Medically important Microorganisms Flashcards
Define a Pathogen
An organism capable of causing disease in it’s host
List the many infections in humans caused by Bacterial pathogens
–Nuisance – recovery without treatment – sore throats, food poisoning, skin infections.
–Deadly – Small chance of recovery without treatment - TB, Plague, Anthrax, MRSA, Cl. difficile
Most commonly pathogens are seen to infect?
respiratory system
nervous system
urogenital tract,
cardiovascular system
Define Pathogenesis
The mechanism by which a pathogen causes disease
Define Virulence
The relative ability of a pathogen to cause disease
Define Virulence factors
Properties of pathogens which contribute to disease
Define a Toxin
A microbial product able to cause host cell and tissue damage
How much bacteria is expelled during a sneeze?
10,000 to 100,000 bacteria
Explain the Primary infection of TB (Mycobacterium Tuberculosis)?
localised lung infection causing the production of aggregates (tubercles)may:spread (Miliary TB) - fatal or become dormant (immunity)
Explain the PostPrimary infection of TB (Mycobacterium Tuberculosis)?
reactivation related to aging, malnutrition, overcrowding, chronic infection
destruction of lung tissue, calcification, gradual spread
What is known Habitat of Streptococcus pyogenes (Sore Throat)?
Commonly isolated from upper respiratory tract and skin of adults
What is known Frequency of Streptococcus pyogenes (Sore Throat)?
Strep. pyogenes counts ~50% all throat infections (rest are viral)
What kinds of diseases can Streptococcus pyogenes cause?
Streptococcal pharyngitis - “strep throat” (tonsillitis)
severe sore throat,
enlarged tonsils (exudate),
mild fever
malaise
If untreated what can Streptococcus pyogenes lead too?
Scarlet fever - erythrogenic toxin ( exotoxin ), damages small blood vessels - rash
Explain infection with Corynebacterium diphtheriae (Diphtheria)
Usually infects children
The bacterium is inhaled and lodges in the throat and tonsils
Explain the effects of infection of Corynebacterium diphtheriae (Diphtheria)
Produce and exotoxin known as diphtheria toxin which kills the host cells.
Damaged host cells and replicated pathogen produce a Pseudomembrane
Toxin cause systemic damage to heart, kidneys and liver
A combination of partial suffocation and organ damage can prove fatal (5-10% death rate)
Explain the treatments used for Corynebacterium diphtheriae (Diphtheria).
rare in UK and USA (DTaP/Polio/Hib immunisation: Diphtheria, Tetanus, Pertussis / Polio / - Haemophilus influenzae type b )
although ~50,000 cases occur annually world wide
Penicillin, gentomycin, erythromycin
What is the Casusative Agent of Meningococcal Disease?
Neisseria meningitidis (meningococcus)
Gram -ve, encapsulated diplococcus up to 30% adults are carriers
(Bacterial / viral / fungal)
Explain transmission/Pathogenesis with central nervous system infections
airborne -> nasopharynx -> bloodstream
->bacteraemia
transient appearance of bacteria in blood
Briefly explain Meningococcemia
septicaemia (pathogens proliferate in blood) vascular coagulation shock -> death 17% cases
Briefly explain Meningitis
meninges inflammation (membranes lining the brain) death (3%)
Explain Primary syphilis
painless red ulcer, hard chancre disappears with or without treatment 4-6 weeks
Explain Secondary syphilis
-runny nose,watery eyes, aches and pains, rash on palms and soles
Explain Tertiary syphilis
- Gumma formation
- damage to large blood vessels
- eyes (blindness),
central nervous system
(madness)
