Colony counting

IDF (1991). Enumeration of microorganisms colony count technique at 30 °C, Standard lOOB. 

Colony forming ability of the fetal liver cells was determined in the medium comprised 1.3% methylcellulose, 4.0 mM glutamine, 10 U/ml penicillin/-streptomycin, 100 U/ml GM-CSF, 100 U/ml IL-3, 50 ng/ml stem cell factor and 10 U/ml erythropoietin in IMDM. An aliquot of 10 cells was transferred to a 35 mm sterile plastic Petri dish and incubated at 37 C in a fully humidified atmosphere of 5% CO2 in air. The final colony count was performed on day 14 of culture, the colony types being defined by general morphological criteria. 

Mutagenic activity was recorded if at least one strain showed an increased reversion frequency in response to the test sample. (—) = no activity detected (-H) = at least 2x the number of colonies appeared as on a control plate situated in a ring around the sample disc (0) = an increased colony count was noted, but not 2x the control value, or not in a ring. 

Figure 19.4 Experimental procedure for the assessment of phototoxicity of formulations using the yeast assay. Formulations are spread on agar previously seeded by yeast cells. Photocytotoxicity is assessed by colonies counting after growth on complete medium, whereas genetically altered colonies (here gene conversion involving the t ptophan locus) are detected using selective growth medium (here tryptophan-free), [39].

After incubation, the spontaneous his - his + reversions found on background Plate C are subtracted from the colony count on Test Plate B. If a statistically significant number of colonies remain (i.e., net revertants ), the POM sample contains one or more chemicals that are promutagens. Sam-... 

After 15 min incubation, transfer 20 pi volume of the bacteria/test-product into the first well of the no. 96 plate and continue down the plate with 1 10 dilutions. Repeat for all bacteria test-products and control, and follow with colony counts. 

Part 1 colony count technique with confirmation of colonies (ISO/DIS 6888-1 1997)... 

Work Item D enumeration of Clostridium perfringens - colony count technique. 

Work Item F general guidance for enumeration of Bacillus cereus - colony count technique at 30°C. 

The lungs are rinsed in water to remove excess Bouin s solution, and the tumor colonies counted with the aid of a dissecting microscope (see Note 9). Murine lungs with greater than 300 colonies should be reported as >300 or too numerous to count. 

A table of values can be generated using a quasi-simulation from the above formula. (See Table 1.) If one uses the specification of 90.0-110.0% which are frequently used for potency assays of drugs products, and a method intermediate precision (as percentage ofRSD) of2.0 and 2.5%, the values obtained from Table 1 are five and seven samples, respectively. Coincidentally, these values approximate those mentioned in the U.S. v. Barr decision. It should be mentioned that this method of calculating the number of retests may not work well for some tests, such as LAL bioassays, which produce colony counts that are not normally distributed, but skewed. 

There were no qualitative differences in the species of anaerobic or aerobic bacteria identified among the dietary groups (data not shown). However, both viable colony counts and microscopic counts indicated that there were 2.5- to 3.8-fold more bacteria per gram of cecal contents in animals fed the pectin-containing or cereal-based diets than in cecal contents of animals fed the purified diet (Table III). No consistent diet-related changes were observed in numbers of aerobic organisms, and the increase in cecal bacteria density was limited to anaerobic organisms. All species of anaerobes identified and counted were elevated in pectin-fed and cereal-based diet-fed animals. 

MK-0911 prolonged survival and reduced colony counts in spleen and liver at a dose as low as 0.05 mg/kg of body weight/day in immunocompetent Balb/c Nu/+ mice infected with H. capsulatum (Graybill et al, 1998). In their athymyic Balb/c nu/nu counterparts, MK-0911 was effective but clearly less potent. Doses of 5 mg/kg per day were required. Finally, MK-0911 was active in a murine model of P. carinii pneumonia (Powles etal., 1998). 

Fig. 7. IC50 vs. LC50 values for HeLa cells treated with a series of platinum complexes. LC50 was determined by a colony-counting assay. /C50 was the platinum concentration at which EGFP expression was reduced to 50% of control.

Use the dilution factors and colony counts to determine the total number of viable cells (Trp+ plus Trp-) present per milliliter of undiluted culture in tubes 1 and 2. Assuming that all of the Trp+ cells are transformants and assuming that the total number of viable cells in tubes 2 through 6 is the same, calculate the efficiency of transformation in tubes 2 to 6. Interpret all your results in terms of the contents of each tube and your knowledge of the process of transformation. Which tubes served as controls for the experiment Explain. 

Example 2.6 A sample of water is analyzed for the cohform group using three sample portions 10 mL, 60 mL, and 600 mL. Each of these portions is hltered through hve hlter membranes using the membrane-hlter technique. The results of the colony counts are as follows 10-mL portions 6, 7, 5, 8, 6 60-mL portions 30, 32, 33, 31, 25 and 500-mL portions 350, 340, 360, 370, 340. What is the number of coliforms per 100 mL of the sample ... 

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