as only four carbapenemase genes in three bacterial species have been described. The study aimed to understand the antibiotic resistance profiles, genes, sequence types, and distribution of carbapenem-resistant gram-negative bacteria from patients in six hospitals across five Kenyan counties by bacterial culture, antibiotic susceptibility testing, and whole-genome sequence analysis. Forty-eight, non-duplicate, carbapenem non-susceptible, clinical isolates were identified across the five counties (predominantly in Nairobi and Kisii): twenty-seven Acinetobacter baumannii, fourteen Pseudomonas aeruginosa, three Escherichia coli, two Enterobacter cloacae, and two Klebsiella pneumoniae. All isolates were non-susceptible to β-lactam drugs with variable susceptibility to tigecycline (66%), minocycline (52.9%), tetracycline (29.4%), and levofloxacin (22.9%). Thirteen P. aeruginosa isolates were resistant to all antibiotics tested. Eleven carbapenemase genes were identified: blaNDM-1, blaOXA-23, -58, -66, -69, and -91 in A. baumannii (STs 1, 2, 164 and a novel ST1475), blaNDM-1 in E. cloacae (STs 25,182), blaNDM-1, blaVIM-1and -6, blaOXA-50 in P. aeruginosa (STs 316, 357, 654, and1203), blaOXA-181, blaNDM-1 in K. pneumoniae (STs 147 and 219), and blaNDM-5 in E. coli (ST164). Five A. baumannii isolates had two carbapenemases, blaNDM-1, and either blaOXA-23 (4) or blaOXA-58 (1). AmpC genes were detected in A. baumannii (blaADC-25), E. cloacae (blaDHA-1 and blaACT-6, 16), and K. pneumoniae (blaCMY). Significant multiple-drug resistant genes were the pan-aminoglycoside resistance16srRNA methyltransferase armA, rmtB, rmtC, and rmtF genes. This study is the first to report blaOXA-420, -58, -181, VIM-6, and blaNDM-5 in Kenyan isolates. High-risk STs of A. baumannii (ST1475, ST2), E. cloacae ST182, K. pneumoniae ST147, P. aeruginosa (ST357, 654), and E. coli ST167, ST648 were identified which present considerable therapeutic danger. The study recommends urgent carbapenem use regulation and containment of high-risk carbapenem-resistant bacteria.