Survival and viability of nonculturableEscherichia coli andVibrio cholerae in the estuarine and marine environment
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Plating methods for estimating survival of indicator organisms, such asEscherichia coli, and water-borne pathogens includingVibrio cholerae, have severe limitations when used to estimate viable populations of these organisms in the aquatic environment. By combining the methods of immunofluorescent microscopy, acridine orange direct counting, and direct viable counting, with culture methods such as indirect enumeration by most probable number (MPN) estimation and direct plating, it was shown that bothE. coli andV. cholerae undergo a “nonrecoverable” stage of existence, but remain viable. Following 2-week incubations in saltwater (5–25%o NaCl) microcosms, total counts, measured by direct microscopic examination of fluorescent antibody and acridine orange stained cells, remained unchanged, whereas MPN estimates and plate counts exhibited rapid decline. Results of direct viable counting, a procedure permitting estimate of substrate-responsive viable cells by microscopic examination, revealed that a significant proportion of the nonculturable cells were, indeed, viable. Thus, survival of pathogens in the aquatic environment must be re-assessed. The “die-off” or “decay” concept may not be completely valid. Furthermore, the usefulness of the coliform and fecal coliform indices for evaluating water quality for public health purposes may be seriously compromised, in the light of the finding reported here.
KeywordsSaltwater Fecal Coliform Acridine Orange Viable Population Much Probable Number
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- 1.American Public Health Association (1980) Standard methods for the examination of water and wastewater, 15th ed. American Public Health Association, Inc., Washington, DCGoogle Scholar
- 2.Andre DA, Weiser HH, Malaney GW (1967) Survival of bacterial enteric pathogens in farm pond water. J Am Water Works Assoc 59:503–508Google Scholar
- 6.Bordner R, Winter J (eds) (1978) Microbiological methods for monitoring the environment. EPA 600/8-78-017, US Environmental Protection Agency, CincinnatiGoogle Scholar
- 7.Cherry WB, Goldman M, Carski TR (1960) Fluorescent antibody techniques in the diagnosis of communicable diseases. US Department of Health, Education and Welfare. Public Health Service, Bureau of State Services, Communicable Diseases Center, Atlanta, p 32Google Scholar
- 9.Colwell RR, Kaper J (1977)Vibrio species as bacterial indicators of potential health hazards associated with water. In: Hoadley AW, Dutka BJ (eds) Bacterial indicators/health hazards associated with water. ASTM STP 635, American Society for Testing and Materials, Philadelphia, pp 115–125Google Scholar
- 12.Daley RJ, Hobbie JE (1975) Direct counts of aquatic bacteria by a modified epi-fluorescent technique. Limnol Oceanogr 20:875–882Google Scholar
- 14.Francisco DE, Mah RA, Rabin AC (1973) Acridine orange epifluorescence technique for counting bacteria in natural waters. Trans Am Microscopical Soc 92:416–421Google Scholar
- 20.Reed WM, Dugan PR (1978) Distribution ofMethylomonas methanica andMethylosinus trichosporium in Cleveland Harbor as determined by an indirect fluorescent antibody-membrane filter technique. Appl Environ Microbiol 35:422–430Google Scholar
- 22.Singleton FL, Attwell RW, Jangi MS, Colwell RR (1981) Influence of salinity and organic nutrient concentration on survival and growth ofVibrio cholerae in aquatic microcosms. Appl Environ Microbiol 43:1080–1085Google Scholar
- 24.Ward BB, Perry MJ (1980) Immunofluorescent assay of the marine ammonium-oxidizing bacteriumNitrosococcus oceanus. Appl Environ Microbiol 39:913–918Google Scholar