RESUMO
Coagulase-negative staphylococci (CNS) are the most frequently isolated bacteria in cases of subclinical mastitis in dairy cows. CNS species may differ in their pathogenicity, but very little is known about their virulence factors or their immune response in intramammary infections. To our knowledge, no experimental studies into the mastitis pathogenesis caused by CNS have been described in lactating goats. The aim of this study was to induce an experimentally Staphylococcus chromogenes mastitis in lactating goats aimed at verifying if the model can be used to evaluate the inflammatory response, the dynamics of infection and the pathological findings within the first hours of intramammary inoculation. Six Saanen goats in mid-lactation were inoculated with 1â¯×â¯107 colony forming units of S. chromogenes. Bacterial growth peaked in milk from the challenged right halves of the mammary glands (RMG) at 4â¯h post inoculation (PI). Shedding of viable bacteria showed a marked decrease at 12â¯h PI. An increase in mean somatic cell counts was observed in the milk samples from 8â¯h PI onwards. Mild clinical signs were evoked by intramammary inoculation. Staphylococcus chromogenes could be isolated in tissue from all RMG. Histological examination of specimens of the RMG and lymph nodes of the goats showed an increased inflammatory response throughout the experiment with respect to control halves. In conclusion, the experimental inoculation of S. chromogenes in lactating goats is capable of eliciting an inflammatory response and capable of causing pathological changes. This research represents a preliminary study for a better knowledge of the mastitis pathogenesis caused by S. chromogenes.
Assuntos
Cabras , Mastite/patologia , Infecções Estafilocócicas/patologia , Staphylococcus/patogenicidade , Animais , Derrame de Bactérias , Modelos Animais de Doenças , Humanos , Linfonodos/patologia , Glândulas Mamárias Humanas/patologia , Mastite/microbiologia , Leite/microbiologia , Infecções Estafilocócicas/microbiologia , Fatores de TempoRESUMO
The modified rotating simplex method has been successfully used to determine the best combination of agitation rate and aeration rate for maximum production of extracellular proteases by Staphylococcus aureus mutant RC128, in a stirred tank bioreactor operated in a discontinuous way. This mutant has shown altered exoprotein production, specially enhanced protease production. Maximum production of proteases (15.28 UP/ml), measured using azocasein as a substrate, was obtained at exponential growth phase when the bioreactor was operated at 300 rpm and at 2 vvm with a volumetric oxygen transfer coefficient (K(L)a) of 175.75 h(-1). These conditions were found to be more suitable for protease production.
Assuntos
Reatores Biológicos , Mutação , Staphylococcus aureus/genética , Biotecnologia/métodos , Calibragem , Caseínas/química , Meios de Cultura/química , Fermentação , Concentração de Íons de Hidrogênio , Microbiologia Industrial/instrumentação , Microbiologia Industrial/métodos , Modelos Estatísticos , Oxigênio/química , Peptídeo Hidrolases/química , Staphylococcus aureus/metabolismo , Temperatura , Fatores de TempoRESUMO
A vaccine against bovine mastitis was developed. The vaccine was based on inactivated, highly encapsulated Staphylococcus aureus cells; a crude extract of Staph. aureus exopolysaccharides; and inactivated unencapsulated Staph. aureus and Streptococcus spp. cells. In this study, the vaccine was evaluated in 164 cows from two commercial dairies (A and B) during a 4-mo period. Two doses of the vaccine were administered subcutaneously to 82 cows in the brachiocephalicus muscle of the neck within a 4-wk interval. The results of this trial revealed significantly fewer intramammary infections caused by Staph. aureus at various levels of severity (clinical, subclinical, and latent) in cows that were vaccinated. The odds ratios of all types of intrammammary infections caused by Staph. aureus for dairies A and B, which were determined by a logistic model, were 1.84 and 1.89, respectively, for quarters of vaccinated cows and quarters of control cows. The colony counts for Staph. aureus in milk from infected quarters of vaccinated cows were significantly lower than those in milk from infected quarters of control cows. Also, the somatic cell counts per milliliter in milk from vaccinated cows were significantly decreased when the initial somatic cell count was < 500,000 cells/ml at the start of the trial. The vaccine had no observable effect on fat production in milk or on streptococcal infections.
Assuntos
Vacinas Bacterianas , Mastite Bovina/prevenção & controle , Animais , Argentina , Bovinos , Contagem de Células , Feminino , Mastite Bovina/microbiologia , Leite/citologia , Razão de Chances , Infecções Estafilocócicas/prevenção & controle , Staphylococcus aureus/imunologia , Infecções Estreptocócicas/prevenção & controle , Streptococcus/imunologiaRESUMO
A Tn551 insertional pleiotropic mutant defective in the production of several exoproteins was isolated from Staphylococcus aureus 196E and characterized. The pleiotropism of the mutant was due to a single insertion of the transposon as evidenced by Southern blot hybridization and by the transfer of its phenotype by transduction to S. aureus ISP479. The mutants showed diminished or null levels of alpha- and beta-hemolysis, DNase, coagulase, and protein A in the supernatants of broth cultures. Production of proteases, lipase, staphylokinase, or enterotoxin A was not modified. The mutants did synthesize the cell-bound form of protein A and also the extracellular form of this protein coded by pRIT11, which lacks the COOH-terminal segment of the molecule. These observations suggest that the sae locus does not involve a positive regulatory gene acting at the transcriptional level. The phenotype of the mutant was different from that of other insertional mutants affecting exoprotein synthesis, such as agr, xpr, or sar. This new mutation has been designated sae (for S. aureus exoprotein expression).