ABSTRACT
Bovine tuberculosis is a chronic bacterial and major infectious disease of cattle and buffaloes caused by Mycobacterium bovis. Rapid diagnosis of bovine tuberculosis is considered one of the cornerstones for worldwide control as it permits early epidemiological and therapeutic interventions. Therefore, this study was designed to evaluate conventional techniques (tuberculin test, Ziehl Neelsen staining and culturing) in comparison with proven molecular laboratory techniques (LCD array and IS6110 PCR) for identification of Bovine tuberculosis. A total of 902 Egyptian animals (480 buffaloes and 422 cattle) were examined by tuberculin test, and the positive reactors were slaughtered. Tissue samples were collected for staining as well as culturing. Moreover, LCD array and PCR using IS6110 on DNA extracted from tissue and culture samples were carried out for molecular identification of M. bovis. According to the results, the tuberculin positive cases for cattle and buffaloes were 2.14% (9 cases) and 5.62% (27 cases), respectively. After post-mortem examination, the prevalence of tuberculin positive cases with visible lesions was 88.9% for cattle and 14.8% for buffaloes. Alternatively, these percentages were 11.1% and 85.2% for cattle and buffalo carcasses with non-visible lesions. The percentage of cattle and buffaloes showing positive culture was 88.9% and 62.9%, respectively. This percentage was 69.5% after staining with Ziehl Neelsen. In contrast, LCD array and IS6110 were 100%, confirming the isolation results. In conclusion, LCD array depending on 16S RNA and DNA hybridization with specific probes for detection of M. bovis are rapid, sensitive and labor-saving when combined with IS6110-PCR.
ABSTRACT
Sensitivity to commercial teat dips (nonoxinol-9 iodine complex and chlorhexidine digluconate) of 56 Staphylococcus (S.) aureus strains isolated from quarter milk samples of various German dairy herds treated with different teat dipping schemes was investigated in this study. The minimum inhibitory concentration was determined using a broth macrodilution method according to the German Veterinary Association guidelines. The main objective of the current study was to induce in vitro resistance induction of S. aureus to chemical disinfectants. Ten different strains were repeatedly passed ten times in growth media with sub-lethal concentrations of disinfectants. Nine strains showed a significant reduction in susceptibility to the nonoxinol-9 iodine complex but only one strain developed resistance to chlorhexidine digluconate. Stability of the acquired resistance was observed in all S. aureus strains adapted to the nonoxinol-9 iodine complex and chlorhexidine digluconate. In contrast, simultaneous resistance to different antibiotics was not observed in any of the ten investigated S. aureus strains. However, the isolates exhibited a high degree of resistance to penicillin G. Based on these results, resistance of S. aureus to chemical disinfectants may be more likely to develop if the chemicals are used at concentrations lower than that required for an optimal biocidal effect.
