This study uses one of the largest data sets compiled to model Vibrio in an estuary, enhances our understanding of environmental correlates with abundance, distribution and presence of potentially virulent strains and offers a method to forecast these pathogens that may be replicated in other regions.
Environmental mycobacteria are of increasing concern in terms of the diseases they cause in both humans and animals. Although they are considered to be ubiquitous in aquatic environments, few studies have examined their ecology, and no ecological studies of coastal marine systems have been conducted. This study uses indirect gradient analysis to illustrate the strong relationships that exists between coastal water quality and the abundance of Mycobacterium spp. within a U.S. mid-Atlantic embayment. Mycobacterium species abundance and water quality conditions (based on 16 physical and chemical variables) were examined simultaneously in monthly samples obtained at 18 Maryland and Virginia coastal bay stations from August 2005 to November 2006 (n ؍ 212). A quantitative molecular assay for Mycobacterium spp. was evaluated and applied, allowing for rapid, direct enumeration. By using indirect gradient analysis (environmental principalcomponents analysis), a strong linkage between eutrophic conditions, characterized by low dissolved-oxygen levels and elevated nutrient concentrations, and mycobacteria was determined. More specifically, a strong nutrient response was noted, with all nitrogen components and turbidity measurements correlating positively with abundance (r values of >0.30; P values of <0.001), while dissolved oxygen showed a strong negative relationship (r ؍ ؊0.38; P ؍ 0.01). Logistic regression models developed using salinity, dissolved oxygen, and total nitrogen showed a high degree of concordance (83%). These results suggest that coastal restoration and management strategies designed to reduce eutrophication may also reduce total mycobacteria in coastal waters.
Aims: To determine the prevalence of total and pathogenic Vibrio parahaemolyticus (Vp) and V. vulnificus (Vv) in blue crabs, water and sediment from the Maryland Coastal Bays (MCBs), USA. Methods and Results: Crab, haemolymph, sediment and seawater samples were collected monthly from four sites in MCBs from February 2012 through October 2012 with environmental parameters recorded. The most-probablenumber (MPN) methodology was used to enumerate Vp and Vv with presumptive colonies and the presence of virulence markers confirmed using polymerase chain reaction (PCR). Results indicate that blue crabs contained both Vp and Vv at densities (7Á28 and 5Á43 log MPN g À1 , respectively) higher than those reported for bivalves. In addition, markers for clinically relevant strains of both species were detected in over 30% of samples. Haemolymph, sediment and seawater samples were also routinely positive for both species and clinically relevant strains, but generally at lower densities than found in crabs (4Á27, 3Á28, and 2Á39 log MPN g À1 per ml À1 Vp, and 4Á28, 2Á49 and 2Á38 log MPN g À1 per ml À1 Vv). Conclusions: Blue crabs concentrate Vp and Vv at levels greater than found in water or sediment. While changes in abundance associated with temperature are apparent, there is little evidence to support differences among sampling locations. Significance and Impact of the Study: These results highlight the potential for blue crab related vibriosis and the importance of proper handling, cooking and care of this popular seafood before consumption. IntroductionBlue crabs (Callinectes sapidus) exist along the western border of the Atlantic Ocean from the Canadian province, Nova Scotia down to Argentina (Reichmuth et al. 2009). They are of ecological and economic importance and require an estuarine environment such as the Chesapeake Bay and the Maryland Coastal Bays (MCBs) for growth.Ecologically, blue crabs perform many roles in the estuarine food web depending upon life stage (Reichmuth et al. 2009). Blue crabs are also a very popular delicacy in the US Gulf of Mexico and Atlantic coastal areas. In 2011, the Chesapeake Bay crab fishery had a total harvest of 67Á3 million pounds. According to the 2012 annual winter dredge survey completed by the Maryland Department of Natural Resources, the blue crab population had increased 66% to 764 million. This
Challenge studies with Mycobacterium marinum clearly demonstrate that a poor diet affects the progression and severity of mycobacteriosis in striped bass Morone saxatilis. Fish (n = 512 total, wt = 65 ± 15 g) were inoculated intraperitoneally with 10 4 colony-forming units (CFU) g -1 body weigth (BW) or a physiological saline solution (controls) and evaluated for 8 mo. Inoculated fish fed a low-ration diet (0.15% BW d -1 ) developed a severe, systemic infection characterized by a high bacterial load (>10 8 CFU g -1 spleen) and poor granuloma formation, which commonly progressed to mortality by 6 wk. In contrast, inoculated fish fed an adequate ration diet (1% BW d -1 ) developed classic granulomatous inflammation of reduced severity and total body energy similar to that found in uninoculated controls (p > 0.05). After 4 wk, fish fed adequate rations maintained an equilibrium state throughout the study period, even though 10 6 CFU g -1 spleen mycobacteria were consistently cultured. In a second study, reactivation of an acute inflammatory state was demonstrated by placing previously infected fish on reducing diets (0.073% BW d -1). In both studies, the energetic demand of this disease was only appreciable when associated with active, severe, inflammatory states. To our knowledge, this study is the first to demonstrate the interaction of diet and mycobacteriosis in fish.
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