ASSOCIATION OF MULTIPLE-ANTIBIOTIC-RESISTANCE PROFILES WITH POINT ANDNONPOINT SOURCES OF ESCHERICHIA-COLI IN APALACHICOLA BAY

A total of 765 Escherichia coli isolates from point and nonpoint sourc es were collected from the Apalachicola National Estuarine Research Re serve, and their multiple-antibiotic-resistance (MAR) profiles were de termined with 10 antibiotics, E. coli isolates from point sources show ed significantly greater resistance (P < 0.05) to antibiotics and high er MAR indices than isolates from nonpoint sources. Specifically, 65 d ifferent resistance patterns were observed among point source isolates , compared to 32 among nonpoint source isolates, Examples of this cont rast in MAR profiles included percentages of isolates with resistance to chlortetracycline-sulfathiazole of 33.7% and to chlortetracycline-p enicillin G-sulfathiazole of 14.5% for point source isolates versus 15 .4 and 1.7%, respectively, for nonpoint source isolates, MAR profile h omology, based on coefficient similarity, showed that isolates from po int sources were markedly more diverse than isolates from nonpoint sou rces, Seven clusters were observed among point source isolates, with a coefficient value of approximately 1.8. In contrast, only four cluste rs were observed among nonpoint source isolates, Covariance matrices o f data displayed six very distinct foci representing nonpoint source E . coli isolates, Importantly, E. coli isolates obtained directly from human and animal feces also clustered among point and nonpoint sources , respectively, We conclude that E, coli MAR profiles were associated with point and nonpoint sources of pollution within Apalachicola Ray a nd that this method may be useful in facilitating management of other estuaries.