microbio lecture 21 - microbial diseases

Pyoderma

pus filled

• dead macrophages and nuetrophils that fight the infection

What causes Staphylococcal Infections?

Staphylococcus aureus through a hair follicle (folliculitis) or pimples

What is a furuncle?

deeper pus-filled infection of S. aureus called a boil

What can a further spread of the S. aureus infection lead to?

carbuncle

What do S. aureus strains do in Staphylococcal infections?

prevent movement of phagocytic cells to a site of infection & kill them

How does S. aureus cause Staphylococcal infection?

inhibiting macrophages and engulfing them ; use them to travel in the body

Is S. aureus coagulase positive or negative?

coagulase positive (most)

What does it mean to be coagulase positive?

• blood clots will form

• likes to infect and cause harm

What can S. aureus strains resist?

digestion by lysozome

How are staphylococcal infections carried?

• Hospital personnel can often spread infections since they can be asymptomatic carriers

• 50% of adults are nasal carriers

What causes impetigo?

Staphylococci or Streptococcus pyogenes

• sometimes both as a mixed infection

What is impetigo?

pyoderma lesions

• mild infection

• highly infectious

• usually not life threatening ; can give antibiotics

Who is usually affected by impetigo?

younger kids

What causes scalded skin syndrome?

Staphylococcus aureus caused by 2 different exotoxins called exfoilatins

What type of exotoxin causes scalded skin syndrome?

A-B

How are the exotoxins carried?

one is produced from a plasmid and the other is carried on the chromosome

• the toxin is carried in the circulation so all areas of the skin can be damaged by the exfoliatin

what is pemphigus neonatorum?

impetigo of the newborn caused by S. aureus

What are the virulence factors of S. aureus in scalded skin syndrome?

mobile genetic factors

• plasmid

• chromosome

What happens if skin is open from scalded skin syndrome?

vulnerable to secondary infections

What bacterium causes Toxic Shock Syndrome (TSS)?

S. aureus

Why can TSS be life threatening?

it can lead to shock and organ failure

What toxin is involved in TSS?

TSST-1 ; gets released into the circulation

What kind of exotoxin causes TSS?

superantigen = creates cytokine storm

How does the toxin work in TSS?

normally our immune system recognizes a toxin that has been released ; toxin is circulating and our immune system is responding to it ; responds in abnormal way = releases cytokines = blood vessels start leaking ; “drop in BP” leads to shock

What happens in the cytokine storm of TSS?

immune cells are meant to cause an inflammatory response, but this toxin acts as a superantigen

• superantigen = asking cells that it shouldn’t be asking non-specific abnormal response

• antigens ask for immune cell

• all the cells response to cell and release cytokines

• cytokines produce inflammatory response that is deadly

What causes streptococcal infections?

streptococcus pyogenes or group A streptococci

What does group A streptococci (GAS) cause?

strep throat

What are complications of streptococcal infection?

• scarlet fever rash

• rheumatic fever

What causes scarlet fever rash?

erythrogenic toxin that is carried on a prophage

What are the virulence factors of streptococci?

• hemolysins (wants the iron)

• streptolysin (lyses macrophages, neutrophils/immune cells)

• M protein

• capsule

• streptokinase (dissolves blood clots)

• hyaluronidase (digests the cement that holds our cells together)

• deoxyribonucleases (destroys DNA + can get around immune system again)

What are other kind involved diseases caused by S. pyogenes?

• Erysipelas

• Necrotizing Fasciitis (virulence factors allow organism to digest tissue)

• Streptococcal Toxic Shock Syndrome

What bacterium causes acne?

propionibacterium acnes

What kind of organism is Propionibacterium acnes?

anaerobic

• likes to live in our pores away from oxygen

How does acne form?

• as the sebaceous glands secrete more oil onto the skin, organisms can multiply to a greater degree since they have more nutrients (oil) for growth

• Overgrowth of the organism can lead to skin pores becoming clogged and inflamed = lead to tissue destruction

How can acne be treated?

Vitamin A derivative

• antibiotics

acne formation

overproduction of sebum gives opportunity for organism to grow better because they have more nutrients

• clog up normal pores

• immune system recognizes abnormal growth and come to the area = inflammation

What causes Pseudomonas dermatitis?

Pseudomonads

• Pseudomonas aeruginosa (gram -)

What is P. aeruginosa resistant to?

antibiotics and disinfectants

• likes to grow on soap in hospitals

P. aeruginose is a frequent cause of what?

infections in burn victims

• opportunistic infection

• starts to cut off circulation to burnt area

What does P. aeruginose make when growing in a biofilm?

endotoxin

How does P. aeruginose infect lungs of people with cystic fibrosis?

biofilm develops

• antibiotics can’t get through biofilms