Clinical evaluation of the rapid carbohydrate degradation microtube method for identification of Neisseria species

Difficulties in differentiating Neisseria cinerea from Neisseria gonorrhoeae in rapid systems used for identifying pathogenic Neisseria species

Neisseria cinerea and Neisseria gonorrhoeae may occur at the same body sites and may have similar colony morphologies. Ideally, systems used for rapid identification of N. gonorrhoeae should be able to differentiate N. cinerea from gonococci. We tested seven N. cinerea strains using the Gonochek II (Du Pont Diagnostics), Minitek (BBL Microbiology Systems), RapID-NH (Innovative Diagnostics, Inc.), RIM-N (American Microscan), and Phadebact (Pharmacia Diagnostics) systems. We found that the reactions produced by N. cinerea in Gonochek II, Minitek, and RapID-NH kits could be confused with the results produced by some strains of N. gonorrhoeae. The susceptibility of N. cinerea to colistin, its ability to grow on tryptic soy or Mueller-Hinton agar, and its inability to grow on modified Thayer-Martin medium help differentiate it from gonococci.

Evaluation of a one-hour test for the identification of Neisseria species

This study presents an evaluation of the RIM-N kit (Austin Biological Laboratories, Inc., Austin, Tex.), a commercial system for rapid identification of Neisseria spp. and Branhamella catarrhalis. The system was compared with the cystine-Trypticase (BBL Microbiology Systems, Cockeysville, Md.) agar method; 218 isolates were tested by each method. There was 96% agreement between the two methods, and only nine discrepancies were encountered. The results suggest that the RIM-N kit may provide a rapid and reliable method for identifying Neisseria spp. and B. catarrhalis.

[Enzymatic profile and plasmid content of Neisseria polysacchareae]

The enzymatic profile of "Neisseria polysacchareae" was determined by using chromogenic substrate (API System), and was compared to that of N. meningitidis, N. gonorrhoeae and N. lactamica. The tested classes of enzymes were aminopeptidase, proteases, esterases, lipases, glycosidases, phosphatase and phosphoamidase. "N. polysacchareae" exhibited various aminopeptidase and protease activities and a strong esterase activity. No lipase and glycosidase activities were detected by the tested substrates. The strains of "N. polysacchareae" differed from that of N. meningitidis in the presence of hydroxyproline aminopeptidase and the lack of gamma-glutamyl-transferase activity. Five strains harboured extrachromosomal elements. The plasmids were of 4.2 Kb in size in four cases and of more than 40 Kb in four cases. Three strains simultaneously harboured these two plasmids. This plasmid content is another characteristic of strains of this new taxon. No phenotypic modification was observed in plasmid-containing strains.

Evaluation of the RIM system and Gono Gen test for identification of Neisseria gonorrhoeae from clinical specimens

RIM-N (Austin Biological Laboratories) and Gono Gen (Micro Media Systems) were evaluated for accuracy and compared with conventional carbohydrate degradation tests for identification of Neisseria gonorrhoeae. A total of 127 fresh clinical isolates of N. gonorrhoeae were tested; 118 (93%) were identified by RIM-N, and 100 (79%) yielded positive reactions with Gono Gen. Seventy nongonococcal isolates including other Neisseria species, Branhamella catarrhalis, Kingella kingae, and Moraxella species were evaluated to determine the specificity of the test methods. Both rapid tests were 100% specific in the identification of N. gonorrhoeae isolates. RIM-N was the most sensitive test for the identification of N. gonorrhoeae and offers a useful, more rapid alternative to conventional carbohydrate degradation methods.

Rapid confirmatory identification of Neisseria gonorrhoeae with lectins and chromogenic substrates

A group of five tests utilizing wheat germ and soybean lectins and chromogenic substrates (orthonitrophenyl-beta-D-galactopyranoside, gamma-glutamyl-beta-naphthylamide, and prolyl-beta-naphthylamide derivatives) was used as a rapid (30-min) method for the identification of Neisseria gonorrhoeae. The rapid method agreed with Minitek test results for all 126 N. gonorrhoeae isolates and all 39 nongonococcal isolates tested. Soybean lectin was useful for the identification of rare strains (4 of 126) of N. gonorrhoeae which are not agglutinated by wheat germ lectin. The chromogenic substrates differentiate N. gonorrhoeae from Neisseria meningitidis, Neisseria lactamica, and other Neisseria species which may grow on Thayer-Martin or other selective media.