staphylococcal and streptococcal infections

Question 1

how important are staphylococcal and streptococcal infections

Answer 1

major human pathogens

increasing incidence of invasive infection

Question 2

what type of infections are caused by staphylococcal and streptococcal bacteria

Answer 2

• 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

Question 3

what type of bacteria is staphylococcus auerus

what does it produce

where does it colonose

resistance

Answer 3

• gram +ve cocci, coagulase +ve
• produce exotoxins and form superantigens
• colonise skin and mucosa
• resistance is a problem - MRSA

Question 4

what type of bacteria is streptococcus pyogenes (GAS)

what does it produce

where does it colonise

resistance

Answer 4

• gram +ve cocci, beta haemolytic
• produce exotoxins and form superantigens
• oro-pharyngeal carriage
• resistance isn’t a problem

Question 5

types of soft tissue infections cause by staph and strep

Answer 5

cellulitis

boils/furuncles

impetigo

infected eczema

lymphadenitis

Question 6

features of staphylococcal scalded skin syndrome

Answer 6

• 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

Question 7

what is Nikolsky sign

Answer 7

when you rub over the skin if sloughs off under your hand under minimal pressure

Question 8

management of staphylococcal scalded skin syndrome

Answer 8

IV flucloxacillin

AND

IV fluids

Question 9

what organism causes scarlet fever

Answer 9

group A strep

Question 10

timeline of scarlet fever

Answer 10

1. contact w/ someone w/ group A strep or pharyngeal carriage
2. 2-5 days incubation period
3. fever, malaise, sore throat, vomiting, abdo pain, purulent tonsils, strawberry tongue, petichiae
4. 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
5. rash lasts ~7 days, develop desquamation
   6.

Question 11

management of scarlet fever

Answer 11

notifiable disease - inform public health

• phenoxymethylpenicillin (penicillin V) 10 days

Question 12

why is phenoxymethylpenicillin used in the management of scarlet fever

Answer 12

reduces duration and severity of illness by ~1 day

reduces incidence of complications - quinsy, acute rheumatic fever, post-streptococcal glomerulonephritis

reduces transmission

Question 13

complications of scarlet fever

Answer 13

• 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

Question 14

what is toxic shock syndrome

Answer 14

acute febrile illness caused by gram +ve bacteria (S. aureus and GAS)

rapidly progressing to shock and multi-organ failure

Question 15

how does TSS happen

Answer 15

superantigen from bacteria causes intense T cell stimulation

• excessive immune activation
• pro-inflammatory cytokine release (TNF alpha, IL-1, IL-2, IFN-gamma)

Question 16

case fatality from TSS

Answer 16

30-60% GAS

3-6% s. aureus

Question 17

clinical features of TSS

Answer 17

• fever
• diffuse, maculopapular, ‘sunburn’ rash
• mucosal changes - non-purulent conjunctivitis, swollen lips, strawberry tongue
• profuse diarrhoea (s. aureus)
• rapid progression to shock and multi-organ failure - tachycardia, prolonged CRT, hypotension, renal impairment, transaminitis, reduced GCS

Question 18

management of TSS

Answer 18

• ABC
• fluid resuscitation +/- inotropes
• cultures: blood, throat swabs, wounds
• IV abx: flucloxacilin + clindamycin
• IVIG - turns off toxin production
• avoid NSAIDs - increased risk of necrotising fasciitis
• surgical debridement