Investigation into agr Specificity Groups among Nasal Isolates of Staphylococcus aureus from Cattle, Sheep and Goats Using Multiplex PCR

The accessory gene regulator (agr) is a central system that controls the expression of Staphylococcus aureus virulence factors and four allelic groups (designated as agr I-IV) have been identified in this system. The aim of this study was to ascertain the frequency of the different agr groups in S. aureus isolates recovered from the nasal cavity of healthy cattle، sheep، and goats. In the current study، 26 S. aureus isolates were recovered from the nasal cavity of 79 cattle (n = 4)، 78 sheep (n = 11)، and 44 goats (n = 11). Then، the isolates were agr typed by multiplex polymerase chain reaction (mPCR). Despite the low prevalence of S. aureus in the nose of cattle (5. 06%)، this organism is more commonly isolated from the nose of sheep (14. 1%) and goats (25%). Of 4 S. aureus isolates obtained from cattle، 3 were ascribed to agr type I and 1 to agr type IV. Seven out of 11 sheep nasal isolates were of agr type I، the other 4 being agr type III (n=3) and agr type II (n=1). Goat nasal isolates were distributed mainly across agr types I (n=10). Only one of the goat isolates was of agr type II. Overall، a low prevalence of S. aureus were found in the nose of cattle compared to small ruminants. Also، S. aureus isolates with agr type I were common and might be capable of colonizing the nasal cavity of ruminants، most likely by regulatory adaptation to the nose environment. Further studies will be necessary to define how the type of agr regulatory system might affect S. aureus nasal colonization.