Comparison of selective media for assay of coliphages in sewage effluent and lake water

Abstract

Selective media, including EC medium, gram-negative broth, nutrient broth (with 0.05% sodium deoxycholate), and lactose broth (with 0.05% sodium deoxycholate), as well as nonselective nutrient and lactose broths, were compared for the enumeration of coliphages by the agar layer method from activated-sludge effluent and eutrophic-lake water from a lake receiving treated sewage effluent. Samples were plated directly or after chloroform treatment with Escherichia coli B, E. coli C, or a mixed host of both E. coli B and C. With the exception of gram-negative broth, direct assays of all samples with the selective media generally resulted in significantly higher (P < 0.05) recoveries of coliphages than did assays of chloroform-treated samples with nutrient broth medium regardless of the host used. In addition, chloroform pretreatment resulted in decreased recovery of coliphages with each selective medium in most analyses. The highest recoveries of coliphages from all samples with each host, except lake water with E. coli C, were obtained by direct assay on EC medium. The selectivity of the EC and gram-negative media resulted in suppression of bacterial interference on direct assay plates comparable to that observed in nutrient agar medium with chloroform-treated samples. The use of certain selective media for the direct assay of environmental materials for coliphage may enhance the recovery of coliphages and obviate bacterial decontamination procedures.

Bacteriophages as indicators of enteric viruses and public health risk in groundwaters

“…The use of direct pour plate assay methods for phage enumerations generally requires a number of steps to reduce or suppress the growth of naturally occurring micro-organisms. Incorporation of antibiotics or decontamination with chloroform (Osawa et al 1981a;Tartera and Jofre 1987), membrane filtration (Tartera and Jofre 1987) and selective media (Kennedy et al 1985) have been used for this purpose. The combined use of membrane filtration with incorporation of the antibiotic, nalidixic acid, has been used most commonly to increase overall assay selectivity.…”

Occurrence and densities of bacteriophages proposed as indicators and bacterial indicators in river waters from Europe and South America

“…The bacteriophages mentioned above have been detected in surface waters (Araujo et al . 1997; Simkova and Cervenka 1981; Kennedy et al . 1985; Kfir et al .…”

Application of direct plaque assay for detection and enumeration of bacteriophages of Bacteroides fragilis from contaminated-water samples

“…To eliminate the contaminating background flora, chemical treatment with chloroform was used, which produces a low rate of decontamination of the sample and a lower recovery of Bacteroides phages, although Tartera and Jofre (15) indicated a high resistance of these phages to chloroform. However, other authors have reported a decrease of the phage recovery after treatment of the samples with this chemical (8).…”