Wound infections caused by Vibrio vulnificus and other marine bacteria

Infections caused by Vibrio vulnificus were first reported in 1979 by Blake et al. of the US Centers for Disease Control. At that time described as a ‘rare, unnamed halophilic lactose-fermenting Vibrio species’, V. vulnificus has emerged as the most virulent foodborne pathogen in the United States with a hospitalization rate of 0·910 and a case-fatality rate of 0·390. It is in addition a significant cause of potentially life-threatening wound infections. Infections following ingestion of raw or undercooked seafood, commonly raw oysters, can lead to a primary septicaemia with a fatality rate of 50–60%. An unusual symptom, occurring in 69% of 274 cases reviewed by Oliver, is the development of secondary lesions, typically on the extremities, which are generally severe (often a necrotizing fasciitis) and require tissue debridement or amputation. These cases occur almost exclusively in males over the age of 50 years. Interestingly, this gender specificity has been found to be due to the female hormone oestrogen, which in some manner provides protection against the lethal V. vulnificus endotoxin. Further, most cases occur in persons with certain underlying diseases which are either immunocompromising or which lead to elevated serum iron levels (e.g. liver cirrhosis, chronic hepatitis, haemochromatosis). V. vulnificus infections resulting in primary septicaemia have been extensively studied, and the subject of several reviews. This review concentrates on the wound infections caused by this marine bacterial pathogen, including the more recently described biotypes 2 and 3, with brief discussions of those caused by other marine vibrios, and the increasingly reported wound/skin infections caused by Mycobacterium marinum, Erysipelothrix rhusiopathiae, and Aeromonas hydrophila.

Phylogenetic study and identification of human pathogenicVibriospecies based on partialhsp60 gene sequences

The use of hsp60 gene sequences for phylogenetic study and identification of pathogenic marine vibrios was investigated. A 600-bp partial hsp60 gene was amplified by PCR and sequenced from 29 strains representing 15 Vibrio species within the family Vibrionaceae. Sequence comparison of the amplified partial hsp60 gene revealed 71–82% sequence identity among different Vibrio species and 96–100% sequence identity among epidemiologically distinct strains with the same species designation. This degree of discrimination allows unambiguous differentiation of all Vibrio species included in the current study from each other, as well as from Aeromonas hydrophila and Plesiomonas shigelloides, which are often misidentified as Vibrio species by conventional biochemical methods. Based on the hsp60 gene sequences, two previously unidentified shrimp isolates were found to be more closely related to Vibrio alginolyticus (93–94% sequence identity) than to Vibrio parahaemolyticus (89% sequence identity), whereas 16S rRNA gene analysis was unable to differentiate among these closely related species (95–97% sequence identity). Our results indicate that the hsp60 gene may be a useful alternative target for phylogenetic analysis and species identification of marine Vibrios to complement more conventional identification systems.Key words: Vibrio, hsp60, 16S rRNA, phylogenetic analysis, species identification.

Survival of Vibrio cholerae 01 Strains in Shrimp Subjected to Freezing and Boiling

This research was undertaken to assess the resistance of Vibrio cholerae 01 strains inoculated into white shrimp, Penaeus schimitti, to heating and freezing treatments. Shrimp samples with and without carapace were obtained from Sao Luis, Brazil. Microbial analysis revealed the presence of marine vibrios including Vibrio alginolyticus, Vibrio parahaemolyticus, and other vibrios and aerobic gram-negative and gram-positive bacteria that grew on selective medium, thiosulfate-citrate-bile salt-sucrose agar. Samples with and without carapaces were heated before inoculating with cells of V. cholerae and then one-half of the samples was stored frozen at −200°C and the other one-half was heated to boiling temperatures. Viable cells of the test organism were recovered from samples without carapaces, stored under frozen conditions, after 36 days. In contrast, no living cells were recovered after 26 days from samples with carapaces. Boiling temperatures were very damaging to V. cholerae 01 in shrimp samples with and without carapaces. Total destruction of the cells occurred within 1 to 2 min of exposure to heating.