Diversity of Streptococcus agalactiae and Staphylococcus aureus ribotypes recovered from New York dairy herds.
OBJECTIVE
To develop a reference database for characterization of bovine Staphylococcus aureus and Streptococcus agalactiae strains by automated ribotyping and to use it to assess the discriminatory power of this typing procedure and the geographic distribution of Sta aureus and Str agalactiae strains in New York state dairy herds.


METHODS
22 commercial dairy herds.


METHODS
Isolates of Sta aureus and Str agalactiae from bovine milk were identified by standard bacteriologic procedures, then typed by automated ribotyping. Antimicrobial susceptibility of isolates was tested in vitro. Two indicators made from the data were percentage of farms with multiple ribotypes and percentage of single ribotypes found in several geographic regions. Standard bacteriologic diagnosis, automated ribotyping, and determination of antibiograms (Kirby-Bauer method) also were done.


RESULTS
Of 50 Sta aureus and 44 Str agalactiae isolates from composite milk samples of 12 and 10 herds, respectively, 18 and 14 ribotypes, respectively, were identified. The discriminatory power of automated ribotyping was approximately 0.96 (Hunter-Gaston's formula). A higher percentage of herds with Sta aureus had multiple ribotypes. The most common Sta aureus ribotypes tended to have broader geographic distribution. Some Sta aureus ribotypes were significantly associated with antibiotic resistance profiles.


CONCLUSIONS
Automated ribotyping appears to characterize bovine strains of bacteria associated with intramammary infections with a high discriminatory index. Potential applications include identification of strains that appear to have broad geographic distribution suggesting interfarm transfer, discrimination between recurrent versus new intramammary infections (ie, for control of Str agalactiae and Sta aureus), and evaluation of antibiotic therapy.
Rivas
A L
AL
Quality Milk Promotion Services, College of Veterinary Medicine, Wilmington, DE, USA.
González
R N
RN
Wiedmann
M
M
Bruce
J L
JL
Cole
E M
EM
Bennett
G J
GJ
Schulte
H F
HF
Wilson
D J
DJ
Mohammed
H O
HO
Batt
C A
CA
D000818:Animals; D000900:Anti-Bacterial Agents / Q000627:therapeutic use; D002417:Cattle; D002418:Cattle Diseases / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology; D016172:DNA Fingerprinting / Q000379:methods / Q000662:veterinary*; D004275:DNA, Ribosomal / Q000032:analysis* / Q000235:genetics; D004352:Drug Resistance, Microbial; D005260:Female; D014644:Genetic Variation; D015994:Incidence; D008321:Mammary Glands, Animal / Q000382:microbiology; D008892:Milk / Q000382:microbiology; D009518:New York / Q000453:epidemiology; D010406:Penicillins / Q000627:therapeutic use; D012016:Reference Values; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary; D013211:Staphylococcus aureus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D013290:Streptococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000662:veterinary; D013292:Streptococcus agalactiae / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification
D000900:Anti-Bacterial Agents; D004275:DNA, Ribosomal; D010406:Penicillins