Potential for nosocomial transmission ofEnterococcus faecalisfrom surfaces in dental operatories

Development and validation of an instrument to assess adherence to occupational health protocols in dentistry

OBJECTIVES

The purpose of this study was the creation and validation of an instrument to evaluate adherence to occupational health protocols used in dentistry that arise from official regulations and international recommendations on infection control, biosafety, and occupational health in dentistry. Additionally, in May 2017 the effectiveness of the instrument was documented within the dental care clinics in the postgraduate area.

METHODS

The instrument was developed based on constructs of occupational health, infection control, and biosafety in dentistry, made up of 21 indicators of 5 dimensions called protocols. Using direct observation through 35 measurements during 1 week, adherence to occupational health protocols was evaluated in postgraduate residents within the clinical sections of endodontics/pediatric dentistry, periodontics, prosthodontics, and orthodontics.

RESULTS

The instrument presents an index of 0.88 in Cronbach's alpha analysis. There is a 34.4% adherence within the postgraduate dental clinic to the proposed occupational health protocols. The protocol with the highest adherence at 41.1% was the personal protection protocol. The periodontics section had a 52.9% observance of the proposed protocols and had the highest adherence to occupational health protocols.

CONCLUSIONS

The proposed instrument is valid and reliable to evaluate adherence to the proposed occupational health protocols within dental care clinics. Dental clinics must be inspected and evaluated to ensure adherence to infection control, biosafety, and occupational health protocols within routine dental practice.

Comparison of genotypes, antimicrobial resistance and virulence profiles of oral and non oral Enterococcus faecalis from Brazil, Japan and the United Kingdom

OBJECTIVES

To determine whether phenotypic and genotypic differences amongst isolates ofEnterococcus faecalis relate to geographical and clinical origin.

METHODS

E. faecalis from primary endodontic infections in Brazilian patients (n = 20), oral infections in UK patients (n = 10), and non-oral infections in Japanese patients (n = 9) were studied. In addition, 20 environmental vancomycin resistant Enterococcus faecalis (VRE) isolates from a UK hospital were analysed. For all isolates, polymerase chain reaction (PCR) was used to detect genes associated with antibiotic resistance and virulence, whilst randomly amplified polymorphic DNA-PCR (RAPD-PCR) was used to produce molecular profiles.

RESULTS

Gelatinase gene (gelE) was prevalent amongst isolates (77-100%) and for oral isolates, genes of aggregation substances (agg), immune evasion protein (esp), cytolysin (cylB), tetracycline resistance (tetM; tetL) and erythromycin resistance (ermB) were detected to varying extent. Japanese non-oral isolates had a similar genetic profile to oral isolates, but with higher prevalence of ermB and cylB. All VRE isolates were positive for gelE, esp, agg, vanA, ermB and tetM, 95% were positive for cylB and 17% positive for tetL. All isolates were negative for ermA, asa373 vanB, vanC1 and vanC2/3. RAPD-PCR revealed clustering of VRE isolates.

CONCLUSIONS

RAPD-PCR analysis revealed extensive genetic variability among the tested isolates. Oral isolates carried antibiotic resistance genes for tetracycline and whilst they possessed genes that could contribute to pathogenicity, these were detected at lower incidence compared with non-oral and VRE isolates. RAPD-PCR proved to be a useful approach to elucidate relatedness of disparate isolates.

In mixed biofilms Enterococcus faecalis benefits from a calcium hydroxide challenge and culturing

AIM

To evaluate the fate of Enterococcus faecalis in dual-species and multispecies biofilms after treatment with calcium hydroxide (Ca(OH)₂ ).

METHODOLOGY

Biofilms were cultured from laboratory strains of E. faecalis and Pseudomonas aeruginosa, or from microbiota retrieved from primary root canal infections. The biofilms were then treated with Ca(OH)₂ . The proportion of E. faecalis and P. aeruginosa and their susceptibility to disinfection were evaluated in a viability assay. In the mixed-species assay, the presence and proportions of E. faecalis before and after Ca(OH)₂ treatment were evaluated with a quantitative polymerase chain reaction assay. Groups were compared using Mann-Whitney U-test and Student's t-tests. An α <0.05 was considered statistically significant.

RESULTS

After Ca(OH)₂ treatment in dual-species biofilms, the proportion of E. faecalis had increased (P < 0.001), whereas the total number of CFUs per biofilm was equal. Enterococcus faecalis was equally susceptible to disinfection by sodium hypochlorite (NaOCl) or by chlorhexidine. Pseudomonas aeruginosa had become more susceptible to NaOCl disinfection. The root canal isolates contained no detectable amounts of E. faecalis. After biofilm culturing or Ca(OH)₂ treatment, it appeared that E. faecalis must have been present in 5 of 6 (83%) root canal samples.

CONCLUSIONS

Calcium hydroxide favours the population of E. faecalis in a dual-species biofilm. Culturing multispecies root canal isolates makes E. faecalis detectable. E. faecalis was often present in primary endodontic infections, albeit in low numbers.

The origin of endodontic Enterococcus faecalis explored by comparison of virulence factor patterns and antibiotic resistance to that of isolates from stool samples, blood cultures and food

AIM

To elucidate the origin of Enterococcus faecalis isolated from secondary root canal infections and the possibility for a foodborne transmission by comparing them to strains recovered from food, blood and stool regarding putative virulence factors and antibiotic susceptibility profiles, where strains from common origin were hypothesized to harbour similar characteristics.

METHODOLOGY

A total of 108 E. faecalis strains recovered in the county of Stockholm, Sweden, were screened using PCR for putative virulence factors esp, cylA, gelE/gelatinase-negative phenotype (ef1841/fsrC), efaA, ace and asa1. The minimum inhibitory concentration (MIC) for ampicillin, piperacillin-tazobactam, imipenem, gentamicin, vancomycin, ciprofloxacin and linezolid was determined using the agar dilution method.

RESULTS

Next to strains from blood, the food isolates presented the highest average number of virulence determinants and were frequently enriched with asa1 coding for aggregation substance. None of the endodontic strains carried cylA, and the gelatinase-negative phenotype caused by a deletion dominated the group. Altogether, the most prevalent genes were gelE, efaA and ace, and a combination of them was equally present in approximately 80% of the strains from food, stool and root canals in comparison with 43.3% of the blood isolates. High-level resistance to ciprofloxacin and gentamicin was observed in 30% of the blood isolates, whereas the isolates from other origins, with single exceptions, were susceptible to all tested antibiotics.

CONCLUSIONS

Evidence for a foodborne transmission, explaining the high reported prevalence of E. faecalis in root filled teeth, could not be determined based on the similarities in virulence factor patterns and antibiotic susceptibility. The only linkage between isolates from food and root canals consisted of a shared common combination of the genes gelE, efaA and ace. The high occurrence of putative virulence traits in food isolates questions the safety of E. faecalis in food products.