Multiplex polymerase chain reaction-based reverse line blot hybridization assay to detect common genital pathogens

Microscopy of Gram-stained urethral smear in the diagnosis of urethritis: Which threshold value should be selected?

The aim of this study was to investigate the sensitivity of GSS in the diagnosis of urethritis in patients who present to the outpatient clinic with symptoms of urethritis. Sixty-three male patients who presented to our outpatient clinic with symptoms of urethritis between January and March 2018 were evaluated. Urethral smear samples obtained from patients were evaluated both by GSS examination and by Real-time Multiplex Polymerase Chain Reaction (rt-MPCR) assay. The sensitivity and specificity of GSS in detecting gonococcal urethritis (GU) and nongonococcal urethritis (NGU) were calculated for threshold values of ≥5 and ≥2 PMNL/HPF. The mean age was 33.2 ± 7.1 years. According to the rt-MPCR results, 14 patients had GU and 27 patients had NGU. A threshold value of ≥5 PMNL/HPF in the GSS demonstrated 92.9% sensitivity in the diagnosis of GU and 55.6% sensitivity in the diagnosis of NGU. A threshold value of ≥2 PMNL/HPF reached 100% sensitivity for GU and 92.6% sensitivity for NGU. A cut-off value of ≥5 PMNL/HPF in the GSS has low sensitivity in the diagnosis of NGU. On the other hand, a threshold value of ≥2 PMNL/HPF seems to have higher sensitivity in the diagnosis of both GU and NGU.

Molecular typing of Chlamydia trachomatis: An overview

Urogenital infection due to Chlamydia trachomatis (CT) is one of the most common bacterial sexually transmitted infections (STIs) and is a major public health problem worldwide. Molecular characterisation of CT is important for understanding the pathophysiological mechanisms of chlamydial disease and its transmission dynamics in sexual networks. Traditionally, strain typing of CT was based on serotyping methods characterising the major outer membrane protein (MOMP). With the advent of polymerase chain reaction and sequencing the era of molecular typing began. Molecular characterization of CT strains is based on sequence analysis of ompA gene encoding MOMP. However, in due course of time, improvements were made to enhance the discriminatory power of sequencing and quality of epidemiological information. New high-resolution genotyping methods using multiple loci such as multilocus sequence typing (MLST) and multiple loci variable number of tandem repeats (MLVA) were developed but were unable to differentiate mixed infections (MIs). The development of DNA-hybridisation methods emerged as a major breakthrough in detecting MIs. Although MLST and MLVA are more discriminative than other genotyping methods, they are laborious and expensive. DNA microarray technique is an affordable alternative for genotyping. Since recombination is widespread in the CT genome, ompA is not a reliable marker for phylogenetic studies; hence, whole genome sequencing may provide maximum phylogenetic resolution of CT strains. A descriptive review is provided of the various molecular CT typing methods. The vital information gained can be used for formulating screening programmes, targeted prevention and optimising therapeutic measures aiming to reduce disease transmission.

Multiplex PCR testing for nine different sexually transmitted infections

Current sexually transmitted infection (STI) testing is not optimal due to delays in reporting or missed diagnoses due to a lack of comprehensive testing. The FilmArray® (BioFire Diagnostics, LLC, Salt Lake City, Utah) is a user-friendly, fully automated, multiplex PCR system that is being developed for rapid point-of-care use. A research-use-only STI panel including multiple PCR primer sets for each organism was designed to detect Chlamydia trachomatis, Neisseria gonorrhoeae, Treponema pallidum, Trichomonas vaginalis, Mycoplasma genitalium, Ureaplasma urealyticum, Haemophilus ducreyi, and herpes simplex virus (HSV) types 1 and 2. Standard clinical testing included Gram stain, nucleic acid amplification, wet mount examination, herpes simplex virus culture, and syphilis IgG. Standard clinical tests were not available for all the organisms tested by the FilmArray STI panel. Two hundred and ninety-five clinical specimens from 190 subjects were directly compared to standard testing. Urine (n = 146), urethral/cervical swabs (31), oral swabs (60), rectal swabs (43), and ulcer swabs (15) were tested. Among the tested samples, FilmArray detected C. trachomatis in 39 (13%), N. gonorrhoeae in 20 (7%), T. vaginalis in nine (3%), HSV 1 in five (2%), HSV 2 in five (2%), U. urealyticum in 36 (12%), M. genitalium in eight (3%), and T. pallidum in 11 (4%). Concordance between the FilmArray STI panel and standard nucleic acid amplification testing for C. trachomatis was 98% and for N. gonorrhoeae was 97%. Multiplex PCR STI testing has the potential to improve public health by providing rapid, sensitive, and reliable results within the clinic or nearby laboratory.

Modern approaches and prospects of development of laboratory diagnostics for sexuallytransmitted infections

The authors provide a comparison of modern approaches to the use of well-known laboratory methods for diagnostics of syphilis, gonorrhea, trichomoniasis and urogenital clamidiosis, which are approved in the world science and practice. They also examine promising directions in the development of up-to-date laboratory technologies (biomicrochips, multiprimer PCR, mass spectrometry, PLEX-ID technology, immunoblotting, chemiluminescence immunoassay (CLIA), xMAP, pyrosequencing) for detecting STD pathogens, which is necessary to make an etiological diagnosis and determine efficient methods of treatment minimizing the period of time required for examination of patients.

Multiplex PCR and reverse line blot hybridization assay (mPCR/RLB)

Multiplex PCR/Reverse Line Blot Hybridization assay allows the detection of up to 43 molecular targets in 43 samples using one multiplex PCR reaction followed by probe hybridization on a nylon membrane, which is re-usable. Probes are 5' amine modified to allow fixation to the membrane. Primers are 5' biotin modified which allows detection of hybridized PCR products using streptavidin-peroxidase and a chemiluminescent substrate via photosensitive film. With low setup and consumable costs, this technique is inexpensive (approximately US$2 per sample), high throughput (multiple membranes can be processed simultaneously) and has a short turnaround time (approximately 10 hours). The technique can be utilized in a number of ways. Multiple probes can be designed to detect sequence variation within a single amplified product, or multiple products can be amplified simultaneously, with one (or more) probes used for subsequent detection. A combination of both approaches can also be used within a single assay. The ability to include multiple probes for a single target sequence makes the assay highly specific. Published applications of mPCR/RLB include detection of antibiotic resistance genes(1,2), typing of methicillin-resistant Staphylococcus aureus(3-5) and Salmonella sp(6), molecular serotyping of Streptococcus pneumoniae(7,8), Streptococcus agalactiae(9) and enteroviruses(10,11), identification of Mycobacterium sp(12), detection of genital(13-15) and respiratory tract(16) and other(17) pathogens and detection and identification of mollicutes(18). However, the versatility of the technique means the applications are virtually limitless and not restricted to molecular analysis of micro-organisms. The five steps in mPCR/RLB are a) Primer and Probe design, b) DNA extraction and PCR amplification c) Preparation of the membrane, d) Hybridization and detection, and e) Regeneration of the Membrane.