Membrane Filter Technique for the Quantification of Stressed Fecal Coliforms in the Aquatic Environment

Abstract

A two-layer membrane filtration (MF) medium (injury-mitigating MF [IM-MF]) and a procedure for the enumeration of injured fecal coliforms are described. These procedures included the addition of glycerol and acetate plus reducing agents to both layers of a two-layer medium and rinsing of the filter with a rich resuscitation medium. Some changes in incubation time and temperatures were used. This method was compared with the multiple-tube fermentation most-probable-number procedure and the one-step M-FC agar-membrane filter method (direct M-FC) in terms of fecal coliform recovery from various aquatic environments that cause bacterial injury. With chlorinated sewage effluents, results of the IM-MF technique were equal to or greater than the most probable number in 9 of 18 trials and were 1.3 to 19 times greater than the M-FC method. When sewage samples were chlorinated in the laboratory, fecal coliform counts with IM-MF equaled or exceeded the most probable number in 7 of 15 trials and always exceeded the M-FC. M-FC was exceeded by IM-MF in 30 of 33 trials with clean mountain stream water. Fecal coliform bacteria that were exposed to low levels of an iodophore in the laboratory produced IM-MF counts 3 to 10 times greater than those with M-FC. A biochemical rationale for the formation of the IM-MF medium is discussed.

Effect of chlorine dioxide on selected membrane functions of Escherichia coli

“…Nor was respiratory damage a distinguishing feature when comparing the two populations of different sensitivity. Similar observations with chlorine have been noted by Haas & Englebrecht (1980) and by others (Stuart 1977;McFeters & Camper 1978). Also, the inhibition of respiration was reversible on the m-END0 recovery medium, as shown by the results at the lowest chlorine dioxide dose (Table 3).…”

Enumerating Injured Coliforms in Drinking Water

“…The problem of enumerating injured fecal coliform bacteria has been recog nized by a new section, " Stressed Organ isms" (section 920), in the 15th edition of Standard 2Meth0ds.~l Included in this section are various resuscitation techniques for fecal coliforms.13.16. [90][91][92] The authors recently compared the effectiveness of m-T7 agar with some of the proposed resuscitation techniques for the recovery of injured fecal coliforms from chlorinated sewage effluents. 99 Although a limited number of samples were examined, m-T7 agar preincubated at 37°C for 8 h before transfer to 44.5" C for an additional 12 h was superior for recovering verified fecal coliforms, compared with the resuscitation techniques tested.…”

Examination of Reactivation and Regrowth of Fecal Coliforms in Centrifuge Dewatered, Anaerobically Digested Sludges

“…Numerous researchers in the 1970s and 1980s have shown that under stress that can cause sub-lethal injury, some bacteria become non-culturable when growth is attempted using selective media and especially selective media specified in standard culturing methods. But if the media are amended or non-selective, culturability is greatly enhanced (Lin et al, 1976, Martin et al, 1976, Green et al, 1977, Stuart et al, 1977, LeChavallier et al, 1982, McFeters et al, 1982, McDonald et al, 1983, McFeters et al, 1986.…”

“…Researchers also have shown that changes in the media formulation or cultivation temperature regimes also can improve recoveries (Lin, 1976, Stuart et al, 1977, Green et al, 1977, LeChavallier et al, 1982, McFetters et al, 1982. For example, LeChavallier et al (1982) developed a medium, termed m-T7, that recovered about three times more coliforms from drinking water compared with the standard m-Endo agar.…”