In intensive dairy farming, persistent intramammary infection has been associated with specific Staphylococcus (S.) aureus strains, and these strains may be resistant to antimicrobials. The objective of this study was to evaluate the antimicrobial resistance phenotypes of S. aureus isolates and to assess the distribution and the persistence of clonal groups in small dairy herds of southern Brazil. Milk samples were collected from all lactating cows from 21 dairy farms over a two-year period, totaling 1,060 samples. S. aureus isolates were tested for susceptibility to thirteen antimicrobials using the disk diffusion method. The total DNA of the isolates was subjected to SmaI digestion followed by pulsed-field gel electrophoresis (PFGE). Banding patterns differing by ≤4 bands were considered members of a single PFGE cluster. The frequency of S. aureus isolation ranged from 3.45% to 70.59% among the 17 S. aureus-positive herds. Most S. aureus isolates (87.1%) were susceptible to all antimicrobials; resistance to penicillin (18.2%) was the most frequently observed. The 122 isolates subjected to macrorestriction analysis were classified into 30 PFGE-clusters. Among them, only 10 clusters were intermittent or persistent over the two-year period. The majority (93.6%) of isolates belonging to persistent and intermittent clusters were susceptible to all tested antimicrobials. S. aureus intramammary colonization in small dairy farms of southern Brazil is most frequently caused by sporadic PFGE clusters, although some persistent clusters can arise over time. Both sporadic and persistent isolates were highly susceptible to antimicrobials.

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Brazil currently ranks as one of the world leaders in food production and exportation. This scenario encourages the development of animal and plant health programs to ensure the production of safe food, helping the country to become an international provider of food for excellence. However, some health problems in dairy production, such as mastitis, have garnered increasing concern. This study aimed to estimate the prevalence of bovine mastitis in select properties located in the western Santa Catarina region, to assess the susceptibility profile to antimicrobial agents used for treatment and to check for the presence of genes (icaA and icaD) associated with biofilm formation in Staphylococcus aureus. In 148 milk samples collected, 72.97% had bacterial growth (n = 108). Among the isolated microorganisms, 21.62% (n = 32) were classified as Staphylococcus aureus, 18.91% (n = 28) as Staphylococcus sp. coagulase negative, 7.43% (n = 11) as Corynebacterium sp., 6.76% (n = 10) as Staphylococcus sp. coagulase positive, 5.41% (n = 8) as Nocardia sp. and 12.83% (n = 19) classified in different bacterial genera. Among the isolates submitted for antimicrobial susceptibility testing, it was observed that 8.95% (n = 6/67) had resistance to amoxicillin, 8.04% (n = 7/87) to ampicillin, 5.88% (n = 5/85) to cephalothin, 3.40% (n = 3/88) to ceftiofur and enrofloxacin, 20.45% (n = 18/88) to streptomycin, 17.04% (n = 15/88) to gentamicin and lincomycin, 31.81% (n = 28/88) to neomycin, 14.94% (n = 13/87) to penicillin and 25% (n = 22/88) to tetracycline. Staphylococcus sp. coagulase negative isolates showed higher multidrug resistance when compared to those of S. aureus and Staphylococcus sp. coagulase positive. Thirty-one strains of S. aureus isolates were genotypically tested by polymerase chain reaction (PCR), yielding a positive result for the icaA gene in 83.87% of the samples, 80.64% positive for icaD and 74.19% of these showed both genes. The results reinforce the importance of controlling this disease by adopting strict hygiene protocols and disinfection of equipment used for milking and the prescription of appropriate therapies to clinical and subclinical cases of mastitis, as well as evaluating not only the susceptibility profile of isolates but also the biofilm formation capacity. ResumoO Brasil situa-se hoje como um dos líderes mundiais em produção e exportação de alimentos. Este cenário incita a elaboração de programas de sanidade animal e vegetal que garantam a produção de alimentos seguros, contribuindo para que o país se torne um fornecedor internacional de alimentos por excelência. Entretanto, alguns problemas sanitários na produção leiteira, como a mastite, têm acarretado crescentes preocupações. O presente estudo teve como objetivo estimar a prevalência de mastite bovina em algumas propriedades localizadas na região Oeste de Santa Catarina, avaliar o perfil de suscetibilidade aos antimicrobianos empregados para tratamento e verificar a presença de genes (icaA e icaD) associados à formação de biofilmes em ...

Objective. To assess the microbiological profile in seven Boar Studs (BS) in Southern Brazil, as well as evaluate antimicrobial susceptibility response to most commonly found microorganisms in BS. Materials and methods. Bacteriologic analysis was carried out in samples from the water purification system, semen extender, raw and stored semen, lab benches, and other working surfaces. Results. Growth of a mixed bacterial population was observed in water samples from all but one BS. Approximately 85% of the BS had significant contamination on their working surfaces with at least one bacterial contaminant. A total of 86% of raw semen samples were contaminated with one or more different bacteria, while 100% of the boar studs provided contaminated samples. Bacterial susceptibility to antimicrobial agents varied from over 80% for gentamycin, neomycin and ceftiofur to 40% or less for penicillin and lincomycin. Conclusions. The identification of the critical points provides necessary support to devise better strategies to minimize contamination in BS. Also, assessing the level of antimicrobial drug resistance offers accurate information to formulate more efficient antibacterial protocols that closely observe the rational use of antibiotics.Keywords: Boar semen; bacterial contamination; antimicrobial susceptibility (Source: DeSC, CAB). RESUMENObjectivo. Evaluar el perfil microbiológico de siete centros de recogida de semen porcino (BS) en el sur de Brasil, así como evaluar la susceptibilidad antimicrobiana a la mayoría de los microorganismos encontrados en los BS. Materiales y métodos. El análisis bacteriológico se realizó en muestras del sistema de purificación de agua, diluyentes de semen, semen crudo y almacenado, bancos de laboratorio y otras superficies de trabajo. Resultados. El crecimiento de una población bacteriana mixta se observó en muestras de agua de todas las BS excepto una. Aproximadamente el 85% de la BS tenía contaminación significativa en sus superficies de trabajo con al menos un contaminante bacteriano. Un total de 86% de muestras de semen crudo fueron contaminadas con una o más bacterias diferentes, mientras que el 100% de BS proporcionaron muestras contaminadas. La susceptibilidad Bacterial Contaminants and Antimicrobial Susceptibility Profile of Boar Semen in Southern Brazil StudsContaminantes bacterianos y perfil de susceptibilidad del semen porcino en centros de recogida em Brasil

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