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Fifteen bone marrow transplant (BMT) patients who received three 0.12% chlorhexidine digluconate (CHX) mouthrinses daily for eight weeks were monitored weekly for the occurrence of oral opportunistic Gram-negative bacilli (GNB). Tongue and buccal mucosa were sampled with use of Culturette swabs that were streaked on plates containing selective MacConkey agar. After incubation, colony-forming units were scored and putative GNB classified with use of the API 20E rapid identification system and supplemental biochemical tests. After identification, the susceptibilities of all GNB to CHX were determined by means of a disk diffusion sensitivity assay. Sixty-seven percent (10) of the BMT subjects had at least one GNB-positive tongue culture, and 53% (8) had GNB in samples taken from the buccal mucosa. Of 218 samples taken, 26% and 24% from the tongue and buccal mucosa, respectively, were GNB-positive. The predominant clinical GNB isolates were Enterobacter cloacae (46%) and Klebsiella pneumoniac (30%). Their respective CHX minimum inhibitory concentrations (MICs) were similar to those of ATCC reference strains. Although the CHX MIC values of the clinical GNB isolates were high (less than or equal to 37.5 to less than or equal to 300 micrograms/mL), they were not dependent upon length of exposure to the agent. Therefore, changes in sensitivity or resistance to CHX did not appear to occur. The results suggest that the mouths of BMT patients--and perhaps of other immunosuppressed individuals--should be routinely monitored for GNB, as are other clinically important sites, such as the throat and the urinary and gastro-intestinal tracts.

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