Opportunistic Mycoses Flashcards
Candidiasis
Most commonly encountered
Involve any anatomical structure (ability to gain access to circulation and deep tissues iatrogenic mechanism)
Increase risk: critically ill, medical and surgical ICUs
Candidiasis morphological features
Budding yeast + pseudohyphae + true hyphae + germ tube
Candidiasis pathogenicity
Human and animal reservoir
Recovered from environment, especially hospitals
Initial step is colonization of a mucocutaneous surface
- disruption of surface allows access to blood stream
- persorption via GI wall allowing direct passage into bloodstream
Candidiasis risk factors
Pregnancy, elderly, infancy
Burn, infection
Cellular immune deficiency, AIDS, chronic granulomatous disease, aplastic anemia, leukemia, lymphoma
DM, hypoparathyroidism, Addison disease
Oral contraceptives, antibiotics, steroid, chemotherapy, catheter
Candidiasis morbidity and mortality
Mucocutaneous:
Most candidiasis infections, never fatal in healthy individuals
Severe oropharyngeal and esophageal candidiasis in AIDS pts (poor oral intake, malnutrition, wasting followed by death
Candied Mia and disseminated candidiasis
30-40% mortality
Hospitalized pts
Uncommon in AIDS pts
Candidiasis clinical presentation
Cutaneous and subcutaneous: oral, vaginal, onychomycosis, dermatitis, diaper rash, balanitis
Systemic: esophagitis, pulmonary infection, cystitis, pyelonephritis, endocarditis, myocarditis, peritonitis, hepatosplenic, endophthalmitis, arthritis, osteomyelitis, meningitis, skin lesions
Cottage cheese appearance, white or yellow color
Chronic mucocutaneous: skin and mucous membranes, verrucous lesions, impaired cellular immunity, autosomal recessive trait, hypoparathyroidism, iron deficiency
Candidiasis diagnosis
Direct microscopic examination: yeast cells, pseudohyphae, true hyphae, germ tube
Culture: differentiation of species on CHROMagar, isolation of organism for subsequent species identification
Serology: Candida mannan assay
Candidiasis treatment
Cutaneous/mucocutaneous: topical antifungals Ketoconazole, Miconazole, Nystatin
Systemic: Amphotericin B, Fluconazole, Itraconazole
Chronic mucocutaneous: Amphotericin B, Fluconazole, Itraconazole
Cryptococcosis
C. neoformans: US and other temperate climates, found in soil and aged pigeon droppings
C. gattii: tropical and subtropical areas, associated with eucalyptus tree
Crucial factor is immune state, defective CMI
Inhalation, transplantation in organ transplants
Cryptococcosis pathogenesis
Transmitted by resp inhalation
Yeast spores deposited into pulmonary alveoli
Phagocytized by alveolar macrophage, capsule has antiphagocytic properties and maybe immunosuppressive
Crypptococcosis clinical presentation
Pulmonary: asymptomatic, flulike illness, or fulminant bilateral PNA
Disseminated: meningitis (severe in immunocompromised individuals, and most common cause of meningitis in immunocompromised), cryptococcoma (most common CNS presentation in immunocompetent), skin lesions
Cryptococcosis diagnosis
Direct microscopic examination: CSF, sputum, aspiration from skin lesion Detection of encapsulated budding yeast *India ink stain with CSF* Culture Serology: Detection of capsule Ag in CSF and serum by latex agglutination test
Cryptococcosis treatment
Anti-fungal therapy for meningitis and disseminated disease
Follow up critical, examination of CSF
Amphotericin B (+ Flucytosine)
Life-long fluconazole prophylaxis following primary treatment in AIDS pts with CD4 count below 50
Aspergillosis
Found in air, soil, decaying matter
Most common is A. fumigatus
Risk factors: almost always in immunosuppressed (underlying lung disease, immunosuppressive drug therapy, immunodeficiency, co-morbidities such as COPD asthma CF)
Aspergillosis clinical presentation
Allergic bronchopulmonary aspergillosis (ABPA): hypersensitivity reaction to colonization of tracheobronchial tree, occurs in conjunction with asthma and CF
Chronic necrotizing aspergillus PNA/ pulmonary aspergillosis (CNPA): subacute infection (such as recovery from TB), individual exhibits some degree of immunosuppression (lying disease, alcoholism, or long term corticosteroid therapy), progressive cavity pulmonary infiltrate
Aspergilloma: development of fungus ball (mycetoma) in preexisiting cavity in lung parenchyma, cavitary disease commonly result of TB sarcoidosis CF and emphysematous bullae, does not invade cavity wall, can cause hemoptysis
Invasive aspergillosis: rapidly progressive, often fatal infection in pts who are severely immunosuppressed or have had prolonged neutropenia, fever cough dyspnea pleurtic chest pain and sometimes hemoptysis, dissemination to other organs including CNS
Aspergillosis diagnosis
Direct microscopic examination:
Sputum, bronchoaveolar lavage, tissue
Septae hyphae and conidia in sputum, intravascular hyphae in tissue
Histopathology:
Septate hyphae that branches at ACUTE ANGLES
Culture:
Grow in absence of cycloheximide
Observation of spherical conidia, vesicles and phialides
Serology:
Rapid diagnosis of invasive aspergillosis
Enzyme immunoassay for aspergillus galactomannan Ag in serum
Aspergillosis treatment
ABPA: oral steroids
Aspergilloma: surgical resection, intraccavity treatment with Amphotericin B
CNPA: anti-fungal treatment until radiographic resolution, surgical resection if anti-fungal fail
Invasive aspergillosis (high mortality rate): surgical debridement, anti-fungal therapy (Amphotericin B, Itraconazole), decrease level of immunosuppression, filter air
Pneumocystis jiroveci Pneumonia
Most common in HIV pts at CD4 count at 200
PJP clinical presentations
Symptoms are nonspecific, flulike symptoms
With HIV more subacute indolent course and tends to present much later after several weeks of symptoms: exertional dyspnea, fever, nonproductive cough, chest discomfort, wt loss, chills, hemoptysis (rare)
Additional findings in children with severe disease include cyanosis, nasal flaring, and intercostal retractions (resembles RSV)
PJP pathophysiology
Pneumocystis attaches to and kills Type I pneumocystis and type II becomes overly abundant and damages alveolar epithelium
Serum leaks into alveoli, producing exudate with foamy/honeycomb appearance on H&E stain
Silver stain reveals holes in the exudate actually the cysts and trophozoites, which do not stain with H&E
X-ray: patchy infiltrate (ground glass appearance), the lower lobe periphery
PJP diagnosis
Silver staining cysts in bronchial alveolar lavage fluids or biopsy
A lactic dehydrogenase study is performed as part of initial workup, usually elevated in PJP
PJP treatment
DOES NOT respond to antifungal treatment
TMP-SMX
Second line: pentaminidine or dapsone + pyrimethamine
Capsofungin? Activity against beta-D glucan
Mucormycosis
Aka: Zygomycosis
Rhizopus most common
Highly ubiquitous, high levels of exposure, low virulence
Natural reservoir: air water soil
Most infections fatal
Risk factors: diabetic ketoacidosis, neutropenia and immunosuppression
Mucormycosis pathogenesis
Primary route is inhalation of sporangiospores: ingestion and traumatic inoculation, infections that start in nose and mouth
Mucoraceae are molds in environment and take on hyphal form in tissue
As spores grow, hyphae invade blood vessels -> production of infarction, necrosis, and thrombosis -> apt to spread to brain quickly
Mucormycosis clinical presentation
Rhinocerebral: progressive orbital swelling and facial cellulitis, discharge of black pus
Proptosis, ptosis, chemosis, and opthalmoplegias: involvement of cranial nerves V and VII, power entail loss of vision
Reduced conscious state: indicative of brain involvement
Differential: anthrax
Cutaneous: progressive black necrotic lesion, result of vessel invasion (characteristic of all forms of disease)
Pulmonary: nonspecific fever dyspnea and cough, individuals with malignancies and history of neutropenia
GI: nonspecific abdominal pain distension n/v, affect severely malnourished
CNS: ha, decreasing consciousness, and focal neurological symptoms (CN deficits), history of open head trauma drug use or malginancy
Mucormycosis diagnosis
Dependent of histologic findings of a biopsy of necrotic tissue
- broad based, ribbon like, nonseptate hyphae with RIGHT ANGLE BRANCHING
Culture:
Cotton candy appearance, characteristic feature of Rhizopus species (sporangium, rhizoids)
Mucormycosis Treatment
Antifungal: Amphotericin B
Surgical debridement
Immune reconstitution
High mortality rate
Fungemia
Malassezia furfur
Nosocomial infections directly related to administration of IV lipid supplements through central venous catheter
Infection subsides once lipid infusion stopped and line removed
Trichosporon species
Catheter associated in neutropenia pts (individuals with malignancies)
Antifungal therapy usually inefficient (80% mortality)
