Vibrio cholerae and enteric bacteria in oyster-producing areas of two urban estuaries in Australia

Spatiotemporal Dynamics of Vibrio spp. within the Sydney Harbour Estuary

Vibrio are a genus of marine bacteria that have substantial environmental and human health importance, and there is evidence that their impact may be increasing as a consequence of changing environmental conditions. We investigated the abundance and composition of the Vibrio community within the Sydney Harbour estuary, one of the most densely populated coastal areas in Australia, and a region currently experiencing rapidly changing environmental conditions. Using quantitative PCR (qPCR) and Vibrio-specific 16S rRNA amplicon sequencing approaches we observed significant spatial and seasonal variation in the abundance and composition of the Vibrio community. Total Vibrio spp. abundance, derived from qPCR analysis, was higher during the late summer than winter and within locations with mid-range salinity (5-26 ppt). In addition we targeted three clinically important pathogens: Vibrio cholerae, V. Vulnificus, and V. parahaemolyticus. While toxigenic strains of V. cholerae were not detected in any samples, non-toxigenic strains were detected in 71% of samples, spanning a salinity range of 0-37 ppt and were observed during both late summer and winter. In contrast, pathogenic V. vulnificus was only detected in 14% of samples, with its occurrence restricted to the late summer and a salinity range of 5-26 ppt. V. parahaemolyticus was not observed at any site or time point. A Vibrio-specific 16S rRNA amplicon sequencing approach revealed clear shifts in Vibrio community composition across sites and between seasons, with several Vibrio operational taxonomic units (OTUs) displaying marked spatial patterns and seasonal trends. Shifts in the composition of the Vibrio community between seasons were primarily driven by changes in temperature, salinity and NO2, while a range of factors including pH, salinity, dissolved oxygen (DO) and NOx (Nitrogen Oxides) explained the observed spatial variation. Our evidence for the presence of a spatiotemporally dynamic Vibrio community within Sydney Harbour is notable given the high levels of human use of this waterway, and the significant increases in seawater temperature predicted for this region.

Cholera: Environmental Reservoirs and Impact on Disease Transmission

Vibrio cholerae is widely known to be the etiological agent of the life-threatening diarrheal disease cholera. Cholera remains a major scourge in many developing countries, infecting hundreds of thousands every year. Remarkably, V. cholerae is a natural inhabitant of brackish riverine, estuarine, and coastal waters, and only a subset of strains are known to be pathogenic to humans. Recent studies have begun to uncover a very complex network of relationships between V. cholerae and other sea dwellers, and the mechanisms associated with the occurrence of seasonal epidemics in regions where cholera is endemic are beginning to be elucidated. Many of the factors required for the organism's survival and persistence in its natural environment have been revealed, as well as the ubiquitous presence of horizontal gene transfer in the emergence of pathogenic strains of V. cholerae. In this article, we will focus on the environmental stage of pathogenic V. cholerae and the interactions of the microorganism with other inhabitants of aquatic environments. We will discuss the impact that its environmental reservoirs have on disease transmission and the distinction between reservoirs of V. cholerae and the vectors that establish cholera as a zoonosis.

Antibiotic-resistant Escherichia coli in wastewaters, surface waters, and oysters from an urban riverine system

The antibiotic resistance (AR) patterns of 462 Escherichia coli isolates from wastewater, surface waters, and oysters were determined. Rates of AR and multiple-AR among isolates from surface water sites adjacent to wastewater treatment plant (WWTP) discharge sites were significantly higher (P < 0.05) than those among other isolates, whereas the rate of AR among isolates from oysters exposed to WWTP discharges was low (<10%).

Role of type IV pilins in persistence of Vibrio vulnificus in Crassostrea virginica oysters

Vibrio vulnificus is part of the natural estuarine microflora and accumulates in shellfish through filter feeding. It is responsible for the majority of seafood-associated fatalities in the United States mainly through consumption of raw oysters. Previously we have shown that a V. vulnificus mutant unable to express PilD, the type IV prepilin peptidase, does not express pili on the surface of the bacterium and is defective in adherence to human epithelial cells (R. N. Paranjpye, J. C. Lara, J. C. Pepe, C. M. Pepe, and M. S. Strom, Infect. Immun. 66:5659-5668, 1998). A mutant unable to express one of the type IV pilins, PilA, is also defective in adherence to epithelial cells as well as biofilm formation on abiotic surfaces (R. N. Paranjpye and M. S. Strom, Infect. Immun. 73:1411-1422, 2005). In this study we report that the loss of PilD or PilA significantly reduces the ability of V. vulnificus to persist in Crassostrea virginica over a 66-h interval, strongly suggesting that pili expressed by this bacterium play a role in colonization or persistence in oysters.

Prevalence and diversity of Aeromonas and Vibrio spp. in coastal waters of Southern Italy

A survey was undertaken to examine sea water and sediment for the presence of Vibrio and Aeromonas spp. along approximately 900 km of coast in Southern Italy during early and late summer. A quantitative analysis was also done to evaluate the water fecal contamination at the stations examined. The results indicate that all the investigated areas were submitted to a wide spatial fluctuation of fecal contamination and that Vibrio and Aeromonas spp. were present in both high and low fecal-contaminated stations. Sixty two percent of the investigated samples were positive for Aeromonas spp., while 42% of samples were positive for Vibrio spp. It was interesting to note that 38% of the positive stations for both Aeromonas and Vibrio spp. showed a fecal coliform contamination of water at < 10(2) cells 100 ml(-1). Thus, these findings support the hypothesis that the bacterial indicators (such as fecal coliforms) do not always satisfactorily reflect the hygienic quality of water. The presence of Vibrionaceae on copepods was also investigated. Copepods were sampled at a station located inside the harbour of the city of Naples and were found contaminated by V. cholerae non-O1, V. alginolyticus, V. fluvialis and A. caviae. Furthermore, the antibiotic resistance patterns of isolated bacteria showed the presence of a number of resistant strains among the isolates. In order to discriminate the isolates on the basis of their biochemical profiles and/or antibiotic resistance patterns, cluster analysis was carried out which showed that no unique assay could fully discern these isolates. However, the best discrimination resulted from complete pattern profile based on both biochemical profiles and antibiotic resistance patterns.