Oral Prevalence of Aerobic and Facultatively Anaerobic Gram-Negative Rods and Yeasts in Hospitalised Patients

Effect of oral hygiene interventions on opportunistic pathogens in patients after stroke

BACKGROUND

Despite the role of the oral cavity as a reservoir of opportunistic pathogens for infection in patients following stroke, the evaluation of the effects of oral hygiene interventions has been largely neglected.

METHODS

This randomized clinical trial included 102 patients undergoing hospital-based rehabilitation for stroke. Patients were randomized to one of 3 groups: oral hygiene instruction (OHI) only; OHI and 0.2% chlorhexidine mouth rinse twice daily; or OHI, 0.2% chlorhexidine mouth rinse twice daily, and assisted brushing twice weekly. Oral samples were obtained at baseline and after 3 weeks for detection of Staphylococcus aureus, aerobic and facultatively anaerobic gram-negative bacilli, and yeasts.

RESULTS

Almost three-quarters (72.8%) of the patients harbored oral anaerobic gram-negative bacilli at baseline, and more than half had detectable S aureus (56.8%) and yeasts (59.3%). Percentage frequencies and viable counts of pathogens remained relatively stable during the course of the clinical trial, and no significant differences were observed among the 3 patient groups.

CONCLUSIONS

In our study cohort, there was no significant difference in the effectiveness of the 3 different oral hygiene interventions on the prevalence or viable counts of oral opportunistic pathogens.

Effect of oral bacteria on growth and survival of Candida albicans biofilms

The purpose of this study was to evaluate the effect of eight aerobic and anaerobic oral commensal bacterial species on in vitro Candida albicans biofilm development. A single isolate of C. albicans 2560 g, and eight different species of oral bacteria comprising, Actinomyces israelii, Lactobacillus acidophilus, Prevotella nigrescens, Porphyromonas gingivalis, Pseudomonas aeruginosa, Escherichia coli, Streptococcus mutans, and Streptococcus intermedius were studied using an in vitro biofilm assay. Biofilm formation was quantified in terms of the ability of Candida to grow on polystyrene plastic surfaces co-cultured with the foregoing bacteria. A viable cell count was used to quantify the sessile yeast growth and scanning electron microscopy was employed to confirm and visualize biofilm formation. Co-culture with differing concentrations of bacteria had variable effects on Candida biofilm formation. Co-culture with the highest concentrations of each of the foregoing bacteria resulted in a consistent reduction in the yeast counts in the candidal biofilm (P<0.05), except for L. acidophilus, S. mutans, and, S. intermedius co-cultures. Further, on regression analysis a significant negative correlation between the co-culture concentration of either P. gingivalis or E. coli and viable yeast counts in the biofilm was noted (P<0.05) although this was not evident for the other bacterial species. Taken together, our data indicate that, quantitative and qualitative nature of the bacteria modulate C. albicans biofilm formation in mixed species environments such as the oral cavity.

Oral colonisation by aerobic and facultatively anaerobic Gram-negative rods and yeast in Tibetans living in Lhasa

Sample groups of children (n=50) and adults (n=38) were selected from pools of 207 children, (11-13-year olds from two primary schools) and 94 adults (25-44-year olds from four governmental agencies) who were the subjects of an oral health survey among Tibetans living in Lhasa, Tibet Autonomous Region. Mean ages of the study groups of children (38% females) and adults (61% females) were 11.6+/-0.9 and 37.1+/-6.1 years, respectively. All had lived in Tibet since birth. Oral rinse samples were selective cultured to isolate, quantify and speciate aerobic and facultatively anaerobic Gram-negative rods (using the API 20E kit) and yeasts (using API 20C AUX and API ZYM kits). For children, the isolation rates for oral coliform bacteria and yeasts were 84 and 14%, respectively, for adults, the respective rates were 26 and 40%. The corresponding quantities of coliforms/yeasts for children and adults were 0.4+/-1.6 x 10(3)c.f.u./15.8+/-72.3 and 0.2+/-0.6 x 10(3)c.f.u./57.2+/-137.5c.f.u. per millilitre oral rinse, respectively. Aerobic and facultatively anaerobic Gram-negative rods and Stenotrophomonas maltophilia, a free-living saprophytic and ubiquitous bacterial species of wide geographic distribution, were significantly more frequently recovered from the children's oral rinses. The isolation rates of facultatively anaerobic Gram-negative rods in adults and yeasts in both groups were similar to those found in similar cohorts from southern China in earlier studies. Randomly amplified polymeric DNA analysis showed that the S. maltophilia spp. isolated from children were of several different clonal types and were school specific. This study shows that the colonisation rate of facultatively anaerobic Gram-negative rods in adults and yeasts in both groups are similar to those in populations living at lower altitudes, the native young, urban Tibetans appear to exhibit a high oral carriage rate of S. maltophilia spp.

Antimicrobial susceptibility of oral isolates of Enterobacter cloacae and Klebsiella pneumoniae from a southern Chinese population

The antibiotic susceptibilities of 59 Enterobacter cloacae and 39 Klebsiella pneumoniae human oral isolates collected from a southern Chinese population in Hong Kong were investigated for their susceptibility to eight antibiotics: ampicillin, cephalothin, cefuroxime, ceftazidime, ciprofloxacin, gentamicin, tetracycline and trimethoprim/sulfamethoxazole using the E-Test method for direct quantification of minimum inhibitory concentrations. Most strains were sensitive to all antibiotics except ampicillin and cephalothin. Ampicillin resistance was exhibited by 82% of K. pneumoniae and 69% of E. cloacae isolates. Eighty-eight percent of E. cloacae isolates were resistant to cephalothin. Several strains fell within the intermediate category of sensitivity for ampicillin (E. cloacae and K. pneumoniae), cefuroxime (E. cloacae) and tetracycline (K. pneumoniae). Comparison with other Hong Kong data suggests that resistance rates to cefuroxime, ceftazidime, ciprofloxacin, gentamicin, tetracycline and trimethoprim/sulfamethoxazole exhibited by the oral isolates are generally lower than in enterobacters and Klebsiella spp. isolated from urine, skin and soft tissues in Hong Kong populations.

A 4-year longitudinal study of the oral prevalence of enteric gram-negative rods and yeasts in Chinese children

A 4-year longitudinal study of the oral prevalence of enteric gram-negative rods and yeasts in 116 Chinese primary school children in Hong Kong was conducted. The oral prevalence of enteric gram-negative rods for each consecutive year was 25.3%, 37.0%, 24.0% and 25.8% respectively, with a weighted mean of 27.9%. Enterobacteriaceae, which comprised 57% of all enteric gram-negative rods, were more common in children with no caries experience. The oral prevalence of yeasts for each consecutive year was 7.7%, 12.0%, 14.4% and 15.5% respectively, with a weighted mean of 12.5%. Candida albicans comprised 84% of all yeasts isolated. Oral yeast carriage was significantly associated with caries prevalence. While the oral prevalence of enteric gram-negative rods in primary school children in Hong Kong may be higher than in other parts of the world, repeated isolation of either enteric gram-negative rods or Candida spp. from individual children over the 4-year study period was rare, suggesting that carriage of these organisms is transient.

The effect of oral commensal bacteria on candidal adhesion to denture acrylic surfaces. An in vitro study

The effect of four different species of oral bacteria (Streptococci (X 2); Escherichia; Porphyromonas) on the adhesion of Candida albicans and Candida krusei to denture acrylic surfaces was studied using a previously described in vitro adhesion assay. Clear acrylic strips immersed in known concentrations of bacterial suspensions and incubated for 45 min to 1 h, at 37 degrees C, were transferred to yeast suspensions of known concentrations and incubated for a similar period, and the adherent yeasts were quantified using an image analysis system. Pre-exposure to different bacterial concentrations resulted in suppression of candidal adhesion to varying degrees. Of three selected concentrations, exposure to the highest bacterial concentration (10(6) organisms/ml) resulted in a consistent reduction in candidal adhesion, except for E. coli-C. albicans and S. salivarius-C. albicans combinations. Candidal adhesion was significantly reduced on pre-exposure to S. sanguis and P. gingivalis, but not E. coli. There were also significant differences in relative adhesion between C. albicans and C. krusei. Taken together, these results indicate that the adhesion of yeasts to acrylic strips is modulated both by the quantity and the quality of pre-existing bacterial flora on acrylic surfaces.

The oral prevalence of aerobic and facultatively anaerobic gram-negative rods and yeasts in semi-recluse human vegetarians

Limited data exist on the oral ecology of vegetarians. Hence the dental and periodontal status, and the oral prevalence of aerobic and facultatively anaerobic Gram-negative rods (AGNR) and yeasts, were studied in 36 semi-recluse, vegetarian, Buddhist monks and nuns in Hong Kong. The oral prevalence of AGNR and yeasts was 61.1% and 33.3%. There was no correlation between the prevalence of AGNR and/or yeasts and the incidence of carious or filled teeth and the health status of the periodontium. Rather, the results of this study combined with those of previous studies suggest that increasing age and the consumption of food prepared in communal kitchens might be more important contributory factors in the oral prevalence of AGNR than the nature of the diet itself or the health of the dentition and periodontium.