A preliminary survey of antibiotic residues and viable bacteria in milk from three Caribbean Basin countries

There is widespread concern about the presence of antimicrobial drugs in milk. The presence of drug residues in milk may have public health implications. Milk samples (n = 25 to 65/country) were collected from bulk tanks and commercial vendors in Barbados, Costa Rica, and Jamaica between February 1996 and August 1997. Bulk tank samples were collected from high milk-producing regions of Jamaica and Costa Rica and from 26 dairy farms in Barbados. Milk pH, bacterial growth (total CFU/ml and the presence of Streptococcus agalactiae and Staphylococcus aureus), and the presence of antimicrobials were determined. Milk samples were tested by a microbial inhibition test (Delvotest-P, Gist-Brocades Food Ingredients, Inc.) to screen for antimicrobial drugs. All positives were retested for the presence of beta-lactam antibiotics after incubating with penicillinase and some positives were identified by high-pressure liquid chromatography-UV. Mean pH values ranged from 6.5 to 6.7. S. aureus was identified in bulk tank samples from Costa Rica (52 percent), Barbados (44 percent), and Jamaica (46 percent). S. agalactiae was identified in bulk tank samples from Barbados (8 percent) and Jamaica (10 percent) but not in samples from Costa Rica. All positives in milk from Jamaica and Barbados were determined to be beta-lactams. No residues were detected in pasteurized milk samples from Barbados or ultrahigh-temperature milk from Jamaica. The presence of beta-lactam residues in some of these samples suggests the appropriateness of testing milk prior to processing for consumption.(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)

Metabolic activity of pathogenic bacteria during semicontinuous anaerobic digestion

In natural environments such as anaerobic digesters, bacteria are frequently subjected to the stress of nutrient fluxes because of the continual changes in the flow of nutrients, and to survive, they must be capable of adapting readily to nutrient changes. In this study, the metabolic activities of Escherichia coli, Salmonella typhimurium, Yersinia enterocolitica, Listeria monocytogenes, and Campylobacter jejuni were studied within culture bags (Versapor -200 filters, 0.22 - microns pore size) in laboratory anaerobic digesters. The metabolic activity of these bacteria was indicated by their adenylate energy charge (EC) ratios and their ability to incorporate [3H] thymidine, which was related to the respective changes in viable number within the culture bags during anaerobic digestion. Fluctuations in the adenylate EC ratios, the uptake of [3H] thymidine, and the viable numbers of E. coli, S. typhimurium, Y enterocolitica, and L. monocytogenes cells were probably due to constant changes in the amount of available nutrients within the anaerobic digesters. The viability of S.typhimurium increased quickly after a fresh supply of nutrients was added to the system as indicated by the uptake of [3H] thymidine and an increase in the adenylate EC ratios. The viable numbers of E. coli, S. typhimurium, Y. enterocolitica, and L. monocytogenes organisms declined rapidly from 10 (7) to 10 (8) CFU/ml to 10(3) to 10 (4) CFU/ml and remained at this level for an indefinite period. The decimal reduction time calculated during the period of exponential decline ranged from 0.8 to 1.2 days for these bacteria. C. jejuni had the greatest mean decimal reduction time value (3 - 6 days).(AU)

Microbial assessment of poultry processed in Jamaica

Microbial assessment of a chicken processing plant in Jamaica was conducted with a view of documenting existing conditions and determining their effect on the finished products. Despite the disadvantages of low chlorination levels, water restrictions and warm climate, chicken produced was safe for public consumption. Spoilage flora and shelf life were similar to those reported for developed countries. However, modifications to processing procedures were required to ensure a high quality product (Summary)