**10.2** *Vibrio vulnificus* **infection**

Progressive gangrene of the extremities caused by infection of *Vibrio vulnificus* is characteristically seen in patients with liver cirrhosis or hemochromatosis [96–99]. High iron concentration in the serum is essential for the bacteria to grow in the body. The genus *Vibrio* is categorized in the "halophilic" bacteria preferring to a high salt concentration for growth on plates. In contrast to *V. cholerae* and *V. parahaemolyticus* growing at the salt concentration of sea water (3–3.5%), *V. vulnificus* prefers to a lower salt concentration of the brackish (estuarine) water at the mouse of the river. *V. vulnificus* resides in the sea fish and oyster, particularly during the summertime. The bacteria proliferate in the gut of the sea creature when the temperature is high. Two transmission pathways of the pathogen are known: transenteric infection and traumatic skin infection. The former septicemic condition is often fatal, initiating a painful skin lesion on the arm or leg resembling honeybee bite. Gangrenous changes of the extremity progress rapidly.

#### **Figure 33.**

*Fulminant streptococcal infection (streptococcal myonecrosis) (Giemsa, H&E and Gram). Numerous chained cocci are demonstrated in the cultured blood. Vessels are thrombosed, and the striated muscle fibers show coagulation necrosis. Colonies of Gram-positive cocci are scattered in the ischemic tissue.*

**Figure 32** demonstrates a diabetic male patient aged 80's, suffering from nomalike condition (progressive ulcerative gingivitis with massive maxillary necrosis). Numerous bacilli accompanying gas formation and immunoreactive with *E. coli*

*Noma-like condition in a diabetic male patient aged 80's (progressive ulcerative gingivitis) (H&E, Grocott and*

*immunostain). A gas-forming, necrotizing lesion is observed in the biopsied maxillary bone. Grocott methenamine silver stain identifies colonies of filamentous bacteria in the lesion, probably representing* Actinomyces *colonization. The Gram-negative bacteria around the gas bubble are immunoreactive with a commercial antiserum against* Escherichia coli*, which shows wide cross-reactivity to Gram-negative bacteria (the courtesy by Dr. Tatsuru Ikeda, Pathology Center, Hakodate Goryoukaku Hospital, Hakodate, Japan).*

A variety of microbes cause progressive and often lethal gangrenous lesions in

Streptococcal myonecrosis, a fulminant form of necrotizing fasciitis, presents a rapidly progressive gangrene of the extremities caused by infection of *Streptococcus pyogenes* (group A β-hemolytic *Streptococcus*), representing a prototype of "flesheating bacteria infection" [89, 90]. The disease affects persons of any age. Groups B and G β-hemolytic *Streptococcus* may also cause an identical fulminant condition [91, 92]. In some cases, protein S deficiency may be responsible for the necrotizing inflammation. It has been reported that vimentin, an intracellular intermediate filament of nonepithelial cells, is upregulated in the injured skeletal muscle cells and functions as the major skeletal-muscle protein binding to streptococci [93]. The lifethreatening gangrene follows the subacute form of necrotizing fasciitis or occurs suddenly without preexisting ulceration. As shown in **Figure 5**, an advanced, deep pocket-forming decubitus in the sacral region may cause the lethal gangrenous

the soft tissue, particularly on the extremities. The mass media often call this frightening condition as "flesh-eating bacteria infection." Three representative forms, fulminant streptococcal infection, *Vibrio vulnificus* infection, and *Aeromonas*

**10.1 Fulminant streptococcal infection (streptococcal myonecrosis)**

antiserum grew in the maxillary bone. Colonies of filamentous bacteria,

representing anaerobic *Actinomyces* spp., were coinfected.

lesion categorized in non-clostridial gas gangrene [18].

**10. Flesh-eating bacteria infection**

**Figure 32.**

*Pathogenic Bacteria*

**116**

*hydrophila* infection, are described below.

Gas formation is not associated. The traumatic infection of *V. vulnificus* is caused by an accidental trauma of the hand or fingers during cooking raw fish (preparing sashimi) or injuring the foot on the rocky seacoast. The prognosis is better than the former. The incidence of infection of the halophilic pathogen nicknamed "flesheating bacteria" is high in Japan.

Microscopically, perivascular cuffing of Gram-negative bacteria, showing a coccoid change, is noted in the involved ischemic/necrotic skin and soft tissue, while the cellular reaction is minimal (**Figure 34**).
