Viable counting

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

Wang et al. report the death kinetics of Bacillus stearothermophilus spores using wet, thermal sterilization. Twenty minutes at 110°C reduces the viable count by a factor of lO". The activation temperature, E/Rg, is 34,200 K. How long will it take to deactivate by a factor of lO ... 

Changes in the population of viable bacteria in an environment are determined by means of a viable count, and aplot of this count against time gives a dynamic picture of any pattern of change (see Fig. 11.1, curve A). The typical growth curve of a bacterial culture is constructed from data obtained in this w. The pattern of bacterial death in a lethal environment m be obtained by the same technique, when a death or mortality curve is obtained (Fig. 11.1, curve C). 

Inspection of the death curves obtained from viable count data had early ehcited the idea that because there was usually an approximate, and under some circumstances a quite excellent, linear relationship between the logarithm of the number of survivors and time, then the disinfection process was comparable to a unimolecular reaction. This imphed that the rate of killing was a function of the amount of one of the participants in the reaction only, i.e. in the case of the disinfection process the number of viable cells. From this observation there followed the notion that the principles of first-order... 

There is no doubt that the maximum information concerning the fate of a baeterial populahon is obtained by performing viable counts at selected hme intervals. Alternatively, the number of survivors expressed as the percentage remaining viable at the end of a given period of time may be determined by viable counts and this parameter is often used in assessing bactericidal activity. 

It will be recalled (sechon 1) that research on the time course of the disinfection process was carried out making extensive use of viable counts, and notions concerning the dynamics of the disinfechon process were gathered by these means. 

Tests should also be done in the presenee of organic matter (e.g. albumin) and in hard water. It is important to remember when performing viable counts that care must be taken to ensure that, at the moment of sampling, the disinfection process is immediately arrested by the use of a suitable neutralizer or ensuring inactivation by dilution (Table 11.4). Membrane filtration is an alternative procedure, the principle of whieh is that treated cells are retained on the filter whilst the disinfectant forms the filtrate. After washing in situ, the membrane is transferred to the surface of a solid (agar) reeoveiy medium and the eolonies that develop on the membrane are counted. 

In certain instances it will be necessary to subject data obtained firm viable counts to statistical analysis or, more sensibly, experiments should be designed so as to render them amenable to statistical treatment. 

The test organism may be placed on the skin, e.g. on the back of the hand, and the preparation to be evaluated placed on the same area. After a given time interval the area is swabbed with sterile cotton wool and the swab incubated in a suitable medium or washed in a suitable fluid, and viable counts are subsequently made. 

Potential chemical preservatives may be evaluated in the first place by the methods outlined above, especially by determining MIC values (section 3.6) or by viable counts (section 3.2). TheRW, CM andKS tests (sections 3.1.1 and 3.1.2) have no relevance in preservative evaluation. It will be recalled (section 2.5) that formula ingredients may reduce the efficiency of a preservative which has shown up well in conventional tests using culture media as the suspending fluid. 

BCG Cultures of live BCG cells in liquid or on solid media 1 Bacteria centrifuged from medium 2 Resuspension in stabilizer 3 Freeze-drying Viable count induction of sensitivity to tuberculin in guinea-pigs Exclusion of virulent mycobacteria absence of excessive dermal reactivity... 

The homogeneity determination of the bacteria in the materials is performed by viable count followed by statistical evaluation of the cormts of sub-samples from the same capsule solution and of total counts of different capsules of one batch. An example for the homogeneity determination for a batch of capsules containing Enterococcus faecium is also presented in (Janning et al. 1995). 

Viable cells Direct viable count Detection of viable cells by elongation 123... 

In a parallel test with water instead of disinfectant the colony forming units (cfu) of surviving bacteria are determined and the reduction in viable counts is calculated. 

Total viable count per gram Bacteria <10 Fungi <10... 

FIGURE 7. Effect of methyltins on total viable counts of natural populations from sediments in Boston Harbor (modified from Reference 68). Tin added as , CHsSnCRtMMT) , (CH3)2SnCl2(DMT) 0> (CH3)3SnCl(TMT)... 

The tests for microbial limits and recommendations for microbial quality criteria of raw materials, excipients, drug substances, and pharmaceutical products have been established in pharmacopoeial compendia for over 30 years. These tests are listed in the USP 24 Chapter (61) Microbial Limits Tests and in the Ph. Eur. 3rd ed.. Biological Tests 2.6.12 and 2.6.13, Microbial Contamination of Products Not Required to Comply with the Test for Sterility (total viable count, tests for specified microorganisms) and the JP XIII 30 Microbial Limit Test. 

Total viable counts (TVCs) were immediately carried out on duplicate controls with no biocide added. The slurries were incubated at 37 °C for 4 hours and TVCs were performed at that time point and at several points over the following 6 weeks. Re-inoculations were carried out after 3 weeks. The resulting bacterial numbers were recorded as colony forming units (cfu)/ml of slurry. 

TABLE 3.7 Effects on viable counts of contact with a cellulose acetate coating containing toluidine blue and rose bengal and exposed to light from a 25-W fluorescent lamp (adapted from Decraene et at., 2006)... 

Organism Light exposure time (h) % Reduction in viable count Logio reduction in viable count... 

Sensory. Sensory analysis is one of the oldest accepted methods forjudging seafood quality and freshness. Although fairly accurate, it unfortunately requires trained, experienced panelists to attain accuracy. Perez-Villarreal (( u evaluators experienced in sensory analysis of fish to judge freshness and quality. Results of the study showed sensory scores were better correlated with microbiological analyses, especially total viable counts, than with chemical analyses such as trimethylamine or enine nucleotide decomposition (6). 

These are areas where materials of low viable count are handled. The area should be constructed and used in such a way as to reduce the... 

Microbiological Investigation 1.1 Total aerobic viable count... 

Total aerobic viable count Establish in-house requirements... 

Water for injection used for other purposes (e.g., washing and rinsing product components and equipment) should be tested for pyrogens and aerobic viable count at least weekly. 

Microbiological Investigations Water for Injection 7.7 Viable count... 

Purge the outlet of the supply point for 5 min. Adjust to a flow volume of about 30 1/min. Pass the nitrogen through an air sampler provided with a 0.22 im filter. Sampling time is about 5 min. Perform the procedure twice. One filter should be incubated for anaerobic, the other for aerobic viable count. 

Test the water used for prewashing in ampule and vial washing machine for viable count. 

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