Produção de hemolisinas por Staphylococcus aureus isolados de casos de mastite bovina subclínica / Production of hemolysins by Staphylococcus aureus isolated from bovine subclinical mastitis

Com o objetivo de avaliar a produção das hemolisinas alfa, beta e delta, foram analisadas 78 amostras de Staphylococcus aureusisoladas de casos de mastite bovinasubclínica. Em ágar sangue de ovino e/ouequino,100% das amostras apresentaram atividade hemolítica, com 58 amostras produzindo a toxina alfa; 73 a delta e 76 a beta, correspondendo a 74,4, 93,6 e 97,4% das amostras, respectivamente. A análise da produção combinada mostrou que em 70,5% das amostras houve co-produção de alfa+beta+delta; em 20,5% beta+delta; em 2,6% alfa+beta; e em 1,3% alfa+delta. A produção de um único tipo de toxina foi observada em apenas quatro amostras, sendo três (3,8%) produtoras datoxina beta e uma (1,3%) amostra da toxina delta. A mensuração do diâmetro dos halos hemolíticos indicou produção de uma grande quantidade de toxina. Além disso, a maioria das amostras (70,5%) demonstrou atividade hemolítica às 24 horas de incubação. Estes resultados demonstraram que vacas com mastite subclínica são um importante reservatório de Staphylococcus aureuscom habilidade de produzir hemolisinas.

Alpha, beta and delta hemolysins were evaluated in 78 samples of Staphylococcus aureusisolated from bovine subclinical mastitis. On sheep and/or horse blood agar,100% of the isolates produced hemolytic activity and 58 were positive for alfa-toxin; 73 for delta-toxin and 76 for beta-toxin, which accounted for 74.4, 93.6 and 97.4% of the isolates, respectively. The production of alpha+beta+deltatoxins was observed in 70.5% of the isolates; beta+deltain 20.5%; alpha+betain 2.6%; and alpha+deltain 1.3%. Four isolates produced one toxin type alone with three (3.8%) of them producing beta-toxin and one (1.3%) delta-toxin. The measurementof the hemolytic area showed a high amount of toxin production. Also, the majority of isolates (70.5%) produced hemolysis at 24 hours after incubation. Theseresultsdemonstrated thatcows with a subclinical mastitis are an important reservoir of hemolytic Staphylococcus aureus.

Neuromuscular activity of Bothrops neuwiedi pauloensis snake venom in mouse nerve-muscle preparations

The pharmacological effects of Bothrops neuwiedi pauloensis venom on mouse phrenic nerve-diaphragm (PND) preparations were studied. Venom (20 mug/ml) irreversibly inhibited indirectly evoked twitches in PND preparations (60 ± 10 percent inhibition, mean ± SEM; p<0.05; n=6). At 50 mug/ml, the venom blocked indirectly and directly (curarized preparations) evoked twitches in mouse hemidiaphragms. In the absence of Ca2+, venom (50 mug/ml), produced partial blockade only after an 80 min incubation, which reached 40.3 ± 7.8 percent (p<0.05; n=3) after 120 min. Venom (20 mug/ml) increased (25 ± 2 percent, p< 0.05) the frequency of giant miniature end-plate potentials in 9 of 10 end-plates after 30 min and the number of miniature end-plate potentials which was maximum (562 ± 3 percent, p<0.05) after 120 min. During the same period, the resting membrane potential decreased from - 81 ± 1.4 mV to - 41.3 ± 3.6 mV 24 fibers; p<0.01; n=4) in the end-plate region and from - 77.4 ± 1.4 to -44.6 ± 3.9 mV (24 fibers; p<0.01; n=4) in regions distant from the end-plate. These results indicate that B. n. pauloensis venom acts primarily at presynaptic sites. They also suggest that enzymatic activity may be involved in this pharmacological action.(AU)