Comparison of Staphylococcus aureus Genotypes Recovered from Cases of Bovine, Ovine, and Caprine Mastitis

Abstract

Staphylococcus aureus is an important pathogen in domestic ruminants. The main objective of this study was to determine the similarity of epidemiologically unrelated S. aureus isolates from bovine, ovine, and caprine mastitis. By pulsed-field gel electrophoresis, 160 different pulsotypes (PTs) were identified among 905 isolates recovered from 588 herds in 12 counties in Norway. Based on estimates of similarity, using an 80% cluster cutoff, the isolates were assigned to 47 clusters. One cluster included 62% of all the isolates and more than 45% of the isolates from each host species. Twenty-three PTs included isolates from more than one host species; these 23 PTs represented 72% of all the isolates. The six most prevalent PTs included isolates from all host species and contained 45% of the bovine isolates, 54% of the ovine isolates, and 37% of the caprine isolates. Antimicrobial susceptibility testing of 373 of the isolates revealed resistance to penicillin in 2.9% and to streptomycin in 2.4%; only 1.9% were resistant to 1 of the other 11 antimicrobials tested. The results of this study suggest that a small number of closely related genotypes are responsible for a great proportion of S. aureus mastitis cases in cows, ewes, and goats in Norway and that these genotypes exhibit little or no host preference among these species. Selection due to antimicrobial resistance appears not to have contributed to the predominance of these genotypes.

Genetic Variation among Staphylococcus aureus Strains from Norwegian Bulk Milk

“…Eight of these pulsotypes were included in 10 clusters (clusters 32 to 41) that contained more than half the bulk milk isolates, 40% of the raw-milk product isolates, and all the ruminant mastitis isolates. These findings agree with those of Mørk et al (31), who genotyped 905 Norwegian S. aureus isolates from cases of bovine, caprine, and ovine mastitis by PFGE and found that between 50% and 60% of the bovine and caprine isolates belonged to pulsotypes common to both animal species.…”

“…These had been tested by PFGE previously and represented different PFGE banding patterns commonly observed for S. aureus isolates from cases of ruminant mastitis in Norway (31).…”

Bovine mastitis outbreak in Japan caused by methicillin-resistant Staphylococcus aureus New York/Japan clone

“…15 The pulsed-field gel electrophoresis (PFGE) pulsotypes (PTs) were analyzed by visual inspection using commercial software c according to the criteria described previously. 26,30 Briefly, a dendrogram was created using the Dice coefficient with optimization and a position tolerance setting of 1% based on the banding patterns of each PT. The PTs that showed >80% similarity in this dendrogram were defined as the same cluster.…”

Epidemiological Analysis of Staphylococcus aureus Isolated from Cows and the Environment of a Dairy Farm in Japan

“…Feeding of unpasteurized milk and close contact with carriers may be one reason for the spread of S. aureus to heifers, with this farming practice possibly leading to heifer mastitis. Furthermore, heifers purchased as replacements seem to be an important causal factor of IMI due to S. aureus [19,23]. According to the MLST website and previous reports, S. aureus strains from pets have similar genotypes to those aureus isolated from different samples in the dairy farm monitored.…”

“…The PFGE pulsotypes were analyzed by visual inspection using the BioNumerics software (version 5.10) according to the criteria described previously [19]. Allele number and sequence type (ST) were determined by using the MLST website (http:// www.mlst.net/).…”