Aeromonas lusitana sp. nov., Isolated from Untreated Water and Vegetables.

During previous studies to evaluate the phylogenetic diversity of Aeromonas from untreated waters and vegetables intended for human consumption, a group of isolates formed a unique gyrB phylogenetic cluster, separated from those of all other species described so far. A subsequent extensive phenotypic characterization, DNA-DNA hybridization, 16S rRNA gene sequencing, multi-locus phylogenetic analysis of the concatenated sequence of seven housekeeping genes (gyrB, rpoD, recA, dnaJ, gyrA, dnaX, and atpD; 4705 bp), and ERIC-PCR, were performed in an attempt to ascertain the taxonomy position of these isolates. This polyphasic approach confirmed that they belonged to a novel species of the genus Aeromonas, for which the name Aeromonas lusitana sp. nov. is proposed, with strain A.11/6(T) (=DSMZ 24095(T), =CECT 7828(T)) as the type strain.

First case of Francisella bacteraemia in Western Australia.

Francisella species are Gram-negative, nonmotile, pleomorphic coccobacilli, facultative intracellular fastidious bacteria. We report the isolation of a Francisella-like species from a blood culture collected from a 44-year-old bacteraemic patient in Perth, Western Australia. The organism was identified to species level by 16S rRNA sequencing and by fatty acid methyl esters analysis. The strain genotypically resembled Francisella hispaniensis, a species previously isolated from human blood in Spain.

Aeromonas australiensis sp. nov., isolated from irrigation water.

A Gram-negative, facultatively anaerobic bacillus, designated strain 266(T), was isolated from an irrigation water system in the south-west of Western Australia. Analysis of the 16S rRNA gene sequence confirmed that strain 266(T) belonged to the genus Aeromonas, with the nearest species being Aeromonas fluvialis (99.6% similarity to the type strain, with 6 nucleotide differences) followed by Aeromonas veronii and Aeromonas allosaccharophila (both 99.5%). Analysis of gyrB and rpoD sequences suggested that strain 266(T) formed a phylogenetic line independent of other species in the genus. This was confirmed using the concatenated sequences of six housekeeping genes (gyrB, rpoD, recA, dnaJ, gyrA and dnaX) that also indicated that A. veronii and A. allosaccharophila were the nearest relatives. DNA-DNA reassociation experiments and phenotypic analysis further supported the conclusion that strain 266(T) represents a novel species, for which the name Aeromonas australiensis sp. nov. is proposed, with type strain 266(T) (=CECT 8023(T) =LMG 26707(T)). [corrected].

Antimicrobial susceptibilities of Aeromonas strains isolated from clinical and environmental sources to 26 antimicrobial agents.

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.

Aeromonas aquariorum is widely distributed in clinical and environmental specimens and can be misidentified as Aeromonas hydrophila.

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.

Phenotypic characteristics of human clinical and environmental Aeromonas in Western Australia.

AIM: To determine the phenotypic characteristics of 199 Aeromonas strains comprising 146 clinical and 53 environmental isolates. METHODS: Identification was based on a scheme consisting of 62 biochemical tests including two novel tests introduced as potential phenotypic markers. RESULTS: One hundred and eighty-five strains (93%) were identified to species level while eight (4%) resembled members of the Aeromonas hydrophila complex and six (3%) could not be assigned to any taxon. There were no significant phenotypic differences between clinical and environmental strains of the three most commonly isolated species A. hydrophila, Aeromonas veronii subspecies sobria and Aeromonas caviae. The most frequently isolated species in human clinical material and environmental samples was A. hydrophila (54.8% and 45.3%, respectively). CONCLUSIONS: Phenotypical identification showed that A. hydrophila was the most frequently isolated Aeromonas from clinical and water samples. The introduction of novel tests did not improve the discriminatory power of the scheme and the lack of definitive phenotypical markers continues to hinder Aeromonas taxonomy.

Expanded range of Burkholderia species in Australia.

This study describes the isolation and characterization of several Burkholderia species from soil in northern Australia. Phenotypic and molecular tests indicate that these isolates belong to the species Burkholderia thailandensis and Burkholderia ubonensis. These observations significantly extend our knowledge of the geographic distribution of these 2 species. Evidence of these species in Australia has implications for bacterial identification in clinical laboratories, diagnostic serology tests, and environmental biodiversity studies.

Endophthalmitis due to Williamsia muralis.

A case of endophthalmitis caused by Williamsia muralis is described. The infection occurred following a procedure known as intravitreal triamcinolone acetonide injection for the treatment of diabetic maculopathy. This is the first report of W. muralis as a causative agent of endophthalmitis.

Comparison of diagnostic laboratory methods for identification of Burkholderia pseudomallei.

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.

First description of Curtobacterium spp. isolated from human clinical specimens.

During a 4-year period, five strains (three of which were doubtless clinically significant) of yellow- or orange-pigmented, oxidative, slowly acid-producing coryneform bacteria were recovered from human clinical specimens in two reference laboratories or referred to them. The strains were motile, catalase positive, nitrate reductase negative, and urease negative, but strongly hydrolyzed esculin. In all reference and clinical strains described in the present study, anteisopentadecanoic (C(15:0ai)) and anteisoheptadecanoic (C(17:0ai)) acids represented more than 75% of all cellular fatty acids except in one clinical strain and in Curtobacterium pusillum, in which both the unusual omega-cyclohexyl fatty acid (identified as C(18:1omega7cis/omega9cis/omega12trans) by the Sherlock system) represented more than 50% of all cellular fatty acids. In all clinical strains, ornithine was the diamino acid of the cell wall, the interpeptide bridge consisted of ornithine, and acetyl was the acyl type of the peptidoglycan. Therefore, the five clinical strains were unambiguously identified as Curtobacterium spp. Analyses of the complete 16S rRNA genes of the five clinical strains with homologies to the established Curtobacterium species ranging from 99.2 to 100% confirmed the identifications as Curtobacterium spp. Data on the antimicrobial susceptibility pattern of curtobacteria are reported, with macrolides and rifampin showing very low MICs for all strains tested. This report is the first on the isolation of Curtobacterium strains from human clinical specimens.

Cellular fatty acid profile distinguishes Burkholderia pseudomallei from avirulent Burkholderia thailandensis.

Burkholderia pseudomallei, the cause of melioidosis, can be distinguished from the closely related but nonpathogenic Burkholderia thailandensis by gas chromatography (GC) analysis of fatty acid derivatives. A 2-hydroxymyristic acid derivative (14:0 2OH) was present in 95% of B. pseudomallei isolates and no B. thailandensis isolates. GC mass spectrophotometry confirmed that 2-hydroxymyristic acid was present in B. pseudomallei. GC-fatty acid methyl ester analysis may be useful in distinguishing these two closely related species.