Performance of culture media for the isolation and identification of Staphylococcus aureus from bovine mastitis.

Rapid isolation and identification of pathogens is a major goal of diagnostic microbiology. In order to isolate and identify Staphylococcus aureus, a number of authors have used a variety of selective and/or differential culture media. However, to date, there are no reports comparing the efficacy of selective and differential culture media for S. aureus isolation from bovine mastitis cases using the 16S rRNA (rrs) gene sequence as a gold standard test. In the present study, we evaluated the efficacy of four selective and/or differential culture media for the isolation of S. aureus from milk samples collected from cows suffering from bovine mastitis. Four hundred and forty isolates were obtained using salt-mannitol agar (SMA, Bioxon), Staphylococcus-110 agar (S110, Bioxon), CHROMAgar Staph aureus (CSA, BD-BBL) and sheep's blood agar (SBA, BD-BBL). All bacterial isolates were identified by their typical colony morphology in the respective media, by secondary tests (for coagulase and ß-haemolysis) and by partial 16S rRNA (rrs) gene sequencing as a gold standard test. Sensitivity, positive predictive and negative predictive values were higher for SMA (86.96, 52.63 and 95.95%, respectively) compared with S110 (70.00, 23.73 and 90.91%, respectively), CSA (69.23, 28.13 and 95.74%, respectively) and SBA (68.75, 37.93 and 89.58%, respectively) while specificity values were similar for all media. Data indicated that the use of culture media for S. aureus isolation combined with determination of coagulase activity and haemolysis as secondary tests improved accuracy of the identification and was in accordance with rrs gene sequence-analysis compared with the use of the culture media alone.

Seroprevalence of and risk factors for brucellosis of goats in herds of Michoacan, Mexico.

Our objectives were to estimate the seroprevalence of Brucella melitensis, and to identify some risk factors associated with goat seropositivity in Michoacan, Mexico. Blood samples were collected from 5114 animals from 79 herds. Sera were tested for antibodies against B. melitensis using the Rose Bengal plate test and the complement-fixation test. Information regarding the herds and each animal sampled were recorded through a personal interview at the farm. We used random-effects multivariable logistic regression to analyze our data. Fifty-six herds of the 79 tested had at least one seropositive animal. The animal-level true seroprevalence was 9.8% (CI=8.8, 10.7). Animals in large herds (>34 animals), in herds with high stock density (>3.5 animals/m(2)) or animals >24 months old had higher odds of seropositivity (2.0, 1.7 and 1.8, respectively) than those in small herds, in herds with low stock density or animals < or =24 months old.

Management factors associated with Babesia bovis seroprevalence in cattle from eastern Yucatán, Mexico.

The effect of management on the seroprevalence of Babesia bovis was studied in 399 Bos indicus cattle 1-2 years old from 92 farms in the eastern Yucatán, México. The management factors studied were: farm-type, production system, herd size, farm size, stocking density, vector control, dipping interval, type of dipping, type of acaricide and cattle introduction to the farm. A cross-sectional study was carried out (2-stage cluster sampling). The number of serum samples was proportionally distributed according to the number of farms in the nine locations of eastern Yucatán, México (399 animals from 92 farms). Antibody activity to B. bovis was tested using an indirect ELISA. The farms with a seroprevalence < or = 75% were considered as cases and those with seroprevalence > 75% were considered as controls. The variables with p < or = 0.20 were included in fixed effects logistic regression. The seroprevalence of the zone was 73.8% (66.3-81.3%). The following risk factors were found: Stocking density (< 1 head/ha, OR = 4.04, CI (OR) = 1.20-13.62) and dipping interval (> 60 days, OR = 5.07 CI (OR) = 1.26-20.48).