Skin and Soft Tissue Infections Flashcards
2 ways to classify soft tissue infection
by microbe
- bacteria; fungi; virus
by anatomy
- superficial; deeper tissue
basic description of S.aureus
Gram positive cocci
Clump together under light microscope
From pus from skin infection
virulence factor of S.aureus
Panton Valentine Leucocidin toxin
- PVL toxin
Attacks white cells
Punch outer cell membrane of epithelial cells
2 disease types of S.aureus
pyogenic (pus producing)
toxin mediated (signs and symptoms due to particular toxins made, e.g. endotoxins)
pyogenic disease caused by S.aureus
Boils, carbuncles
Wound infections
Abscesses
Impetigo
Mastitis
Pneumonia
Endocarditis
Bacteraemia
Osteomyelitis
toxin mediated diseases caused by S.aureus
Scaled skin syndrome
Toxic shock syndrome
Food poisoning
basic structure of S.pyogenes
e.g. Group A streptococcal infection (pus forming)
Chains (not clumps like grapes)
Gram positive
Haemolysis around colonies (white dots)
- Beta haemolysis – clearing
virulence factor of S.pyogenes
Superantigens
Present as Toxic Shock Syndrome
Production of particular antigen - Effect of it on immune system is disproportional - Bypass some of the usual controls Innocuous injury - Small amount of toxin – over react to
If don’t treat the pt quickly they will have disease progression
classic presentation/disease of S.pyogenes
cellulitis
basic description of S.anginosus
Gram positive
Chains
virulence factor of S.anginosus
intermedilysin (cytotoxin)
disease of S.anginosus
acute dental absecess
example of an anaerobe
Clostridium perfringens
basic structure of anaerobes
purple rice shaped structures (rods/bacilli)
virulence factor of anaerobes
Alpha toxin(lecithinase)
Enzyme breaks down fatty acid in outer cell membrane
- Allows infection to spread
The nagler reaction
- Coat plate with egg white, streaks across top, inhibition of lecthinase proves C.perfringens is present
example of a virus
herpes simplex group
basic structure of herpes simplex group
DNA virus
envelope around
- fried egg virus
virulence factor of herpes simplex group
cell lysis
- part of virus life cycle when activated it causes cell lysis
disease of herpes simplex group
cold sores
genital herpes
what is candida albicans
fungi
basic structure of canidida albicans
Yeast cells with hyphae
- 10 times bigger than bacteria
virulence factor of candida albicans
Phospholipase
- Breaks down phospholipids found in cell membrane
disease caused by candid albicans
Oropharyngeal candidiasis, vulvovaginal (genital) candidiasis and invasive candidiasis (candidemia)
epidermis infections are
superficial
examples of superficial epidermis infections
Impetigo and angular cheilitis (only Angle of the mouth)
- Crusted lesion
- Group A streptococci common cause
- Staph aureus also
Outbreaks can occur in nursery
- Need quick diagnosis and appropriate control
Chicken pox
- varicella-zoster virus (VZV)
Herpes zoster – shingles, reactivation in later life
- Scratchy, itchy – get secondary infections
—–Staph aureus
Herpes infection of skin used to be common occupational hazard for dentists
common cause of impetigo or angular chellitis
- Group A streptococci common cause
- Staph aureus also
clinical presentation of impetigo/angular chellitis
crusted lesion
what causes chicken pox
varicella-zoster virus (VZV)
Herpes zoster – shingles, reactivation in later life
what are the 2 secondary issues of chicken pox
Herpes zoster – shingles, reactivation in later life
Scratchy, itchy – get secondary infections
- Staph aureus
example of dermis infection
Erysipelas
Facial – butterfly rash
Common cause: group A strep
Often swab and fail to recover a pathogen
- Innocuous injury which causes widespread reaction
common cause of Erysipelas
group A strep
clinical presentation of Erysipelas
facial butterfly rash
3 diseases of hair follicles
Folliculitis
Boils (furuncle)
Carbuncles
cause of folliculitis
Staph aureus
cause of boils (furuncle)
Deeper seated infection
Staph aureus
cause of carbuncles
deeper seated infection with multiple heads in same area
staph aureus
hard to treat
disease of subcutaneous fat
cellulitis
causes of cellulitis
group A strep
staph aureus
more severe cases: - Strep pyogenes - Staph aureus - Introduce anaerobes Depends on nature and extent of minor injury - Dirty, puncture
clinical measurement tool for cellulitis
Objective marker part of medical/surgical assessment
- Edge of area of redness
Idea of spreading or receding infection
what causes severe odontogenic infections
mixture of anaerobes
disease of fascia
Necrotising fasciitis
what is Necrotising fasciitis
Combination of subcutaneous fat and tissue overlying muscles
what can occur in Necrotising fasciitis
gas gangrene
- pockets of gas and fluid produced with clostridium infection
what is the optimal treatment of Necrotising fasciitis
combination: antibiotics and debridement
- Neither will cure/manage on its own
diseases of muscle
myonecrosis
- gas gangrene too
gangrene
cause of myonecrosis
clostridium perfingens
common infection of surgical/post op wounds
staph aureus
clinical appearance of surgical/post op wounds
red
swollen
painful
possible infectors of human bite wound infection
mixed anaerobes
possible infectors of animal bite wound infections
gram negative
Pasteurella multicoda
treatment principles for soft tissue infections
History and examination
Special investigation
Record provisional and diagnosis in notes
Combination Treatment: SURGICAL DEBRIDEMENT AND ANTIBIOTICS
Need both medicine and incision and drainage to certain of pus
Review
what is Empiric prescribing
Good guess of main causative MO outside head and neck ----Group A streptococcal (S.pyogenes) -----Staph aureus ------Anaerobes Antibiotic for each
Severe od - Strep anginosus - Anaerobes Cannot take antibiotics orally IV penicillin
what is the advantage of a narrow spectrum over a broad spectrum antibiotic? (penicillin V over amoxycillin)
only work on oral flora unlike broad spectrum
- likely be less resistance
