Staphylococcus aureus is one of the most frequent mastitis causative agents in small ruminants. The expression of most virulence genes of S. aureus is controlled by an accessory gene regulator (agr) locus. This study aimed to ascertain the prevalence of the different agr groups and to evaluate the occurrence of encoding genes for cytotoxin, adhesins and toxins with superantigen activity in S. aureus isolates from milk of ewes with clinical and subclinical mastitis in sheep flocks raised for meat production The agr groups I and II were identified in both cases of clinical and subclinical mastitis. Neither the arg groups III and IV nor negative agr were found. The presence of cflA gene was identified in 100% of the isolates. The frequency of hla and lukE-D genes was high - 77.3 and 82.8%, respectively and all isolates from clinical mastitis presented these genes. The sec gene, either associated to tst gene or not, was identified only in isolates from subclinical mastitis. None of the following genes were identified: bbp, ebpS, cna, fnbB, icaA, icaD, bap, hlg, lukM-lukF-PV and se-a-b-d-e.
Este trabalho teve por objetivo estudar os efeitos da acidose láctica ruminal, induzida experimentalmente em caprinos, sobre o quadro clínico, as características físico-químicas e microbiológicas do fluido ruminal. Para tal, foram utilizados dez animais, sem raça definida (SRD), com peso médio de 25 kg, machos, com um a dois anos de idade, fistulados, clinicamente sadios e mantidos em baias. Após se estabelecer os padrões de normalidade para as variáveis estudadas, os animais foram induzidos experimentalmente a ter a acidose ruminal empregando-se a sacarose, na dose de 15 g/kg de peso corporal. As observações clínicas e laboratoriais foram realizadas nos intervalos de 4, 8, 12, 16, 24, 32, 48, 72, 96, 120 e 144 horas, após a indução (PI) onde se avaliou a intensidade do processo da acidose láctica ruminal. Os caprinos estudados apresentaram manifestações clínicas de acidose láctica ruminal já a partir das 4 horas PI, cujos sinais como apatia, anorexia, taquicardia, atonia ruminal, distensão abdominal e diarréia de intensidade variável foram observados. As características do suco ruminal sofreram alterações, ocorreu a redução do pH para valores inferiores a 5, a cor tornou-se leitosa, o odor ácido e a consistência aquosa. O tempo de atividade de sedimentação (TAS) reduziu seus valores, e a dinâmica da fauna e flora ficaram comprometidas, havendo um predomínio da microbiota Gram-positiva. Ao término do período de observação constatou-se que em alguns animais não ocorreu o restabelecimento pleno das variáveis analisadas.
Staphylococcus aureus is one of the most important infectious mastitis causative agents in small ruminants. In order to know the distribution of Staph. aureus strains associated with infectious mastitis in flocks of sheep in the northeast of Brazil and establish whether these clones are related to the strains distributed internationally, this study analysed the genetic diversity of Staph. aureus isolates from cases of clinical and subclinical mastitis in ewes by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing (MLST). In this research, 135 ewes with mastitis from 31 sheep flocks distributed in 15 districts were examined. Staph. aureus was isolated from sheep milk in 9 (29%) out of 31 herds located in 47% of the districts surveyed. MLST analysis allowed the identification of four STs (ST750, ST1728, ST1729 and ST1730). The last three with their respective novel alleles (glp-220; pta-182 and yqil-180) were recently reported in the Staph. aureus MLST database (http://www.mlst.net). Each novel allele showed only a nucleotide different from those already described. The occurrence of CC133 (ST750 and ST1729) in this study is in agreement with other reports that only a few clones of Staph. aureus seem to be responsible for most cases of mastitis in dairy farms and that some of these clones may have broad geographic distribution. However, the prevalence of CC5 (ST1728 and ST1730)--an important group related to cases of colonization or infection in humans--differs from previous studies by its widespread occurrence and may suggest human contamination followed by selective pressures of the allelic diversifications presented for these STs.
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