Temporal profile of antimicrobial resistance exhibited by strains of Staphylococcus spp. isolated from cases of bovine mastitis for 20 years (1992-2011)

Abstract

Records of in vitro susceptibility tests performed between 1992 and 2011 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

Classification of dairy properties according to the geometric mean of the somatic cell count and its antimicrobial resistance profile

“…The high rate of resistance of the isolates to beta-lactam antibiotics can be explained by the routine use of these drugs for the treatment of bovine mastitis for many years (Kowalski et al, 2015). The incorrect and indiscriminate use of antimicrobials represents dangers to human and animal health resulting from therapeutic failures with increased rates of bacterial resistance (Costa et al, 2013).…”

<b>Estudo da diversidade molecular de linhagens de <i>Staphylococcus aureus</i> de isolados de mastite bovina</b>

“…Varia com a distribuição geográfica, mas alta incidência de resistência a penicilinas naturais ou semissintéticas, frequentemente utilizadas no tratamento da mastite, está sempre presente (OLIVER;MURINDA, 2012;RUEGG et al, 2015;THOMAS et al, 2015;WANG et al, 2015;BEN SAID et al, 2016;MEHMETI et al, 2016). (KOWALSKI et al, 2015) e no caso dos EUA 9 anos (LINDEMAN et al, 2013). Mas de acordo com Kowalski et al (2015) foi possível perceber diminuição estatística da resistência a penicilinas ao longo do tempo para Staphylococcus spp.…”

“…(KOWALSKI et al, 2015) e no caso dos EUA 9 anos (LINDEMAN et al, 2013). Mas de acordo com Kowalski et al (2015) foi possível perceber diminuição estatística da resistência a penicilinas ao longo do tempo para Staphylococcus spp.…”