BIO205 Topic 7 - Chapters 21-23

Covering Respiratory Infections (Streptococcal Pharyngitis, Common Cold, Tuberculosis, Influenza, Coccidioidomycosis), Skin Infections (Hair follicle infections, varicella, & superficial cutaneous mycoses), & Wound Infections (pseudomonas aeruginosa, tetanus, & gas gangrene)

functions of upper respiratory tract

Filters, warms, humidifies air; mucociliary escalator removes microbes; tonsils sample microbe

functions of lower respiratory tract

Gas exchange; normally sterile due to mucociliary escalator

causative agent of strep throat

Streptococcus pyogenes (group A Strep, B-hemolytic)

symptoms of strep throat

Red throat, pus patches, tiny hemorrhages, fever, swollen lymph nodes; possible rheumatic fever, scarlet fever

pathogenesis of strep throat

Hyaluronic acid capsule; SPE toxins; Protein G Blocks IgG; M protein adhesion; protein F binds epithelial fibrin

epidemiology of strep throat

Human-only; spread by droplets/food; nasal carriers spread most; asymptomatic carriage

treatement of strep throat

Penicillin or erythromycin; no vaccine

Causative agent of common cold

>100 rhinovirus serotypes

symptoms of common cold

Malaise, scratchy throat, runny nose (watery → thick), no fever

why no antibiotics for cold?

Viral infections - antibiotics target bacteria only

Why no vaccine for cold?

Too many rhinovirus serotypes

causative agent of TB

Mycobacterium tuberculosis - acid-fast due to mycolic acid

pathogenesis of TB

Macrophage infection → lung tissue death → “cheesy” necrosis

First-line TB drug + mechanism

Isoniazid - inhibits mycolic acid synthesis

Hemagglution (H) function

Attachment to respiratory epithelial cells

Neuraminidase (N) function

Viral release from host cells

Antigenic drift vs. shift

Drift = minor mutations; Shift = major changes → pandemics

Causative agents of Valley Fever

Coccidioides immitis (dimorphic fungus)

Symptoms of Valley Fever

Flu-like: fever, cough, chest pain, weight loss

Antimicrobial aspects of skin

Dryness, saltiness, acidity, toxic lipids

3 major groups of normal skin flora

Diphtheroids, Staphylococci, Fungi (Malassezia)

Causative agent of folliculitis/furuncle/carbuncle

Staphylococcus aureus

Symptoms of S. aureus skin infections

Folliculitis → furuncle → carbuncle; redness, swelling, pus, fever

Pathogenesis of S. aureus skin infections

Coagulase, clumping factor, neutrophil plug; can spread to heart/bone/brain

Causative agent of chickenpox

Varicella-zoster virus (VZV)

Pathogenesis of VZV

Respiratory entry → bloodstream → skin; latent in nerves → shingles

Causative agents of dermatophyte infections

Epidermophyton, Microsporum, Trichophyton

Causative agent of Pseudomonas wound infections

P. aeruginosa - Gram-negative rod, produces pyoverdin (green pigment)

Epidemiology of Pseudomonas

Grows in soaps, pools, hot tubs, eyedrops, even distilled water

Causative agent of Tetanus

Clostridium tetani - anaerobic, endospore-forming

Pathogenesis of Tetanus

Tetanospasmin blocks inhibitory neurotransmitters → spastic paralysis

Causative agent of Gas Gangrene

Clostridium perfringens

Pathogenesis of Gas Gangrene

Tissue breakdown → hydrogen + CO2 gas production

Why toxin-producing wound infections are hard to treat

Toxins spread beyond wound; antibiotics don’t neutralize toxins; poor blood supply limits drug delivery

what is the production of heterophile antibody associated with?

Epstein-Barr Productive virus (infection)

which is/are associated with Coccidioidomycosis (Valley Fever)?

soil fungus AND dimorphic fungus

Tetanus prevents the release of neurotransmitters from what?

Inhibitory neurotransmitters

what does Staphylococcus aureus bind to?

Protein A