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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.

Additional file 3. Environmental sampling sites in Clinics A–C and Clinics/Practices D–G.

Additional file 2. Criteria used for infection prevention and control (IPC) scoring in the seven companion animal institutions and as evaluated during one-day IPC audits. Each IPC topic was scored as follows: all criteria fulfilled = score 2; part of the criteria fulfilled = score 1; no criteria fulfilled = score 0. A score per IPC area and a total score was calculated. The results of the IPC scoring of the participating institutions are given in Table 3 and Additional file 4.

Additional file 4. Detailed infection prevention and control scoring for Clinics/Practices A–G.

Background: Bacteriophages could represent a therapeutic alternative to treat infections caused by multidrug resistant (MDR) pathogens. However studies analyzing their activity against MDR Enterobacteriaceae are limited. Methods: The in vitro lytic activity of three commercial bacteriophage cocktails (PYO INTESTI Septaphage) was evaluated against 70 Escherichia coli and 31 Proteus spp. of human and non human origin. Isolates were characterized by phenotypic and genotypic methods and included 82 MDR strains: 44 ESBL (of which 15 CTX M 15 like including ST131/ST648 E. coli) 27 pAmpC (of which 23 CMY 2 like including ST131 E. coli) 3 ESBL plus pAmpC and 8 carbapenemase producers. Phage susceptibility was determined using the spot test. Results: E. coli susceptibility to PYO INTESTI and Septaphage was 61 67 and 9 whereas that of Proteus spp. was 29 39 and 19 respectively. For the subgroup of ESBL producing E. coli/Proteus spp. the following susceptible rates were recorded: PYO 57; INTESTI 59; and Septaphage 11. With regard to the pAmpC producers 59 70 and 11 resulted susceptible to PYO INTESTI and Septaphage respectively. Five out of 8 carbapenemase producers and 3 out of 4 colistin resistant E. coli were susceptible to PYO and INTESTI. Conclusions: This is the first study analyzing the activity of the above three cocktails against well characterized MDR E. coli and Proteus spp. The overall narrow spectrum of activity observed could be related to the absence of specific bacteriophages targeting these contemporary MDR strains that are spreading in different settings. Therefore bacteriophages targeting emerging MDR pathogens need to be isolated and integrated in such bio preparations.

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.

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