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What Is the Appropriate Meropenem MIC for Screening of Carbapenemase-Producing Enterobacteriaceae in Low-Prevalence Settings?

ABSTRACT: Infection with carbapenemase-producing Enterobacteriaceae (CPE) has been shown to cause significant illness among hospitalized patients. Given the paucity of treatment options, there is a critical need to stop the spread of CPE. However, screening for the presence of CPE in laboratory settings has been challenging. In order to assess the effectiveness of current CPE detection guidelines, we analyzed the meropenem MIC distribution for a large set of clinical Enterobacteriaceae isolates. A total of 1,022 isolates submitted to the Public Health Ontario Laboratories (PHOL) from January 2011 to March 2014 were examined. Only isolates displaying a meropenem or ertapenem MIC of ? 0.25 or ? 1 ?g/ml, respectively, were included. Carbapenemase-positive isolates were identified by multiplex PCR. We identified 189 isolates positive for carbapenemases, which primarily comprised NDM, KPC, and OXA-48-like carbapenemases, and these isolates were largely Klebsiella spp., Escherichia coli, and Enterobacter spp. Interestingly, 14 to 20% of these isolates displayed meropenem MICs within the susceptible range on the basis of CLSI and EUCAST breakpoint interpretive criteria. While the majority of meropenem-susceptible CPE isolates were observed to be E. coli, meropenem susceptibility was not exclusive to any one species/genus or carbapenemase type. Application of CLSI screening recommendations captured only 86% of carbapenemase-producing isolates, whereas application of EUCAST recommendations detected 98.4% of CPE isolates. In a region with a low carbapenemase prevalence, meropenem-based screening approaches require a cutoff MIC near the epidemiological wild-type threshold in order to achieve nearly optimal CPE identification.

SUBMITTER: Fattouh R

PROVIDER: S-EPMC4776007 | biostudies-other | 2015 Dec

REPOSITORIES: biostudies-other

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Project description:BackgroundCarbapenem-resistant Enterobacteriaceae (CRE) are responsible for worldwide outbreaks and antibiotic treatments are problematic. The polysaccharide poly-(?-1,6)-N-acetyl glucosamine (PNAG) is a vaccine target detected on the surface of numerous pathogenic bacteria, including Escherichia coli. Genes encoding PNAG biosynthetic proteins have been identified in two other main pathogenic Enterobacteriaceae, Enterobacter cloacae and Klebsiella pneumoniae. We hypothesized that antibodies to PNAG might be a new therapeutic option for the different pan-resistant pathogenic species of CRE.MethodsPNAG production was detected by confocal microscopy and its role in the formation of the biofilm (for E. cloacae) and as a virulence factor (for K. pneumoniae) was analysed. The in vitro (opsonophagocytosis killing assay) and in vivo (mouse models of peritonitis) activity of antibodies to PNAG were studied using antibiotic-susceptible and -resistant E. coli, E. cloacae and K. pneumoniae. A PNAG-producing strain of Pseudomonas aeruginosa, an organism that does not naturally produce this antigen, was constructed by adding the pga locus to a strain with inactive alg genes responsible for the production of P. aeruginosa alginate. Antibodies to PNAG were tested in vitro and in vivo as above.ResultsPNAG is a major component of the E. cloacae biofilm and a virulence factor for K. pneumoniae. Antibodies to PNAG mediated in vitro killing (>50%) and significantly protected mice against the New Delhi metallo-?-lactamase-producing E. coli (P?=?0.02), E. cloacae (P?=?0.0196) and K. pneumoniae (P?=?0.006), against K. pneumoniae carbapenemase (KPC)-producing K. pneumoniae (P?=?0.02) and against PNAG-producing P. aeruginosa (P?=?0.0013). Thus, regardless of the Gram-negative bacterial species, PNAG expression is the sole determinant of the protective efficacy of antibodies to this antigen.ConclusionsOur findings suggest antibodies to PNAG may provide extended-spectrum antibacterial protective activity.

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What Is the Appropriate Meropenem MIC for Screening of Carbapenemase-Producing Enterobacteriaceae in Low-Prevalence Settings?

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