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Oral endotoxin in healthy adults
LETTERS TO THE EDITOR
Oral endotoxin in healthy adults
In reply:
To the editor: I read with interest the article by Leenstra et al., Oral endotoxin in healthy adults (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;82:637-43). In the introductory section of the article these authors quote the historic data from the literature on the oral carriage of aerobic gram-negative bacilli (AGNB), which states that these organisms are "abnormal" and are uncommon in the oral cavity of healthy persons. Obviously, the data they quote are from Western studies and agree with our findings from the United Kingdom that we reported some years ago. 1,2 In the last few years, we have conducted a series of clinical epidemiologic studies in cohorts in Southem China to ascertain the oral carriage of AGNR. To our surprise these studies have demonstrated, unequivocally, that 25% to 40% of healthy children and adults carry AGNR in the oral cavity 3,4 as opposed to 10% to 15% carriage rate in the West, 2 a fact that needs to be borne in mind by future investigators in this field. These findings also raise other questions, such as the level of oral endotoxin in healthy persons with a high oral prevalence of AGNR. Studies conducted in Asian cohorts are therefore needed to make general statements on oral endotoxin levels that are globally applicable. Professor L.P. Samaranayake Professor in Oral Microbiology Faculty of Dentistry University of Hong Kong 34 Hospital Road Hong Kong REFERENCES
1. SamaranayakeLP, LambAB, LameyP-J, MacFarlaneTW. Oral carriage of Candidaspeciesand coliformsin patients with burning mouth syndrome. J Oral Path Med 1989;18:233-5. 2. SedgleyCM, Samm'anayakeLE Oral and oropharyngealprevalence of Enterobacteriaceae in humans: a review. J Oral Path Med 1994;23:104-13. 3. SedgleyCM, SamaranayakeLE The oral prevalenceof aerobic and facultatively anaerobic gram-negativerods and yeasts in Hong KongChinese. Arch Oral Biol 1994;39:459-66. 4. Sedgley CM, Chu CS, Lo ECM, SamaranayakeLR The oral prevalence of aerobic and facultativelyanaerobicgram-negative rods and yeasts in semi-reclusehuman vegetarians.Arch Oral Biol 1996;41:307-9.
We appreciate Dr. Samaranayake's positive contribution to the issue of oropharyngeal carriage of aerobic gram-negative bacilli (AGNB) in healthy adults. Recent work from Dr. Samaranayake's group suggests a significant difference in AGNB carriage between Western and Asian cohorts. Crucial in this discussion is the appreciation of the difference between carriage and transient presence of potential pathogens. Carriage or carrier state exists when the same strain of a potential pathogen is isolated from at least two consecutive surveillance samples in any concentration over a period of at least 1 week. 1 If one surveillance sample is positive for a potential pathogen that differs from previous isolates, the person is considered to have acquired a potential pathogen. Thus carriage refers to the persistent presence of a micro-organism in the oropharynx. An acquired potential pathogen is only transiently present in an otherwise healthy host. Acquisition rather than carriage may explain the high oral AGNB prevalence rates of 33.3% and 41.7% in Buddhist monks, nuns, and Chinese people living in Hong Kong, respectively. In both studies only one oral rinse sample was obtained, making a distinction between acquisition and carriage in healthy persons impossible. Second, the AGNB exposure via raw food including tomatoes, salads, and vegetables is higher than from cooked food. 2 Third, acquired AGNB are in general cleared from the healthy oropharynx within 3 hours, making the sampling time in relation to eating and drinking an important variable. Dr. Samaranayake's observation that morning samples yielded a significantly higher prevalence of AGNB than afternoon samples (67% versus 33%) whereas there was no difference in yeast carriage, support the third argument. These discrepancies do not occur in patients. No differences in AGNB prevalences were observed between single culture and multiple culture surveys obtained from the oropharynx of diseased persons) This study also showed that AGNB exposure was not an adequate explanation for the high AGNB carriage in critically ill patients. They hypothesized that the oropharyngeal clearance of AGNB is impaired in the critically ill because of the severity of underlying disease. Recently, scoring methods became available to estimate the degree of severity of underlying disease. A recent study in medical intensive care unit patients reports that one third of the population with a mean of 13 _+4.6 SAPS carried AGNB in the oropharynx. 4 Moreover, oral
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
August 1997 113
Oral endotoxin in healthy adults
In reply:
To the editor: I read with interest the article by Leenstra et al., Oral endotoxin in healthy adults (Oral Surg Oral Med Oral Pathol Oral Radiol Endod 1996;82:637-43). In the introductory section of the article these authors quote the historic data from the literature on the oral carriage of aerobic gram-negative bacilli (AGNB), which states that these organisms are "abnormal" and are uncommon in the oral cavity of healthy persons. Obviously, the data they quote are from Western studies and agree with our findings from the United Kingdom that we reported some years ago. 1,2 In the last few years, we have conducted a series of clinical epidemiologic studies in cohorts in Southem China to ascertain the oral carriage of AGNR. To our surprise these studies have demonstrated, unequivocally, that 25% to 40% of healthy children and adults carry AGNR in the oral cavity 3,4 as opposed to 10% to 15% carriage rate in the West, 2 a fact that needs to be borne in mind by future investigators in this field. These findings also raise other questions, such as the level of oral endotoxin in healthy persons with a high oral prevalence of AGNR. Studies conducted in Asian cohorts are therefore needed to make general statements on oral endotoxin levels that are globally applicable. Professor L.P. Samaranayake Professor in Oral Microbiology Faculty of Dentistry University of Hong Kong 34 Hospital Road Hong Kong REFERENCES
1. SamaranayakeLP, LambAB, LameyP-J, MacFarlaneTW. Oral carriage of Candidaspeciesand coliformsin patients with burning mouth syndrome. J Oral Path Med 1989;18:233-5. 2. SedgleyCM, Samm'anayakeLE Oral and oropharyngealprevalence of Enterobacteriaceae in humans: a review. J Oral Path Med 1994;23:104-13. 3. SedgleyCM, SamaranayakeLE The oral prevalenceof aerobic and facultatively anaerobic gram-negativerods and yeasts in Hong KongChinese. Arch Oral Biol 1994;39:459-66. 4. Sedgley CM, Chu CS, Lo ECM, SamaranayakeLR The oral prevalence of aerobic and facultativelyanaerobicgram-negative rods and yeasts in semi-reclusehuman vegetarians.Arch Oral Biol 1996;41:307-9.
We appreciate Dr. Samaranayake's positive contribution to the issue of oropharyngeal carriage of aerobic gram-negative bacilli (AGNB) in healthy adults. Recent work from Dr. Samaranayake's group suggests a significant difference in AGNB carriage between Western and Asian cohorts. Crucial in this discussion is the appreciation of the difference between carriage and transient presence of potential pathogens. Carriage or carrier state exists when the same strain of a potential pathogen is isolated from at least two consecutive surveillance samples in any concentration over a period of at least 1 week. 1 If one surveillance sample is positive for a potential pathogen that differs from previous isolates, the person is considered to have acquired a potential pathogen. Thus carriage refers to the persistent presence of a micro-organism in the oropharynx. An acquired potential pathogen is only transiently present in an otherwise healthy host. Acquisition rather than carriage may explain the high oral AGNB prevalence rates of 33.3% and 41.7% in Buddhist monks, nuns, and Chinese people living in Hong Kong, respectively. In both studies only one oral rinse sample was obtained, making a distinction between acquisition and carriage in healthy persons impossible. Second, the AGNB exposure via raw food including tomatoes, salads, and vegetables is higher than from cooked food. 2 Third, acquired AGNB are in general cleared from the healthy oropharynx within 3 hours, making the sampling time in relation to eating and drinking an important variable. Dr. Samaranayake's observation that morning samples yielded a significantly higher prevalence of AGNB than afternoon samples (67% versus 33%) whereas there was no difference in yeast carriage, support the third argument. These discrepancies do not occur in patients. No differences in AGNB prevalences were observed between single culture and multiple culture surveys obtained from the oropharynx of diseased persons) This study also showed that AGNB exposure was not an adequate explanation for the high AGNB carriage in critically ill patients. They hypothesized that the oropharyngeal clearance of AGNB is impaired in the critically ill because of the severity of underlying disease. Recently, scoring methods became available to estimate the degree of severity of underlying disease. A recent study in medical intensive care unit patients reports that one third of the population with a mean of 13 _+4.6 SAPS carried AGNB in the oropharynx. 4 Moreover, oral
ORAL SURGERY ORAL MEDICINE ORAL PATHOLOGY
August 1997 113