Bacterial and Parasitic infections of the skin Flashcards
where is staph aureus carried in nonsymptomatic individuals? how is it transmitted?
in the nostrils
transmitted via direct contact or via fomites
what are the two most common bacteria to cause infections of the skin?
staph aureus and strep pyogenes (group A strep)
what part of the skin is infected by impetigo? what does it look like?
near the nostrils typically but can spread across the face, trunk and limbs
yellow crusted skin lesions
what is bullous impetigo? what bacteria causes it and how?
an impetigo infection with severe bullae present
caused by s aureus releasing exfoliatin toxin
what is the etiology of impetigo? what does a smear from the pus look like?
usually a mixture of strep and staph
smear shows gram positive cocci in clumps and/or chains
what are the properties of cultures with impetigo? which organisms do they pertain to?
s. aureus- coagulase positive, beta hemolytic, DNAse positive and salt resistant
s pyogenes- coagulase negative, beta hemolytic, bacitracin sensitive and reactive with group A antiserum
how is impetigo treated?
keep area clean and dry
mild- mupirocin ointment (OTC creams not effective)
severe- penicillinase resistant penicillins, amoxicillin with penicillinase inhibitor or cephalosporins
get sensitivity testing- unlikely to need methicillin or vancomycin
how is impetigo prevented?
cover lesions and discard dressings. isolate infected children. don’t share towels or clothing and treat carriers with mupirocin
how are piercings infected?
they are infected by biofilms with large numbers of bacteria that start by attachment of low grade pathogens from normal flora
what is the most important organism in infection of piercings and catheters?
staph epidermidis- attaches to nylon and plastic
what culture would probably be grown from an infected piercing?
gram positive cocci growing in clumps that are catalase positive, coagulase negative and non hemolytic
what is the treatment for infected piercings and catheters?
remove the infected piercing or device (just cleaning and antibiotics will not get to all of the bacteria in the biofilms)
how are infections of piercings and catheters prevented?
use gold or surgical stainless steel for piercings
change all indwelling catheters on a regular schedule
what organism causes scabies? what does the rash look like and what causes it?
sarcoptes scabei- a mite
rash is a linear lesion that itches severely caused by mites that burrow into the skin and lay eggs. host has a cell mediated hypersensitivity reaction
where does scabies infect, typically? how is it transmitted?
affects the wrists or genitals primarily. transmitted by personal contact or fomites
how is scabies diagnosed? how is it prevented and treated?
diagnosed by observation of mites in skin scrapings
prevent by changing clothes regularly and not sharing towels
treat with topical steroids for itching and permethrin to kill mites
what is an abscess? what are its forms?
a localized collection of pus (liquefied tissue)
ferunculitis (superficial infections), carbuncles (multiple fused subcutaneous abscesses), styes, and acne
what is the most common cause of skin abscess? in acne, what is another major culprit?
staph aureus
acne also has propionobacterium acnes present
what culture testing diagnoses s aureus infection?
gram positive, clustered cocci that are coagulase positive, beta hemolytic, DNAse positive and salt resistant
how are skin abscesses treated?
abscess should be drained. mupirocin ointment for mild cases and systemic antibiotics if severe or with fever (nafcillin or oxacillin)
what may be necessary before skin abscess treatment?
drug sensitivity testing may be necessary. last resort antibiotics are vancomycin or linezolid
how is acne treated?
agents to reduce the skin susceptibility as well as topical or systemic antibiotics
what public health measures are used to prevent skin abscess transmission?
remove carriers from ICUs, operating rooms and nurseries. carrier state eliminated by topical mupirocin ointment
what is scalded skin syndrome?
widespread exfoliation due to a localized infection by s aureus and its exfoliatin toxin. it causes separation between epidermal cells usually seen in newborns
what is the skin manifestation of toxic shock syndrome? what causes it?
systemic immune reaction to the super antigen TSS toxin. with sterile exfoliation lesions
what organism typically causes cellulitis and necrotizing fasciitis?
group a streptococci (strep pyogenes)
what is the etiology of cellulitis?
infections of the deep skin that spread in a diffuse manner. may be associated with lymphadenopathy, fever and bacteremia
what is necrotizing fasciitis?
a minor skin infection that becomes rapidly extensive, spreading through subcutaneous fascia with necrosis and gangrene (noncontageous)
what causes a skin infection to become necrotizing?
it produces a potent protease enzyme.
what do the cultures from a cellulitis or necrotizing fasciitis demonstrate?
usually negative. diagnose with clinical features
how is cellulitis treated? necrotizing fasciitis?
penicillin or cephalosporin
rapid surgical intervention including amputation. culture and sensitivity test for antibiotics
what is erysipelas?
a superficial cellulitis that is not well defined.
