staphylococcal and streptococcal infections Flashcards
how important are staphylococcal and streptococcal infections
major human pathogens
increasing incidence of invasive infection
what type of infections are caused by staphylococcal and streptococcal bacteria
- majority of skin and soft tissue infections are caused by staph (s. aureus) or strep (s. pyogenes)
- both cause osteoarticular infection
- both cause bacteraemia
- both cause toxin mediated diseases - staphylococcal and streptococcal toxic shock syndrome (TSS)
can be difficult to distinguish clinically
what type of bacteria is staphylococcus auerus
what does it produce
where does it colonose
resistance
- gram +ve cocci, coagulase +ve
- produce exotoxins and form superantigens
- colonise skin and mucosa
- resistance is a problem - MRSA
what type of bacteria is streptococcus pyogenes (GAS)
what does it produce
where does it colonise
resistance
- gram +ve cocci, beta haemolytic
- produce exotoxins and form superantigens
- oro-pharyngeal carriage
- resistance isn’t a problem
types of soft tissue infections cause by staph and strep
cellulitis
boils/furuncles
impetigo
infected eczema
lymphadenitis
features of staphylococcal scalded skin syndrome
- usually <5y
-
toxin mediated - exfoliatoxin
- damage to linkage proteins in the superficial layer of the dermis
- initial bullous lesions, followed by widespread desquamation
- Nikolsky sign
- mild fever, doesn’t tend to be associated w/ significant systemic upset
- purulent conjunctivitis
what is Nikolsky sign
when you rub over the skin if sloughs off under your hand under minimal pressure
management of staphylococcal scalded skin syndrome
IV flucloxacillin
AND
IV fluids
what organism causes scarlet fever
group A strep
timeline of scarlet fever
- contact w/ someone w/ group A strep or pharyngeal carriage
- 2-5 days incubation period
- fever, malaise, sore throat, vomiting, abdo pain, purulent tonsils, strawberry tongue, petichiae
- 1-2 days after symptoms have started, confluent erythematous sandpaper rash - starts H+N then spreads through trunk to extremities (sparing of skin round mouth, palms and soles of feet) - can precede other symptoms
- rash lasts ~7 days, develop desquamation
6.
management of scarlet fever
notifiable disease - inform public health
- phenoxymethylpenicillin (penicillin V) 10 days
why is phenoxymethylpenicillin used in the management of scarlet fever
reduces duration and severity of illness by ~1 day
reduces incidence of complications - quinsy, acute rheumatic fever, post-streptococcal glomerulonephritis
reduces transmission
complications of scarlet fever
- abscess formation - retropharyngeal or peritonsillar (quinsy), OM and sinusitis, rarely meningitis
- acute rheumatic fever
- most common cause of acquired heart disease in children
- 2-3/52 after pharyngitis
- arthritis, carditis, chorea, erythema marginatum, subcutaneous nodules
- post streptococcal glomerulonephritis
what is toxic shock syndrome
acute febrile illness caused by gram +ve bacteria (S. aureus and GAS)
rapidly progressing to shock and multi-organ failure
how does TSS happen
superantigen from bacteria causes intense T cell stimulation
- excessive immune activation
- pro-inflammatory cytokine release (TNF alpha, IL-1, IL-2, IFN-gamma)
