Dinâmica da infecção e caracterização molecular das mastites causadas por Staphylococcus spp. em ovelhas da raça Santa Inês

Abstract

The present work traced the epidemiological profile of intramammary infections (IMI) caused by staphylococci in Santa Inês sheep using molecular biology tools covering the following aspects: 1) to investigate the incidence of intramammary infection (IMI) in meat ewes in the post-partum and the persistence of infection during lactation, and its effect on lamb growth. In this study, 38 ewes and 44 lambs were followed from birth until weaning at 90 days. The lambs were weighed at birth and every 15 days, and the microbiological examination and identification of Mycoplasma agalactiae by polymerase chain reaction (PCR) of the sheep's milk samples were performed at respective times. It was observed that 14 (36.8%; 5 by Mycoplasma agalactiae; 5 by Staphylococcus sciuri, 2 by Staphylococcus aureus and 2 by Staphylococcus simulans) and 20 (31.6%) sheep present persistent and transient IIM, respectively. Therefore, 63.26% of IMIs, all due to non-aureus staphylococci, did not persist during lactation, suggesting opportunistic profiles of some species. The survival rate of lambs from sheep with persistent IMI (33.3%) was much lower than healthy animals (100%) or with transient IMI (91.7%). In addition, there was a difference in weight gain for lambs from sheep persistently infected at 90 days in relation to the other groups. Despite the negative impact of mastitis on Santa Inês sheep on lamb performance and death, the etiologic agent and its potential to cause persistent IMI should be considered. 2) to report a sporadic case of gangrenous mastitis caused by multi-resistant Staphylococcus haemolyticus in Santa Inês sheep. The microbiological examination, the antimicrobial resistance profile and the presence of virulence factors were investigated. Staphylococcus haemolyticus isolates showed multidrug resistance to antimicrobials and were positive for two staphylococcal enterotoxygenic genes and fibronectin-binding protein (fnbA). 3) investigate whether the staphylococci isolated from clinical and subclinical mastitis, from apex of sheep and lambs' tonsils are genetically distinct, and have genes related to the production of enterotoxins and resistance to methicillin and penicillin. 78 staphylococcus isolates from Santa Inês sheep were used (Study 1). Staphylococcus isolates were identified by MALDI-TOF MS, and PCR was performed to identify the virulence and antimicrobial resistance genes. In addition, the isolates were genotyped by random amplification of polymorphic DNA (RAPD). It was observed that S. aureus isolated from milk samples differ from those isolated from extra-mammary niches, differently from non-aureus staphylococcus species. S. aureus hosted most virulence and resistance genes. An isolate of S. aureus and other of Staphylococcus sciuri shown methicillin-resistance. Therefore, the present study provided more detailed information on the epidemiology of staphylococci associated with sheep. 4) to report the presence of Staphylococcus sciuri carrying the methicillin resistance gene mecC, being, therefore, the first report in Brazil. Resistance to cefoxitin and oxacillin was determined by the minimum inhibitory concentration, and the resistance genes were confirmed by PCR, and sequencing of PCR products.