Microbiology Flashcards
Define ‘virulence’
The ability of an organism to cause disease within a host
Name 5 virulence factors
Adhesin Impedin Invasin Aggressin Modulin
What are adhesins?
Bacterial cell surface components that help the organism stick/adhere to host tissue
What are invasins?
Enable organisms to invade host tissue
What are impedins?
Help the organism avoid the defence/immune response in host tissue
What are aggressins?
Cause direct damage to host tissue + immune cells, affecting the host’s ability to cope with disease in the future
What are modulins?
Cause indirect damage to the host by turning the immune system in on itself (host’s immune system causes damage to host tissue)
The nasal strain of Staph. aureus can protect the mucosa. True/False?
True
Staph. epidermidis can occupy up to 100% of our skin. True/False?
True
Where is the most common entry of Staph. aureus into the body?
Nasal entry
Name the 3 particularly important virulence factors of Staph. aureus disease
Fibrinogen-binding protein (adhesin)
Leukocidin (kills leukocytes)
TSST-1 (toxin)
Every strain of Staph. aureus carries every virulence factor. True/False?
False
Which 2 severe skin diseases is leukocidin associated with?
Necrotising fasciitis
Recurrent furunculosis
Leukocidin is more virulent in hospital-acquired MRSA than community-acquired. True/False?
False
Give an example of a superantigen released by MRSA
TSST-1 (toxic shock)
How exactly do superantigens avoid specific T-cell activation?
Bind to MHC II complex on the outside, i.e. not the conventional binding groove
Name 3 skin infections caused by Strep. pyogenes
Impetigo
Cellulitis
Necrotising fasciitis
How does the Lancefield system classify different subtypes of Step. pyogenes?
M-protein
M1 and M3 are predominant; M3 and M18 cause severe, invasive disease
Which 2 virulence factors are particularly important as adhesins for Strep. pyogenes disease?
Hyaluronic acid (sticky capsule) CD44 +ve keratinocytes
The bigger the capsule, the less virulent an organism is. True/False?
False
Where does impetigo usually affect?
Face
Where in the body is Strep. pyogenes normally found?
Throat
Which strain of Staph aureus commonly produces abscesses and boils, usually affecting numerous family members at once?
PVL (panton valentine leukocidin)
Which group of Strep causes throat and severe skin infections?
Group A
Which bacteria cause impetigo?
Staph aureus
Group A Strep
Which bacteria tends to cause nectrotising fasciitis?
Group A Strep (pyogenes)
What is the treatment of choice for Staph aureus?
Flucloxacillin
What is the treatment of choice for Strep pyogenes?
Penicillin
What is necrotising fasciitis?
Bacterial infection spreading under the skin into fascia
What is the nickname of necrotising fasciitis?
Flesh-eating bacterial disease
Type I necrotising fasciitis is caused by Group A Strep. True/False?
False
Type I = mixed anaerobes and coliforms
Type II = group A Strep
What is the most common skin fungal infection caused by?
Ringworm (Tinea)
Tinea pedis is another name for what?
Athlete’s foot
How is dermatophyte infection caused?
Fungus enters abraded skin and infects keratinised tissue, provoking inflammation and outward lesioning
Which organism is the most common cause of dermatophyte infection?
Trichophyton rubrum
How are small areas of dermatophyte infection treated?
Clotrimazole cream
Nail paint
How are dermatophyte scalp infections treated?
Terbinafine oral
Itraconzole oral
Which parasite causes scabies?
Sarcoptes scabiei
Incubation of the scabies parasites takes up to how long?
6 weeks
How is scabies treated?
Malathion lotion overnight Benzyl benzoate (not in children)
Chickenpox and shingles are due to which virus?
Varicella zoster
Where does varicella zoster become dormant following chickenpox?
Dorsal root ganglia of spine
Chickenpox can cause pneumonitis and encephalitis. True/False?
True
What is Ramsay-Hunt syndrome?
Reactivation of VZV in CN VII
Causes vesicles and pain in auditory canal and throat
What does herpes simplex virus cause around the mouth?
Primary gingivostomatitis
Extensive ulceration
What is the treatment of choice for varicella zoster and herpes simplex virus?
Aciclovir
Which virus tends to cause warts?
Human papilloma virus
Which treatment is effective for warts?
Salicylic acid
Which bacterium causes syphilis?
Treponema pallidum
How is syphilis treated?
Penicillin injections
