ISOLATION AND ANTIMICROBIAL SUSCEPTIBILITY OF STAPHYLOCOCCUS AUREUS AND OCCURRENCE OF METHICILLIN RESISTANT STAPHYLOCOCCUS AUREUS (MRSA) IN MASTITIC DAIRY COWS IN THE SELALE/FITCHE AREA, NORTH SHOWA, ETHIOPIA
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Date
2014-06
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Abstract
Bovine mastitis is of the most significant problems associated with high milk production loss
in Ethiopia. Staphylococcus aureus is still a major cause of bovine mastitis. MRSA is any
strain of Staphylococcus aureus that has developed resistance to beta-lactam antibiotics. It
has been known by a significant public health problem infected animals with MRSA might
serve as a potential source of human infection. This study was carried out with the aim that to
determine the prevalence of Staphylococcus aurous mastitis from the total of clinical and subclinical
mastitis and identify associated risk factors, isolates and identify Staphylococcus
aurous and MRSA strains from mastitic milk samples and conduct in vitro antimicrobial
susceptibility test on the isolates. Quarter milk samples from cows were examined to
determine the prevalence of Staphylococcus aureus, MRSA and different antibiotic resistant
pattern were determined in a cross-sectional study design. A total of 403 samples were
collected and screened for the presence of S. aureus. The overall prevalence of mastitis at cow
and quarter levels were 128 (83.1%) and 403 (65.42%) respectively. A total of 164 (40.69%)
S. aureus isolates were obtained and out of these isolates 60 (36.6%) were found MRSA
isolates during this study. The risk factors of mastitis like age group and pregnancy status had
no effect on (p>0.05) Staphylococcus aureus isolation whereas, stage of lactation and
previous mastitis history had significant effect on (p<0.05) isolates of S. aurous. A total of 61
isolate of S. aureus species were tested for antimicrobial sensitivity for 12 different types of
antibiotics. The S. aureus isolates showed highest sensitivity towards Amoxicillin-clavulinic
acid (80%), Chloroamphenicol (78.7%), Nitrofuration (73.8), Cefoxitin (67.2%),
Sulphamethoxazole-trimethoprim (59%) and also uncommonly 70.1% of S. aureus isolates
were found resistant to Vancomicin. The most frequent multidrug resistance pattern consisting
of three drugs is exhibited for, gentamicin, ceftazidime and streptomycin with a resistance of 7
(9.46%) of the isolates. Sixty four (86.46% of the isolates) were resistant to different
combinations of two or above tested antibiotics.
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Keywords
Mastitis, Staphylococcus aureus, Methicillin resistant S. aureus, antimicrobial susceptibility test