No abstract

Three systems for the identification of nonfermentative bacilli were evaluated for their rapidity and accuracy of identification of 217 strains. Two of the systems, API 20E (API) and Oxi/Ferm tube (OxiF), are available as kits; the oxidative attack (OA) system is not commercially available. The overall accuracies of the OA, API, and OxiF systems were 91, 69, and 50%, respectively. Identification within 48 h was achieved for 98% of the strains by OA, for 50% by API, and for 18% by OxiF. Most of the organisms that were either misidentified or not identified by API and OxiF were those nonfermentative bacilli which are relatively more fastidious or rarely encountered or both. All three systems accurately identified nonfermentative bacilli commonly isolated at Olive View Medical Center, namely, Pseudomonas aeruginosa, Acinetobacter anitratus, Pseudomonas maltophilia, Acinetobacter Iwoffi, saccharolytic flavobacteria (CDC IIb), moraxellae, Pseudomonas fluorescens, and Pseudomonasputida. The OA system identified 100% of the above organisms correctly, API identified 99.4%, and OxiF identified 99.3%. Since these organisms comprise 92% of the total number of nonfermentative bacilli isolated at Olive View Medical Center, we conclude that both API and OxiF may be useful alternatives to conventional methods, based on accuracy of identification alone. These two systems were considered substantially inferior to the OA system when both accuracy and rapidity of identification were taken into account.

A rapid system (OA), based on oxidative attack of substrates, was developed for identification of gram-negative, nonfermentative bacillia (NFB). One hundred and twelve strains of NFB from 25 species (representing the genera Pseudomonas, Alcaligenes, Acinetobacter, Bordetella, Flavobacterium, Moraxella, and Xanthomonas) were assayed by OA, buffered single substrate, and oxidative/fermentative methods. The 38 substrates consisted of salts of organic acids, nitrogen-containing compounds, alcohols, and carbohydrates. Ninety-four percent of the test strains were identified by the OA method in 24 h, and 99% were identifiable in 48 h. Reproducibility was 99%. Correlation with buffered single substrate was 98% (all substrates) and 90% with the oxidative/fermentative method (carbohydrates only). Biochemical profiles of all strains are presented, as well as tables showing the most useful tests for identification.

Biochemical characteristics and antibiotic susceptibilities of five strains of Pseudomonas vesicularis isolated from cervical cultures are reported. The organisms were recovered from Thayer-Martin medium, which, because of its inhibitory properties, restricts over-growth by most other species. Our findings agree with those of Kaltenbach and associates (J. Clin. Microbiol., 1:339--344, 1975) on the importance of esculin hydrolysis, maltose oxidation, and pigmentation in the identification of P. vesicularis. Comparative carbohydrate oxidation studies showed agreement in three of four methods (oxidative attack, buffered single substrate, King oxidative/fermentative medium). No oxidation of carbohydrates was observed in commercial oxidative/fermentative medium. In addition to biochemical characteristics, antibiograms can be useful auxiliary aids in the identification of P. vesicularis and in its differentiation from P. diminuta, a closely related species.