Related Experiment Videos
Aeromonas schubertii, a new mannitol-negative species found in human clinical specimens
F W Hickman-Brenner1, G R Fanning, M J Arduino
1Enteric Bacteriology Section, Centers for Disease Control, Atlanta, Georgia 30333.
Abstract:
In 1983 the vernacular name Enteric Group 501 was coined for a group of strains that had been referred to our laboratory as "possible Vibrio damsela that does not require NaCl for growth." By DNA-DNA hybridization (hydroxyapatite method, 32P, 60 and 75 degrees C), six strains of Enteric Group 501 were closely related to the labeled strain 2446-81 (70 to 95% at 60 degrees C and 71 to 93% at 75 degrees C; 0 to 1% divergence). Type strains of all Aeromonas species and reference strains of six other Aeromonas DNA hybridization groups were 26 to 42% related (60 degrees C) to strain 2446-81, but type strains of 27 Vibrio and Photobacterium species, including V. damsela, were 0 to 1% (75 degrees C) related. We propose the name Aeromonas schubertii for the highly related group of seven strains formerly known as Enteric Group 501. The type strain is designated as ATCC 43700 (CDC 2446-81). Strains of A. schubertii grew well at 36 degrees C and had positive reactions at this temperature for methyl red, Voges-Proskauer (1% NaCl, Coblentz method), lysine decarboxylase, arginine dihydrolase, motility, lipase, DNase, nitrate reduction to nitrite, oxidase, and growth in nutrient broth with 0 and 1% NaCl. There was no growth in 6% NaCl or on thiosulfate-citrate-bile salts-sucrose agar. The following sugars were fermented: D-glucose, D-galactose, maltose, D-mannose, and trehalose. The following sugars were not fermented: adonitol, L-arabinose, D-arabitol, cellobiose, dulcitol, erythritol, myo-inositol, lactose, D-mannitol, melibiose, alpha-CH3-D-glucoside, raffinose, L-rhamnose, salicin, D-sorbitol, sucrose, and D-xylose. Esculin was not hydrolyzed, and the string test was negative. The mannitol-negative reaction differtiates A. schubertii from other Aeromonas species. The antibiogram of this organism is typical of other Aeromonas strains (resistance to ampicillin and carbenicillin and susceptibility to most other agents). A. schubertii strains have been isolated from abscesses (two strains), wound (one), skin (one), pleural fluid (one), and blood (two). The two blood isolates suggest clinical significance typical of other Aeromonas species , but further information is needed on this group.
Insights
A new bacterial species, Aeromonas schubertii, is proposed for strains previously known as Enteric Group 501. DNA-DNA hybridization confirmed its distinctness from Vibrio and other Aeromonas species, with unique biochemical characteristics.
Area of Science:
- Microbiology
- Bacterial Taxonomy
- Genetics
Background:
- Enteric Group 501 strains were previously identified as possible Vibrio damsela lacking NaCl growth requirement.
- Distinct phenotypic and genetic characteristics necessitated reclassification.
Purpose of the Study:
- To formally name and characterize a distinct group of bacterial strains.
- To differentiate these strains from known Vibrio and Aeromonas species using DNA-DNA hybridization and biochemical profiling.
Main Methods:
- DNA-DNA hybridization (hydroxyapatite method, 32P, 60 and 75°C) was used to assess genetic relatedness.
- Biochemical tests were performed to determine metabolic capabilities and identify key differentiating reactions.
- Antibiogram analysis and isolation source documentation were included.
Main Results:
- Six strains of Enteric Group 501 showed high DNA-DNA relatedness (70-95%) to strain 2446-81.
- These strains exhibited low relatedness (0-1%) to Vibrio damsela and moderate relatedness (26-42%) to other Aeromonas species.
- Key biochemical characteristics include positive methyl red, Voges-Proskauer, lysine decarboxylase, arginine dihydrolase, motility, lipase, DNase, and nitrate reduction; negative for 6% NaCl growth and mannitol fermentation.
Conclusions:
- The proposed name Aeromonas schubertii (type strain ATCC 43700) is established for this distinct group.
- The mannitol-negative reaction differentiates A. schubertii from other Aeromonas species.
- Clinical isolates suggest potential significance, warranting further investigation.