Drug resistance in isolated bacteria from milk of sheep and goats with subclinical mastitis in shahrekord district

ABSTRACT

Four-hundred milk samples from half udders of 20 flocks of native breed goats were aseptically collected. The samples were examined by California mastitis test [CMT]. Twenty-one [5.25%] of 400 were CMT-positive. The CMT-positive samples were then cultured and the following bacteria were isolated Staphylococcus aureus in 3 [14.28%], CNS [coagulase-negative staphylococci] in 14 [66.66%], streptococci in 4 [19.04%] and Mycoplasma spp. in 11 [52.38%] samples. The isolated staphylococci were examined to evaluate their resistance to different antibiotics by disc diffusion method. CNS resistance to amikacin was 78.5%, to penicillin was 50%, to tetracycline 50%, to ampicillin 42.8%, and to doxycycline was 28.5%. Four-hundred native breed sheep milk samples were taken from 19 flocks in the same conditions. The samples were examined by CMT test. 19 [4.75%] of 400 were CMT-positive. The CMT-positive samples were cultured and the following bacteria were isolated S, aureus in 2 [10.5%], CNS in 7 [36.8%], streptococci in 2 [10.5%], Pasteurella in 1 [5.26%] and Mycoplasma in 9 [47.37%] samples. The isolated staphylococci were examined for antibiotic susceptibility. CNS resistance to amikacin was 42.8%, and to tetracycline, ampicillin, oxycycline and penicillin was 14.3%. Both isolates of S. aureus were resistance to penicillin