Comparison of types and antimicrobial susceptibility of Staphylococcus from conventional and organic dairies in west-central Minnesota, USA.
OBJECTIVE
To assess whether conventional and organic dairy management practices are associated with differences in the susceptibility of Staphylococcus to antimicrobial agents.


RESULTS
Staphylococcus was isolated from milk samples collected from conventional and organic dairies in west-central Minnesota. Isolates were categorized as (1) coagulase-positive, (2) novobiocin-sensitive coagulase-negative or (3) novobiocin-resistant coagulase-negative. Novobiocin-resistant coagulase-negative Staphylococcus (CNS) was more common on conventional farms and novobiocin-sensitive CNS predominated the isolates from organic farms. Overall, a larger proportion of isolates from organic rather than conventional farms were susceptible to erythromycin, pirlimycin and tetracycline. However, for pirlimycin and tetracycline, different patterns of susceptibility were observed among Staphylococcus categories.


CONCLUSIONS
In this study, organic dairy management was associated with more overall antimicrobial susceptibility among Staphylococcus than was conventional management. However, different patterns of susceptibility among Staphylococcus categories suggest that multiple management practices, including some unrelated to antimicrobial use, may contribute to the observed differences in susceptibility.


CONCLUSIONS
This study adds to our understanding of the implications of dairy management choices.
Bombyk
R A M
RA
Division of Science and Mathematics, University of Minnesota, Morris, MN 56267, USA.
Bykowski
A L
AL
Draper
C E
CE
Savelkoul
E J
EJ
Sullivan
L R
LR
Wyckoff
T J O
TJ
D000822:Animal Husbandry / Q000379:methods; D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology; D001431:Bacteriological Techniques; D002417:Cattle; D002418:Cattle Diseases / Q000382:microbiology*; D015169:Colony Count, Microbial / Q000662:veterinary; D003612:Dairying; D005260:Female; D058870:Food, Organic; D007218:Industrial Microbiology; D008826:Microbial Sensitivity Tests; D008892:Milk / Q000382:microbiology; D008910:Minnesota; D013203:Staphylococcal Infections / Q000662:veterinary*; D013210:Staphylococcus / Q000145:classification / Q000187:drug effects / Q000302:isolation & purification*
D000890:Anti-Infective Agents