Fungi - Ew Flashcards
What two filamentous bacteria are important in human disease?
Nocardia - immunocompromised
Actinomyces - part of normal flora, immunocompetent
What is the most common cause of invasive mold infections in transplant and cancer patients?
Aspergillus
What are the main differences between yeasts and molds?
Yeasts - reproduce by budding, colonies with smooth surfaces
Moulds - branching hyphae, hairy or fuzzy appearance
What is the general treatment for opportunistic pathogens?
Prolonged therapy with or without surgical debridement
What are the basics of actinomyces?
Gram positive rods * does not stain with acid stain Lack mycolic acids Anaerobic or slightly aero tolerant Normal in GI tract and female genital tract
Why is actinomyces often missed as a diagnosis?
- Common sinuses and fistulae resemble malignancies
* it does not respect normal anatomical boundaries - spreads into adjoining organs
What are the three main clinical syndromes of actinomyces?
Orocervicofacial - poor dental hygiene or procedures, lumpy jaw, draining sulfur sinuses
Pulmonary - pneumonia with fevers chills, night sweats, weight loss - *can be confused with tb but has foul halitosis
Abdominal and pelvic infection - trauma or IUDs can cause
What is the treatment of actinomyces?
Pen g treatment of choice - IV for a few weeks then 6-12 mos oral therapy (amoxil or amoxil/clavulanic acid)
Can also use ampicillin, clindamycin, moxifloxacin, doxycycline, but not metronidazole
Surgery if needed
What are the basics of nocardia?
Obligate aerobes, gram pos rod *beaded appearance *weakly acid fast Have mycolic acids Lives in soil
What allows for nocardia to have intracellular growth?
Trehalose dimycolate cord factor
Can live within macrophages
Who does nocardia typically infect?
Those with cell mediated immune defects - steroids, lymphoma, transplant
What are the three clinical syndromes caused by nocardia?
Sub acute pneumonia - infiltrates or cavitary nodules like tb, have usually failed antibiotics
Disseminated infection in patients with pneumonia - brain abscesses, *image brain!
Cutaneous - direct inoculation, ulcers, nodules or mycetomas, pustule with fever and tender lymphadenitis
How is nocardia diagnosed?
Culture on blood agar - *tell lab to hold places longer, may take weeks
What is the treatment for nocardia?
*sulfonamides - trimethoprim-sulfamethoxazole (bactrim)
Treatment for 6-12 months
What are some common opportunistic fungi causing human disease?
Candida albicans
Aspergillus
Cryptococcus neoformans
Mucor (rhizopus)
What are the basics of Candida albicans?
Opportunistic commensal eukaryotic organism
Other types of candida more likely to be fluconazole resistant
Forms germ tubes in culture for 90 min, other Candida’s don’t
What are common clinical syndromes from candida?
Oral and vaginal thrush - can possibly be asymptomatic, affects other most surfaces
Esophagitis - dysphagia and chest pain, only if immunocompromised
Deep infections - iatrogenic introduction by procedures
Bloodstream infections - life threatening
Hepatosplenic - neutropenia patients
Rarely cause of pneumonia - usually from saliva or bronchoscope contamination
What are candida infections often preceded by antibiotic therapy?
It disrupts normal flora of mucosal surfaces
How is candida diagnosed?
*positive blood culture hardly ever represents contamination
Clinical appearance for mucosal surfaces
Culture for deep infections
What is the treatment of candida?
Oral, vaginal, skin - topical antifungals, single dose oral fluconazole for vaginal, esophagitis needs systemic Rx
Systemic - *remove medical device - amphotericin b or echinocandins or fluconazole, might be drug resistance
Azoles are fungistatic but neutropenic require fungicidal
What are the basics of cryptococcus neoformans?
Encapsulated yeast - capsule promotes survival in macrophages
Found worldwide - typically soil with bird droppings (var neoformans) or eucalyptus trees (var gattii)
Stain gram positive - esp with India ink
How can cryptococcus neoformans be distinguished from candida?
It is bigger
It doesn’t form germ tube or psuedohyphae
What is the transmission and pathogenesis of cryptococcus?
Acquiring by inhalation - lung main portal of entry
Usually asymptomatic
Spreads to brain and causes meningitis in AIDS patients
Cell mediated immunity is necessary
Melanin negative generally a virulent
What clinical syndromes are associated with cryptococcus?
Pulmonary - coin lesions that rarely cavitate
Disseminated - most commonly meninges in immunocompromised, then skin nodules
How is cryptococcus diagnosed?
*antigen testing in blood and CSF
What is the treatment of cryptococcus?
Amphotericin and 5-FU for severe
Fluconazole for mild and long term maintenance
What are the basics of aspergillus?
Ubiquitious and unavoidable in environment
Conidia extensively disseminated and inhaled
Immunocompetent can clear conidia with mucociliary clearance and phagocytic defense
What are the clinical syndromes caused by aspergillus?
Colonization of abnormal mucosal surfaces - usually asymptomatic, in those with lung diseases, aspergilloma = fungus ball - grows inside cavity from something else (can sometimes be serious)
Invasive infection - severely immunocompromised, bad prognosis
Hypersensitivy reaction - aberrant host response with TH2, difficult to control asthma
What is one special characteristic aspergillus growth in tissue?
The hyphae invade blood vessels
What is the most widely recognized risk factor for invasive aspergillosis?
Prolonged and severe neutropenia
How is aspergillus diagnosed?
*definitive diagnosis requires histology and microbiology
Hyphae at 45 degree angle
Antigen tests for galactomannan - for invasive and disseminated not local
What is the treatment of aspergillus?
*dont wait for definitive diagnosis - recovery of neutrophils function is most important
Voriconazole, then amphotericin b (terreus is resistant)
Fluconazole has no activity
How does zygomycetes grow?
*broad, ribbon like nonseptate hyphae in tissue
Twice as wide as aspergillus which is septate
What are the risk factors for zygomycetes?
Severe immunosuppression
Diabetic ketoacidosis
What are the clinical syndromes of zygomycetes?
Invasive rhino sinusitis - sinus pain, fever, nasal discharge progressing to neurologic deficits, black necrotic areas in nasal mucosa or hard palate, medical emergency
Invasive pneumonia - less common
How is zygomycetes diagnosed?
Biopsy - non septae branching at 90 degrees
What is the treatment of zygomycetes?
Immediate surgical resection
Amphotericin b
Posaconazole as salvage
Control underlying disease
What is the major host defense against histo?
Prefers to grow in alveolar macrophages
Cell mediated immune response
Interferon gamma particularly important
How is histo diagnosed?
Serologically - immunodiffusion (more specific - H and M bands) and complement fixation tests (more sensitive)
High LDH suggests dissemination
What is the treatment of histo?
Mild pneumonia may not need - resolves
Ampho b in severe
Itraconazole in mild and maintenance
How is Blasto diagnosed?
Lollipop appearance of septate hyphae
Antigen and serology cross reacts with histo
Skin test not useful
What is the treatment for Blasto?
All patients get it - high risk of dissemination
Amphotericin b in severe and CNS diseases
Intraconazole for mild
What is the treatment of coccidioidomycosis?
Uncomplicated pneumonia - questionable benefit
Diffuse pneumonia and disseminated - ampho b (intrathecally if meningitis)
Milder - itraconazole or fluconazole
Meningitis - fluconazole
Lifelong maintenance required for all patients with disseminated
What is the treatment for paracoccidioidomycosis?
Itraconazole treatment of choice
Ampho b for severe cases
Sulfa drugs but treat for longer
