Novel Isolation and Identification Methods for Enterococcus Species and Their Distribution in the Human Oral Cavity

Purpose: In recent years, vancomycin-resistant Enterococcus (VRE) has spread worldwide, and the acquisition of resistance to antibiotics other than vancomycin has become a significant problem. While Enterococcus species have been considered part of the normal flora of the digestive tract, including the oral cavity, it remains unclear whether they are actually present in all human mouths and which species are detected. Therefore, this study aimed to develop selective media for reliable detection of Enterococcus species from various oral samples and to establish a highly accurate identification and detection method using multiplex PCR targeting five Enterococcus species. Using this method, we conducted a detailed investigation of the distribution of these organisms in the human oral cavity. Methods: Antimicrobial susceptibility testing using antibiotic discs was performed to develop selective media for the highly accurate detection of Enterococcus species in human oral samples. Additionally, Enterococcus species-specific primers for multiplex PCR identification were designed. Furthermore, the developed selective media and multiplex PCR method were used to investigate the distribution of Enterococcus species in 30 subjects and the emergence of vancomycin resistance in isolated strains. Conclusion: Enterococcus species were detected in 8 subjects (26.7%). Multiplex PCR-based bacterial species identification revealed that the Enterococcus isolates were E. faecalis, E. hirrae, E. casseliflavus, and E. durans. No VRE was detected.