Relation to Human Health

**87**

**Chapter 5**

**Abstract**

**1. Introduction**

Hemolysin of *Vibrio* Species

hemolysins from *Vibrio* species, which has been reported so far.

*Vibrio parahaemolyticus*, *vibrio cholerae*, *vibrio mimicus*, *vibrio vulnificus*

**Keywords:** thermostable direct hemolysin, El Tor hemolysin,

the probability of infections caused by them.

*Tamaki Mizuno, Anusuya Debnath and Shin-ichi Miyoshi*

Hemolysin is one of the major pathogenic factors among *Vibrio* species, which shows hemolytic activity against erythrocytes. It is associated with different *Vibrio* spp. that manifest either wound infection or intestinal infection as their clinical symptom. *V. vulnificus* and *V. alginolyticus* are well-known causative organisms for wound infection, whereas the gastrointestinal infection is caused by *V. cholerae*, *V. mimicus*, and *V. parahaemolyticus*. There are two major groups of hemolysins in *Vibrio* spp.: the thermostable direct hemolysin (TDH) from *V. parahaemolyticus* and the HlyA (El Tor hemolysin) from *V. cholerae*. These hemolysins have homology in certain degrees; however, the essential amino acids for the activity are variable depending on the species. This chapter summarizes the functions and features of

The genus *Vibrio* is comprised of facultative, anaerobic, Gram-negative, curvedrod bacteria that are widely found in natural aquatic environments such as marine, estuarine, and freshwater [1]. More than 100 species have been currently described in this genus, and at least 12 species represented by *V. cholerae*, *V. parahaemolyticus*, and *V. vulnificus* cause a variety of clinical symptoms in human (Table) [1–5]. In addition, species such as *V. metoecus* and *V. navarrensis* are among the newly isolated species from human, and it is strongly suggested that they are human pathogens of *Vibrio* spp. [6, 7]. On the other hand, the major pathogenic *Vibrio* for aquatic vertebrates or invertebrates are *V. anguillarum*, *V. harveyi*, *V. ordalii* etc., responsible for fatal hemorrhagic septicemic disease called vibriosis in marine animals [5, 8–10]. *Vibrio* spp. prefer warm water temperature (15–35°C), so they are likely to flourish more with rising environmental water temperature due to global warming and thus

Human diseases caused by pathogenic *Vibrio* spp. can be divided into two major types based on symptoms: intestinal infection and non-intestinal infection [1, 3]. The intestinal infection includes gastroenteritis and cholera, whereas nonintestinal infection includes septicemia and wound infection (**Table 1**). Cholera is caused by ingestion of food and drinking water contaminated with *V. cholerae* O1/O139 that produces cholera toxin (CT) as a major virulence determinant and characterized by severe diarrhea that rapidly leads to dehydration [11, 12]. Till date it remains a major public health disease with estimated 2.9 million cases and 95,000 deaths annually worldwide [13]. There are many clinical cases of gastroenteritis by *V. parahaemolyticus* due to ingestion of raw fish and shellfish [14, 15].
