Polyclonal gut colonization with extended-spectrum cephalosporin- and/or colistin-resistant Enterobacteriaceae: a normal status for hotel employees on the island of Zanzibar, Tanzania

For low-income countries, data regarding the intestinal colonization with extended-spectrum cephalosporin-resistant (ESC-R) and colistin-resistant (CST-R) Enterobacteriaceae in the community are still scarce. Here, we investigated this phenomenon by analysing hotel employees in Zanzibar.; During June to July 2018, rectal swabs from 59 volunteers were screened implementing selective enrichments and agar plates. Species identification was achieved using MALDI-TOF MS. Strains were characterized using microdilution panels (MICs), microarray, PCRs for mcr-1/-8, repetitive extragenic palindromic-PCR (rep-PCR) and WGS.; Colonization prevalence with ESC-R-, CST-R- and mcr-1-positive Enterobacteriaceae were 91.5%, 66.1% and 18.6%, respectively (average: 2.2 strains per volunteer). Overall, 55 ESC-R Escherichia coli (3 also CST-R), 33 ESC-R Klebsiella pneumoniae (1 also CST-R), 17 CST-R E. coli and 21 CST-R K. pneumoniae were collected. The following main resistance genes were found: ESC-R E. coli (blaCTX-M-15-like, 51.0%), ESC-R K. pneumoniae (blaCTX-M-9-like, 42.9%), CST-R E. coli (mcr-1, 55%) and CST-R K. pneumoniae (D150G substitution in PhoQ). ESBL-producing E. coli mainly belonged to ST361, ST636 and ST131, whereas all those that were mcr-1 positive belonged to ST46 that carried mcr-1 in a 33 kb IncX4 plasmid. ESBL-producing K. pneumoniae mainly belonged to ST17, ST1741 and ST101, whereas CST-R strains belonged to ST11.; We recorded remarkably high colonization prevalence with ESC-R and/or CST-R Enterobacteriaceae in hotel staff. Further research in the local environment, livestock and food chain is warranted to understand this phenomenon. Moreover, as Zanzibar is a frequent holiday destination, attention should be paid to the risk of international travellers becoming colonized and thereby importing life-threatening pathogens into their low-prevalence countries.