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3129400 
Journal Article 
Molecular characterization of antibiotic resistance in Escherichia coli strains from a dairy cattle farm and its surroundings 
Navajas-Benito, EV; Alonso, CA; Sanz, S; Olarte, C; Martínez-Olarte, R; Hidalgo-Sanz, S; Somalo, S; Carmentorres, S 
2016 
1 
Journal of the Science of Food and Agriculture
ISSN: 0022-5142
EISSN: 1097-0010 
English 
26969806 
BACKGROUND: This study describes the phenotypic and genotypic characteristics of 78 genetically different Escherichia coli recovered from the air and exudate samples of a dairy cattle farm and its surroundings in Spain, in order to gain insight into the flow of antimicrobial resistance through the environment and food supply.

RESULTS: Antimicrobial resistance was detected in 21.8% of the 78 E. coli isolates analyzed (resistance for at least one of the 14 agents tested). The highest resistance rates were recorded for ampicillin, nalidixic acid, trimethoprim/sulfamethoxazole and tetracycline. The resistance genes detected were as follows [antibiotic (number of resistant strains), gene (number of strains)]: ampicillin (9), blaTEM-1 (6); tetracycline (15), tet(A) (7), tet(B) (4), tet(A)+ tet(B) (1); chloramphenicol (5), cmlA (2), floR(2); trimethoprim/sulfamethoxazole (10), sul2 (4), sul1 (3), sul3 (2), sul1+ sul2 (1); gentamicin-tobramycin (1), ant(2") (1). About 14% of strains showed a multidrug-resistant phenotype and, of them, 7 strains carried class 1 integrons containing predominantly the dfrA1-aadA1 array. One multidrug-resistant strain was found in both inside and outside air, suggesting that the airborne spread of multidrug-resistant bacteria from the animal housing facilities to the surroundings is feasible.

CONCLUSIONS: This study gives a genetic background of the antimicrobial resistance problem in a dairy cattle farm and shows that air can act as a source for dissemination of antimicrobial-resistant bacteria.