Transcription-mediated Amplification Assay Research Articles

Macrolide-Resistant Mycoplasma genitalium Impairs Clinical Improvement of Male Urethritis After Empirical Treatment.

Mycoplasma genitalium (MG) is associated with urethritis in men and could play a role in clinical outcome. We examined clinical improvement of symptoms in men receiving empirical treatment for urethritis and correlated the outcome with Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT), MG, and MG macrolide resistance-associated mutations (MRAM) status. At the sexually transmitted infection clinic in Amsterdam, the Netherlands, empirical treatment for gonococcal urethritis is 1 g ceftriaxone and for nongonococcal urethritis 1 g azithromycin. In 2018 to 2019, we tested urine samples of men with urethritis for CT, NG, and MG using transcription-mediated amplification assays. Mycoplasma genitalium-positive samples were tested for MRAM using quantitative polymerase chain reaction. Two weeks after receiving therapy, men were sent a text message inquiring after clinical improvement. We evaluated 2505 cases of urethritis. The positivity rates of NG, CT, and MG were 26% (648 of 2489), 29% (726 of 2489), and 23% (522 of 2288), respectively. In 768 of 2288 of the cases (34%), no causative agent was detected. Most cases were infected with a single pathogen: NG, 417 of 2288 (18%); CT, 486 of 2288 (21%); and MG, 320 of 2288 (14%). The prevalence of MRAM among MG-positives was 74% (327 of 439). For 642 (25.6%) cases, we could evaluate clinical improvement after treatment of whom 127 (20%) indicated no improvement; 9% (15 of 174) in NG cases, 18% (35 of 195) in CT cases, 14% (4 of 28) in MG wild-type cases, and 40% (38 of 94) in MG-MRAM cases. Clinical improvement in MG-MRAM cases was significantly lower compared with all other groups (P < 0.001). Presence of MG-MRAM is associated with lack of clinical improvement in azithromycin-treated nongonococcal urethritis.

Detection of Neisseria gonorrhoeae or Chlamydia trachomatis from oral wash specimens using the Abbott RealTime CT/NG assay and the Cobas 4800 CT/NG assay: A prospective study

IntroductionIsolating oropharyngeal Neisseria gonorrhoeae (NG) and Chlamydia trachomatis (CT) from oral wash specimens (OWSs) is uncommon. Therefore, we evaluated the performance of the Abbott RealTime CT/NG assay and the Cobas 4800 CT/NG assay in detecting NG and CT in OWSs. MethodsThis multicenter prospective study included 457 patients from 14 medical facilities suspected of having untreated male urethritis or female cervicitis from November 2014 to December 2015. OWSs were collected and tested using the Abbott and Cobas assays. Finally, the discordant results were confirmed using the APTIMA Combo 2 transcription-mediated amplification assay and retested using each assay. ResultsThe sensitivity and specificity of the Abbott assay were 100% and 97.2% for NG and 87.5% and 100% for CT, respectively, and of the Cobas assay were 100% and 98.8% for NG and 93.8% and 99.8% for CT, respectively. Both assays had high negative but low positive predictive values for oropharyngeal NG (Abbott assay: 65.7%, Cobas assay: 82.1%). Based on the definition of “true positive,” the prevalence of oropharyngeal NG and CT were 5.0% and 3.5%, respectively. ConclusionsThe Abbott and Cobas assays using OWSs had high sensitivity and specificity, which can help diagnose oropharyngeal NG and CT. We consider that if a positive result is obtained, the patient should be treated because the negative predictive values were high. However, limited data are available on oropharyngeal NG and CT detection, and further studies are needed to clarify the role of oropharyngeal sexually transmitted infections.

Diagnosing SARS-CoV-2 with Antigen Testing, Transcription-Mediated Amplification and Real-Time PCR.

This study was performed as a head-to-head comparison of the performance characteristics of (1) two SARS-CoV-2-specific rapid antigen assays with real-time PCR as gold standard as well as (2) a fully automated high-throughput transcription-mediated amplification (TMA) assay and real-time PCR in a latent class analysis-based test comparison without a gold standard with several hundred samples in a low prevalence “real world” setting. Recorded sensitivity and specificity of the NADAL and the LumiraDx antigen assays and the Hologic Aptima SARS-CoV-2 TMA assay were 0.1429 (0.0194, 0.5835), 0.7644 (0.7016, 0.8174), and 0.7157 (0, 1) as well as 0.4545 (0.2022, 0.7326), 0.9954 (0.9817, 0.9988), and 0.9997 (not estimable), respectively. Agreement kappa between the positive results of the two antigen-based assays was 0.060 (0.002, 0.167) and 0.659 (0.492, 0.825) for TMA and real-time PCR. Samples with low viral load as indicated by cycle threshold (Ct) values > 30 were generally missed by both antigen assays, while 1:10 pooling suggested higher sensitivity of TMA compared to real-time PCR. In conclusion, both sensitivity and specificity speak in favor of the use of the LumiraDx rather than the NADAL antigen assay, while TMA results are comparably as accurate as PCR, when applied in a low prevalence setting.

Minipool testing for SARS-CoV-2 RNA in United States blood donors.

SARS-CoV-2 RNA prevalence in blood donors from large geographic areas of high community transmission is limited. We tested residual donor plasma minipools (MPs) to determine SARS-CoV-2 RNAemia prevalence in six United States areas. Blood donations collected from 7 March 2020 to 25 September 2020 were tested for SARS-CoV-2 RNA (vRNA) in MP of 6 or 16 donations using the Grifols Procleix SARS-CoV-2 research-use only (RUO) transcription-mediated amplification (TMA) assay. Reactive results were confirmed using an alternate target region TMA assay. Reactive MPs were tested by TMA after serial dilution to estimate viral load. Testing for anti-SARS-CoV-2 antibodies and infectivity was performed. A total of 17,995 MPs corresponding to approximately 258,000 donations were tested for vRNA. Three confirmed reactive MP16 were identified. The estimated prevalence of vRNA reactive donations was 1.16/100,000 (95% CI 0.40, 3.42). The vRNA-reactive samples were non-reactive for antibody, and the estimated viral loads of the (presumed single) positive donations within each MP ranged from <1000 to <4000 copies/ml. When tested, no infectivity was observed in inoculated permissive cell cultures. Blood donation MP-nucleic acid testing (NAT) indicated that SARS-CoV-2 RNAemia is infrequent and, when detected, the vRNA was at low concentrations. Only one RNA-reactive MP could be tested for infectivity for operational reasons and was not infectious in cell culture. These findings support current recommendations from international and national regulatory agencies to not screen donors by NAT.

Analytical Performance Characteristics of a New Transcription-Mediated Amplification Assay for Treponema pallidum.

ABSTRACTThis study evaluated the performance characteristics of a new research-use-only transcription-mediated amplification (TMA) assay for the detection of rRNA from Treponema pallidum. Analytical sensitivity determined using dark-field microscopy-quantitated T. pallidum was 1.4 organisms/ml (95% confidence interval [CI], 0.7 to 6.33 organisms/ml). Dilution of in vitro-transcribed (IVT) T. pallidum RNA in Aptima sample transport medium (STM) yielded 100% positivity (n = 3) at 10 copies/ml (4 copies/reaction). Analytical specificity testing of nontarget microorganisms (n = 59), including the closely related nonsyphilis treponemes Treponema denticola and Treponema phagedenis, yielded 0% positivity. TMA testing of mucosal swab specimens collected from men who have sex with men (MSM) attending a sexually transmitted disease clinic yielded 1.8% (17/944) positive results. A collection of 56 serum specimens obtained from a separate cohort of patients with known rapid plasma reagin (RPR) statuses and clinical diagnoses of syphilis was 19.6% (11/56) TMA positive overall and 29.7% (11/37) positive among subjects with syphilis diagnoses, including 8 (36.3%) of 22 persons with primary or secondary syphilis, 2 (20%) of 10 persons with early latent syphilis, and 1 (20%) of 5 persons with late latent or unstaged syphilis. None (0%) of the 18 RPR-positive sera from patients with histories of treated syphilis were TMA positive. These results show that TMA is an analytically sensitive and specific method for the detection of T. pallidum rRNA and is compatible with serum specimens in addition to pharyngeal and rectal mucocutaneous swab specimens. Automated real-time TMA testing for T. pallidum may be useful as an adjunctive method with serology for screening and diagnostic testing of selected patient populations for syphilis.

Evaluation of the analytical performance and specificity of a SARS-CoV-2 transcription-mediated amplification assay

The ongoing severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic requires fast and accurate high-throughput diagnostic tools.To evaluate the analytical performance of the Hologic Aptima transcription-mediated amplification (TMA) assay for detection of SARS-CoV-2 RNA from respiratory samples we analysed 103 clinical and proficiency panel samples pre-tested by real-time RT-PCR (Altona, RealStar) and found a positive percent agreement (sensitivity) of 95.7 % and a negative percent agreement (specificity) of 100 %. The limit of detection of the Aptima test was 150 copies/mL determined as 95 % detection probability.To further assess the Aptima assay’s specificity we prospectively analysed 7545 clinical specimens from the upper and lower respiratory tract sent for the purpose of routine SARS-CoV-2 screening. SARS-CoV-2 RNA was detected in 16/7545 (0.2 %) samples by the TMA assay and confirmed independently by the Xpert SARS-CoV-2 RT-PCR (Cepheid); in one case a previous discrepant result was confirmed as true SARS-CoV-2 infection in a subsequent sample from the same patient.Results from the Aptima SARS-CoV-2 TMA assay agreed well with RT-PCR and showed an excellent specificity in a large number of routine specimens despite the low prevalence at that time of the pandemic, indicating that this assay can be used even for screening purposes.

Evaluating the prevalence and risk factors for macrolide resistance in Mycoplasma genitalium using a newly developed qPCR assay.

Mycoplasma genitalium (MG) is a sexually transmitted bacterium in which macrolide resistance is rapidly increasing, limiting treatment options. We validated a new assay to detect the presence of macrolide resistance-associated mutations in MG (MG-MRAM). In 2018, symptomatic and asymptomatic clients visiting sexually transmitted infections (STI) clinics in Amsterdam or The Hague were tested for MG using transcription mediated amplification (TMA) assays. The sensitivity to detect MG of the newly developed MG-MRAM qPCR was compared to the MgPa qPCR, both in relation to the TMA assay. For the sensitivity and specificity to detect relevant mutations the MG-MRAM qPCR was compared to 23SrRNA sequencing analysis. The qPCR was subsequently used to determine the presence of MG-MRAM at different anatomical locations and to identify risk factors for MG-MRAM. MG-positive clients (402) providing 493 MG-positive samples were included. In total 309/493 (62.7%) samples from 291 (72.4%) clients were successfully typed with the MG-MRAM qPCR. The MG-MRAM qPCR had a sensitivity of 98.6% (95%CI 91.1%-99.9%) and specificity of 94.1% (95%CI 78.9%-99.0%) to detect MG-MRAM compared to sequencing analysis. Infection with MG-MRAM was detected in 193/291 (66.3%) clients: in 129/178 (72.5%) men and 64/113 (56.6%) women (p = 0.005). Prevalence of MG-MRAM was significantly higher in men, clients with a higher education, HIV-positive clients and clients with >10 sexual partners in the previous six months, but in multivariable analysis no factor was significantly associated with MG-MRAM presence. Since MG-MRAM prevalence was very high, testing for MG-MRAM is essential if treatment for MG is considered, and can be performed with this sensitive and specific qPCR test in routine diagnostics.

Current Diagnostic Techniques used to detect SARS-COV-2- Coronavirus

The corona virus disease being aware commonly as Covid-19 in passing days among common masses is a novel viral illness of the systema respiratorium, causing a sustained pandemic which is in particular characterized by atypical pneumonia with specific symptoms of mild fever, runny nose with secreted fluid similar to flu, hypoxia, myalgia, anosmia, ageusia, shortness of breath, normal or decreased leukocyte count, ground glass opacities, sore throat and cough without phlegm. It is caused by an epidemic referred as SARS CoV-2 with abbreviation of severe acute respiratory syndrome coronavirus-2 nowadays. The procedures to be adopted for the diagnosis of COVID-19 should be based not only on clinical but epidemiological agents also and anyways stand on the link to an assessment and likelihood of the infection. The SARS CoV-2 is diagnosed with different test techniques like serological, molecular and others but most common for it is RT-PCR which is widely used and most reliable one to authenticate the findings of this disease. In the earlier times its detection was too an issue but luckily soon after its threat the scientists and organizations involved themselves and developed strong techniques to get reliable and accurate results with peaceful outcomes. The including such techniques are like immunological assay, amplification technique like RT-PCR (Spin column-and poly amino ester magnetic nanoparticle (pcMNPs) extraction method. Real-time nanopore target sequencing (NTS) and amplification methods) while on the other hands latest in use techniques are Isothermal nucleic acid amplification (as their subcategories include transcription-mediated amplification (TMA), Loop-mediated isothermal amplification (LAMP), rolling circle amplification (RCA) and clustered regularly interspaced short palindromic repeats (CRISP), and TMA assay). The novel techniques developed for this particular purpose are Biosensors, Localized surface plasma resonance (LSPR) sensor, the Field effect transistor (FET) and Cell-based potentiometric biosen.

Extragenital Mycoplasma genitalium infections among men who have sex with men

ObjectivesThere are limited data on the prevalence of Mycoplasma genitalium (Mgen) coinfection with rectal chlamydia (Chlamydia trachomatis (CT)) and rectal gonorrhoea (Neisseria gonorrhoeae (NG)) infections and few studies examining the...

Mycoplasma genitalium infection among HIV-infected pregnant African women and implications for mother-to-child transmission of HIV.

Many sexually transmitted infections increase risk of mother-to-child transmission (MTCT) of HIV, but the effect of Mycoplasma genitalium is not known. We hypothesized that M. genitalium infection would be common among HIV-infected pregnant women and could be associated with in-utero and intrapartum MTCT. Observational case-cohort study. The current study used specimens from a Kenyan perinatal MTCT cohort (1999-2005) involving HIV-infected women and their infants, who received short-course zidovudine for prevention of MTCT. Vaginal swabs collected at 32 weeks gestation were tested for M. genitalium using a transcription-mediated amplification assay. Infant perinatal HIV infection was determined at birth and 4 weeks of age by DNA PCR. Using a case-cohort design, a random sample was generated with 3 : 1 control : case ratio; prevalence and correlates of M. genitalium were assessed with chi-squared and t tests; predictors of infant outcomes were analyzed using logistic regression. Among 220 HIV-infected pregnant women evaluated, 47 women (21.4%) had M. genitalium. Antenatal M. genitalium infection was associated with higher HIV RNA in plasma (5.0 vs. 4.6 log10 copies/ml in M. genitalium-positive vs. M. genitalium-negative women, P = 0.02) at 32 weeks. Women with M. genitalium were less likely to report prior sexually transmitted infections and genital ulcers (both P = 0.05). There was no association found between exposure to M. genitalium and perinatal MTCT (odds ratio = 0.72, 95% confidence interval 0.35, 1.51, P = 0.39). Vaginal M. genitalium infection was frequently detected among Kenyan HIV-infected pregnant women and was associated with higher plasma HIV levels, but was not associated with perinatal transmission of HIV.

Comparison of Transcription-Mediated Amplification and Real-Time PCR Assays for Hepatitis B Virus DNA Quantitation in Serum.

The quantification of hepatitis B (HBV) DNA in serum is critical to identify patients requiring antiviral therapy and to monitor the response to treatment. This study describes the evaluation of the Aptima HBV Quant Dx assay (Aptima HBV) performed on the automated Panther system. Aptima HBV was linear from 1.70 to 7.70 log10 IU/mL with a commercial reference panel, as well as clinical specimens representing genotypes B and C, and total imprecision, as measured by the percentage coefficient of variation (%CV) at 2.0 log10 IU/mL was <10%. The specificity of Aptima HBV was 94.7% (126/133) and 96.6% (84/87) for serum specimens from individuals without HBV exposure and individuals with resolved HBV infection, respectively. The qualitative agreement and quantitative accuracy of Aptima HBV was compared to the COBAS AmpliPrep/COBAS TaqMan HBV Test v2.0 (CAP/CTM). Overall agreement was 90.8% (187/206) with a κ statistic of 0.708 (standard error, 0.063; 95% CI, 0.585-0.831). Passing-Bablok regression revealed a regression line of y = 0.953x + 0.075 (95% CI of the slope, 0.883-1.011; intercept, -0.100 to 0.299), and Bland-Altman analysis (Aptima - CAP/CTM) showed a slight negative bias (-0.054 log10 IU/mL, and 95% limits of agreement of -1.093 to 0.984). The Aptima HBV test affords a suitable alternative to CAP/CTM for serum virus load testing and provides a key component of the diagnostic algorithm for the global eradication of viral hepatitis.

Meta-analysis of the Cepheid Xpert® CT/NG assay for extragenital detection of Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) infections.

The literature indexed on PubMed.gov was searched. Included studies were those that were an evaluation of the Xpert CT/NG assay with rectal and/or pharyngeal specimen types compared with another nucleic acid amplification test (NAAT), the Aptima transcription mediated amplification assay. A full Bayesian method was used for bivariate fixed-effect meta-analysis of positive and negative per cent agreement and pooled estimates (and 95% confidence intervals (CI)) were presented for each. The pooled positive and negative per cent agreement for detection of CT in rectal specimens was 89.72% (95% CI: 84.97%, 93.64%) and 99.23% (95% CI: 98.74%, 99.60%), and in pharyngeal specimens, they were 89.96% (95% CI: 66.38%, 99.72%) and 99.62% (95% CI: 98.95%, 99.95%) respectively. For NG detection in rectal specimens, the pooled positive and negative per cent agreement was 92.75% (95% CI: 87.91%, 96.46%) and 99.75% (95% CI: 99.46%, 99.93%), and in pharyngeal specimens, they were 92.51% (95% CI: 85.84%, 97.18%) and 98.56% (95% CI: 97.69%, 99.23%) respectively. It was found that the Xpert CT/NG assay performed similarly to the Aptima transcription mediated amplification assay for the detection of CT and NG in extragenital specimens. The Xpert assay has the benefit of providing faster results at the point-of-care, thus reducing the turnaround time for results, potentially enabling same-day treatment.

436 Sampling technique and detection rates of oropharyngeal and anorectal gonorrhoea using nucleic acid amplification tests in men who have sex with men

The objective of this study was to examine the associations between clinicians’ self-reported sampling technique and the detection rate of gonorrhoea at the oropharynx and rectum using a highly sensitive nucleic acid amplification test (NAAT). We analysed oropharyngeal and anorectal gonorrhoea swab results for men who have sex with men attending the Melbourne Sexual Health Centre (MSHC) between March 2015 and December 2016. Swabs were tested by NAAT using the Aptima Combo 2 transcription-mediated amplification assay due to its high sensitivity. Clinicians at MSHC were invited to complete a questionnaire on sampling techniques in November 2016. Univariable generalised estimating equations (GEE) logistic regressions were performed to determine the association between gonorrhoea detection rates and clinicians’ sampling technique. Patients’ epidemiological risk factors were included in the multivariable GEE logistic model. A total of 2605 oropharyngeal gonorrhoea and 2392 anorectal gonorrhoea swab results were analysed. There was no significant difference in the detection rates of gonorrhoea between the 23 clinicians at the oropharynx (range 3.6%-16.9%, median 8.2%, P=0.302) or and anorectum (range 2.4%-17.3%, median 10.5%, p=0.177). Variations in clinicians’ self-reported sampling technique were not associated with oropharyngeal or anorectal gonorrhoea detection rates after adjusting for patients’ epidemiological risk factors.

Deceased organ donor screening for human immunodeficiency virus, hepatitis B virus and hepatitis C virus: Discordant serology and nucleic acid testing results.

Before the 2014 policy change pertaining to infectious disease screening, many organ procurement organizations (OPOs) were supplementing serologic screening of deceased organ donors with nucleic acid testing (NAT) for human immunodeficiency virus (HIV-1), hepatitis B virus (HBV), and hepatitis C virus (HCV). The number of seronegative, NAT-positive donors has not been directly measured. HIV, HBV, and HCV screening results of 11229 donor referrals evaluated from 2010 to 2013 were obtained from 3 OPO-affiliated laboratories, capturing 35% of all donors in the United States. Laboratories used either polymerase chain reaction assay or transcription-mediated amplification assay to test 9643 deceased donors by NAT. The NAT results were positive in 21 (0.2%), 1 (0.02%), and 11 (0.1%) donors who were seronegative for HIV, HBV, and HCV, respectively. All discordant HIV-1 results were from one laboratory using a polymrease chain reaction assay. Thirteen of the reactive HIV NAT results in seronegative referrals were repeated and were non-reproducibly positive (NRP). Ten (0.1%), 452 (7.8%), and 197 (2.2%) of HIV-, HBV-, and HCV-seropositive donors, respectively, were negative by NAT. This study highlights the importance of robust quality assurance to minimize NRP NAT results. NAT may allow for increased utilization of organs from HBV- and HCV-seropositive, NAT-negative donors.

Sampling technique and detection rates of oropharyngeal and anorectal gonorrhoea using nucleic acid amplification tests in men who have sex with men

ObjectivesThe objective of this study was to examine the associations between clinicians’ self-reported sampling technique and the detection rate of gonorrhoea at the oropharynx and anorectum using a highly sensitive...

A comparison study between GeXP-based multiplex-PCR and serology assay for Mycoplasma pneumoniae detection in children with community acquired pneumonia

BackgroundDiagnosis of community-acquired pneumonia (CAP) caused by Mycoplasma pneumoniae (Mp) in children has been hampered by difficulty in obtaining convalescent serum and time constraints. In this study, the two diagnostic assays that targeted respectively on Mp-antibody and Mp-DNA were retrospectively investigated.MethodsA total of 3146 children were clinically diagnosed to have CAP and were confirmed by chest X-ray during March 2015 to February 2016 in Children’s hospital of Hebei Province (China). Both of the sera and sputum samples were collected in 24 h after their admission. The Mp-antibody was examined by the passive particle agglutination assay and a fourfold or greater increase of antibody titers of paired sera or≧1:160 titer of single serum was set as the serology positive. Mp-DNA in the sputum samples was tested by a multiplex-PCR method named GeXP assay (multiplex PCR combined with automated capillary electrophoresis). In order to eliminate the false positive results caused by the asymptomatic carriage after infected by M. pneumoniae, the inconsistent samples were tested by the real-time isothermal transcription-mediated RNA amplification assay (SAT).ResultsThe inter-rated agreement test was performed in 3146 CAP patients, with a highest kappa value in the school-age children as 0.783. There were 6.29% (198/3146) cases showed inconsistent results determined by GeXP and serology assay. All of the 19 GeXP(+)/Serology (−) samples and a randomly chosen 27 from 179 GeXP(−)/Serology (+) samples were tested by SAT assay, and a 97.8% diagnosis agreement was observed between SAT and GeXP assay, but not with the serology assay. In addition, patients who were detected only by serology or only by multiplex-PCR were significantly younger than those with both methods positive (3.0 and 1.5 years vs. 5.0 years, p < 0.01). The Viral-Mp coinfection accounted for 37.0% (97/262), which was more common in winter and spring (p < 0.05) and in the infantile group (p < 0.01), compared to the pure Mp positive ones.ConclusionIn some children CAP cases, the Mp laboratory diagnosis was inconsistent between serology and multiplex-PCR assay. Verified by the SAT assay, the GeXP showed a more sensitive and reliable performance compared with the serology assay. Furthermore, employing the multiplex-PCR could provide more information on the associated pathogens for clinical assessment of CAP.

Mycoplasma genitalium: Accurate Diagnosis Is Necessary for Adequate Treatment.

Mycoplasma genitalium is very difficult to grow in culture but has been more able to be studied for disease associations since the advent of research molecular amplification assays. Polymerase chain reaction (PCR) and other molecular assays have demonstrated an association with adverse disease outcomes, such as urethritis or nongonococcal urethritis in men and adverse reproductive sequelae in women-for example, cervicitis, endometritis, and pelvic inflammatory disease (PID), including an association with risk for human immunodeficiency virus. The lack of commercially available diagnostic assays has limited widespread routine testing. Increasing reports of high rates of resistance to azithromycin detected in research studies have heightened the need available commercial diagnostic assays as well as standardized methods for detecting resistance markers. This review covers available molecular methods for the diagnosis of M. genitalium and assays to predict the antibiotic susceptibility to azithromycin. A PubMed (US National Library of Medicine and National Institutes of Health) search was conducted for literature published between 2000 and 2016, using the search terms Mycoplasma genitalium, M. genitalium, diagnosis, and detection. Early PCR diagnostic tests focused on the MPa adhesion gene and the 16S ribosomal RNA gene. Subsequently, a transcription-mediated amplification assay targeting ribosomes was developed and widely used to study the epidemiology of M. genitalium. Newer methods have proliferated and include quantitative PCR for organism load, AmpliSens PCR, PCR for the pdhD gene, a PCR-based microarray for multiple sexually transmitted infections, and multiplex PCRs. None yet are cleared by the Food and Drug Administration in the United States, although several assays are CE marked in Europe. As well, many research assays, including PCR, gene sequencing, and melt curve analysis, have been developed to detect the 23S ribosomal RNA gene mutations that confer resistance to azithromycin. One recently developed assay can test for both M. genitalium and azithromycin resistance mutations at the same time. It is recommended that more commercial assays to both diagnose this organism and guide treatment choices should be developed and made available through regulatory approval. Research is needed to establish the cost-effectiveness of routine M. genitalium testing in symptomatic patients and screening in all individuals at high risk of acquiring and transmitting sexually transmitted infections.

Performance evaluation of the Aptima® HCV Quant Dx assay for hepatitis C virus (HCV) RNA detection and quantification in comparison to the Abbott RealTime HCV assay

BackgroundThe Aptima HCV Quant Dx assay (Aptima) is a real-time transcription-mediated amplification assay CE-approved for the diagnosis and monitoring of hepatitis C virus (HCV) infection. ObjectiveAptima’s analytical performance was compared to the Abbott RealTime HCV assay (RealTime) in a clinical routine setting. Study designOverall 295 clinical plasma samples (117 prospective/fresh; 178 retrospective/frozen) from HCV-infected patients were tested in Aptima and RealTime to determine concordance on qualitative and quantitative results. Linearity and precision at low viral loads (VLs; 0.8–3.3LogIU/mL) was tested using dilutions of the 5th WHO standard, in 10 and 20 replicates in the two assays, respectively. The ability to measure different HCV genotypes and accuracy were analyzed using the Seracare EQA panel. ResultsInter-assay agreement for qualitative results (prospective samples) was 88% (kappa=0.78). For the 127 samples with quantitative results in both assays, Aptima yielded on average slightly higher values (by 0.24LogIU/mL; Bland–Altman method) than RealTime. Concordance between assay results was excellent (R=0.98). At low VLs (0.8–3.3LogIU/mL), Aptima demonstrated good linearity and precision, similar to RealTime. Aptima detected and accurately quantified all main HCV genotypes. ConclusionsAptima demonstrated excellent precision, linearity, and accuracy in all genotypes tested. Good concordance was observed between Aptima and RealTime assays in clinical samples. The performance of the Aptima assay, on the fully automated Panther platform, makes it an excellent candidate for the detection and monitoring of HCV RNA in plasma and serum samples.

The new frontier of diagnostics: Molecular assays and their role in infection prevention and control.

Recent advances in technology over the last decade have propelled the microbiology laboratory into a pivotal role in infection prevention and control. The rapid adaptation of molecular technologies to the field of clinical microbiology now greatly influences infectious disease management and significantly impacts infection control practices. This review discusses recent developments in molecular techniques in the diagnosis of infectious diseases. It describes the basic concepts of molecular assays, discusses their advantages and limitations, and characterizes currently available commercial assays with respect to cost, interpretive requirements, and clinical utility.

Quantitative Real-Time Polymerase Chain Reaction for the Diagnosis of Mycoplasma genitalium Infection in South African Men With and Without Symptoms of Urethritis.

This study was done to diagnose Mycoplasma genitalium infection based on bacterial load in urine specimens from symptomatic and asymptomatic men. Urine specimens from 94 men with visible urethral discharge, 206 with burning on micturition and 75 without symptoms presenting to a family practitioner were tested for M. genitalium as well as Neisseria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis by transcription-mediated amplification assays. A quantitative polymerase chain reaction assay was used to determine the bacterial load for all specimens in which M. genitalium was the only organism detected. Among the 375 specimens collected, M. genitalium was detected in 59 (15.7%) men (both symptomatic and asymptomatic) using the transcription-mediated amplification assay, and in 45 (12.0%) of the total population, it was the only pathogen detected. One or more pathogens were detected in 129 (43%) of the symptomatic men, with N. gonorrhoeae in 50 (16.7%); C. trachomatis in 37 (12.3%) and T. vaginalis present in 24 (8.0%) patients. Among the 17 patients where mixed infections were detected, M. genitalium with N. gonorrhoeae was the most common (11/17; 64.7%). Patients with visible urethral discharge had significantly higher M. genitalium concentrations than those with burning on micturition. The median M. genitalium load in symptomatic men was significantly higher than that in asymptomatic men. This study confirms the high prevalence of M. genitalium among men with urethritis in South Africa and demonstrates that there is a strong association with M. genitalium bacterial load and clinical urethritis. As the number of organisms increased, the severity of the symptoms increased, an indication of the role that the organism plays in disease progression.