Opportunistic pathogens Flashcards
What are the opportunistic fungal pathogens?
- Candida spp
- mucocutaneous and cutaneous infections
- systemic infections in compromised host - Aspergillus spp
- allergic response in airways (asthma)
- systemic infections in compromised hosts - Mucomycetes
- Rhinocerebral disease (diabetics)
- Mucor spp, Rhizopus spp - Cryptococcus neoformans
- cryptococcal meningitis (AIDS) - Pneumocystis jirovecii
- pneumocystis pneumonia (AIDS)
Predisposing factors for opportunistic mycoses associated with immunosuppression? (4)
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Other predisposing factors for opportunistic mycoses? (5,6)
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What are opportunistic candida species?
- C. albicans
- C. parapsilosis
- C. tropicalis
- C. krusei
- C. Galabrata
What is the most common Candida species?
C. albicans
-forms hyphae, pseudohyphae and germ tubes
What is the second most common Candida species?
C. galabrata
-does not form hyphae, pseduohyphae or germ tubes
What is a growing concern with opportunistic/nosocomial Candida species (galabrata and krusei)?
anti fungal resistance
Where is C. albicans found?
- normal flora:
- oral cavity
- lower GI tract
- female genital tract
Most C. albicans infections are what?
- endogenous
- person to person transmission from healthcare workers skin has been documented in ICUs
When C. albicans is in normal flora, how does it present?
as a yeast
What is seen with invasive disease of C. albicans?
septated hyphae and pseudohyphae
What is a diagnostic test for C. albicans?
- germ tube test (hyphae like growth)
- when cultured in serum
- diagnostic test for this strain
What is the most common cause of fungal infections in immunocompromised individuals?
Candida
4th most common blood culture isolated in hospitals?
Candida
What is responsible for 70-80% of cases of invasive candidiasis?
- C. albicans
- C. galabrata
What makes a person high risk for Candida infection? (10)
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What must happen for someone to get hospital acquired Candidiasis?
- must be at risk
- must be exposed
What types of infections can be classified as Candidiasis?
- Cutaneous/mucocutaneous infection
- systemic infection- opportunistic pathogen, compromised host
- chronic mucocutaneous- endocrine disorders and defects in T cell immunity
Where do cutaneous/mucocutaneous infections occur? who do they effect?
- skin and nails
- oropharyngeal (trush)
- vulvovaginal (yeast infection)
- can occur in both immunocompromised and non compromised hosts
Types of systemic infections?
- UTI
- Pneumonia
- Endocarditis
- Pericarditis
- CNS infection
- Ocular infection
- Bone and joint infection
- Abdominal infection
- Hematogenous infection
Common sites of dissemination of systemic disease?
- kidney
- brain
- eye
- heart
Why are systemic infections often fatal?
because patients have underlying co-morbidities
What does anti-fungal therapy select for in Candida?
- selects for resistant strains of Candida
- C. krusei, C. glabrata
What are AIDS defining illnesses associated with Candida?
- Oral thrush
- esophageal candidiasis
How many HIV patients develop oropharyngeal candidiasis?
75%
How many AIDS patients develop esophageal candidiasis?
20-40%
How many HIV women develop vulvo vaginal candidiasis?
30-40%
What is the most common human pathogen?
- Aspergillus fumigateurs
- other species include A. flavus, A. terreus, A. niger
Where and in what form is Aspergillus species found?
- ubiquitous mold in soil and on plants and decaying vegetation
- in a hospital setting- air, shower heads, water, storage tanks, potted plants
What is sick building syndrome?
- associated with aspergillus
- conidia (spores) in the air trigger an allergic response or asthma attack
In aspergillus, where do columns of conidia form?
on top of a conidiophore
In aspergillus, conidia germinate to form what?
- branched septated hyphae
- conidial heads are rarely seen in clinical specimens except within a cavity
- hyphae are seen in tissue, distinctive acute angle branching with regularly spaced septa
Types of clinical infections of aspergillus?
- cutaneous infections
- wounds or burns - airway infections
- allergic responses to inhalation of spores
- aspergillomas (fungal balls) in dead air spaces
- obstruction of airways
- localized destructive infection of airways - invasive infection that disseminates beyond the airways
How do you get allergic aspergillosis?
- inhaled spores settle in bronchi and trigger and asthmatic reaction mediated by IgE
- Type 1 hypersensitivity reaction
What are the symptoms of allergic aspergillosis?
- rhinitis and wheezing
- intermittent fever
- productive cough
What is a more severe allergic aspergillosis response?
- antigen antibody complexes cause tissue damage (type III hypersensitivity)
- influx of neutrophils and lymphocytes
- intermittent fever and productive cough
What is typically the result of patients with allergic aspergillosis upon a skin test?
-approx 40% of patients develop hypersensitivity reaction to antigen
What types are the most serious allergic responses of allergic aspergillosis?
Type 1 and type 3 reactions in bronchi
Who are the people most likely to get allergic sinusitis?
-young adults with a history of asthma and allergies
Signs and symptoms of allergic sinusitis?
- nasal obstruction
- discharge
- headache, facial pain
- obstruction of multiple sinuses may occur
- nasal polyps (tumors on mucosal surfaces), recurrence common
What serious side effects would occur from allergic sinusitis?
-bone erosion and deformities
How is allergic sinusitis diagnosed?
-by histological findings following surgical debridement (confirmed by culture)
What is aspergilloma? where does it occur?
- fungus ball
- colonization of pulmonary cavity or dead areas of lung
- can also form in paranasal sinuses
Symptoms of aspergilloma?
- asymptomatic or productive cough
- may be slowly progressive or reactivate to invasive disease (compromised patient)
How is aspergilloma confirmed?
-chest radiographs show a mass separated from the cavity wall by an air space
Who gets obstructive bronchial aspergillosis?
- occurs in individuals with underlying pulmonary disease:
- cytic fibrosis
- chronic bronchitis
What do people develop with obstructive bronchial aspergillosis?
- bronchial casts- plugs composed of hyphae, mucus
- there is obstruction but no tissue injury
What is chronic necrotizing pulmonary aspergillosis? treatments?
- underlying structural pulmonary disease
- treated with low dose corticosteroids
- local destruction of tissue can cause inflammatory infiltrates and formation of fungus ball
- vascular invasion and dissemination does not occur
What happens during invasive aspergillosis?
- fungus actively invades lung tissue
- most severe form
Who does invasive aspergillosis occur in? what can be seen?
- occurs in most severely compromised patients
- cant contain infection so it goes systemic
- neutropenic and undergoing immunosuppressive or corticosteroid therapy
- chronic granulomatous disease- neutrophils have no respiratory burst to kill hyphae
Courses of infection of conidia?
- inhale conidia
- macrophages can kill conidia - if macrophages clear the conidia, no disease
- conidia not cleared germinate to form hyphae, macrophages can’t clear germinating conidia and hyphae
- complement activation to activate neutrophil chemotactic factors
- neutrophil can kill hyphae
- if hyphae growth is not contained by neutrophils, invasive disease occurs
- hyphae invade blood vessels
- seed other tissue (brain, liver, kidneys, spleen, GI)
- obstruction of blood vessels can cause ischemia and infarction
Summary of aspergillus infections? (28)
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Examples of Mucormycosis (Zygomycosis- molds)?
- Mucor
- Rhizopus
- Lichtheimia (formerly absidia)
- Rhizomucor
- genera of the order of Mucorales
Where is Zygomycosis found?
- ubiquitous
- common on bread and spoiled food
Properties of Zygomycosis?
- broad
- non septated hyphae
Where do Zygomycosis colonize? invade?
- colonize nasal, oropharyngeal or respiratory mucosa (inhale spores)
- they invade lumen and walls of blood vessels
Who are at high risk of invasive disease of Zygomycosis?
-Granulocytopenic and acidotic patients (especially diabetics)
Types of infections found with mucor?
- Rhinocerebral
- pulmonary
- abdominal/pelvic and GI
- primary cutaneous
- disseminated disease
Where does Rhinocerebral disease usually occur?
- occurs in acidotic diabetics
- initial infection in the nasal region
- spreads to sinuses, eye, brain and meninges
Symptoms of Rhinocerebral?
- fever
- facial pain
- headaches
- nasal congestion
- visual disturbances
- lethargy
- can be fatal within 2 weeks
Who does pulmonary disease occur in?
-occurs in patients with leukemia, severe neutropenia, or on steroid therapy
Signs and symptoms of pulmonary disease?
- bronchitis and lobular pneumonia
- fever
- productive cough with hemoptysis
- chest pain
- shortness of breath
Invasion of pulmonary disease?
- invasion of blood vessels
- destruction of lung tissue
- spreads via blood to CNS, liver, kidney, spleen, heart, skin
- necrosis, abscess formation
Who does Gastrointestinal mucormycosis occur in? what happens?
- occurs in individuals who are malnourished or have renal failure
- necrotic ulcers in stomach and colon
Who does cutaneous mucormycosis occur in? what happens?
- occurs in burn patients or as a result of disseminated disease
- usually single lesions that develop into a necrotic ulcer with dark center
Predisposing condition that leads to rhino cerebral disease?
diabetes
Predisposing condition that leads to pulmonary disease?
neutropenia
Predisposing condition that leads to cutaneous infection?
burns
Predisposing condition that leads to Gastrointestinal disease?
malnutrition
2 forms of Pneumocystis jiroveci (carnii)?
- cysts and trophs
- extracellular
Describe the cysts Pneumocystis jiroveci (carnii)?
- cysts are larger and more prevalent in clinical samples
- 8 intracystic bodies, rupture and release intracystic bodies as trophs
- trophs are haploid, split by fission or fuse and develop into cysts
How is pneumocystis jiroveci (carnii) spread?
- person to person via aerosols
- over 50% of population is seropositive by 2-4 years of age (normal flora?)
Infection of pneumocystis jiroveci (carnii) is most commonly due to what?
-reactivation or reinfection from the organism being dormant in the lung
Pneumocystis pneumonia?
- AIDS defining illness
- 80% of AIDS patients have this at some point
- was leading cause of death in AIDS patients prior to prophylaxis
- can disseminate to spleen, lymph nodes and bone marrow
Where is cryptococcus neoformans found?
- found worldwide in soil contaminated with pigeon droppings
- inhale the yeast form
- not dimorphic- always yeast
Pulmonary infection by cryptococcus neoformans?
- may be subclinical
- or mild influenza like syndrome
Disseminated infection occurs in who?
-in immunocompromised individuals
What is disseminated infection?
- AIDS defining illness
- CNS is most common site of dissemination
