Concentration of enteric viruses from water with lettuce extract.

Applied microbiology 11/1974; 28(4):717-9.
Source: PubMed

ABSTRACT A method for recovering enteroviruses, adenovirus, and reovirus from water with lettuce extract is described. Lettuce extract at pH 8.5 was added to the sample and the pH was reduced stepwise with hydrochloric acid to 4.0 to 4.5. The flocculent lettuce-extract particles, and adsorbed virus, were readily removed from solution by low-speed centrifugation. Electron microscopy suggests that, under conditions suitable for adsorption, virus particles are coated with the lettuce-extract colloid.

  • 10/1975; 8(4):219–220. DOI:10.1016/S0315-5463(75)73814-2
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    ABSTRACT: Salad vegetables exposed to fecal contamination may cause outbreaks of hepatitis or gastro-enteritis if they are eaten raw. A procedure, based on elution with phosphate-buffered saline and concentration by filtration through membrane filters, was developed for the recovery of enteric viruses from salad leaves. The method was evaluated using lettuce leaves inoculated with hepatitis A virus (HAV), poliovirus, and MS2 bacteriophage. In addition, this method was validated by an intra-laboratory study using leaves of various salad vegetables inoculated with MS2 phage. The French standard NF V 03-110 was used to establish the general principle and the technical protocol of the validation procedure. Linear regression models describing the quantitative reactions were good fits to data in the whole range of viral concentrations tested, which was from about 1 to 4 log plaque-forming units (PFU) per 25 g of lettuce. The fractions of inoculated viruses recovered were estimated to be about 64% for HAV, 18% for poliovirus, and 29% for MS2. No significant effect of the food matrix was found using various types of salad vegetable (butter lettuce, iceberg lettuce, romaine lettuce, witloof chicory, curly endive, corn salad, rocket and watercress). Moreover, the variance of the results was constant for all levels of virus contamination within the experimental range. Intermediate reproducibility experiments were also performed to allow calculation of the uncertainty factor, which was found to be 0.58 log PFU/25 g. When used in association with phage enumeration, this validated procedure is rapid enough to be used for screening salad vegetables for evaluation of the efficacy of processes for control of pathogenic microorganisms on such foods.
    International Journal of Food Microbiology 05/2006; 108(2):164-71. DOI:10.1016/j.ijfoodmicro.2005.11.007 · 3.16 Impact Factor


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