10.6.10 Skin infections
Normal skin has a complex endogenous microflora,
whereby disease is prevented usually by a combination
of factors, not the least of which is the physical
barrier of the skin. Disruption of this normal barrier
by a variety of means creates the potential for secondary
bacterial infection (Table 10.12). Primary bacterial
infections are much less common but may also occur.
Cytological examination is often used for a presumptive
diagnosis of bacterial skin disease. For example,
identification of intracellular cocci is typically interpreted
as a clinically relevant tentative diagnosis of
coagulase-positive staphylococcal or streptococci.
Culture is often used for severe or refractory cases.
The skin is a readily accessible site for collection of
samples, however interpretation of results can be
difficult because of the complex normal microflora,
including many potential opportunistic pathogens.
Culture of moist lesions and crusts is not typically
recommended because of the likelihood of growing
contaminants. Cultures of superficial lesions can be
taken directly from the skin but it should be remembered
that false-positive results are common. More
reliable results can be obtained from intact pustules
or furuncles if samples are collected by sterile aspiration.
As opposed to direct sampling of superficial
lesions, samples should be collected from the surface
of plaques, nodules and fistulous tracts by skin biopsy
after aseptic preparation of the site.
10.6.10 Skin infectionsNormal skin has a complex endogenous microflora,whereby disease is prevented usually by a combinationof factors, not the least of which is the physicalbarrier of the skin. Disruption of this normal barrierby a variety of means creates the potential for secondarybacterial infection (Table 10.12). Primary bacterialinfections are much less common but may also occur.Cytological examination is often used for a presumptivediagnosis of bacterial skin disease. For example,identification of intracellular cocci is typically interpretedas a clinically relevant tentative diagnosis ofcoagulase-positive staphylococcal or streptococci.Culture is often used for severe or refractory cases.The skin is a readily accessible site for collection ofsamples, however interpretation of results can bedifficult because of the complex normal microflora,including many potential opportunistic pathogens.Culture of moist lesions and crusts is not typicallyrecommended because of the likelihood of growingcontaminants. Cultures of superficial lesions can betaken directly from the skin but it should be rememberedthat false-positive results are common. Morereliable results can be obtained from intact pustulesor furuncles if samples are collected by sterile aspiration.As opposed to direct sampling of superficiallesions, samples should be collected from the surfaceof plaques, nodules and fistulous tracts by skin biopsyafter aseptic preparation of the site.
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