Antibiotic resistance trend of Staphylococcus aureus isolated between 2010 and 2012 from mastitis cases in Azawak zebu in Niger

The present study was conducted at the Sahelian Experimental Station in Toukounous Niger, on three herds of Azawak zebu breed in order to evaluate antimicrobial susceptibility of a total of 43 Staphylococcus aureus isolated from 164 milk samples of cows with subclinical mastitis from 2010 to 2012. The highest frequency of resistance was observed for the β-lactam family: penicillin (46%) followed by oxacillin (12%). Twenty isolates were sensitive to all tested antibiotics, 12 were resistant to one of them and 11 were multi-resistant (2 to 5 antibiotics). The resistance percentage to oxacillin, enrofloxacin and clindamycin varied significantly over the 3 years (p <0.05) but not to the other antibiotics. Moreover, 90% of S. aureus isolates resistant to penicillin detected by in vitro disk diffusion possessed the blaZ gene. In conclusion, the isolates from cases of mastitis at Toukounous are more resistant to the antibiotics frequently used for treatments at the station than to other antibiotics. Key words: Mastitis, Staphylococcus aureus, antibiotic resistance, Azawak zebu, Niger.