micro test 3 pt.2

What are the phases of an infection?

Incubation, Prodromal, Invasion, Convalescence

What happens during each phase on infection?

1. contact to first symptoms

2. vague feelings of discomfort, \

3. acute/most severe symptoms

4. , recovery

What is infectious dose?

 Minimum number of microbes for infection

Why would a high ID be needed vs a low ID?

•  Low ID (1–10 cells) = high virulence; High ID = lower virulence.

What are the three categories of virulence factors?

• Antiphagocytic factors, Exoenzymes, and Toxins.

What are the different patterns of infection?

•  Localized, Systemic, Focal, Mixed (polymicrobial), and Primary/Secondary.

What is a source vs a reservoir?

•  Reservoir is the permanent habitat (soil, animal); Source is the immediate individual or object from which infection is acquired.

What are the most common animal vectors?

arthropods ex:  fleas, ticks, and mosquitos. While most are arthropods, larger animals can also act as vectors, such as mammals (rabies)  and lower vertebrates (e.g., in the case of salmonellosis).

What is a zoonotic disease?

an infection that is native to animals but can be transmitted to humans

prevalence equation

prevalence = total # of cases in a population / total # of people in the population

What is hantavirus?

Single-stranded RNA virus

What is its vector (hantavirus)

•  vector is rodents (via urine/feces); causes pulmonary syndrome (HPS). 38% mortality rate.

What is the iceberg effect in relation to epidemiology?

• Most cases of communicable diseases are unreported; visible "reported" cases are only a fraction of actual infections.

What is a nosocomial infection? What does this have to do with carriers?

 Hospital-acquired infections (4% of patients) often spread by Passive Carriers (healthcare workers).

Understand basic viral biology: what components do all viruses have vs. which ones

some of them have.

• All have a Capsid (protein container) and Nucleic Acid (DNA or RNA). Some animal viruses have an Envelope.

What are persistency, latency, and oncogenicity in the context of viral infections? This includes examples of each

• * Persistent: Lasts years/life (e.g., Hepatitis B).

  • Latent: Dormant, can reactivate (e.g., Herpes).

  • Oncogenic: Can cause cancer (e.g., HPV, EBV).

Understand the biology of each of the DNA viruses we discussed in class, the diseases

the cause, whether or not they can be treated.

•  Poxviruses: Enveloped, largest animal viruses. Smallpox (Variola) causes pustules; vaccine uses Vaccinia virus (Jenner).

  • Herpesviruses: All show latency and form episomes. HSV-1 (cold sores), HSV-2 (genital herpes), VZV/HHV-3 (chickenpox/shingles), EBV/HHV-4 (mono/cancers).

  • Hepadnaviruses: Hepatitis B (HBV) is the only DNA hepatitis virus; chronic infection can lead to liver cancer.

What are the different types of RNA genomes and how does each get replicated?

What are the ways to decontaminate Ebola virus in medical waste?

• Ebola: Decontaminated in medical waste using Autoclaving or Incineration.

• Erythma infectiosum: Caused by

• Parvovirus B19 (nonenveloped, single-stranded DNA).

What are the different types of RNA genomes and how does each get replicated?

Double-Stranded RNA (+dsRNA), Positive Single-Stranded RNA (+ssRNA), Negative Single-Stranded RNA (-ssRNA)

Double-Stranded RNA (+dsRNA) Replication Strategy

•  The virus uses the negative strand of the double-stranded RNA as a template to synthesize new +ssRNA.

Positive Single-Stranded RNA (+ssRNA)

• Replication Strategy

• A negative strand is first synthesized using the original positive strand as a template (via viral RNA polymerase). This negative strand then serves as the template to produce multiple daughter positive strands for the new viruses.

. Negative Single-Stranded RNA (-ssRNA)Replication Strategy:

• The virus must bring its own RNA-dependent RNA polymerase into the host cell. This enzyme replicates the -ssRNA into a +ssRNA strand.

examples of the 3 primary fungal pathogens

 Histoplasma capsulatum (Histoplasmosis), Blastomyces dermatitidis (Blastomycosis), Coccidioides immitis (Coccidiomycosis)

 Histoplasma capsulatum (Histoplasmosis)

• Basic Biology:

• Dimorphic fungus; appears as white/brown hairy mycelia at lower temps and creamy white colonies at body temp. Thrives in moist soil with high nitrogen (bird/bat droppings).

Histoplasma capsulatum (Histoplasmosis) Pattern of Infection

•  Inhaled spores (ID = 5 spores) are taken up by phagocytes (immune cells) and grow within their cytoplasm. Most cases are asymptomatic.

Histoplasma capsulatum (Histoplasmosis) Epidemiology 

Known as Ohio Valley Fever. Distributed globally but highly prevalent in the Ohio and Mississippi River valleys. 80-90% of the local population shows evidence of past infection by age 20.

 Histoplasma capsulatum (Histoplasmosis) Diagnosis

• Identified via "fish-eye" yeast visible in host macrophages from sputum or CSF samples.

 Histoplasma capsulatum (Histoplasmosis) Treatment

• Mild cases resolve on their own; systemic or chronic cases require IV amphotericin B or surgery.

 Blastomyces dermatitidis (Blastomycosis) Basic Biology

• Dimorphic; forms wrinkled, creamy white yeast colonies with large buds at 37°C. Found in forest soils, decaying wood, and animal manure.

Blastomyces dermatitidis (Blastomycosis) Pattern of Infection

•  Portal of entry is the respiratory tract (ID = 10-100 spores). It can progress from the lungs to the skin and other organs (abscesses can be mistaken for cancer or TB).

Blastomyces dermatitidis (Blastomycosis) Epidemiology

•  Found in southern Canada and the USA (Midwest, SE, Appalachia). High incidence in Wisconsin. Mortality is 8-10%, but much higher in the immunocompromised.

Blastomyces dermatitidis (Blastomycosis) Diagnosis

•  Microscopic identification of dimorphic cultures (though these take weeks to grow).

Blastomyces dermatitidis (Blastomycosis) Treatment

•  Systemic infections are treated with IV amphotericin B; mild cases are treated with azoles.

 Coccidioides immitis (Coccidiomycosis) Basic Biology:

• Known as Valley Fever. It has the greatest virulence of all fungal pathogens. At 25°C, it forms block-like spores (arthrospores); at 37°C, it forms spherical cells (spherules).

Coccidioides immitis (Coccidiomycosis) Pattern of Infection

• A single spore can cause infection. Inhaled spores convert to spherules in the lungs. It can invade bones and the CNS in 7% of cases.

Coccidioides immitis (Coccidiomycosis) Epidemiology

• Concentrated in the SW United States, Mexico, and Central/South America. Outbreaks are linked to soil disturbance (dust storms, farming).

Coccidioides immitis (Coccidiomycosis) Diagnosis

• Finding characteristic spherules in sputum, biopsies, or spinal fluid.

Coccidioides immitis (Coccidiomycosis) Treatment

•  Most patients don't require treatment; disseminated disease is treated with IV amphotericin B.

Candida auris Profile

highly drug-resistant yeast.

Candida auris is risky to

• Dangerous in hospitals and long-term care facilities.

Candida auris causes what

• Causes invasive candidiasis (fungemia), affecting the bloodstream, CNS, and internal organs.

 Candida auris can you treat

•  It is notoriously difficult to treat, with over 90% of clinical isolates resistant to fluconazole and up to 35% resistant to amphotericin B.

Mucormycosis caused by

• Caused by molds called mucormycetes found in soil and decaying matter.

Mucormycosis 3 forms

Rhinocerebral, Pulmonary, Cutaneous

Rhinocerebral is an — infection

•  Sinus and brain infection.

Pulmonary is an — infection

•  Lung infection (common in transplant/cancer patients).

Cutaneous is an — infection

• Skin infection that can occur in people with healthy immune systems after trauma (burns/surgery).

Mucormycosis Epidemiology

• Very high mortality rates, reaching 96% in disseminated cases.

 Dermatophytosis (Ringworm) caused by

•  Caused by fungi in the genera Trichophyton, Microsporum, and Epidermophyton.

Dermatophytosis (Ringworm) thrive on

•  These fungi thrive on keratin and do not typically exhibit thermal dimorphism.

Dermatophytosis (Ringworm) Symptoms

• Itchy, red, circular rashes and hair loss appearing 4–14 days after contact.

Dermatophytosis (Ringworm) Treatment

• Can be treated with generic anti-fungal powders like azoles (which prevent ergosterol synthesis).

Aspergillus causes

• Often causes respiratory issues in those with underlying lung disease.

Cryptococcus causes

•  Known for causing meningitis in immunocompromised individuals.

Pneumocystis (PJP) is

•  A frequent cause of pneumonia in AIDS patients.