Genomic analysis of hospital plumbing exposes a reservoir of bacterial plasmids conferring carbapenem resistance

Carbapenemase-producing organisms are a serious concern due to a high rate of morbidity and mortality associated with these resistant Gram-negative bacteria

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Carbapenem drug resistance, mostly among Gram-negative pathogens, is a current worldwide public-health problem. Particularly when mediated by transferable carbapenemase-encoding genes, the mechanisms of carbapenem resistance spread quickly initiating serious outbreaks, highly restricting the treatment options. The resistance mechanism to new bacteria can occur through horizontal plasmid transfer spreads, thus, understanding the plasmid ecology of the hospital environment can help preventing nosocomial infections.  

A recent 5-year genomic and epidemiological survey was undertaken in the National Institutes of Health Clinical Center, Maryland, USA, to study the CPOs in the patient-accessible environment, and in the plumbing system removed from the patient. The authors reported a vast, unappreciated reservoir of CPOs in wastewater, contrasting to the low positivity rate in both the patient population and the patient-accessible environment. Results also demonstrated that, though there were limited patient-environmental isolate relations, there were plasmid backbones common to both populations.


The hospital environment is a potential reservoir of bacteria with plasmids conferring carbapenem resistance. Our Hospital Epidemiology Service routinely performs extensive sampling of high-touch surfaces, sinks, and other locations in the hospital. Over a 2-year period, additional sampling was conducted at a broader range of locations, including housekeeping closets, wastewater from hospital internal pipes, and external manholes. We compared these data with previously collected information from 5 years of patient clinical and surveillance isolates. Whole-genome sequencing and analysis of 108 isolates provided comprehensive characterization of blaKPC/blaNDM-positive isolates, enabling an in-depth genetic comparison. Strikingly, despite a very low prevalence of patient infections with blaKPC-positive organisms, all samples from the intensive care unit pipe wastewater and external manholes contained carbapenemase-producing organisms (CPOs), suggesting a vast, resilient reservoir. We observed a diverse set of species and plasmids, and we noted species and susceptibility profile differences between environmental and patient populations of CPOs. However, there were plasmid backbones common to both populations, highlighting a potential environmental reservoir of mobile elements that may contribute to the spread of resistance genes. Clear associations between patient and environmental isolates were uncommon based on sequence analysis and epidemiology, suggesting reasonable infection control compliance at our institution. Nonetheless, a probable nosocomial transmission of Leclercia sp. from the housekeeping environment to a patient was detected by this extensive surveillance. These data and analyses further our understanding of CPOs in the hospital environment and are broadly relevant to the design of infection control strategies in many infrastructure settings

Reference: Weingarten RA, Johnson RC, Conlan S, Ramsburg AM, Dekker JP, Lau AF, Khil P, Odom RT, Deming C, Park M, Thomas PJ, NISC Comparative Sequencing Program, Henderson DK, Palmore TN, Segre JA, Frank KM. 2018. Genomic analysis of hospital plumbing reveals diverse reservoir of bacterial plasmids conferring carbapenem resistance. mBio 9:e02011-17.

Celia Fortuna Rodrigues

PharmD, PhD , University of Porto


Go to the profile of Salvatore Mandalà
over 4 years ago

This is really worrying!

Go to the profile of Celia Fortuna Rodrigues
over 4 years ago

Yes, it is. :(