Dataset Information

Characterization of Enterobacter cloacae and Citrobacter freundii species complex isolates with decreased susceptibility to cephalosporins from United States hospitals and activity of ceftazidime/avibactam and comparator agents.

ABSTRACT:

Objectives

To evaluate the antimicrobial susceptibility and resistance mechanisms to β-lactams among Enterobacter cloacae and Citrobacter freundii from United States medical centres.

Methods

2571 E. cloacae and 1008 C. freundii species complex isolates were consecutively collected from 77 medical centres and susceptibility tested by broth microdilution method. Isolates displaying MIC values ≥16 mg/L for ceftazidime or ≥2 mg/L for cefepime (n = 914) were tested for β-lactamase-encoding genes using whole genome sequencing.

Results

Overall susceptibility to ceftazidime and cefepime were 73.9% and 91.2% among E. cloacae and 74.2% and 93.5% among C. freundii, respectively. Sixty-three isolates harboured a carbapenemase gene, including 56 bla _KPC, 2 bla _NMC-A, and 5 metallo-β-lactamase genes. Among non-carbapenemase producers, 121 isolates had at least one ESBL-encoding gene, mainly bla _SHV (81) or bla _CTX-M (61), and 15 had a transferable AmpC gene, mainly bla _DHA-1 (8) or bla _FOX-5 (6). Carbapenemase, ESBL, or transferable AmpC-encoding genes were not identified among 718 of 914 (78.6%) isolates sequenced. The most active agents against isolates with a decreased susceptibility to ceftazidime and/or cefepime were ceftazidime/avibactam (MIC_50/90, 0.5/1 mg/L; 99.3% susceptible), amikacin (MIC_50/90, 1/4 mg/L; 99.5% susceptible), and meropenem (MIC_50/90, 0.06/0.5 mg/L; 92.9% susceptible). The isolates resistant to ceftazidime/avibactam were the five MBL producers and one E. cloacae isolate with a reduced expression of OmpF and overexpression of AcrAB-TolC.

Conclusions

Hyperproduction of chromosomal AmpC appears to be the most common mechanism of resistance to ceftazidime and/or cefepime in E. cloacae and C. freundii. Ceftazidime/avibactam remained highly active against most isolates showing decreased susceptibility to ceftazidime and/or cefepime.

SUBMITTER: Sader HS

PROVIDER: S-EPMC8378278 | biostudies-literature |

REPOSITORIES: biostudies-literature

ACCESS DATA

Similar Datasets

Project description:A bla KPC-2-carrying Citrobacter freundii isolate developed ceftazidime-avibactam resistance during treatment with this agent. The initial and follow-up isolates exhibited ceftazidime-avibactam MICs of 4 and 64?µg/ml, respectively. Overexpression of AcrAB-TolC and porin alterations were detected in both isolates, but no other resistance mechanism was observed. After passaging the initial clinical isolate in ceftazidime-avibactam at a fixed concentration of 4?µg/ml and a 4:1 ratio, resistance to all ?-lactams was noted, and a percentage of the bla KPC-2 sequencing reads had mutations leading to the alterations D176Y (bla KPC-2-D176Y [78%]) or R164S plus P147L (bla KPC-2-R164S + P147L [82%]). Further investigation of the follow-up isolate showed that 11% of the bla KPC-2 reads had mutations leading to D179Y substitution (bla KPC-2-D179Y). In the absence of selective pressure, ceftazidime-avibactam MICs of the passaged and follow-up isolates revealed that 7 or 8 out of 20 screened colonies reverted to susceptible and possessed bla KPC-2 wild-type sequences. Recombinant plasmids carrying the bla KPC-2 alterations observed were transformed in Escherichia coli, and MIC values for ceftazidime ± avibactam were elevated. Lower MICs for ceftriaxone, cefepime, aztreonam, meropenem, and imipenem for the mutated KPC-2-producing isolates were observed compared to those of the isolates producing a wild-type KPC-2. Avibactam at a fixed concentration of 4?µg/ml restored the activity of all ?-lactams tested for the recombinant strains. The heterogenous population of wild-type and mutated bla KPC-2 and the reversibility of the genotypes observed suggest a significant challenge for managing KPC-producing isolates that develop ceftazidime-avibactam resistance during therapy.IMPORTANCE The development of ceftazidime-avibactam resistance among KPC-producing isolates during treatment with this agent has been reported. Usually isolates that become resistant have a mutated bla KPC gene that confers resistance to ceftazidime-avibactam and susceptibility to meropenem. We report a Citrobacter freundii isolate that developed ceftazidime-avibactam resistance due to mutations within the coding region of the bla KPC-2 ?-loop previously reported; however, in this case, only 11% of the whole-genome sequencing reads had mutations, making this alteration difficult to detect and the treatment of these isolates more challenging. In addition to bla KPC, the initial and the follow-up patient isolates displayed hyperexpression of the AcrAB-TolC efflux system and disruption of the outer membrane protein (OMP) OmpF, which contribute to carbapenem resistance. Experiments performed to confirm our findings included generating mutant isolates from the initial patient isolate, passaging the isolates for purity in drug-free medium, resulting in a reversible phenotype, and cloning the mutations to demonstrate the resistance conferred.

Project description:BackgroundCeftazidime-avibactam has in vitro activity against some carbapenem-resistant gram-negative infections (GNIs), and therefore may be a useful alternative to more toxic antibiotics such as colistin. Understanding ceftazidime-avibactam uptake and usage patterns would inform hospital formularies, stewardship, and antibiotic development.MethodsA retrospective cohort study assessed inpatient encounters in the Vizient database. Ceftazidime-avibactam and colistin administrations were categorized into presumed empiric (3 consecutive days of therapy or less with qualifying exclusions) versus targeted therapy (≥4 consecutive days of therapy) for presumed carbapenem-resistant GNIs. Quarterly percentage change (QPC) using modified Poisson regression and relative change in frequency of targeted ceftazidime-avibactam to colistin encounters was calculated. Factors associated with preferentially receiving targeted ceftazidime-avibactam versus colistin were identified using generalized estimating equations.ResultsBetween 2015 quarter (q) 1 and 2017q4, ceftazidime-avibactam was administered 21 215 times across 1901 encounters. Inpatient prescriptions for ceftazidime-avibactam increased from 0.44/10 000 hospitalizations in 2015q1 to 7.7/10 000 in 2017q4 (QPC, +11%; 95% CI, 10-13%; P < .01), while conversely colistin prescriptions decreased quarterly by 5% (95% CI, 4-6%; P < .01). Ceftazidime-avibactam therapy was categorized as empiric 25% of the time, targeted 65% of the time, and indeterminate 10% of the time. Patients with chronic kidney disease were twice as likely to receive targeted ceftazidime-avibactam versus colistin (RR, 2.02; 95% CI, 1.82-2.25), whereas those on dialysis were less likely to receive ceftazidime-avibactam than colistin (RR, 0.71; 95% CI, .61-.83).ConclusionsSince approval in 2015, ceftazidime-avibactam use has grown for presumed carbapenem-resistant GNIs, while colistin has correspondingly declined. Renal function drove the choice between ceftazidime-avibactam and colistin as targeted therapy.

Project description:Enterobacter cloacae has recently emerged as one of the most common carbapenem-resistant Enterobacteriaceae. The emergence and spread of metallo-?-lactamase-producing E. cloacae have posed an immediate threat globally. Here, we investigated the molecular characteristics of 84 carbapenem-resistant Enterobacter cloacae (CREL) collected from three tertiary hospitals in China between 2012 and 2016. Species identification and antimicrobial susceptibility testing were performed using a VITEK-2 system. Carbapenems, polymyxins B, and tigecycline were tested by broth microdilution method. The carbapenem in activation method (CIM) and cefoxitin three-dimensional test were used to detect carbapenemase and AmpC ?-lactamase, respectively. Isolates were screened for ?-lactam resistance genes by PCR, and expression of ompC and ompF was determined by qRT-PCR. Genetic relatedness was performed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST), while selected isolates were subjected to whole-genome sequencing. Among the 84 CREL isolates, 50 (59.5%) were detected as carbapenemase producers. NDM-1 was the dominant carbapenemase (80.0%), followed by IMP-26 (8.0%) and IMP-4 (6.0%). Notably, we identified the first NDM-1 and IMP-1 co-producing E. cloacae, carrying plasmids of several incompatibility (Inc) groups, including IncHI2, IncHI2A, and IncN. Most isolates showed decreased expression of ompC and/or ompF, and contained a broad distribution of ESBLs and AmpC ?-lactamases. These findings suggested that different molecular mechanisms, including carbapenemase, ESBL and/or AmpC plus loss of porins, have contributed to carbapenem resistance. The bla NDM-1-harboring plasmids contained highly conserved gene environment around bla NDM-1 (bla NDM-1-ble MBL-trpF-dsbD-cutA1-groES-groEL), which could be associated with the potential dissemination of bla NDM-1. IMP-type MBL was located within a variety of integrons and usually contained various gene cassettes encoding multidrug resistance. These isolates produced 54 different pulsotypes, and were classified into 42 STs by MLST. Nineteen bla NDM-1-positive E. cloacae isolates obtained from Ningxia had the same pulsotype (PFGE type 1), belonging to ST78 within clonal complex 74 (CC74). The plasmid-based replicon typing indicated that IncX3 plasmids mediated the dissemination of bla NDM-1 among these homologous strains. This is the first report on the outbreak of NDM-1-producing E. cloacae ST78 with contribution of IncX3 plasmids in Northwestern China. There's an immediate need to intensify surveillance attentively to prevent and control the further spread of NDM-1 in China.