Using a biological indicator to detect potential sources of cross-contamination in the dental operatory

Topographic aspects of airborne contamination caused by the use of dental handpieces in the operative environment

BACKGROUND

The use of dental handpieces produces aerosols containing microbial agents, bacteria, and viruses representing a high-risk situation for airborne cross infections. The aim of this study was to map and quantify the biological contamination of a dental operatory environment using a biological tracer.

METHODS

Streptococcus mutans suspension was infused into the mouth of a manikin, and an operator performed standardized dental procedures using an air turbine, a contra-angle handpiece, or an ultrasonic scaler. The presence of the tracer was measured at 90 sites on the dental unit and the surrounding surfaces of the operatory environment.

RESULTS

All tested instruments spread the tracer over the entire dental unit and the surrounding environment, including the walls and ceiling. The pattern and degree of contamination were related to the distance from the infection source. The maximum distance of tracer detection was 360 centimeters for air turbine, 300 cm for contra-angle handpiece, and 240 cm for ultrasonic scaler. No surface of the operative environment was free from the tracer after the use of the air turbine.

CONCLUSIONS

Attention should be paid to minimize or avoid the use of rotary and ultrasonic instruments when concerns for the airborne spreading of pandemic disease agents are present.

PRACTICAL IMPLICATIONS

This study supports the recommendations of dental associations to avoid treatments generating aerosols, especially during pandemic periods. Guidelines for the management of dental procedures involving aerosols, as well as methods for the modification of aerosols aimed to inactivate the infective agent, are urgently needed.

Isoenzymatic genotyping of Staphylococcus aureus from dairy cattle and human clinical environments reveal evolutionary divergences

Background

The genetic variability of 610 S. aureus isolates from the hands of professional dentists (A), dental clinic environment air (B), bovine milk from cows with and without mastitis (C), an insufflator for milking equipment (D) and milking environment air (E) was studied by isoenzyme genotyping and genetic and cluster analysis.

Results

Monoclonal and polyclonal patterns of S. aureus were detected in every bacterial population; however, isolates belonging to the same strain were not found among the populations, suggesting the genetic heterogeneity and the intrapopulation spread of strains. Genetic relationship analysis revealed the co-existence of highly related strains at low frequency among populations.

Conclusion

The data suggest that some strains can adapt and colonize new epidemiologically unrelated habitats. Consequently, the occurrence of an epidemiological genotypic identity can assume a dynamic character (spread to new habitats), however infrequently. A tendency of microevolutionary and genetic divergences among populations of S. aureus from human sources (AB) and bovine milk (DE), and especially the mammary quarter (C), is also suggested. This research can contribute to the knowledge on the distribution and dissemination of strains and the implementation of control measures and eradication of S. aureus in important dental clinic environments, as well as animal environments and dairy production.

Dynamics of the seasonal airborne propagation of Staphylococcus aureus in academic dental clinics

Objective

Staphylococcus aureus strains can be disseminated during dental treatments and occasionally lead to the contamination and infection of patients and dentists, which is an important public health problem. The dynamics of the airborne propagation and the genetic diversity of S. aureus isolated in an academic dental clinic environment were investigated using isoenzyme typing.

Material and Methods

The isoenzymes of 44 previously reported isolates were obtained from fresh cultures and extracted using glass beads. Nine isoenzymes were investigated using multilocus enzyme electrophoresis (MLEE). The genetic diversity and relationship among the strains (electrophoretic type – ET) were determined using statistics previously described by Nei²⁵ (1972) and the SAHN grouping method (UPGMA algorithm).

Results

Clonal pattern analyses indicated a high level of genetic polymorphism occurring among the 33 ETs, which were grouped into five taxa. Each taxon presented one or more clusters that were moderately related and that contained two or more identical/highly related isolates, revealing seasonal airborne propagation in these dental clinic environments.

Conclusions

These data suggest the occurrence of active microevolutionary processes in S. aureus as well as the possibility of environmental propagation during a 14-month time span. Such findings are important to show that multiuser academic dental clinics can retain certain strains that are spreadable to different niches.

Detection and Quantification of Dental Unit Water Line Contamination by Oral Streptococci

Objective.

(1) To investigate the prevalence of oral streptococci (OS) and biological indicators of water contamination by oral fluids in water from dental unit water lines (DUWs) by detection and quantification and of saprophytes indigenous to the oral cavity. (2) To test whether measurement of the total cultivable mesophilic flora (TCF), the parameter commonly used to monitor water quality in DUWs, is an effective predictor for OS contamination.

Design.

Survey of 21 dental units equipped with antiretraction devices. Water samples were collected from air-water syringes, cup fillers, tap water, and before and during the working day.

Setting.

Units were from 7 public dental offices selected for convenience from among those in proximity of the microbiological laboratory.

Methods.

For detection of OS, samples were plated on an enriched medium, to revitalize the organisms. Colonies were subcultured on a selective medium and biochemically identified (lower detection limit, 1 cfu/mL). For measurement of the TCF, samples were plated on a nutrient-poor medium. Cultures with colony counts greater than 200 cfu/mL were considered to be TCF positive. The sensitivity and specificity of TCF positivity in predicting OS detection was calculated.

Results.

Prevalence rates for OS contamination and for TCF positivity were, respectively, 34.4% (11 of 32 samples) and 25.0% (8 of 32 samples) for syringes, 27.8% (10 of 36 samples) and 8.3% (3 of 36 samples) for cup fillers, and 0.0% (0 of 7 samples) for tap water. OS contamination levels ranged from 1 to 6 cfu/mL. No statistically significant differences were found between samples obtained before and during the working day. TCF positivity did not predict OS contamination effectively, because of low sensitivity.

Conclusions.

Given the absence of OS in tap water, the reported prevalence of OS contamination suggests that oral fluids are aspirated during dental therapy with relatively high frequency and that DUWs can potentially expose successive patients to bloodborne cross-infections.

Isolation and Antimicrobial Resistance ofStaphylococcus aureusIsolates in a Dental Clinic Environment

Objective.

To determine the number ofStaphylococcus aureusisolates collected in a dental clinical environment and to determine their susceptibility to antimicrobial agents commonly used in dentistry.

Setting.

Undergraduate clinic of the Dental School of Piracicaba, University of Campinas, Brazil.

Methods.

Sterile cotton swabs were used to collect the samples from dental-chair push buttons, light handles, 3-in-l syringes, computer “Enter” keys, doorknobs, and X-ray tubes before, during, and after clinical procedures. These samples were spread on brain-heart infusion agar and were incubated at 37°C for 24 hours. The resultingS. aureusisolates were counted and classified using Gram staining and biochemical tests. The counts among the 3 periods and the groups were analyzed by Kruskal-Wallis and Dunn tests (α= 5%). Commercial paper disks containing widely prescribed antimicrobial agents (β-lactams, macrolides, clindamycin, and vancomycin) were used to perform the antimicrobial susceptibility tests.

Results.

An increase in the number of microorganisms was observed during clinical procedures (P< .05). The highest bacterial resistance rates were observed for theβ-lactam group. All isolated strains were sensitive to vancomycin, and 2% of them were resistant to methicillin.

Conclusions.

Clinical procedures increased the number and proportion of antimicrobial-resistantS. aureusisolates dispersed in a dental clinical environment. The present study highlights the need to establish strategies to prevent emergence of drug-resistant bacterial strains in dental settings.

Detection of oral streptococci in dental unit water lines after therapy with air turbine handpiece: biological fluid retraction more frequent than expected

AIM

Oral streptococci detected in water from dental unit water lines (DUWLs) are a surrogate marker of patients' biological fluid retraction during therapy. We investigated oral streptococci detection rate in DUWLs in a representative sample of private offices in real-life conditions.

MATERIALS & METHODS

Samples of nondisinfected water (100 ml) were collected from the DUWL designated for the air turbine handpiece in 81 dental units, immediately after dental treatment of patients with extensive air turbine handpiece use. Water was filtered and plated on a selective medium for oral streptococci and, morphologically, typical colonies of oral streptococci were counted. The lowest detection limit was 0.01 CFU/ml.

RESULTS

The oral streptococci detection rate was 72% (95% CI: 62-81%), with a mean level of 0.7 CFU/ml. Oral streptococci detection was not affected by handpiece age or dental treatment type, but was associated with dental unit age.

CONCLUSION

Biological fluid retraction into DUWLs during patient treatment and, possibly, the risk for patient-to-patient blood- or air-borne pathogen transmission are more frequent than expected.

[Evaluation of surface disinfectants utilized in dentistry]

Surface disinfection is a procedure carried out on the external parts of the dental equipment as well as on other items of the dental office. The aim of this study was to analyze the efficacy of 4 surface disinfectants utilized in dentistry: 77 degrees GL alcohol, phenolic compound (Duplofen), iodophor (PVP-I) and 77 degrees GL alcohol with 5% of chlorhexidine. Four surfaces of the equipment were analyzed in the study (the carter, the washbasin for hand-washing, the headrest of the chair and the external surface of the reflector), and the spray-wipe-spray procedure was carried out. From each surface, samples were collected by means of surface plates containing Mitis Salivarius bacitracin sucrose agar, Sabouraud Dextrose agar with chloramphenicol, MacConkey agar and blood agar, for counting mutans streptococci, Candida yeasts, gram-negative bacteria and total microorganisms, respectively (ufc/plate). The results were statistically analyzed by means of the Student's t test in order to compare the mean ufc/plate values. The most effective disinfectant was 77 degrees GL alcohol with 5% of chlorhexidine, mainly against gram-positive bacteria. Iodophor and phenolic compound were also effective in microbial reduction. 77 degrees GL alcohol was the least effective product - however, although it is not considered as a surface disinfectant, it produced, in this study, statistically significant microbial reduction after the disinfecting procedure.