ABR

Spatial patterns of ABR in marine predators

Antibiotic resistance (ABR) in bacteria is a growing problem in both human and veterinary medicine. Several recent studies have documented the presence of ABR in human, livestock, and domestic animal cases; however, limited research is available on the presence of ABR in wildlife species. To date, no study has determined the prevalence of ABR in marine top-level predatory fishes. A cross-sectional study was conducted to determine the prevalence of ABR in marine predatory fishes. The specific objectives of this study were to 1) determine if ABR bacteria were present in marine predatory fishes, and 2) determine if ABR patterns in marine predatory fishes were spatially explicit. Seven species of sharks and a single teleost species were opportunistically sampled from six different study sites. A total of 134 viable bacteria samples were isolated from the cloacal swabs of predatory fishes. The prevalence of ABR for each study location were: 1) Belize: 75%, 2) Florida Keys: 86.5%, 3) Coastal Louisiana: 62%, 4) Louisiana Offshore-sharks: 52%, 5) Louisiana Offshore-redfish: 91.7%, and 6) Massachusetts: 87.5%. Inter-specific comparisons between redfish and sharks from Louisiana offshore waters demonstrated a significantly higher ABR prevalence in redfish, which may be due to the older age of the population. The findings of this study confirmed the presence of antibiotic resistance in marine predatory fishes from multiple taxa and multiple geographic locations. Widespread use of antibiotics in human and veterinary medicine and anthropogenic influences on the environment may have led to ABR spillover into the marine environment. Future studies to determine the specific biogeography and ecology of ABR in marine predators should be pursued.

· Resistance was found in all six geographic locations and for all species of sharks and a teleost fish and for all non-synthetic and synthetic drugs tested in at least a portion of the isolates.

· Resistance was found The areas studied included those with large human interaction and development, such as the Belize study site in addition to those with very little human interaction, such as the Florida Keys study site.

· That resistance was found in all locations, for all species, and for every drug tested, goes beyond the expectations of the original hypothesis.

· Greater exploration of additional species, habitats, and reasons for such resistant strains of microbes is necessary.

· Spatial patterns were difficult to discern due to overlapping confidence intervals, but all areas should be considered possible reservoirs for ABR.

· A more complete understanding of the role biophysical geography plays in the dispersal and promotion of ABR in the wild is necessary.

· Differences in redfish and spinner shark ABR may be attributable to age, but suggests that multiple species should be used as sentinels within a region.

The Kirby-Bauer Disc Diffusion method was used to test bacterial cultures isolated from cloacal swabs of wild sharks and red fish from six distinct geographic locations from Belize to New England. Shown here is an image of a Psuedomonus culture 24 hours after inoculation. The white discs are antibiotic drugs. The amount of resistance to each different drug type is quantified by measuring the distance from the disc to the edge of the bacteria (zone of inhibition). In this example, the clear areas are the areas of inhibition where the drug discs hindered bacterial growth. The green areas are where living Psuedomonus colonies have grown on the plate.

The nurse shark, Ginglymostoma cirratum, is a common species in both the Florida Keys and coastal Belize (two sites in this study). Nurse sharks were sampled in the Dry Tortugas, Florida and in the Hol Chan Marine Reserve in northern Belize.

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