Clinical laboratories have relied historically on phenotypic methods (i.e. culture and biochemical tests) to identify microorganisms. This can be time consuming task especially with slow growing organisms such as Mycobacterium tuberculosis. Molecular methods are now well established in the diagnosis of infectious disease. . (Harwood 2012). For the purpose of this essay I will give a brief overview of both traditional and molecular methods that re used today. I will focus on the pros and cons of both methods in identifying some bacteria.
Traditional Methods of Identification
Traditional methods of identifying organisms and infections in a clinical setting includes; inoculation of the specimen onto an appropriate media, liquid broth …show more content…
However, despite these advances, the overall time to result of blood cultures is too long. Thus delaying appropriate treatment for the infection. (Liesenfeld et al 2014)
Mycobacterium Tuberculosis. M.Tuberculosis is an obligate aerobe and grows very slow in media. It grow at a temperature of 37 degrees Celsius. They are grown on selective media. Lowenstein-Jenson. They are identified by their culture, growth and biochemical tests. Because bacteria are hard to grow and inoculation can take up to 14-15 hours. And incubation of up to eight weeks is needed for colonies to be observed.
After incubation the following biochemical tests are performed to aid identification, it is usually catalase positive. It produces the enzyme nitrate reductase and reduces nitrate to nitrite and is therefore positive for nitrate reduction and it is niacin positive.
Although the traditional culture growth and biochemical test are time consuming new automated methods have reduced the time taken to identify Mycobacterium Tuberculosis. Such as automated radiometric culture methods. This has reduced the detection time to within 9-16 days. (Chandra Parija 2012).
Molecular Methods used to identify …show more content…
Bacteria culture are transferred onto a metal plate. A laser is then used to form newly ionized particles. These particles are then brought up through a vacuum tube (time of flight) the ions are separated on their mass to charge ratio. A mass analyser creater a spectral profile which is unique to each component that is analysed.
Detects A large range of pathogens at the same time.
Fig. 2 (Madigan et al, 2015; Perry, 2014; Chandra Parija, 2012).
As you can see from this table there are a large range of molecular methods available in clinical laboratories today with new technologies constantly emerging. These provide rapid identification and cost effectiveness eg with multiplex PCR. However molecular technologies can have pitfalls when identifying some bacteria.
PCRs are now fully integrated in clinical medical laboratories. Traditional PCR are highly sensitive in identifying pathogens and a less time consuming and faster than traditional methods. However Single PCRs are expensive to run. They are also prone to contamination of the DNA sample, which can give a false positive and can delay identification of the