A Preliminary Survey of Antibiotic Residues and Viable Bacteria in Milk from Three Caribbean Basin Countries

Abstract

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 β-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%), Barbados (44%), and Jamaica (46%). S. agalactiae was identified in bulk tank samples from Costa Rica (28%), Barbados (8 and 16%), and Jamaica (18%). Antimicrobial residues were detected in some bulk tank samples from Barbados (8%) and Jamaica (10%) but not in samples from Costa Rica. All positives in milk from Jamaica and Barbados were determined to be β-lactams. No residues were detected in pasteurized milk samples from Barbados or ultrahigh-temperature milk from Jamaica. The presence of β-lactam residues in some of these samples suggests the appropriateness of testing milk prior to processing for consumption.