20:T465,Evidence presented in support of the hypothesis that interrelationships among organisms in the pharynx provide one of the mechanisms that maintain the bacterial status quo. Many organisms in the normal pharynx are capable in vitro of preventing the growth of other bacterial species—species with which they coexist in vivo or test organisms to which they are exposed experimentally. The majority of these "inhibitors" as revealed by the aerobic techniques described are alpha hemolytic streptococci. Detailed study of cultures from the posterior pharynx of patients undergoing massive antibiotic therapy for open heart surgery shows that as virtually all inhibitors (alpha hemolytic streptococci) in the patient's normal flora are suppressed by antibiotic therapy, overgrowth of bacteria not usually found in the pharynx routinely occurs. When therapy is withdrawn inhibitors reappear, and normal flora is reestablished. When inhibitors are resistant to the antibiotics used, no such overgrowth occurs. The data presented indicate that presence of the inhibitors plays a key role in maintaining the balance of normal flora.21:T451,We compared the prevalence of Gram-negative bacilli in the pharyngeal flora of two groups of patients with a known predilection for Gram-negative bacillary pneumonia (chronic alcoholics and diabetics), two other groups of aspiration-prone persons with no known predilection for Gram-negative bacillary pneumonia (epileptics and narcotic addicts), and normal control subjects. Quantitative cultures of saline gargles showed pharyngeal Gram-negative bacilli to be significantly (P<.05) more prevalent among alcoholics (35%) and diabetics (36%) but not epileptics (17%) or addicts (20%) than controls (18%). Counts of 100 Gram-negative bacilli per milliliter were also significantly more common in alcoholics (14%) and diabetics (24%) than controls (5%,P<.05).Enterobactersp,Klebsiella pneumoniae, andEscherichia coliwere the most common Gram-negative bacilli isolated. Increased colonization by Gram-negative bacilli might be a factor contributing to the propensity of alcoholics and diabetics for Gram-negative pneumonia. (Arch Intern Med138:1224-1227, 1978)

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