Bacterial mastitis in the Azawak zebu breed at the Sahelian experimental station in Toukounous (Niger): Identification and typing of Staphylococcus aureus

Though the government of Niger opted in 1975 for a policy of improving the dairy capability of the Azawak zebu cows, the national level of dairy production satisfies only 50% of population needs. Several reasons may explain this shortage, including the prevalence of mastitis. The purpose of this research was (i) to study the prevalence of mastitis at the Sahelian experimental station in Toukounous; (ii) to identify the bacterial species responsible; and (iii) to type the Staphylococcus (S. ) aureus isolates. Two hundred and sixty-five cows were tested using the California Mastitis Test (CMT) and the 112 CMT-positive milk samples (10.6%) from 104 cows (39.2%) were further tested for bacterial growth. Fifty-one of them (45.5%) gave a positive growth: half of the isolated bacteria belonged to the genus Staphylococcus and 23 (41.8%), to the species S. aureus . The majority of the S. aureus isolates belonged to the bovine biotype, formed biofilms, produced Small Colony Variants, grouped into closely related virulotypes, and belonged to two closely related pulsotypes. In conclusion, (i) the prevalence of presumptive mastitis in Toukounous is 40%; (ii) the genus Staphylococcus is the most frequent; and (ii) the 23 S. aureus isolates are closely related, though not clonal.