We determined the susceptibilities of 144 clinical and 49 environmental Aeromonas strains representing 10 different species to 26 antimicrobial agents by the agar dilution method. No single species had a predominantly nonsusceptible phenotype. A multidrug nonsusceptible pattern was observed in three (2.1%) clinical strains and two (4.0%) strains recovered from diseased fish. Common clinical strains were more resistant than the corresponding environmental isolates, suggesting that resistance mechanisms may be acquired by environmental strains from clinical strains.

Limited experience and a lack of validated diagnostic reagents make Burkholderia pseudomallei, the cause of melioidosis, difficult to recognize in the diagnostic microbiology laboratory. We compared three methods of confirming the identity of presumptive B. pseudomallei strains using a collection of Burkholderia species drawn from diverse geographic, clinical, and environmental sources. The 95 isolates studied included 71 B. pseudomallei and 3 B. thailandensis isolates. The API 20NE method identified only 37% of the B. pseudomallei isolates. The agglutinating antibody test identified 82% at first the attempt and 90% including results of a repeat test with previously negative isolates. Gas-liquid chromatography analysis of bacterial fatty acid methyl esters (GLC-FAME) identified 98% of the B. pseudomallei isolates. The agglutination test produced four false positive results, one B. cepacia, one B. multivorans, and two B. thailandensis. API produced three false positive results, one positive B. cepacia and two positive B. thailandensis. GLC-FAME analysis was positive for one B. cepacia isolate. On the basis of these results, the most robust B. pseudomallei discovery pathway combines the previously recommended isolate screening tests (Gram stain, oxidase test, gentamicin and polymyxin susceptibility) with monoclonal antibody agglutination on primary culture, followed by a repeat after 24 h incubation on agglutination-negative isolates and GLC-FAME analysis. Incorporation of PCR-based identification within this schema may improve percentages of recognition further but requires more detailed evaluation.Burkholderia pseudomallei, the cause of melioidosis, can be difficult to reliably identify in the clinical microbiology laboratory. Many diagnostic laboratories have no experience of this species. Even in locations such as Southeast Asia and northern Australia where melioidosis is endemic, a preponderance of septicemic cases during the wet season results in a low expectation of B. pseudomallei in clinical specimens at other times of year (1). Practical difficulties for the diagnostic laboratory include the presence of closely related Burkholderia species in specimens from nonsterile sites and atypical colony morphology of some B. pseudomallei strains (4). Despite clear recommendations for screening suspect B. pseudomallei colonies (3), there is wide variation in the approaches used by diagnostic laboratories. Moreover, a lack of properly validated diagnostic test reagents means that laboratories have to rely on biochemical tests for definitive identification. The substrate utilization test panels in current diagnostic use can generate misleading identification profiles (6).These problems and the rarity of melioidosis outside of northern Australia and Southeast Asia highlight the need for a more standardized culture-based diagnostic pathway. In the present study we evaluated phenotypic identification methods used in Australia to develop a laboratory case definition of melioidosis. This approach aims to integrate previou...

Genotypic characterization of 215 Aeromonas strains (143 clinical, 52 environmental, and 20 reference strains) showed that Aeromonas aquariorum (60 strains, 30.4%) was the most frequently isolated species in clinical and water samples and could be misidentified as Aeromonas hydrophila by phenotypic methods.