Intro to fungi (ii)
Superficial infections
limited to outermost layers of skin, hair, nails + mucosa
normally don't cause abscesses
pityriasis versicolor
caused by malassezia furfur (mould)
pigmented lesions on upper torso, neck, patchy, pale brown/pink, maculopapular, itchy
risk factors
sweating heavy
oily skin
hot humid climates
not contagious
Dx
clinical appearance
skin scrapings
wood lamp test (UV light - yellow/green immunofluorescence)
Tx
topical azoles (ketoconazole)
oral azoles (fluconazole, itraconazole)
dermatophytosis (ringworm/tinea)
caused by dermatophytes (trichophyton, epidermophtyon, microsporum)
contagious - acquired from soil/animals/other humans
specific name depending on infected body part
tinea barbae (beard)
tinea capitis (head)
tinea corporis (groin)
tinea faciei (face)
tinea manuum (hands)
tinea pedis (foot, esp between toes due to sweat)
tinea unguium (nails)
Dx
appearance
KOH (potassium hydroxide - celars debris + keratin from specimens) microscopy
culture
Tx
oral or topical terbinafine
other topical antifungals (e.g. cotrimazole)
ketolytic agents
skin candidiasis
erythema + itchy macular plaque-like lesions in warm moist folded areas of intertrigo (skin-on-skin friction - axilla, groin, perineum, under breasts)
precipitants - antibiotics, steroids, pregnancy
Dx
clinical appearance
skin scrapings
swabs
Tx
sometimes resistance occurs
topical clotrimazole or oral fluconazole
mucosal candidiasis
white patches on mucosal surface
can be oral, vaginal or oesophageal (esp in HIV)
Dx: swab for microscopy + culture
Tx: topical / oral anti fungal
systemic infection
histoplasma capsulatum
cyptococcus neoformans
invasive candidiasis
encapsulated yeast
found in bird faeces, soil, rotting vegetation
inhaled into lungs
usually no symptoms except meningitis in immunosuppressed patients
Dx
clinical suspicion
culture + antigen detection in blood + CSF
microscopy (India ink) rarely used now
dimorphic
common in N American soil (hence travel Hx NB)
lives intraceullarly in macrophages (evades immune response)
may cause
asymptomatic infection
acute/chronic resp infection resembling TB, with areas of consolidation
disseminated infection in immunosuppressed hosts (involving liver, lungs, spleen)
major disease in an immunocompromised host
4th most common BSI in hosp patients
risk factors
antibiotics
steroids
HIV +ve
chemo
transplant (solid organ or BM)
post-op
IV catheters/other devices
DM
burns
in ICU
parenteral nutrition
Dx
clinical suspicion
microscopy: dark purple cells (gram +ve large budding yeasts)
specimens: blood, tissue, sterile samples
fever
no response to antibiotics
multi-site colonisation
germ tube test
outdated
add horse/human serum (proteinaceous) + intubate -> tubes form from cells
culture
aerobic, on Sabouraud
if blue: albicans or tropicalis
if white: parapsilosis
if pink: glabrata
Invasive aspergillosis
@ risk
prolonged neutropenia (>2 wks)
transplants
HIV
DM
high dose steroids
major surgery
primary site = lung
macrophage + neutrophils would normally eradicate the spores in an immunocompetent hist
widespread destructive growth in lung tissue
invades in blood vessels + disseminates to other sites (liver, spleen kidney, CNS)
poor prognosis