A prospective study of tracheobronchial bacterial flora in acutely brain-injured patients with and without antibiotic prophylaxis.

The authors observed prospectively 28 brain-injured patients, who required respiratory tract intubation, to determine the effect of antibiotic prophylaxis on bacterial flora, the rate of flora change, and the appearance of infection. Antibiotics not only failed to alter the rate of abnormal colonization but were associated with an earlier appearance of Gram-negative bacilli, the organisms that produced the most severe infections. Although more infections occurred in patients initially untreated with antibiotics, these infections were usually mild and caused by organisms susceptible to highly effective and relatively safe drugs. Although highly reproducible as a laboratory determination, the nitroblue tetrazolium dye test score showed no consistent relationship with the presence or absence of bacterial infection. Regular and extensive clinical and laboratory observations, including cultures of the respiratory tract helped to make the antibiotic administration in these patients specific, appropriate, and reasonable. Broad spectrum antibiotic prophylaxis does not prevent and may enhance the development of severe pulmonary infection in these patients.