Molecular genetic methods for diagnosis and characterisation of Chlamydia trachomatis and Neisseria gonorrhoeae: impact on epidemiological surveillance and interventions

Abstract

One of the mainstays in the prevention of Chlamydia trachomatis and Neisseria gonorrhoeae infections is the availability of laboratory diagnostics with high sensitivity and specificity. Assays for diagnosis of C. trachomatis include cell culture and nucleic acid amplification tests (NAATs). The major target sequences for C. trachomatis diagnosis by NAATs are located at the cryptic plasmid and the major target used for characterisation is the omp1 gene. The gold standard for diagnosis of N. gonorrhoeae is culture. However, numerous NAATs for identification of N. gonorrhoeae and a number of molecular genetic methods for characterisation of N. gonorrhoeae have been developed. Probably no routine laboratory can attain as high sensitivity by culturing C. trachomatis or N. gonorrhoeae as by using NAATs. For that reason NAATs can be recommended for diagnosing C. trachomatis, but not as the only diagnostic assay for N. gonorrhoeae, due to lack of antibiotic susceptibility testing and specificity problems, most pronounced for pharyngeal and rectal samples. Genotyping of C. trachomatis or N. gonorrhoeae provides additional information for contact tracing. It is recommended for N. gonorrhoeae, at least in low prevalence geographic areas, but cannot today be recommended for C. trachomatis. This is due to the low genetic variability and hence the limited benefits for partner notification. However, genotyping of C. trachomatis may play an important role under special circumstances.

Frecuencia de la infección por Chlamydia trachomatis en un grupo de mujeres de la Región de la Araucanía, Chile

“…La detección de C. trachomatis se realizó por RPC convencional y para la confirmación de casos positivos se utilizó RPC anidada. En total, la frecuencia obtenida fue de 4,7% (n: 19). No hubo diferencias significativas entre los grupos etarios y la prevalencia.…”

“…Si bien, la sensibilidad de la técnica de RPC depende de la calidad de la muestra, del sistema de detección del producto o de la eficiencia propia de RPC, en este trabajo fue posible aumentar la sensibilidad utilizando partidores dirigidos al plásmido críptico bacteriano, debido a que una bacteria puede contener alrededor de 10 copias de plásmido críptico 19 . Así, se puede cuantificar un mínimo de 3,55 copias/μL, lo que significaría la presencia de una bacteria.…”

Genital Chlamydia trachomatis infections

“…Questi metodi amplificano sia un gene cromosomico, il gene omp 1 codificante per il MOMP, sia l'RNAr presente in circa 1000 copie per microrganismo, sia una sequenza del plasmide criptico specifico di C.t. presente nel 99% dei ceppi in 10 copie per batterio (40). I test che amplificano l'RNAr hanno una sensibilità ancora maggiore rispetto a quelli che amplificano il DNA anche se l'RNA è più fragile.…”

“…Aliquote di ciascun campione possono essere combinate in un pool e testate. Se il pool risulta negativo, tutti i campioni formanti il pool saranno negativi, se il pool è positivo verranno testati singolarmente i campioni che lo compongono (18,23,40). Un limite dei NAATs è rappresentato dal fatto che nel campione possono essere presenti inibitori della reazione di amplificazione responsabili di risultati falsamente negativi.…”

New approaches to identification of bacterial pathogens by surface enhanced laser desorption/ionization time of flight mass spectrometry in concert with artificial neural networks, with special reference to Neisseria gonorrhoeae

“…Conventional diagnostic methods for N. gonorrhoeae include direct microscopy, selective culturing, immunological tests, enzyme reaction tests and nucleic acid amplification tests, among others (Johnson et al, 2002;Knapp, 1988). The population structure of N. gonorrhoeae is of an unstructured random mating or panmictic nature (Smith et al, 1993) causing frequent horizontal genetic exchange, which in addition to natural mutation causes the high levels of variability that enable bacterial adaptation and immune system evasion (Fredlund et al, 2004).…”