Influence of storage time on DNA of Chlamydia trachomatis, Ureaplasma urealyticum, and Neisseria gonorrhoeae for accurate detection by quantitative real-time polymerase chain reaction

The shipment and storage conditions of clinical samples pose a major challenge to the detection accuracy of Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and Ureaplasma urealyticum (UU) when using quantitative real-time polymerase chain reaction (qRT-PCR). The aim of the present study was to explore the influence of storage time at 4°C on the DNA of these pathogens and its effect on their detection by qRT-PCR. CT, NG, and UU positive genital swabs from 70 patients were collected, and DNA of all samples were extracted and divided into eight aliquots. One aliquot was immediately analyzed with qRT-PCR to assess the initial pathogen load, whereas the remaining samples were stored at 4°C and analyzed after 1, 2, 3, 7, 14, 21, and 28 days. No significant differences in CT, NG, and UU DNA loads were observed between baseline (day 0) and the subsequent time points (days 1, 2, 3, 7, 14, 21, and 28) in any of the 70 samples. Although a slight increase in DNA levels was observed at day 28 compared to day 0, paired sample t-test results revealed no significant differences between the mean DNA levels at different time points following storage at 4°C (all P>0.05). Overall, the CT, UU, and NG DNA loads from all genital swab samples were stable at 4°C over a 28-day period.

The role of a commercial enzyme immuno assay antigen detection system for diagnosis of C. trachomatis in genital swab samples.

In the present pilot study, endocervical and urethral swabs collected from 100 patients attending sexually transmitted disease (STD) clinics and regional centre for STD in two referral hospitals in New Delhi were analyzed by enzyme immune assay (EIA), polymerase chain reaction (PCR) and direct fluorescent antibody (DFA) for detection of C. trachomatis. It was found that EIA could detect a very low number of cases (3/100) as against DFA (11/100) and PCR (9/100). Thus, in spite of the widespread availability, lower cost and ease of performance of the enzyme-linked-immunosorbent serologic assay, the present study highlights the need to employ sophisticated diagnostic tools like DFA and PCR for detection of Chlamydia trachomatis in STD patients.