Counting, microbial

The category 1 samples that showed at least one log higher in ATP content than cultivable counts had more yeast-fimgi populations on tryptic soy agar (TSA) plates. Next predominant microbes were Gram-positive groups. About 46% of unclassified clean room samples showed at least one log higher in ATP content than cultivable counts. Microbial diversity of cultivable... 

Hospital steriliza tion is more limited in the availabiHty of steriliza tion methods and of packaging materials. Microbial invasion can occur particularly when articles are wrapped in traditional fabrics such as muslin (140-thread-count cotton). The expected shelf life of hospital-wrapped and sterilized articles is considered to be ca 21—30 days when a double-wrapping technique is used. Double-wrapping requires two successive wraps, each having a layer or layers of an approved packaging material. 

Propylene Oxide. Propylene oxide [75-56-9] (qv), C H O, is a higher homologue of ethylene oxide that boils at 35°C. Propylene oxide is not as germicidaHy active as ethylene oxide (291), but has one distinct advantage it hydrolyzes to produce nontoxic propylene glycol (292), allowing use for treating foods. Three hours at 37°C reduced the microbial count of cocoa powder by 50—70% and molds by 90—99% (293). Powdered cosmetics and toiletries are treated with 1—2% of Hquid propylene oxide in sealed containers, and the temperature is raised to cause vaporization and increased activity (294). 

Viable count Measurement of the concentration of live cells in a microbial population. 

For food and pharmaceutical applications, the microbial count must be reduced to less than 10,000 viable cells per g exopolysaccharide. Treatment with propylene oxide gas has been used for reducing the number of viable cells in xanthan powders. The patented process involves propylene oxide treatment for 3 h in a tumbling reactor. There is an initial evacuation step before propylene oxide exposure. After treatment, evacuation and tumbling are alternated and if necessary the reactor is flushed with sterile nitrogen gas to reduce the residual propylene oxide level below the Food and Drug Administration permitted maximum (300 mg kg 1). The treated polysaccharide is then packaged aseptically. 

The microbial count of the mains water will be reflected in both softened and deionized water which m be prepared from it. 

Softened water is often used for washing containers before filling with liquid or semi-solid preparations and for cooling systems. Unless precautions are taken, the microbial count in a cooling system or jacketed vessel will rise rapidly and if faults develop in the cooling plates or vessel wall, contamination of the product may occur. 

The use of natural products with a high non-pathogenic microbial count is possible if a sterilization stage is included either before or during the manufacturing process. 

Packaging materials which have a smooth, impervious surface, free fi cm crevices or interstices, such as cellulose acetate, polyethylene, polypropylene, poly vinylchloride, and metal foils and laminates, all have a low surface microbial count. Cardboard and paperboard, unless treated, carry mould spores of Cladosporium spp., Aspergillus spp. md Penicillium spp. and bacteria such 2 Bacillus spp. sn.dMicrococcus spp. 

Recognizing these problems, UK food regulatory authorities have generally abandoned the use of quantitative microbial counts as enforceable standards of food quality. Despite this, the European Pharmacopoeia has introduced both quantitative and qualitative mierobial standards for non-sterile medicines, which might become enforceable in some member states. It prescribes varying maximum total microbial levels and exclusions of particular species according the routes of administration. The British Pharmacopoeia has now ineluded these tests, but suggest they should be used... 

Microbial limits. Carry out the test according to the general procedure <61 >. The total count does not exceed 100 microorganisms per gram, and tests for Staphylococcus aureus, and Pseudomonas aeruginosa, are negative. 

The restricted shelf life of liquid milk continues to be a problem that is often more influenced by the type of milk being sold rather than the pasteurisation technique. The shelf life of processed milk is determined primarily by the quality of the raw milk from the dairy herd. Increasing cell counts in the milk and a higher concentration of free fatty acids, contribute to rancidity in both liquid milk and milk products. Janzen (1972) reported that the 0-14 day shelf life of pasteurised milk is influenced by the somatic cell concentration in the raw milk and found that after 14 days any observed changes in the flavour and stability of the milk were attributable to microbial activity during storage. 

Historically, measurement of the microbial biomass has been a tedious, time-consuming occupation involving staining and direct counting or use of culture media and enumeration of individual microbial communities. However, in the last 20 years, a suite of methods have been developed for more rapid assessment of the microbial biomass. These include the substrate-induced respiration method (Anderson and Domsch 1978), the chloroform fumigation-incubation method (Jenkinson and... 

Minimal effects on intestinal flora were seen with rifaximin administration [9, 35]. In an early study, performed on healthy volunteers who received a short-term (5 days) rifaximin treatment, the observed changes in bowel flora returned to baseline levels within 1-2 weeks [9]. In a recent investigation fecal samples of patients with ulcerative colitis given three 10 day courses of the antibiotic were cultured and the different microbial species quantitated. Despite the high dose (i.e. 1800 mg daily) of rifaximin used there was only a minor change in bacterial counts which reverted back to pre-treatment values during the washout period [35]. It appears therefore that administration of this antibiotic does not disrupt intestinal microbial ecology. 

Microbial contamination, especially by salmonellas, is a risk when sprouts are produced commercially for human consumption. For recombinant protein production, seeds can be washed with water and surface-sterilized using hypochlorite solution. Sprouts can also be surface-sterilized during sprouting, by the addition of mild hypochlorite solution directly into the growth medium. Eventually, the hypochlorite is diluted out with pure water or growth medium. In our experiment on plate count agar [28], the sprouts showed no bacterial growth after sterilization with 1% sodium hypochlorite. 

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