Comparison of microscopy, culture and in-house PCR and NASBA assays for diagnosis of Neisseria gonorrhoeae in Russia

Comparative performance of commercial Amies transport media with and without charcoal for Neisseria gonorrhoeae culture for gonococcal isolation and antimicrobial resistance monitoring in Ukraine

INTRODUCTION

Culture is the only laboratory method that provides live gonococcal isolates for monitoring antimicrobial resistance. Many clinical settings do not have direct access to laboratories for the immediate processing of biological samples. Validated and quality-assured transport media are recommended to maintain the viability of Neisseria gonorrhoeae.

METHODS

In total, 103 clinical samples were divided into two groups: 51 samples were stored in Amies agar gel medium containing charcoal and 52 samples were stored in agar gel medium without charcoal. All samples were stored at 4°C for 0.5-6 h and then transported in a thermo-protected box within 0.17-0.25 h to the laboratory of Ternopil Regional STI Clinic (Ukraine).

RESULTS

The recovery rate was significantly higher for charcoal-containing Amies medium than for charcoal-free Amies medium (86.27%, 44/51 vs. 59.62%, 31/52). A higher rate of specimens transported in charcoal-containing Amies medium was isolated within 24 h (84.31%, 43/51), whereas most isolates from charcoal-free Amies medium grew within 24 h (42.31%, 22/52) or 48 h (17.31%, 9/52). Growth beyond the first quadrant of the agar plate was registered for 59.09% (26/44) of charcoal-containing Amies samples, compared with only 19.35% (6/31) of charcoal-free Amies samples.

CONCLUSIONS

A high rate of N. gonorrhoeae recovery after transport has considerable public health implications for establishing national antimicrobial susceptibility programs. Charcoal-containing Amies medium had higher viability rate, and it could be used for diagnostic and isolation purposes in future antimicrobial susceptibility studies. Continuous validation studies of transport medium for N. gonorrhoeae culture are needed.

A systematic review and meta-analysis of different diagnostic procedures to detect gonococcus infection in resource-limited scenario

Context

Neisseria gonorrhoeae is a Gram-negative diplococcus, an obligate human pathogen, and the etiologic agent of the sexually transmitted infection (STI), gonorrhoea. culture is the standard procedure for diagnosis, which may be supported by nucleic acid tests and microscopy.

Aims

To determine the best possible method of diagnosis for Gonococcus infection in resource-limited settings.

Settings and Design

The meta-analyses were designed to determine the difference in diagnosis between Culture and nucleic acid amplification tests (NAATs) and also between the different Amplification Tests and widely available Roche COBAS AMPLICOR test.

Subjects and Methods

Databases searched were Pubmed, Medline, Google Scholar and Cochrane reviews. Risk ratio (RR) with 95% confidence intervals was estimated for the dichotomous outcomes. The random-effect model was applied for all the studies in the analysis.

Statistical Analysis Used

The meta-analysis was computed in RevMan Version 5.3, Copenhagen, Denmark.

Results

In the first analysis, NAATs significantly improved the chances of detection in comparison to the standard culture and final RR was 1.24 (1.05-2.51), which put the diamond on the right of no-effect axis, indicating more positives by NAATs. In the second analysis, AMPLICOR had the more positive results, which may have indicated better detection rate, as well as less specificity and final RR was 0.809 (0.737-0.888), which put the diamond on the left of the non-effect axis, indicating more positives by AMPLICOR.

Conclusions

In a resource-limited scenario like India, the syndromic management of STIs are considered to be the norm. A positive diagnosis is only given if the tests are confirmed by Culture, as it is still considered to be the gold standard of diagnosis. However, in many cases, due to suboptimal transportation and lack of proper handling, culture in unable to grow even if the patient is infected. In such cases, Nucleic Acid Tests should be able to detect an infection.

Comparison of rRNA-based and DNA-based nucleic acid amplifications for detection of Chlamydia trachomatis, Neisseria gonorrhoeae, and Ureaplasma urealyticum in urogenital swabs

Background

Nucleic acid amplification tests (NAAT) are well-accepted in diagnosis and surveillance of sexually infectious pathogens worldwide. However, performance differences between a RNA-based NAAT and DNA-based NAAT are rarely reported. This study compares the performances of the RNA-based SAT (simultaneous amplification and testing) assay and the DNA-based quantitative real-time polymerase chain reaction (qPCR) assay.

Methods

A total of 123 urogenital swabs were collected from outpatients with suspected genital infections in our hospital. Chlamydia trachomatis (CT), Neisseria gonorrhoeae (NG), and Ureaplasma urealyticum (UU) in these swabs were simultaneously tested by SAT and qPCR. Any swabs were positive in the qPCR assay were further verified by following cloning and sequencing. All statistical analysis was performed using the SPSS software.

Results

When the concentrations of CT, NG, or UU were more than 1 × 10³ copies/ml, 100% agreements between SAT and qPCR were observed regardless of the pathogen. No discrepancy was found. However, the sensitivity of SAT is significantly higher than qPCR in samples with concentration less than 1 × 10³ copies/ml. When tested by SAT and qPCR, 57.14 and 28.57% were positive for CT, 46.15% and 0 were positive for NG, 80% and 0 were positive for UU, respectively.

Conclusions

The SAT assay has better agreements and higher sensitivities when compared with the qPCR assay, and thus could be a better choice for screening, diagnosis, and surveillance of sexually transmitted diseases, especially for CT and NG.

Value of light microscopy to diagnose urogenital gonorrhoea: a diagnostic test study in Indonesian clinic-based and outreach sexually transmitted infections services

INTRODUCTION

Gonorrhoea is a common sexually transmitted disease caused by Neisseria gonorrhoeae (Ng) infection. Light microscopy of urogenital smears is used as a simple tool to diagnose urogenital gonorrhoea in many resource-limited settings. We aimed to evaluate the accuracy of light microscopy to diagnose urogenital gonorrhoea as compared with a PCR-based test.

METHODS

In 2014, we examined 632 male urethral and 360 endocervical smears in clinic-based and outreach settings in Jakarta, Yogyakarta and Denpasar, Indonesia. Using the detection of Ng DNA by a validated PCR as reference test, we evaluated the accuracy of two light microscopic criteria to diagnose urogenital gonorrhoea in genital smears: (1) the presence of intracellular Gram-negative diplococci (IGND) and (2) ≥5 polymorphonuclear leucocytes (PMNL)/oil-immersion field (oif) in urethral or ≥20 PMNL/oif in endocervical smears.

RESULTS

In male urethral smears, IGND testing had a sensitivity (95% CI), specificity (95% CI) and kappa±SE of 59.0% (50.1 to 67.4), 89.4% (86.3 to 91.9) and 0.49±0.04, respectively. For PMNL count, these were 59.0% (50.1 to 67.4), 83.7% (80.2 to 86.9) and 0.40±0.04, respectively. The accuracy of IGND in the clinic-based settings (72.0% (57.5 to 83.3), 95.2% (91.8 to 97.5) and 0.68±0.06, respectively) was better than in the outreach settings (51.2% (40.0 to 62.3), 83.4% (78.2 to 87.8) and 0.35±0.06, respectively). In endocervical smears, light microscopy performed poorly regardless of the setting or symptomatology, with kappas ranging from -0.09 to 0.24.

CONCLUSION

Light microscopy using IGND and PMNL criteria can be an option with moderate accuracy to diagnose urethral gonorrhoea among males in a clinic-based setting. The poor accuracy in detecting endocervical infections indicates an urgent need to implement advanced methods, such as PCR. Further investigations are needed to identify the poor diagnostic outcome in outreach services.