Conditions affecting the Growth of Bacterium coli on Bile Salts Media. Enumeration of this Organism in Polluted Waters

Abstract

SUMlClARY:The growth of Bacterium coli on agar media containing bile salts is conditioned by a number of factors. The proportion of total cells able to grow on a medium not containing bile salts rapidly declines at temperatures of incubation above 43". On a medium containing bile salts and lactose a distinctly inhibitory effect is observed at 37'; with most strains this effect is still more pronounced a t 4 4 ' . Some brands of bile salts are appreciably more inhibitory than others. Inclusion of phosphate in a bile salts medium introduces a markedly inhibitory factor, the severity of which varies with the strain of organism; some strains are virtually unable to grow on such a rnediuni.When a culture of Bact. coli is suspended in water containing only small concentrations of inorganic salts an iticreasing proportion of the population becomes attenuated so that the cells are unable to grow on bile salts lactose agar at 44'. An occasional strain may also exhibit sensitiveness to the presence of neutral red. This attenuating effect may be largely decreased if, before the inoculum is mixed with the bile salts and agar, it is subjected t o a short period of incubation with lactose broth. This treatment has been made the basis of a technique for obtaining a colony count of Bact. coli which is applicable t o polluted waters. (1939). Disadvantages of the method are the large quantity of medium required and the large error involved in the computation of the most probable number. Thus Halvorson & Ziegler (1933) calculated that, with five tubes of medium to each dilution, the count obtained will be between 70% below and Z60y0 above the true value.Enumeration of this organism provides a simple method of following the eff'ect of different treatments of sewage on the numbers of faecal bacteria discharged into a river and of the rate a t which these numbers decrease as the organisms are carried downstream. A colony count of Bact. coli would introduce into sanitary surveys of this character a welcome improvement in accuracy. Clegg & Sherwood (1947) introduced a roll-tube method of counting faecal coli in shellfish in which inocula were mixed with a modified MacConkey agar and the tubes were incubated a t 44". Preliminary tests showed, however, that the ability of cells of Bact. coli to form colonies on bile salts lactose agar

The Effect of Environmental Conditions on the Viability and Growth of Bacteria Damaged by Phenols

“…These findings had suggested that normal nutrient broth contained substances which were inimical to the survival (or revival) of such damaged cells, though not to normal cells. In this connection Allen and his co-workers (Allen, Pasley & Pierce, 1952; Allen, Pierce t Smith, 1953; Childs & Allen, 1953) obtained higher counts of Escherichia coli and Streptococcus faecalis when cells from polluted water were resuscitated in nutrient broth prior to transfer to inhibitory selective media. These workers also showed that counts on bile salt media from suspensions of E .…”

Comparison of the Effects of Liquid Medium Repair and the Incorporation of Catalase in MacConkey Type Media on the Recovery of Enterobacteriaceae Sublethally Stressed by Freezing

“…incubating the impaired cells in a rich medium at room temperature for 5 2 h before plating out on, or enriching in, selective media (Allen et al 1952;Mossel & Ratto 1970). incubating the impaired cells in a rich medium at room temperature for 5 2 h before plating out on, or enriching in, selective media (Allen et al 1952;Mossel & Ratto 1970).…”

Introduction and prospective

“…In most instances these effects are so serious that populations released from such foods can only be inoculated into or onto selective media after a revitalization treatment known as resuscitation (Allen et al, 1952) has been carried out.…”