Staphylococci in dairy goats and human milkers, and the relationship with herd management practices

Abstract

Staphylococci are the most common bacteria isolated from goat milk. This includes Staphylococcus aureus, an important animal and human pathogen, and various coagulase negative staphylococci or CNS. In this study, we identified S. aureus isolates from goat milk samples and nares and from the hands and noses of people milking the goats, as well as CNS from goat milk. A total of 497 milk samples, 502 goat nasal swabs and 97 human swabs were collected on 30 North Carolina goat dairies. A survey was used to elicit information on herd management practices for each dairy and to aid in the assessment of the association between those practices and the presence of staphylococci. We found a very low prevalence of 1.4% (6/497) of S. aureus in milk, but a considerably higher prevalence of 46.2% (232/502) S. aureus in goat nasal swabs. Nearly one-third (32.6%; 162/497) of goat milk samples were CNS-culture-positive, with S. simulans, S. caprae, S. xylosus and S. chromogenes commonly isolated. Milkers’ hands and nasal swab samples were more frequently positive (25.8%; 25/97) for S. aureus than were goat milk samples (1.4%; 6/497). A wide range of milking routines was found, and gloves were not commonly worn by milkers (only 10% of farms milkers always wore gloves). The most common use of milk was home consumption and 28 of the 30 goat dairies reported the consumption of unpasteurized milk.