Streptococcus zooepidemicus is an opportunistic pathogen associated with a wide variety of diseases e.g. pneumonia, septicemia, mastitis, placentitis and endometritis. The pathogenesis of a respiratory infection with S. zooepidemicus, factors associated with the bacteria, as well as with the host, appear to play a major role in the clinical appearance and outcome of the disease. S. zooepidemicus was isolated from of 91 out of 136 samples of foal's disease (38.9%). The highest rate was from nasal swabs of diseased foals (83.5%) followed by lung and lymph nodes of dead foals (66.6%) and the lowest rate (16%) of isolation was from nasal swabs of apparently healthy foals. On the other hand, 17 isolates of S. zooepidemicus (42.5%) were isolated from 40 samples collected from mares (vaginal wash and placenta) and 68.3% from aborted feti. Six isolates (3 from respiratory cases and 3 from abortion cases) were subjected to PCR for detection of virulence sodA gene, where all isolates were positive. The most effective antibiotic for S. zooepidemicus was ceftiofur (75%) and vancomycin.
Heat map analysis showed the intensity of resistance of S. zooepidemicus isolates were multidrug resistant mainly for β lactams (Cephalosporins), β lactams (Pencillins) and the resistance ranged from 100% to 25%, also the resistance was for tetracyclines (100 to 90%); fluoroquinolones (100 to 50 %), Lincosamides (100 to 75%) and glycopeptides (vancomycin
75 to 25%). Also, heat map analysis showed that S. zooepidemicus isolated from aborted feti showed high intensity of resistance to most antibacterial agents used in the study followed bythose isolated from mares. These results revealed the isolates causing abortion has different multidrug resistance profiles than that isolated from foal with respiratory symptoms.