Abstract:
BACKGROUND : Staphylococcus aureus is a contagious, opportunistic pathogen that causes clinical or subclinical
mastitis in dairy cattle. The genetic background and antimicrobial resistance of isolates from Ethiopian dairy farms
has not been studied. Therefore, the aim of this study was to characterize S. aureus from Ethiopian hand milked
dairy cows, by spa, MLST and virulence factor typing, and by assessment of antimicrobial susceptibility. A total of
79 S. aureus isolates from intramammary infections was studied. A PCR was used to detect lukM-lukF’ and pvl genes
encoding the bovine and human associated bi-component leukocidins, and the toxic shock syndrome toxin gene-1
(tst). Antimicrobial susceptibility was determined using the broth microdilution method.
RESULTS : Twenty different spa types were identified, most isolates were t042 (58%), and the closely related t15786
(11%). The proportion of isolates positive for lukM-lukF’, tst and pvl was low at 0.04, 0.10 and 0.09 respectively, with
lukM-lukF’ often co-occurring with tst, but notwith pvl. Methicillin-resistance was not found, but resistance to penicillin/
ampicillin (86%) and tetracycline (54%) was very common.
CONCLUSIONS : We found a high degree of relatedness among bovine S. aureus isolates in North-Western Ethiopia,
suggesting contagious within and between farm transmission of strains that are often resistant to commonly used
antimicrobials. This highlights the need for effective preventive measures that aim at limiting transmission of bacteria
rather than using antimicrobials to control S. aureus mastitis in Ethiopia.
