Abstract
ABSTRACT The objective of this study was to evaluate the “in vitro” antimicrobial susceptibility profiles of Staphyloccusspp. and Streptococcus spp. isolated from the milk of cows with infectious mastitis. This study was conducted on 14 dairy farms located in four municipalities on the Island of São Luís, Maranhão, Brazil. The isolates were obtained by bacteriological cultivation of milk samples, followed by morphological and biochemical characterization. Antimicrobial susceptibility tests were performed using the disk diffusion method. The results showed that none of the principles were 100% effective against the isolates. Penicillin, ampicillin, and amoxicillin showed higher rates of resistance in isolates of Coagulase-positive Staphylococcus (80%, 77.2%, and 77.2%, respectively), Coagulase-negative Staphylococcus (80%, 75.4%, and 75.4%, respectively ), and S. aureus (94.3%, 88.6%, and 88.6%, respectively). Isolates of Streptococcus showed a higher frequency of resistance to streptomycin (94%), tetracycline (86%), and lincomycin (76%). Isolates from the Coagulase-negative Staphylococcus group had the highest multidrug resistance profile, with 32.65% of the strains being simultaneously resistant to more than eight antibiotics. A high frequency of isolates of agents that cause bovine mastitis with multidrug-resistant phenotypes was determined, making it necessary to base the treatment of animals on the diagnosis of the causative pathogen and patterns of sensitivity to antimicrobials.
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