João Batista Ribeiro

Presence of mecA-positive multidrug-resistant Staphylococcus epidermidis in bovine milk samples in Brazil

Bacteria of the genus Staphylococcus are one of the major pathogens causing bovine mastitis. In recent decades, resistance of this genus to oxacillin (methicillin) has been a matter of concern due to the possibility of reducing the effectiveness of mastitis treatments and the transfer of resistance determinants to other bacteria. Oxacillin resistance was studied in 170 staphylococci from bovine milk samples, including 79 Staphylococcus aureus and 91 coagulase-negative staphylococci (CNS). The susceptibility profile of 10 antimicrobial agents used in veterinary practice was determined by the Etest method. In addition to the Etest, the phenotypic characterization of oxacillin resistance was tested using the cefoxitin disk diffusion test. All isolates were screened by PCR to detect the mecA gene in 2 different regions of the gene. The isolates with an oxacillin minimum inhibitory concentration ≥0.5 µg/mL or resistant to cefoxitin were identified by sequencing a 536-bp fragment of the 16S rRNA gene. This group of isolates was also evaluated for the presence of blaZ and mecC genes. Molecular analysis of the mecA gene was carried out by typing of the staphylococcal cassette chromosome mec (SCCmec). The relatedness of the mecA-positive isolates was evaluated by macrorestriction of chromosomal DNA followed by pulsed-field gel electrophoresis. With the exception of penicillin and oxacillin, 86% of the isolates showed susceptibility to cephalothin, gentamicin, erythromycin, sulfonamide, trimethoprim-sulfamethoxazole, and tetracycline. All S. aureus isolates were susceptible to oxacillin, whereas 47% (n=43) of the CNS isolates were resistant. The CNS isolates showed a higher resistance to cephalothin, erythromycin, tetracycline, and gentamicin in comparison with S. aureus. The mecA gene was only detected in 10 CNS isolates, identified as Staphylococcus epidermidis, and classified into 3 pulsotypes (A, B, and C) and 4 subtypes (A1, B1, B2, and B3). Among the isolates with an oxacillin resistance phenotype, 12 were positive for the blaZ gene, and 9 of them were mecA-positive. Two of the oxacillin-resistant isolates amplified the mecA homolog gene of Staphylococcus sciuri and none amplified mecC. Three SCCmec types, I, IV, and V, were found. Our results suggest that Staphylococcus epidermidis can be a reservoir for mecA for other Staphylococcus species. Studies investigating the molecular and phenotypic profile of antimicrobial resistance in staphylococcal species should be performed for controlling the spread of resistance and the selection of appropriate therapeutic measures.

Estimate of the economic impact of mastitis: A case study in a Holstein dairy herd under tropical conditions

The aim of this study was to estimate the economic impact of mastitis at the herd level and the weight (percent) of the components of this impact in a Holstein dairy herd under tropical conditions. Three estimates of the economic impact of mastitis were performed. In estimates 1 and 2 the real production and economic indices from February 2011 to January 2012 were considered. In the estimate 1, indices for mastitis classified as ideal were considered, whereas in the estimate 2, the mastitis indices used were those recorded at the farm and at Holstein Cattle Association of Minas Gerais State database (real indices). Ideal mastitis indices were bulk milk somatic cell counts less than 250,000 cells/mL, incidence of clinical mastitis less than 25 cases/100 cows/year, number of culls due to udder health problems less than 5% and the percentage of cows with somatic cell counts greater than 200,000 cells/mL less than 20%. Considering the ideal indices of mastitis, the economic impact was US

Characterisation of penicillin and tetracycline resistance in Staphylococcus aureus isolated from bovine milk samples in Minas Gerais, Brazil

19,132.35. The three main components of the economic impact were culling cows (39.4%) and the reduction in milk production due to subclinical and clinical mastitis (32.3% and 18.2%, respectively). Estimate 2 using real mastitis indices showed an economic impact of US

Prevalence Reduction of Contagious Mastitis Pathogens in a Holstein Dairy Herd Under Tropical Conditions

61,623.13 and the reduction in milk production due to mastitis (77.7%) and milk disposal (14.0%) were the most relevant components. The real impact of culling cows was approximately 16 times less than the weight that was considered ideal, indicating that this procedure could have been more frequently adopted. The reduction in milk production was 27.2% higher than the reduction in Estimate 1, indicating a need to control and prevent mastitis. The estimate 3 considered the same indices as estimate 2, but for the period from February 2012 to January 2013. Its economic impact was US

Naproxen Cocrystals with Pyridinecarboxamide Isomers

91,552.69. During this period, 161 treatments of cows with an intramammary antibiotic were performed to eliminate Streptococcus agalactiae, and eight cows chronically infected with Staphylococcus aureus were culled. The reduction in milk production due to mastitis was the main component of the economic impact (54.9%). The culling of cows with chronic infection was associated with an increase in the economic impact of mastitis and a reduction in the average productivity per cow. At the herd level reduction in milk production was the component that presented the largest weight in the economic impact of the disease.

Overexpression of the plg1 gene encoding pectin lyase in Penicillium griseoroseum

This Regional Research Communication describes the characterisation of ampicillin, penicillin and tetracycline resistance in Staphylococcus aureus isolated from bovine subclinical mastitis in Minas Gerais State, Brazil. Ninety S. aureus isolates from bovine mastitis exhibiting phenotypic resistance to ampicillin, penicillin and/or tetracycline were selected for this study. The minimum inhibitory concentration (MIC) of each antibiotic was determined using the E-Test® and the production of beta-lactamase was determined by cefinase disks. The resistance genes blaZ, tet(K), tet(L), tet(M), and tet(O) were investigated by PCR in all of the isolates. The MIC results classified 77, 83 and 71% of the isolates as resistant to ampicillin, penicillin and tetracycline, respectively. The MIC50 and MIC90 were, respectively, 1 and 2 µg/ml for ampicillin, 0·5 and 1 µg/ml for penicillin and 32 and 64 µg/ml for tetracycline. Eighty-six per cent of beta-lactamase producing isolates were detected. Of the 90 isolates investigated, 97% amplified blaZ, 84% amplified tet(K), 9% amplified tet(L), 2% amplified tet(M) and 1% amplified tet(O). Seventy-nine isolates (88%) showed blaZ together with at least one tet gene. S. aureus isolates showed high MIC50 and MIC90 values for the three antimicrobials. The blaZ and tet(K) genes were widespread in the herds studied, and most of the isolates harboured blaZ and tet(K) concomitantly.

Genotypic and phenotypic detection of capsular polysaccharide and biofilm formation in Staphylococcus aureus isolated from bovine milk collected from Brazilian dairy farms

The aim of this study was to evaluate the reduction of intramammary infection caused by Streptococcus agalactiae and Staphylococcus aureus in a Holstein dairy herd under tropical conditions. The period of study was from January 2012 from January 2013 in a dairy herd composed by Holstein cows, with an average of 142 lactating cows/month. Milk samples were collected from individual lactating cows for microbiological tests. The sampling lactating cows was in order to identify those infected by Streptococcus agalactiae for the treatment of all mammary quarters with intramammary antibiotics, as well as to identify chronically infected lactating cows by S. aureus for possible culling. During this period, 161 treatments of cows with an intramammary antibiotic were performed to eliminate Streptococcus agalactiae, and nine cows chronically infected with Staphylococcus aureus were culled. The percentages of infected cows with S. agalactiae in January 2012 and January 2013 were 61.6% and 2.2%, respectively. For the same months, the percentages of cows infected with S. aureus were 28.3% and 19.4%, respectively. The intramammary antibiotic treatment of lactating cows was efficient in eliminating infection caused by S. agalactiae and consequently the prevalence of infected animals in the herd. The reduction in S. aureus prevalence among cows was associated with the culling of cows chronically infected by this pathogen.