Review 3 concepts

Natural antibiotics

Made by microbes (e.g., Penicillium → Penicillin, Streptomyces → Streptomycin).

Semi-synthetic antibiotics

Modified natural antibiotics (e.g., Amoxicillin).

Synthetic antibiotics

Fully lab-made (e.g., Sulfonamides, Ciprofloxacin).

Cell Wall Synthesis Inhibitors

e.g., Penicillin; cause cell lysis.

Cell Membrane Disruptors

e.g., Polymyxins; damage membrane integrity.

Protein Synthesis Inhibitors

e.g., Tetracyclines; block ribosomes.

Nucleic Acid Synthesis Inhibitors

e.g., Ciprofloxacin; block DNA/RNA processes.

Metabolic Pathway Inhibitors

e.g., Sulfonamides; block folic acid synthesis.

Minimum inhibitory concentration (MIC)

The smallest concentration (highest dilution) of drug that visibly inhibits growth. Useful in determining the smallest effective dosage of a drug.

Kirby-Bauer test

The Kirby-Bauer disk is used to determine the susceptibility of microbes to various antimicrobials.

Portals of Entry

Common routes through which pathogens enter the body, e.g., Respiratory Tract: Influenza virus, Gastrointestinal Tract: Salmonella, Skin: Staphylococcus aureus, Urogenital Tract: Neisseria gonorrhoeae.

Portals of Exit

Common routes through which pathogens exit the body, e.g., Respiratory Tract: Mycobacterium tuberculosis, Gastrointestinal Tract: Escherichia coli, Skin: Staphylococcus aureus, Blood: HIV.

Human Reservoir

Neisseria meningitidis in the nasopharynx of asymptomatic carriers.

Animal Reservoir

Rodents as reservoirs for Yersinia pestis, the bacterium responsible for plague.

Non-Living Reservoir

Water contaminated with Vibrio cholerae, the bacterium that causes cholera.

First line of defense

Physical and chemical barriers that prevent pathogens from entering the body, e.g., skin, mucus in nose and throat, stomach acid, tears, and saliva.

Second Line of Defense

Innate Immune Response that attacks invaders that get past the first line, e.g., inflammation, fever, white blood cells (e.g., phagocytes engulfing pathogens).

Third Line of Defense

Adaptive Immune Response that targets specific pathogens with memory for future defense.

Rubor

Redness; caused by increased circulation and vasodilation in injured tissues.

Calor

Warmth; heat given from the increased blood flow.

Tumor

Swelling from increased fluid escaping into the tissues.

Dolor

Pain; caused by the stimulation of nerve endings.

Loss of function

A consequence of inflammatory responses.

Neutrophils

Phagocytize bacteria.

Lymphocytes

T and B cells, third line of defense.

T cells

Cell mediated immunity.

B cells

Antibody mediated immunity. Production of antibodies.

Monocytes

Become macrophages that eat foreign objects.

Eosinophils

A type of white blood cell involved in allergic reactions and parasitic infections.

Basophils

Release histamines. Localized basophils are called mast cells.

Fever

An abnormally elevated body temperature that inhibits multiplication of temperature-sensitive microorganisms.

Role of fever in infection control

Impede the nutrition of bacteria by reducing the availability of iron; increases metabolism and stimulates immune reactions.

IgG

Primary response, memory cell response, neutralizes bacterial toxins.

IgM

First to be made in primary response, starts complement fixation, responds to ABO antigens.

IgA

Found in serous and mucous membranes, short lived.

IgD

signals b cells to activate

IgE

Responses to allergies and parasite infections.

Helper T cells

Activate macrophages, assist B-cell processes, and help activate cytotoxic T cells.

Regulatory T cells

Control the T-cell response by secreting anti-inflammatory cytokines or preventing proliferation.

Cytotoxic T cells

Lead to the destruction of infected host cells and other 'foreign' cells.

Innate immunity

Non-specific; first and second line of defense.

Acquired immunity

Specific; third line of defense.

Live, attenuated vaccines

Stimulate strong immunity due to the pathogen's ability to replicate in the vaccine recipient.

Whole killed cell vaccines

Contain a wide range of surface markers that can activate the immune responses.

Broad-spectrum antibiotics

Use when the cause of infection is unknown.

Mixed infections

Infections caused by more than one pathogen, some of which may be resistant to treatment.

Narrow-spectrum drugs

Antibiotics that only target a specific group of bacteria, used when the pathogen is known to minimize resistance and microbiome disruption.

Nosocomial infection

Infectious diseases that are acquired or develop during a hospital stay or stay in another health care facility.

Catheter-associated urinary tract infections (CAUTI)

A type of nosocomial infection associated with the use of urinary catheters.

Central line-associated bloodstream infections (CLABSI)

A type of nosocomial infection associated with the use of central lines.

Surgical site infections (SSI)

Infections that occur at the site of a surgical procedure.

Ventilator-associated events (VA)

Infections or complications that occur in patients who are on mechanical ventilation.

Characteristics of a good antibiotic

Toxic to the microbe but not to humans, microbicidal, soluble in body fluids, remains potent, does not lead to resistance, remains active in tissues, easily delivered, reasonably priced, and does not disrupt host health.

Zone of inhibition

The area around an antibiotic disk where bacteria cannot grow, indicating the effectiveness of the antibiotic.

Endotoxins

Toxins that are part of the bacterial cell wall and are released when the bacteria die.

Exotoxins

Toxins secreted by bacteria that can damage host tissues.

Antibiotic resistance

The ability of bacteria to resist the effects of an antibiotic, often due to overuse or misuse of antibiotics.

Microflora

The community of microorganisms that normally inhabit various parts of the body and play a role in health.

Classical complement pathway

Activated by antibodies bound to microbial surfaces.

Lectin pathway

Activated by lectins that bind to sugars on microbial surfaces.

Alternative pathway

Activated directly by repeating molecules on the microbial surface, such as lipopolysaccharides (LPS).

Asymptomatic carriers

Individuals who are infected but show no symptoms of disease.

Incubating carriers

Individuals who are infected but show no symptoms of disease during the incubation period.

Convalescent carriers

Recuperating patients without symptoms who continue to shed viable microbes.

Chronic carriers

Individuals who harbor an infectious agent for a long period after recovery due to latency.

Passive carriers

Medical and dental personnel who may mechanically transfer pathogens to patients.