Open AccessIn vitro antimicrobial susceptibility and genetic resistance determinants of Streptococcus agalactiae isolated from mastitic cows in Brazilian dairy herds
Author(s) -
Juliana Rosa da Silva,
Glei dos Anjos de Carvalho Castro,
Maysa Serpa Gonçalves,
Dircéia Aparecida da Costa Custódio,
Gláucia Frasnelli Mian,
Geraldo Márcio da Costa
Publication year - 2017
Publication title -
semina. ciências agrárias
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.268
H-Index - 25
eISSN - 1679-0359
pISSN - 1676-546X
DOI - 10.5433/1679-0359.2017v38n4supl1p2581
Subject(s) - clindamycin , streptococcus agalactiae , ceftiofur , penicillin , tetracycline , gentamicin , amikacin , microbiology and biotechnology , biology , antibiotic resistance , cefalotin , mastitis , antimicrobial , erythromycin , antibiotics , streptococcus , bacteria , genetics
Streptococcus agalactiae is one of the main causative agents of bovine mastitis and is associated with several economic losses for producers. Few studies have evaluated antimicrobial susceptibility and the prevalence of genetic resistance determinants among isolates of this bacterium from Brazilian dairy cattle. This work aimed to evaluate the frequency of the antimicrobial resistance genes ermA, ermB, mefA, tetO, tetM, aphA3, and aad-6, and in vitro susceptibility to the antimicrobials amikacin, erythromycin, clindamycin, tetracycline, gentamicin, penicillin, ceftiofur, and cefalotin, and the associations between resistance genotypes and phenotypes among 118 S. agalactiae isolates obtained from mastitic cows in Brazilian dairy herds. Of the resistance genes examined, ermB was found in 19 isolates (16.1%), tetO in 23 (19.5%), and tetM in 24 (20.3%). The genes ermA, mefA, aphA3, and aad-6 were not identified. There was an association between the presence of genes ermB, tetM, and tetO and phenotypic resistance to erythromycin, clindamycin, and tetracycline. Rates of resistance to the tested antibiotics varied, as follows: erythromycin (19.5%), tetracycline (35.6%), gentamicin (9.3%), clindamycin (20.3%), penicillin (3.4%), and amikacin (38.1%); conversely, all isolates were susceptible to ceftiofur and cefalotin. Antimicrobial resistance testing facilitates the treatment decision process, allowing the most judicious choice of antibiotics. Moreover, it enables regional and temporal monitoring of the resistance dynamics of this pathogen of high importance to human and animal health