2: Infections - Staphylococcal and Streptococcal Infections Flashcards
What organisms are staphylococci
Gram positive
What are the main two groups of staphylococcus
- Staphylococcus aureus
2. Staphylococcus epidermis
Is staph.a coagulase positive or negative
Positive
Is staphylococcus epidermis coagulase positive or negative
Negative
What are the three methods staphylococcus aureus can cause infection
- Direct
- Indirect toxin-mediated
- Direct toxin-mediated
What is direct effect
Due to proteases released by bacteria
What is indirect toxic-mediate
Toxins activate T-cells which release cytokines
What is a mnemonic to remember conditions staphylococcus can cause due to direct effects
BASIC POPES
Boils Abscess Septic arthritis Impetigo Cellulitus Pneumonia Osteomyelitis Peri-orbital cellulitus Endocarditis Septicaemia
What are two conditions that are indirect toxin-mediated
- Toxic shock syndrome
- Food poisoning
What condition is direct toxin-mediated
Scaled skin syndrome
What is impetigo
Superficial skin infection with Staph.aureus
What are the two types of impetigo
Primary
Secondary
What is primary impetigo
Infection of previously healthy skin
What age-group does impetigo primarily affect
2-6 years
Explain spread of impetigo
Spreads rapidly around nurseries due to being highly contagious
What is the most common cause of impetigo
Staphylococcus aureus
What can cause non-bulbous impetigo
Staphylococcus epidermis
What are 4 RF for impetigo
- Diabetes
- Immunocompromised
- Poor personal hygiene
- Atopic dermatitis
What are the two types of impetigo
Non-Bullous
Bullous
What is 70% of impetigo
Non-Bulbous
Explain clinical presentation of non-bulbous impetigo
Papules and small vesicles surrounded by erythema that rupture to give a honey yellow-coloured crust. Occurs more commonly around mouth and nose.
Regional lymphadenopathy
Explain clinical presentation of bullies impetigo
vesicles turn into large bullae that rupture to give brown crusts
What is positive in bullous impetigo
Nikolosky sign = on touching the skin it sloughs
Where does bullous impetigo tend to present
Trunk and upper extremities
When should impetigo be suspected
Child presents with honey colour crusts around lips and nose
What 3 pieces of advice should be offered for someone with impetigo
- Wash face regularly
- Do not share towels
- Avoid school 48h after all lesions crusted over
How long should someone with impetigo avoid school for
48h after all lesions crusted over
What is first line for mild impetigo
Topical fusidic acid
How long is fusidic acid given for
TDS for 5d
What antibiotic is given if impetigo is more widespread
Flucloxacillin
How long is flucloxacillin given for
7d
What is given to manage impetigo
Topic fusidic acid
Oral flucloxacillin
What is a complication of streptococcus
Post-streptococcal glomerulonephritis (Group A Strep - if caused by streptococcus )
What is cellulitus
Skin infection of deep dermis and subcutaneous tissue
What can cause cellulitus
Staphylococcus aureus
Group A staphylococcus
How does cellulitus present clinically
Poorly demarcated erythematous lesion
Can present with systemic symptoms - fever, chills, confusion
How is cellulitus classified
Eron Classification
What is Eron Class 1
- Systemically well
- No co-morbidities
What is Eron Class 2
- Systemically unwell
- Systemically well with co-morbidities
What is Eron Class 3
- Significant systemic illness
- Unstable interfering co-morbidities
- Limb threatening vascular compromise
What is Eron Class 4
Sepsis or necrotising fasciitis
How is cellulitus managed
Flucloxacillin
What is staphylococcus scalded skin syndrome
Caused by exfoliative toxin of staphylococcus aureus
What precede staphylococcal scalded skin syndrome
Mucocutaneous staphylococal aureus infection
In which age-group does staphylococcal scalded skin syndrome occur
Under 6
How does staphylococcal scalded skin syndrome present
Starts with malaise, fever and peri-oral erythema.
24-48h later:
- Flaccid easily ruptured bullae form. They rupture to show erythematous moist skin underneath.
What sign is positive in staphylococcal skin syndrome
Nikolosky sign
What is not present in staphylococcal scalded skin syndrome
Mucosal involvement
Explain pathophysiology of staphylococcal scalded skin syndrome
Staphylococcus aureus releases exfoliative toxins which cleave desmoglein 1 causing epidermal detachment
Explain how staphylococcal scalded skin syndrome is investigated
Blood Culture
Nasopharyngeal aspirate
FBC, CRP
How is staphylococcal scalded skin syndrome managed
Fluids
Antibiotics
NSAIDs for pain
How is streptococcus categorised
Depending on its ability to haemolyse blood agar it is categorised into:
- Group A streptococcus
- Group B streptococcus
What are a-haemolytic streptococci
Partially haemolyse blood-agar
What are b-haemolytic streptococci
Completely haemolyse blood-agar
Give two examples of a-haemolytic streptococci
S. pneumonia
S. viridians
What are 3 conditions streptococcus pneumonia can cause
- Otitis media
- Pneumonia
- Meningitis
What are the two types of B-haemolytic streptococci
Group A streptococcus
Group B streptococcus
What is an example of group A streptococcus
Streptococcus pyogenes
What does group A streptococcus cause
Erysipelas Impetigo Cellulitus Necrotising fasciitis Scarlet Fever Tonsillitis Post-streptococci glomerulonephritis
What is an example of Group B streptococcus
Streptococcus agalactiae
What can streptococcus agalactiae cause
Meningitis
What can streptococcus pneumonia cause
Otits media
Pneumonia
Meningitis
What can streptococcus pyogenes cause
Tonsillitis
What is scarlet fever
Infection causes by exotoxin produced by Group A, b-haemolytic streptococci
What causes scarlet fever
Toxin of streptococcus pyogenes (Group A, b-haemolytic streptococci)
When is scarlet fever most common
2-6 years
What causes transmission group A streptococcus
Respiratory droplets
Explain how scarlet fever presents
Initial phase then 12-48h later is an exanthem phase
How does the initial phase of scarlet fever present
- Malaise and Fever
- Tonsillopharyngitis: strawberry tongue, dysphagia
GI symptoms: abdominal pain and diarrhoea (more common in young children)
What is a key feature of the initial phase of scarlet fever
Strawberry tongue
Explain presentation of the exanthem phase of scarlet fever
Sand-paper like rash that starts on the torso and blanches with pressure
Where does the rash in scarlet fever spare
palms and soles
What is a feature of scarlet fever rash
pasta line = petechial rash of creases
What investigation is often performed in scarlet fever
throat swab for streptococcus pyogenes
Explain management of scarlet fever
Penicillin V
Is scarlet fever a notifiable disease
Yes
When can child return to school in scarlet fever
1d after starting antibiotics
What is the most common complication of scarlet fever
Otitis media
What are 4 complications of scarlet fever
- Otitis media
- Rheumatic fever
- Meningitis
- Post-streptococcal glomerulonephritis
When may rheumatic fever present after scarlet fever
20d
When may post-streptococcal glomerulonephritis present after scarlet fever
10d
What is post-streptococcal glomerulonephritis
Inflammation glomerulus following infection Group A streptococcus
What usually precedes post-streptococcal glomerulonephritis
- Tonsillarpharyngitis
- Impetigo
When does post-streptococcal glomerulonephritis occur
2W after infection
How will post-streptococcal glomerulonephritis present
Nephritic syndrome:
- Haematuria = Coca Cola urine
- Proteinuria
- HTN
- Oedema
- Oliguria
What is the main differential of post-streptococcal glomerulonephritis
IgA Nephropathy (presents 1-2d post infection)
How is post-streptococcal glomerulonephritis investigate
Anti-streptolysin O Titre Urinalysis U+E RFT Complement
What is present in anti-streptolysin O titre
Raised
What is prognosis of post-streptococcal glomerulonephritis
6-8W
