Sensitivity and specificity of three new commercially available Chlamydia trachomatis tests

In order to determine the value of new Chlamydia trachomatis (Ct) specific tests for routine serological diagnosis of Ct infections, we evaluated several commercially available assays (C. trachomatis enzyme immunoassay (EIA), Labsystems (CtL); SeroCT, Savyon (CtS); pELISA, Medac (CtMp)) in various study populations. The prevalence of C. trachomatis-specific IgA antibodies in a blood donor population (n = 443) as determined by the peptide based tests CtL, the CtS and the CtMp was 5%, while for IgG antibodies this was 6% (CtL and CtS) and 12% (CtMp) respectively. Prevalence was negatively correlated with age, concording with C. trachomatis specificity. None of the three tests showed significant titre rises in serum samples taken from patients with a proven infection of Chlamydia pneumoniae (n = 22), indicating species-specificity for all three tests. In patients with a polymerase chain reaction proven (n = 324) Ct infection, 75%, 70% and 68% were positive for IgG and 45%, 38% and 47%, positive for IgA as determined by the CtMp, CtL and CtS respectively. We conclude that the new synthetic peptide-based EIA tests are able to detect species-specific Ct antibodies, which are strongly correlated to (active) infection.

Detection of PCR inhibitors in cervical specimens by using the AMPLICOR Chlamydia trachomatis assay

To determine that susceptibility of AMPLICOR Chlamydia trachomatis PCR to inhibitory factors possibly present in cervical specimens, we obtained cervical specimens from 200 gynecology patients attending our outpatient clinic. The prevalence of C. trachomatis infection was 4.1%, as determined by cell culture. All AMPLICOR specimens were tested in one procedure as described by the manufacturer, and after the specimen was spiked with C. trachomatis, several other pretreatment protocols were used. Complete inhibition of the PCR was observed in 38 (19%) cervical specimens. Heat treatment at 95 degrees C, freeze-thawing, or 10-fold dilution of the samples reduced the initial inhibition to 9, 16, or 9%, respectively. A combination of heat treatment and 10-fold dilution reduced the inhibition to 4% of the samples. A second specimen type (swabs inoculated in 0.2 M sucrose phosphate buffer [2SP]) was also evaluated. A 10-fold dilution of the spiked 2SP specimen resulted in an inhibition rate of 6%, which was comparable to that obtained by centrifugation of the 2SP specimen prior to processing. Furthermore, it was shown that the inhibition was not correlated with blood contamination. Processing the specimens on the day of collection or the day after resulted in a higher inhibition rate than did delayed processing (27.6 versus 15.5%, respectively). An inverse correlation was found between the concentration of C. trachomatis added to the sample and the rate of inhibition observed. The inhibition was partly correlated with the pH of the cervical mucosa. Decreased inhibition was found at pH values of > or = 7.5. The effects of blood, pH, and delay in processing were all evaluated by using the AMPLICOR specimen. We conclude that the susceptibility of AMPLICOR C. trachomatis PCR to inhibiting factors in cervical specimens can be significantly reduced if the pretreatment procedure includes heat treatment or the use of 2SP transport medium. Also, a 10-fold dilution of the clinical specimen followed by heat treatment will largely prevent the inhibition of this PCR.

Prevalence of Chlamydia trachomatis in women attending a family planning clinic in Papua New Guinea

OBJECTIVE

To determine the prevalence of Chlamydia trachomatis infection in women attending a family planning clinic in Papua New Guinea, in the period between April and June 1991.

SETTING

The outpatient department of Obstetrics and Gynaecology of Port Moresby General Hospital, Port Moresby, Papua New Guinea, the departments of Dermato-Venereology and Clinical Microbiology of the Erasmus University, Rotterdam, The Netherlands and the National Institute of Public Health and Environmental Protection, Bilthoven, The Netherlands.

PATIENTS

A total of 254 consecutive women who attended the family planning clinic at Port Moresby General Hospital, Papua New Guinea were enrolled into this study.

METHODS

Cervical infections with C trachomatis were diagnosed using the direct immunofluorescent assay (DFA) and the polymerase chain reaction (PCR). Serum IgM and IgG antibodies directed against C trachomatis were detected using the enzyme-linked fluorescent assay (ELFA).

RESULTS

The prevalence of C trachomatis was 14.6% using the PCR, 9.1% using the DFA and 17.3% when the results of the PCR and the DFA were combined. An elevated IgM titre was observed in 14.2% of the women, whereas 44.1% had an elevated IgG titre. The titres of IgM or IgG were significantly higher in women who were positive using the PCR or the DFA than in those who were negative in both the PCR and the DFA (p = 0.032 and p = 0.0046, respectively).

CONCLUSION

Cervical infection by C trachomatis can be considered a major health problem in at least the studied population in Papua New Guinea. The prevalence of C trachomatis infection is at least comparable with that in groups with a high prevalence in industrialized countries. Effective screening and treatment programmes are imperative to combat this problem.

In-vitro activity of a new quinolone (CP-99,219) compared with ciprofloxacin, pefloxacin, azithromycin and penicillin against Neisseria gonorrhoeae

The in-vitro activities of CP-99, 219, ciprofloxacin, pefloxacin, azithromycin and penicillin was tested against 114 Neisseria gonorrhoeae strains. The MIC90s were: 0.008 mg/L (MIC range 0.001-0.06 mg/L) for CP-99, 219, 0.008 mg/L (MIC range 0.001-0.25 mg/L) for ciprofloxacin, 0.12 mg/L (MIC range 0.008-4 mg/L) for pefloxacin, 0.25 mg/L (MIC range 0.03-1 mg/L) for azithromycin and 16 mg/L (MIC range 0.015-16 mg/L) for penicillin. The activity of CP-99,219 against various N. gonorrhoeae isolates was comparable to ciprofloxacin.

Improved performance of PACE 2 with modified collection system in combination with probe competition assay for detection of Chlamydia trachomatis in urethral specimens from males

The Gen-Probe PACE 2 assay (GP) in combination with a modified collection system was compared with cell culture (CC) for the detection of Chlamydia trachomatis in urethral specimens from males. Analysis of discordant results was performed by PCR. The modifications, i.e., application of a more rigid swab type and a 50% reduction in the amount of transport medium, were made to improve the sensitivity of the assay. By using the modified GP on 302 urethral specimens from males, a sensitivity of 89.5% and a specificity of 100% were determined. In addition, performance of a probe competition assay on all GP samples with a result > 0.6 and < 1.0 times the cutoff factor (gray zone) detected three more true-positive samples. The sensitivity of GP in combination with the probe competition assay increased to 94.9%, with a specificity of 100%. This was identical to the performance of CC. The modified GP offers a very sensitive and specific alternative to CC.

Evaluation of Clearview and Magic Lite tests, polymerase chain reaction, and cell culture for detection of Chlamydia trachomatis in urogenital specimens

The Clearview Chlamydia test (CV; Unipath Ltd., Bedford, United Kingdom), the Magic Lite Chlamydia test (ML; CIBA Corning, Medfield, Mass.), a polymerase chain reaction (PCR), and cell culture (CC) were evaluated for detection of Chlamydia trachomatis in urogenital specimens. Specimens were collected from 283 men and 724 women visiting the outpatient clinic for Sexually Transmitted Diseases at the University Hospital Rotterdam, Rotterdam, The Netherlands. ML, PCR, and CC were all performed on the same sample to prevent swab-to-swab variability. CV was performed on a separate sample. Analysis of discordant results was performed by application of the following confirmatory assays: first, PCR on the CC, second, ML was repeated, and third, PCR was repeated by using a different DNA extraction protocol. If more than one test was positive, the sample was considered true positive. If only one test was positive, which was confirmed by the confirmatory assay, the sample was also considered true positive. By using these interpretations, the following results were obtained. The sensitivity and specificity of CV for samples from men were 60.4 and 86.3%, respectively. For samples from women, these values were 62.3 and 99.7%, respectively. The low specificity for samples from men was caused by unidentified substances in the swab that was used. The use of CV on samples from men is not recommended by the manufacturer. For samples from women, the specificity of CV was high, but the low sensitivity of CV limits its use for diagnostic purposes. The sensitivities of ML were low for samples from both men and women (68.8% and 50.9% respectively), while specificities were excellent for samples from both groups (100 and 99.9%, respectively). The low sensitivity of ML limits its diagnostic value. The PCR technique was highly specific for samples from both men (99.6%) and women (99.9%). The sensitivity of PCR, however, was unexpectedly low for samples from both groups (men, 87.5%; women, 79.2%), most likely because of the sample treatment method used. The sensitivity and specificity values of CC for samples from men were 95.8 and 100%, respectively. For samples from women, these values were 100 and 99.9%, respectively. In the present study, CC was the most reliable technique for the detection of C. trachomatis.

Comparison of HeLa 229 and McCoy cell cultures for detection of Chlamydia trachomatis in clinical specimens

Consecutive clinical specimens of Chlamydia trachomatis (1,048) were inoculated in parallel on DEAE-dextran- and cycloheximide-treated HeLa 229 cells and cycloheximide-treated McCoy cells. HeLa 229 cell culture detected 113 positive specimens, and McCoy cell culture detected 103 positive specimens. This difference is not significant. However, HeLa 229 cell culture yielded significantly more inclusions than McCoy cell culture in the 95 specimens positive in both cell types (P = 0.042). For routine diagnostic purposes, a choice for one of the cell types may be determined by local preferences.

Trends in gonococcal resistance to antibiotics in Rotterdam, The Netherlands, 1975-86

The incidence of resistance of Neisseria gonorrhoeae to penicillin and tetracycline was periodically monitored during 1975-86. The incidence of resistance to penicillin (minimum inhibitory concentration (MIC) of more than 1.28 mg/l) of non-PPNG strains remained low (less than 2.5%). The incidence of penicillinase producing N gonorrhoeae (PPNG) strains decreased after a peak of 14% in 1982 to a mean of 8% in more recent years. After a gradual increase, the incidence of tetracycline resistant (MIC of more than 1.28 mg/l) strains has remained stable at around 20% during the past five years. This indicates that a continuing increase in incidence of resistance was not observed in this outpatient clinic.