CylE and mig as virulence genes of streptococci isolated from mastitis in cows and buffalo in Egypt

Abstract

Objective: A study was carried out to investigate the prevalence of mastitis caused by Streptococcus agalactiae and Streptococcus  dysgalactiae in cows and buffalo reared in households and smallholder dairy farms, and to detect their antibiotics susceptibility, and  molecular investigation of some virulence genes (cylE and mig genes).
Design: Observational study.
Samples: A total of 288 milk samples were gathered from 72 mastitic animals (48 cows and 24 buffalo) from households and smallholder  dairy farms in Dakahlia and Domiatte Governorates, Egypt.

Procedures: Isolation and identification of S. agalactiae and S. dysgalactiae was  performed using conventional techniques. The identified  isolates were examined for antimicrobial resistance by disk diffusion assay, Minimum inhibitory concentration MIC by broth microdilution  method as well as virulence genes (cylE and mig genes) by polymerase chain reaction (PCR).
Results: Forty-five (62.5%) out of 72 animals showed the clinical signs of mastitis. Microbiological evaluation of 288 mastitis milk samples  was displayed 190 (65.72%) streptococci strains composing of 114 (60%) S. agalactiae and 76 (40%) S. dysgalactiae strains. The antibiotic  susceptibility tests revealed that S. agalactiae strains was resistant to trimethoprim (100%), followed by tetracycline and minocycline  (37.7%), whereas intermediate resistant was observed to other tested antibiotics. Moreover, S. dysgalactiae strains were highly resistant to  lincomycin, tetracycline (87.52 each), followed by trimethoprim (81.6) and minocycline (75%), while all strainswere susceptible to  penicillin, amoxicillin, cephapirin, and cefquinome. Additionally, the highest MIC with the widest range (1 to ≥128 μg/mL) was observed to  trimethoprim for S. agalactiae and to erythromycin and lincomycin for S. dysgalactiae. In contrast, the lowest MIC was detected to  penicillin, amoxicillin, cefquinome, and erythromycin for S. agalactiae and to penicillin, amoxicillin, cephapirin, cefquinome, and rifaximin  for S. dysgalactiae. The cylE gene was displayed in 6 (60%) S. agalactiae strains, whereas the mig gene was found in 4 (40%) S. dysgalactiae  strains.
Conclusion and clinical relevance: Our data highlights the importance of awareness of antibiotic resistant strains of S. agalactiae and S. dysgalactiae in various mastitic animals (cows and buffalo) in Egypt.