Asian Journal of Microbiology, Biotechnology & Environmental Sciences Paper

Vol.13, Issue 3, 2011; Page No.(399-408)




A total of 135 swab specimens were obtained by swabbing around instruments from three different dental clinics namely restorative, preventive and oral surgery clinics of the University of Benin Teaching Hospital, Edo State, Nigeria of which 45 swabs were obtained from each clinic. Sterile swab sticks were first briefly dipped into sterile distilled water and then used to rub the surfaces of selected instruments which were immediately taken to the laboratory and processed. Total hetetrophic bacterial and fungal counts were carried out in sterile nutrient broths and potato dextrose broths respectively by standard methods. Swabs were asceptically inoculated on sterile MacConKey, Cysteine Lactose Electrolyte Deficient (CLED) and Mannitol Salt agar plates and incubated at 370C for 24hrs. Swabs were also asceptically inoculated on sterile Potato Dextrose agar plates and incubated at 280C for 7 days. The highest heterotrophic bacterial plate count (HBPC) of 21.6±0.52x103 CFU/mL was recovered apiece from carver and hatchet instruments respectively in the restorative clinic. The lowest count (15.9±0.64x103 CFU/mL) was recovered from the condenser equipment. The upper right molar forceps and straight hospital elevator as obtained in the preventive and oral surgery clinics respectively recorded the highest HBPC of 21.0±1.96x103CFU/mL and 20.7±67x103 CFU/mL respectively. The highest (30.6±0.57x103CFU/mL) and lowest (27.3±0.58x103 CFU/mL) heterotrophic fungal plate count (HFPC) were recovered from the dental hoe and plastic instruments respectively. In the preventive and oral surgery clinics, the highest HFC (24.7±1.82x103 CFU/mL) and 30.6±0.46x103 CFU/mL respectively were obtained from the restorative clinic upper right molar forceps and mouth mirror instruments respectively. Overall means of total HBPC and HFPC recovered from all equipment analyzed in the restorative, preventive and oral surgery clinics showed that there was no significant difference between HBPC and HFPC (P > 0.05). Identified bacterial organisms were Staphylococcus aureus, coagulase negative Staphylococci, Escherichia coli, Klebsiella spp, Proteus spp, Serratia spp and Pseudomonas aeruginosa. Fungal organisms identified were mainly Candida species. A total of 41, 57 and 43 strains of the various isolates were recovered from the restorative, preventive and oral surgery clinics respectively of which the preventive clinic recorded the highest microbial load. Instruments sampled from the restorative clinic were contaminated by strains of Candida species as the highest occurring organism followed by Staphylococcus aureus. The least occurring strains were those of E.coli and Serratia spp. The carver and condenser instruments sampled from the restorative clinic were mostly contaminated by 12 (29.3%) strains apiece of total microbial load recovered. The plastic instrument from which 6 (14.6%) load was recovered, was the least contaminated. Instruments sampled from preventive clinic appeared to be the most contaminated with HBPC of 92.5±0.15x103 CFU/mL as compared with those sampled from the oral surgery clinic having HBPC of 80.1±0.28x103 CFU/mL. While the upper right molar forceps and straight hospital elevator were the most contaminated instruments sampled from the preventive and oral surgery clinics respectively, the least contaminated were lower molar forceps and upper left forceps respectively. The best and most appropriate way of preventing bacterial colonization of the dental operatory and its equipment is by proper/adequate disinfection/sterilization of surfaces between instruments. These measures will guarantee the safety, health and productivity of staff and patients as well as reduce nosocomial infections. The overall effect of this will be a cleaner, safer and healthier public.

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