Pathogens with Respiratory Transmission Flashcards
Three primary bacteria discussed in this packet
Mycobacterium
Mycoplasma
Corynebacterium
Staining used for mycobacterium?
Acid-Fast
Describe the growth of mycobacteria?
Very Slow (18hours) Growth from one pole
Significance of mycobacteria growth time?
Culturing is too slow for diagnosis
mycobacterial structure associated with virulence?
Serpentine Cord Formation
Describe the mycobacterial cell wall
Made with mycolic acids (very hydrophobic
Waxy part of outer layer
Significance of mycolic acids in mycobacterium? (2)
Acid-Fastness
Prevents lysozyme or complement attack
What is Freund’s Adjuvant?
The waxy part of the outer layer of mycobacteriua
Antigenic
What is LAM? Why do we care?
Lipoarabinomannan
Stimulates cytokine production by mammalian host
TB promotes what other disease?
HIV
Symptoms of mycobacterium tuberculosis?
Fatigue, Fever, Night Sweats, Weight Loss, Hemoptysis
Primary presentation of mycobacterium tuberculosis?
Exudative lesion (edema, inflammation) Usually Unnoticed
Three potential responses to exudative lesions?
Healing
Necrotizes lung
Productive Lesion
A productive lesion will cause a _____ to occur. This can cause these two responses.
Granuloma
Encasing or Spreading (via lymph, bronchi, or blood)
Encases granulomas run the risk of
Reactivation
Leads to multiple granulomas, fibrination of lung
Mycobacterium tuberculosis spread in the blood can lead to …
Miliary TB
What is caseum?
Necrotic tissue damaged by inflammatory response and lack of vascularization
Why are caseum especially bad in mycobacterial infection?
The hollowed areas they leave behind may allow encapsulated TB to escape
Prevalence of TB?
2B people in the world infected (30%)
TB at risk populations in the US? (5)
Minorities and Immigrants Co-Existing Infection (esp. HIV) Homeless Very Young or Old Travelers in High Risk Areas
How is TB spread?
Person-to-Person via respiratory droplets
What does TB do when in the body?
Attach to alveolar macrophages and invade
Prevent Phagolysosome fusion
Cytotoxicity from cord factor
Cytokine-mediated inflammation
T or F. TB always presents with primary symptoms of the lungs.
False. Rarely primary extrapulmonary symptoms will occur.
Two sites where long term TB retention may occur.
Granulomas and Bone Marrow.
Two tests used to detect TB?
Mantoux (PPD) Test
QuantiFERON-Gold assay (IGRA)
How does a Mantoux (PPD) Test work?
Intradermal Protein Injection
Sensitivity within 72 hours indicates that Tmem cells were present
How does a QuantiFERON-Gold assay work?
Tests for releave of IFN-g from peripheral lymphocytes when exposed to TB antigen
Best method of diagnosing TB?
PCR
Two ineffective means of diagnosing TB?
Culture (too slow)
Acid-fast sputum stain (requires massive inf. to detect)
What does a IGRA+ or PPD+ patient with no symptoms and normal X ray indicate? What should you do?
Latent TB
Latent TB MUST be treated
Drug therapy commonly used to treat tuberculosis patients?
INH, Rifampin, Pyrazinamide, Ethambutol daily for 6-9 months
Drug therapy commonly used for latent TB?
Just INH
What non-chemical treatment method is important in some patients?
Directly Observed Therapy
Why might someone except to see TB+ patients very commonly in other countries?
Other parts of the world vaccinate for TB
How do you treat XDR-T patients? (3)
Meropenem + Clavulanate
Linezolid is effective, but almost always causes adverse events
Bedaquiline
Two manifestations of mycobacterium leprae?
Tuberculoid Leprosy
Lepromatous Leprosy
Describe tuberculoid leprosy (paucibacillary).
Macular Lesions
Nerves on One Side (occasional bilateral) Involved
Describe lepromatous leprosy (multibacillary)
Progressive Nodular Lesions
Bilateral Nerve Death –> Bone Resorption/Extremity Loss
Which form of leprosy is rare in the modern era
Lepromatous
Describe the skin markings seen on patients with mycobacterium leprae
Whitened, anaesthetized skin area with red ring around it
Most mycobacterium leprae cases come from what parts of the world? How is it transmitted?
Asia and Africa
Long-term contact
What organisms can have mycobacterium leprae infections?
Humans and Armadillos
Describe the pathogenesis of mycobacterium leprae.
Inflammatory disease (like TB)
Inflammation damages Nerve Endings
Hyposensitivity can cause soft tissue damage and bone loss
How do you treat mycobacterium leprae?
Dapsone (sulfone) + Rifampin
Significance of M. avium-intracellulare?
Most common hospital-acquired bacterial infection of AIDS patients
Treatment for M. avium-intracellulare?
Clarithromycin + Ethambutol for life
How does M. kansasii present?
TB-like symptoms in IC patients
Describe the physical structure of mycoplasm bacteria
Probably the smallest possible free-living entity
No Cell Wall, Membrane Only with Sterols
How do mycoplasm generate sterols?
They don’t. They take them from the host.
Describe what you would see in attempting to culture mycoplasm pneumoniae.
Grows Slowly
Tiny Colonies with Depressed centers (Fried Egg Appearance)
Describe the clinical presentation of mycoplasma pneumoniae
Mild atypical (wheeze+crackle) pneumonia
tracheobronchitis
Insidious Onset
Mild Fever + Dry Cough
How is mycoplasma pneumoniae transmitted?
Transmitted via respiratory droplets
Circumstances in which mycoplasma pneumoniae is more common.
Schoolchildren
Winter
Describe the pathogenesis of mycoplasma pneumoniae.
Proline-rich adhesion protein forms elongated tip, binds epithelial cells.
Protein M blocks the Ab Fab region
Cyotoxic Effects
List cytotoxic effects of mycoplasma pneumonia
Production of H2O2, O2-
Competition for nutrients
How is mycoplasma pneumonia
Typically don’t treat if mind
Tetracycline, Erythromycin
What drug are you a doof if you give to treat mycoplasma.
Penicilin
Mycoplasma don’t have a cell wall
Mycoplasma genetalium manifest in what three ways?
Normal Flora
Urethral Infections
Genital Infections
Manifestations of mycoplasma hominis?
10% of salphingitis
Post-partum fever
Unique metabolic activity of ureaplasma urealyticum?
Requires 10% urea to grow
Long term effect of ureaplasma urealyticum metabolism?
Generates an alkalinized environment
Causes bladder stones
Bladder stones –> Non-gonococcal urethritis in males
Describe the physical structure of Corynebacterium diphtheriae
G+ with mycolic acids in outer mem
Club Shaped
Pleomorphic
Important diagnostic test for Corynebacterium diphtheriae.
Plate on tellurite blood agar, will reduce potassium tellurite to tellurium (turn it black)
Clinical presentation of Corynebacterium diphtheriae?
Throat Infection – sore throat, fever
“Bull-Neck” – Swollen Lymph Nodes
Pseudomembrane – forms at back of throat and may obstruct airway
Toxin
Effects of Corynebacterium diphtheriae toxin?
Absorbed in blood – affects heart, liver, kidneys
How are toxigenic strains of Corynebacterium diphtheriae identified?
Elek immunodiffusion test
Filter paper with antitoxin placed perpendicular to stain streaks
Toxin and Anti-Toxin form precipitate
How is Corynebacterium diphtheriae spread?
Aerosolized droplets
When is Corynebacterium diphtheriae typically acquired?
Usually a childhood disease, most adults immune from subclinical exposure (except not really)
Mortality rate of Corynebacterium diphtheriae
10-25%
Describe the pathogenesis of Corynebacterium diphtheriae.
- AB toxin from beta-phage conversion.
- B binds EGF-like receptor and it internalized. Low pH in vesicle allows hydrolysis, frees the A
- A binds NAD and ADP, ribosylates EF-2
- NO PROTEIN SYNTHESIS
How does Corynebacterium diphtheriae work its tox genes.
High Fe turns off toxAB operon
Free Fe is kept at low levels in the body
Corynebacterium diphtheriae only releases the toxin in the body
How is Corynebacterium diphtheriae prevented?
DTaP or DPT
Booster before school and every 10 years
How is Corynebacterium diphtheriae treated?
Quarantine
Equine anti-toxin in large dose
Penicillin/Erythromycin to keep bacteria low
