Susceptibility of gram-negative isolates collected in Taiwan to imipenem/relebactam and comparator agents - SMART 2018-2021.

BACKGROUND: Imipenem/relebactam (IMR) was approved for patient use in Taiwan in 2023. We evaluated the in vitro susceptibility of recent Gram-negative pathogens collected in Taiwan hospitals to IMR and comparators with a focus on carbapenem-resistant and KPC-carrying non-Morganellaceae Enterobacterales (NME), and carbapenem-resistant Pseudomonas aeruginosa (CRPA). METHODS: From 2018 to 2021, eight hospitals in Taiwan each collected up to 250 consecutive, aerobic or facultative, Gram-negative pathogens per year from patients with bloodstream, intraabdominal, lower respiratory tract, and urinary tract infections. MICs were determined using Clinical Laboratory Standards Institute (CLSI) broth microdilution. Most isolates that were IMR-, imipenem-, or ceftolozane/tazobactam-nonsusceptible were screened for ß-lactamase genes by PCR or whole-genome sequencing. RESULTS: Ninety-eight percent of NME (n = 5063) and 94% of P. aeruginosa (n = 1518) isolates were IMR-susceptible. Percent susceptible values for non-carbapenem ß-lactam comparators, including piperacillin/tazobactam, were 68-79% for NME isolates, while percent susceptible values for all ß-lactam comparators, including meropenem, were 73-81% for P. aeruginosa. IMR retained activity against 93% of multidrug-resistant (MDR) NME and 70% of MDR P. aeruginosa. Sixty-five percent of carbapenem-resistant NME and 81% of KPC-positive NME (n = 80) were IMR-susceptible. IMR inhibited 70% of CRPA (n = 287). Fifty percent of IMR-nonsusceptible NME tested for ß-lactamase carriage had an MBL or OXA-48-like enzyme, whereas most (95%) IMR-nonsusceptible P. aeruginosa examined did not carry acquired ß-lactamase genes. CONCLUSION: Based on our in vitro data, IMR may be a useful option for the treatment of hospitalized patients in Taiwan with infections caused by common Gram-negative pathogens, including carbapenem-resistant NME, KPC-positive NME, and CRPA.

In Vitro Activity of Cefepime-Taniborbactam and Comparators against Clinical Isolates of Gram-Negative Bacilli from 2018 to 2020: Results from the Global Evaluation of Antimicrobial Resistance via Surveillance (GEARS) Program.

Taniborbactam is a novel cyclic boronate ß-lactamase inhibitor in clinical development in combination with cefepime. We assessed the in vitro activity of cefepime-taniborbactam and comparators against a 2018-2020 collection of Enterobacterales (n = 13,731) and Pseudomonas aeruginosa (n = 4,619) isolates cultured from infected patients attending hospitals in 56 countries. MICs were determined by CLSI broth microdilution. Taniborbactam was tested at a fixed concentration of 4 µg/mL. Isolates with cefepime-taniborbactam MICs of ≥16 µg/mL underwent whole-genome sequencing. ß-lactamase genes were identified in meropenem-resistant isolates by PCR/Sanger sequencing. Against Enterobacterales, taniborbactam reduced the cefepime MIC90 value by >64-fold (from >16 to 0.25 µg/mL). At ≤16 µg/mL, cefepime-taniborbactam inhibited 99.7% of all Enterobacterales isolates; >97% of isolates with multidrug-resistant (MDR) and ceftolozane-tazobactam-resistant phenotypes; ≥90% of isolates with meropenem-resistant, difficult-to-treat-resistant (DTR), meropenem-vaborbactam-resistant, and ceftazidime-avibactam-resistant phenotypes; 100% of VIM-positive, AmpC-positive, and KPC-positive isolates; 98.7% of extended-spectrum ß-lactamase (ESBL)-positive; 98.8% of OXA-48-like-positive; and 84.6% of NDM-positive isolates. Against P. aeruginosa, taniborbactam reduced the cefepime MIC90 value by 4-fold (from 32 to 8 µg/mL). At ≤16 µg/mL, cefepime-taniborbactam inhibited 97.4% of all P. aeruginosa isolates; ≥85% of isolates with meropenem-resistant, MDR, and meropenem-vaborbactam-resistant phenotypes; >75% of isolates with DTR, ceftazidime-avibactam-resistant, and ceftolozane-tazobactam-resistant phenotypes; and 87.4% of VIM-positive isolates. Multiple potential mechanisms, including carriage of IMP, certain alterations in PBP3, permeability (porin) defects, and possibly, upregulation of efflux were present in most isolates with cefepime-taniborbactam MICs of ≥16 µg/mL. We conclude that cefepime-taniborbactam exhibited potent in vitro activity against Enterobacterales and P. aeruginosa and inhibited most carbapenem-resistant isolates, including those carrying serine carbapenemases or NDM/VIM metallo-ß-lactamases (MBLs).

In vitro activity of cefiderocol against MBL-producing Gram-negative bacteria collected in North America and Europe in five consecutive annual multinational SIDERO-WT surveillance studies (2014-2019).

OBJECTIVES: To evaluate the in vitro antibacterial activity of cefiderocol, a siderophore cephalosporin against MBL-producing clinical isolates. METHODS: MBL-producing strains were selected from clinical isolates of Enterobacterales, Pseudomonas aeruginosa and Acinetobacter baumannii complex collected in North America and Europe in five consecutive annual multinational SIDERO-WT surveillance studies from 2014 to 2019. MICs of cefiderocol and comparator agents were determined by the broth microdilution method according to the CLSI guideline. RESULTS: A total of 452 MBL-producing strains consisting of 200 Enterobacterales, 227 P. aeruginosa and 25 A. baumannii complex were identified. The highest number of MBL-producing Enterobacterales strains were detected in Greece. MBL-producing strains of both P. aeruginosa and A. baumannii complex were isolated most frequently in Russia. For Enterobacterales, 91.5% or 67.5% of MBL-producing strains had cefiderocol MIC values ≤4 mg/L (CLSI susceptibility breakpoint) or ≤2 mg/L (EUCAST susceptibility breakpoint), respectively. All MIC values of cefiderocol for MBL-producing P. aeruginosa strains were ≤4 mg/L (CLSI susceptibility breakpoint), and 97.4% of them had cefiderocol MIC values ≤2 mg/L (EUCAST susceptibility breakpoint). For A. baumannii complex, 60.0% or 44.0% of MBL-producing strains had cefiderocol MIC values ≤4 mg/L (CLSI susceptibility breakpoint) or ≤2 mg/L (EUCAST pharmacokinetic-pharmacodynamic susceptibility breakpoint), respectively. Against all types of MBL-producing strains, MIC distribution curves of cefiderocol were located in the lowest numerical values, compared with other ß-lactams and ß-lactam/ß-lactamase inhibitor combinations tested and ciprofloxacin. CONCLUSIONS: Although the types of MBL-producing strains isolated by country varied, cefiderocol showed potent in vitro activity against all types of MBL-producing Gram-negative bacteria regardless of the bacterial species.

Incidence of ESBLs and carbapenemases among Enterobacterales and carbapenemases in Pseudomonas aeruginosa isolates collected globally: results from ATLAS 2017-2019.

OBJECTIVES: To assess the global and regional distribution of ESBLs in Enterobacterales and carbapenemases in Enterobacterales and Pseudomonas aeruginosa. METHODS: Antimicrobial susceptibility of isolates collected from ATLAS (2017-2019) was determined per CLSI guidelines. Enterobacterales exhibiting meropenem MICs ≥2 mg/L and/or ceftazidime/avibactam and/or aztreonam/avibactam MICs ≥16 mg/L, Escherichia coli and Klebsiella pneumoniae with aztreonam and/or ceftazidime MICs ≥2 mg/L, and P. aeruginosa with meropenem MICs ≥4 mg/L were screened for ß-lactamases by PCR and sequencing. RESULTS: Globally, ESBL-positive E. coli (23.7%, 4750/20047) and K. pneumoniae (35.1%, 6055/17229) carried predominantly the CTX-M-15 variant (E. coli: 53.9%; K. pneumoniae: 80.0%) with highest incidence in Africa/Middle East (AfME). Among carbapenem-resistant (CR) E. coli (1.1%, 217/20047) and Enterobacter cloacae (3.8%, 259/6866), NDMs were predominant (E. coli in AfME: 62.5%; E. cloacae in Asia Pacific: 59.7%). CR K. pneumoniae (13.3%, 2299/17 229) and P. aeruginosa (20.3%, 4187/20 643) carried predominantly KPC (30.9%) and VIM (14.7%), respectively, with highest frequency in Latin America. Among ESBL-positive Enterobacterales, susceptibility to ceftazidime/avibactam (>90.0%) and amikacin (>85.0%) was higher than to piperacillin/tazobactam (>45.0%) and ciprofloxacin (>7.4%). In CR Enterobacterales, susceptibility to amikacin (>54.0%) and ceftazidime/avibactam (>31.0%) was higher than to ciprofloxacin (>2.7%) and piperacillin/tazobactam (>0.5%). CR P. aeruginosa similarly demonstrated higher susceptibility to amikacin (63.4%) and ceftazidime/avibactam (61.9%) than to ciprofloxacin (26.2%) and piperacillin/tazobactam (25.3%). CONCLUSIONS: Varied distribution of resistance genotypes across regions among ESBL-positive Enterobacterales and CR Enterobacterales and P. aeruginosa provide crucial insights on major resistance mechanisms and trends observed in recent years. Continued surveillance is warranted for monitoring global dissemination and resistance.

In vitro activity of aztreonam-avibactam against Enterobacterales isolates collected in Latin America, Africa/Middle East, Asia, and Eurasia for the ATLAS Global Surveillance Program in 2019-2021.

This study aimed to report reference method antimicrobial susceptibility results for 24,937 recent (2019-2021) clinical isolates of Enterobacterales from 27 countries in Latin America, Eurasia, Africa/Middle East, and Asia with a focus on the investigational combination aztreonam-avibactam against metallo-ß-lactamase (MBL) isolates. Antimicrobial susceptibility testing was performed by the CLSI broth microdilution methodology. Minimum inhibitory concentrations (MICs) were interpreted using the CLSI (2022) breakpoints for all agents except aztreonam-avibactam (provisional pharmacokinetic/pharmacodynamic susceptible breakpoint, ≤ 8 mg/L) and tigecycline (US-FDA). Molecular testing for ß-lactamase genes was performed on isolates with meropenem MICs ≥ 2 mg/L, ceftazidime-avibactam MICs ≥ 16 mg/L, and/or aztreonam-avibactam MICs ≥ 16 mg/L, and 50% of isolates of Escherichia coli, Klebsiella pneumoniae, Klebsiella oxytoca, Klebsiella variicola, and Proteus mirabilis testing with ceftazidime and/or aztreonam MICs ≥ 2 mg/L. Aztreonam-avibactam inhibited 99.8% of all Enterobacterales at ≤ 8 mg/L (MIC90, 0.25 mg/L) and maintained activity against phenotypically resistant subsets of multidrug-resistant (MDR) (99.5% susceptible), extensively drug-resistant (XDR) (98.7%), and carbapenem-resistant Enterobacterales (CRE) (99.1%) isolates. At ≤ 8 mg/L, aztreonam-avibactam inhibited 100%, 99.6%, 99.6%, and 98.8% of KPC-, OXA-48-like-, ESBL-, and MBL-carrying isolates, respectively. MBL-positive isolates were most prevalent in India (20.5%), Guatemala (13.8%), and Jordan (13.2%). No differences in the activity of aztreonam-avibactam were observed across the global regions evaluated. At a concentration of ≤ 8 mg/L, aztreonam-avibactam inhibited almost all Enterobacterales collected from developing countries, including MBL-producing isolates. The widespread dissemination of MBLs among Enterobacterales highlights the unmet need for new agents such as aztreonam-avibactam for the treatment of CRE infections.

Ceftibuten-Ledaborbactam Activity against Multidrug-Resistant and Extended-Spectrum-ß-Lactamase-Positive Clinical Isolates of Enterobacterales from a 2018-2020 Global Surveillance Collection.

Ceftibuten-ledaborbactam etzadroxil is a cephalosporin-boronate ß-lactamase inhibitor prodrug combination under development as an oral treatment for complicated urinary tract infections caused by multidrug-resistant (MDR) Enterobacterales producing serine ß-lactamases (Ambler class A, C, and D). In vivo, ledaborbactam etzadroxil (formerly VNRX-7145) is cleaved to the active inhibitor ledaborbactam (formerly VNRX-5236). To more completely define the breadth of ceftibuten-ledaborbactam's activity against important antimicrobial-resistant pathogens, we assessed its in vitro activity against phenotypic and genotypic subsets from a 2018-2020 global culture collection of 3,889 clinical isolates of Enterobacterales, including MDR organisms, extended-spectrum-ß-lactamase (ESBL)-positive organisms, and organisms that are nonsusceptible and resistant to other antimicrobials. MICs were determined by CLSI broth microdilution and interpreted using both CLSI and EUCAST breakpoints. Ledaborbactam was tested at a fixed concentration of 4 µg/mL. ß-Lactamase genes were characterized by PCR followed by Sanger sequencing or whole-genome sequencing for selected ß-lactam-resistant isolate subsets. At ≤1 µg/mL, ceftibuten-ledaborbactam (MIC90, 0.25 µg/mL) inhibited 89.7% of MDR isolates, 98.3% of isolates with a presumptive ESBL-positive phenotype, and 92.6% of trimethoprim-sulfamethoxazole-nonsusceptible, 91.7% of levofloxacin-nonsusceptible, 88.1% of amoxicillin-clavulanate-nonsusceptible, 85.7% of ceftibuten-resistant (MIC >1 µg/mL), and 54.1% of carbapenem-nonsusceptible isolates. Against specific ESBL genotype-positive isolates (AmpC negative, serine carbapenemase negative, and metallo-ß-lactamase negative), ceftibuten-ledaborbactam inhibited 96.3% of CTX-M-9 group (MIC90, 0.25 µg/mL), 91.5% of CTX-M-1 group (MIC90, 0.5 µg/mL), and 88.2% of SHV-positive (MIC90, 2 µg/mL) isolates at ≤1 µg/mL. Against specific serine carbapenemase genotype-positive isolates, ceftibuten-ledaborbactam inhibited 85.9% of KPC-positive (MIC90, 2 µg/mL) and 82.9% of OXA-48-group-positive (MIC90, 2 µg/mL) isolates at ≤1 µg/mL. Continued development of ceftibuten-ledaborbactam appears warranted.

Multicenter Evaluation of the Acuitas AMR Gene Panel for Detection of an Extended Panel of Antimicrobial Resistance Genes among Bacterial Isolates.

The Acuitas antimicrobial resistance (AMR) gene panel is a qualitative, multiplex, nucleic acid-based in vitro diagnostic test for the detection and differentiation of 28 antimicrobial resistance markers associated with not susceptible results (NS; i.e., intermediate or resistant) to one or more antimicrobial agents among cultured isolates of select Enterobacterales, Pseudomonas aeruginosa, and Enterococcus faecalis. This study was conducted at four sites and included testing of 1,224 deidentified stocks created from 584 retrospectively collected isolates and 83 prospectively collected clinical isolates. The Acuitas results were compared with a combined reference standard including whole-genome sequencing, organism identification, and phenotypic antimicrobial susceptibility testing. The positive percent agreement (PPA) for FDA-cleared AMR targets ranged from 94.4% for MCR-1 to 100% for armA, CTX-M-2, DHA, IMP, OXA-9, SHV, vanA, and VEB. The negative percent agreement (NPA) for the majority of targets was ≥99%, except for AAC, AAD, CMY-41, P. aeruginosa gyrA mutant, Sul1, Sul2, and TEM targets (range, 96.5% to 98.5%). Three AMR markers did not meet FDA inclusion criteria (GES, SPM, and MCR-2). For each organism, 1 to 22 AMR targets met the minimum reportable PPA/NPA and correlated with ≥80% positive predictive value with associated NS results for at least one agent (i.e., the probability of an organism carrying an AMR marker testing NS to the associated agent). We demonstrate that the Acuitas AMR gene panel is an accurate method to detect a broad array of AMR markers among cultured isolates. The AMR markers were further associated with expected NS results for specific agent-organism combinations.

Multicenter evaluation of the RAPIDEC® CARBA NP assay for the detection of carbapenemase production in clinical isolates of Enterobacterales and Pseudomonas aeruginosa.

Carbapenem-resistant Gram-negative bacilli are a major public health problem. Accurate and rapid detection of carbapenemase-producing organisms can facilitate appropriate infection prevention measures. The objective was to evaluate the performance of the RAPIDEC® CARBA NP assay (RAPIDEC), a screening assay that utilizes a pH indicator to detect carbapenem hydrolysis within 2 h. A multicenter study evaluated 306 clinical bacterial strains of Enterobacterales (n = 257) and Pseudomonas aeruginosa (n = 49). The RAPIDEC was compared to a composite reference standard-the Clinical Laboratory Standards Institute (CLSI) Carba NP assay, PCR for specific carbapenemase genes (blaKPC, blaNDM, blaOXA-48-like, blaVIM and blaIMP), and phenotypic carbapenem susceptibility testing. The assay was evaluated using two culture incubation times for the bacterial isolates: "routine"(cultures incubated 18-24 h) and "short" (cultures incubated 4-5 h). For the routine incubation, the overall percent agreement was 98.7% with a positive percent agreement (PPA) of 99.6% and a negative percent agreement (NPA) of 97.4%; there were five false positives and one false negative. For the short incubation, the overall percent agreement was 98.0% with a PPA of 98.5% and a NPA of 97.3%; there were five false positives and four false negatives. RAPIDEC results for the P. aeruginosa isolates were 100% concordant with the reference standard for both incubation times. The RAPIDEC assay is an accurate and rapid (≤ 2 h) assay for the detection of the most common carbapenemases in clinical isolates. Growth from a short incubation culture may be used to reliably detect carbapenemase production in clinical strains.

Correlation of ß-Lactamase Production and Colistin Resistance among Enterobacteriaceae Isolates from a Global Surveillance Program.

The increasing use of carbapenems for treating multidrug-resistant (MDR) Gram-negative bacterial infections has contributed to the global dissemination of carbapenem-resistant Enterobacteriaceae (CRE). Serine and metallo-ß-lactamases (MBLs) that hydrolyze carbapenems have become prevalent and endemic in some countries, necessitating the use of older classes of agents, such as colistin. A total of 19,719 isolates of Enterobacteriaceae (excluding Proteeae and Serratia spp., which have innate resistance to colistin) were collected from infected patients during 2012 and 2013 in a global surveillance program and tested for antimicrobial susceptibility using CLSI methods. Isolates of CRE were characterized for carbapenemases and extended-spectrum ß-lactamases (ESBLs) by PCR and sequencing. Using EUCAST breakpoints, the rate of colistin susceptibility was 98.4% overall, but it was reduced to 88.0% among 482 carbapenemase-positive isolates. Colistin susceptibility was higher among MBL-positive isolates (92.6%) than those positive for a KPC (87.9%) or OXA-48 (84.2%). Of the agents tested, only tigecycline (MIC90, 2 to 4 µg/ml) and aztreonam-avibactam (MIC90, 0.5 to 1 µg/ml) consistently tested with low MIC values against colistin-resistant, ESBL-positive, and carbapenemase-positive isolates. Among the 309 (1.6%) colistin-resistant isolates from 10 species collected in 38 countries, 58 carried a carbapenemase that included KPCs (38 isolates), MBLs (6 isolates), and OXA-48 (12 isolates). These isolates were distributed globally (16 countries), and 95% were Klebsiella pneumoniae. Thirty-nine (67.2%) isolates carried additional ESBL variants of CTX-M, SHV, and VEB. This sample of Enterobacteriaceae demonstrated a low prevalence of colistin resistance overall. However, the wide geographic dispersion of colistin resistance within diverse genus and species groups and the higher incidence observed among carbapenemase-producing MDR pathogens are concerning.

Susceptibility of Gram-negative isolates collected in South Korea to imipenem/relebactam and comparator agents-SMART 2018-21.

Objectives: To evaluate the in vitro susceptibility of recent Gram-negative pathogens collected in South Korean medical centres to imipenem/relebactam and comparator agents. Methods: From 2018 to 2021, six hospitals in South Korea each collected up to 250 consecutive, aerobic or facultative Gram-negative pathogens per year from patients with bloodstream, intra-abdominal, lower respiratory tract and urinary tract infections. MICs were determined using CLSI broth microdilution and interpreted by 2023 CLSI breakpoints. Most isolates that were imipenem/relebactam, imipenem or ceftolozane/tazobactam non-susceptible were screened for ß-lactamase genes by PCR or WGS. Results: Of all non-Morganellaceae Enterobacterales (NME) isolates (n = 4100), 98.8% were imipenem/relebactam susceptible. Most NME were also susceptible to imipenem alone (94.7%) and meropenem (97.3%); percent susceptible values for non-carbapenem ß-lactam comparators were lower (68%-80%). Imipenem/relebactam retained activity against 96.4%, 70.8% and 70.6% of MDR, difficult-to-treat resistant (DTR) and meropenem-non-susceptible NME, respectively, and inhibited 93.1% of KPC-carrying and 95.5% of ESBL-carrying NME. Of imipenem/relebactam-resistant NME, 21/25 (84.0%) carried an MBL or an OXA-48-like carbapenemase. Of all Pseudomonas aeruginosa isolates (n = 738), 82.8% were imipenem/relebactam susceptible; percent susceptible values for all ß-lactam comparators, including carbapenems (imipenem, meropenem) were 61.5%-74.7%. Less than 20% of MDR and DTR isolates, and 41% of meropenem-non-susceptible P. aeruginosa isolates were imipenem/relebactam susceptible. Of imipenem/relebactam-resistant P. aeruginosa isolates, 61.6% carried an MBL and 37.0% did not possess any acquired ß-lactamase genes. Conclusions: Based on in vitro data, imipenem/relebactam, if licensed in South Korea, may be a viable treatment option for many hospitalized patients infected with common Gram-negative pathogens including NME exhibiting MDR, DTR and carbapenem resistance and many ß-lactam-resistant phenotypes of P. aeruginosa.

Global trends in carbapenem- and difficult-to-treat-resistance among World Health Organization priority bacterial pathogens: ATLAS surveillance program 2018-2022.

OBJECTIVES: To report trends in carbapenem resistance and difficult-to-treat resistance (DTR) among clinical isolates of Gram-negative priority pathogens collected by the ATLAS global surveillance program from 2018 to 2022. METHODS: Reference broth microdilution testing was performed in a central laboratory for 79,214 Enterobacterales, 30,504 Pseudomonas aeruginosa, and 13,500 Acinetobacter baumannii-calcoaceticus complex isolates collected by a constant set of 157 medical centres in 49 countries in Asia Pacific (APAC), Europe (EUR), Latin America (LATAM), Middle East-Africa (MEA), and North America (NA) regions. MICs were interpreted by 2023 CLSI M100 breakpoints. ß-lactamase genes were identified for meropenem-nonsusceptible (MIC ≥2 mg/L) Enterobacterales isolates. RESULTS: Carbapenem-resistant Enterobacterales (CRE) detection increased (P < 0.05) in APAC, EUR, LATAM, and MEA regions and decreased in NA, while annual DTR percentages increased in all five regions. Carbapenem-resistant P. aeruginosa (CRPA; decreased in MEA region) and carbapenem-resistant A. baumannii-calcoaceticus complex (CRAB; decreased in MEA region and increased in EUR) remained relatively stable over time in all regions, although notably, annual percentages of CRAB and DTR A. baumannii-calcoaceticus complex isolates were consistently >25 percentage points lower in NA than in other regions. For all regions except NA, the majority of changes in CRE percentages could be attributed to hospital-acquired infections. Among meropenem-nonsusceptible Enterobacterales, KPC was the most frequent carbapenemase in NA and EUR each year. NDM was the most prevalent carbapenemase detected in 2022 in other global regions. CONCLUSION: CRE, CRPA, CRAB, and DTR rates vary among global regions over time highlighting the need for continuing surveillance to inform treatment strategies and antimicrobial stewardship.

Epidemiology and in vitro activity of ceftazidime-avibactam and comparator agents against multidrug-resistant isolates of Enterobacterales and Pseudomonas aeruginosa collected in Latin America as part of the ATLAS surveillance program in 2015‒2020.

INTRODUCTION: The incidence of antimicrobial resistance is increasing in many parts of the world. The focus of this report is to examine changes in antimicrobial resistance epidemiology among clinical isolates of Enterobacterales and Pseudomonas aeruginosa collected in six Latin American countries as part of the Antimicrobial Testing Leadership and Surveillance (ATLAS) program from 2015 to 2020, with a focus on the in vitro activity of ceftazidime-avibactam against Multidrug-Resistant (MDR) isolates. METHODS: Non-duplicate, clinical isolates of Enterobacterales (n = 15,215) and P. aeruginosa (n = 4,614) collected by 40 laboratories in Argentina, Brazil, Chile, Colombia, Mexico, and Venezuela, from 2015 to 2020, underwent centralized Clinical Lab Standards Institute (CLSI) broth microdilution susceptibility testing. Minimum Inhibitory Concentration (MIC) values were interpreted using 2022 CLSI breakpoints. An MDR phenotype was defined by resistance to ≥ 3 of seven sentinel agents. RESULTS: In total, 23.3% of Enterobacterales and 25.1% of P. aeruginosa isolates were MDR. Annual percent MDR values for Enterobacterales were stable from 2015 to 2018 (21.3% to 23.7% year) but markedly increased in 2019 (31.5%) and 2020 (32.4%). Annual percent MDR values for P. aeruginosa were stable from 2015 to 2020 (23.0% to 27.6% year). Isolates were divided into two 3-year time-periods, 2015‒2017 and 2018‒2020, for additional analyses. For Enterobacterales, 99.3% of all isolates and 97.1% of MDR isolates from 2015‒2017 were ceftazidime-avibactam-susceptible compared to 97.2% and 89.3% of isolates, respectively, from 2018‒2020. For P. aeruginosa, 86.6% of all isolates and 53.9% of MDR isolates from 2015‒2017 were ceftazidime-avibactam-susceptible compared to 85.3% and 45.3% of isolates, respectively, from 2018‒2020. Among individual countries, Enterobacterales and P. aeruginosa collected in Venezuela showed the greatest reductions in ceftazidime-avibactam susceptibility over time. CONCLUSION: MDR Enterobacterales increased in Latin America from 22% in 2015 to 32% in 2020 while MDR P. aeruginosa remained constant at 25%. Ceftazidime-avibactam remains highly active against all clinical isolates of both Enterobacterales (97.2% susceptible, 2018‒2020) and P. aeruginosa (85.3%), and inhibited more MDR isolates (Enterobacterales, 89.3% susceptible, 2018‒2020; P. aeruginosa, 45.3%) than carbapenems, fluoroquinolones, and aminoglycosides.

In Vitro Activity of Cefiderocol Against Meropenem-Nonsusceptible Gram-Negative Bacilli with Defined ß-Lactamase Carriage: SIDERO-WT Surveillance Studies, 2014-2019.

We examined the in vitro susceptibility of meropenem-nonsusceptible Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii complex isolates from five consecutive annual SIDERO-WT surveillance studies (2014-2019) to cefiderocol and comparator agents in the context of their carbapenemase carriage. 1,003 Enterobacterales, 1,758 P. aeruginosa, and 2,809 A. baumannii complex isolates from North America and Europe that were meropenem nonsusceptible (CLSI M100, 2022) were molecularly characterized for ß-lactamase content by PCR followed by Sanger sequencing or by whole genome sequencing. Among Enterobacterales, 91.5% of metallo-ß-lactamase (MBL)-producing, 98.4% of KPC-producing, 97.3% of OXA-48 group-producing, and 98.7% of carbapenemase-negative, meropenem-nonsusceptible isolates were cefiderocol susceptible (MIC ≤4 mg/L). Among P. aeruginosa, 100% of MBL-producing, 100% of GES carbapenemase-producing, and 99.8% of carbapenemase-negative, meropenem-nonsusceptible isolates were cefiderocol susceptible (MIC ≤4 mg/L). Among A. baumannii complex, 60.0% of MBL-producing, 95.6% of OXA-23 group-producing, 89.5% of OXA-24 group-producing, 100% of OXA-58 group-producing, and 95.5% of carbapenemase-negative, meropenem-nonsusceptible isolates were cefiderocol susceptible (MIC ≤4 mg/L). Cefiderocol was inactive against A. baumannii complex isolates carrying a PER or VEB ß-lactamase (n = 103; 15.5% susceptible). Ceftazidime-avibactam and ceftolozane-tazobactam were inactive against MBL-carrying and A. baumannii complex isolates; ceftolozane-tazobactam was also inactive against serine carbapenemase-carrying Enterobacterales and P. aeruginosa. In summary, cefiderocol was highly active in vitro against Gram-negative isolates carrying MBLs and serine carbapenemases, as well as carbapenemase-negative, meropenem-nonsusceptible isolates.

In vitro activity of ceftazidime-avibactam against clinical isolates of Enterobacterales and Pseudomonas aeruginosa from sub-Saharan Africa: ATLAS Global Surveillance Program 2017-2021.

OBJECTIVES: To report the in vitro susceptibility of Enterobacterales (n = 3905) and Pseudomonas aeruginosa (n = 1,109) isolates, collected from patients in sub-Saharan Africa (four countries) in 2017-2021, to a panel of 10 antimicrobial agents with a focus on ceftazidime-avibactam activity against resistant phenotypes and ß-lactamase carriers. METHODS: MICs were determined by CLSI broth microdilution and interpreted using both 2022 CLSI and EUCAST breakpoints. ß-lactamase genes were identified in select ß-lactam-nonsusceptible isolate subsets using multiplex PCR assays. RESULTS: Among Enterobacterales, 96.2% of all isolates were ceftazidime-avibactam-susceptible (MIC90, 0.5 µg/mL), including all serine carbapenemase-positive (n = 127), 99.6% of ESBL-positive, carbapenemase-negative (n = 730), 91.9% of multidrug resistant (MDR; n = 1817), and 42.7% of DTR (difficult-to-treat resistance; n = 171) isolates. Metallo-ß-lactamase (MBL) genes were identified in most (n = 136; 91.2%) ceftazidime-avibactam-resistant isolates (3.5% of all Enterobacterales isolates). Ceftazidime-avibactam percent susceptible values ranged from 99.5% (Klebsiella species other than Klebsiella pneumoniae) to 92.5% (K. pneumoniae) for the various Enterobacterial taxa examined. Greater than 90% of Enterobacterales isolates from each country (Cameroon, Ivory Coast, Nigeria, South Africa) were ceftazidime-avibactam-susceptible. Among P. aeruginosa, 88.9% of all isolates were ceftazidime-avibactam-susceptible (MIC90, 16 µg/mL). Most (88.5%) MBL-negative, meropenem-resistant (n = 78), 68.1% of MDR (n = 385), and 19.2% of DTR isolates (n = 99) were ceftazidime-avibactam-susceptible. MBL genes were identified in 43.1% of ceftazidime-avibactam-resistant isolates (n = 53; 4.8% of all P. aeruginosa isolates). Country-specific ceftazidime-avibactam percent susceptible values for P. aeruginosa ranged from 94.1% (Cameroon) to 76.2% (Nigeria). CONCLUSION: Reference in vitro antimicrobial susceptibility testing demonstrated that most recent Enterobacterales (96%) and P. aeruginosa (89%) clinical isolates from four sub-Saharan African countries were ceftazidime-avibactam susceptible.

Temporal and geographical prevalence of carbapenem-resistant Pseudomonas aeruginosa and the in vitro activity of ceftolozane/tazobactam and comparators in Taiwan-SMART 2012-2021.

OBJECTIVES: To determine the in vitro activities of ceftolozane/tazobactam (C/T) and comparators against Pseudomonas aeruginosa isolates cultured from hospitalised patient samples in Taiwan from 2012 to 2021 with an additional focus on the temporal and geographical prevalence of carbapenem-resistant P. aeruginosa (CRPA). METHODS: P. aeruginosa isolates (n = 3013) were collected annually by clinical laboratories in northern (two medical centres), central (three medical centres), and southern Taiwan (four medical centres) as part of the SMART global surveillance program. MICs were determined by CLSI broth microdilution and interpreted using 2022 CLSI breakpoints. Molecular ß-lactamase gene identification was performed on selected non-susceptible isolate subsets in 2015 and later. RESULTS: Overall, 520 (17.3%) CRPA isolates were identified. The prevalence of CRPA increased from 11.5%-12.3% (2012-2015) to 19.4%-22.8% (2018-2021) (P ≤ 0.0001). Medical centres in northern Taiwan reported the highest percentages of CRPA. C/T, first tested in the SMART program in 2016, was highly active against all P. aeruginosa (97% susceptible), with annual susceptibility rates ranging from 94% (2017) to 99% (2020). Against CRPA, C/T inhibited >90% of isolates each year, with the exception of 2017 (79.4% susceptible). Most CRPA isolates (83%) were molecularly characterised, and only 2.1% (9/433) carried a carbapenemase (most commonly, VIM); all nine carbapenemase-positive isolates were from northern and central Taiwan. CONCLUSION: The prevalence of CRPA increased significantly in Taiwan from 2012 to 2021 and warrants continued monitoring. In 2021, 97% of all P. aeruginosa and 92% of CRPA in Taiwan were C/T susceptible. Routine in vitro susceptibility testing of clinical isolates of P. aeruginosa against C/T, and other newer ß-lactam/ß-lactamase inhibitor combinations, appears prudent.

Predicting Salmonella enterica serotypes by repetitive sequence-based PCR.

Repetitive extragenic palindromic sequence-based PCR (rep-PCR) utilizing a semi-automated system, was evaluated as a method to determine Salmonella serotypes. A group of 216 Salmonella isolates belonging to 13 frequently isolated serotypes and one rarer serotype from poultry were used to create a DNA fingerprint library with the DiversiLab System software. Subsequently, a blinded set of 44 poultry isolates were fingerprinted and queried against the library in an attempt to putatively assign a serotype designation to each Salmonella isolate. The query isolates were previously typed employing standard serological techniques. Utilizing pair-wise similarity percentages as calculated by the Pearson correlation coefficient, the predicted serotype of 28 isolates matched the serological typing result. For eight isolates, rep-PCR results were interpreted as one of two very closely-related serotypes, Hadar and the rarer Istanbul. Traditional serological assays have difficulty distinguishing between these groups, and sequencing interspacer regions of the rrfH gene was unable to differentiate among isolates of these two serovars. Six of the remaining isolates resulted in no match to the database (similarity values <95%) and these indeed proved to be serotypes not included in the original library. The two remaining samples proved discrepant at the 95% similarity threshold, however examination of electropherograms clearly indicated fingerprint variability between query and library samples, suggesting an expanded rep-PCR library will be necessary for increased utility. Since serological assays can take several days to weeks to provide information, the DiversiLab System holds promise for more rapid serotype classification for members of this group.

In vitro activity of cefiderocol, a siderophore cephalosporin, against a recent collection of clinically relevant carbapenem-non-susceptible Gram-negative bacilli, including serine carbapenemase- and metallo-ß-lactamase-producing isolates (SIDERO-WT-2014 Study).

Cefiderocol is a siderophore cephalosporin in development for treatment of infections caused by Gram-negative bacilli, including carbapenem-resistant and multidrug-resistant isolates. ß-Lactamase carriage and in vitro activity of cefiderocol were determined against 1272 meropenem-non-susceptible isolates of Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii collected as part of the SIDERO-WT-2014 surveillance study. Minimum inhibitory concentration (MIC) values for cefiderocol were ≤4 µg/mL against 97.7% of tested isolates, including 100% of IMP-positive (range, 1-2 µg/mL), OXA-58-positive (MIC90, 1 µg/mL), KPC-positive (MIC90, 2 µg/mL), VIM-positive (MIC90, 2 µg/mL), and OXA-48-like-positive (MIC90, 4 µg/mL) isolates; 99.3% of carbapenemase-negative isolates (MIC90, 1 µg/mL); 97.2% of OXA-23-positive isolates (MIC90, 1 µg/mL); 95.2% of OXA-24-positive isolates (MIC90, 1 µg/mL); 91.7% of GES-positive isolates (MIC90, 4 µg/mL); and 64.3% of NDM-positive isolates (MIC90, 8 µg/mL). A total of 29 isolates (2.3%; 15 OXA-23-producers, 6 OXA-24-producers, 5 NDM-producers, and 3 carbapenemase-negative isolates) exhibited cefiderocol MIC ≥8 µg/mL, confirming there was no clear correlation between carriage of ß-lactamases included in the molecular testing algorithm and elevated cefiderocol MICs. Similarly, no correlation was observed between cefiderocol MICs and truncation or loss of porin proteins in meropenem-non-susceptible isolates of E. coli and K. pneumoniae. Cefiderocol MICs were also ≤4 µg/mL against 99.3% of 136 colistin-resistant Enterobacteriaceae collected as part of the SIDERO-WT-2014 study, including isolates carrying mcr-1 (MIC90, 2 µg/mL). Cefiderocol demonstrated potent in vitro activity against a collection of carbapenemase-producing and carbapenemase-negative meropenem-non-susceptible Gram-negative bacilli for which few treatment options are available, including the majority of metallo-ß-lactamase producing isolates identified.

Characterization of "Mycobacterium paraffinicum" associated with a pseudo-outbreak.

We describe the first "Mycobacterium paraffinicum" (unofficial taxon) pseudo-outbreak in a tertiary-care medical center. Fifteen clinical nontuberculous mycobacterium isolates from 10 patients were initially identified by biochemical tests and high-performance liquid chromatography as Mycobacterium scrofulaceum. However, further testing by molecular analysis revealed "M. paraffinicum." Epidemiological and environmental investigation determined that the ice machine was the source of the pseudo-outbreak.

Global survey of Klebsiella pneumoniae major porins from ertapenem non-susceptible isolates lacking carbapenemases.

PURPOSE: To understand the diversity of porin disruption in Klebsiella pneumoniae, the major outer membrane protein (OMP) porins, OmpK35 and OmpK36, were examined in a set of isolates that did not harbour traditional carbapenem-hydrolysing enzymes, but nevertheless tested non-susceptible to ertapenem. METHODS: A world-wide collection of Klebsiella pneumoniae isolates that were part of the Study for Monitoring Antimicrobial Resistance Trends (SMART) surveillance project over the years 2008-2014 were characterised with regard to their ß-lactamase gene carriage and potential permeability defects. Four hundred and eighty-seven isolates that did not carry carbapenemase genes, but were non-susceptible to ertapenem, were investigated by sequence analysis of the genes encoding OmpK35 and OmpK36. Isolates without obvious genetic lesions in either major porin gene were further examined by outer membrane protein SDS-PAGE. RESULTS: The majority of isolates, 83.0 % (404/487), exhibited clear genetic disruption in either or both of the ompK35 and ompK36 genes. Among the proportion of the collection with the highest ertapenem MIC value (>4 mg l-1), 60.5 % (115/190) showed mutation in both porin genes. Isolates without obvious genetic mutations were examined by SDS-PAGE, and 90.4 % (75/83) were found to lack or show altered expression of at least one of the major OMPs when compared to an ertapenem sensitive control strain. CONCLUSION: This study illustrates that porin deficiency in Klebsiella pneumoniae is a widespread phenomenon, and in combination with ESBLs and/or AmpC enzymes, likely accounts for the elevated ertapenem MICs observed in this study.

Prevalence of mcr-type genes among colistin-resistant Enterobacteriaceae collected in 2014-2016 as part of the INFORM global surveillance program.

A set of 908 clinically derived colistin-resistant Enterobacteriaeae isolates collected worldwide in 2014-2016 were screened for the presence of the plasmid-borne mcr-1, mcr-2, mcr-3, mcr-4 and mcr-5 genes. In total 3.2% (29/908) of the collection were positive for mcr, including 27 Escherichia coli, 1 Klebsiella pneumoniae and 1 Enterobacter cloacae. Twenty-four isolates possessed genes from the mcr-1 family, including the original mcr-1 (n = 22), as well as mcr-1.2 (n = 1) and mcr-1.5 (n = 1), which each differ from mcr-1 by encoding single amino acid variations. Genes from the mcr-3 family were found in isolates from Thailand, including mcr-3.1 (n = 3) and mcr-3.2 (n = 1). An E. coli isolated from a patient with a urinary tract infection in Colombia contained the recently discovered mcr-5. The full colistin-resistant collection was tested against a panel of antimicrobial agents with ceftazidime-avibactam and tigecycline exhibiting the highest activity.