Abstract
Background:
Staphylococcus aureus is a typical pathogenic agent causes several morbidities and mortalities which variable largely following the severity of bacteria and activity of host immunity.
Aim:
Isolation of S. aureus from different cattle infections, molecular detection of nuc gene in positive S. aureus isolates and identification the effectiveness of phagocytic activity.
Methods:
Totally, 100 cattle with various infections (25 wounds, 25 abscesses, 25 nasal discharge, and 25 ear swaps) were selected and subjected for collection of swabs under controlled conditions. All collected samples were cultured on Mannitol salt agar (MSA) and assessed by the biochemical tests. Targeting the nuc gene, all study MSA positive isolates were examined molecularly by conventional polymerase chain reaction (PCR), and then subjected for antibiotic susceptibility test. Jugular venous blood was collected from all infected animals in addition to 20 healthy cattle that selected as a control group to estimate the phagocytic activity of S. aureus isolates.
Results:
The findings of MSA culture revealed a totally 80 positive samples to S. aureus as 23, 21, 20, and 16 positive isolates for nasal discharge, abscess, wound and ear swab, respectively; based on its morphology, cultural trait, and biochemical test. Subsequently, PCR assaying of MSA positive isolates was demonstrated an overall 59 positive samples as 14, 16, 12 and 17 positive isolates for nasal discharge, abscess, wound and ear swab, respectively. Antibiotic susceptibility testing of S. aureus positive PCR isolates reported a significant high sensitivity to chloramphenicol and vancomycin, and a high resistance to penicillin. Finally, there was a considerable decline in phagocytic activity in particular 2 weeks post infection as a result of bacterial invasion.
Conclusion:
This study shows a high prevalence of S. aureus in cattle infections, and protocol includes regular screening of cattle infection and suitable therapy based on antibacterial susceptibility test is of great importance in long-term control of pathogen. However, additional molecular studies targeting other genes of S. aureus and the role of immune markers in different infections should be aimed

Key words: Antibiotic susceptibility, Bovine bacterial infection, Molecular test, Polymerase chain reaction, Iraq