Development and Evaluation of a Point-of-Care Test in a Low-Resource Setting with High Rates of Chlamydia trachomatis Urogenital Infections in Fiji

Loop-Mediated Isothermal Amplification (LAMP): Potential Point-of-Care Testing for Vulvovaginal Candidiasis

PURPOSE

The aim of this study is to establish a loop-mediated isothermal amplification (LAMP) method for the rapid detection of vulvovaginal candidiasis (VVC).

METHODS

We developed and validated a loop-mediated isothermal amplification (LAMP) method for detecting the most common Candida species associated with VVC, including C. albicans, N. glabratus, C. tropicalis, and C. parapsilosis. We evaluated the specificity, sensitivity, positive predictive value (PPV), negative predictive value (NPV), and Kappa value of the LAMP method to detect different Candida species, using the conventional culture method and internal transcribed spacer (ITS) sequencing as gold standards and smear Gram staining and real-time Rolymerase Chain Reaction (PCR) as controls.

RESULTS

A total of 202 cases were enrolled, of which 88 were VVC-positive and 114 were negative. Among the 88 positive patients, the fungal culture and ITS sequencing results showed that 67 cases (76.14%) were associated with C. albicans, 13 (14.77%) with N. glabratus, 5 (5.68%) with C. tropicalis, and 3 (3.41%) with other species. Regarding the overall detection rate, the LAMP method presented sensitivity, specificity, PPV, NPV, and Kappa values of 90.91%, 100%, 100%, 93.4%, and 0.919, respectively. Moreover, the LAMP had a specificity of 100% for C. albicans, N. glabratus, and C. tropicalis, with a sensitivity of 94.03%, 100%, and 80%, respectively. Moreover, the microscopy evaluation had the highest sensitivity, while the real-time PCR was less specific for C. albicans than LAMP. In addition, CHROMagar Candida was inferior to LAMP in detecting non-albicans Candida (NAC) species.

CONCLUSIONS

Based on the cost-effective, rapid, and inexpensive characteristics of LAMP, coupled with the high sensitivity and specificity of our VVC-associated Candida detection method, we provided a possibility for the point-of-care testing (POCT) of VVC, especially in developing countries and some laboratories with limited resources.

Point of care detection of SARS-CoV-2 antibodies and neutralisation capacity-lateral flow immunoassay evaluation compared to commercial assay to inform potential role in therapeutic and surveillance practices

Introduction

As the COVID-19 pandemic moves towards endemic status, testing strategies are being de-escalated. A rapid and effective point of care test (POCT) assessment of SARS-CoV-2 immune responses can inform clinical decision-making and epidemiological monitoring of the disease. This cross-sectional seroprevalence study of anti-SARS-CoV-2 antibodies in Irish healthcare workers assessed how rapid anti-SARS-CoV-2 antibody testing can be compared to a standard laboratory assay, discusses its effectiveness in neutralisation assessment and its uses into the future of the pandemic.

Methods

A point of care lateral flow immunoassay (LFA) detecting anti-SARS-CoV-2 spike (S)-receptor binding domain (RBD) neutralising antibodies (Healgen SARS-CoV-2 neutralising Antibody Rapid Test Cassette) was compared to the Roche Elecsys/-S anti-SARS-CoV-2 antibody assays and an in vitro surrogate neutralisation assay. A correlation between anti-spike (S), anti-nucleocapsid (N) titres, and in vitro neutralisation was also assessed.

Results

1,777 serology samples were tested using Roche Elecsys/-S anti-SARS-CoV-2 assays to detect total anti-N/S antibodies. 1,562 samples were tested using the POC LFA (including 50 negative controls), and 90 samples were tested using an in vitro ACE2-RBD binding inhibition surrogate neutralisation assay. The POCT demonstrated 97.7% sensitivity, 100% specificity, a positive predictive value (PPV) of 100%, and a negative predictive value (NPV) of 61% in comparison to the commercial assay. Anti-S antibody titres determined by the Roche assay stratified by the POC LFA result groups demonstrated statistically significant differences between the "Positive" and "Negative" LFA groups (p < 0.0001) and the "Weak Positive" and "Positive" LFA groups (p < 0.0001). No statistically significant difference in ACE2-RBD binding inhibition was demonstrated when stratified by the LFA POC results. A positive, statistically significant correlation was demonstrated between the in vitro pseudo-neutralisation assay results and anti-S antibody titres (rho 0.423, p < 0.001) and anti-N antibody titres (rho = 0.55, p < 0.0001).

Conclusion

High sensitivity, specificity, and PPV were demonstrated for the POC LFA for the detection of anti-S-RBD antibodies in comparison to the commercial assay. The LFA was not a reliable determinant of the neutralisation capacity of identified antibodies. POC LFA are useful tools in sero-epidemiology settings, pandemic preparedness and may act as supportive tools in treatment decisions through the rapid identification of anti-Spike antibodies.

Rapid and simultaneous detection of multiple pathogens in the lower reproductive tract during pregnancy based on loop-mediated isothermal amplification-microfluidic chip

Background

Female reproductive tract infection (RTI) is the common source of varied diseases, especially as an important risk factor for pregnancy outcomes, therefore the rapid, accurate and simultaneous detection of multiple pathogens is in urgent need for assisting the diagnosis and treatment of RTI in pregnant women. Streptococcus agalactiae (S. agalactiae), Enterococcus faecalis (E. faecalis), Gardnerella vaginalis (G. vaginalis), Candida albicans (C. albicans) and Chlamydia trachomatis (C. trachomatis) are five main pathogens in lower genital tract with high risk, serious consequences and clinical demands. The combination of loop-mediated isothermal amplification (LAMP) and microfluidic technology was used to develop the LAMP-microfluidic chip for rapid, simple, sensitive and simultaneous detection of the five target pathogens above.

Results

Standard strains and clinical isolates were used for the establishment of the novel LAMP method in tube and LAMP-microfluidic chip, followed by the chip detection on 103 clinical samples and PCR verification partially. The sensitivities of LAMP of S. agalactiae, E. faecalis, G. vaginalis, and C. albicans in tube were 22.0, 76.0, 13.2, 1.11 CFU/μL, respectively, and C. trachomatis was 41.3 copies/μL; on LAMP-microfluidic chip they were 260, 154, 3.9 and 7.53 CFU/μL, respectively, and C. trachomatis was 120 copies/μL. The positive coincidence rates of clinical stains in tube and on chip experiments were 100%. Compared with the classic culture method performed in hospitals, the positive coincidence rate of the 103 clinical samples detected by LAMP-microfluidic chip were 100%. For the six inconsistent ones, including four G. vaginalis and two C. albicans positive samples tested by LAMP-microfluidic chip and verified by PCR were negative by culturing method in hospitals, indicating the lack of efficient detection by the classic culturing method.

Conclusion

Our study suggested that the LAMP-microfluidic chips could simultaneously, efficiently, and accurately detect multiple main pathogens, including S. agalactiae, E. faecalis, G. vaginalis, C. albicans and C. trachomatis, in clinical samples of female RTI to give a great clinical value. Accordingly, this novel method has the potential to provide a valuable reference for female RTI screening and early diagnosis during pregnancy.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-022-02657-0.

Nanoparticle-Based Lateral Flow Biosensor Integrated With Loop-Mediated Isothermal Amplification for Rapid and Visual Identification of Chlamydia trachomatis for Point-of-Care Use

Chlamydial infection, caused by Chlamydia trachomatis, is the most common bacterial sexually transmitted infection and remains a major public health problem worldwide, particularly in underdeveloped regions. Developing a rapid and sensitive point-of-care (POC) testing for accurate screening of C. trachomatis infection is critical for earlier treatment to prevent transmission. In this study, a novel diagnostic assay, loop-mediated isothermal amplification integrated with gold nanoparticle-based lateral flow biosensor (LAMP-LFB), was devised and applied for diagnosis of C. trachomatis in clinical samples. A set of LAMP primers based on the ompA gene from 14 C. trachomatis serological variants (serovar A-K, L1, L2, L3) was successfully designed and used for the development of C. trachomatis-LAMP-LFB assay. The optimal reaction system can be performed at a constant temperature of 67°C for 35 min. The total assay process, including genomic DNA extraction (~15 min), LAMP reaction (35 min), and LFB readout (~2 min), could be finished within 60 min. The C. trachomatis-LAMP-LFB could detect down to 50 copies/ml, and the specificity was 100%, no cross-reactions with other pathogens were observed. Hence, our C. trachomatis-LAMP-LFB was a rapid, reliable, sensitive, cost-effective, and easy-to-operate assay, which could offer an attractive POC testing tool for chlamydial infection screening, especially in resource starvation settings.

Development of a duplex recombinase-aided amplification assay for direct detection of Mycoplasma pneumoniae and Chlamydia trachomatis in clinical samples

BACKGROUND

Pneumonia caused by Mycoplasma pneumoniae is common in the elderly and children, and pneumonia caused by Chlamydia trachomatis is prevalent in newborns. This study aimed to establish a rapid, sensitive, and simple method for the direct detection of M. pneumoniae and C. trachomatis in clinical samples without DNA extraction.

METHODS

We established a duplex recombinase-aided amplification (RAA) assay with the RNAseP gene as an internal control for detecting the P1 gene of M. pneumoniae and the ORF8 gene of C. trachomatis, respectively. The results were obtained at 39 °C within 15-20 min. A total of 130 clinical samples suspected of M. pneumoniae or C. trachomatis infection were collected and tested by duplex RAA and PCR. DNA extracted via a commercial kit or treated with a nucleic acid-releasing agent was used and compared, respectively. Standard recombinant plasmids were used to test the sensitivity of the duplex RAA assay. In addition, other similar common pathogens were used to verify the specificity of the duplex RAA assay.

RESULTS

The sensitivity of the duplex RAA assay for detecting M. pneumoniae and C. trachomatis was 10 copies/μL using recombinant plasmids. Compared with PCR, the sensitivity and specificity of duplex RAA assays for M. pneumoniae and C. trachomatis was 100% using clinical DNA samples extracted using a commercial kit and a nucleic acid-releasing agent, and the Kappa value was 1.

CONCLUSION

The advantages of this duplex RAA assay include high sensitivity and specificity, short duration, and simple extraction steps, with potential for use in the on-site detection of M. pneumoniae and C. trachomatis in resource-limited settings.

Prevalence of Mycoplasma genitalium and other sexually transmitted pathogens in male urethritis in a sexual health centre in New Caledonia

BACKGROUND

The prevalence of sexually transmitted infections (STIs) is high in New Caledonia (NC), but there are no data on Mycoplasma genitalium (MG). However, the syndromic treatment of urethritis used in the territory includes a single dose of azithromycin, which could generate resistance in MG.

METHODS

We recruited 217 men referred to the Noumea public medical centre (CMP) with signs of urethritis and meeting the inclusion criteria from May 2016 to March 2018. Each was tested for Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT), Trichomonas vaginalis (TV) and for the first time in NC for MG by polymerase chain reaction (PCR).

RESULTS

The prevalence of MG was 10.1% (22/217). Azithromycin resistance of MG (mutation in the 23S rRNA gene) could only be assessed for 10 of the 22 strains. Only one (1/10; 10%) was resistant. The prevalence of other STIs tested was high, as CT, NG and/or TV were associated in 77.3% (17/22) of MG-positive cases.

CONCLUSIONS

Although co-infections further justify syndromic management, the presence of MG in NC urethritis cases could call treatment guidelines into question.