Urine specimens from pregnant and nonpregnant women inhibitory to amplification of Chlamydia trachomatis nucleic acid by PCR, ligase chain reaction, and transcription-mediated amplification: identification of urinary substances associated with inhibition and removal of inhibitory activity

Optimizing extraction of microbial DNA from urine: Advancing urinary microbiome research in bladder cancer

PURPOSE

This study aimed to evaluate and optimize microbial DNA extraction methods from urine, a non-invasive sample source, to enhance DNA quality, purity, and reliability for urinary microbiome research and biomarker discovery in bladder cancer.

MATERIALS AND METHODS

A total of 302 individuals (258 with genitourinary cancers and 44 with benign urologic diseases) participated in this study. Urine samples were collected via sterile catheterization, resulting in 445 vials for microbial analysis. DNA extraction was performed using three protocols: the standard protocol (SP), water dilution protocol (WDP), and chelation-assisted protocol (CAP). DNA quality (concentration, purity, and contamination levels) was assessed using NanoDrop spectrophotometry. Microbial analysis was conducted on 138 samples (108 cancerous and 30 benign) using 16S rRNA sequencing. Prior to sequencing on the Illumina MiSeq platform, Victor 3 fluorometry was used for validation.

RESULTS

WDP outperformed other methods, achieving significantly higher 260/280 and 260/230 ratios, indicating superior DNA purity and reduced contamination, while maintaining reliable DNA yields. CAP was excluded due to poor performance across all metrics. Microbial abundance was significantly higher in WDP-extracted samples (p<0.0001), whereas SP demonstrated higher alpha diversity indices (p<0.01), likely due to improved detection of low-abundance taxa. Beta diversity analysis showed no significant compositional differences between SP and WDP (p=1.0), supporting the reliability of WDP for microbiome research.

CONCLUSIONS

WDP is a highly effective and reliable method for microbial DNA extraction from urine, ensuring high-quality and reproducible results. Future research should address sample variability and crystal precipitation to further refine microbiome-based diagnostics and therapeutics.

Evaluation of the APTIMA Combo 2™ kit for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae in frozen semen

Detection of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) in cryopreserved semen is crucial for screening sperm donors. The evaluation of the limit of detection (LOD) of the APTIMA Combo 2™ kit (Panther, Hologic) was performed on cryopreserved semen samples spiked with CT and NG at concentrations ranging from 1 to 106 IFU/mL or CFU/mL, respectively. The LOD was 102 IFU/mL for CT and 10 CFU/mL for NG in single infection or coinfection. An inhibitory effect of semen on amplification was highlighted. This study confirmed the performance of the APTIMA Combo 2™ kit for screening cryopreserved sperm samples before donation.

Culture and amplification-free nanopore sequencing for rapid detection of pathogens and antimicrobial resistance genes from urine

PURPOSE

Urinary Tract Infections (UTIs) are among the most prevalent infections globally. Every year, approximately 150 million people are diagnosed with UTIs worldwide. The current state-of-the-art diagnostic methods are culture-based and have a turnaround time of 2-4 days for pathogen identification and susceptibility testing.

METHODS

This study first establishes an optical density culture-based method for spiking healthy urine samples with the six most prevalent uropathogens. Urine samples were spiked at clinically significant concentrations of 103-105 CFU/ml. Three DNA extraction kits (BioStic, PowerFood, and Blood and Tissue) were investigated based on the DNA yield, average processing time, elution volume, and the average cost incurred per extraction. After DNA extraction, the samples were sequenced using MinION and Flongle flow cells.

RESULTS

The Blood and Tissue kit outperformed the other kits based on the investigated parameters. Using nanopore sequencing, all the pathogens and corresponding genes were only identified at a spike concentration of 105 CFU/ml, achieved after 10 min and 3 hours of sequencing, respectively. However, some pathogens and antibiotic-resistance genes (ARG) could be identified from spikes at 103 colony formation units (CFU/mL). The overall turnaround time was five hours, from sample preparation to sequencing-based identification of pathogen ID and antimicrobial resistance genes.

CONCLUSION

This study demonstrates excellent promise in reducing the time required for informed antibiotic administration from 48 to 72 h to five hours, thereby reducing the number of empirical doses and increasing the chance of saving lives.

Microbial DNA extraction method for avian feces and preen oil from diverse species

As DNA sequencing technology continues to rapidly improve, studies investigating the microbial communities of host organisms (i.e., microbiota) are becoming not only more popular but also more financially accessible. Across many taxa, microbiomes can have important impacts on organismal health and fitness. To evaluate the microbial community composition of a particular microbiome, microbial DNA must be successfully extracted. Fecal samples are often easy to collect and are a good source of gut microbial DNA. Additionally, interest in the avian preen gland microbiome is rapidly growing, due to the importance of preen oil for many aspects of avian life. Microbial DNA extractions from avian fecal and preen oil samples present multiple challenges, however. Here, we describe a modified PrepMan Ultra Sample Preparation Reagent microbial DNA extraction method that is less expensive than other commonly used methodologies and is highly effective for both fecal and preen oil samples collected from a broad range of avian species. We expect our method will facilitate microbial DNA extractions from multiple avian microbiome reservoirs, which have previously proved difficult and expensive. Our method therefore increases the feasibility of future studies of avian host microbiomes.

Urine: A Pitfall for Molecular Detection of Toscana Virus? An Analytical Proof-of-Concept Study

Toscana virus (TOSV), a sandfly-borne virus, is an important etiological agent in human acute meningitis and meningoencephalitis in the Mediterranean area during the summer. However, the actual number of TOSV infections is underestimated. Laboratory confirmation is necessary because TOSV infection has overlapping clinical features with other neuro-invasive viral infections. Nowadays, the reference test for direct diagnosis in the acute phase of TOSV infection is the PCR based method for detecting TOSV in cerebrospinal fluid and/or plasma, serum, or blood. Although poorly employed, urine is another helpful biological matrix for TOSV detection. Urine is a matrix rich in PCR inhibitors that affect PCR efficiency; consequently, false negatives could be generated. To investigate the potential effect of urine PCR inhibitors on TOSV detection, we compared undiluted and diluted urine using 10-fold series of spiked TOSV. The results showed a significant improvement in TOSV detection performance in diluted urine (1 TCID50 vs. 1 × 104 TCID50 limit of detection and 101.35% vs. 129.62% efficiency, respectively, in diluted and undiluted urine). In conclusion, our data provide preliminary important insights into the use of diluted urine to limit the impact of the inhibitory effects of urine on the detection of TOSV in RT-PCR-based approaches.

PCR inhibitors and facilitators - Their role in forensic DNA analysis

Since its inception, DNA typing technology has been practiced as a robust tool in criminal investigations. Experts usually utilize STR profiles to identify and individualize the suspect. However, mtDNA and Y STR analyses are also considered in some sample-limiting conditions. Based on DNA profiles thus generated, forensic scientists often opine the results as Inclusion, exclusion, and inconclusive. Inclusion and exclusion were defined as concordant results; the inconclusive opinions create problems in conferring justice in a trial- since nothing concrete can be interpreted from the profile generated. The presence of inhibitor molecules in the sample is the primary factor behind these indefinite results. Recently, researchers have been emphasizing studying the sources of PCR inhibitors and their mechanism of inhibition. Furthermore, several mitigation strategies- to facilitate the DNA amplification reaction -have now found their place in the routine DNA typing assays with compromised biological samples. The present review paper attempts to provide a comprehensive review of PCR inhibitors, their source, mechanism of inhibition, and ways to mitigate their effect using PCR facilitators.

Comprehensive Molecular Screening in a Cohort of Young Men Who Have Sex With Men and Transgender Women: Effect of Additive Rectal Specimen Source Collection and Analyte Testing

BACKGROUND

This study's purposes were to characterize detection rates of several sexually transmitted infection (STI) agents and describe the effect additional specimen source and analyte screening has on STI detection within a cohort of young men who have sex with men and transgender women.

METHODS

Within a 16-month interval, 1966 encounters involved dual urine and rectal swab submissions assessed by commercial transcription-mediated amplification-based assays for Chlamydia trachomatis and Neisseria gonorrhoeae and by off-label transcription-mediated amplification-based Trichomonas vaginalis and Mycoplasma genitalium testing. Identification of STI carriers used algorithms involving Food and Drug Administration-cleared screening methods, laboratory-modified testing for extraurogenital C. trachomatis and N. gonorrhoeae, and laboratory-developed tests for T. vaginalis and M. genitalium.

RESULTS

Food and Drug Administration-indicated urine C. trachomatis and N. gonorrhoeae screening revealed 39 encounters (2.0%) yielding one or both agents. Via C. trachomatis and N. gonorrhoeae screening that included rectal swab analysis, 264 encounters (13.4%) yielded evidence of either (140 C. trachomatis, 88 N. gonorrhoeae) or both (36 participants) infections. Detection rates for C. trachomatis and N. gonorrhoeae were 1.4% and 0.6% for urine screening and 8.2% and 6.2% for rectal screening, respectively. Off-label screening identified 413 additional encounters with STI (5 T. vaginalis, 396 M. genitalium, 12 with both). Of these identifications, 82.1% were generated from analysis of rectal swabs (4 participants with T. vaginalis, 323 participants with M. genitalium, 12 with both). Overall detection rates of T. vaginalis (0.2% urine, 1.3% rectal) and M. genitalium (9.1% urine, 21.5% rectal) were variable.

CONCLUSIONS

Additive analyte testing, including extraurogenital collections, contributes to comprehensive STI screening within a high-risk demographic.

Availability of Chlamydia trachomatis Testing and Its Importance in the Surveillance of Genital Chlamydial Infection

The reported prevalence of genital Chlamydia trachomatis infection (GCTI) is much lower in low-income countries than that in high-income countries. This study surveyed the prevalence of GCTI in 456 hospitals in Shandong province, China in December 2018. Among the hospitals surveyed, antigen testing, PCR testing, and either antigen or PCR testing were available in 200 (43.9%), 88 (19.3%), and 268 (58.8%) hospitals, respectively. PCR testing was more available in tertiary hospitals than in primary and secondary hospitals (χ² = 28.560, P = 0.000). Significant differences were observed in the availability of antigen testing (χ² = 15.708, P = 0.003), PCR testing (χ² = 22.494, P = 0.000), and either antigen or PCR testing (χ² = 21.729, P = 0.000) among different types of hospitals. In 2018, 1532 cases of GCTI were reported in 99 hospitals. Tertiary hospitals reported more cases than those in primary and secondary hospitals (χ² = 24.082, P = 0.000). The distribution of different types of hospitals that reported GCTI cases was consistent with that of hospitals that provided laboratory testing for GCTI. Antigen and PCR testing were only available in 200 (43.9%) and 88 (19.3%) hospitals, respectively. The results highlighted that the availability of laboratory testing for GCTI in Shandong province was poor, suggesting that the prevalence of GCTI in the province had been sorely underestimated.

Two-phase wash to solve the ubiquitous contaminant-carryover problem in commercial nucleic-acid extraction kits

The success of fundamental and applied nucleic acid (NA) research depends on NA purity, but obtaining pure NAs from raw, unprocessed samples is challenging. Purification using solid-phase NA extractions utilizes sequential additions of lysis and wash buffers followed by elution. The resulting eluent contains NAs and carryover of extraction buffers. Typically, these inhibitory buffers are heavily diluted by the reaction mix (e.g., 10x dilution is 1 µL eluent in 9 µL reaction mix), but in applications requiring high sensitivity (e.g., single-cell sequencing, pathogen diagnostics) it is desirable to use low dilutions (e.g., 2x) to maximize NA concentration. Here, we demonstrate pervasive carryover of inhibitory buffers into eluent when several commercial sample-preparation kits are used following manufacturer protocols. At low eluent dilution (2-2.5x) we observed significant reaction inhibition of polymerase chain reaction (PCR), loop-mediated isothermal amplification (LAMP), and reverse transcription (RT). We developed a two-phase wash (TPW) method by adding a wash buffer with low water solubility prior to the elution step. The TPW reduces carryover of extraction buffers, phase-separates from the eluent, and does not reduce NA yield (measured by digital PCR). We validated the TPW for silica columns and magnetic beads by demonstrating significant improvements in performance and reproducibility of qPCR, LAMP, and RT reactions.

Optimizing bacterial DNA extraction in urine

Urine is an acceptable, non-invasive sample for investigating the human urogenital microbiota and for the diagnosis of sexually transmitted infections. However, low quantities of bacterial DNA and PCR inhibitors in urine may prevent efficient PCR amplification for molecular detection of bacteria. Furthermore, cold temperatures used to preserve DNA and bacteria in urine can promote precipitation of crystals that interfere with DNA extraction. Saline, Dulbecco’s Phosphate Buffered Saline, or Tris-EDTA buffer were added to urine from adult men to determine if crystal precipitation could be reversed without heating samples beyond ambient temperature. Total bacterial DNA concentrations and PCR inhibition were measured using quantitative PCR assays to compare DNA yields with and without buffer addition. Dissolution of crystals with Tris-EDTA prior to urine centrifugation was most effective in increasing bacterial DNA recovery and reducing PCR inhibition. DNA recovery using Tris-EDTA was further tested by spiking urine with DNA from bacterial isolates and median concentrations of Lactobacillus jensenii and Escherichia coli 16S rRNA gene copies were found to be higher in urine processed with Tris-EDTA. Maximizing bacterial DNA yield from urine may facilitate more accurate assessment of bacterial populations and increase detection of specific bacteria in the genital tract.

Comparative analysis of syndromic case management and polymerase chain reaction based diagnostic assays for treatment of Neisseria gonorrhoeae, Chlamydia trachomatis and genital mycoplasmas in patients of genitourinary discharge

To respond to the situation of high prevalence and need for effective treatment for sexually transmitted infections (STIs) in low-resource settings, syndromic diagnostic approach was recommended by the World Health Organization and was adopted by National AIDS Control Organization at the primary health centre level. A retrospective study was undertaken in symptomatic patients attending an STI clinic to validate the syndromic approach for genitourinary discharge syndrome. For aetiological diagnosis, culture and/or polymerase chain reaction was used. An infective aetiology could be established in only 20% (106 of 530) patients. The present data call for an early appraisal and review of the diagnostic policy by national authorities on syndromic case management.

Chlamydia trachomatis and chlamydia-like bacteria: new enemies of human pregnancies

PURPOSE OF REVIEW

This review provides an update on the roles of Chlamydia trachomatis and the related Waddlia chondrophila and Parachlamydia acanthamoebae in miscarriage, stillbirths and preterm labour in humans. A broad audience, including microbiologist, infectiologists, obstetricians and gynaecologists, should be aware of the potential threat of these Chlamydiales for human reproduction.

RECENT FINDINGS

Despite increasing laboratory techniques and possibilities to perform diagnostic tests, the cause of miscarriage is only identified in 50% of the cases. Intracellular bacteria, such as C. trachomatis and Chlamydia-related bacteria, are difficult to detect in routine clinical samples and could represent possible agents of miscarriages. C. trachomatis is considered the world largest sexual transmitted bacterial agent and is associated with adverse pregnancy outcome in human. In the last decade Chlamydia-like organisms, such as W. chondrophila and P. acanthamoebae, have also been associated with adverse pregnancy outcomes in human and/or animals.

SUMMARY

We review here the current evidences for a pathogenic role in humans, the diagnostic approaches and possible treatment options of C. trachomatis, W. chondrophila and P. acanthamoebae.

Mie Scatter and Interfacial Tension Based Real-Time Quantification of Colloidal Emulsion Nucleic Acid Amplification

This work demonstrates for the first time rapid, real-time Mie scatter sensing of colloidal emulsion nucleic acid amplification directly from emulsion droplets. Loop-mediated isothermal amplification is used in this study, and, to our knowledge, has not previously been used in a colloidal emulsion platform. Interfacial tension values (γ) associated with bulk protein adsorption and denaturation at the oil-water interface exhibit characteristic changes in the absence or presence of amplification. In the presence of target and amplicon, emulsions maintain a constant 300-400 nm diameter, whereas emulsions formed with no target control show a rapid decrease in droplet diameter to <100 nm over the first 20 min of incubation. This method is validated using whole bacteria (Staphylococcus aureus MSSA and Escherichia coli O157:H7) and whole virus (Potato virus Y and Zika virus) samples suspended in water, buffer, or serum-like matrices. Short-term formation of colloidal emulsion is quantified via 60° scatter monitoring, where the initial slope of scattering intensity is utilized to confirm target amplification in less than 5 min. The unique benefits of this method render it more cost-effective and field-deployable than existing methods, while being adaptable to a multitude of targets, sample matrices, and nucleic acid amplification tests.

Analysis of laboratory testing results for Chlamydia trachomatis infection in an STI clinic in India: Need for extragenital screening

BACKGROUND

Extragenital sites are believed to serve as hidden reservoirs for ongoing transmission of infection. In addition, treatment for rectal Chlamydia infection is different from that of genital Chlamydia infection. Many cases may be missed if only genital testing is performed.

METHODS

Between September 2015 and August 2016, all male and female attendees at an STI clinic of a tertiary care hospital with genital and or extragenital discharge were screened for CT infection. Samples included endocervical swabs in women, urethral swabs and urine samples in men. Rectal and pharyngeal samples were collected wherever indicated.

RESULTS

Of total of 439 samples collected from 417 patients (245 women and 172 men), samples from women had a high positivity rate than men. (13.6% and 11%). High rates of rectal CT was detected nearly 30.43%. All rectal positive cases except one had no concomitant genital infection.

CONCLUSIONS

Prevalence of extragenital Chlamydia is increasing in men as well as women. What needs to be stressed on is the sexual behaviour of an individual and not the sexual identity. Further studies are needed to help formulate guidelines and recommendations for extragenital screening in a population.

Application of Alternative Nucleic Acid Extraction Protocols to ProGastro SSCS Assay for Detection of Bacterial Enteric Pathogens

As an alternative to automated extraction, fecal specimens were processed by investigational lysis/heating (i.e., manual) and by chromatography/centrifugation (i.e., column) methods. ProGastro SSC and Shiga toxin-producing Escherichia coli (i.e., STEC) indeterminate rates for 101 specimens were 1.0% to 3.0% for automated, 11.9% for manual, and 24.8% to 37.6% for column methods. Following freeze-thaw of 247 specimens, indeterminate rates were 1.6% to 2.4% for manual and 0.8 to 5.3% for column methods. Mean processing times for manual and column methods were 30.5 and 69.2 min, respectively. Concordance of investigational methods with automated extraction was ≥98.8%.

Background review for the '2015 European guideline on the management of Chlamydia trachomatis infections'

SummaryChlamydia trachomatis infections are major public health concerns globally. Of particular grave concern is that the majority of persons with anogenital Chlamydia trachomatis infections are asymptomatic and accordingly not aware of their infection, and this silent infection can subsequently result in severe reproductive tract complications and sequelae. The current review paper provides all background, evidence base and discussions for the 2015 European guideline on the management of Chlamydia trachomatis infections (Lanjouw E, et al. Int J STD AIDS 2015). Comprehensive information and recommendations are included regarding the diagnosis, treatment and prevention of anogenital, pharyngeal and conjunctival Chlamydia trachomatis infections in European countries. However, Chlamydia trachomatis also causes the eye infection trachoma, which is not a sexually transmitted infection. The 2015 European Chlamydia trachomatis guideline provides up-to-date guidance regarding broader indications for testing and treatment of Chlamydia trachomatis infections; clearer recommendation of using validated nucleic acid amplification tests only for diagnosis; advice on (repeated) Chlamydia trachomatis testing; recommendation of increased testing to reduce the incidence of pelvic inflammatory disease and prevent exposure to infection and recommendations to identify, verify and report Chlamydia trachomatis variants. Improvement of access to testing, test performance, diagnostics, antimicrobial treatment and follow-up of Chlamydia trachomatis patients are crucial to control its spread.

Evaluation of a dilution method for non-evaluable results in the detection of Chlamydia trachomatis and Neisseria gonorrhoeae with the Cobas 4800 platform

INTRODUCTION

A variable percentage of samples analysed using the Cobas 4800 assay can give an invalid result by PCR inhibition or erroneous due to incorrect DNA extraction with the Cobas 4800 CT/NG test.

METHOD

An analysis was performed using the vortex agitation and dilution protocol on the original sample (swab or urine) for a total of 116 samples. In order to analyse the sensitivity of this method, 100 samples (swabs and urine) with known results were retested.

RESULTS

A total of 98.3% (114/116) of the samples analysed were resolved with this protocol with 100% agreement after reviewing clinical data, Gram stain, and other samples analysed in parallel from the same patient.

DISCUSSION

The data indicate no loss of sensitivity with this protocol; thus Cobas 4800 users could use this method without the need for alternative methods.

A novel approach for evaluating the performance of real time quantitative loop-mediated isothermal amplification-based methods

Molecular diagnostic measurements are currently underpinned by the polymerase chain reaction (PCR). There are also a number of alternative nucleic acid amplification technologies, which unlike PCR, work at a single temperature. These ‘isothermal’ methods, reportedly offer potential advantages over PCR such as simplicity, speed and resistance to inhibitors and could also be used for quantitative molecular analysis. However there are currently limited mechanisms to evaluate their quantitative performance, which would assist assay development and study comparisons. This study uses a sexually transmitted infection diagnostic model in combination with an adapted metric termed isothermal doubling time (IDT), akin to PCR efficiency, to compare quantitative PCR and quantitative loop-mediated isothermal amplification (qLAMP) assays, and to quantify the impact of matrix interference. The performance metric described here facilitates the comparison of qLAMP assays that could assist assay development and validation activities.

Diagnostic efficacy of a real time-PCR assay for Chlamydia trachomatis infection in infertile women in north India

BACKGROUND & OBJECTIVES

Little is known about the prevalence of Chlamydia trachomatis infection in Indian women with infertility. To improve the diagnosis of C. trachomatis infection in developing countries, there is an urgent need to establish cost-effective molecular test with high sensitivity and specificity. This study was conducted to determine the diagnostic utility of a real time-PCR assay for detention of C. trachomatis infection in infertile women attending an infertility clinic in north India. The in house real time-PCR assay was also compared with a commercial real-time PCR based detection system.

METHOD

Endocervical swabs, collected from 200 infertile women were tested for C. trachomatis by three different PCR assays viz. in-house real time-PCR targeting the cryptic plasmid using published primers, along with omp1 gene and cryptic plasmid based conventional PCR assays. Specimens were also subjected to direct fluorescence assay (DFA) and enzyme immunoassay (EIA) Performance of in-house real time-PCR was compared with that of COBAS Taqman C. trachomatis Test, version 2.0 on all in-house real time-PCR positive sample and 30 consecutive negative samples.

RESULTS

C. trachomatis infection was found in 13.5 per cent (27/200) infertile women by in-house real time-PCR, 11.5 per cent (23/200) by cryptic plasmid and/or omp1 gene based conventional PCR, 9 per cent (18/200) by DFA and 6.5 per cent (7/200) by EIA. The in-house real time-PCR exhibited a sensitivity and specificity of 100 per cent, considering COBAS Taqman CT Test as the gold standard. The negative and positive predictive values of the in-house real time-PCR were 100 per cent. The in-house real time-PCR could detect as low as 10 copies of C. trachomatis DNA per reaction.

INTERPRETATION & CONCLUSIONS

In-house real time-PCR targeting the cryptic plasmid of C. trachomatis exhibited an excellent sensitivity and specificity similar to that of COBAS Taqman CT Test, v2.0 for detection of C. trachomatis infection in women attending an infertility clinic. In an effort to prevent Chlamydia infection associated infertility, we recommend screening of women with infertility due to C. trachomatis infection by in-house molecular method as a cost-effective solution in resource limited settings.

Pre-PCR processing in bioterrorism preparedness: improved diagnostic capabilities for laboratory response networks

Diagnostic DNA analysis using polymerase chain reaction (PCR) has become a valuable tool for rapid detection of biothreat agents. However, analysis is often challenging because of the limited size, quality, and purity of the biological target. Pre-PCR processing is an integrated concept in which the issues of analytical limit of detection and simplicity for automation are addressed in all steps leading up to PCR amplification--that is, sampling, sample treatment, and the chemical composition of PCR. The sampling method should maximize target uptake and minimize uptake of extraneous substances that could impair the analysis--so-called PCR inhibitors. In sample treatment, there is a trade-off between yield and purity, as extensive purification leads to DNA loss. A cornerstone of pre-PCR processing is to apply DNA polymerase-buffer systems that are tolerant to specific sample impurities, thereby lowering the need for expensive purification steps and maximizing DNA recovery. Improved awareness among Laboratory Response Networks (LRNs) regarding pre-PCR processing is important, as ineffective sample processing leads to increased cost and possibly false-negative or ambiguous results, hindering the decision-making process in a bioterrorism crisis. This article covers the nature and mechanisms of PCR-inhibitory substances relevant for agroterrorism and bioterrorism preparedness, methods for quality control of PCR reactions, and applications of pre-PCR processing to optimize and simplify the analysis of various biothreat agents. Knowledge about pre-PCR processing will improve diagnostic capabilities of LRNs involved in the response to bioterrorism incidents.

Applicability of self-obtained urine and vaginal samples for HPV-16, -18, -31 and -45 cervical cancer screening in pregnancy: a pilot cross-sectional study

ABSTRACT: Aim: To conduct a pilot cross-sectional study to evaluate the rates of detection of four common high-risk HPV (hr-HPV) types using first-void urine paired with vaginal self-obtained samples in a nonvaccinated population of pregnant women. We also aimed to compare these results with a matched nonpregnant group in order to test the applicability of self-sampled hr-HPV cervical cancer screening during antenatal visits. Materials & methods: Samples from 550 pregnant women were subjected to hr-HPV-16, -18, -31 and -45 type detection by inhouse PCR and compared with 250 paired urine, vaginal and cervical samples from an age-matched cohort of nonpregnant women. Results: Comparing overall hr-HPV prevalence in urine and vaginal samples between pregnant (15 out of 550; 2.7%) and nonpregnant women (eight out of 250; 3.2%) for each HPV type revealed no significant differences. All paired urine/vaginal samples were both positive for the same type of hr-HPV and there was no positive urine sample with the other samples being negative. Conclusion: hr-HPV detection in pregnant women using self-obtained urine and vaginal samples seems to be a feasible cervical cancer screening method.

Retrospective assessment of transcription-mediated amplification-based screening for Trichomonas vaginalis in male sexually transmitted infection clinic patients

Transcription-mediated amplification (TMA) enhances detection of Neisseria gonorrhoeae and Chlamydia trachomatis from rectal and pharyngeal sources. The utility of TMA for detection of Trichomonas vaginalis has recently been described. We report on the performance of TMA for detection of sexually transmitted infection (STI) agents from extraurogenital sources, with a focus on T. vaginalis. Within a 21-month interval, 1,314 consecutive male patient encounters at an STI clinic resulted in collection of 2,408 specimens for C. trachomatis, N. gonorrhoeae, and T. vaginalis TMA screening. A total of 471 encounters were managed with a single specimen collection (94.9% urine), with 12.7% positive for at least one STI agent. This detection percentage increased to 14.4% with collection of specimens from two sources and to 20.3% with collection from three sources (P = 0.03 versus single-source sampling). A total of 44.4% of encounters were managed by collection of urine and pharyngeal specimens and 19.1% by the addition of a third (rectal) collection. While procurement of urine and rectal specimens resulted in greater detection of C. trachomatis (6.1% and 11.3% rates, respectively) than of other STI agents, 858 pharyngeal specimens yielded a 2.9% T. vaginalis detection rate compared with 2.1% for N. gonorrhoeae and 1.6% for C. trachomatis. All T. vaginalis pharyngeal detections were confirmed by TMA-based alternative target testing. A total of 38.1% of T. vaginalis-positive pharyngeal specimens were derived from symptomatic patient encounters. A total of 85.7% of males with T. vaginalis-positive pharyngeal collections indicated strictly heterosexual preference. Additional specimen source sampling is necessary to make STI screening comprehensive. Incorporation of extraurogenital sources into assessment for T. vaginalis detection may identify additional symptomatic and asymptomatic male STI carriers.

Overcoming inhibition in real-time diagnostic PCR

PCR is an important and powerful tool in several fields, including clinical diagnostics, food analysis, and forensic analysis. In theory, PCR enables the detection of one single cell or DNA molecule. However, the presence of PCR inhibitors in the sample affects the amplification efficiency of PCR, thus lowering the detection limit, as well as the precision of sequence-specific nucleic acid quantification in real-time PCR. In order to overcome the problems caused by PCR inhibitors, all the steps leading up to DNA amplification must be optimized for the sample type in question. Sampling and sample treatment are key steps, but most of the methods currently in use were developed for conventional diagnostic methods and not for PCR. Therefore, there is a need for fast, simple, and robust sample preparation methods that take advantage of the accuracy of PCR. In addition, the thermostable DNA polymerases and buffer systems used in PCR are affected differently by inhibitors. During recent years, real-time PCR has developed considerably and is now widely used as a diagnostic tool. This technique has greatly improved the degree of automation and reduced the analysis time, but has also introduced a new set of PCR inhibitors, namely those affecting the fluorescence signal. The purpose of this chapter is to view the complexity of PCR inhibition from different angles, presenting both molecular explanations and practical ways of dealing with the problem. Although diagnostic PCR brings together scientists from different diagnostic fields, end-users have not fully exploited the potential of learning from each other. Here, we have collected knowledge from archeological analysis, clinical diagnostics, environmental analysis, food analysis, and forensic analysis. The concept of integrating sampling, sample treatment, and the chemistry of PCR, i.e., pre-PCR processing, will be addressed as a general approach to overcoming real-time PCR inhibition and producing samples optimal for PCR analysis.

Genital mycoplasma & Chlamydia trachomatis infections in treatment naïve HIV-1 infected adults

Background & objectives:

Sexually transmitted infections (STIs) enhance the transmission of human immunodeficiency virus (HIV). Thus, screening for STIs is a routine component of primary HIV care. There are limited data for selective screening guidelines for genital mycoplasmas and Chlamydia trachomatis in HIV-infected adults. The aim of the present study was to determine the frequency of genital infections with Ureaplasma spp., Mycoplasma hominis, M. genitalium and C. trachomatis in treatment naïve asymptomatic HIV-1 - infected adults and study their association with CD4+ T-cell count.

Methods:

First-void urine samples were collected from 100 treatment-naïve HIV-1-infected adults and 50 healthy volunteers. C. trachomatis and M. genitalium were detected by polymerase chain reaction (PCR). Ureaplasma spp. and M. hominis were detected by both culture and PCR. Circulating CD4+ cell counts of HIV-1-infected patients were determined from peripheral blood by flow-cytometry.

Results:

C. trachomatis was detected in 7 per cent of HIV-1-infected adults compared to none in control population. Ureaplasma spp. and M. hominis showed infection rates of 6 and 1 per cent in the HIV group and 2 and 0 per cent in the control group, respectively. None of the individuals from the patient and control groups was tested positive for M. genitalium. A significant association was found between CD4 cell count and detection of C. trachomatis in HIV-infected adults (P = 0.01).

Interpretation & conclusions:

Screening of HIV-infected individuals for C. trachomatis infection could be recommended as a routine component of HIV care. The role of mycoplasmas as co-pathogens of the genitourinary tract in HIV-1 infected patients seems to be unlikely. Further longitudinal studies need to be done to confirm these findings.

Competition for DNA binding sites using Promega DNA IQ™ paramagnetic beads

The Promega DNA IQ™ system is easily amenable to automation and has been an integral part of standard operating procedures for many forensic laboratories including those of the Royal Canadian Mounted Police (RCMP) since 2004. Due to some failure to extract DNA from samples that should have produced DNA using our validated automated DNA IQ™-based protocol, the competition for binding sites on the DNA IQ™ magnetic beads was more closely examined. Heme from heavily blooded samples interfered slightly with DNA binding. Increasing the concentration of Proteinase K during lysis of these samples did not enhance DNA recovery. However, diluting the sample lysate following lysis prior to DNA extraction overcame the reduction in DNA yield and preserved portions of the lysates for subsequent manual or automated extraction. Dye/chemicals from black denim lysates competed for binding sites on the DNA IQ™ beads and significantly reduced DNA recovery. Increasing the size or number of black denim cuttings during lysis had a direct adverse effect on DNA yield from various blood volumes. The dilution approach was successful on these samples and permitted the extraction of high DNA yields. Alternatively, shortening the incubation time for cell lysis to 30 min instead of the usual overnight at 56 °C prevented competition from black denim dye/chemicals and increased DNA yields.

Molecular Diagnosis of Sexually Transmitted Chlamydia trachomatis in the United States

Chlamydia, with its Chlamydia trachomatis etiology, is the most common bacterial sexually transmitted infection in the United States and is often transmitted via asymptomatic individuals. This review summarizes traditional and molecular-based diagnostic modalities specific to C. trachomatis. Several commercially available, FDA-approved molecular methods to diagnose urogenital C. trachomatis infection include nucleic acid hybridization, signal amplification, polymerase chain reaction, strand displacement amplification, and transcription-mediated amplification. Molecular-based methods are rapid and reliable genital specimen screening measures, especially when applied to areas of high disease prevalence. However, clinical and analytical sensitivity for some commercial systems decreases dramatically when testing urine samples. In vitro experiments and clinical data suggest that transcription-mediated amplification has greater analytical sensitivity than the other molecular-based methods currently available. This difference may be further exhibited in testing of extragenital specimens from at-risk patient demographics. The development of future molecular testing could address conundrums associated with confirmatory testing, medicolegal testing, and test of cure.

Aetiological agents of urethritis in symptomatic South African men attending a family practice

The objective was to determine the occurrence of four urethral pathogens in urine specimens from symptomatic men using transcription mediated amplification (TMA) assay. Urethral swab and urine specimens from 300 men presenting to a family practitioner were Gram stained and tested for Neisseria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis and Mycoplasma genitalium using three TMA assays respectively. Except for T. vaginalis, the other recognized pathogens viz. N. gonorrhoeae, C. trachomatis and M. genitalium were detected in significantly larger numbers of patients with urethral discharge than in those with burning on micturition (BOM). The overall prevalences were 16.7% for N. gonorrhoeae, 12.3% C. trachomatis, 8.0% T. vaginalis and 17.3% M. genitalium. With regard to microscopic evidence of urethritis, significant associations were found for N. gonorrhoeae and C. trachomatis, but not for M. genitalium and T. vaginalis. This study demonstrated that in symptomatic men attending family practice, M. genitalium and T. vaginalis are also important aetiological agents of urethritis and hence treatment strategies be they syndromic management or laboratory directed should cover for these causative agents. The microscopic diagnosis of urethritis may not be important for treatment strategies. The current syndromic treatment guidelines for developing countries including South Africa need modification.

A German Chlamydia trachomatis screening program employing semi-automated real-time PCR: results and perspectives

BACKGROUND

Genital Chlamydia trachomatis infection is a worldwide public health burden. A screening program for C. trachomatis was therefore initiated by the public health insurers in Germany ("Gemeinsamer Bundesausschuss", GBA) in April 2008.

OBJECTIVES

To estimate C. trachomatis prevalence from screening 115,766 asymptomatic females and 20,033 female patients with unspecific abdominal pain.

STUDY DESIGN

Urine samples (pooled by five for the asymptomatic screening subjects) and cervical swabs were analyzed using semi-automated real-time PCR. Infection prevalence was determined separately in four categories of women, defined by health status (asymptomatic screening vs. non-screening with unspecified symptoms) and test material used. Comparative analyses were stratified by age and pregnancy status.

RESULTS

Experimental evaluation of the assay used revealed a detection limit of 379 genome copies/ml urine. For pooled urine samples, the positive predictive value was 100% whereas the negative predictive value equaled 98.1%. The observed infection prevalence was higher for cervical swabs than for urine samples. Prevalence estimates also differed significantly between pregnant and non-pregnant adolescents (< or = 20 years), irrespective of the test material used (10.2% vs. 7.3% for cervical swabs, 10.9% vs. 6.1% for pooled urine samples).

CONCLUSIONS

Our retrospective study, based upon a very large number of females from all parts of Germany, revealed a high infection prevalence in adolescents, particularly in pregnant adolescents, thereby justifying the screening directive of the German GBA.

Improved forensic DNA analysis through the use of alternative DNA polymerases and statistical modeling of DNA profiles

DNA evidence, linking perpetrators to crime scenes, is central to many legal proceedings. However, DNA samples from crime scenes often contain PCR-inhibitory substances, which may generate blank or incomplete DNA profiles. Extensive DNA purification can be required to rid the sample of these inhibitors, although these procedures increase the risk of DNA loss. Most forensic laboratories use commercial DNA amplification kits (e.g., AmpFlSTR SGM Plus) with the DNA polymerase AmpliTaq Gold as the gold standard. Here, we show that alternative DNA polymerase–buffer systems can improve the quality of forensic DNA analysis and efficiently circumvent PCR inhibition in crime scene samples, without additional sample preparation. DNA profiles from 20 of 32 totally or partially inhibited crime scene saliva samples were significantly improved using Bio-X-Act Short, ExTaq Hot Start, or PicoMaxx High Fidelity instead of AmpliTaq Gold. A statistical model for unbiased quality control of forensic DNA profiles was developed to quantify the results. Our study demonstrates the importance of adjusting the chemistry of the PCR to enhance forensic DNA analysis and diagnostic PCR, providing an alternative to laborious sample preparation protocols.

Evaluation of an automated extraction method for the detection of Chlamydia trachomatis and Neisseria gonorrhoeae by Cobas Amplicor PCR from different sample materials

A commercially available automated device (MagNA Pure LC) was adapted for nucleic acid extraction of urogenital specimen for subsequent PCR detection of Chlamydia trachomatis and Neisseria gonorrhoeae in a clinical laboratory. Results were compared to the standard manual extraction procedure and showed excellent correlation, with even slightly increased sensitivity.

Urine‐based testing forChlamydia trachomatisusing polymerase chain reaction, leucocyte esterase and urethral and cervical smears

The performance of Roche polymerase chain reaction (PCR) Amplicor to detect Chlamydia trachomatis in first-voided urine specimens from 422 males and 456 females attending two clinics for sexually transmitted infections was evaluated in comparison with cultures of urethral and cervical specimens. At the same time, the ability of leucocyte esterase (LE) in first-voided urine and the presence of leucocytes in urethral and cervical smears to identify C. trachomatis-infected individuals based on PCR and culture was determined. The prevalence of C. trachomatis infection was 10.9% in men and 7.7% in women. Sensitivity, specificity, positive predictive value and negative predictive value of Amplicor was 93.5%, 99.7%, 97.7% and 99.2% in males and 91.4%, 99.5%, 94.1% and 99.3% in females. All Chlamydia-infected men were identified by means of a combination of urethritis (4 leucocytes in the urethral smear) and/or a positive LE test in urine, although the specificity was only 42.2%. In women, the combination of urethritis and/or cervicitis and/or a positive LE test identified 85.7% of Chlamydia-infected patients with a specificity of 38.2%. It is concluded that a combination of urethral and/or cervical smears and LE testing of urine can be used as a screening test to select patients, especially males, for specific C. trachomatis testing.

Evaluation of three automated nucleic acid amplification systems for detection of Chlamydia trachomatis and Neisseria gonorrhoeae in first-void urine specimens

A total of 500 first-void urine specimens were tested for the presence of Chlamydia trachomatis and Neisseria gonorrhoeae nucleic acids using ProbeTec ET reagents on a Viper platform (BD Diagnostics, Mississauga, Ontario, Canada), Aptima Combo 2 reagents on a Tigris platform (Gen-Probe, Inc., San Diego, CA), and Abbott RealTime CT/NG reagents on an m2000 platform (Abbott Molecular Diagnostics, Des Plaines, IL). The performance of the three assays for detection of N. gonorrhoeae was comparable, but detection of C. trachomatis by the three assays showed more variation. All three platforms were suitable for the detection of C. trachomatis and N. gonorrhoeae, but additional factors, such as maximum daily specimen throughput, are important in evaluating automated systems for C. trachomatis and N. gonorrhoeae detection in high-volume laboratories.

PCR detection rates of high risk human papillomavirus DNA in paired self-collected urine and cervical scrapes after laser CO2 conization for high-grade cervical intraepithelial neoplasia

OBJECTIVE

To compare the PCR detection rates of high risk human papillomavirus DNA in self-collected urine and cervical scrapes during follow-up of patients treated for HG-CIN by laser CO2 conization.

PATIENTS AND METHODS

52 women who submitted to laser conization for HG-CIN were enrolled into this prospective follow-up study receiving liquid-based cytology and HR-HPV testing by PCR assay on self-collected urine and cervical scrapes before and at 3, 6 and 12 months after treatment. Diagnostic accuracy and predictive values for treatment failure were evaluated for both urinary and cervical HPV testing and follow-up cytology.

RESULTS

3 cases (5.8%) of recurrent HG-CIN occurred during follow-up. Positive margins and HR-HPV persistence resulted to significant risk factors for recurrence (p=0.01). The overall concordance on HR-HPV detection between paired urine and cervical samples was 96.6% and discord trend between agreement rates during follow-up were excluded by overall fixed-effect index (OR 1.03; 95% CI 0.62-1.70). No difference was observed comparing the three- and six-month cumulative sensitivity and NPV for recurrent disease of urinary and cervical HPV detections, with an increase of 5.6% in specificity associated with urinary testing.

CONCLUSIONS

PCR detection of HR-HPV in paired urine and cervical samples during follow-up revealed an excellent concordance, suggesting a potential equivalent role of the two methods within post-treatment follow-up. In our experience HPV testing on self-collected urine was more sensitive than cytology and more specific than cervical HPV detection to predict treatment failure. Larger studies are needed to definitively establish the role of urine-based HPV testing during follow-up.

The evaluation of diagnostic tests for sexually transmitted infections

Diagnostic tests should receive method- and use-effectiveness evaluations. Method-effectiveness evaluations determine sensitivity, specificity and predictive values for new tests. Use-effectiveness evaluations determine how practical or convenient a new test will be in a specific setting and may not be performed in a formal way in North American laboratories. To perform a clinical method evaluation of diagnostic tests, a good relationship between laboratory and clinical personnel is essential. Studies are usually conducted separately on populations of men and women, and should include sampling from different prevalence groups. Test performance comparisons may be made on a single specimen type or on more than one specimen from the same patient, which allows for the expansion of a reference standard and includes the ability of a particular assay, performed on a specimen type to diagnose an infected individual. The following components of the evaluation should be standardized and carefully followed: specimen identification; collection; transportation; processing; quality control; reading; proficiency testing; confirmatory testing; discordant analysis - sensitivity, specificity and predictive value calculations; and record keeping. Methods are available to determine whether sample results are true or false positives or negatives. Use-effectiveness evaluations might determine the stability or durability of supplies and equipment; the logistics of shipping, receiving and storing supplies; the clarity and completeness of test instructions; the time and effort required to process and read results; the subjectivity factors in interpretation and reporting; and the costs. These determinations are usually more apparent for commercial assays than for homemade tests.