**10.3** *Aeromonas hydrophila* **infection**

Lethal gangrene of the extremities or face is also caused by *Aeromonas hydrophila* in patients under an immunocompromised condition, with diabetes mellitus or on hemodialysis, as a form of opportunistic infection [100–104]. The bacteria invade the skin via a minor trauma. **Figure 35** illustrates gross features of lethal gangrene of the right upper arm caused by *A. hydrophila*. Vesicles are formed on the necrotic skin. *A. hydrophila* belongs to the family *Vibrio* and widely distributes in fresh water and soil. *A. hydrophila* can grow at low temperature to cause food poisoning (watery or bloody diarrhea) due to production of heat-labile enterotoxins. An outbreak of *A. hydrophila* wound infection has also been reported among the participants for mud football games in Australia [105]. There were many infected scratches and pustules distributed over the bodies.

Microscopically, the lesion shows clusters of Gram-negative rods around necrotic subcutaneous tissue. Cellular reaction is poor. Gas formation may be associated. In the case as shown in **Figure 36**, necrotizing foci of infection were disseminated in the rectum, epididymis, prostate, liver, and kidneys.
