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Medical microbiologists focus on the growth and presence of microbial infections in patients, their effects on the human body and the way in which these infections are treated. Four kinds of microorganisms exist that cause infectious diseases in the human body and they include bacteria, viruses, parasites and fungi as well as an infectious protein called a prion. These specialists devise treatment protocols regarding infectious microorganisms by studying the characteristics and growth patterns of pathogens, the ways they are transmitted and their mechanisms of infection.
Other duties that a medical microbiologist would perform include identifying potential health risks to certain communities or monitoring the evolution of resistant strains of microorganisms and assisting in the design of health protocols and practices. They are also helpful in controlling or preventing disease outbreaks or epidemics.
The residency programme in medical microbiology takes 5 years to complete. The doctor wanting to specialise in this medical discipline first has to complete a 5-6 year undergraduate degree to qualify as a medical practitioner, and then has to also complete an internship training phase that takes 1-2 years to complete.
Medical microbiologists may want to specialise further and the sub-specialties include training in the specific microorganisms as mentioned above.
Diagnostic tests in medical microbiology
Diagnosing infectious diseases is done by taking a history from a patient and performing a clinical examination. Certain signs, symptoms and side-room investigations point to obvious infectious. At times, though, this isn't always the case and further investigations are necessary in order to help make the diagnosis. These investigations would include microscopy, culture and sensitivity (MCS) testing of specimens, biochemical tests and genotyping and will be discussed further.
Compound light microscopes are used to assess the presence of a microorganism in a specimen (except for viruses and prions which are too small). Fluorescence and electron microscopes are also used for to observing microorganisms (especially the aforementioned) in greater detail.
This test is the primary method used in order to test fluid and tissue samples in order to isolate infectious disease. The three main types of media used to test specimens include solid cultures, liquid cultures (parasites and mycobacteria), cell cultures (human or animal cell cultures to identify viruses).
Biochemical tests used to quickly identify bacteria include the use of enzymatic or metabolic characteristics that result in gases, alcohols and acids to be detected when bacteria are grown in selective liquid or solid media. The bacterium of interest will react with each chemical in a specific way, therefore making its identification easier.
Serological tests use antibodies to bind a causative antigen, and therefore a positive test will confirm the presence of the offending microorganism. Similarly, other tests such as immunoassays can detect the actual antigens from either infectious microbes or the proteins generated by an infected patient as a response to the infection (these tests are generally more expensive).
Polymerase chain reaction (PCR)
Nowadays, quantitative PCR testing is done versus standard PCR testing as the former uses fluorescence techniques and probes to detect the DNA molecules of an antigen, thereby providing a quicker availability of results which are also more accurate and less likely to be false positive due to issues such as contamination. Quantitative PCR testing is the current standard for detecting viral infections such as hepatitis and HIV.