Background: Dental caries result from an imbalance in the oral environment, where bacteria produce acids that gradually dissolve tooth enamel over time. This study aims to isolate and characterize oral bacteria morphologically and genetically, and to determine the susceptibility of the bacteria to antibiotics.
Objective: the research is to identify the predominant bacterial isolates responsible for dental caries using the Polymerase Chain Reaction (PCR) technique.
Methods: A total of 150 samples were collected from tooth surfaces at the Specialized Dental Center in Babylon and cultured on suitable media under anaerobic conditions. A total of 87 bacterial isolates were obtained, showing the predominance of Kocuria rosea and Streptococcus spp., in addition to unidentified isolates identified using the Vitek 2 system. Antibiotic susceptibility testing was also performed using the same system, and K.rosea isolates showed resistance to several antibiotics, especially erythromycin, while remaining sensitive to glycopeptides and tetracyclines. Polymerase Chain Reaction (PCR) was also conducted to detect the bacterial isolates.
Results: The isolates showed variable susceptibility to antimicrobial agents. A considerable proportion (41.7%) exhibited a multidrug-resistant (MDR) phenotype, with complete resistance to erythromycin and resistance to multiple antibiotic classes including macrolides, tetracyclines, aminoglycosides, fluoroquinolones, rifamycins, penicillins, and cephalosporins. However, all isolates remained susceptible to glycopeptides, oxazolidinones, and fosfomycin.
Conclusion: The study showed bacterial diversity in dental caries with the dominance of K. rosea and Streptococcus spp., along with the presence of multidrug-resistant isolates. PCR also confirmed the presence of virulence and resistance genes, highlighting their role in disease progression.