The role of bacterial interference in the increased prevalence of oropharyngeal gram-negative bacilli among alcoholics and diabetics.

The oral flora of alcoholics, diabetics, and normal control subjects were compared using an agar overlay technique to determine whether the increased prevalence of oropharyngeal gram-negative bacilli among alcoholics and diabetics exists because patients with these diseases have decreased numbers of normal inhibitory bacteria in the oropharynx. Alcoholics generally had slightly lower concentrations of inhibitory bacteria than control subjects, and diabetics had somewhat higher concentrations than control subjects. However, colonized subjects did not differ from noncolonized subjects with respect to concentrations of these inhibitory bacteria in the oropharynx. Characterization of inhibitory bacteria demonstrated a preponderance of nongroupable alpha-hemolytic streptococci in each of the study groups. Stimulated saliva obtained from subjects failed to demonstrate significant differences in pH between study populations or between colonized and noncolonized subjects within each study population. These results suggest that the frequent oropharyngeal colonization of alcoholics and diabetics by gram-negative bacilli involves mechanisms other than that of a deficiency of normal interfering aerobic bacteria in the oropharynx or an altered salivary pH leading to inactivation in vivo of bacteriocins produced by these inhibitory bacteria.