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Shewanella algae and Shewanella putrefaciens: clinical and microbiological characteristics
H M Holt1, B Gahrn-Hansen, B Bruun
1Department of Clinical Microbiology, Odense University Hospital, Odense, Denmark. hanne.holt@ouh.fyns-amt.dk
Summary
Shewanella infections, often linked to warm seawater, commonly affect skin and ears. Accurate identification of Shewanella algae versus Shewanella putrefaciens is crucial due to differing pathogenic potential.
Area of Science:
- Clinical microbiology
- Bacteriology
- Environmental microbiology
Background:
- Shewanella species, including Shewanella algae and Shewanella putrefaciens, are found in clinical specimens and their occurrence correlates with seawater temperature and salinity.
- Shewanella infections typically manifest in warm climates or during warm seasons, primarily affecting the ears, skin, and soft tissues, sometimes with associated bacteraemia.
- Immunocompromised individuals are susceptible to primary bacteraemia with a severe course caused by Shewanella.
Purpose of the Study:
- To highlight the importance of differentiating between Shewanella algae and Shewanella putrefaciens in clinical settings.
- To address the challenges in accurate identification due to limitations in automated systems.
- To emphasize the distinct pathogenic potential of these two Shewanella species in human infections.
Main Methods:
- Phenotypic characterization of Shewanella species.
- Comparison of biochemical and growth characteristics between S. algae and S. putrefaciens.
- Evaluation of automated identification system capabilities for Shewanella differentiation.
Main Results:
- Shewanella algae exhibits distinct characteristics from Shewanella putrefaciens, including mucoid colonies, beta-haemolysis, growth at 42°C and 6% NaCl, and nitrite reduction.
- Automated identification systems often fail to distinguish between S. algae and S. putrefaciens because S. algae is not consistently included in their databases.
- Extensive phenotypic analysis reveals that Shewanella algae is frequently the causative agent of human Shewanella infections, contrary to attributions often made to S. putrefaciens.
Conclusions:
- Accurate identification of Shewanella species is essential due to their differing pathogenic potentials.
- Routine clinical microbiology laboratories can achieve correct identification through comprehensive phenotypic characterization.
- Clinical and epidemiological data suggest Shewanella algae may be more prevalent in human infections than previously reported.