Shedding of OXA-181 carbapenemase-producing Escherichia coli from companion animals after hospitalisation in Switzerland: an outbreak in 2018

BACKGROUND: Carbapenem-resistant Enterobacteriaceae pose a serious threat to public health worldwide, and the role of companion animals as a reservoir is still unclear. AIMS: This 4-month prospective observational study evaluated carriage of carbapenem-resistant Enterobacteriaceae at admission and after hospitalisation in a large referral hospital for companion animals in Switzerland. METHODS: Rectal swabs of dogs and cats expected to be hospitalised for at least 48 h were taken from May to August 2018 and analysed for the presence of carbapenem-resistant Enterobacteriaceae using selective agar plates. Resistant isolates were further characterised analysing whole genome sequences for resistance gene and plasmid identification, and ad hoc core genome multilocus sequence typing. RESULTS: This study revealed nosocomial acquisition of Escherichia coli harbouring the carbapenemase gene bla (OXA-181), the pAmpC cephalosporinase gene bla (CMY-42) as well as quinolone resistance associated with qnrS1 and mutations in the topoisomerases II (GyrA) and IV (ParC). The bla (OXA-181) and qnrS1 genes were identified on a 51 kb IncX3 plasmid and bla (CMY-42) on a 47 kb IncI1 plasmid. All isolates belonged to sequence type ST410 and were genetically highly related. This E. coli clone was detected in 17 of 100 dogs and four of 34 cats after hospitalisation (21.6%), only one of the tested animals having tested positive at admission (0.75%). Two positive animals were still carriers 4 months after hospital discharge, but were negative after 6 months. CONCLUSIONS: Companion animals may acquire carbapenemase-producing E. coli during hospitalisation, posing the risk of further dissemination to the animal and human population and to the environment.