skin and soft tissue infections Flashcards
how can infections be classified
- by microbe = bacteria, virus or fungi
- by anatomy = superficial, deeper tissues
what type of microbe is staphylococcus aureus
- bacteria
- gram positive cocci
- can cause a wide range of diseases
what is the virulence factor of staphylococcus aureus
- Panton Valentine Leukocidin (PVL) toxin
how does PVL work
- toxin that attacks the white blood cells
- works by punching holes in the outer membrane of the epithelial cells and causes the content of the cell to leak out
- can also work on polymorphs = cause all enzymes in it to be released and causes tissues atrophy
where is staphylococcus aureus most common
- nose throat and groin are most affected = 20-30% of us will carry it in these areas of our body
what are pyogenic infections caused by staphylococcus aureus
- boils, carbuncles
- wound infections
- abscesses
- impetigo
- mastitis
- pneumonia
- endocarditis
- bacteraemia
- osteomyelitis
what are toxin mediated infections caused by staphylococcus aureus
- scalded skin syndrome
- toxic shock syndrome
- food poisoning
what type of microbe is streptococcus pyogenes
- bacteria
- pus producing
- other name is Group A streptococcal infections
- gram positive
- chains rather than clump together
what is the haemolytic occurring around colonies of streptococcus pyogenes
- beta haemolysis
what is the virulence factor of streptococcus pyogenes
- superantigens causing toxic shock syndrome
why are they called super antigens
- because it is an effect on our immune system that is disproportionate to the amount of antigen present
- activates all the pathways and bypasses other control systems
what else can streptococcus pyogenes cause
- enzyme release causing skin infection, pharyngitis, otitis media
- bacteraemia causing meningitis, arthritis and osteomyelitis
- antigen causing post-streptococcal glomerulonephirits or acute rheumatic fever
how does streptococcus pyogenes cause toxic shock syndrome
- releases a super antigen that then causes cytokine release leading to toxic shock syndrome
what is a disease caused by streptococcus pyogenes
- cellulitis
- get streptococcus skin and soft tissue infections in neck
what type of microbe is streptococcus anginosus group
- bacteria
- gram positive
- chains
what is the virulence factor for streptococcus anginosus
- intermedilysin
- it is a cytotoxin
- it is produced by an anginosus group
what disease can be caused by streptococcus anginosus
- dental abscesses
what type of microbes are anaerobes
- bacteria
- gram positive
- purple rice shaped structures
- bacilli
- clostridium species is an example
what is the virulence factor of anaerobes
- alpha toxin (lecithinase)
- like an enzyme, it breaks down the outer cell membrane and allows infection to spread
what type of reaction is used to identify clostridium
- Nagler reaction
- zone of inhibition around the white streaks show that it is clostridium
what type of microbe is herpes simplex virus
- virus
- DNA virus with envelope around it
- “fried egg virus”
what is the virulence factor of herpes simplex virus
- causes lysis of other cells
what disease can be caused by herpes simplex virus
- herpes labialis
what type of microbe is Candida albicans
- fungi
- yeast cells
- they are 10 times bigger then bacteria
what is the virulence factor of Candida albicans
- phospholipase
- breaks down phospholipids in cell membrane
what disease can be caused by Candida albicans
- candidiasis
where is impetigo and angular cheilitis found
- epidermis
what is angular cheilitis and impetigo
- golden honey coloured crusted lesion
what is the common cause of impetigo and angular cheilitis
- group A streptococci and maybe sometimes staph aureus
where is the herpes simplex virus found
- epidermis
what can the herpes simplex virus cause
- chicken pox = can sometimes get secondary infection by staphylococcus due to itching of lesion
- shingles = reactivation of varicella’s (chicken pox)
- herpetic whitlow = a lesion that occurs on the tip of the finger
Where does erysipelas occur
- in the dermis
what does erysipelas show as
- a butterfly rash on the face
what is the common cause of erysipelas
- group A streptococcus is the most common
- can sometimes swab and not find any pathogen however
where are hair follicle infections
- in the dermis
what is folliculitis
- hair follicle infection
- red spots on the skin that are raised and inflamed
what is the common cause of folliculitis
- staphylococcus is important here
what are boils
- hair follicle infection
- furuncle
- red boils on the skin
- boils = furuncle deep seated infection
what is the common cause of boils
- staph aureus
what are carbuncles
- hair follicle infection
- multiple heads
- number of boils in one area
- deep hearted infection with multiple heads
- multiple deep infections of hair follicles
what is the common cause of carbuncles
- staph aureus
where does cellulitis occur
- subcutaneous fat
what does cellulitis show as
- swollen red inflamed area
why is a blue line often drawn around cellulitis
- marking for surgical and medical monitoring
- know if it is spreading or receding
what is the common cause of cellulitis
- group A streptococcus or staph aureus too
what can cellulitis cause
- the introduction of anaerobes to that area
- depends on the area and extent
what causes odontogenic infections
- streptococcus anginosus and a mixture of anaerobes cause these
where does necrotising fascitis occur
- in the fascia = in the subcutaneous fat and tissue over the muscles
what is the common cause of necrotising fascitis
- staph aureus and streptococcus pyogenes
what is the treatment of necrotising fascitis
- need to debride the area
- and need antibiotics
- need both of these for ti cure
what are a common diagnostic symptoms of necrotising fascitis
- also known as flesh eating disease
- large, dark, boil-like blisters
- pockets of gas
where does myonecrosis, gangrene occur
- muscle necrosis
- muscle
- can get abdominal wall myonecrosis from burst appendix or trauma = clostridium perfringens is the cause
what is the common cause of surgical wound infections
- healthcare associated infections
- staph aureus
what is the common cause of bite wound infections
- depends on what bites you
- human = missed anaerobes, prevotella intermedia
- animals = pasteurella multicoda
what is prevotella intermedia
- gram negative, obligate anaerobic pathogenic bacterium involved in periodontal infections and often found in acute necrotising ulcerative gingivitis
what is pasteurella multicoda
- gram negative microbe in the oral cavity of cats and dogs
- depends on the animal that bites you what you will find
what are the treatment principles
- diagnosis
- surgical debridement
- antibiotics
- review
- needs to be a combo of both debridement and antibiotics
what are the most common microbes outside of the head and neck
- staph aureus and strep pyogenes
what do you give for streptococcus anginosus and anaerobes
- give intravenous penicillin for streptococcus anginosus
- give metronidazole for anaerobes
