Molecular Detection of Tetracycline-Resistant Streptococcus viridans Bacteria Using the rpoA Gene

Objective: The aim of this study was to established diagnostic approaches to dental caries using polymerase chain reaction technology. Methods: PCR series. 60 samples of oral bacteria were collected between 8/6/2023 and 12/1/2023, where 27 teeth showed a growth rate for bacterial culture (45%). The bacterial isolates under study were characterized. The sensitivity of the bacterial isolates of Streptococcus viridans under study to eight antibiotics was tested. The results of the current study showed that the resistance rates were as follows: 71.4% for tetracycline, 57% for augmentin, 57% for ciprofloxacin, 28% for clindamycin, 57% for erythromycin, 57% for doxycycline, and 28% for doxycycline for clarithromycin. Results: The minimum inhibitory concentration (MIC) for the bacterial isolates under study was determined for the tetracycline antibiotic. S. viridansisolates showed resistance to this antibiotic through a sensitivity test using the disk method, as the MIC value. for the isolates ranged from (1024-8) micrograms/m l. The percentage of S. viridans isolates producing virulence factors was as follows: protease enzyme 42%, and membrane protease. Bioactive 71%, bacteriocin 14%, hemolycin 57%, DNAase 71%, capsule 28%, and lipase 28%. Conclusion: The total DNA of all bacterial isolates under study was extracted, after which a polymerase chain reaction (PCR) was performed for the S. viridans resistant to tetracycline and with an MIC value higher than 64 µg/ml using specialized primers targeting the specific sequence of the tetM gene with a size of 1,862bp. When the amplified products were migrated on an agarose gel, one band appeared in all tracks in the gel at the same level for all samples. The results showed that the presence of the tetM gene was 100%.