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

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114 Letters to the editor

ORAL SURGERY ORAL MEDICINEORAL PATHOLOGY August 1997

AGNB carriage rates returned to control levels after Completion of radiotherapy. 5 Finally, advanced age was suggested by Samaranayake's group to explain the differences observed in the oral prevalences of AGNB amongst the Asian cohorts compared with the Western studies. Age as an independent risk factor has never been shown to promote AGNB carriage. 1 This is in line with Dr. Samaranayake's findingthat there was no difference in AGNB prevalence between groups aged 15 to 29 years and over 50 years. A confounding factor is that chronic and acute underlying disease is often associated with increased age. In conclusion, further studies in homogeneous subsets of persons using conformity in both definitions and methods rather than expensive epidemiologic typing systems to correlate bacteria in oral rinses with those in suspected source samples may clarify the discrepancies observed between AGNB carriage in healthy persons from those two continents with different cultures including diet.

cian extracts a tooth that exhibits a radicular cyst at its apex and leaves the cyst in place, then by definition that cyst is a residual radicular cyst, from the time of extraction to its eventual resolution or enucleation. I realize that he is really referring to a putative residual radicular cyst that is removed months or even years after a tooth (or teeth) in the region was extracted. Our knowledge of the pathogenesis of such lesions is very weak. As Dr. Walton states, there is a lack of longitudinal studies in the literature concerning radicular cysts that have failed to resolve after appropriate endodontic treatment or extraction of the associated teeth. Probably most such cysts do in fact resolve without incident. David G. Gardner, DDS, M S D

Professor, University of Colorado School of Dentistry, Denver, CO 80262 In reply:

T. S. Leenstra J. J. M. van Saene H. K. E van Saene M. V. Martin

University Hospital and University of Groningen and University of Liverpool REFERENCES

1. Spijkervet FKL, van Saene HKF, Panders AK, et al. Colonizationindex of the oral cavity:a noveltechniquefor monitoring colonization defense. Microbial Ecologyin Health and Disease 1989;2:145-51. 2. RemingtonJS, SchimpffSC. Please don't eat the salads. New Engl J Med 1981;304:433-5. 3. Johanson WG, Pierce AK, Sanford JR Changing pharyngeal bacterial flora of hospitalized patients: emergenceof gram-negative bacilli. New Engl J Med 1969;281:1137-40. 4. Garrouste-Orgeas M, Marie O, Rouveau M, et al. Secondary carriage with multi-resistant Acinetobacter baumannii and Klebsiella pneumoniae in an adult ICU population:relationship with nosocomial infections and mortality. J Hosp Infect 1996;34:279-89. 5. Makkonen TA, Borthen L, Heimdahl A, et al. Oropharyngeal colonizationwith fungi and gram-negativerods in patients treated with radiotherapyof the head and neck. Br J Oral Maxillofac Surg 1989;27:334-40.

Residual cysts To the editor:

In reply to Dr. Walton's editorial (Oral Surg Oral Med Oral Pathol Oral Radiol Endo 1996;82:471) in which he questions the existence of residual radicular Cysts, it seems obvious that they must occur. If a clini-

We appreciate being given an opportunity to respond to the concerns expressed by Dr. Marilyn Moffat, President of the American Physical Therapy Association. Dr. Moffat takes us to task for having conducted a strict review of the literature in which we included only those studies that used control groups. We were surprised at Dr. Moffat's comments, as our mandate was to present "the results from rigorous and methodologically sound clinical trials and studies published in peerreviewed journals." This was explained very clearly by James Lipton in the introduction to this series of articles, which were part of the Health Technology Assessment Conference on Management of Temporomandibular Disorders (TMD), sponsored by the National Institute of Dental Research and the National Institutes of Health Office of Medical Applications of Research. Dr. Moffat states that our assessment of individual modalities is "misguided." She also states that we have drawn "an erroneous conclusion" from the work of Elaine Chapman, 1 Director of the School of Physical and Occupational Therapy at the Universit6 de Montr6al. On the contrary, Dr. Chapman also reviewed physical modalities individually, in exactly the same manner as we. Furthermore, she concluded "Thus, there is a clear need for randomized, controlled trials to address this important question, and these should include a control group not receiving any other physical modality" [our emphasis]. Dr. Chapman also writes "It was concluded that, apart from a few exceptions and in a few types of disorders, existing evidence does not support the use of these modalities in long-term pain