Abstract
ObjectivesThere are limited data on Enterobacter cloacae outbreaks and fewer describing these in association with NDM-1. With whole-genome sequencing, we tested the hypothesis that a cluster of 16 E. cloacae bacteraemia cases in a Nepali neonatal unit represented a single clonal outbreak, using a wider set of epidemiologically unrelated clinical E. cloacae isolates for comparison.MethodsForty-three isolates were analysed, including 23 E. cloacae and 3 Citrobacter sp. isolates obtained from blood cultures from 16 neonates over a 3 month period. These were compared with two contemporaneous community-associated drug-resistant isolates from adults, a unit soap dispenser isolate and a set of historical invasive isolates (n = 14) from the same geographical locality.ResultsThere were two clear neonatal outbreaks and one isolated case in the unit. One outbreak was associated with an NDM-1 plasmid also identified in a historical community-associated strain. The smaller, second outbreak was likely associated with a contaminated soap dispenser. The two community-acquired adult cases and three sets of historical hospital-associated neonatal isolates represented four additional genetic clusters.ConclusionsE. cloacae infections in this context represent several different transmission networks, operating at the community/hospital and host strain/plasmid levels. Wide sampling frames and high-resolution typing methods are needed to describe the complex molecular epidemiology of E. cloacae outbreaks, which is not appropriately reflected by routine susceptibility phenotypes. Soap dispensers may represent a reservoir for E. cloacae and bacterial strains and plasmids may persist in hospitals and in the community for long periods, sporadically being involved in outbreaks of disease.
Highlights
Several previous outbreaks in neonatal units have been attributed to a variety of sources such as contaminated medications, distilled water in mechanical ventilators and solutions used for parenteral nutrition
The New Delhi metallo-b-lactamase (NDM) carbapenemase was first identified in a Klebsiella pneumoniae strain in a patient originally hospitalized in India.[5]
Sixteen individuals with E. cloacae bloodstream infection were identified in the hospital neonatal unit between 18 November 2012 and 9 February 2013
Summary
Enterobacter cloacae can colonize the human gastrointestinal tract and is an emerging drug-resistant nosocomial pathogen,[1] in neonatal critical care.[2,3] Several previous outbreaks in neonatal units have been attributed to a variety of sources such as contaminated medications, distilled water in mechanical ventilators and solutions used for parenteral nutrition. These are typically controlled by review and improvement of infection control practices.[4] When molecular typing has been deployed as part of epidemiological investigation, most outbreaks appear clonal, based predominantly on analysis by PFGE.[4]. South Asia is one potential reservoir for these genes, with an NDM carriage prevalence of
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