Methodology for enumeration of coliphages in foods

Applied and Environmental Microbiology (Impact Factor: 3.67). 06/1986; 51(5):956-62.
Source: PubMed


The effects of eluent composition, pH, and chaotropic agents on the recovery of T2, MS2, and indigenous coliphages from various foods were investigated. Additionally, methods of sample suspension and clarification were evaluated for coliphage recovery and application to various foods. Clarified sample suspensions were assayed for coliphages with a modified agar layer technique and appropriate Escherichia coli hosts. Centrifugation and polypropylene mesh filtration were more rapid and effective than glass wool filtration for clarification of sample suspensions and subsequent recovery of coliphages. Blending, stomaching, and shaking procedures were generally comparable for sample liquefaction and release of coliphages from foods. Complex basal eluents, EC medium and 1% casein, were generally more effective than a less complex eluent, phosphate buffer, for elution of coliphages from foods. For most foods, incorporation of sodium chloride or chaotropic agents, i.e., sodium trichloroacetate, urea, Tween 80, Triton X-100, and sodium nitrate, into basal eluents did not enhance recovery of coliphages. Indigenous coliphage recovery was not affected by sample suspension pH over a range of 6.0 to 9.0. With an optimal procedure, i.e., EC medium eluent, blending, and centrifugation, the recovery of T2 and MS2 ranged from 48 to 81% and from 58 to 100%, respectively, depending on the food type.

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    • "As a consequence, bacteriophage infection can lead to the destruction of the entire colony[18,20,22,23]. Bacteriophages are ubiquitous in nature and can be isolated from soil, water[21]and foods such as meat and meat products, dairy products and vegetables2425262728. Over the last year, the FDA/USA approved a preparation of bacteriophages (LISTEX P100) to combat the presence of L. monocytogenes directly in foods293031. "

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    • "Initial concentrations of MS2 phage in the range of 10 4 –10 5 plaque-forming units per milliliter (PFU/ mL) suspended in 2 mL 0.1 M bicarbonate buffer were filtered through the nAg–PSf and control PSf membranes. Virus concentrations were assayed using an agar-overlay technique (Kennedy et al., 1986). Briefly, 100 mL aliquots of influent or filtrate were serially diluted in 900 mL bicarbonate buffer, and incubated with 100 mL stationary phase MS2 host E. coli (ATCC 15597) for 10 min. "
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    ABSTRACT: Biofouling and virus penetration are two significant obstacles in water treatment membrane filtration. Biofouling reduces membrane permeability, increases energy costs, and decreases the lifetime of membranes. In order to effectively remove viruses, nanofiltration or reverse osmosis (both high energy filtration schemes) must be used. Thus, there is an urgent demand for low pressure membranes with anti-biofouling and antiviral properties. The antibacterial properties of silver are well known, and silver nanoparticles (nAg) are now incorporated into a wide variety of consumer products for microbial control. In this study, nAg incorporated into polysulfone ultrafiltration membranes (nAg-PSf) exhibited antimicrobial properties towards a variety of bacteria, including Escherichia coli K12 and Pseudomonas mendocina KR1, and the MS2 bacteriophage. Nanosilver incorporation also increased membrane hydrophilicity, reducing the potential for other types of membrane fouling. XPS analysis indicated a significant loss of silver from the membrane surface after a relatively short filtration period (0.4 L/cm2) even though ICP analysis of digested membrane material showed that 90% of the added silver remained in the membrane. This silver loss resulted in a significant loss of antibacterial and antiviral activity. Thus, successful fabrication of nAg-impregnated membranes needs to allow for the release of sufficient silver ions for microbial control while preventing a rapid depletion of silver.
    Full-text · Article · Dec 2008 · Water Research
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