title: Characterization, and comparison, of human clinical and black-headed gull (Larus ridibundus) extended-spectrum beta-lactamase-producing bacterial isolates from Kalmar, on the southeast coast of Sweden.
abstract: BACKGROUND
  Antibiotic resistance is one of the great challenges for modern healthcare. In Gram-negative bacteria, CTX-M-type extended-spectrum beta-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 bla(CTX-M-14) and one with bla(CTX-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.
authors.affiliation: Department of Medical Sciences/Section of Infectious Diseases, Uppsala University, SE-75185 Uppsala, Sweden.
authors.forename: J
authors.initials: J
authors.lastname: Bonnedahl
authors.forename: P
authors.initials: P
authors.lastname: Drobni
authors.forename: A
authors.initials: A
authors.lastname: Johansson
authors.forename: J
authors.initials: J
authors.lastname: Hernandez
authors.forename: A
authors.initials: A
authors.lastname: Melhus
authors.forename: J
authors.initials: J
authors.lastname: Stedt
authors.forename: B
authors.initials: B
authors.lastname: Olsen
authors.forename: M
authors.initials: M
authors.lastname: Drobni
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D046091:Charadriiformes / Q000382:microbiology*; D024881:Drug Resistance, Bacterial; D004926:Escherichia coli / Q000145:classification* / Q000201:enzymology* / Q000302:isolation & purification; D004927:Escherichia coli Infections / Q000382:microbiology* / Q000635:transmission / Q000662:veterinary*; D029968:Escherichia coli Proteins / Q000235:genetics; D006801:Humans; D008826:Microbial Sensitivity Tests; D017720:Molecular Epidemiology; D010957:Plasmids; D013548:Sweden; D001618:beta-Lactamases / Q000096:biosynthesis* / Q000235:genetics
chemical_list: D000900:Anti-Bacterial Agents; D029968:Escherichia coli Proteins; D001618:beta-Lactamases