[Halitosis management by the general dental practitioner- results of an International Consensus Workshop*]. / Halitosismanagement für die Zahnarztpraxis. Ergebnisse eines internationalen Konsunsus-Workshops*.

Clinical investigations on patients suffering from halitosis clearly reveal that in the vast majority of cases the source for an offensive breath odor can be found within the oral cavity (90%). Based on these studies, the main sources for intra-oral halitosis where tongue coating, gingivitis/periodontitis and a combination of the two. Thus, it is perfectly logical that general dental practitioners (GDPs) should be able to manage intra-oral halitosis under the conditions found in a normal dental practice. However, GDPs who are interested in diagnosing and treating halitosis are challenged to incorporate scientifically based strategies for use in their clinics. Therefore, the present paper summarizes the results of a consensus workshop of international authorities held with the aim to reach a consensus on general guidelines on how to assess and diagnose patients’ breath odor concerns and general guidelines on regimens for the treatment of halitosis.

Microbial alcohol-conferred hemolysis is a late response to alcohol stress.

We have reported previously that growth on alcohol vapors confers hemolytic properties on certain yeast species and strains ['microbial alcohol-conferred hemolysis' (MACH)]. In a recent study, we analyzed the genetic basis of MACH in Saccharomyces cerevisiae using the EUROSCARF mutant collection. The data suggested that intact mitochondrial and respiratory chain functions are critical for the observed alcohol-mediated hemolysis. We proposed that the uncontrolled cellular uptake of alcohol results in yeast 'hyper-respiration', leading to elaboration of hemolytic molecules such as hydrogen peroxide and lytic lipids. In the current study, we have further analyzed the molecular mechanisms involved in the MACH phenomenon in S. cerevisiae, using DNA microarrays. The patterns of regulation were confirmed by quantitative reverse transcriptase PCR. The results presented here lend further support to this hypothesis, based on upregulation of the genes responsible for coping with vast amounts of hydrogen peroxide produced as a byproduct of excessive oxidation of alcohol. These results, taken together, show that alcohol-mediated hemolysis in yeast appears to be related to the overproduction of hemolytic byproducts, particularly hydrogen peroxide, which accumulates during long-term exposure of S. cerevisiae to both ethanol and n-butanol.

Global gene expression in Staphylococcus aureus following exposure to alcohol.

It was recently shown that, as in yeast, alcohols selectively increase the hemolytic properties of certain staphylococci strains. This phenomenon has been called 'microbial alcohol-conferred hemolysis'(MACH). Here we present the changes in gene expression by Staphylococcus aureus 8325-4, in response to ethanol. Ethanol upregulated the expression of multiple toxins and increase the pathogen potential of S. aureus strain 8325-4. Ethanol also increased the level of genes considered necessary for production and viability of biofilm, such as: icaAD, sdrDE, pyr, and ure. Increased urease activity appeared to be an important factor in the ethanol response along with macromolecule repair mechanisms. Oxidative-stress responses, such as increased expression of sodA1, sodA2 and upregulation of zinc-containing alcohol dehydrogenase, alcohol-acetaldehyde dehydrogenase (adhE) and two aldehyde dehydrogenases (aldA1, aldA2), which can generate more reducing power, were also induced. Upregulation of fatty acid metabolism appears to be important in enabling the bacteria to handle excess amounts of ethanol which ultimately may lead to synthesis of lytic lypids. The patterns of regulation were confirmed by quantitive reverse transcriptase PCR (QRT-PCR). These results, taken together, suggest that exposure to ethanol increases pathogenic traits and induce oxidative-stress responses.

Effect of alcohol on bacterial hemolysis.

Hemolysis of blood agar is broadly used as a diagnostic tool for identifying and studying pathogenic microorganisms. We have recently shown that alcohol vapors can confer hemolytic properties on otherwise nonhemolytic fungi (microbial alcohol-conferred hemolysis; MACH). Until now, this phenomenon has been found in various yeast strains and other fungi, but only in a few bacterial species (e.g., staphylococci). In the current study we (1) determined the extent of the above phenomenon in various gram-positive and gram-negative laboratory bacterial strains and in clinical bacterial isolates, (2) validated the observed hemolysis using a quantitative technique, and (3) provided evidence that the observed alcohol-mediated hemolysis may, at least in part, be related to synthesis of hemolytic lipids.

Alcohol-conferred hemolysis in yeast is a consequence of increased respiratory burden.

We have previously reported that growth on alcohol vapors confers hemolytic properties on certain yeast species and strains ('microbial alcohol conferred hemolysis'; MACH). Here, a Saccharomyces cerevisiae deletion library consisting of c. 4800 clones was screened for MACH mutants in the presence of n-butanol vapors; 136 mutants were MACH-negative, and 325 exhibited reduced hemolysis and/or growth. Of the MACH-negative mutants, 35.3% were affected in mitochondrial-related genes. The data suggest that intact mitochondrial and respiratory chain functions are critical for the observed MACH phenomenon. We propose that the uncontrolled cellular uptake of alcohol results in yeast 'hyper-respiration', leading to elaboration of hemolytic molecules such as hydrogen peroxide and hemolysis-causing lipids. To support this premise, we showed that: (1) exogenous catalase and glutathione reduce alcohol-conferred hemolysis in S. cerevisiae BY4741 and Candida tropicalis 59445; (2) C. tropicalis produces hydrogen peroxide following growth on ethanol and n-butanol, as shown using xylenol orange; and (3) a lysophospholipid-containing lipid extract from alcohol-grown C. tropicalis specifically causes hemolysis.

Alcohol increases hemolysis by staphylococci.

It was recently found that alcohols can confer hemolytic properties on certain species of yeast. Here, it is reported that alcohol can promote hemolysis by various species of staphylococci, including strains of Staphylococcus aureus, Staphylococcus epidermidis and Staphylococcus hominis. In order to study this novel phenomenon in S. aureus and S. epidermidis, strains that exhibit this phenomenon (e.g. S. aureus 8325-4, COL, SH1000, S. epidermidis), as compared with strains that exhibited little alcohol-enhanced hemolysis (e.g. S. aureus 8325-4 DeltaTRAP, RN6911) were examined. Both ethanol and n-butanol caused upregulation of the virulence regulator-RNAIII, with a concomitant increase in the production of alpha, beta and gamma-hemolysins in strain 8325-4. In S. aureus COL and SH1000, there was an increase in RNAIII but no change in transcription levels of alpha, beta and gamma hemolysins. Staphylococcus epidermidis stain sofi exhibited increased RNAIII and beta hemolysin production. Staphylococcus aureus mutant strains (8325-4 DeltaTRAP and RN6911) showed no change in the transcription level of the RNAIII regulator and the above hemolysins. Increased hemolysis in S. aureus COL, SH1000 and mutant strains may be caused by other hemolysins (not regulated by RNAIII) or through other mechanisms such as hyperoxidation or cytotoxic lipids.

Microbial adhesion to hydrocarbons: twenty-five years of doing MATH.

Twenty-five years ago this past autumn, we published a short article entitled 'Adherence of bacteria to hydrocarbons: a simple method for measuring cell-surface hydrophobicity' in Volume 9 of FEMS Microbiology Letters. Together with my Ph.D. supervisors, Eugene Rosenberg and David Gutnick, we proposed a method of measuring bacterial cell surface hydrophobicity based on bacterial adherence to hydrocarbon ('BATH', later known as 'MATH', for microbial adhesion to hydrocarbon). The method became popular soon after it was published, and the paper was, for at least the following decade, the Journal's most cited article. It became an ISI 'citation classic' in 1991. This minireview is a rather personal look at the development of the method and its various modifications and other scientific offspring, with the perspective of a quarter-century.

Assessing the relationship between concentrations of malodor compounds and odor scores from judges.

BACKGROUND: The purpose of this review was to assess the relationship between mean organoleptic scores (using a 0-to-5 scale) and concentrations of putative odorants representative of those thought to be important in oral malodor, as well as to propose a simple model that explains the dose-response curves obtained from a group of odor judges. METHODS: The model assumes that the scale is rooted at the detection threshold (0), the maximum score (5) is fully saturating and the brain and olfactory nervous system can act as a faithful transducer of the state of binding (occupancy) of the smell receptors in the nose. The authors predicted that the response would be exponential or sigmoidal in nature. They tested this using published empirical data based on seven odor judges and eight odor compounds. RESULTS: Analysis of the data by different plotting methods showed the odorants to be significantly different from each other (P < .01 by regression analysis) with regard to thresholds and slopes. The lower the threshold, the stronger the inherent odor of the compound. The greater the slope, the greater the odor power. Volatile sulfur compounds had low smell thresholds and high odor power and were highly volatile, while indole was less volatile but had a very low threshold. Both compounds may be significant in human oral malodor. CONCLUSIONS: The authors found that the organoleptic scale was exponential in practice. These findings imply that when inhibitory agents are tested against odor-generating bacteria, a given percentage inhibition of the volatile compound production rate by a treatment (such as an antimicrobial mouthwash) will result in an equal incremental reduction on the scale, regardless of the starting position on the scale. Understanding the scale enables dental professionals to develop better ways of training, calibrating and standardizing odor judges, along with better ways of designing clinical trials and interpreting data regarding the efficacy of antiodor treatments.

Alcohol-mediated haemolysis in yeast.

Although yeast are generally non-haemolytic, we have found that addition of alcohol vapour confers haemolytic properties on many strains of yeast and other fungi. We have called this phenomenon 'microbial alcohol-conferred haemolysis' (MACH). MACH is species- and strain-specific: whereas all six Candida tropicalis strains tested were haemolytic in the presence of ethanol, none among 10 C. glabrata strains tested exhibited this phenomenon. Among 27 C. albicans strains and 11 Saccharomyces cerevisiae strains tested, ethanol-mediated haemolysis was observed in 11 and 4 strains, respectively. Haemolysis is also dependent on the alcohol moiety: n-butanol and n-pentanol could also confer haemolysis, whereas methanol and 2-propanol did not. Haemolysis was found to be dependent on initial oxidation of the alcohol. Reduced haemolysis was observed in specific alcohol dehydrogenase mutants of both Aspergillus nidulans and S. cerevisiae. MACH was not observed during anaerobic growth, and was reduced in the presence of pararosaniline, an aldehyde scavenger. Results suggest that initial oxidation of the alcohol to the corresponding aldehyde is an essential step in the observed phenomenon.

Halitosis.

Halitosis (oral malodour or breath odour) is a fairly common complaint. Halitosis is most often a consequence of oral bacterial activity, typically from anaerobes. Occasional causes include systemic disease, and some patients have a psychogenic background to the complaint. The management is outlined in this paper.

Saliva secretion and oral flora in prolonged nasogastric tube-fed elderly patients.

BACKGROUND: In a previous study we showed that prolonged nasogastric tube feeding is associated with pathogenic oral flora. OBJECTIVE: To reexamine the impact of prolonged nasogastric tube feeding on the oral microbiota and to explore the salivary flow and composition in elderly patients in long-term care. METHODS: We compared a group of elderly patients fed by nasogastric tube with a control group of elderly patients in long-term care who are fed orally. Bacteriologic studies were performed by culturing samples from the oropharynx. Saliva studies included quantitative and biochemical analysis of basal and stimulated salivary flow. RESULTS: Bacteriologic studies performed in 90 patients revealed a significantly higher prevalence of gram-negative bacteria in nasogastric tube-fed patients (73% vs. 13%, P < 0.001). It is emphasized that Pseudomonas aeruginosa and Klebsiella pneumoniae were commonly and exclusively isolated from the oral flora of the nasogastric tube-fed patients (P < 0.001, P < 0.05). In the saliva studies performed on 23 nasogastric tube-fed and 21 control patients, basal and stimulated salivary flow was not significantly different in the two groups, however the ratio of stimulated to basal flow was reduced in the nasogastric tube-fed group (P < 0.05). Significant differences were also found in the concentrations of sodium, amylase, phosphor and magnesium. Noteworthy was the concentration of uric acid, the main non-enzymatic antioxidant of saliva, which was significantly lower in nasogastric-tube fed patients (P < 0.002). CONCLUSIONS: These findings suggest that prolonged nasogastric tube feeding is associated with pathologic colonization of the oroparynx and with alterations in the saliva that are related to the risk of aspiration pneumonia. Further research is called for, as well as a thorough revision of the existing oral cleansing procedures in these patients.

Pathogenic colonization of oral flora in frail elderly patients fed by nasogastric tube or percutaneous enterogastric tube.

BACKGROUND: Aspiration of infected oropharyngeal content is the main cause of aspiration pneumonia. This complication, mainly related to gram-negative bacteria, threatens percutaneous enterogastric tube as well as nasogastric tube (NGT) fed patients. The objective of this study was to examine the oral microbiota of tuboenterally fed patients and compare it with that of orally fed counterparts. METHODS: Patients were recruited for this study from six nursing and skilled nursing facilities with an overall number of 845 beds. Enrolled were 215 patients: Group 1 consisted of 78 patients on NGT feeding, Group 2 consisted of 57 patients on percutaneous enterogastric tube feeding, and Group 3 consisted of 80 patients fed orally who were from the same facilities. Cultures were performed by sampling the oropharynx of each subject in order to identify gram-negative bacteria and Staphylococcus aureus. RESULTS: A high prevalence of potentially pathogenic isolations was found in tuboenterally fed patients: 81% in Group 1 and 51% in Group 2, as compared with only 17.5% in Group 3 (p <.0001). Pseudomonas aeruginosa was cultured from 31% of the subjects in Group 1 and 10% of Group 2, but in none of Group 3 (p <.001). Klebsiella and Proteus were isolated mainly from the NGT fed patients (p <.003). No correlation was found between the time duration on tube feeding or the presence of residual dentition and pathogenic microbiota. CONCLUSION: This study shows that tuboenteral feeding in elderly patients is associated with pathogenic colonization of the oropharynx. These findings are related to the risk of aspiration pneumonia and are compelling for the reevaluation of current oral cleansing procedures.

A simple technique for the determination of salivary gland hypofunction.

OBJECTIVE: Present volumetric or gravimetric techniques for measuring saliva output are often cumbersome and, therefore, not generally used. In the present study, a simple approach to study the weight loss of a standard hard sugar candy after 3 minutes of passive incubation between tongue dorsum and palate was tested. STUDY DESIGN: Subjects (n = 59), 27 of whom had a subjective complaint of dry mouth and the rest who were healthy control subjects, were tested with this procedure, together with gravimetric measurements of stimulated and unstimulated saliva output from various glands (parotid, submandibular, and sublingual). Correlations between a decrease in candy weight and salivary flow rate were determined for the 2 groups of subjects, taken separately, as well as for the entire subject population, by using the Pearson product moment correlation. RESULTS: In most cases, highly significant associations were found, particularly when comparing candy weight loss with stimulated parotid and submandibular and sublingual saliva. Data were submitted to dichotomous analysis and divided according to salivary flow rate by using a cutoff 0.23 g for candy loss; the sensitivity, specificity, and positive predictive values were 92%, 85%, and 82%, respectively. CONCLUSIONS: The candy weight-loss test is a simple, rapid measure of salivary hypofunction, which correlates with saliva output and reports of subjective dry mouth.