Authors evaluated the quantitative culture of bronchoalveolar lavage fluid(BALF) in patients who were being treated with antimicrobial agents and the characteristics of isolated microorganism.

A prospective study was done with 25 patients under mechanical ventilation and antimicrobial treatment in ICU and NCU of Yongdong Severance Hospital from Apr. to Sep. 1999.

Patients were classified into two groups: control group (n=5) and patients with VAP (n=20). The threshold of quantitative culture of BAL fluid in the diagnosis of VAP was 104 cfu/ml.

1) In gram staining of BALF, one patient in the control group and four in the VAP group showed positive results. Quantitative culture of BALF showed no organisms in the patients in the control group and in 9 VAP patients. Therefore the overall sensitivity was 43.8%. 2) Frequency of isolated organisms cultured above diagnostic threshold was in the following other : E. cloacae, S. aureus, K. pneumoniae, and A. baumani. S. aureus and Staphylococcus coagulase(-) were all resistant to oxacillin. Seven out of 10 isolated G (-) organisms were suspected to be organisms producing extended spectrum β-lactamase (ESBL). 3) The concurrence between gram staining of sputum aspiration and that of BALF was only in 1 case. And the concurrence of culture results was observed in 3 cases.

The sensitivity of gram staining and quantitative culture of BALF from patients under antibiotic therapy and the concordance rate between conventional tracheal aspiration and BAL were low, facts which were important in interpretation the data. Since the frequency of drug resistance organisms was not different from that of foreign data, antibiotics must be prudently selected and used.