Analysis of water and sediments collected in coastal waters of the Gulf of Mexico potentially affected by Hurricane Katrina to determine levels of human fecal indicators and pathogenic Vibrio species

We analyzed twenty-two water and eight sediment samples collected during the R/V NANCY FOSTER cruise of September 12-16, 2005. The results show that the numbers of microbial indicators of fecal contamination (E. coli and Enterococcus) in water samples did not exceed EPA guidelines for recreational waters (i.e., greater than 235 and 61 cells per 100 milliliters, respectively, EPA, 2004). Total numbers in 25 g of three sediment samples did exceed these levels for E. coli but only one of these same three samples exceeded the level for Enterococcus. While no standards exist for determining health risks from E. coli in sediments or soils, particularly in the marine environment (EPA, 2005), the presence of E. coli implies the presence of fecal contamination and exposure to these sediments should be limited. The same samples were analyzed for the presence of naturally-occurring marine Vibrio species, some of which can be pathogenic to humans. Nine of twenty-two water samples cultured positive for V. cholerae; characterization of these isolates with the cholera toxin gene probe (ctx) demonstrated that these are ctx negative or non-toxigenic. Ten water samples tested positive for V. vulnificus. In addition, eight of the water samples showed very low levels of other Vibrio species. Six of eight sediment samples showed the presence of non-toxigenic V. cholerae, while V. vulnificus was isolated from all eight sediment samples. However, the total numbers of these naturally occurring Vibrio species were very low and were at levels considered to be normal for Gulf Coast marine waters and sediments.