Inhibition of PCR in Genital and Urine Specimens Submitted for Chlamydia trachomatis Testing

Abstract

We determined the frequency of PCR inhibition in genital and urine specimens submitted for Chlamydia trachomatis testing using the internal control DNA provided with the COBAS AMPLICOR C. trachomatis test and assessed methods to remove it. Inhibition occurred in 65 of 906 (7%) cervical swabs, 23 of 51 (45%) urethral swabs, and 2 of 175 (1.1%) urine samples. Overall, inhibition was eliminated in processed specimens after storage at 4°C in 77 of 90 specimens (86%), freezing at −70°C in 59 of 82 specimens (72%), storage at 4°C followed by either 1:100 dilution in 37 of 43 specimens (86%) or 1:10 dilution in 42 of 47 specimens (89%), and phenol-chloroform extraction in 79 of 80 specimens (99%). No positive specimens were missed due to inhibition. We conclude that PCR inhibition is rare with urine specimens and infrequent with endocervical swabs but occurs frequently with urethral swabs. The frequency of PCR inhibition may be significantly reduced by methods which can be easily incorporated into the processing of specimens.

Detection of Chlamydia trachomatis DNA using MagNA Pure DNA extraction and Cobas Amplicor CT/NG amplification

“…Semen and FVU were inhibited more frequently (10.0% and 11.5%, respectively). Variable inhibition rates (2.7% to 15%) have been reported previously for urine samples [4][5][6][7][8][9], especially female urine [5,10,11]. In the present study, among 52 FVU (38 male) samples, five of the six inhibited samples were from females, giving an inhibition rate of 37.5% for female samples, but only 2.6% for male samples.…”

“…These resistance profiles suggest that AmpC derepression or hyper-production is conferring resistance to the third-generation cephalosporins [3]. However, production of extended-spectrum b-lactamases (ESBLs) by E. cloacae isolates in Taiwan [4,5] and worldwide [6][7][8] has been reported, raising the possibility of therapeutic failure with isolates apparently susceptible to cefepime [9]. Recently, SHV-12 carriage has been identified among E. cloacae isolates from two large (>1200 beds) hospitals in northern Taiwan [4,5].…”

Programmed Transfer of Sequence Information into a Molecularly Imprinted Polymer for Hexakis(2,2′-bithien-5-yl) DNA Analogue Formation toward Single-Nucleotide-Polymorphism Detection

“…This alignment does not limit the probe length, as is the case with the conventional vertically tethered probe. 68 Moreover, our 2,2'-bithien-5-yl MIPs are invulnerable to inhibition by sample components 69,70 that can result in false negative determinations in clinical, 71,72 environmental, 73 food, 74 and forensic 75 samples. Therefore, our direct method of quantification of specific sequences is a promising alternative to quantitative amplification methods, such as PCR reliant on polymerases.…”

First evaluation of six nucleic acid amplification tests widely used in the diagnosis of Chlamydia trachomatis in Russia

“…These findings are, in general, consistent with previous reports. [32][33][34][35] Nevertheless, using the reference methods, none of the samples was inhibited. This is probably due to the fact that MagNA Pure LC was used for automated DNA isolation, which has previously been shown to increase the sensitivity and significantly lower the rate of inhibition.…”