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.
Background: Despite a strong association between Salmonella isolation and slaughter hygiene, as measured by the Enterobacteriaceae levels on pre-chill carcass surfaces, a high variation in this association was observed between sampling days within the same slaughterhouse. It was hypothesised that in a scenario of high exposure on the farm, batches with a high prevalence of carrier pigs shedding a high number of Salmonella may enhance the risk of contamination on some slaughter days. Thus, the aim of this study was to assess the profile of Salmonella carried in the intestinal contents of slaughter pigs.Materials, Methods & Results: Ten pig batches slaughtered in a slaughterhouse were investigated for the presence of Salmonella. From each pig, the following samples were taken: i. blood collected at bleeding; ii. sponges rubbed on the carcass surface after bleeding and before chilling; iii. fragment of the ileocecal region of the intestine. Serum samples were subjected to a ELISA-Typhimurium test. Sponges were investigated for the presence of Salmonella and total aerobic mesophilic (TAM) and Enterobacteriaceae (EC) bacterial counts. Salmonella was enumerated in the intestinal contents. Selected Salmonella strains were subjected to an antimicrobial resistance disk diffusion test, macro-restriction with Xba-I (PFGE) and whole genome sequencing (WGS). From the 50 sampled pigs, 96% were positive in the ELISA-Typhimurium test and 64% were Salmonella-positive in the intestinal contents. The amount of Salmonella in the intestinal content samples was highly variable, and the mean log of fitted distributions of Salmonella in the batch ranged from -2.97 to 2.25 cfu.g-1. The slaughter process achieved a logarithmic reduction, ranging from 0.64 to 2.35 log cfu.cm-2 for TAM and from 0.55 to 2.57 log cfu.cm-2 for EC. Salmonella was isolated from 16% of the carcasses after bleeding; this frequency decreased to 8% at the pre-chill step. All positive pre-chill carcasses originated from pigs carrying Salmonella in the intestinal content and from batches with a high number of carrier pigs. Salmonella Typhimurium and its monophasic variant were the most frequent in the intestinal contents and carcasses. Resistance was detected against ampicillin (42.5%), tetracycline (42.5%), sulfonamide (40%), gentamicin (25%) and ciprofloxacin (12.5%). Regarding colistin, 85% of the tested strains were classified as non-susceptible. The monophasic variant S. Typhimurium strains subjected to PFGE and WGS presented different profiles; several antimicrobial resistance genes were identified and all belonged to ST-19.Discussion: In this study, almost all sampled pigs entering the slaughter line had been exposed to Salmonella on the farm and a high number were carrying Salmonella in their guts. While the three batches with Salmonella-positive carcasses at the pre-chill step presented TAM media that was not significantly different from the other batches, there was a higher number of positive pigs carrying Salmonella in their intestinal contents. Moreover, the batch with the highest number of positive carcasses also presented the highest Salmonella mean count in their intestinal contents. The profile of Salmonella carried in the intestinal content of slaughter pigs proved to be highly variable in terms of the frequency, number of bacteria, serovars, antimicrobial resistance, and genotypes. Results indicate that the day-to-day variability in the prevalence and number of Salmonella in the intestinal contents of slaughter batches is likely to influence the frequency of contaminated pre-chill carcasses. Salmonella Typhimurium isolated from the intestinal contents of slaughter pigs may belong to genotypes involved in human disease and may carry several antimicrobial resistance genes. These aspects should be taken into account when planning Salmonella control in swine.
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 ...
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