Oropharyngeal cultures of patients in protected environment units: evaluation of semiquantitative technique during antibiotic prophylaxis.

A semiquantitative culture technique was used to monitor the microbial flora of the oropharynx of 30 patients receiving antibiotic prophylaxis in protected environment units. After institution of antibiotic prophylaxis, the median concentration of organisms in the oropharynx fell by 2 logs but gradually increased by 1 log and then remained stable. Neisseria spp., Micrococcus sp., and Streptococci were generally eradicated by the antibiotics but were replaced by Lactobacilli and yeast. Four of nine enteric organisms persisted despite in vitro sensitivity to the antibiotic regimens. Yeast were cultured from the initial specimens of only 17% of the 30 patients, but they were cultured subsequently from specimens of 80% of the 20 patients who remained in protected environment units for at least 8 weeks.