Carbapenemase-producing Enterobacteriaceae in hospital wastewater: a reservoir that may be unrelated to clinical isolates.
BACKGROUND
Carbapenemase-producing Enterobacteriaceae (CPE) are an emerging infection control problem in hospitals worldwide. Identifying carriers may help reduce potential spread and infections.


OBJECTIVE
To assess whether testing hospital wastewater for CPE can supplement patient-based screening for infection prevention purposes in a hospital without a recognized endemic CPE problem.


METHODS
Wastewater collected from hospital pipework on 16 occasions during February to March 2014 was screened for CPE using chromID(®) CARBA agar and chromID(®) CPS agar with a 10μg ertapenem disc and combination disc testing. Minimum inhibitory concentrations were determined using British Society for Antimicrobial Chemotherapy methodology and carbapenemase genes detected by polymerase chain reaction or whole-genome sequencing. Selected isolates were typed by pulsed-field gel electrophoresis.


RESULTS
Suspected CPE were recovered from all 16 wastewater samples. Of 17 isolates sent to the Antimicrobial Resistance and Healthcare Associated Infections Reference Unit, six (four Citrobacter freundii and two Enterobacter cloacae complex) were New Delhi metallo-β-lactamase (NDM) producers and the remaining 11 (six Klebsiella oxytoca and five Enterobacter cloacae complex) were Guiana-Extended-Spectrum-5 (GES-5) producers, the first to be described among Enterobacteriaceae in the UK. The four NDM-producing C. freundii, two NDM-producing E. cloacae complex, and four out of five GES-5-producing E. cloacae complex were each indistinguishable isolates of the same three strains, whereas the six GES-5-producing K. oxytoca overall shared 79% similarity.


CONCLUSIONS
CPE are readily isolated from hospital wastewater using simple culture methods. There are either undetected carriers of CPE excreting into the wastewater, or these CPE represent colonization of the pipework from other sources. Surveillance of hospital wastewater for CPE does not appear helpful for infection control purposes within acute hospitals.
Microbiology Department, Royal Preston Hospital, Lancashire Teaching Hospitals NHS Foundation Trust, Preston, UK. Electronic address: Leila.white@lthtr.nhs.uk.
L
L
White
Antimicrobial Resistance and Healthcare Associated Infections Reference Unit (AMRHAI), National Infection Service, Public Health England, London, UK.
K L
KL
Hopkins
Antimicrobial Resistance and Healthcare Associated Infections Reference Unit (AMRHAI), National Infection Service, Public Health England, London, UK.
D
D
Meunier
Antimicrobial Resistance and Healthcare Associated Infections Reference Unit (AMRHAI), National Infection Service, Public Health England, London, UK.
C L
CL
Perry
Antimicrobial Resistance and Healthcare Associated Infections Reference Unit (AMRHAI), National Infection Service, Public Health England, London, UK.
R
R
Pike
Microbiology Department, Royal Preston Hospital, Lancashire Teaching Hospitals NHS Foundation Trust, Preston, UK.
P
P
Wilkinson
Biomedical and Life Sciences, Faculty of Health and Medicine, Furness College, Lancaster University, Lancaster, UK.
R W
RW
Pickup
Microbiology Department, Royal Preston Hospital, Lancashire Teaching Hospitals NHS Foundation Trust, Preston, UK.
J
J
Cheesbrough
Antimicrobial Resistance and Healthcare Associated Infections Reference Unit (AMRHAI), National Infection Service, Public Health England, London, UK.
N
N
Woodford
D001426:Bacterial Proteins / Q000378:metabolism*; D001431:Bacteriological Techniques / Q000379:methods; D004755:Enterobacteriaceae / Q000187:drug effects / Q000201:enzymology* / Q000302:isolation & purification*; D005838:Genotype; D006761:Hospitals; D006801:Humans; D008403:Mass Screening / Q000379:methods; D016133:Polymerase Chain Reaction; D017422:Sequence Analysis, DNA; D006113:United Kingdom; D062065:Wastewater / Q000382:microbiology*; D001618:beta-Lactamases / Q000378:metabolism*
D001426:Bacterial Proteins; D062065:Wastewater; D001618:beta-Lactamases; C063912:carbapenemase
Carbapenem resistance; Guiana-Extended-Spectrum-5 (GES-5); Metallo-β-lactamase; Surveillance