Microbiology Exam 1 Study Guide: Infectious Diseases, Respiratory and Nervous System Infections

Study Guide - Smart Notes

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Opportunistic vs. True Pathogen: Opportunistic pathogens cause disease only in hosts with compromised defenses, while true pathogens can cause disease in healthy individuals.
Communicable vs. Noncommunicable Disease: Communicable diseases can be transmitted from person to person (e.g., influenza), whereas noncommunicable diseases are not spread between hosts (e.g., tetanus from soil).
Acute vs. Chronic Disease: Acute diseases have rapid onset and short duration (e.g., common cold), while chronic diseases develop slowly and persist over time (e.g., tuberculosis).
Endemic vs. Sporadic Disease: Endemic diseases are constantly present in a population (e.g., malaria in some regions), while sporadic diseases occur infrequently and irregularly.

Pandemic vs. Epidemic: An epidemic is a sudden increase in disease cases in a specific area, while a pandemic is a global outbreak affecting multiple countries or continents (e.g., COVID-19).
Emerging vs. Reemerging Disease: Emerging diseases are newly identified or increasing in incidence (e.g., Zika virus), while reemerging diseases were previously under control but are now increasing again (e.g., measles).
Herd Immunity: Occurs when a high percentage of a population is immune (via vaccination or previous infection), reducing disease spread and protecting non-immune individuals.

Incubation Period: Time between pathogen entry and symptom onset.
Prodromal Phase: Early, mild symptoms appear.
Acute Phase: Disease symptoms are most severe.
Period of Decline: Symptoms subside as the immune response controls the infection.
Convalescent Period: Recovery and return to normal health.

Note: The duration and intensity of these stages can vary by pathogen, complicating diagnosis and epidemiological tracking.

Chronic Carriers vs. Asymptomatic Carriers: Chronic carriers harbor the pathogen long-term and may shed it intermittently (e.g., Typhoid Mary), while asymptomatic carriers never develop symptoms but can transmit the disease.

Epidemiology: The study of disease distribution and determinants in populations. Primary goals: (1) Identify causes and risk factors, (2) Control and prevent disease spread.
Quarantine: Restricting movement of exposed individuals to prevent disease spread; effective for diseases with clear incubation periods and transmission routes.

Prevalence Rate: Proportion of a population with a disease at a specific time.
Incidence Rate: Number of new cases in a population over a period of time.

Formulas:

Factors Impacting Prevalence: Disease duration, recovery rate, mortality, and new case rate.
Population: Group of individuals in a defined area.
Morbidity: Rate of disease in a population.
Mortality: Rate of death due to a disease.

Healthcare-Associated Infections (HAIs): Acquired in healthcare settings; prevention includes hand hygiene, sterilization, and isolation protocols.
Community-Acquired Infections: Contracted outside healthcare facilities; prevention includes vaccination and public health measures.

Infection-Limiting Factors: Mucociliary escalator, coughing, sneezing, immune cells, and antimicrobial secretions.
Normal Flora Locations: Nasal cavity, pharynx, and upper respiratory tract.
Examples of Respiratory Flora: Streptococcus spp., Staphylococcus spp., Corynebacterium spp.

Common Terms: Rhinitis (nasal inflammation), pharyngitis (throat inflammation), sinusitis (sinus inflammation), otitis media (middle ear infection), pneumonia (lung infection).
Symptoms Comparison:

Disease	Key Symptoms
Common Cold	Runny nose, sneezing, mild sore throat, no fever
RSV	Fever, cough, wheezing, difficulty breathing (especially in infants)
HPIV	Croup (barking cough), fever, runny nose
Influenza	High fever, muscle aches, fatigue, cough, sore throat

Annual Flu Vaccines: Needed due to frequent antigenic changes (antigenic drift/shift) in influenza viruses.
No Vaccine for Colds: Caused by many virus types (mainly rhinoviruses), making vaccine development impractical.
Severe Acute Respiratory Syndrome (SARS): Caused by a coronavirus; symptoms include high fever, cough, and respiratory distress; can progress to pneumonia.
Typical vs. Atypical Pneumonia: Typical is caused by bacteria like Streptococcus pneumoniae with rapid onset and productive cough; atypical ("walking pneumonia") is often milder, caused by organisms like Mycoplasma pneumoniae.
Otitis Media in Children: Eustachian tubes are shorter and more horizontal, facilitating pathogen entry from the throat.
Diseases by Streptococcus pyogenes: Strep throat, scarlet fever, rheumatic fever.
Tuberculosis: Caused by Mycobacterium tuberculosis; forms include latent TB (no symptoms, not contagious) and active TB (symptomatic, contagious).
Typical Pneumonia Organisms: Streptococcus pneumoniae, Haemophilus influenzae, Klebsiella pneumoniae; effects include lung inflammation, fever, productive cough.

Molecular Transport: The blood-brain barrier (BBB) restricts passage of most molecules; only small, lipid-soluble substances and some nutrients (via specific transporters) can cross.

Viral vs. Bacterial Meningitis: Viral meningitis is generally milder, often self-limiting; bacterial meningitis is more severe, can be fatal without prompt treatment.
Signs and Symptoms of Polio: Fever, sore throat, headache, muscle weakness, paralysis in severe cases.
Bacterial Meningitis Pathogens: Neisseria meningitidis, Streptococcus pneumoniae, Haemophilus influenzae.
Leprosy Forms: Lepromatous leprosy is more severe, with widespread lesions and nerve damage; tuberculoid leprosy is milder, with localized skin lesions.
Tetanospasmin vs. Botulinum Toxin: Tetanospasmin (from Clostridium tetani) causes muscle spasms by blocking inhibitory neurotransmitters; botulinum toxin (from Clostridium botulinum) causes flaccid paralysis by blocking acetylcholine release. Both are contracted via wounds (tetanus) or ingestion (botulism).
Arboviruses: Transmitted by arthropods (e.g., mosquitoes); can cross the BBB and cause encephalitis (e.g., West Nile virus).
Toxoplasmosis: Caused by Toxoplasma gondii; can cause neurological symptoms, especially in immunocompromised individuals or fetuses.

Additional info: For all diseases, understanding transmission, prevention, and treatment is essential for effective control and management.