Successful Combination of Nucleic Acid Amplification Test Diagnostics and Targeted Deferred Neisseria gonorrhoeae Culture

Abstract

g Nucleic acid amplification tests (NAATs) are recommended for the diagnosis of N. gonorrhoeae infections because of their superior sensitivity. Increasing NAAT use causes a decline in crucial antimicrobial resistance (AMR) surveillance data, which rely on culture. We analyzed the suitability of the ESwab system for NAAT diagnostics and deferred targeted N. gonorrhoeae culture to allow selective and efficient culture based on NAAT results. We included patients visiting the STI Clinic Amsterdam, The Netherlands, in 2013. Patient characteristics and urogenital and rectal samples for direct N. gonorrhoeae culture, standard NAAT, and ESwab were collected. Standard NAAT and NAAT on ESwab samples were performed using the Aptima Combo 2 assay for N. gonorrhoeae and C. trachomatis. Two deferred N. gonorrhoeae cultures were performed on NAAT-positive ESwab samples after storage at 4°C for 1 to 3 days. We included 2,452 samples from 1,893 patients. In the standard NAAT, 107 samples were N. gonorrhoeae positive and 284 were C. trachomatis positive. The sensitivities of NAAT on ESwab samples were 83% (95% confidence interval [CI], 75 to 90%) and 87% (95% CI, 82 to 90%), respectively. ESwab samples were available for 98 of the gonorrhea-positive samples. Of these, 82% were positive in direct culture and 69% and 56% were positive in the 1st and 2nd deferred cultures, respectively (median storage times, 27 and 48 h, respectively). Deferred culture was more often successful in urogenital samples or when the patient had symptoms at the sampling site. Deferred N. gonorrhoeae culture of stored ESwab samples is feasible and enables AMR surveillance. To limit the loss in NAAT sensitivity, we recommend obtaining separate samples for NAAT and deferred culture.A ntibiotic treatment for gonorrhea has existed for around 80 years, and Neisseria gonorrhoeae has developed mechanisms of antimicrobial resistance (AMR) ever since. Resistance to the last-resort empirical monotherapy, extended-spectrum cephalosporins, has now emerged, and this has been recognized as a major public health problem (1). In response, the World Health Organization recommended actions to extend the existing surveillance and, where lacking, develop new AMR surveillance worldwide (2, 3).In recent years, nucleic acid amplification tests (NAATs) have rapidly replaced the use of culture as a diagnostic test for gonorrhea (4). While the use of highly sensitive NAATs results in the detection of more infections, it also results in fewer cultures (5). This compromises AMR surveillance, as molecular methods to detect AMR in NAAT samples are still suboptimal, and culture remains essential (6, 7).Ideally, an NAAT to diagnose gonorrhea would be combined with targeted deferred culture of positive samples for AMR surveillance. Using a single sample for NAAT and deferred culture requires special conditions for the collection medium, i.e., maintained diagnostic NAAT sensitivity and N. gonorrhoeae survival until the NAAT result is available. The ESwab system (Copan Italia, Brescia, Ita...

Bacterial sexually transmitted infections

“…Urine is not suitable for bacterial cultures in either gender. For bacterial cultures to be diagnostically useful, the time between swabbing and arrival of the specimen in the laboratory (in a suitable transport medium) should ideally be no longer than 4 hours .…”

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

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Bakterielle sexuell übertragbare Infektionen

“…Urin ist für die kulturelle Diagnostik bei beiden Geschlechtern ungeeignet. Entscheidend für das Gelingen einer Kultur ist die Zeitspanne zwischen Entnahme des Abstrichs und Eintreffen der Probe – in einem geeigneten Transportmedium – im Labor (idealerweise innerhalb von 4 Stunden) .…”