Temporal profile of antimicrobial resistance exhibited by strains of Staphylococcus spp. isolated from cases of bovine mastitis for 20 years

• Published in: Ciência rural p. 1035
• Main Authors: Kowalski, Ananda Paula, Maboni, Grazieli, Espindola, Julia Pires, Foletto, Ariane, Bandeira, Jr., Guerino, Potter, Luciana, Botton, Sonia de Avila, de Vargas, Agueda Castagna
• Format: Journal Article
• Language: Spanish
• Published: Universidade Federal de Santa Maria 01-06-2015
• Subjects: Brasil
• ISSN: 0103-8478
• DOI: 10.1590/0103-847Sicr20140928

Records of in vitro susceptibility tests performed between 1992 and 20H were retrospectively reviewed in order to evaluate the dynamic profiles of possible changes in antimicrobial resistance of Staphylococcus spp. isolated from milk samples of cows with mastitis during two decades. The results of 2,430 isolates tested by disk diffusion technique for susceptibility to oxacillin, penicillin, ampicillin, cephalexin, norfloxacin, tetracycline, sulfazotrim, gentamicin, and neomycin were analysed. Comparisons were performed between the percentages of resistance to antimicrobials and their classes and also between the decades studied. Additionally, the possible tendency or changes in the behaviour of these pathogens against the major drugs used in the last two decades were evaluated using regression analysis. The highest rates of resistance (P<0.0001) were observed for the beta-lactams (34.3%), with exception of cephalexin (6.9%), and for the tetracyclines (28%). Similar resistance rates (7.6% to 15.7%) were observed among the other drugs. Regression analysis showed a reduction in resistance to penicillin and ampicillin throughout the period, whilst for oxacillin and neomycin a decrease in the resistance was observed during the first decade, followed by an increase. A trend towards decreased resistance was found for sulfazotrim, whereas for the other antimicrobials no decrease was observed. The results indicated no trend towards increased resistance for most antimicrobials tested. Nevertheless, it is necessary to monitor the resistance patterns of these pathogens in order to save these drugs as a therapeutic reserve. Key words: cows, milk, Staphylococcus spp., susceptibility, surveillance. Os registros de resultados de testes de suscetibilidade in vitro realizados no periodo de 1992 a 2011 foram revisados, retrospectivamente, a fim de avaliar a dinamica de possiveis mudancas dos perfis de resistencia de isolados de Staphylococcus spp., oriundos de amostras de leite de vacas com mastite ao longo do tempo. Os resultados de 2430 isolados testados pela tecnica de difusao em disco para oxacilina, penicilina, ampicilina, cefalexina, norfloxacina, tetraciclina, sulfazotrim, gentamicina e neomicina foram analisados. Comparacoes entre as medias de resistencia para os antimicrobianos e suas respectivas classes e em relacao ao periodo analisado foram estabelecidas. O comportamento da resistencia para cada antimicrobiano foi avaliado por meio de analise de regressao. As maiores taxas de resistencia (P<0,0001) foram observadas para os betalactamicos (34,3%), com excecao da cefalexina (6,9%), e tetraciclina (28%). Frente aos demais farmacos, os isolados apresentaram medias de resistencia semelhantes entre si (de 7,6% a 15,7%). A analise de regressao demonstrou reducao da resistencia para penicilina e ampicilina ao longo do periodo analisado. Para a oxacilina e a neomicina, houve um decrescimo da resistencia dos micro-organismos testados durante a primeira decada; entretanto, houve um aumento no segundo periodo. Em relacao ao sulfazotrim, foi verificada uma tendencia a diminuicao da resistencia dos isolados, ao passo que, para os demais antimicrobianos, nenhum comportamento foi destacado. Os resultados nao indicaram tendencia de aumento da resistencia dos isolados de Staphylococcus spp. para a maioria dos antimicrobianos testados. Contudo, e necessario monitorar os padroes de resistencia destes patogenos, afim de que estes farmacos sejam preservados para garantir uma reserva terapeutica. Palavras-chave: vacas, leite, Staphylococcus spp., suscetibilidade, vigilancia.