Colonization of dental plaque: A source of nosocomial infections in intensive care unit patients

Objective: To study the dental status and colonization of dental plaque by aerobic pathogens and their relation with nosocomial infections in intensive care unit (ICU) patients. Design: A prospective study in a medical ICU of a university-affiliated hospital. Patients: Consecutive patients admitted to the ICU during a 3-mo period. Interventions: Dental status was assessed by the same investigator using a score adapted from the “Caries-Absent-Occluded” (CAO) index (referred to in the U.S. as DMFT Decayed-Missing-Filled Teeth index). The amount of dental plaque on premolars was assessed using a semiquantitative score. Quantitative cultures of dental plaque, nasal secretions, tracheal aspirates, and urine were done at admission (day 0) and every fifth day until death or discharge. An additional study was done in eight patients to serially compare dental plaque, salivary, and tracheal aspirate cultures during a 2-wk period. Meaurements and Main Results: Fifty-seven patients were included in the main study. Due to the variability in their ICU stay, 29 patients could be examined on day 0 only (group A), 15 patients on days 0 and 5 (group B), and 13 patients on days 0, 5, and 10 (group C). The mean dental CAO score was 16 +/- 8 and did not change during the ICU stay. The dental plaque score was or=to2 in 50% of patients on day 5; and >or=to2 in 90% of patients on day 10. Dental plaque cultures were positive at 103 colony-forming units/mL for aerobic pathogens in 23% of patients on day 0; 39% of patients on day 5; and 46% of patients on day 10. In groups B and C, mean dental plaque score and frequency of plaque colonization increased from days 0 to 5 and from days 5 to 10. A high bacterial concordance was found between dental plaque and tracheal aspirate cultures, and in the additional study, between salivary and dental plaque cultures. Twenty-one patients developed a nosocomial infection in the ICU. Dental plaque colonization on days 0 and 5 was significantly associated with the occurrence of nosocomial pneumonia and bacteremia (sensitivity 0.77; specificity 0.96; positive predictive value 0.87; negative predictive value 0.91; relative risk 9.6). In six cases of nosocomial infection, the pathogen isolated from dental plaque was the first identified source of nosocomial infection. Conclusions: The amount of dental plaque increased during the ICU stay. Colonization of dental plaque was either present on admission or acquired in 40% of patients. A positive dental plaque culture was significantly associated with subsequent nosocomial infections. Dental plaque colonization by aerobic pathogens might be a specific source of nosocomial infection in ICU patients. (Crit Care Med 1998; 26:301-308) Nosocomial infections continue to be a major cause of morbidity and mortality in patients hospitalized in the intensive care unit (ICU). Their frequency rate reaches approximately20% of all admitted patients and may exceed 60% 1. Most of these infections are of endogenous origin, following a sequence of previous colonization at the oropharyngeal and intestinal levels 2. Subsequent infection occurs either by occult inhalation in the tracheobronchial tree or after bacterial translocation in the bloodstream 3. For these reasons, colonization of oropharynx and gastric content has been extensively studied in ICU patients, resulting in specifically designed preventive measures, i.e., reduction in the use of prophylactic antacids or selective digestive decontamination by topical antibiotics 4. The possibility that the dental bacterial plaque might be involved during the sequence of initial colonization and may represent a specific source of nosocomial infections has been poorly examined. The bacterial dental plaque is a dynamic and complex system that associates microorganisms and an extracellular matrix. It predominates on the sub- and supragingival surfaces of the teeth, but may also develop on mucosal surfaces and dental prosthesis. More than 300 different bacterial species are harbored in its complex aerobic and anaerobic flora and 1 mm3 of plaque contains >10 sup 8 bacteria 5. Aerobic bacteria predominate at the supragingival level and anaerobic bacteria at the subgingival level, but aerobic pathogens are not usually present in the plaque. Numerous factors are involved in making the plaque flora resistant to colonization by aerobic pathogens: the physico-chemical properties of the mucosal surface, the salivary enzymatic content, and the presence of specific proteases and immunoglobulins 6. However, poor oral hygiene and lack of mechanical elimination are the main factors leading to proliferation and accumulation of dental plaque and subsequent colonization. Colonization of dental plaque by aerobic pathogens has been documented in granulocytopenic patients and in patients with cystic fibrosis 7,8. ICU patients may also be at risk of dental plaque colonization, due to difficulties in oral hygiene, changes in salivary properties, and reduction of anaerobic flora by antibiotherapy. To our knowledge, only one study 9 has been specifically designed to measure the frequency rate of dental plaque colonization in ICU patients. In that study 9, 34 ICU patients were included and compared with 25 non-ICU patients treated in a dental medical school. The main results of that study9 showed that compared with four (16%) of the 25 control patients, 21 (62%) of the 34 ICU patients were found to be colonized by aerobic pathogens on admission. The amount of plaque was significantly higher in ICU patients but did not correlate with bacterial colonization. The changes in dental status and plaque colonization during the ICU stay and their link with the occurrence of nosocomial infections were not documented. We designed the present prospective study to document in ICU patients: a) the dental status and the evolution of dental plaque; b) the prevalence of plaque colonization on admission and during the ICU stay; and c) the relationships between plaque colonization by aerobic pathogens and the occurrence of nosocomial infections. The main results of our study show that dental plaque might be an important reservoir of aerobic pathogens and a specific source of nosocomial pneumonia and bacteremia in ICU patients.