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
