GER performed the dye accumulation antimicrobial susceptibility assays. THK provided the MDR A. baumannii CAL-101 supplier isolates, characterized the bla OXA sequences in DB and R2. KLC conceived

the study. LJP and KLC participated in the design and coordination and helped to draft the manuscript. All authors read and approved the final manuscript.”
“Background Dental caries represents one of the most common infectious diseases afflicting humans [1]. Of the mutans group of streptococci, Streptococcus mutans (serotype c, e, f, and k mutans streptococci) and Streptococcus sobrinus (serotype d and g mutans streptococci), which are Gram-positive oral commensal species, are strongly implicated as etiological agents associated with human dental caries. Previous investigations have reported

that S. sobrinus has a higher acidogenic capacity compared I-BET-762 research buy with S. mutans, and the prevalence of S. sobrinus is more closely associated with high caries activity than is that of S. mutans[2, 3]. These studies suggest the importance of the diagnoses of infection by these organisms. Previously, several studies have reported methods for diagnosis of these organisms [4, 5]. However, DNA-based detection and quantification of specific www.selleckchem.com/products/Nilotinib.html bacteria cannot distinguish between live and dead bacteria. Bacterial DNA is degraded after the loss of cell viability; thus, the remaining DNA of already dead bacteria can still act as a template DNA for PCR. Consequently, DNA-based detection systems overestimate the cell population. However, we have not differentiated live and dead bacteria within the context of diagnosis of oral infectious diseases, including dental caries. In the present study, we successfully developed and evaluated a discriminative method between live and dead bacteria for the human cariogenic

pathogens S. mutans and S. sobrinus using propidium monoazide (PMA). Previously, ethidium monoazide (EMA) was used for discriminating live from dead bacterial cells [6, 7]. EMA is a DNA/RNA intercalating substance that only enters bacterial cells with compromised 4-Aminobutyrate aminotransferase cell walls and cell membranes. However, EMA was reported to possibly to penetrate viable cells of some bacterial species, resulting in underestimation of viable bacterial numbers [8–11]. Because PMA is less able to penetrate viable cells, more attention has been paid to PMA as an alternative to EMA [8]. In the present study, we examined the population of live and dead bacteria in oral specimens. The relationships of cell viability with saliva and dental plaque or carious dentin were further analyzed. Finally, we analyzed the cell viability of S. mutans assessed by this PMA technique after treatment with hydrogen peroxide (H2O2) and proposed the usefulness of this technique for biofilm experiments. This is the first report to apply the combination of PMA plus real-time PCR (PMA-qPCR) for analysis of the prevalence of live/dead S.