Comparison of Three International Methods with APHA Method for Enumeration of Escherichia coli in Estuarine Waters and Shellfish.

Three international methods were evaluated for enumerating Escherichia coli in estuarine waters, oysters ( Crassostrea virginica ), mussels ( Mytilus edilus ) and clams ( Mercenaria mercenaria ). Results of the French most probable number (MPN) method, a modification of the MacKenzie, Taylor and Gilbert (1948) method, were obtained within 48 h and compared favorably with those obtained by the standard American Public Health Association (APHA) MPN procedure in all sample types. Results of the Australian Anderson and Baird-Parker plate count method, obtained within 24 h, were significantly lower than those obtained with the standard APHA procedure for all sample types. Results of the British roll tube method, a 24-h direct count method, compared favorably with the standard APHA procedure only for mussels and waters.