Quinolone resistance mutations in the faecal microbiota of Swedish travellers to India.
BACKGROUND
International travel contributes to the spread of antibiotic resistant bacteria over the world. Most studies addressing travel-related changes in the faecal flora have focused on specific mobile resistance genes, or depended on culturing of individual bacterial isolates. Antibiotic resistance can, however, also spread via travellers colonized by bacteria carrying chromosomal antibiotic resistance mutations, but this has received little attention so far. Here we aimed at exploring the abundance of chromosomal quinolone resistance mutations in Escherichia communities residing in the gut of Swedish travellers, and to determine potential changes after visiting India. Sweden is a country with a comparably low degree of quinolone use and quinolone resistance, whereas the opposite is true for India.


METHODS
Massively parallel amplicon sequencing targeting the quinolone-resistance determining region of gyrA and parC was applied to total DNA extracted from faecal samples. Paired samples were collected from 12 Swedish medical students before and after a 4-15 week visit to India. Twelve Indian residents were included for additional comparisons. Methods known resistance mutations were common in Swedes before travel as well as in Indians, with a trend for all mutations to be more common in the Indian sub group. There was a significant increase in the abundance of the most common amino acid substitution in GyrA (S83L, from 44 to 72%, p=0.036) in the samples collected after return to Sweden. No other substitution, including others commonly associated with quinolone resistance (D87N in GyrA, S80I in ParC) changed significantly. The number of distinct genotypes encoded in each traveller was significantly reduced after their visit to India for both GyrA (p=0.0020) and ParC (p=0.0051), indicating a reduced genetic diversity, similar to that found in the Indians.


CONCLUSIONS
International travel can alter the composition of the Escherichia communities in the faecal flora, favouring bacteria carrying certain resistance mutations, and, thereby, contributes to the global spread of antibiotic resistance. A high abundance of specific mutations in Swedish travellers before visiting India is consistent with the hypothesis that these mutation have no fitness cost even in the absence of an antibiotic selection pressure.
Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg, Guldhedsgatan 10, SE-413 46, Gothenburg, Sweden. anna.johnning@chalmers.se.|Department of Mathematical Sciences, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden. anna.johnning@chalmers.se.
Anna
A
Johnning
Department of Mathematical Sciences, Chalmers University of Technology, SE-412 96, Gothenburg, Sweden. erik.kristiansson@chalmers.se.
Erik
E
Kristiansson
Department of Clinical Microbiology, Infectious Diseases, Umeå University, SE-901 85, Umeå, Sweden. martin.angelin@umu.se.
Martin
M
Angelin
Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg, Guldhedsgatan 10, SE-413 46, Gothenburg, Sweden. marathenachiket@gmail.com.|Microbial Culture Collection, National Centre for Cell Science, Ganeshkhind, Pune, 411 007, India. marathenachiket@gmail.com.
Nachiket
N
Marathe
Microbial Culture Collection, National Centre for Cell Science, Ganeshkhind, Pune, 411 007, India. yogesh.shouche@gmail.com.
Yogesh S
YS
Shouche
Laboratory for Molecular Infection Medicine Sweden, Department of Clinical Microbiology, Bacteriology, Umeå University, SE- 901 87, Umeå, Sweden. anders.f.johansson@umu.se.
Anders
A
Johansson
Department of Infectious Diseases, Institute of Biomedicine, University of Gothenburg, Guldhedsgatan 10, SE-413 46, Gothenburg, Sweden. joakim.larsson@fysiologi.gu.se.
D G Joakim
DG
Larsson
D000293:Adolescent; D000328:Adult; D002648:Child; D027081:DNA Gyrase / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics; D024881:Drug Resistance, Bacterial; D004925:Escherichia / Q000187:drug effects* / Q000235:genetics*; D005243:Feces / Q000382:microbiology*; D005260:Female; D064368:Healthy Volunteers; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007194:India; D008297:Male; D008969:Molecular Sequence Data; D020125:Mutation, Missense; D015363:Quinolones / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D013548:Sweden; D014195:Travel; D055815:Young Adult
D015363:Quinolones; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase