Isolation and identification of resistant bacteria from dental clinic and evaluation of biofilm formation by them

Surface bacterial contamination has been shown to be a potential source of cross-infection. The aim of this study was to identify resistant bacterial isolates in the dental clinic before and after disinfection and evaluation of biofilm formation by them.
Sampling was performed at a dental clinic in Isfahan, Iran, on 2014. Samples were obtained by using swab and settle plate method. In the firs method, sterile swabs were used to sample of dental instrument and unit chair surface before and after disinfection, then swabs were transferred to TSB media (60 tubes). In the second method, air monitoring was carried out by settling blood agar and nutrient agar plates at the certain distance from the patient for 1 hour (24 plates). Then these samples incubated aerobically for 2 days at 37°C. Isolates were identified to species level with morphological and biochemical features and 16S ribosomal RNA gene sequencing. In addition, the strength of biofilm formation by isolates was measured by using microtiter plate method.
Most of these isolates were spore-forming Bacillus species and environmental Staphylococcus species. On the basis of the strength of biofilm formation, the most important identified bacteria were Staphylococcus xylosus and Bacillus safensis.
Bacteria that are able to form biofilm, can survive after disinfection of dental instruments and can enhance the risk of infection in dental practice by providing a surface for colonization of pathogens.