Longitudinal study on the susceptibility to bacteriophages of Staphylococcus aureus strains isolated from dairy farms in Trinidad

A 6-month longitudinal study was conducted on 30 dairy cows in early lactation and their human handlers on six farms across Trinidad. Weekly samples of bulk milk, composite milk and anterior nares and hand swabs from human handlers were collected and cultured for Staphylococcus aureus on Baird-Parker agar (BPA). The susceptibility of S. aureus strains to bacteriophages and the relatedness of strains isolated over the study period were determined. Sixty-three (51.2 percent) of 123 strains of S. aureus from bulk milk were typable compared with 111 (57.3 percent) of 194 and 82 (61.7 percent) of 133 strains isolated from composite milk and human handlers, respectively. The differences were not statistically significant (P> 0.05; chi 2). Bovine phage 42D lysed 3.3 percent (4 of 123), 16.5 percent (32 of 194) and 12.0 percent (16 of 133) of S. aureus strains isolated from bulk milk, composite milk and human handlers, respectively. The differences were statistically significant (P< 0.001; chi 2). Amongst bulk milk isolates of S. aureus, 35 (31.8 percent) of 110 exhibited relatedness in 11 groups based on their phage patterns and groups. The mean maximum interval between the first and last detection of related S. aureus strains in a group was 11.5 +/- 7.3 weeks. Amongst composite milk strains of S. aureus, 23 (46.0 percent) of 50, 25 (62.5 percent) of 40 and 22 (53.7 percent) of 41 exhibited relatedness on farms IB 2, IB 27 and IC 23, respectively, but the differences were not statistically significant (P> 0.05; chi 2). On farm IB 2, five groups of related strains of S. aureus were detected with a mean maximum interval of detection of 18.2 +/- 8.5 weeks compared to farm IB 27 where five groups of related strains were also observed but with an interval of 13.8 +/- 8.2 weeks. On farm IC 23, a total of seven groups of related S. aureus strains detected with a mean interval of 8.0 +/-5.5 weeks. For human strains of S. aureus from farm IB 2, nine (56.3 percent) of 16 strains isolated from anterior nares exhibited relatedness in three groups with a mean maximum interval of 13.3 +/- 4.7 weeks compared to four (25.0 percent) of 16 hand swab isolates which exhibited relatedness in two groups with a mean maximum interval of detection of 20.5 +/- 2.1 weeks compared to hand swab isolates, with six (50.0 percent) of 12 showing relatedness in two groups and a mean interval of 10.5 +/- 2.1 weeks. (AU)

Prevalence and characteristics of Staphylococcus aureus strains isolated from bulk and composite milk and cattle handlers

The prevalence and characteristics of Staphylococcus aureus strains isolated from bulk and composite milk and from cattle handlers on dairy farms in Trinidad were determined. S. aureus strains isolated from all 175 bulk milk samples tested (100 percent) while 280 of 287 composite milk samples (97.6 percent) yielded S. aureus. The mean counts of S. aureus in bulk milk ranged from 5.9 x 10(3) to 1.2 x 10(5) CFU/ml compard with mean S. aureus counts in composited milk which ranged from 2.4 x 10(3) to 3.0 x 10(4) CFU/ml. Of the 105 strains of S. aureus from bulk milk tested, 45 (42.9 percent) were enterotoxigenic elaborating staphylococcal enterotoxin A (SEA), SEB, SEC, SED, or a combination compared to 69 of 146 strains (47.3 percent) recovered from composite milk which were enterotoxigenic but the difference was not statistically significant (P > = 0.05; chi 2). Twenty-two of 42 bulk milk samples containing enterotoxigenic S. auerus (52.4 percent) had counts of the organism which exceeded 10(4) CFU/ml. For S. aureus strains isolated from cattle handlers, 66 of 146 (45.2 percent) were enterotoxigenic. Prevalence of resistance to nine antimicrobial agents tested was 18.7 percent and 12.9 percent among bulk milk and composite milk isolates, respectively, compared to 49.3 percent and 69.5 percent among isolates from human anterior nares and hand swabs, respectively. Resistance to ampicillin and penicillin was highest among both milk (12.2 percent) and human (53.6 percent) isolates of S. aureus, and the difference was statistically significant (P < or = 0.001); chi 2). It was concluded that bulk milk containing relatively high counts of enterotoxigenic S. aureus may constitute a health hazard to consumers(AU)

Prevalence and characteristics of Staphylococcus aureus strains isolated from bulk and composite milk cattle handlers

The prevalence and characteristics of Staphylococcus aureus strains isolated from bulk and composite milk and from cattle handlers on dairy farm all 175 bulk milk samples tested (100 percent) while 280 of 287 composite milk samples (97.6 percent) yielded S. aureus. The mean counts of S. aureus in bulk milk ranged from 5.9 x 10(3) to 1.2 x 10(5) CFU/ml compared with mean S. aureus counts in composite mild which ranged from 2.4 x 10(3) to 3.0 x 10(4) CFU/ml. Of the 105 strains of S. aureus from bulk milk tested, 45 (42.9 percent) were enterotoxigenic elaborating staphylococcal enterotoxin A (SEA), SEB, SEC, SED, or a combination compared to 69 of 146 stains (47.3 percent) recovered from composite milk which were enterotoxigenic, but the difference was not statistically significant (P > 0.05; chi 2). Twenty-two of 42 bulk milk samples containing enterotoxigenic S. aureus (52.4 percent) had counts of the organism which exceeded 10(4) CFU/ml. For S. aureus strains isolated from cattle handlers, 66 of 146 (45.2 percent) were enterotoxigenic. Prevalence of resistance to nine antimicrobial agents tested was 18.7 percent and 12.9 percent among bulk milk and composite milk isolates, respectively, compared to 49.3 percent and 69.5 percent among isolates from human anterior nares and hand swabs, respectively. Resistance to ampicillin and penicillin was highest among both milk (12.2 percent) and human (53.6 percent) isolates of S. aureus, and the difference was stastically significant (P < or in 0.001; chi 2). It was concluded that bulk milk containing relatively high counts of enterotoxigenic S. aureus may constitute a health hazard to consumers(AU)

Isolation of Rhodococcus equi from the abscess of a goat in Trinidad

Rhodococcus equi was first islolated from infected foals by Magnusson in 1923. On a review of R. equi infection in humans and animals, Prescott showed that only two cases of R. equi infection have been reported in goats. According to him, the organism has a tendency to cause liver abscesses, possibly following penetration from the intestinal tract. It is not clear to us how the animal acquired the infection. There is no information about close contact with horses in the farm or origin in England (AU)