A Comparison of the Membrane Filter with the Most Probable Number Method for Coliform Determinations from Several Waters

Evaluation of recovery methods to detect faecal streptococci in polluted waters

“…These results disagree with those of other studies (Saleh 1980 8 ;Volterra et al 1985), which suggested that the MF technique was more ef®cient (gave higher numbers) for faecal streptococci counts than the MPN procedure. Previous studies have also reported a lower sensitivity of the MF technique in recovering coliforms when compared with the MPN procedure (Shipe and Cameron 1954;McFeters et al 1982;Jacobs et al 1986); on the other hand, Dutka and Tobin (1976), Janardan et al (1977) and Massa et al (1989) found that the MF technique was more ef®cient (gave higher numbers) for coliform counts than the MPN procedure. There are several possible explanations for these discrepancies, the foremost being the different principles on which the two techniques are based, i.e.…”

Influence of diluents, media, and membrane filters on detection fo injured waterborne coliform bacteria

“…Such debilitated organisms are often unable to grow on selective media (27), but can regain that capability through a resuscitation process (1,3,7,9,22,29) under nonrestrictive conditions. The concept of sublethal injury was first associated with the suppression of waterborne indicator bacteria when it was noted that coliform enumeration data from waters containing toxic wastes or chlorine were consistently higher by the multiple tube fermentation-most-probable-number method than by the membrane filtration procedure (6,9,22,29,35). More than 90% of the indicator bacteria present may become injured when exposed to natural waters for less than 1 week (3,4).…”

THE FAILURE OF PHENOL TREATED ESCHERICHIA COLI TO GROW ON MEMBRANE FILTERS

“…Damaged cells may be expected to occur in water as a result of attrition or antiseptic action and it is possible that such cells may behave similarly to those damaged by phenol. This may account for the relatively poor performance of membrane filters reported by some workers (Shipe & Fields, 1954;shipe & Cameron, 1954).…”

“…However, Shipe & Fields (1954) reported membrane counts of Escherichia coli which were consistently lower than agar plate counts, both with untreated suspensions and with cells exposed to copper and zinc sulphates. Similarly Shipe & Cameron (1954) obtained lower counts with membrane filters than with the 'most probable number' method from waters which contained toxic substances. Membrane filter counts which were slightly lower than those on agar plates were reported by Portner, Mayo & Kaye (1954) with untreated bacteria, but with bacteria exposed to the action of formaldehyde these workers found higher counts on the membrane filters.…”