Microbial Control and Principles of Disease: Study Guide (Chapters 13 & 14)

Study Guide - Smart Notes

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Sterilization: The process that destroys all forms of microbial life, including bacterial spores. Used for surgical instruments and media preparation.
Disinfection: Eliminates most pathogenic microorganisms (except spores) on inanimate objects.
Antisepsis: Application of antimicrobial agents to living tissue/skin to reduce infection risk.
Sanitization: Reduces microbial population to safe levels, commonly used in food service.

Heat: Most effective method for sterilization. Includes moist heat (autoclaving) and dry heat.
Autoclave: Standard conditions are 121°C, 15 psi, for 20 minutes. Used for sterilizing media, glassware, and instruments.
Cold: Refrigeration and freezing slow microbial growth but do not kill most microbes.
Ultraviolet (UV) Radiation: Damages DNA; effective for surface sterilization only.
Gamma Radiation: Penetrates deeply; used for sterilizing medical supplies and food.
Filtration: Physically removes microbes from liquids or air using membrane filters; useful for heat-sensitive solutions.

Selective Toxicity: The ability of a drug to target microbial cells without harming host cells.
Minimum Inhibitory Concentration (MIC): The lowest concentration of an antimicrobial that inhibits visible growth of a microorganism.

Class	Target
Penicillins	Cell wall synthesis
Macrolides	Protein synthesis (50S ribosomal subunit)
Tetracyclines	Protein synthesis (30S ribosomal subunit)
Quinolones	DNA synthesis
Rifamycins	RNA synthesis
Sulfa drugs	Metabolic pathways (folic acid synthesis)
Polymyxins	Cell membrane

Production of enzymes that destroy or inactivate the drug (e.g., beta-lactamases).
Alteration of drug target sites (e.g., mutation in ribosomal proteins).
Efflux pumps that expel the drug from the cell.

Pathogen: Any microorganism that can cause disease.
Infection: The invasion and multiplication of pathogens in the body.
Disease: The result of infection that leads to tissue damage or dysfunction.
Virulence: The degree of pathogenicity or severity of disease caused by a microbe.

The microorganism must be present in every case of the disease.
The microorganism must be isolated from the diseased host and grown in pure culture.
The cultured microorganism must cause the disease when introduced into a healthy host.
The microorganism must be re-isolated from the experimentally infected host.

Incubation Period: Time between pathogen entry and appearance of symptoms.
Prodromal Period: Early, mild symptoms appear.
Illness Period: Disease is most severe; characteristic signs and symptoms are present.
Decline Period: Signs and symptoms subside as the immune response or treatment reduces pathogen numbers.
Convalescence (Recovery): Body returns to pre-disease state; recovery occurs.

Direct Transmission: Person-to-person contact (e.g., touching, kissing).
Indirect Transmission: Via air (droplets), fomites (inanimate objects), or vectors (insects).

Bacteremia: Presence of bacteria in the blood.
Septicemia: Growth and multiplication of bacteria in the blood, often leading to systemic inflammation.
Acute Infection: Rapid onset, short duration (e.g., influenza).
Chronic Infection: Develops slowly, persists over a long period (e.g., tuberculosis).
Latent Infection: Pathogen remains inactive for a time but can reactivate (e.g., herpes simplex virus).

Sign: Objective evidence of disease observed by others (e.g., fever, rash).
Symptom: Subjective experience reported by the patient (e.g., pain, fatigue).

What method kills spores? Answer: Sterilization
Autoclave conditions? Answer: 121°C, 15 psi, 20 minutes
Difference between sign and symptom? Answer: Sign is objective and observable; symptom is subjective and felt by the patient.
What does penicillin target? Answer: Cell wall synthesis
What is MIC? Answer: Minimum Inhibitory Concentration—the lowest concentration of a drug that inhibits microbial growth.
Name 5 mechanisms of antibiotics Answer: Cell wall synthesis, cell membrane, protein synthesis, DNA/RNA synthesis, metabolism
Define bacteremia vs septicemia Answer: Bacteremia is the presence of bacteria in the blood; septicemia is bacterial growth in the blood causing systemic illness.
What causes antibiotic resistance? Answer: Enzymatic destruction of drug, alteration of target, efflux pumps
Acute vs chronic vs latent? Answer: Acute: rapid onset/short duration; Chronic: slow onset/long duration; Latent: inactive, can reactivate
What is selective toxicity? Answer: The ability of a drug to harm microbes without harming the host