Analytical specificity and sensitivity of the novel dual-target GeneProof Neisseria gonorrhoeae PCR kit for detection of N. gonorrhoeae

Analytical and clinical validation of a multiplex PCR assay for detection of Neisseria gonorrhoeae and Chlamydia trachomatis including simultaneous LGV serotyping on an automated high-throughput PCR system

For effective infection control measures for Chlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG), a reliable tool for screening and diagnosis is essential. Here, we aimed to establish and validate a multiplex PCR assay on an automated system using a dual-target approach for the detection of CT/NG and differentiation between lymphogranuloma venereum (LGV) and non-LGV from genital and extra-genital specimens. Published primer/probe sets (CT: pmpH, cryptic plasmid; NG: porA, opa) were modified for the cobas 5800/6800/8800. Standards quantified by digital PCR were used to determine linearity and lower limit of detection (LLoD; eSwab, urine). For clinical validation, prospective samples (n = 319) were compared with a CE-marked in vitro diagnostics (CE-IVD) assay. LLoDs ranged from 21.8 to 244 digital copies (dcp)/mL and 10.8 to 277 dcp/mL in swab and urine, respectively. A simple linear regression analysis yielded slopes ranging from -4.338 to -2.834 and Pearson correlation coefficients from 0.956 to 0.994. Inter- and intra-run variability was <0.5 and <1 cycle threshold (ct), respectively. No cross-reactivity was observed (n = 42). Clinical validation showed a sensitivity of 94.74% (95% confidence interval (CI): 87.23%-97.93%) and 95.51% (95% CI: 89.01%-98.24%), a specificity of 99.59% (95% CI: 97.71%-99.98%) and 99.57% (95% CI: 97.58%-99.98%), positive predictive values of 89.91% (estimated prevalence: 3.7%; 95% CI: 80.91%-95.6%) and 88.61% (estimated prevalence: 3.4%; 95% CI: 80.18%-94.34%), and negative predictive values of 99.81% (95% CI: 98.14%-100%) and 99.85% (95% CI: 98.14%-100%) for the detection of CT and NG, respectively. In conclusion, we established a dual-target, internally controlled PCR on an automated system for the detectiwon of CT/NG from genital and extra-genital specimens. Depending on local regulations, the assay can be used as a screening or a confirmatory/typing assay.IMPORTANCEChlamydia trachomatis (CT) and Neisseria gonorrhoeae (NG) represent a major global health burden, with the World Health Organization estimating that >128 million and >82 million people, respectively, were newly infected in 2020. For effective infection control measures, a reliable tool for sensitive diagnosis and screening of CT/NG is essential. We established a multiplex PCR assay for the detection of CT/NG and simultaneous discrimination between lymphogranuloma venereum (LGV) and non-LGV strains, which has been validated for genital and extra-genital specimens on a fully automated system. To increase assay sensitivity, a dual-target approach has been chosen for both pathogens. This strategy reduces false-positive results in oropharyngeal swabs due to the detection of commensal N. species that may harbor NG DNA fragments targeted in the PCR due to horizontal gene transmission following previous infection. In sum, the established assay provides a powerful tool for use as either a screening/diagnostic or a typing/confirmatory assay.

Conductive Ink-Coated Paper-Based Supersandwich DNA Biosensor for Ultrasensitive Detection of Neisseria gonorrhoeae

Herein, we report results of the studies relating to the development of an impedimetric, magnetic bead-assisted supersandwich DNA hybridization assay for ultrasensitive detection of Neisseria gonorrhoeae, the causative agent of a sexually transmitted infection (STI), gonorrhea. First, a conductive ink was formulated by homogenously dispersing carboxylated multiwalled carbon nanotubes (cMWCNTs) in a stable emulsion of terpineol and an aqueous suspension of carboxymethyl cellulose (CMC). The ink, labeled C5, was coated onto paper substrates to fabricate C5@paper conductive electrodes. Thereafter, a magnetic bead (MB)-assisted supersandwich DNA hybridization assay was optimized against the porA pseudogene of N. gonorrhoeae. For this purpose, a pair of specific 5' aminated capture probes (SCP) and supersandwich detector probes (SDP) was designed, which allowed the enrichment of target gonorrheal DNA sequence from a milieu of substances. The SD probe was designed such that instead of 1:1 binding, it allowed the binding of more than one T strand, leading to a 'ladder-like' DNA supersandwich structure. The MB-assisted supersandwich assay was integrated into the C5@paper electrodes for electrochemical analysis. The C5@paper electrodes were found to be highly conductive by a four-probe conductivity method (maximum conductivity of 10.1 S·cm^-1). Further, the biosensing assay displayed a wide linear range of 100 aM-100 nM (10⁹ orders of magnitude) with an excellent sensitivity of 22.6 kΩ·(log[concentration])^-1. The clinical applicability of the biosensing assay was assessed by detecting genomic DNA extracted from N. gonorrhoeae in the presence of DNA from different non-gonorrheal bacterial species. In conclusion, this study demonstrates a highly sensitive, cost-effective, and label-free paper-based device for STI diagnostics. The ink formulation prepared for the study was found to be highly thixotropic, which indicates that the paper electrodes can be screen-printed in a reproducible and scalable manner.

Gentamicin 240 mg plus azithromycin 2 g vs. ceftriaxone 500 mg plus azithromycin 2 g for treatment of rectal and pharyngeal gonorrhoea: a randomized controlled trial

OBJECTIVES

The aim was to evaluate the efficacy and tolerability of gentamicin 240 mg plus azithromycin 2 g for treatment of uncomplicated rectal and pharyngeal gonorrhoea compared to ceftriaxone 500 mg plus azithromycin 2 g, the recommended European first-line gonorrhoea treatment.

METHODS

A non-inferiority, open-label, single-centre randomized controlled trial was conducted in Prague, Czech Republic. Patients, 18-75 years of age, diagnosed with uncomplicated rectal or pharyngeal gonorrhoea by nucleic acid amplification test (NAAT) were randomized to treatment with gentamicin 240 mg intramuscularly plus azithromycin 2 g orally or ceftriaxone 500 g intramuscularly plus azithromycin 2 g orally. The primary outcome was negative culture and negative NAAT, i.e. 1 week and 3 weeks, respectively, after treatment.

RESULTS

Both clinical cure and microbiological clearance was achieved by 100% (95% CI 0.95-1.00) of patients in the gentamicin/azithromycin arm (n = 72; 40 rectal, 17 pharyngeal and 15 rectal+pharyngeal infections both localizations) and 100% (95% CI 0.95-1.00) in ceftriaxone/azithromycin arm (n = 71; 38 rectal, 14 pharyngeal and 19 rectal+pharyngeal infections). The absolute difference between the two arms was 0.0% (CI95% -5.1 to 5.1), thus less than the pre-specified margin of 7%. Administration of gentamicin was not more painful than ceftriaxone according to the visual analogue scale (1.8 vs. 3.4; p <0.001). Gastrointestinal adverse events were similar in the ceftriaxone arm (33/71, 46.5%) and the gentamicin arm (29/72, 40.3%), and overall in most (52/62, 83.9%) cases they were mild.

CONCLUSIONS

Gentamicin 240 mg plus azithromycin 2 g is an effective alternative for treatment of extragenital gonorrhoea.