Concordance between Neisseria gonorrhoeae Genotypes Recovered from Known Sexual Contacts

Abstract

Neisseria gonorrhoeae multiantigen sequence typing (NG-MAST) is a highly discriminatory molecular typing procedure that provides precise and unambiguous strain characterization. Since molecular typing can complement contact tracing for reconstructing gonorrhea sexual networks, the concordance between the NG-MAST genotypes of pairs of N. gonorrhoeae isolates from recent sexual contacts was examined. Among 72 pairs of gonococci from recent sexual contacts, the genotypes of each pair were concordant in 65 cases (90.3%). In two further pairs, the isolates from sexual contacts differed by only a single nonsynonymous substitution in the porin gene, and in both of these pairs, the isolates were the same by opa typing. The other five nonconcordant pairs of isolates were clearly different strains. opa typing data were available for 51 of the pairs of isolates from sexual contacts, and concordant opa types were obtained in 38 cases (74.5%). NG-MAST should therefore be better than opa typing at identifying recent sexual contacts and has the important advantage over opa typing of being a more precise method of strain characterization.Typing of Neisseria gonorrhoeae isolates has provided a valuable adjunct to contact tracing for reconstructing sexual networks (3, 14) and for identifying individuals predicted to be in the same sexual network (2, 6). Phenotypic typing methods for gonococci-for example, the combination of auxotype and serovar-lack sufficient discrimination for this purpose, but a number of more-discriminatory molecular methods have been developed. Of these, pulsed-field gel electrophoresis and opa typing are considered to be the most highly discriminatory but have the disadvantage that they require the comparison of complex DNA fragment patterns on agarose or acrylamide gels (10, 12). More recently there has been a move toward the use of digital data for molecular typing, since this is more suitable for the development of molecular-typing Internet databases and the unambiguous comparison of new isolates with those already deposited in the database. In gonococci, the sequences of the porin (por) gene and fragments of both por and the transferrin-binding protein subunit B gene (tbpB) have been evaluated for molecular typing (9, 11, 13). These genes show high levels of sequence diversity among strains; they are believed to evolve rapidly, because their gene products are surface exposed and are targets of the host immune response to infection. The combination of the sequences at por and tbpB have been used to develop N. gonorrhoeae multiantigen sequence typing (NG-MAST). In this procedure each unique sequence at each locus is given a different allele number, so that a strain is defined unambiguously by two digits, corresponding to the allele numbers at por and tbpB. Each different two-digit number is assigned to a distinct sequence type (ST) that is used to describe the strain (9).Rapid diversification of the loci used to characterize gonococci provides very high levels of discrimination between strains, but too hi...

Review and International Recommendation of Methods for Typing Neisseria gonorrhoeae Isolates and Their Implications for Improved Knowledge of Gonococcal Epidemiology, Treatment, and Biology

“…However, Opa typing has the same disadvantages as RFLP methods, including labor-intensiveness, subjectiveness, and a need for pronounced standardization for interlaboratory comparisons. Opa typing has been used to define gonococcal populations within a geographic area, for the identification of clusters of strains (8,9,19,20,26,49,65,71,74,93,96,104,118,121,127,174,182,186,189), for tracing strain transmission between sexual contacts (9,19,74,186), for resolving suspicions of reinfection (102), for substantiation of treatment failure (77,102), and for detection of mixed infection (102). Opa typing has been used to increase the discriminatory power of other typing methods, including full-or extended-length porB sequencing or NG-MAST in specific situations, especially those involving extreme microepidemiological analysis (19,65,96,104,174,186) (Table 1).…”

First Neisseria gonorrhoeae Genotyping Analysis in France: Identification of a Strain Cluster with Reduced Susceptibility to Ceftriaxone

“…Over the last few years, the number of gonorrhoea cases has increased regularly in many European countries (1)(2)(3)6), the United States (15), and China (7). The French National Reference Centre (NRC) for Neisseria gonorrhoeae receives isolates of gonorrhoea diagnosed in France, through a voluntary national network, RENAGO (Réseau National du Gonocoque), including 235 laboratories located across the entire national territory.…”

Molecular Surveillance of Clinical Neisseria gonorrhoeae Isolates in Russia

“…It is based on the analysis of internal fragments of two hypervariable genes, porB and tbpB, encoding superficial gonococcus antigens and therefore under positive selection (19). An online database (www.ng-mast.net) collects current information on the sequence types of gonococcus isolates in different regions of the world, and it can be an efficient instrument for objective estimation of the genetic variability of the microbial population and tracing the spread of infection (2). Moreover, an association of the NG-MAST sequence type with the antibiotic resistance profile has been demonstrated by some investigators (20,26).…”