An outbreak of OXA-232 expressing carbapenem resistant Klebsiella pneumoniae (CRKP) infections was identified at our institution. The OXA-232 isolate was recovered from 9 patients, 8 of whom had endoscopic retrograde cholangiopancreatography (ERCP) procedure performed prior to infection (first case, in October 2014), and 1 of whom had recent travel history to India (isolate recovered in October 2014). Whole genome sequencing (WGS) was used to evaluate the genetic relatedness of OXA-232 isolates at our institution.
All carbapenem resistant Enterobacteriaceae isolated in 2014 were screened for OXA-232 by PCR. All patients exposed to ERCP duodenoscopes from October 2014 and January 2015 were also screened for colonization by rectal swabs, which were plated to a MacConkey Agar. Colonies were screened for meropenem resistance and presence of OXA-232 gene. WGS, using an Illumina MiSeq, was performed for selected OXA-232 isolates. Data analysis was done by using A5-miseq, RAST, CONTIGuator, BRIG and Center for Genomic Epidemiology tools.
7 of 173 patients were identified as colonized with OXA-232 CRE, one of which was selected for sequencing. Genomic sequences of the 8 OXA-232 clinical isolates associated with ERCP had > 99% identity with the OXA-232 isolated from the patient with travel to India, indicating close genetic relatedness. Similarly, the surveillance isolate was > 99% identical to the other OXA-232 isolates. SNPs phylogenetic tree analysis and genome alignment showed these isolates were closely related to XH209, a CRKP strain first reported in China. WGS identified both blaOXA-232 (on a 6.4 kb plasmid), and blaCTX-M-15 (on a 4.8 kb transposon), which contributed to carbapenem and cephem resistance in these isolates. Interestingly, the 4.8kb blaCTX-M-15 carrying transposon was missing in the surveillance isolate, and this isolate was susceptible to 3rd and 4th generation cephalosporins and aztreonam.
WGS identified the index patient and established definitive molecular epidemiology for the CRKP outbreak. WGS also provided crucial information for understanding antimicrobial resistance mechanisms. No clear epidemiological link could be established between the index patient and the patients with ERCP.
J. Hindler, None
K. Ward, None
F. Li, None
H. Adisetiyo, None
G. Aldrovandi, None
R. M. Humphries, None