Travellers returning from the island of Zanzibar colonized with MDR Escherichia coli strains: assessing the impact of local people and other sources.

OBJECTIVES: Many travellers to low-income countries return home colonized at the intestinal level with extended-spectrum cephalosporin-resistant (ESC-R) and/or colistin-resistant (CST-R) Escherichia coli (Ec) strains. However, nothing is known about the local sources responsible for the transmission of these pathogens to the travellers. METHODS: We compared the ESC-R- and CST-R-Ec strains found in the pre- (n = 23) and post-trip (n = 37) rectal swabs of 37 travellers from Switzerland to Zanzibar with those (i) contemporarily isolated from local people, poultry, retailed chicken meat (n = 31), and (ii) from other sources studied in the recent past (n = 47). WGS and core-genome analyses were implemented. RESULTS: Twenty-four travellers returned colonized with ESC-R- (n = 29) and/or CST-R- (n = 8) Ec strains. Almost all ESC-R-Ec were CTX-M-15 producers and belonged to heterogeneous STs/core-genome STs (cgSTs), while mcr-positive strains were not found. Based on the strains' STs/cgSTs, only 20 subjects were colonized with ESC-R- and/or CST-R-Ec that were not present in their gut before the journey. Single nucleotide variant (SNV) analysis showed that three of these 20 travellers carried ESC-R-Ec (ST3489, ST3580, ST361) identical (0-20 SNVs) to those found in local people, chicken meat, or poultry. Three further subjects carried ESC-R-Ec (ST394, ST648, ST5173) identical or highly related (15-55 SNVs) to those previously reported in local people, fish, or water. CONCLUSIONS: This is the first known study comparing the ESC-R- and/or CST-R-Ec strains obtained from travellers and local sources using solid molecular methods. We showed that for at least one-third of the returning travellers the acquired antibiotic-resistant Ec had a corresponding strain among resident people, food, animal and/or environmental sources.

On the island of Zanzibar people in the community are frequently colonized with the same MDR Enterobacterales found in poultry and retailed chicken meat.

OBJECTIVES: Intestinal colonization with extended-spectrum cephalosporin-resistant (ESC-R) and colistin-resistant (CST-R) Enterobacterales (Ent) can be driven by contact with colonized animals and/or contamination of the food chain. We studied the ESC-R-Ent and COL-R-Ent colonizing poultry as well as contaminating chicken meat in Zanzibar (Tanzania). Results were compared with recently published data obtained from rectal swabs of people in the community. METHODS: During June and July 2018, we collected poultry faecal material (n = 62) and retail chicken meat (n = 37) samples. ESC-R and CST-R strains were isolated implementing selective approaches and characterized with different molecular methods, including WGS coupled with core-genome analyses. RESULTS: The prevalence of ESC-R-Ent and CST-R-Ent, respectively, were: 88.7% and 48.4% in poultry; and 43.2% and 18.9% in chicken meat. Overall, the following strains and main resistance mechanisms were found in the two settings: 69 ESC-R Escherichia coli (CTX-M-15 subgroup, 75%), 34 ESC-R Klebsiella pneumoniae (CTX-M-9 group, 54.5%), 24 non-ESC-R but CST-R E. coli (mcr-1, 95.8%) and 17 non-ESC-R but CST-R K. pneumoniae (D150G substitution in PhoQ). Several clones (differing by only 0-13 single nucleotide variants) were concomitantly and frequently found in human and non-human settings: mcr-1-carrying E. coli ST46; CTX-M-15-producing E. coli ST361; CTX-M-14-producing K. pneumoniae ST17; and CTX-M-15-producing K. pneumoniae ST1741. CONCLUSIONS: This is one of the few studies that have assessed the occurrence of identical MDR Enterobacterales in human and non-human settings. The frequent human gut colonization observed in the community might be favoured by the spread of ESC-R-Ent and CST-R-Ent in poultry and chicken meat. Further studies with a One Health approach should be carried out to better investigate this phenomenon.

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

OBJECTIVES: 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. METHODS: 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. RESULTS: 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. CONCLUSIONS: 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.