Prevalence of urease in Vibrio parahaemolyticus from the Mississippi Sound
T R Berutti1, R E Williams, S Shen
1Gulf Coast Research Laboratory, The University of Southern Mississippi, Ocean Springs, MS, USA.
Unlabelled:
Vibrio parahaemolyticus is a pathogenic marine bacterium that causes food-borne gastroenteritis and, less commonly, wound infections. As is the case for many pathogens, all V. parahaemolyticus strains possess at least one erythrocyte-lysing haemolysin. In addition, many V. parahaemolyticus also possess the enzyme urease. We tested 206 environmental V. parahaemolyticus isolates from Mississippi coastal waters for urease and haemolytic activity using urea agar with added salt and Wagatsuma agar, respectively. The relative abundance of haemolysin-producing V. parahaemolyticus was consistently high throughout the sampling period. In contrast, the number of urease-positive organisms increased from 36% in 2006 to 80% in 2007 and 97% in 2009. We then tested the ability of four strains representing each of the three sample years along with seven other bacterial strains for their ability to grow in seawater urea and raise the pH of this seawater broth. Finally, one of the 4 strains was tested for its ability to form an alkaline microhabitat immediately above its biofilm.
Significance And Impact Of The Study:
The results of this study illustrate that V. parahaemolyticus has the ability to create alkaline microhabitats that could enhance virulence, including virulence from haemolysins. This finding could have both clinical and ecological impact as to how V. parahaemolyticus can modify its habitat.
Insights
The marine bacterium Vibrio parahaemolyticus can create alkaline microhabitats, potentially increasing its virulence. This study tracked urease activity in environmental isolates, revealing a significant rise over time.
Area of Science:
- Marine microbiology
- Bacterial pathogenesis
- Environmental microbiology
Background:
- Vibrio parahaemolyticus is a marine bacterium causing foodborne illness.
- All strains produce haemolysins; many also produce urease.
- Urease activity in V. parahaemolyticus is not fully understood in environmental contexts.
Purpose of the Study:
- To investigate urease and haemolytic activity in environmental V. parahaemolyticus isolates.
- To determine the prevalence and trends of urease-positive V. parahaemolyticus.
- To assess the ability of V. parahaemolyticus to create alkaline microhabitats.
Main Methods:
- Tested 206 environmental V. parahaemolyticus isolates from Mississippi coastal waters.
- Assessed urease activity using urea agar with added salt.
- Assessed haemolytic activity using Wagatsuma agar.
- Evaluated bacterial growth in seawater urea and pH changes.
- Examined biofilm formation and alkaline microhabitat creation.
Main Results:
- Haemolysin-producing V. parahaemolyticus were consistently abundant.
- Urease-positive V. parahaemolyticus increased from 36% (2006) to 97% (2009).
- Selected strains demonstrated growth in urea-rich seawater, increasing pH.
- One strain formed an alkaline microhabitat above its biofilm.
Conclusions:
- Vibrio parahaemolyticus can create alkaline microhabitats.
- These microhabitats may enhance bacterial virulence, including haemolysin activity.
- Findings have potential clinical and ecological implications for V. parahaemolyticus habitat modification.
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