INVESTIGATING LONG-TERM TRENDS IN VIBRIOSIS SEVERITY AND RISK ASSOCIATED WITH WATER EXPOSURE AND CLIMATE-INDUCED STRESSORS IN THE CHESAPEAKE BAY: A MIXED METHODS STUDY

Abstract

The number of outbreaks and sporadic illnesses associated with non-cholera Vibrio spp. contaminated seafood and coastal water sources have been increasingly reported across the United States and many other nations, and may continue to rise as a result of ocean warming, adversely impacting public health. However, there are limited data concerning the trends in virulence and antibiotic resistance of these bacterial pathogens outside of Southern U.S. waters, including critical estuarine systems such as the Chesapeake Bay. Moreover, there are few studies that have evaluated longitudinal trends in Vibrio illness (vibriosis) among water users (recreational and commercial) and shellfish consumers in more northern states such as Maryland. To address these knowledge gaps my dissertation research involved 1) a retrospective longitudinal molecular analysis, as well as antimicrobial susceptibility testing, to evaluate changes in V. vulnificus and V. parahaemolyticus antibiotic resistance patterns and virulence factors; and 2) an epidemiological study using publicly-available data to evaluate vibriosis trends. My specific aims were as follows: 1) To evaluate changes in virulence factors among V. vulnificus and V. parahaemolyticus isolates recovered from the Chesapeake Bay between 2009-2022; 2) To evaluate changes to antibiotic susceptibility among V. vulnificus and V. parahaemolyticus isolates recovered from the Chesapeake Bay between 2009-2022; and 3) To evaluate long-term trends in the incidence of severe vibriosis among water users (recreational and commercial) and shellfish consumers in Maryland between 2006-2019. Overall, my results indicate that potentially pathogenic V. vulnificus and V. parahaemolyticus occur across the Chesapeake Bay throughout every season, including at frequencies that may still lead to an increased risk of infection in the fall and possibly early winter. Moreover, the mid and lower sections of the Bay, which include many commercial and recreationally important areas, may harbor a greater risk of severe vibriosis from wound-associated water exposures, given the greater presence of V. vulnificus isolates characterized by clinically-relevant virulence factors. Interestingly, I also found that antibiotic resistance patterns among V. vulnificus and V. parahaemolyticus isolates collected from Tangier Sound in the lower Chesapeake Bay have remained relatively stable since 2009. Notwithstanding, recovered Vibrio spp. isolates exhibited varying levels of resistance and intermediate-resistance to antibiotics used to treat severe vibriosis, underscoring the need for prompt diagnosis and treatment with effective first line antibiotic agents. Finally, my epidemiological analysis revealed that long-term increases in Vibrio infections, notably V. vulnificus wound infections, are occurring in Maryland. This trend, along with increased rates in hospitalizations and average hospital durations, underscore the need to improve public awareness, water monitoring, post-harvest seafood interventions, and environmental forecasting, particularly as our climate warms and creates environmental conditions that support the growth of estuarine vibrios.