Evaluation of eight methods for identification of pathogenic Neisseria species: Neisseria-Kwik, RIM-N, Gonobio-Test, Minitek, Gonochek II, GonoGen, Phadebact Monoclonal GC OMNI Test, and Syva MicroTrak Test

Abstract

The performance of eight methods in identifying Neisseria species, particularly N. gonorrhoeae, was evaluated. These methods included four rapid carbohydrate utilization tests (Gonobio-Test, Neisseria-Kwik, RIM-N, and Minitek); the Gonochek 11, a test which is based on the utilization of chromogenic substrates; and three monoclonal antibody tests (Syva MicroTrak, GonoGen, and Phadebact Monoclonal GC OMNI Test). In all, 182 isolates comprised in six species of Neisseria as well as Branhamella catarrhalis and Moraxella sp. were tested. Cystine-tryptic digest agar supplemented with sugars was included for reference purposes. In the carbohydrate utilization tests, the sensitivity and specificity of the Neisseria-Kwik and Minitek tests for the identification of N. gonorrhoeae were 100%. This compared with sensitivities and specificities, respectively, of 100 and 99.1% for the Gonobio-Test and 99.1 and 100% for cystine-tryptic digest agar sugars and the RIM-N test. The sensitivity and specificity of the Gonochek II test were 99.0 and 86.7%, respectively. Although most test kits did not claim to identify all Neisseria species, in several cases isolates of N. subflava were misidentified or could be misinterpreted as N. gonorrhoeae or N. meningitidis. With the monoclonal reagents, the Syva MicroTrak system was 100% sensitive and 100% specific. The GonoGen test was both 99.1% sensitive and specific, while the Phadebact Monoclonal GC OMNI Test was 99.1% sensitive but 91.2% specific. With this latter test, cross-reactions were observed with strains of B. catarrhalis, N. cinerea, and N. lactamica.

Branhamella catarrhalis: an organism gaining respect as a pathogen.

“…The potentially confusing coccobacillary cells of Moraxella and Acinetobacter species elongate into snakelike cells when division is blocked by sublethal concentrations of penicillins or certain other antibacterial agents. Since elongation does not occur with B. catarrhalis or Neisseria species, this is an easy way to distinguish them from nonsaccharolytic, short paired rods (63 155,185), Gonobio-Test (94), and API QuadFERM+ (109,156). Minitek test reactions were correct in some instances (94), but not all (233).…”

Moraxella (Branhamella) catarrhalis: Clinical, microbiological and immunological features in lower respiratory tract infections

“…Strains of M catarrhah have been found susceptible to colistin, with inhibition zones of 3 10 mm in diameter when using disks containing lOpg of colistin (Knapp et al 1984, Morello et al 1985, but resistant strains occur, which diminishes the reliability of this characteristic (I, Blackwell et al 1978, Dillon et al 1988, Doern and Morse 1980, Durussel and Siegrist 1988, Knapp 1988, Young and Bain 1983.…”

“…Being non-motile, oxidase-and catalase-positive and asaccharolytic are typical characteristics of human isolates of Moraxella species, including M catarrhalis (Weyant et al 1996). Negative results for acid production from carbohydrates are observed uniformly with various methods, including rapid carbohydrate tests (1, IY Arkwright 1907, Catlin 1970, Catlin and Cunningham 1964a, Dillon et al 1988, Durussel and Siegrist 1988, Elser and Huntoon 1909, Janda et al 1987, Knapp and Holmes 1983, Lairscey and Kelly 1985. The apathogenic Neisseria species, NJluvescens, N mucosa and N pharyngis, possess an amylosucrase that builds sucrose into a polysaccharide, which reacts with iodine (Berger 1961a).…”

Rapid identification of pathogenic neisserias using the Identicult-Neisseria test

“…T h e Gonocheck identification system uses similar chromogenic substrates, albeit in a different format from the Identicult-Neisseria. Several comparative studies have been made of the Gonocheck system and the specificity has ranged from 86.7 to 100% (Wellborn et al 1984;Philip and Garton 1985;Wood and Young 1986;Dillon et a!. 1988).…”

“…grown on selective medium. If non-selective medium is used, non-pathogenic neisseria such as N. subJava may grow leading to misidentifications (Dillon et al 1988;Janda and Sobieski 1988). Depending on the sample site and sexual orientation of the patient isolation of non-gonococcal neisseria may vary from 0.4 to 11.4% (Young and Reid 1987).…”