Thirteen Yersinia enterocolitica were recovered from a variety of clinical sources. Of these, only one was associated with mesenteric lymphadenitis and belonged to serotype 8. The 12 remaining strains were isolated from nonmesenteric sources and belonged to serotype 17. All strains exhibited the main characteristics of Y. enterocolitica which differentiated them from other Enterobacteriaceae, i.e., motility at 22 C but not at 37 C, positive urease and ornithine decarboxylase activities, and negative phenylalanine deaminase. These 12 strains differed, however, from other Y. enterocolitica previously described in the United States in that they fermented rhamnose and raffinose at 22 C, and failed to grow on Salmonella-Shigella and Hektoen-Enteric agars.

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A simple and rapid semiquantitative slide catalase test useful for the identification of oxidative and nonsaccharolytic gram-negative bacteria, i.e., "nonfermenters," is described. Using the intrepretative criterion of time of appearance of oxygen bubbles in 3% hydrogen peroxide, three categories of nonfernenters were established. The rapid catalase producers included Achromobacter xylosoxidans and Achromobacter species; Acinetobacter anitratus and Acinetobacter lwoffii; Bordetella bronchiseptica; CDC group IVE; Pseudomonas aeruginosa, P. fluorescens, P. putida, P. diminuta, and P. acidovorans; and Moraxella urethralis and M-6. The delayed catalase producers included Bordetella parapertussis, CDC group VA-1, P. alcaligenes, P. cepacia, P. mendocina, P. pickettii (VA-2), P. pseudoalcaligenes, P. putrefaciens, P. stutzeri, P. testosteroni, and P. vesicularis. The third group consisted of an additional 17 taxa of nonfermenters which were classified as moderate catalase producers.

Legionella pneumophila serogroup 1 was isolated from antemortem aerobic blood culture bottles not supplemented with L-cysteine or ferric pyrophosphate and from the postmortem lung tissue of a 72-year-old man. We recommend that aerobic blood culture bottles (Johnston Laboratories, Cockeysville, Md.) of BACTEC be subcultured to an agar that supports the growth of L. pneumophila when growth indexes range from 30 to 60 but fail to increase further.