Evaluation of Recovery Methods to Detect Coliforms in Water

Abstract

Various recovery methods used to detect coliforms in water were evaluated by applying the membrane filter chamber technique. The membrane filter chambers, containing pure-culture suspensions of Escherichia coli or natural suspensions of raw sewage, were immersed in the stream environment. Samples were withdrawn from the chamber at regular time intervals and enumerated by several detection methods. In general, multiple-tube fermentation techniques gave better recovery than plating or membrane filtration procedures. The least efficient method of recovery resulted when using membrane filtration procedures, especially as the exposure period of the organisms to the stream environment increased. A 2-h enrichment on a rich, nonselective medium before exposure to selective media improved the recovery of fecal coliforms with membrane filtration techniques. Substantially enhanced recoveries of E. coli from pure-culture suspensions and of fecal coliforms from raw-sewage suspensions were observed when compared with recoveries obtained by direct primary exposure to selective media. Such an enrichment period appears to provide a nontoxic environment for the gradual adjustment and repair of injured cells.

The effects of nutrients on the survival of Escherichia coli in lake water

“…Flint (1987) showed that in the absence of other bacteria, i.e. in the absence of competitors, in sterile autoclaved river water E. coli could Discussion survive for up to 260 d, even at 2 5 T , without The factors which are considered most likely to any decline in numbers and without suffering affect the survival of non-indigenous bacteria in any of the apparent stress symptoms seen by others (Bissonnette et al 1975(Bissonnette et al , 1977Zaske et al 1980). As expected, the addition of a complex mixture of nutrients, in the form of synthetic sewage, to filtered-autoclaved lake water allowed the E. coli to increase in numbers in proportion to the amount of synthetic sewage added.…”

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

“…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). Injury is an important factor in underestimating numbers of waterbome indicator bacteria which may lead to inaccurate public health assessments.…”

“…In most studies, however, little attention has been given to injured bacteria. Selective media have likewise been reported as a factor that causes variable recovery efficiencies of indicator bacteria (4,11,12,18,21,32,34). Bacteria injured in water have been shown to be more sensitive to selective ingredients in various enumeration media (4,11) because of damage to the bacterial envelope (44).…”

“…Selective media have likewise been reported as a factor that causes variable recovery efficiencies of indicator bacteria (4,11,12,18,21,32,34). Bacteria injured in water have been shown to be more sensitive to selective ingredients in various enumeration media (4,11) because of damage to the bacterial envelope (44). This realization stimulated the successful development of resuscitation procedures and media for the improved enumeration of injured fecal coliforms, particularly in chlorinated wastewater effluents (3,4,19,25,38).…”

“…Bacteria injured in water have been shown to be more sensitive to selective ingredients in various enumeration media (4,11) because of damage to the bacterial envelope (44). This realization stimulated the successful development of resuscitation procedures and media for the improved enumeration of injured fecal coliforms, particularly in chlorinated wastewater effluents (3,4,19,25,38). A new section describing these methods, entitled 921), has been added to the 15th edition of Standard Methods for the Examination of Water and Wastewater (2).…”