Effects of KPC Variant and Porin Genotype on the In Vitro Activity of Meropenem-Vaborbactam against Carbapenem-Resistant Enterobacteriaceae.

Meropenem-vaborbactam is a new agent with the potential to treat carbapenem-resistant Enterobacteriaceae (CRE) infections. We describe the in vitro activity of meropenem-vaborbactam against representative CRE genotypes and laboratory-engineered Escherichia coli isolates harboring mutant blaKPC genes associated with ceftazidime-avibactam resistance. We also compared disk diffusion and gradient strip testing methods to standard broth microdilution methods. Against 120 CRE isolates, median ceftazidime-avibactam and meropenem-vaborbactam MICs were 1 and 0.03 µg/ml, respectively. Ninety-eight percent (117/120) of isolates were susceptible to meropenem-vaborbactam (MICs ≤ 4 µg/ml). Against Klebsiella pneumoniae isolates harboring mutant blaKPC, the addition of vaborbactam lowered the meropenem MICs in 78% of isolates (14/18); 100% were susceptible to meropenem-vaborbactam. Median meropenem-vaborbactam MICs were higher against K. pneumoniae carbapenemase (KPC)-producing K. pneumoniae isolates with mutant ompK36 porin genes (n = 26) than against those with wild-type ompK36 porin genes (n = 54) (0.25 versus 0.03 µg/ml; P < 0.0001). Against E. coli TOP10 isolates with plasmid constructs containing wild-type blaKPC or mutant blaKPC, the addition of vaborbactam at 8 µg/ml lowered the meropenem MICs 2- to 512-fold, resulting in meropenem-vaborbactam MICs of 0.03 µg/ml. The rates of categorical agreement with broth microdilution for disk diffusion or gradient strips ranged from 90 to 95%. Essential agreement rates were higher for research-use-only (RUO) gradient strips manufactured by bioMérieux (82%) than for those manufactured by Liofilchem (48%) (P < 0.0001). Taken together, our data highlight the potent in vitro activity of meropenem-vaborbactam against CRE, including isolates resistant to ceftazidime-avibactam. Vaborbactam inhibited both wild-type and variant KPC enzymes. On the other hand, KPC-producing K. pneumoniae isolates with ompK36 mutations displayed higher meropenem-vaborbactam MICs than isolates with wild-type ompK36 The results of susceptibility testing with RUO bioMérieux gradient strips most closely aligned with those of broth microdilution methods.

Wilson WR ，Kline EG ，Jones CE ，Morder KT ，Mettus RT ，Doi Y ，Nguyen MH ，Clancy CJ ，Shields RK ... -  《-》

Susceptibility evaluation of novel beta-lactam/beta-lactamase inhibitor combinations against carbapenem-resistant Klebsiella pneumoniae from bloodstream infections in hospitalized patients in Brazil.

Novel beta-lactam/beta-lactamase inhibitor (BIBLI) combinations are commercially available and have been used for treating carbapenem-resistant Klebsiella pneumoniae (CRKP) infections. Continuous surveillance of susceptibility profiles and resistance mechanism identification are necessary to monitor the evolution of resistance within these agents. The purpose of this study was to evaluate the susceptibility rates of ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam in CRKP isolated from patients with bloodstream infections who underwent screening for a randomized clinical trial in Brazil. Minimum inhibitory concentrations (MICs) were determined for meropenem, ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam using the gradient diffusion strip method. Carbapenemase genes were detected by multiplex real-time polymerase chain reaction. Klebsiella pneumoniae carbapenemase (KPC)-producing isolates showing resistance to any BLBLI and New Delhi Metallo-beta-lactamase (NDM)-producing isolates with susceptibility to any BLBLI isolates were further submitted for whole-genome sequencing. From a total of 69 CRKP isolates, 39 were positive for blaKPC, 19 for blaNDM and 11 for blaKPC and blaNDM. KPC-producing isolates demonstrated susceptibility rates above 94 % for all BLBLIs. Two isolates with resistance to meropenem/vaborbactam demonstrated a Gly and Asp duplication at the porin OmpK36 as well as a truncated OmpK35. All NDM-producing isolates, including KPC and NDM coproducers, demonstrated susceptibility rates to ceftazidime/avibactam, imipenem/relebactam and meropenem/vaborbactam of 0 %, 9.1-21.1 % and 9.1-26.3 %, respectively. Five NDM-producing isolates that presented susceptibility to BLBLIs also had porin alterations CONCLUSIONS: This study showed that, although high susceptibility rates to BLBLIs were found, KPC-2 isolates were able to demonstrate resistance probably as a result of porin mutations. Additionally, NDM-1 isolates showed susceptibility to BLBLIs in vitro.

Wilhelm CM ，Antochevis LC ，Magagnin CM ，Arns B ，Vieceli T ，Pereira DC ，Lutz L ，de Souza ÂC ，Dos Santos JN ，Guerra RR ，Medeiros GS ，Santoro L ，Falci DR ，Rigatto MH ，Barth AL ，Martins AF ，Zavascki AP ... -  《-》

Activity of ceftazidime/avibactam, meropenem/vaborbactam and imipenem/relebactam against carbapenemase-negative carbapenem-resistant Enterobacterales isolates from US hospitals.

We investigated the prevalence, resistance mechanisms and activity of ceftazidime/avibactam, meropenem/vaborbactam, imipenem/relebactam and comparator agents against carbapenem-resistant Enterobacterales (CRE) that did not carry carbapenemase genes. Among 304 CRE isolates collected in US hospitals during 2016-2018 (1.1% of the overall Enterobacterales), 45 (14.8%) isolates did not carry carbapenemases. These isolates were mainly Klebsiella aerogenes (n = 11), Enterobacter cloacae (n = 11) and Klebsiella pneumoniae (n = 10). Isolates harboured one to six β-lactam resistance mechanisms (median, three mechanisms). Acquired β-lactamase genes were detected in 21 isolates; blaCTX-M-15 was the most common acquired β-lactamase gene found (14 isolates). All 11 K. aerogenes and 6 E. cloacae isolates overexpressed AmpC. Only one isolate belonging to these species carried acquired β-lactamase genes. Disruptions or reduced expression of both outer membrane proteins (ompC/ompK36 and ompF/ompK35) were detected among 20 isolates. AcrAB-TolC was modestly expressed or overexpressed among 19 isolates from six species. One E. coli isolate produced a CTX-M-15 variant that displayed an increased meropenem minimum inhibitory concentration (MIC) when expressed in a clean background. Most β-lactam agents had limited activity against CRE isolates that did not carry carbapenemases. Ceftazidime/avibactam inhibited all isolates, while imipenem/relebactam and meropenem/vaborbactam inhibited 93.0% (88.9% if Proteus mirabilis is included) and 93.3% of tested isolates at current breakpoints. The resistance mechanisms among CRE isolates that did not produce carbapenemases are complex; β-lactam/β-lactamase inhibitor combinations might have different activity against these isolates depending on their resistance mechanisms and the bacterial species.

Castanheira M ，Doyle TB ，Deshpande LM ，Mendes RE ，Sader HS ... -  《-》

In vitro activity of meropenem/vaborbactam and characterisation of carbapenem resistance mechanisms among carbapenem-resistant Enterobacteriaceae from the 2015 meropenem/vaborbactam surveillance programme.

The activity of meropenem/vaborbactam was evaluated against 11 559 Enterobacteriaceae isolates, including 330 carbapenem-resistant phenotypes (CRE) and carbapenemase genotypes collected worldwide during 2015. Antimicrobial susceptibility testing for meropenem/vaborbactam (inhibitor at 8 mg/L) and comparators was performed by the reference broth microdilution method. CRE isolates were screened for the presence of genes encoding carbapenemases, and 292 (88.5%) of the CRE isolates carried these resistance genes. A total of 209 isolates (63.3% of the CRE; 1.8% of the overall Enterobacteriaceae population) carried blaKPC, including genes encoding KPC-2 (90 isolates), KPC-3 (117 isolates) and KPC-17 (2 isolates). Overall, meropenem/vaborbactam (vaborbactam at 8 mg/L) inhibited 99.3% of all Enterobacteriaceae isolates at the US-FDA susceptibility breakpoint of ≤4/8 mg/L. Meropenem alone inhibited 96.9% of the isolates at the current CLSI susceptibility breakpoint of ≤2 mg/L. Susceptibility rates for comparator antimicrobial agents tested against Enterobacteriaceae isolates ranged from 82.1-98.2% applying the CLSI breakpoints. Against CRE isolates, meropenem/vaborbactam displayed MIC50/90 values at 0.5/32 mg/L, whereas meropenem MIC50/90 values were 16/>32 mg/L. Meropenem/vaborbactam was very active against KPC-producers, and 99.5% of these isolates were inhibited by ≤4/8 mg/L. The single resistant isolate was shown to harbour an outer membrane porin alteration. Meropenem/vaborbactam had limited activity against MBL-producing isolates (including 49 NDM-, 1 IMP-64- and 2 VIM-producers) and/or oxacillinases (47 OXA-48/-232) that were detected mainly in European countries. Meropenem/vaborbactam was active against contemporary CRE and wild-type Enterobacteriaceae collected worldwide and this combination demonstrated enhanced activity compared with meropenem and most comparator agents against CRE and KPC-producers.

Pfaller MA ，Huband MD ，Mendes RE ，Flamm RK ，Castanheira M ... -  《-》

Meropenem/vaborbactam activity in vitro: a new option for Klebsiella pneumoniae carbapenemase (KPC)-producing Klebsiella pneumoniae treatment.

Romanelli F ，Stolfa S ，Morea A ，Ronga L ，Prete RD ，Chironna M ，Santacroce L ，Mosca A ... -  《-》