Bacteria Pathogenicity Ability to Cause Infection

Bacteria Pathogenicity Ability to Cause Infection

Infectious Diseases
* Encounter-bug meets host (reservoir)
* Bug adheres to host
* Entry-bug enters host
* Multiplication- bug multiplies in host
* Damage to host
* Outcome- bug or host wins or
* Coexist- chronic infection

Reservoir
* Exposure to microbe
Virulence Factors
Adherence
* Prevent infection
* Influenza changes adhesions over time
* Neisseria gonorrhoeae -variety of adhesions

Portals of Entry
* Mucous membranes
* Conjunctiva
* Skin
* Bugs have preferred portal
* C. tetani spores in soil --- anaerobic wound

Inoculum

* Number of microbes-dose
* Greater dose, more chance infection will occur
* ID50 or LD50 expresses virulence

Invasins
* Adherence of microbe to surface
* Activates factors that let microbe in-penetration
* Microbes produce invasins (proteins)
* Endocytosis
* Requires multiplication
* Compete with normal flora for space & nutrients
* Overcome local host defenses
* Avoid IgA

Multiplication
* Need Fe to multiply
Avoid Phagocytosis
* Components of cell wall –virulence
Surviving Within Phagocyte

Tuberculosis
* Ancient disease
* 1/3 of world population infected
* 8 million develop active TB each year
* 2 million die each year
* AIDs increases activation of latent TB
* Dependent upon virulence of strain & host resistance
* Produces cell mediated immunity which prevents active disease in many people
* Multi drug resistance has developed

S & S of Pulmonary TB
* Chronic disease
* Progressive weight loss
* Night sweats
* Chronic cough
* Hemoptysis
Mycobacterium tuberculosis
* Acid fast bacillus (AFB)
* Resistant to drying
* Aerobic, slow growth
* Airborne transmission
* Inhale airborne droplets
* Ingested by alveolar macrophages
* Multiply in macrophages even with ongoing immune response

TB Response
* Host immune response-delayed type hypersensitivity reaction
* Tissue damage DT Inflammatory response
TB Conversion
* TST skin reaction is positive
* Occurs within 24 – 48 hours after exposure to TB antigens
* Purified protein derivative of bacillus
* Cell mediated immunity
* Sensitized T cells react with proteins
QuantiferonGold
* Blood test
* Detects interferon gamma

How to Confirm Diagnosis
* Sputum cultures for AFB smear & culture
* Chest xray
Pathogenesis
* LTBI (latent TB infection)
Active Disease

* Low resistance

TB Outcomes
* Primary infection- positive skin test
* 10% progressive primary infection-not controlled
Secondary or Reactivation Infection
* Reinfection-2nd exposure or
* Bacteria escape immune system-reactivation
* Activated macrophages release cytokines
* Delayed hypersensitivity reaction

Prevention of Transmission
* Negative pressure rooms
* Respirator masks-fit tested
* Admit staff aware of symptoms of TB
* Yearly TST of staff
* Conversions treated with 6-9 months of INH

Treatment
* INH for LTBI or TB conversion
* TB disease-active TB
* 9- 12 months of treatment
Resistant TB
* MDR TB
* XDR TB
* DT improper treatment

BCG
* Live culture of M. bovis
Latent vs Active
* Latent TB
* Active TB
Leprosy
* Hanson’s disease- discovered in 1873
* Seen in tropics and underserved countries
* U.S.-150 new cases per year
* Infection of nervous system
* Infects the peripheral nerves within skin
* 2 forms of disease dependent upon immune response

M. leprae
* Tuberculoid form
Lepromatous Form
* Weak immune response & microbe spreads
* Skin & nerve cells infected
* Shed large #s in nasal secretions and oozing sores-more infectious
Invasion via Enzymes
Kinases
Enzymes
Invasion via Toxins
Exotoxins
A-B Toxins
Superantigens
Naming of Exotoxins
Endotoxin
S & S
Shock
Staphylococci
S. aureus
Successful Pathogen
Biofilm
Capsule
Skin Infections
Invasion via Toxins
Toxic shock syndrome
S. aureus Intoxication
Treatment
CA-MRSA
Outbreaks in Community
PVL Gene
Preventing Transmission
Clostridium botulinum
Neurotoxin
Botulism-Foodborne Disease
Toxin
Clostridium tetani
Neurotoxin
Lockjaw
Clostridium difficile
Epidemiology
Range of Disease
Pathogenesis of CDI
New Issues
Treatment
Transmission
Environment

* Clean and disinfect surfaces in close proximity of the patient
* Patient care equipment.
* Use bleach for C. difficile
* Privacy drapes

Bacteria Pathogenicity Ability to Cause Infection.ppt