The aim of the study was using polymerase chain reaction (PCR) technique for detecting the most bacteria causing mastitis in cows as streptococci spp., Escherichia coli and Staphylococcus aureus by using Genus specific primers for each one. One hundred milk samples were collected from cases of subclinical bovine mastitis positive for California Mastitis Test (CMT). The samples were bacteriologically cultivated on to 5% sheep blood agar and also, on different types of media (MacConkey's agar plates, Edward's agar medium and mannitol salt agar) to isolate the major bacteria causing mastitis and identified biochemically. Finally, these bacteria were identified by using PCR technique with a specific primer for each genus. The PCR results revealed that E. coli 16/46 (34.7%), Staphylococcus aureus (S. aureus) 12/40 (30%) and streptococci spp. 11/39 (28.2%). Multiplex PCR for typing of streptococci spp. revealed that St. agalactiae 3/39 (7.69%) and St. dysgalactiae 8/39 (20.51%). In conclusion, in the present study, PCR analysis was used for diagnosis of major bacteria causing subclinical mastitis in cows by using specific primers for each one. The most prevalent bacteria causing subclinical mastitis were E. coli, S. aureus, S. dysgalactia and S. agalactia.
Integrons play major roles in spreading and expression of antibiotic resistance genes among bacteria especially Gram-negative bacteria. However, the incidences of class 1 integrons in Gram-positive bacteria remained elusive. The present study was conducted to monitor the prevalence of class 1 integrons in Corynebacterium bovis (C. bovis) isolated from cases of bovine mastitis in Egypt. A total of 35 Corynebacteria spp., isolated from milk samples of subclinical mastitis, were examined using PCR analysis with 16S rRNA specific primers. The results revealed a prevalence of 8 (22.8%) C. bovis strains in the examined samples. All isolates of C. bovis showed an elevated level of resistance, mostly against spectinomycin, streptomycin followed by tetracycline, ampicillin, kanamycin, chloramphenicol and sulfamethoxazole-trimethoprim. Using PCR and DNA sequencing, two isolates of C. bovis were identified containing class 1 integrons that encoded aminoglycoside adenyltransferase type A (aadA1) as a gene cassette. The aadA1 confers resistance to spectinomycin/streptomycin. Additionally, class 1 integron resistance genes in C. bovis isolates were described utilizing PCR and DNA sequencing. These resistance genes conferred resistance to several antimicrobial agents frequently used in dairy farming. This study reports, for the first time, the detection and identification of class 1 integron containing aadA1 gene in C. bovis of animal origin.
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