Isolation of ether-resistant enteroviruses from sewage: methodology

Experiments were conducted to determine whether polio type 1 (Mahoney and coxsackie A8 viruses adsorb onto cotton fibers of sewer swabs. Negative results were obtained. It has been shown that viruses may exist in sewage as free virus particles or as bound (adsorbed) virus particles. The sewer-swab method of sampling is superior because it filters out the bound virus over several days; when collected, it represents a catch (grab) sample at that particular time which may or may not contain free virus. A simple method for the preparation of sewage inocula for virus isolations is described which samples the bound virus fraction. Only ether-resistant viruses can be isolated, and an ultracentrifuge is not required. By this method, an isolation rate between 60 and 80% of positive sewer swabs can be achieved. Corresponding figures of 84 and 96% were achieved by concentration of sewer-swab eluates with an ultracentrifuge. Quantitative studies showed that the virus concentration in raw sewage can be as high as one infectious particle per 0.5 ml.