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Medical Microbiology Terminology for Patients and Students

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What is microbiology and why is it important?

Microbiology is the science which deals with the study of microbes. Medical microbiology is the medical microbiologyfield of medicine which deals with the diagnosis, treatment and prevention of infectious diseases. Bacteria, viruses, fungi and parasites are the main microorganisms of focus.

Medical microbiology is a recognized specialty in the UK. In other parts of the world including the United States infectious disease specialists and physicians who don’t specialize treat a number of infectious diseases though. Therefore, knowledge of some of the basic terms having to do with medical microbiology is important to patients. It improves communication in health care. It also is critical to the understanding of literature and other forms of information pertaining to infectious diseases. The increase in the prevalence of these types of diseases as evident in the news, underscores the importance of the latter.

Medical Terminology  


Acute – Consisting of severe symptoms and of a short course.  

Acuity – The level of severity of an illness.  

Antibiotic – An agent that destroys or subdues the growth or multiplication of bacteria. Various ones are products of microorganisms. The main producers of them are bacteria, fungi and molds. There are medications used to treat humans and some animals.    

Antimicrobial – An agent that kills or suppresses the growth or multiplication of microbes. Antibiotics, antifungals and antivirals all belong to this general category.

Antifungal – An antimicrobial that kills or suppresses the growth or multiplication of fungi

Antiviral – An antimicrobial that kills or suppresses the growth or multiplication of viruses.   

Bacterium – Any of the microorganisms which are single cells contained within a cell wall and which multiply by cell division. They do not have a true nucleus in that their DNA is not contained in a nuclear membrane.  – Bacteria pl. – Bacterial adj. 

Chronic – Persisting over a long period of time. It is a term used in reference to a disease that progresses slowly and continues over a long period of time.  

Convalescent serum – Is the serum from a person who has recovered from an infection. It contains antibodies against microbes that caused the infection. Serum is the clear liquid portion of blood which separates upon clotting.  

Ectoparasite – A parasite that lives on the surface of a host’s body.  The mites, lice and fleas are examples.   

Fungus – Is any of the microorganisms which have a cell nucleus containing their DNA and which reproduce by spores. – Fungi – pl. – Fungal – adj.

Host – An organism (animal or plant) on which another one (parasite) depends for survival and reproduction.  

Host range – Is the gamut of organisms a virus or other microorganism can infect. Evidence of that infection might range from overt disease to no signs of illness.

Infectious disease – Disease caused by the growth and multiplication of microbes which have entered the body. Germ disease is a lay term for it.    

Infest To live in the tissues or organs as a parasite. – Infestation – n.  

MicrobeMicrobial – adj. – Is a microorganism. The term refers especially to those that can cause disease in animals. They include bacteria, fungi, viruses and protozoa. Germ is a lay term for it.  

Microorganism – A life form visible only through a microscope.  

Parasite – Is an organism that lives on or within a host and depends on that host for food and survival. The main categories of parasites are protozoa, helminths (worms), and ectoparasites.  – Parasitic – adj.   

Pathogen – Is a microorganism that produces disease. – Pathogenic – adj.      

Pathogenicity – Is the ability of a microorganism to cause disease (i.e. harm to a host).  Thus, it is the hallmark of a pathogen.  The ability to cause disease is what distinguishes a pathogen from a commensal – a microorganism that lives in a host  without causing disease in the host.  In some cases there is a mutually beneficial relationship between a commensal and a host.  An example of the latter is the good bacteria of the gut.

Protozoan – Single-cell organisms that are visible only with a microscope. They can be either free living or exist as parasites in humans. They might live in a human’s intestinal tract or blood. Their multiplication and humans allows them to survive and cause disease. There are four major groups based on how they move about.  – Protozoa – pl. – Protozoal – adj.  

Replication – The act or process of reproducing or duplicating. It oftentimes refers to microorganisms.  – Replicate – v.  

Reservoir of infection – Living or nonliving material in nature on which, or in which, infectious organisms multiply and depend on as a source of survival.  

RNA dependent RNA polymerase – Is the enzyme of an RNA virus that catalyzes the copying of new pieces of RNA from itself instead of the usual transcribing of if from DNA which occurs in higher organisms.

Serology – The science which deals with the properties and reactions of blood serum as they relate to immune system function.  – Serologic – adj.

Serotype – A subdivision of a particular group of microorganisms or cells based on a distinguishing set of antigens they have in common. It is determined by serologic testing.  

Sepsis (Septicemia) – Is infection of the blood stream with signs and symptoms of the body’s response to it.  In the strictest sense of the term, the pathogen that causes it is bacterial.  But in a broader since, the term also applies to blood stream infection by other microbes such as fungi, viruses, and parasites.  The condition differs from bacteremia in that the immune system goes into overdrive, so to speak, in its response to the infection.  Manifestations may range from chills and fever to shock.  It can be life-threatening depending upon the extent of the infection and the degree of the immune response. 

Strain A population of microorganisms with the same genetic makeup, structure, composition, etc.  It is thus, a genetic variant or subtype of a similar microorganism, but has certain characteristic features of its own that distinguish it. 

Titer – Is a way of expressing of the concentration of a substance. It most commonly refers to the concentration of antibodies or virus in the blood.  It is the maximum number of stepwise dilutions of serum at which the substance is detectable by a given test method. The higher the number of dilutions at which it is detectable the greater is its concentration in the body and vice versa.  

Ultramicroscopic – Is a term which means too small to see with a regular light microscope.

Vaccination – The induction of adaptive immunity to a pathogen through the injection of a vaccine. 

Vaccine – A dead or weakened form of a pathogen, given in order to stimulate immunity against it.  

Vector – An organism that carries and transmits disease-causing microorganisms from one host to another.  The mosquito and its transmission of malaria is an example.    

Viremia – The presence of viruses in the blood stream.  

Virulence – Is the degree to which a pathogen can cause disease.  The severity of the disease it produces is an indicator of the degree. – Virulent – adj.

Virus – Is an ultramicroscopic single-cell organism that replicates only within host cells . Many are pathogenic. They contain either DNA or RNA wrapped in a thin coat of protein – not in a true nucleus. – Viral – adj.

RNA virus – Is a virus whose genetic material is RNA instead of DNA.











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