Isolation of faecal coliform bacteria from the American alligator (Alligator mississippiensis)

To determine whether American alligators (Alligator mississippiensis) are an unrecognized poikilothermic source of faecal coliform and/or potential pathogenic bacteria in South Carolina's coastal waters.

Bacteria from the cloaca of American alligators, as well as bacteria from surface water samples from their aquatic habitat, were isolated and identified. The predominant enteric bacteria identified from alligator samples using biochemical tests included Aeromonas hydrophila, Citrobacter braakii, Edwardsiella tarda, Escherichia coli, Enterobacter cloacae, Plesiomonas shigelloides and putative Salmonella, and these were similar to bacteria isolated from the surface waters in which the alligators inhabited. Based on most-probable-number enumeration estimates from captive alligator faeces, faecal coliform bacteria numbered 8.0x10(9) g(-1) (wet weight) of alligator faecal material, a much higher concentration than many other documented endothermic animal sources.

A prevalence of enteric bacteria, both faecal coliforms and potential pathogens, was observed in American alligators. The high faecal coliform bacterial density of alligator faeces may suggest that alligators are a potential source of bacterial contamination in South Carolina coastal waters.

These findings help to increase our understanding of faecal coliform and potential pathogenic bacteria from poikilothermic reptilian sources, as there is the potential for these sources to raise bacterial water quality levels above regulatory thresholds.