Indicator Microorganisms

This chapter covers a variety of organisms that are routinely monitored for in environmental samples such as food or water, and whose presence indicates the potential for pathogenic microorganisms. Following a discussion of indicator organisms including the criteria for an "ideal" indicator, specific indicator organisms are discussed with respect to their advantages and deficiencies as indicators of pathogenic microbes. A section on total coliforms includes a discussion of the most probable number (MPN) test; the membrane filter (MF) test; and the presence-absence (P-A) test. Other indicators discussed include: fecal coliforms and E. coli; fecal streptococci; Clostridium perfringens; Bacteroides and Bifidobacterium; heterotrophic plate count (HPC); and bacteriophages. Finally, standards and criteria for indicators are presented.