Cellulitis due to Shewanella algae: Crucial diagnostic clues from basic microbiological tests.

Area of Science:

• Medical Microbiology
• Infectious Diseases
• Clinical Case Study

Background:

• Shewanella species are increasingly recognized as emerging pathogens, particularly in tropical and subtropical regions.
• Human infections caused by Shewanella are rare but can be severe, often associated with underlying health conditions.

Observation:

• A middle-aged male with diabetes and hypertension presented with symptoms of congestive heart failure, fever, and a painful, erythematous right leg with scabs.
• Initial diagnosis considered decompensated heart failure, cellulitis, and uncontrolled hypertension.

Findings:

• Blood cultures revealed non-fermentative, oxidase-positive, motile Gram-negative bacilli.
• The isolate produced hydrogen sulfide on triple sugar iron agar and formed mucoid, weakly β-hemolytic colonies on blood agar.
• Initial identification as Shewanella putrefaciens by API 20 NE was revised to Shewanella algae based on 16S rRNA gene sequencing.

Implications:

• This case underscores the importance of accurate identification of Shewanella species in clinical microbiology.
• Early and appropriate antibiotic therapy, such as ceftazidime, is crucial for managing Shewanella-associated infections like cellulitis.
• Awareness of Shewanella algae as a potential pathogen is vital, especially in immunocompromised individuals and in endemic regions.