Abstract
This assessment describes the enteric colonization of German soldiers 8–12 weeks after returning from mostly but not exclusively subtropical or tropical deployment sites with third-generation cephalosporin-resistant Enterobacteriaceae, vancomycin-resistant enterococci (VRE), and methicillin-resistant Staphylococcus aureus (MRSA). Between 2007 and 2015, 828 stool samples from returning soldiers were enriched in nonselective broth and incubated on selective agars for Enterobacteriaceae expressing extended-spectrum beta-lactamases (ESBL), VRE and MRSA. Identification and resistance testing of suspicious colonies was performed using MALDI-TOF-MS, VITEK-II and agar diffusion gradient testing (bioMérieux, Marcy-l’Étoile, France). Isolates with suspicion of ESBL were characterized by ESBL/ampC disc-(ABCD)-testing and molecular approaches (PCR, Sanger sequencing). Among the returnees, E. coli with resistance against third-generation cephalosporins (37 ESBL, 1 ESBL + ampC, 1 uncertain mechanism) were found in 39 instances (4.7%). Associated quinolone resistance was found in 46.2% of these isolates. Beta-lactamases of the blaCTX-M group 1 predominated among the ESBL mechanisms, followed by the blaCTX-M group 9, and blaSHV. VRE of vanA-type was isolated from one returnee (0.12%). MRSA was not isolated at all. There was no clear trend regarding the distribution of resistant isolates during the assessment period. Compared with colonization with resistant bacteria described in civilians returning from the tropics, the colonization in returned soldiers is surprisingly low and stable. This finding, together with high colonization rates found in previous screenings on deployment, suggests a loss of colonization during the 8- to 12-week period between returning from the deployments and assessment.
Highlights
Spread of multidrug-resistant bacteria is a global concern, involving subtropical and tropical war and crisis zones where international armed forces are deployed
The distribution of the detected third-generation cephalosporin-resistant E. coli ranged from 0% to 18.7% of analyzed samples (Table 3)
Close household contacts have been identified as a major source for the spread and as a reservoir for long-term persistence and distribution of resistant bacteria outside of the hospital environment [36]
Summary
Spread of multidrug-resistant bacteria is a global concern, involving subtropical and tropical war and crisis zones where international armed forces are deployed. Extended-spectrum betalactamase (ESBL)-producing Enterobacteriaceae are frequent colonizers in the gastrointestinal tract of civilian returnees from the tropics [1,2,3,4]. Contacts with medical infrastructure in central African settings have been described with subsequent colonization rates with ESBL-positive Enterobacteriaceae up to >90% [5]. Antibiotic pressure contributes to the colonization with ESBL-expressing or multidrug-resistant bacteria [1]. Enteric colonization with atypically resistant or multidrug-resistant pathogens does not necessarily mean obligate progression to infections [1], . The average colonization time in case of enteric colonization with ESBL-expressing Gram-negative bacteria is estimated to be between a few months and a year, cases of long-term shedding have been described [6]
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