Characterization, and comparison, of human clinical and black-headed gull (Larus ridibundus) extended-spectrum β-lactamase-producing bacterial isolates from Kalmar, on the southeast coast of Sweden

• Published in: Journal of antimicrobial chemotherapy 2010-09, Vol.65 (9), p.1939-1944
• Main Authors: Bonnedahl, J., Drobni, P., Johansson, A., Hernandez, J., Melhus, Å., Stedt, J., Olsen, B., Drobni, M.
• Format: Article
• Language: English
• Subjects: Animals; Anti-Bacterial Agents - pharmacology; Antibiotics. Antiinfectious agents. Antiparasitic agents; beta-Lactamases - biosynthesis; beta-Lactamases - genetics; Biological and medical sciences; Charadriiformes - microbiology; clinical; CTX-M; Drug Resistance, Bacterial; environmental; ESBL; Escherichia coli - classification; Escherichia coli - enzymology; Escherichia coli - isolation & purification; Escherichia coli Infections - microbiology; Escherichia coli Infections - transmission; Escherichia coli Infections - veterinary; Escherichia coli Proteins - genetics; Humans; Medical sciences; MEDICIN; MEDICINE; Microbial Sensitivity Tests; Molecular Epidemiology; Pharmacology. Drug treatments; Plasmids; Sweden; wild birds; Zoonotic Ecology; Zoonotisk ekologi
• ISSN: 0305-7453; 1460-2091; 1460-2091
• DOI: 10.1093/jac/dkq222

Background Antibiotic resistance is one of the great challenges for modern healthcare. In Gram-negative bacteria, CTX-M-type extended-spectrum β-lactamases (ESBLs) have been rapidly spreading through Europe since the early 2000s. In Sweden, ESBL-producing Escherichia coli are still rare, but a 3-fold increase has been seen from 2004 to 2007. Enterobacteria and normal flora of wild animals, with or without antibiotic resistance traits, constitute a potential source of human infection and colonization. We studied wild birds with the aim to understand the environmental dissemination of antibiotic resistance and, focusing on clinically relevant resistance types, we made comparisons with human clinical samples. Methods In this study, ESBL-producing human clinical isolates and isolates from juvenile black-headed gulls from Kalmar County hospital and the city of Kalmar, respectively, on the southeast coast of Sweden, were characterized and compared. Results Despite a low frequency of antibiotic resistance among the isolates from gulls, ESBL-producing E. coli isolates were found, two with blaCTX-M-14 and one with blaCTX-M-15. The same CTX-M types were dominant among human ESBL isolates. In addition, gull isolates were dispersed among the human samples in the PhenePlate™ clustering system, indicating that they neither differ from the human isolates nor form any separate clonal clustering. Conclusions The finding of CTX-M-type ESBLs in E. coli isolated from black-headed gulls in Sweden, where ‘background resistance’ is low, is consistent with an ongoing environmental spread of these plasmid-borne resistance genes. The results indicate that a potential for transfer between the human population and environment exists even in countries with a low level of antibiotic resistance.