Species Diversity of Environmental GIM-1-Producing Bacteria Collected during a Long-Term Outbreak

Abstract

Reports of outbreaks concerning carbapenemase-producing Gram-negative bacteria in which the main source of transmission is the hospital environment are increasing. This study describes the results of environmental sampling in a protracted polyspecies metallo-beta-lactamase GIM-1 outbreak driven by plasmids and bacterial clones of Enterobacter cloacae and Pseudomonas aeruginosa in a tertiary care center. Environmental sampling targeting wet locations (especially sinks) was carried out on a surgical intensive care unit and on a medical ward on several occasions in 2012 and 2013. We were able to demonstrate 43 bla GIM-1 -carrying bacteria (mainly nonfermenters but also Enterobacteriaceae) that were either related or unrelated to clinical strains in 30 sinks and one hair washbasin. GIM-1 was found in 12 different species, some of which are described here as carriers of GIM-1. Forty out of 43 bacteria displayed resistance to carbapenems and, in addition, to various non-beta-lactam antibiotics. Colistin resistance was observed in two E. cloacae isolates with MICs above 256 mg/liter. The bla GIM-1 gene was harbored in 12 different class 1 integrons, some without the typical 3= end. The bla GIM-1 gene was localized on plasmids in five isolates. In vitro plasmid transfer by conjugation was successful in one isolate. The environment, with putatively multispecies biofilms, seems to be an important biological niche for multidrug-resistant bacteria and resistance genes. Biofilms may serve as a "melting pot" for horizontal gene transfer, for dissemination into new species, and as a reservoir to propagate future hospital outbreaks. IMPORTANCEIn Gram-negative bacteria, resistance to the clinically relevant broad-spectrum carbapenem antibiotics is a major public health concern. Major reservoirs for these resistant organisms are not only the gastrointestinal tracts of animals and humans but also the (hospital) environment. Due to the difficulty in eradicating biofilm formation in the latter, a sustained dissemination of multidrug-resistant bacteria from the environment can occur. In addition, horizontal transfer of resistance genes on mobile genetic elements within biofilms adds to the total "resistance gene pool" in the environment. To gain insight into the transmission pathways of a rare and locally restricted carbapenemases resistance gene (bla GIM-1 ), we analyzed the genetic background of the bla GIM-1 gene in environmental bacteria during a long-term polyspecies outbreak in a German hospital.

Protracted Regional Dissemination of GIM-1-Producing Serratia marcescens in Western Germany

“…The metallo-beta-lactamase GIM-1 is, at this stage, mainly restricted geographically to a confined region in western Germany and represents a serious problem in hospitals in that area (6,7,(9)(10)(11)(12)18). However, bla GIM-1 has also been rarely reported from other regions of Germany (10,19).…”

“…Due to the low MICs of carbapenems for some GIM-1-positive S. marcescens strains (resulting in nondetection of the resistance gene in isolated organisms) and the relatively low prevalence of S. marcescens as a cause of nosocomial infection, this is not an unlikely scenario. Lower MICs of imipenem and meropenem in the susceptible or intermediate range were previously described for GIM-1-harboring bacteria (6,9,10,18). Nevertheless, even the study isolates demonstrating susceptibility to carbapenems would have not been missed, if surveillance were based on the EUCAST recommendations (23).…”

“…E. coli isolates growing on the selective medium were further screened as probable transconjugants for bla GIM-1 . As a positive control, we used a GIM-1-positive Citrobacter freundii strain (strain 2157) with a conjugative plasmid described previously (18). S1 nuclease restriction and hybridization.…”

Biofilm Associated Genotypes of Multidrug-Resistant Pseudomonas aeruginosa

“…P. aeruginosa biofilms are found at surface-liquid, surface-air and liquid-air interfaces, and are a significant clinical problem in wounds and the cystic fibrosis lung 15 . Polymicrobial biofilms are also recognized as important niches for MDR evolution, as they represent a significant reservoir for horizontal gene transfer within and between bacterial species 16 .…”

Characterization of Novel Integrons, In1085 and In1086, and the Surrounding Genes in Plasmids from Enterobacteriaceae, and the Role for attCaadA16 Structural Features during attI1 × attC Integration

“…However, more recent studies have shown that integrons harboring various bla OXA -type genes are present in bacterial plasmids (Wendel et al, 2016). The current study characterizes novel integrons In 1085 and In 1086 and their surrounding genes within bacterial plasmids, and explores the putative mechanism of integron mobilization.…”