Serial dilution method

API Serial Dilution Method. The API serial dilution method is the most widely used method for the detection of microorganisms. Field test methods for estimating bacterial populations have been standardized. A standard method dealing with the dose-response (time-kill) testing for evaluating biocides has been established. Sampling methods are of special importance because effective sampling is essential to any successful analysis. 

Animal infectivity methods Some viruses do not cause recognizable effects in cell cultures but cause death in the whole animal. In such cases, quantification can only be done by some sort of titration in infected animals. The general procedure is to carry out a serial dilution of the unknown sample, generally at ten-fold dilutions, and samples of each dilution are injected into numbers of sensitive animals. After a suitable incubation period, the fraction of dead and live animals at each dilution is tabulated and an end point dilution is calculated. This is the dilution at which, for example, half of the injected animals die. Although such serial dilution methods are much more cumbersome and much less accurate than cell culture methods, they may be essential for the study of certain types of viruses. 

The compound 7-(4-chloro-benzyl)-2-(4-chloro-phenyl)-3,8a-dihydro-pyridazino[4,3-( ][l,3,4] thiadiazin-8-one 42 has been reported to be active against Bacillus Escherchia coli, Staphylococcus aureus, and Pseudomonas aeruginosa by a serial dilution method <2001IJB475>. Triazino-thiadiazines 24f, 25b, 25c, and 25f <2002IJH287> have been reported to be active against S. aureus-, sydnone derivatives of triazino-thiadiazine 24f <2002IJH287> are more reactive than coumarin derivatives. 

It is very important to select promptly the most effective antibiotic for successful therapy of infectious diseases, and wound and post-surgical infections. The duration of standard microbiology assays applied in clinical practice exceeds 3-5 days since preliminary isolation of the pathogen from the clinical sample is required. In the present study we optimized a rapid bio luminescent antibiotic susceptibility assay based on comparison of bacterial ATP concentrations (bioluminescent signals) in a control (aliquot of the sample, free of the antibiotic) and probe (aliquot of the sample, supplied with antibiotic examined) after short-time incubation. For validation of the proposed assay, bacteria strains isolated from clinical samples were analyzed in parallel by the Bioluminescent Assay and Standard Microbiology Assay - Disk Method or Serial Dilutions Method. 

Standard Microbiology Assay of antibiotic susceptibility. Bacteria suspensions in saline ( 108 cell/mL) were assayed by Disk Method (DM) or Serial Dilutions Method (SDM) using automated analyzer Vitek (bio Meriuex, France). 

Diffusion tests are used to determine the susceptibility of microorganisms but have their limitations when equivocal results are obtained or in the case of prolonged serious infection, e.g., bacterial endocarditis, the elucidation of antibiotic action in relation to the pathogen needs to be more precise. Also the terms susceptible and resistant are open to interpretation. Thus, when in douht, a precise assessment is needed and involves determining the MIC of the antimicrobial compounds to the organisms using the 2-fold serial dilution method, which shown in Figure 11.2 [20,24]. 

The antibacterial activity of the fabric samples was tested using AATCC Method 100 using Staphylococcus aureus. The fabric swatch (l xl ) was placed in a sterilized flask containing Luria broth (Hi-media) solution, inoculated with 20 pi of test organisms and incubated at 37°C for 24 hrs in a laboratory shaker at 200 rpm. After incubation the number of colony forming unit (CFU) was counted by using serial dilution method. 

The serial dilution method of assay referred to in Section 1,4 is readily adapted for use in the estimation of relatively low antibiotic concentrations such as are found in the human (or other animal) body following administration of one or more therapeutic dosage forms. In order to achieve the sensitivity not available with other methods, the serial dilution procedure employs a smaller amount of test organism inoculum and a longer period of incubation. However, the precision that can be achieved with the other methods is lost here because of the rather wide potency ranges not covered by two-fold dilution increments. As mentioned earlier, the precision of the usual serial dilution assay may be improved by setting up graded dilution series (30) at the same time. 

The polymerization kinetics were followed by varying the reaction times and determining the molecular weights by light scattering photometry employing the serial dilution method. Attempts were made to follow the reactions at shorter times by UV/Visible spectrophotometry. The monomers and polymers were scanned from 900-190 nm and in all cases the bands of the monomers and polymers were found to overlap such that the reaction could not be easily monitored by this method. 

Liquid samples from the 23 corresponding flasks were determined to have a wide variance in specific activity between 0.01 MBq g" and 410 MBq g". This result represents lower specific and total activities per waste flask than might have been anticipated from historical records. The efficacy of the serial dilution method was tested against a control... 

The serial dilution method uses the same media to culture bacterial populations as does the method described in API RP 38. The techniqne may be modified slightly to interrogate snrface deposits removed from bioprobe studs. 

The main drawback with the serial dilution method is the time taken to incubate the colonies. The serial dilution test should be carried out at least twice on each sample of water or surface deposit. More rapid semi-quantitative techniques are available in kit form for detecting bacteria responsible for corrosion, where their presence within a process stream or storage area is suspected. 

Two standard methods were used in the determination of the mold flora of the marihuana samples. These were the serial dilution method for the plant material and the direct plating techniques for marihuana seeds (Mislivec and Stack, 198A). In the serial dilution plating method, 10 g of finely ground plant material were taken from each of the 25 marihuana samples, and used in the study. This test portion was... 

The media used in the two types of t. sts an different and may, thereby, modify the action of the antibacterial substances. The influon c of alkalinity, salts, and phosphate concentration on the activity of streptothricin (73) can be cited as an example of the effect of composition of medium on activity. Several different media were used in the serial dilution methods. The kinds of media used in testing (when given in the original publications) are as follows Streak-plate method (104,115,145,146,160,162, 164,166,170). Serial dilution method in (a) beef extract, small inocula (96,102), and large inocula (158) (6) beef heart broth (119,122), small inocula (112,177), and large inocula (50,71,113) (c) beef heart dextrose (123), small inocula (132) (d) nutrient broth (107,158,165) (e) nutrient broth dextrose (57,118,158) (/) 1% tryptone broth, small inocula (134). 

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