Medical Microbiology: Key Terms and Definitions for Bacteria, Viruses, Fungi, and Parasites

Bacter-

Pertaining to bacteria

Fung-

Pertaining to fungi

Parasit-

Pertaining to parasites

Vir-

Pertaining to viruses

Cephal(o)-

Head

Chole-

Gall/bile

Cyst-

Bladder

Docho-

Duct or tube (literally "cup")

Enter(o)-

Intestines

Hepat(o)-

Liver

Mening(o)-

Meninges

Myel(o)-

Marrow

Myo-

Muscle

Nephr(o)-

Kidneys

Oste(o)-

Bone

Pneumo(n)-

Air/lungs

Pyelo-

Pelvis

Pyo-

Pus

Thora(c)-

Chest/thorax

-uria

Pertaining to the urine
Examples: Asymptomatic bacteriuria

-itis

Inflammation
Examples: Cystitis, osteomyelitis

-emia
Examples: Bacteremia, viremia

In the blood

-ia
Examples: Pneumonia

Condition, especially an abnormal state

-lithiasis
Examples: Nephrolithiasis, cholelithiasis

Presence of stones

-centesis
Examples: Paracentesis

Puncture to remove fluid from a cavity

Epidemiology

The study of how diseases affect the health and illness of populations

Antimicrobial Resistance

When an antimicrobial has lost its effectiveness

Antibiotic Stewardship

A public health effort that ensures the judicious use of antibiotic prescribing

Etiology

The cause of a disease or condition

Incidence

The number of new diagnoses of a condition within a population

Prevalence

The proportion of a population that has a condition at a specific time

Isolation

The separation of a patient with or suspected of having an infection from other patients

Virulence

The ability of a microorganism to cause damage to the host

Zoonotic

Transmission occurring from an animal source

Endemic

Occurring within a specific area or community

Epidemic

Widespread occurrence of a disease within a community at a specific time

Pandemic

Widespread diseases occurring within a whole country or the world at a specific time

Outbreak

Disease occurring in excess of normal

Microbiome

The microorganisms in a specific environment, including the whole or part of the body

Immunocompromised

Having an impaired immune system. This could be intentional through immunosuppression or due to a primary or secondary immunodeficiency

Opportunistic Infection

An infection that affects patients with immunocompromising conditions

Asymptomatic

Without symptoms (a- or an- is a prefix meaning without)

Pathogen

A microorganism that can cause disease

Virus

An infectious microbe consisting of a segment of nucleic acid (either DNA or RNA) surrounded by a protein coat which cannot replicate on its own and must infect cells and use components of the host cell to make copies of itself.
Examples: Herpes simplex virus (HSV), human papilloma virus (HPV), hepatitis A

Fungus

Eukaryotic organism which can cause infection as a yeast or mold.
Examples: Coccidioides, Candida, Cryptococcus, Aspergillus

Parasite

Eukaryotic organism that lives on or in a host organism and gets its food from or at the expense of its host. Commonly used to refer to protozoa and worms.
Examples: Giardia, Toxoplasma, Pinworm

Bacteria

Prokaryotic, single-celled organism that can cause infection.
Examples: Staphylococcus aureus, E. coli

Gram positive

Bacteria that stain purple with a Gram stain due to a thick cell wall

Gram negative

Bacteria that stain pink with a Gram stain due to a thin cell wall

Staph-

Clusters (from Greek for grape)

Strep-

Pairs and chains (from Greek for twisted)

Coccus

Round shape (from Greek for grain or seed)

Bacillus

Rod-shaped (from Latin for stick)

Acid-fast

Retains stain through acid decolorization - commonly used to identify mycobacteria

Bactericidal

Rapidly causes bacterial cell death

Bacteriostatic

Inhibits growth of bacteria, leading to slower cell death

Empiric Therapy

Antibiotic therapy selected to treat suspected pathogens before culture and susceptibility results are available

Definitive Therapy

Antibiotic therapy selected to treat known pathogens once culture and/or suscepitbility results are available

Prophylactic Therapy

Antibiotic therapy selected to prevent infection

Suppressive Therapy

Antibiotic therapy selected to control or reduce the growth of bacteria in known infections, usually when treatment cure is not possible

Ke

Rate of elimination, important in pharmacokinetic calculations for vancomycin and aminoglycosides

Area under the curve (AUC)

Total exposure of a drug

Culture

A laboratory test that involves growing bacteria or other organisms on a growth media for the diagnosis of an infection

Gram Stain

A stain used to differentiate gram-positive from gram-negative organisms

Nucleic Acid Amplification Test (NAAT)

A test that detects DNA or RNA. Can be qualitative (yes/no) or quantitative. Examples include polymerase chain reaction (PCR) and Loop-mediated isothermal amplification (LAMP) among others

Quantitative PCR

A quantitative measurement of amount of nucleic acids of a specific organism in a sample, often reported as copies/mL.

Titer

A quantitative measurement of antibodies

Antigen

Any substance that causes the immune system to produce antibodies

Antibody

An immunoglobulin formed in response to an antigen

Incubation Period

The time period between exposure to an infectious agent and when symptoms first appear

Latency Period

A period in which an infection is undetectable and/or asymptomatic

I & D

A procedure to control the source of infection. Can refer to "incision and drainage" or "irrigation and debridement" depending on the context.

Radiograph (a.k.a., X-ray)

Imaging procedure that produces a static two-dimensional image generated by passage of x-rays through the patient

Computed Tomography (CT)

Imaging procedure in which a narrow beam of x-rays are quickly rotated around the body to generate cross-sectional tomographic images

Magnetic resonance imaging (MRI)

Imaging procedure that uses magnetic fields to generate a three-dimensional image

Echocardiogram

Imaging procedure that uses ultrasound to create pictures of the heart valves and chambers

U=U (undetectable=untransmissible)

(undetectable= untransmissible) Concept in HIV