BIOL 232 (good)

Microorganism

Organism too small to be seen without a microscope

Pathogen

Microbe that causes disease

Opportunistic pathogen

Causes disease in compromised hosts or unusual sites where it normally does not cause disease (e.g.

Normal flora (microbiota)

Microbes that reside on or in the body without causing disease

Commensal symbiotic relationship

One organism benefits while the other is neither helped nor harmed

Mutualistic symbiotic relationship

Both organisms benefit

Host

Organism infected by a microbe

Portal of entry

Site where a pathogen enters the body (e.g.

Adherence

Attachment of microbes to host tissues and a step of pathogenesis

Colonization

Establishment of microbial growth on a body surface without necessarily causing disease

Infection

Invasion and multiplication of a pathogen in the body

Disease

Damage or impairment of host function resulting from infection

Infectivity

Ability of a microbe to infect a host

ID50

Microbial dose required to infect 50% of a studied population

Virulence

Degree of pathogenicity or severity of disease caused by a microorganism

LD50

Microbial dose required to kill 50% of a studied population

Gram staining

Method used to classify bacteria based on cell wall structure

Gram-positive bacteria

Thick peptidoglycan cell wall and retains crystal violet stain (purple)

Gram-negative bacteria

Thin peptidoglycan wall with outer membrane containing LPS and stains pink/red

Cell wall

Additional layer external to plasma membrane found in bacteria and fungi

Endotoxin

Toxin associated with gram-negative outer membrane (lipid A of LPS)

Exotoxin

Protein toxin made and secreted by bacteria

Innate immunity

Nonspecific defense mechanisms present at birth

Neutrophils

Innate immune cells that phagocytose microbes especially in bacterial infections

Macrophages

Phagocytic cells that activate adaptive immunity

Adaptive immunity

Specific immune response with memory

Cell-mediated immunity

T-cell based immune response targeting infected cells

Humoral immunity

Antibody-mediated immune response involving B cells

Reservoir

Natural habitat of a pathogen

Vector

Animal that transmits pathogens between hosts

Fomite

Inanimate object that transmits pathogens

Incubation period

Time between exposure and onset of symptoms

Prodrome period

Early nonspecific symptoms of disease

Contagious period

Time during which infection can be transmitted

Binary fission

Asexual reproduction where a prokaryote divides into two identical cells

Lag phase

No increase in number of living bacteria

Log phase

Exponential increase in number of living bacteria

Stationary phase

Plateau where bacterial growth equals death

Death phase

Exponential decrease in number of living bacteria

Sporulation

Formation of highly resistant dormant endospores during environmental stress

Endospore

Resistant dormant bacterial structure that increases survival not replication

Germination

Return of dormant spore to active vegetative cell under favorable conditions

Capsid

Protein shell that surrounds and protects viral genome

Enveloped virus

Virus with lipid membrane surrounding capsid derived from host cell

Non-enveloped virus

Virus lacking a lipid envelope

Viral genome

Genetic material determining replication strategy and host interaction

Sense RNA

Viral RNA that acts directly as mRNA and can be translated by host ribosomes

Antisense RNA

Viral RNA that must be converted into sense RNA before translation

Viral tropism

Specificity of virus for certain host cells or tissues

Flagella

Structures that help bacteria move in watery environments

Pili (fimbriae)

Hair-like sticky structures that aid in attachment

Cocci

Spherical bacteria

Bacilli

Rod-shaped bacteria

Diplococci

Cocci arranged in pairs

Streptococci

Cocci arranged in chains

Staphylococci

Cocci arranged in clusters

Spirochetes

Spiral-shaped bacteria

Bacteria

Cellular organisms capable of independent reproduction

Viruses

Acellular organisms requiring host machinery to reproduce

Prokaryote

Cell lacking nucleus and membrane-bound organelles

Eukaryote

Cell containing nucleus and membrane-bound organelles

Obligate intracellular organism

Organism that must live inside host cells (e.g.

Antimicrobial agents

Drugs used to treat infections caused by microbes

Antibiotics

Drugs that target bacterial infections

Antivirals

Drugs that interfere with viral replication cycle

Bacteriostatic

Antibiotics that inhibit bacterial growth

Bactericidal

Antibiotics that directly kill bacteria

Broad-spectrum antibiotics

Antibiotics effective against many types of bacteria

Narrow-spectrum antibiotics

Antibiotics targeting specific bacteria

Superinfection

Infection caused by resistant organisms after antibiotic use

Pharmacokinetics

Absorption distribution metabolism and excretion of drugs

Pharmacodynamics

Biological effects and mechanisms of drug action

Minimum inhibitory concentration (MIC)

Lowest antibiotic concentration that inhibits bacterial growth

Minimum bactericidal concentration (MBC)

Lowest antibiotic concentration that kills bacteria

Penetration

Ability of antibiotic to reach site of infection

Toxicity

Degree to which a drug causes harm

Therapeutic index

Balance between drug efficacy and toxicity

Mutation

Random genetic change that can cause antibiotic resistance

Sepsis

Dysregulated host response to infection causing organ dysfunction

Septic shock

Sepsis with hypoperfusion requiring vasopressors and elevated lactate

Systemic inflammatory response syndrome (SIRS)

Systemic inflammation response that is sensitive but nonspecific

SOFA score

Tool assessing organ failure to predict mortality

qSOFA

Rapid bedside tool to identify patients at high risk of death from sepsis

PAMPs

Pathogen-associated molecular patterns found on microbes

DAMPs

Damage-associated molecular patterns released from injured host cells

Warm shock

Early septic shock characterized by vasodilation and warm skin

Cold shock

Late septic shock characterized by vasoconstriction and poor perfusion

Disseminated intravascular coagulation (DIC)

Widespread clotting leading to bleeding and organ ischemia

Bacteremia

Presence of bacteria in the blood

Toxemia

Presence of toxins in the blood

Superantigens

Toxins that cause massive T-cell activation and cytokine storm

Tumor necrosis factor alpha (TNF-α)

Pro-inflammatory cytokine released during sepsis

Early sepsis management

Rapid oxygen antibiotics fluids and lactate measurement

Empiric antibiotic therapy

Initial broad-spectrum antibiotics given before culture results