Antibiotic resistant bacteria in Chesapeake Bay

Abstract

Water and shellfish samples were collected in Chesapeake Bay during February and March 1975, for bacteriological analyses, which included enumeration and identification of coliform bacteria resistant to multiple antibioties. Water samples were analyzed using eosin-methylene blue (EMB) agar supplemented with antibiotics. Shellfish samples were analyzed following accepted methods for examination of shellfish for coliforms and fecal coliforms. Pure cultures were isolated and evaluated for multiple drug resistance patterns using the antibiotic disk procedure to determine susceptibility. A total of 479 multiple resistant organisms was isolated. Of these, 34 were randomly picked and identified. From a compilation of the data for all the sampling sites, a trend was noted, indicating a threefold or more increase in the number of antibiotic resistant coliforms, extending up the Bay from the Chesapeake Bay Bridge north to Baltimore Harbor. The increase in number of antibiotic resistant bacteria in the vicinity of a populated area such as Baltimore supports the hypothesis that sewage effluents have a detectable influence on the water quality of Chesapeake Bay, as measured by the presence of antibiotic resistant coliform bacteria.