Pneumonia Fungal and Viral Pathogens Flashcards
Dimorphic fungi facts
most common cause of fungal pulmonary infections; grow as yeast in human tissues and as mold in lab; infection from inhalation of spores which in the lungs differentiate into yeasts or spherules; usually asymptomatic but all can cause pneumonia
Dimorphic fungal pathogens
Blastomyces dermatitidis, Histoplasma capsulatum, Coccidioides immitis, Paracoccidioides brasiliensis
Typical clinical manifestations of Histoplasmosis
varies from asymptotic to respiratory infection characterized by fever, chills, cough, chest pain. CXR findings vary from infiltrates, mediastinal LAD to cavitary lesions. If with AIDS, severe disseminated disease can develop with pancytopenia and mouth/GI mortality
Clinical manifestations of Paracoccidioidomycosis
mild respiratory infection which can progress with dissemination and development of oral, nasal, and facial nodular ulcerated lesions and submandibular lymphadenopathy
Clinical manifestations of Coccidioidomycosis
mild influenza like illness with fever and cough (“valley fever”) (erythema nodosum can develop), with dissemination occurring in 1%, most commonly bone, meninges, skin
Clinical manifestations of Blastomycosis
asymptomatic respiratory illness, however up to 50% of patients will have cough, chest pain, sputum production, fever which most often resolves spontaneously. CXR can show lobular consolidation, multi lobar infiltrates, multiple nodules, etc. Disseminated disease can result in ulcerated granulomatous lesion of the skin, bone, GU tract, and CNS
Diagnosis of Histoplasmosis
tissue biopsy: oval yeast cells within macrophages seen; serology (complement fixation or immunodiffusion) or urinary antigen
Treatment of Histoplasmosis
Ambisome for severe disease; Itraconazole otherwise
Diagnosis of Coccidioidomycosis
Spherules seen microscopically; serology for IgM or IgG; peripheral eosinophilia is common; skin test reactivity to diagnose exposure
Treament of Coccidioidomycosis
Ambisome for persistent lung lesions or disseminated disease; for meningitis give fluconazole
Diagnosis of Paracoccidioidomycosis
Tissue biopsy shows yeast cells with multiple buds; serology for IgM and IgG
Treatment of Paracoccidioidomycosis
Several months of Itraconazole. Ambisome can be used for severe disease
Diagnosis of Blastomycosis
tissue biopsy shoes thick walled yeast cells with single broad based bud; can use serology
Treament of Blastomycosis
Itraconazole is drug of choice, but Ambisome for severe disease
Pneumocystis jiroveci
usually asymptomatic infection; important cause of pneumonia in immunosuppressed; one of leading causes of death in pts w AIDS; cysts in alveoli produce inflammatory response, resulting in frothy exudate that blocks oxygen exchange; does not invade lung tissue
Clearance of Pneumocystis
CD4+ T cells recruit monocytes and macrophages which are responsible for clearance of the organism
How is Pneumocystis pneumonia diagnosed?
finding cysts by microscopic exam of lung tissues or fluids obtained by bronchoscopy, bronchial lavage, or lung biopsy; visualization of cysts by methenamine silver, Giemsa stain, or other stains; fluorescent antibody staining; PCR on respiratory tract specimens
Treatment for PCP (Pneumocystis Carinii Pneumonia)
Trimethoprim-sulfamethoxazole. Other secondary: clindamycin/Primaquine, Atovaquone, Pentamidine
Prophylactic PCP treatment for AIDS patients
Bactrim, Dapsone, Atovaquone
Common features of Aspergillus infection
Fungus ball formation in cavities of the lung, which can produce hemoptysis; allergic infection of the bronchi that produces asthmatic symptoms and high IgE titer; causes expectoration of brownish plugs containing hyphae; invasive pneumonia producing hemorrhage, infarction and necrosis, especially in those with heme malignancies and neutropenia
Mucormycosis risk factors
opportunistic infection caused by bread mold; risk factors - DM, neutropenia, iron overload, burns/surgical wounds, corticosteroid use
Mucormycosis Transmission and infection
Transmitted by airborne spores, invade tissues (also angioinvasive) of patients with reduced host defense; causes invasive rhino cerebral sinusitis, pneumonia, and cutaneous infections
Aspergillus on biopsy and culture
characterized by septate, acute-angle branching hyphae
Mucor on biopsy and culture
Characterized by nonseptate broad hyphae with frequent right angle branching
Aspergillus treatment
Voriconazole. Ambisome or echinocandins if patient does tolerate Voriconazole. Remove the fungal balls; for ABPA use steroids and antifungals
Mucor treatment
treat underlying disorder plus Ambisome and surgical removal of necrotic infected tissue (Posaconazole can be used)
Cryptococcus neoformans facts
Yeast present in solid and pigeon shit; oval budding yeast with wide polysaccharide capsule that forms narrow-based bud; causes meningitis in immunosuppressed and pneumonia in everyone (immunocompetent will be asymptomatic)
Cytomegalovirus
DNA enveloped virus; usually asymptomatic infection; enters latent state primarily in monocytes and can be reactivated when cell-mediated immunity is decreased.
Nocardiosis
Aerobic, found in soil, thin branching filaments, gram+, many isolates are weakly acid fast
Nocardiosis infections
In immunocompromised produce lug infection and may disseminate especially to brain, causing abscesses; can cause pneumonia, lung abscess with cavity formation, lung nodules, or empyema
Nocardiosis Diagnosis
Gram stain/acid fast stain; culture
Nocardiosis Treatment
Trimethoprim-sulfamethoxazole; sometimes needs combination therapy; resistance can occur - check sensitivities.
CMV Infections
Immunosuppressed get pneumonitis. AIDS patient get colitis and retinitis, not pneumonitis
Type of pneumonia caused by pneumonia
atypical pneumonial; usually acute, febrile respiratory disease characterized by patchy inflammatory changes in the lung, usually confined to the alveolar septa and pulmonary interstitium
Features of RSV
pleomorphic, enveloped, negative-sense single-stranded, linear RNA
Diagnostic methods for RSV
Rapid antigen test or RT-PCR on nasal swab or washings
Groups at risk for RSV pneumonia
immunocompromised, institutionalized elderly, infants with chronic lung disease, infants born during RSV season and are less than 6mo, infants born before 35wks gestation
Usual course of RSV infection
usually resolves without complication; the more severe the infection the more complications particularly apnea and respiratory failure
Treatment and prevention of RSV
inhaled Ribavirin, Palivizumab, supportive care with hydration, albuterol, oxygen
Palivizumab
monoclonal antibody against F protein which prevents pneumonia caused by RSV in premature infants by neutralizing virus infectivity
Ribavirin
routine use in children is not recommended because efficacy is not proven; may be beneficial for some adults
Adenovirus
transmitted via aerosal droplet, fecal-oral, or direct inoculation; pneumonia is typically seen in infants and can be accompanied by lethargy, diarrhea, vomiting; outbreaks in military common; no treatment, diagnosed clinically
Adenovirus vaccine
live oral enteric-coated using serotypes 4&7 are used by the military; not approved for general public use
Influenza
most common cause of respiratory tract infections that result in physician visits
Populations at risk for complications from influenza
young children and elderly, chronic disease, immunosuppressed, pregnant or 2 weeks postpartum, morbidly obese, nursing home residents, native Americans and Alaskan natives
Surface proteins of influenza
hemagglutinin, which serves to attach the virus to its cellular target, and Neuraminidase, which facilitates the release of newly formed virions
Influenza transmission
transmitted by airborne respiratory droplets; virus is inhaled, gains access to respiratory cells of URT and LRT
Pathology of influenza infection
necrosis of superficial layers of the respiratory epithelium; myalgias due to circulating cytokines
Reason people are infected yearly by influenza
antigenic drift results in the emergence of new viral strands
Antigenic drift
results from random spontaneous mutations in viral genome as it replicates
Antigenic shift
results from reassortment of the genome segments encoding the HA and NA genes - generating an antigenic ally new virus with pandemic potential
Influenza diagnostic test
RT-PCR, direct fluorescent antibody, rapid viral antigen test, and viral culture (not usually used) of nasopharyngeal swab
Treatment for influenza
supportive care, Oseltamivir or Zanamivir, and antibiotics for secondary bacterial pneumonia
Who should get the influenza vaccine
everyone 6 months of age or older
Complication of influenza
Reye’s syndrome
Complication of adenovirus
bronchievtasis or brochiolitis obliterans
Complication or RSV
asthma
Reye’s syndrome
condition characterized by encephalopathy and liver degeneration; rare, life threatening complication in kids post viral infections; aspirin has been implicated in its cause
What type of virus causes SARS and what is the reservoir
Coronavirus; masked palm civet, horseshoe bat
SARS clinical presentation
China, flu like symptoms progressing to respiratory distress with tachypnea; fever, crackles bilaterally; CXR showing pneumonia with diffuse edema resulting in hypoxemia
MERS
Coronavirus of animal origin, transmitted human-to-human
MERS clinical presentation
severe illness with PNA, ARDS, AKI; fever, chills/rigors, cough, SOB, hemoptysis, sore throat, myalgias, n/v/d, abdominal pain
Hantavirus
Bunyavirus that is transmitted by aerosol inhalation of infected rodent excreta (deer mouse)
Sin Nombre Virus
most important Hantavirus in US; multiplies in pulmonary capillary endothelial cells, leading to bilateral pleural effusions with interstitial infiltrates of mononuclear cells; present with flu like symptoms, rapidly progressive SOB, pulmonary edema, thrombocytopenia, hypotension. Mortality >50%; no treatment
Human Metapneumovirus (HMPV)
major cause of more serious LRTI in children and adults; transmitted via respiratory droplets; recurrent epidemics during winter months
HMPV clinical scenario
infant with nonproductive cough, nasal congestion, rhinorrhea, fever, irritability; febrile, wheezing; infiltrates on CXR
HPIV-1 symtoms
young child with barking cough “seal-like,” and inspiratory stridor; fever, rhinorrhea, sore throat, mild respiratory distress, febrile, tachypneic, wheezing
Typical clinical presentations of parainfluenza viruses
mild upper respiratory tract infection in children and adults; Croup (laryngotracheobronchitis) in infants and young children; bronchiolitis and pneumonia in young children and infants
Parainfluenza virus
4 distinct versions; Croup is caused by 1-3; hPIV3 causes pneumonia and bronchiolitis; hPIV4 causes mild respiratory illness
PIV infection path
initially infect mucous membrane of the throat; more extensive infections will involve larynx and upper trachea
Prognosis of parainfluenza virus infection
good, most children recover after a few days; reinfection is common
