Risk factors associated with the antimicrobial resistance of Staphylococcus aureus isolated from bovine mastitis

Abstract

Pesq. Vet. Bras. 34(10):947-952, outubro 2014 947 RESUMO.-[Fatores de risco associados com a resistên-cia antimicrobiana de Staphylococcus aureus isolados da mastite bovina.] Objetivou-se com este estudo avaliar os fatores de risco associados às práticas de manejo e tratamento de mastite e a resistência aos antimicrobianos de Staphylococcus aureus isolados de vacas com mastite. Foram selecionados para o presente estudo 13 rebanhos localizados na região de Pirassununga/SP. Foi aplicado um questionário contendo informações para o levantamento de fatores de risco relacionados à resistência aos antimicrobianos e às práticas de manejo e tratamento de mastite. Após a seleção dos rebanhos e aplicação dos questionários, foram utilizados 210 isolados de S. aureus de amostras compostas de leite coletadas durante 24 meses, em quatro períodos, para realização dos testes de resistência. Os antimicrobianos testados foram: ampicilina 10µg, clindamicina 2µg, penicilina 1µg, eftiofour 30µg, gentamicina 10µg, sulfatrimetropin 25µg, enrofloxacina 5µg, sulfonamida 300µg, tetraciclina 30µg, oxacilina 1µg, cefalotina 30µg e eritromicina 5µg. As variáveis que foram significativamente as- The objective of this study was to evaluate herd management practices and mastitis treatment procedures as risk factors associated with Staphylococcus aureus antimicrobial resistance. For this study, 13 herds were selected to participate in the study to evaluate the association between their management practices and mastitis treatment procedures and in vitro antimicrobial susceptibility. A total of 1069 composite milk samples were collected aseptically from the selected cows in four different periods over two years. The samples were used for microbiological culturing of S. aureus isolates and evaluation of their antimicrobial susceptibility. A total of 756 samples (70.7%) were culture-positive, and S. aureus comprised 27.77% (n=210) of the isolates. The S. aureus isolates were tested using the disk-diffusion susceptibility assay with the following antimicrobials: ampicillin 10mg; clindamycin 2μg; penicillin 1mg; ceftiofur 30μg; gentamicin 10mg; sulfa-trimethoprim 25μg; enrofloxacin 5μg; sulfonamide 300μg; tetracycline 30μg; oxacillin 1mg; cephalothin 30μg and erythromycin 5μg. The variables that were significantly associated with S. aureus resistance were as follows: the treatment of clinical mastitis for ampicillin (OR=2.18), dry cow treatment for enrofloxacin (OR=2.11) and not sending milk samples for microbiological culture and susceptibility tests, for ampicillin (OR=2.57) and penicillin (OR=4.69). In conclusion, the identification of risk factors for S. aureus resistance against various mastitis antimicrobials is an important information that may help in practical recommendations for prudent use of antimicrobial in milk production.

Antimicrobial resistance and genotypic relatedness of environmental staphylococci in semi-extensive dairy farms

“…This could be related to the fact that S. aureus is an important intramammary infectious agent in dairy cows and normally found in milk. Similar results were reported by Beuron et al. (2014) .…”

Antimicrobial resistance profiles of Staphylococcus aureus clusters on small dairy farms in southern Brazil

“…Among the sampled farms, only clinical mastitis cases were treated with antimicrobials and no susceptibility test was performed. In Brazilian herds, a higher chance of S. aureus resistant to penicillin and ampicillin was found in farms that did not perform microbiological cultures and susceptibility tests (Beuron et al 2014). In the aforementioned study, herds with a higher number of lactating cows (from 10 to >60) were sampled, while in our study 80% of the sampled farms had less than 15 cows in lactation.…”

EFSA's assistance for the 2015 Codex Committee on Residues of Veterinary Drugs in Food (CCRVDF) in relation to rBST

“… The effect of the use of antimicrobials in increasing resistance in mastitis pathogens has been discussed in several papers, and studies have shown that bacteria isolated from cases of mastitis have developed resistance to antimicrobials that have been extensively used over the years in dairy cattle (Saini et al, 2012;Suojala et al, 2013;Beuron et al, 2014;da Costa Krewer et al, 2015).…”