COMPARISON OF SAMPLE PREPARATION METHODS FOR DETECTION OF CHLAMYDIA-PNEUMONIAE IN BRONCHOALVEOLAR LAVAGE FLUID BP PCR

Amplification inhibitors can lead to false-negative results for PCR. I n order to evaluate the reliability of PCR for the detection of Chlamy dia pneumoniae, the presence of PCR inhibitors in 75 bronchoalveolar l avage specimens was assessed after treatment by various sample prepara tion methods. Specimens were collected from patients with acute respir atory infections, including four cases of proven C. pneumoniae infecti on. Substances inhibitory to the amplification of chlamydial DNA conti nued to be present in 12% of the samples treated according to the comm only used single-step proteinase K digestion and in 31% of the samples processed by heat treatment. However, the complexing of DNA-contamina ting proteins and polysaccharides from digested specimens to cetyltrim ethylammonium bromide (CTAB) followed by DNA extraction efficiently re moved inhibitors from all experimental samples and provided subsequent identification of all positive clinical samples by PCR. The CTAB meth od and proteinase K treatment had comparable detection limits of appro ximately 0.01 inclusion-forming units. CTAB-based DNA purification of respiratory specimens is recommended to increase the diagnostic sensit ivity of PCR and confidence in negative results.