APPLED MICROBIOLOGY, Jan. 1975, p. 130-131 Copyright 0 1975 American Society for Microbiology
Vol. 29, No. 1 Printed in U.S.A.
Evaluation of a Medium for the Rapid Recovery of Escherichia coli from Shellfish' WALLACE H. ANDREWS, CECILE D. DIGGS, AND CLYDE R. WILSON Division of Microbiology, Food and Drug Administration, Washington, D.C. 20204 Received for publication 25 October 1974
A medium (A-1) which shortens the time necessary to identify and enumerate Escherichia coli found in estuarine water was evaluated for use for recovery of E. coli found in shellfish. Productivity of E. coli by this medium was comparable to that of the lengthier American Public Health Association method, and the occurrence of false positives was substantially reduced.
At the beginning of this century when the detection and enumeration of pathogenic bacteria in water was a time-consuming, laborious task, the concept of utilizing indicator organisms to infer the presence or absence of these pathogens was adopted. The methodology which subsequently evolved was designed to quantitate levels of total coliform and fecal coliform organisms. Eventually coliform types were specified, and the results of numerous studies were published reporting on the relative significance of these indicator organisms as contrasted to the more specific Escherichia coli, Enterobacter aerogenes, and Klebsiella species. One of the limiting factors in using E. coli as an indicator organism is the length of time required for complete identification. A medium or test designed to shorten this period could conceivably render E. coli more acceptable as an indicator. It is neither the intent nor within the scope of this note, however, to further complicate an already controversial area by advocating any one organism as the preferred indicator. Rather, this note reports on the performance of a medium, originally formulated for the rapid recovery of E. coli from estuarine water, for use with shellfish. The medium, designated medium A-1 (3), was reported to recover numbers of E. coli organisms from estuarine waters comparable to those obtained by the lengthier American Public Health Association (APHA) method (1). During a 24-month interval subsequent to that report, this medium was evaluated with the Eastern oyster (Crassostrea virginica) and the quahaug (Mercenaria mercenaria). Field units of the Food and Drug Administration Shellfish Sanitation Branch collected quahaug I Address reprint requests to: Helen L. Reynolds, Technical Editor, FDA Bureau of Foods-HFF-38, 200 C St., S.W., Washington, D.C. 20204.
130
samples from Narragansett Bay, Rhode Island, and oyster samples from several estuaries of the Gulf Coast, Rhode Island, Connecticut, and New York. Water depth in the estuaries varied from 1 to 50 feet (30.5 to 1,524 cm). Water temperatures ranged from 2 to 31 C, and salinities were from
Vol. 29, No. 1 Printed in U.S.A.
Evaluation of a Medium for the Rapid Recovery of Escherichia coli from Shellfish' WALLACE H. ANDREWS, CECILE D. DIGGS, AND CLYDE R. WILSON Division of Microbiology, Food and Drug Administration, Washington, D.C. 20204 Received for publication 25 October 1974
A medium (A-1) which shortens the time necessary to identify and enumerate Escherichia coli found in estuarine water was evaluated for use for recovery of E. coli found in shellfish. Productivity of E. coli by this medium was comparable to that of the lengthier American Public Health Association method, and the occurrence of false positives was substantially reduced.
At the beginning of this century when the detection and enumeration of pathogenic bacteria in water was a time-consuming, laborious task, the concept of utilizing indicator organisms to infer the presence or absence of these pathogens was adopted. The methodology which subsequently evolved was designed to quantitate levels of total coliform and fecal coliform organisms. Eventually coliform types were specified, and the results of numerous studies were published reporting on the relative significance of these indicator organisms as contrasted to the more specific Escherichia coli, Enterobacter aerogenes, and Klebsiella species. One of the limiting factors in using E. coli as an indicator organism is the length of time required for complete identification. A medium or test designed to shorten this period could conceivably render E. coli more acceptable as an indicator. It is neither the intent nor within the scope of this note, however, to further complicate an already controversial area by advocating any one organism as the preferred indicator. Rather, this note reports on the performance of a medium, originally formulated for the rapid recovery of E. coli from estuarine water, for use with shellfish. The medium, designated medium A-1 (3), was reported to recover numbers of E. coli organisms from estuarine waters comparable to those obtained by the lengthier American Public Health Association (APHA) method (1). During a 24-month interval subsequent to that report, this medium was evaluated with the Eastern oyster (Crassostrea virginica) and the quahaug (Mercenaria mercenaria). Field units of the Food and Drug Administration Shellfish Sanitation Branch collected quahaug I Address reprint requests to: Helen L. Reynolds, Technical Editor, FDA Bureau of Foods-HFF-38, 200 C St., S.W., Washington, D.C. 20204.
130
samples from Narragansett Bay, Rhode Island, and oyster samples from several estuaries of the Gulf Coast, Rhode Island, Connecticut, and New York. Water depth in the estuaries varied from 1 to 50 feet (30.5 to 1,524 cm). Water temperatures ranged from 2 to 31 C, and salinities were from
