An outpatient clinic as a potential site of transmission for an outbreak of NDM-producing Klebsiella pneumoniae ST716: a study using whole-genome sequencing.

Background The incidence of nosocomial infections due to carbapenem-resistant Klebsiella pneumoniae is increasing worldwide. Whole-genome sequencing (WGS) can help elucidate the transmission route of nosocomial pathogens. Methods We combined WGS and epidemiological data to analyze an outbreak of New Delhi metallo--lactamase (NDM)-producing K. pneumoniae that occurred in 2 Belgian hospitals situated about 50 miles apart. We characterized 74 NDM-producing K. pneumoniae isolates (9 from hospital A, 24 from hospital B, and 41 contemporary isolates from 15 other Belgian hospitals) using pulsed-field gel electrophoresis and WGS. Results A K. pneumoniae sequence type 716 clone was identified as being responsible for the outbreak with all 9 strains from hospital A and 20 of 24 from hospital B sharing a unique pulsotype and being clustered together at WGS (compared with 1 of 41 isolates from other Belgian hospitals). We identified the outpatient clinic of hospital B as the probable bridging site between the hospitals after combining epidemiological, phylogenetic, and resistome data. We also identified the patient who probably caused the transmission. In fact, all but 1 strain from hospital A carried a Tn1331-like transposon, whereas none of the hospital B isolates did. The patient from hospital A who did not have the Tn1331-like transposon was treated at the outpatient clinic of hospital B on the same day as the first NDM-producing K. pneumoniae-positive patient from hospital B. Conclusions The results from our WGS-guided investigation highlight the importance of implementing adequate infection control measures in outpatient settings, especially when healthcare delivery moves from acute care facilities to outpatient clinics. Combining whole-genome sequencing data with epidemiological data, we investigated an outbreak of New Delhi metallo--lactamase-producing Klebsiella pneumoniae across 2 Belgian hospitals. We identified the outpatient clinic as the likely common site of transfer between the 2 institutions.