Vibrio vulnificus infection

Vibrio vulnificus is a species of Gram-negative, motile, curved rod-shaped (bacillus), pathogenic bacteria of the genus Vibrio. Present in marine environments such as estuaries, brackish ponds, or coastal areas, V. vulnificus is related to V. cholerae, the causative agent of cholera. Infection with V. vulnificus leads to rapidly expanding cellulitis or sepsis.:279 It was first isolated as a source of disease in 1976. V. vulnificus is an extremely virulent bacterium that can cause three types of infections: Among healthy people, ingestion of V. vulnificus can cause vomiting, diarrhea, and abdominal pain. In someone with a compromised immune system, particularly those with chronic liver disease, it can infect the bloodstream, causing a severe and life-threatening illness characterized by fever and chills, decreased blood pressure (septic shock), and blistering skin lesions. While men have been shown to be more at risk from this infection than women, co-morbidities such as alcoholic cirrhosis and diseases affecting the endocrine system (diabetes, rheumatoid arthritis, etc.) put a person far more at risk to develop infection from V. vulnificus. Capsule: V. vulnificus has a capsule, made of polysaccharides, and is thought to protect against phagocytosis. The capsule also aids the bacteria in escaping opsonization. Different strains of the bacteria are capable of shifting through the unencapsulated and encapsulated forms. Mouse models have shown that the unencapsulated forms are avirulent. These same strains however, are shown to have a higher predisposition to shift to the virulent encapsulated form when taken up by oysters. Endotoxin: Like all gram negative bacteria, V. vulnificus has LPS (lipopolysaccharide as the major component of its outer membrane). However, the LPS the bacteria produces isn't as efficient at triggering the immune system's release of tumor necrosis factor (TNF) alpha and other cytokines that produce shock syndromes. The capsular proteins the bacteria express however, are capable of producing an immune response contributing to shock syndrome. Exotoxin: V. vulnificus produces a number of extracellular toxins such as metalloprotease VvpE, cytolysin/hemolysin VvhA, and the multifunctional autoprocessing repeats-in-toxins (MARTX) toxin. While the VvhA and MARTX toxin are factors in the bacteria's virulence, in vivo studies in mice suggest that the MARTX toxin is more responsible for bacterial dissemination from the intestine to produce sepsis. Iron: Growth of V. vulnificus is dependent on the amount of iron that is accessible to the bacteria. The observed association of the infection with liver disease (associated with increased serum iron) might be due to the capability of more virulent strains to capture iron bound to transferrin.