Search

A total of 1120 specimens of fresh urine from male patients was tested for Chlamydia trachomatis with the Roche Amplicor PCR Kit and an in-house PCR assay. The in-house PCR had an internal control to monitor inhibitory effects of clinical specimens on the PCR assay. All urine samples were processed within 24-48 h of collection and DNA was extracted on the same day that the assays were performed. Specimens that gave discrepant PCR results were tested by a reference laboratory with both the Roche Amplicor kit and their in-house PCR assay. Of the 1120 samples, 174 gave positive results in both assays and 942 gave negative results in both assays. Only one specimen showed an inhibitory effect on the in-house PCR assays, as indicated by failure to produce the internal control PCR product. This specimen gave negative results by both assays. There were four discrepant results in the two PCR assays. One was a false negative result obtained with the Roche Amplicor kit and the remaining three discrepant results could not be resolved because there was an insufficient quantity of specimen. This study demonstrated that the Roche Amplicor kit could effectively detect C. trachomatis in urine specimens from this population of male patients with negligible inhibition of PCR.

The new Sanofi Diagnostics Pasteur Chlamydia Microplate EIA shortened assay was evaluated by comparison with the original standard assay and cell culture. A total of 853 paired male and female genital tract specimens was tested with both Sanofi Chlamydia Microplate EIA shortened and standard assays and the results were compared with those of cell culture. For confirmation, a blocking assay run in the shortened format was used. Discrepancies between the three methods were resolved by a direct fluorescent antibody (DFA) test on the EIA samples or the culture retentate, or both. After resolution of discrepant results, the standard assay had a sensitivity, specificity, positive predictive value and negative predictive value of 98.5%, 100%, 100% and 99.9%, respectively. The shortened assay results were 100%, 100%, 100% and 100%, respectively. The shortened assay takes approximately 1.5 h less time than the standard assay and this study demonstrated that they have equivalent sensitivity and specificity. The improvement in turnaround time enables results to be reported on the same day.

The Genie HIV-1/2 kit (Sanofi Diagnostics Pasteur, Montreal, Quebec), a synthetic-peptide solid-phase enzyme immunoassay, was evaluated as a confirmatory assay for HIV-1 antibodies in comparison with Western blot (BioRad, Hercules, CA, USA) on 50 stored HIV-1 antibody-positive sera and the 137 sera yielding repeated positive results in the conventional EIA screen out of 13405 fresh patient sera from Saskatchewan in 1993. The stored HIV-1-positive sera were uniformly positive in the Genie test. Of the 137 EIA screen-positive sera, 33 were uniformly positive and 64 were uniformly negative in Genie and Western blot; 36 were Genie-negative and indeterminate by Western blot; and four were Genie indeterminate, of which one was negative and three were indeterminate by Western blot. All HIV-1 Western blot-indeterminate and Genie-interdeterminate sera were negative in radio-immunoprecipitation assay (RIPA) and Western blot for HIV-1 and HIV-2 antibodies performed by a reference laboratory. Genie gave an accurate definitive result for 97% of EIA positive sera compared with 71% for Western blot. There was excellent correlation between Genie, Western blot and RIPA results. However, the Genie assay was faster, less costly and yielded fewer indeterminate results than Western blot in confirmatory testing for HIV-1 antibodies.

Legionella pneumophila, in Buffered Yeast Extract broth, was treated for 5 h at 37 degrees C with rosaramicin, erythromycin, cefotaxime, dibekacin, penicillin, methicillin, cefoxitin, cephalothin, ticarcillin, carbenicillin or polymyxin B at near-MIC levels and above. Electronmicroscopy demonstrated morphological changes to the bacteria in some, but not all, of the antibiotic-treated suspensions. Penicillin, at 1000 micrograms/ml (40 X MIC) but not less, produced smooth bubble-like structures on cell surfaces; methicillin produced rough bubble-like structures at 100 micrograms/ml (MIC) but not at 1000 micrograms/ml. In each case, these structures resembled spheroplasts. Polymyxin B induced small-bleb formation on the bacterial cell surfaces at all concentrations tested (MIC-10 X MIC). The other eight antibiotics did not induce any morphological changes at any concentration tested.