Definition and Overview

Microbiology is the science that studies microscopic organisms or those that are alive but are too small to be seen by the naked eye. It is a very broad and general subject, and as such, has many sub-groupings. Its branches include virology (the study of viruses), mycology (the study of fungi), bacteriology (the study of bacteria) and parasitology (the study of parasites). These sub-groups fall under microorganisms that cause infectious diseases which make them a part of “medical microbiology”, the branch of medical science that deals with their prevention, diagnosis and treatment.

Medical microbiologists study pathogens or agents that carry infectious diseases. They also analyse how the pathogen spreads to ascertain the speed with which the infection diffuses and how the pathogen affects a person once infection sets in. They work with physicians by providing information on the infectious disease and recommend a treatment plan for patients. A microbiology evaluation at this level can consider the possibility of an infectious disease from samples taken from patients who exhibit specific symptoms. An important detail being considered is how these affected patients acquired their suspected pathogen.

Who Should Undergo and Expected Results

Patients who are suspected of being sick due to microbial infections are those who are likely to undergo microbiology evaluation. Below are the common causes of infectious diseases that will normally require a microbiology evaluation to identify:

  • Bacteria – The body has both good and bad bacteria. The former naturally flourish in our bodies to fight off infection (such as in the vagina) and produce amino acids (in the bowels). Bad infectious bacteria, on the other hand, come from external sources and cause infectious diseases. Examples are bacterium mycobacterium tuberculosis (which causes tuberculosis) and streptococcus (which causes pneumonia). Meanwhile, salmonella bacteria cause food poisoning and other bacteria cause typhoid fever, meningitis and chlamydia, among others. Antibiotics or anti-bacterial medication are usually enough to treat bacterial infections.

  • Viruses – Viral infections are more common than the others. Minor and common viral infections include colds, coughs, influenza and chickenpox. Viruses are different from bacteria in that they attack and change the cells they infect. Viral infections usually resolve themselves even without medication. Treatment provided by doctors is mostly dedicated to the symptoms resulting from the body fighting off the infection.

  • Fungi – There are many different fungi that can cause infection in humans. Most common fungal infections include athlete’s foot, ringworm and other localised rashes. Other more deadly fungi can cause histoplasmosis (caused by Histoplasma capuslatum) or “black mold” (Stachybotrys chartarum) that causes long-term respiratory damage.

  • Parasites – These microbes latch on to another host to survive. Examples are hookworms and tapeworms that suck blood from the small intestine causing anemia and iron deficiency. They are usually ingested from contaminated food or water. Other parasitic infections are malaria (from an infected mosquito) and amoebic dysentery (diarrhea with blood and mucus).

How Does the Procedure Work

When a patient experiences symptoms indicative of infectious diseases, like high-grade fever, rashes and muscle and joint pain, he must immediately schedule an appointment with his doctor. Although these symptoms may be due to minor illnesses, they may also be indications of serious infectious diseases.

The consultation will start with a brief interview where the doctor would obtain information about the patient’s medical history and symptoms. The patient’s vital signs, such as blood pressure, weight and breathing, among others, will also be obtained and assessed later on. The doctor may also ask the patient if he has gone somewhere (possibly out of the country) just to rule out infectious diseases that are foreign in origin.

After the physical examination, the doctor may request a blood, urine and culture test to identify the pathogen that causes the symptoms.

The only way to correctly diagnose the problem is through microbiological evaluation using microbial culture, blood testing and microscopy (microscopic examination of tissue or fluid sample from the patient). These procedures will positively identify which pathogen is causing the disease and this will be helpful in figuring out which treatment option is applicable.

The physician will rely on the medical microbiologist’s recommendation regarding the strain of the pathogen, any resistances to medication it may have and the best treatment option for the patient.

Possible Complications and Risks

A microbiology evaluation may take some time to process considering the number of tests that have to be performed on the samples. During this time, the patient may be at risk of getting worse as he waits for the diagnosis.


  • Kumar V, Abbas AK, Aster JC. Neoplasia. In: Kumar V, Abbas AK, Aster JC, eds. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 7.
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