Lecture Quiz 3 Studyguide

Define bacteriocidal vs bacteriostatic.

• Bactericidal drugs kill the target bacteria directly.

• Bacteriostatic drugs inhibit bacterial growth and reproduction, allowing the host’s immune system to eliminate the pathogen. 

Define broad-spectrum vs narrow-spectrum antibiotics.

• Broad-spectrum antibiotics target a wide variety of bacterial species, including both Gram-positive and Gram-negative bacteria.

• Narrow-spectrum antibiotics target only specific families or groups of bacteria.They are used when the specific bacteria is known or to reduce the impact on beneficial microbiota.

Define dosage and route of administration.

• Dosage is the amount of medication given during a certain time interval to achieve optimal therapeutic levels without toxicity.

• Route of administration refers to how the drug is delivered to the body—such as orally, intravenously, topically, or intramuscularly. The route affects how quickly and effectively the drug reaches the infection site.

Define synergistic and antagonistic drug interactions.

• Synergistic interactions occur when two drugs work together to produce a greater effect than either drug alone (e.g., trimethoprim + sulfamethoxazole).

• Antagonistic interactions occur when drugs interfere with each other’s actions, reducing their overall effectiveness (e.g., bacteriostatic drugs reducing the effectiveness of bactericidal ones).

Define selective toxicity.

Selective toxicity is the ability of a drug to target pathogens without causing significant harm to the host. This depends on differences between microbial and host cell structures or metabolism.

List the (5) classes of antibacterial compounds, including mode of action and an example of each.

Class; Mode of Action; Example

1. Inhibitors of Cell Wall Synthesis; Block peptidoglycan formation, weakening bacterial cell walls and causing lysis;Penicillin, Cephalosporin, Vancomycin

2. Inhibitors of Protein Synthesis; Bind to bacterial ribosomes (30S or 50S subunits) to prevent translation; Tetracycline, Erythromycin, Streptomycin

3. Inhibitors of Nucleic Acid Synthesis; Interfere with DNA replication or RNA transcription; Fluoroquinolones (Ciprofloxacin), Rifampin

4. Disruptors of Plasma Membrane Function; Damage or alter membrane integrity, causing leakage of cellular contents; Polymyxin B, Daptomycin

5. Metabolic Pathway Inhibitors (Antimetabolites); Block essential metabolic reactions (e.g., folic acid synthesis); Sulfonamides, Trimethoprim

Name (1) antifungal drug, including mode of action and example.

• Example: Azoles (e.g., Miconazole, Fluconazole)

• Mode of Action: Inhibit ergosterol synthesis, an essential component of fungal cell membranes.

Name (1) antihelminth drug, including mode of action and example.

• Example: Mebendazole

• Mode of Action: Inhibits microtubule formation in intestinal worms, blocking nutrient absorption and leading to starvation of the parasite.

Name (1) antiprotozoan drug, including mode of action and example.

• Example: Metronidazole (Flagyl)

• Mode of Action: Produces free radicals that damage DNA and other critical biomolecules within protozoa.

Name (1) antiviral drug, including mode of action and example.

• Example: Oseltamivir (Tamiflu)

• Mode of Action: Inhibits neuraminidase, preventing the release of new influenza virus particles from infected cells.

Briefly explain (4) strategies that bacteria can use to develop resistance to antimicrobial drugs.

1. Efflux Pumps: Bacteria actively pump the drug out of the cell before it can act.

2. Blocked or Altered Penetration: Changes in porins prevent drug entry.

3. Target Modification: Bacterial proteins (e.g., ribosomes or enzymes) are altered so the drug can no longer bind effectively.

4. Enzymatic Inactivation: Bacteria produce enzymes that destroy or deactivate the drug (e.g., β-lactamase deactivates penicillin).

Name and briefly describe (1) way to test the effectiveness of antimicrobials.

Kirby-Bauer Disk Diffusion Test:
Paper disks impregnated with antibiotics are placed on an agar plate inoculated with bacteria. After incubation, zones of inhibition are measured to determine susceptibility or resistance.

Read Micro Connections-Antibiograms: Taking Some of the Guesswork Out of Prescriptions. What is an antibiogram and how are antibiograms used?

• Antibiogram: A summary report showing the susceptibility of bacterial strains to different antibiotics, compiled from hospital or lab data.

• Use: Clinicians use antibiograms to guide empirical therapy—choosing antibiotics most likely to be effective against local strains—thereby improving patient outcomes and helping prevent resistance.

Distinguish between a disease and an infection.

• Infection: Occurs when a pathogen enters, colonizes, and begins to multiply in the host.

• Disease: A noticeable impairment of normal body functions caused by infection; the host shows signs and symptoms.

Distinguish between a sign and a symptom, including an example of each.

• Sign: Objective, measurable evidence of disease observed by others.

  • Example: Fever, rash, or elevated blood pressure.

• Symptom: Subjective evidence felt or reported by the patient.

  • Example: Pain, fatigue, or nausea.

Distinguish between iatrogenic disease and a nosocomial disease, including an example of each.

• Iatrogenic disease: Directly results from a medical procedure or treatment.

  • Example: Infection from contaminated surgical instruments.

• Nosocomial disease: Acquired in a hospital or healthcare setting.

  • Example: MRSA infection developed during hospitalization.

List the periods of disease and describe what is happening during each stage.

1. Incubation Period: Time between exposure and appearance of first symptoms; pathogen is multiplying, but no signs/symptoms yet.

2. Prodromal Period: Mild, nonspecific symptoms appear as pathogen load increases.

3. Period of Illness: Disease is most severe; signs and symptoms are evident, and immune response is active.

4. Period of Decline: Pathogen numbers decrease due to immune system or treatment; symptoms subside.

5. Period of Convalescence: Recovery phase; tissues heal and the body returns to normal function.

List the (3) factors that affect the duration of the period of illness. 

1. Virulence of the pathogen

2. Dose (number of pathogens introduced)

3. Host’s overall health and immune response

List Koch's Postulates. What do Koch's Postulates help to determine?

1. The suspected pathogen must be present in every case of the disease but absent from healthy individuals.

2. The pathogen must be isolated and grown in pure culture.

3. The cultured pathogen must cause the same disease when introduced into a healthy, susceptible host.

4. The same pathogen must be re-isolated from the newly diseased host.
   Purpose: To determine whether a specific microorganism causes a specific disease.

List molecular Koch's Postulates.

1. The phenotype (trait) under study should be associated with pathogenic strains.

2. Inactivation of the suspected gene(s) should reduce virulence.

3. Restoration (reintroduction) of the gene should restore pathogenicity.

Distinguish between virulence and pathogenicity.

• Pathogenicity: The ability of a microorganism to cause disease.

• Virulence: The degree or severity of pathogenicity—how harmful the pathogen is.

Distinguish between a primary pathogen and an opportunistic pathogen.

• Primary pathogen: Causes disease in a healthy host (e.g., Mycobacterium tuberculosis).

• Opportunistic pathogen: Causes disease only when the host’s defenses are weakened (e.g., Candida albicans).

List the (4) stages of pathogenesis and be familiar with what happens during each stage.

1. Exposure (Contact): Pathogen encounters host through portals of entry (e.g., respiratory tract, mucous membranes).

2. Adhesion (Colonization): Pathogen attaches to host tissues using adhesion factors.

3. Invasion: Pathogen spreads through tissues, sometimes entering cells or the bloodstream.

4. Infection: Pathogen multiplies, evades immune response, and causes damage (disease).

Name and describe (2) virulence factors for adhesion.

• Fimbriae (pili): Hairlike appendages that attach to host cell receptors (e.g., Neisseria gonorrhoeae).

• Adhesins (surface proteins or glycoproteins): Found on microbial surfaces; bind specifically to host cell receptors (e.g., E. coli adhesins bind to urinary tract cells).

Distinguish between endotoxins and exotoxins, including an example of each.

Type	Produced By	Composition	Effect/Example
Endotoxin	Gram-negative bacteria (outer membrane)	Lipopolysaccharide (LPS), specifically lipid A	Causes fever, inflammation, and shock (e.g., E. coli LPS)
Exotoxin	Gram-positive or Gram-negative bacteria	Protein	Highly specific effects, e.g., botulinum toxin (causes paralysis)

Define superantigen.

A class of exotoxin that overstimulates the immune system by activating large numbers of T cells nonspecifically, leading to excessive cytokine release and toxic shock.

Describe (2) virulence factors that help pathogens survive in the host and/or evade the immune system.

• Capsules: Prevent phagocytosis by immune cells (e.g., Streptococcus pneumoniae).

• Proteases or Enzymes: Destroy host immune molecules like antibodies (e.g., Neisseria produces IgA protease).

Distinguish between antigenic shift and antigenic drift.

• Antigenic Drift: Minor, gradual genetic mutations in viral surface proteins (e.g., influenza hemagglutinin/neuraminidase) causing seasonal variation.

• Antigenic Shift: Major, abrupt reassortment or exchange of genetic material between viral strains, creating new subtypes that can cause pandemics.

Describe the fungal virulence factor (mycotoxin) aflatoxin.

Aflatoxin: A mycotoxin produced by Aspergillus flavus; it is carcinogenic and can contaminate crops like peanuts or corn, causing liver cancer or damage.

Describe the major virulence factors of the protozoan, Giardia lamblia.

• Uses adhesive disk to attach to intestinal epithelial cells.

• Produces proteases to degrade host intestinal barriers.

• Undergoes antigenic variation of surface proteins to avoid immune detection.

Describe how helminths survive in the host and evade the host immune system.

• Coating with host molecules (e.g., proteins) to avoid recognition.

• Suppressing the immune system by releasing anti-inflammatory molecules.

• Large size makes them difficult for immune cells to destroy directly.

Read through the Clinical Focus, parts 1-3, and resolution. Be familiar with the key aspects of the disease, diagnosis, and treatment.

Disease: Clostridium difficile infection (C. diff).

• Cause: Overgrowth of C. difficile following antibiotic therapy that disrupts normal gut flora.

• Symptoms: Severe diarrhea, fever, abdominal pain, and colitis.

• Diagnosis: Detection of C. difficile toxins in stool samples.

• Treatment: Discontinue the triggering antibiotic; treat with metronidazole or vancomycin; in severe or recurrent cases, fecal microbiota transplant (FMT) may be used.

Distinguish between the field of epidemiology and the science of etiology.

• Epidemiology: The study of where, when, and how diseases occur and how they are transmitted among populations.

• Etiology: The study of the specific cause or origin (etiological agent) of a disease.

Distinguish between prevalence and incidence.

• Prevalence: The total number (or proportion) of cases of a disease in a population at a given time (both old and new cases).

• Incidence: The number or rate of new cases of a disease in a specific population over a defined period of time.

Distinguish between morbidity and mortality.

• Morbidity: Refers to illness or disease in a population (how many people are affected).

• Mortality: Refers to death caused by a disease in a population.

Distinguish between sporadic and endemic diseases.

• Sporadic disease: Occurs only occasionally and irregularly (e.g., tetanus).

• Endemic disease: Constantly present in a population or region at relatively stable levels (e.g., malaria in some tropical areas).

Distinguish between epidemic and pandemic diseases.

• Epidemic: A sudden increase in disease cases above the normal expected level in a given population (e.g., Ebola outbreak).

• Pandemic: A worldwide epidemic that affects multiple countries or continents (e.g., COVID-19, 1918 influenza).

Define etiological agent.

The etiological agent is the causative pathogen or microorganism responsible for causing a specific disease (e.g., Mycobacterium tuberculosis → tuberculosis).

Explain the role of the CDC in public health.

The CDC is the main national public health agency in the United States. It:

• Monitors and investigates infectious disease outbreaks.

• Publishes the Morbidity and Mortality Weekly Report (MMWR).

• Provides guidelines for disease prevention, vaccination, and biosafety.

Who was John Snow? Who was Florence Nightingale? What were their contributions to epidemiology?

• John Snow (1813–1858): Considered the father of epidemiology. Traced the source of a cholera outbreak in London (1854) to a contaminated water pump, demonstrating that diseases can spread through contaminated water.

• Florence Nightingale (1820–1910): Collected and analyzed data during the Crimean War showing that poor sanitation and overcrowding led to high soldier mortality. Her statistical analysis helped reform hospital sanitation practices.

Distinguish between observational studies and experimental studies. Be specific.

• Observational studies: Researchers observe subjects without intervention; can be descriptive, analytical, or cohort studies.

  • Example: Comparing infection rates in two populations with different risk factors.

• Experimental studies: Researchers manipulate variables (e.g., test a new vaccine or drug) and compare treatment vs. control groups under controlled conditions.

Define reservoir. Provide examples of living and nonliving reservoirs.

A reservoir is any habitat where a pathogen normally lives, grows, and multiplies.

• Living reservoirs: Humans (carriers), animals (zoonoses).

  • Example: Rabies in dogs, typhoid in humans.

• Nonliving reservoirs: Soil, water, or contaminated surfaces.

  • Example: Clostridium tetani in soil, Vibrio cholerae in water.

Distinguish between contact transmission, vehicle transmission, and vector transmission (2 types) of disease, including examples of each. 

Type	Definition	Examples

Contact Transmission

Spread by direct, indirect, or droplet contact.

- Direct: Touching or sexual contact (herpes). - Indirect: Contaminated objects/fomites (common cold). - Droplet: Coughing or sneezing within 1 meter (flu).

Vehicle Transmission

Disease spread through air, water, food, or bodily fluids.

Cholera (water), Salmonella (food), Tuberculosis (airborne).

Vector Transmission

Disease spread by animals (usually arthropods). Two types: 1. Mechanical: Pathogen carried on vector’s body (e.g., flies transferring Shigella). 2. Biological: Pathogen reproduces inside vector before transmission (e.g., mosquitoes transmitting Plasmodium malaria).

Explain the role of WHO in public health.

The WHO (a United Nations agency) coordinates international public health by:

• Tracking and reporting global disease outbreaks.

• Establishing international health standards.

• Supporting vaccination and eradication programs (e.g., smallpox).

• Providing emergency response and technical support to nations.

Read through the Clinical Focus, parts 1-3, and resolution. Be familiar with the key aspects of the disease, diagnosis, and treatment.

Disease: Salmonellosis outbreak.

• Cause: Salmonella enterica contamination linked to undercooked poultry or cross-contaminated food.

• Symptoms: Diarrhea, abdominal cramps, fever.

• Diagnosis: Stool culture identifying Salmonella species.

• Treatment: Usually self-limiting; rehydration therapy; antibiotics only in severe cases.

• Key concept: Traced using epidemiological methods to a contaminated food source, illustrating how disease surveillance prevents spread.

Read through the Eye on Ethics article. Be familiar with the approaches taken to stop the spread of the ZIKA virus. How is the virus spread and how dangerous is it?

• Transmission: Primarily spread by Aedes aegypti mosquitoes; also transmitted sexually, from mother to fetus, and through blood transfusions.

• Risks: Causes microcephaly and other severe birth defects in fetuses when pregnant women are infected; also linked to Guillain-Barré syndrome.

• Prevention/Ethical Measures:

  • Mosquito control (eliminating standing water, insecticide spraying).

  • Public education and travel advisories for pregnant women.

  • Research on vaccines and vector control balanced with ethical concerns about environmental impact and reproductive rights.