Disadvantages of Phenotypic Methodologies

To runner with, phe nonype is defined as the visible characteristics of an beingness resulting from the interaction between its elementtic organization and the environment(Encarta 2008). Phe nonypic regularityology has many advantages and mischiefs and this audition talks about the dis advantages . The fact that closely laboratories can do an automatic deoxyribonucleic acid makes genotyping testing more avail suitable than phenotyping. scratch and fore well-nigh the test is not ordinarily readily available and accessible qualification the time for the effect of the result to be prolonged and inevitably long.Phenotypic method actings for most drugs does not energize clinically significant release off to secernate sensitive and repellant isolates and this has not been delineated for most of the drugs. From the prototypical principle, genotyping is slight complex, faster, and less expensive than phenotyping. other disadvantage is that certain changes in vindication mutation detected by genotyping atomic number 18 not sometimes detected by phenotyping. Such changes might be the charge step in the path to upper-level shield, and detection of these mutations might stimulate a change in therapy in a patient with detectable plasma viremia.Therefore phenotypical methodologies whitethorn not be able to determine a minute shifts in the susceptibility that follows the existence of whole sensation or more mutation which whitethorn lead to decreased drug effect. A good font is the 74V and 90M mutation in the sequinavir and didanosine respectively. Phenotypic method is applied to differentiate isolates based on the phenotypic appearances which are a corollary of genetic composition.The method has a low discriminating range at bottom same species and therefore has been applied only within same variety of organisms. many phenotypic methodologies have been suggested for use in discriminating among various groups of bacteria. These include biochemi cal tests (Olsen etal 1992)), phage susceptibility (Zierdlt etal 1980)), outer membrane protein profiles (Barekam etal 1981), antibody reactivity (Valsalovic etal 1994), fimbriation (Latham and Stamm 1984), bacteriocin production and susceptibility, and other methods.However, these systems have serious disadvantages, including unstable phenotypes, low esthesia at the intraspecies level, and limited specificity. However, a few phenotypic methods have been use successfully as bacterial origin tracking (BST) methodologies. Phenotyping that is dependent on the biochemical properties could be expensive and waste a lot of time . In this method the basal metabolic rate of the organism is greatly affected by the emersion parameters and conditions.Some variables used in the biochemical ascend can also give cabbage to chimerical discrimination. A good example is the L monocytogen which did not provide a coherent and reliable outcome make the use of antimicrobial susceptibility not to be encouraged while dealings with these bacteria. Phenotypic characteristics are not unremarkably reproducible as they are aspect of genetic expression and this is affected by and large by the prevailing growth parameters.Phenotypic methodological analysis despite advantages is not without its own terminus ad quem and setbacks as it is difficult under this method to determine and establish clinically rare value for the prediction of the virology response. It also has a notable problem of handling making it limited. It solely depends on the specific ideal storage, conveyance method and preparation. When specimen are improperly handled this may lead to false positive and negative data recital results.The DNA from virus while employ the method can be profane from unprofessional handling in the laboratory. It must be noted that both the genotypical and phenotypic approaches study and examine the most important viral quasispecies. Another disadvantage of phenotypic methodolog y is that in boldness of a virus that the proof of its protection to drug has been established and that has been selected by previous manipulations with drugs or has been acquired by initial transmittance ,if another resistant strain of such(prenominal) virus develop again, it may not be detected by this method.Furthermore, when dealing with the Human immunodeficiency virus for example, any self-possessed sample with copy of the virus less than 500 RNA more frequently than not will not stimulate results. In other words, the method is not sensitive to a minor anatomy case. The phenotype method also relies on the takings of the amplified gene sequences using the polymerase chain reply and as such the possibility of track contamination is highly plausible and this may occur with or without appropriate proficiency and carefulness.It is therefore advised for this reason that an outcome that does not tally with the present clinical state or previous treatment of patient is an i ndication for repeating the resistance test. In conclusion, phenotypic method has some(prenominal) disadvantages in that it is highly variable, due to environmental factors that lead to variation in gene expression, it has poor reproducibility and the discriminatory provide is unsatisfactory. It may also falsely comrade unrelated isolates and conversely when only a tiny and narrow framework of biochemical tests are used.