Background: Milk quality is considered unsatisfactory in Brazil due to factors of a social, economic, cultural, and climatic nature. Mastitis is the main disease that affects dairy herds. Microorganisms of the genus Staphylococcus are the most frequently isolated pathogens in cases of mastitis in bovines. Staphylococcus aureus requires more attention because they have the ability to develop resistance to antimicrobials used in the treatment of mastitis. Thus, the aim of the present study was to evaluate virulence factors in isolates of S. aureus as well as analyze the hygienic-sanitary quality of raw milk produced on dairy farms in a semiarid region of northeastern Brazil.Material, Methods & Results: Samples were taken from milk containers at 44 properties. Fifty-eight isolates of Staphylococcus spp. were analyzed and genotypically identified as S. aureus. In the phenotypic characterization, 56.8% (33/58) of the isolates demonstrated moderate biofilm production. In the genotypic characterization (icaA, icaD and bap genes), icaA was the most representative among the isolates. No resistance to cephalothin or oxacillin was found, but 62% (36/58) of the isolates exhibited resistance to ampicillin, amoxicillin, and penicillin. In the genotypic evaluation in response to β-lactam antibiotics, 50% (29/58) of the isolates exhibited the blaZ gene. Total bacterial counts were determined based on the standard plate count and flow cytometry, for which a significant positive correlation was found (r = 0.61, P < 0.01). The somatic cell count was also performed using flow cytometry and demonstrated that 6.8% (3/44) of the properties had values above one million cells per mL. The analysis of Staphylococcus spp. revealed that 20% (9/44) of the properties had significant counts for the production of staphylococcal enterotoxins. Regarding total coliforms, 56.8% (25/44) of the milk analyzed had counts above 1.0 x 103 CFUs/mL. There were no cases of the isolation of Pseudomonas spp. Streptococcus spp. was isolated on 6.8% (3/44) of the properties. The results of the sequencing revealed one isolate to be Lactococcus lactis and two to be Enterococcus spp.Discussion: None of the 58 isolates of S. aureus was classified as negative in the phenotypic characterization of biofilmforming capacity, which suggests the presence of genes involved in this process. Studies have shown that the molecular techniques used to identify ica genes encoding biofilm synthesis are very important for the identification of virulent strains. The isolates demonstrated resistance to β-lactam antibiotics of the class of penicillins, which are the most widely employed antimicrobial agents for the treatment of diseases in dairy herds. The presence of the blaZ gene in 50% of the isolates is in agreement with data reported in other studies developed in northeastern Brazil. In 50% (29/58) of the isolates, the presence of the blaZ gene was not observed. Of these, (8/29) were resistant to ampicillin, amoxicillin and penicillin. This is due to the existence of other bacterial mechanisms. Research has shown that some isolates possessed three mechanisms (blaZ, mecA and msrA) of antimicrobial resistance simultaneously. The results of the quality analyses demonstrate that some properties produce milk of low quality, which underscores the need for management strategies directed at reducing the contamination of the product.

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Aeromonas hydrophila is a common fish pathogen that causes extensive damage to aquaculture. To develop and implement a more adequate strategy to farm fish, it is crucial to understand the bacterial-resistance levels and their transference dynamics. The objective of this study was to analyze the resistance profile of isolated Aeromonas hydrophila to antimicrobial agents and heavy metals and draw a correlation of the observed profiles with the presence of plasmids. Resistance of the isolated bacteria to antimicrobial agents (oxacilin, gentamicin, tetracycline, and nalidixic acid) and heavy metals (cadmium, lead, copper, and manganese) was verified using the minimum bactericidal concentration (MBC) and minimum inhibitory concentration (MIC) standards. The Multiple Antibiotic Resistance Index (MAR Index) was calculated. Plasmids were extracted by using a common methodology described elsewhere. Mann-Whitney Test, implemented in the R environment, was used to determine the correlation between resistance and plasmids presence. A high resistance to almost all antimicrobial agents and heavy metals was observed, except to gentamicin and cadmium. The MAR index results showed resistance to all antimicrobial profiles. Of the isolated bacteria, 14 showed the presence of plasmids. However, no correlation was noted between the resistance profile and the plasmid presence for these isolates, indicating that the genes responsible for resistance to microbial agents and heavy metals are present in the cromossomic DNA, which in turn suggested the possibility of gene transfer between the isolated bacteria. The resistance to heavy metals can be linked to heavy utilization of fertilizers along the Sao Francisco River.

The aim of the present study was to assess two diagnostic techniques (California mastitis test (CMT) and the somatic cell count (SCC)) that can diagnose mastitis in dairy goats

Mastitis is responsible for both damage to animal health and economic losses to the industry. To identify effective treatments for this disease, products extracted from a variety of plants with antimicrobial potential have gained attention. The present study aimed to assess the in vitro antibacterial potential of the ethanolic extract of two plant species from the Caatinga biome against bacteria isolated from small ruminants with subclinical mastitis. The leaves of Mimosa tenuiflora and Commiphora leptophloeos were dried and processed to obtain crude ethanolic extracts and their phenolic composition was evaluated. In total, 33 Staphylococcus spp. isolates from the bacterial collection of the Laboratory of Food Quality Control of IF SERTÃO-PE were used for evaluation of biofilm production. Furthermore, an antimicrobial susceptibility test was conducted using the minimal bactericidal concentration (MBC) method against the two ethanolic extracts. The toxic potential was measured through a toxicity test with Artemia salina. The quantification of the phenolic compounds revealed that the ethanolic extracts of M. tenuiflora and C. leptophloeos possessed higher amounts of myricetin (43.2 and 294.9 mg in 10 g, respectively) in relation to the other compounds. A 39.4% positivity rate was observed in the nuc gene investigation. The biofilm production analysis revealed that 96.9% of the isolates produced biofilm, evidencing the evolution the microorganisms regarding the development of resistance mechanisms. The MBC results showed an inhibition range between 195.30 and 3125.00 µg mL-1 and between 781.20 and 6250.00 µg mL-1 for the extracts of M. tenuiflora and C. leptophloeos, respectively. The M. tenuiflora extract showed the highest activity, suppressing 100% of the bacterial isolates (n=26), whereas the extract of C. leptophloeos showed an inhibition percentage of 69.23%. The crude ethanolic extract (EEB) of M. tenuiflora was found to be toxic, presenting a DL50 of 118.356 µg mL-1. In contrast, the EEB of C. leptophloeos was found to be non-toxic (DL50 = 1527.430 µg mL-1). In conclusion, both native Caatinga species presented antibacterial activity and myricetin was the major compound. These findings highlight the need for further studies regarding the identification of anti-mastitis products from natural extracts.