*H. influenza*
Gram (-) coccobacillus
Fastidious grower → chocolate agar
Encapsulated form is most invasive → polyribitol phosphate
IgA protease
Vaccine
*Strept. pneumoniae*
Gram (+) diplococci
Catalase (-)
Alpha hemolysis
Optochin sensitivity
Polysaccharide capsule (84 serotypes)
IgA protease
Bile soluble
Urine antigen test
Staph. aureus
Gram (+) cocci
IV drug users
*Pseudomonas aeruginosa*
Moist environments ie hot tub
Gram (-) rods
Oxidase (+)
Lactose (-)
MacConkey agar – clear but bluish border
Cystic fibrosis patients
*Klebsiella pneumoniae*
Enteric bacteria
Gram (-) bacillus
Blood and MacConkey agar
Lactose (+)
Endotoxin → toxic and life threatening
Capsule → difficult to treat
Legionella pneumophila
Bacillus
Organism present in artificial water environments (heating and cooling)
Transmission by inhalation
Silver stain, BCYE agar
Urine antigen test
Predisposing condition: classically organ transplant recipients
Atypical Pneumonia
*Mycoplasma pneumoniae*
Smallest free-living bacteria
No cell wall
Cold hemagglutinins – RBC clumping
ELISA
PCR
Complications: hemolytic anemia, erythema multiforme, myo/pericarditis
Readily treatable with non-beta-lactam antibiotics
Coxiella burnetii
Q fever
“rickettsia-like”
Giemsa stain
Obligate intracellular
Spore-like structures
Phase 1 and phase 2 antigens
Pneumonia and endocarditis
Streptococcus pyogenes
Gram (+) cocci
Catalase (-)
Beta hemolysis
Sensitive to bacitracin
Capsule contains hyaluronic acid and “M” protein
Toxin causes rashes and lyses RBCs
Superantigen disease
Pharyngitis → rheumatic fever + nephritis
Lysogeny
Strept antigen test, blood agar, ASO
Nocardia
Fungi-like because of hyphae
Gram (+) rod
Partially acid-fast
Cell wall contains peptidoglycan and lipid
Brain abscesses and nodular skin lesions
Cord factor (2x mycolic acids + 1 trehalose)
*Bordetella pertussis*
Gram (-) coccobacillus
Bordet-Gengou media
Catarrhal
Paroxysmal
Convalescent
Mycobacteria Tuberculosis
Granulomatous inflammation
Caseous necrosis
Facultative intracellular
Acid fast
Lowenstein-Jensen medium
Facultative intracellular – within host cells
Cell wall: mycolic acid + lipids
Does not elicit humoral response
Macrophages are primary cells infected; after 3 weeks, TH1 response (produce IFN-gamma) against organisms occurs which activates macrophages to kill the mycobacteria; TH1 response also develops the granuloma formation and necrosis: hypersensitivity response leads to tissue destruction
Histoplasma capsulatum
Fungus
Inside histiocyte (macrophages are target of infection)
Fibrocaseous (“tree bark”) nodule
Inhalation of dust particles from soil with bird or bat droppings which contain infectious spores
Latent primary lung involvement, primary usually self limited (may see “coin lesion” on CXR)
Secondary, chronic, progressive lung disease localized to apices with cough, fever, night sweats; local lesions in extrapulmonary sites
Blastomyces dermatidis
Fungus
Broad-base budding
Multiple nuclei
Soil, dimorphic fungus
Pulmonary blastomycosis – abrupt illness, productive cough, headache, chest pain, weight loss, fever, abdominal pain, night sweats, chills, anorexia
Suppurative granulomas
Macrophages have limited ability to ingest/kill organisms
Neutrophils recruited
Disseminated and primary cutaneous forms also exist
Coccidioides immitis
Valley fever
Necrotizing granuloma
Delayed type hypersensitivity to inhaled fungus
SW and Western US
Majority of primary infections are asymptomatic; 10% develop lung lesions, fever, cough, pleuritic pain, erythema nodosum or erythema multiforme (San Joaquin valley fever complex)
Pneumocystis jiroveci
Extracellular pathogen
Interstitial plasma cell pneumonia
Mild thickening of the aveolar septa → fibrosis
Alveoli fill with foamy vacuolated material
Aspergillus
Close-packed, branching, septate hyphae
Can invade blood vessels
Cryptococcus Neoformans
Pneumonia because infection acquired via the respiratory tract
Clear capsule surrounding the pale blue nucleus
CMV
Large cytomegalic cells
Enlarged nuclei and purple intranuclear inclusion surrounded by a clear halo
Picornaviruses
1. Enteroviruses
2. Rhinoviruses
Enteroviruses
Coxsackievirus
Spherical/icosahedral, naked
(+) ssRNA genome
Nucleocapsid (VP1 – VP4)
Transmission
Stool/respiratory secretions
Clinical Presentation (Hand, Foot & Mouth Disease; Type A)
Rash
Non-specific fever
Headache
herpangina (vesicular pharyngitis)
Complications
Aseptic meningitis
Myocarditis/pericarditis
Paralytic disease
Encephalitis
Treatment
Fluids
Acetaminophen
Pooled Ig for CNS disease
Rhinoviruses
Replicate optimally at 33 C
Acid labile
Human-only reservoir
Transmission
Person-to-person via respiratory droplets
Infection via nasal epithelium (ICAM-1)
Confined to upper respiratory tract
Clinical Presentation
Sneezing, nasal discharge, nasal obstruction
Sore throat, cough, headache
Complications
Bacterial sinusitis
Bacterial otitis media
Asthma exacerbations in children
Chronic bronchitis exacerbations
Treatment
Antihistamines
NSAIDs
Decongestants (vasoconstrictors)
Cough suppressants (narcotics)
Adenoviruses
Large, naked icosahedral shape
dsDNA genome
57 serotypes (7 association with respiratory illnesses)
Transmission
Respiratory, water-borne, fomite, fecal-oral
incubation period of 2-9 days
Clinical Presentation
Respiratory illness
Common cold symptoms
Pneumonia
Gastroenteritis
Replication Cycle
Attachment/entry: spike proteins (CAR/coxsackie-adenovirus receptor)
Uncoating
Early transcription: regulatory proteins to suppress INF-α & MHC type I
Late transcription: substrates & machinery
Genome replication + assembly → exit → cell lysis
Diagnosis
PCR
Immunofluorescence tests
Tissue culture
Influenza virus
Segmented
(+) ssRNA genome
Hemagglutinin spike protein: binds to enter host cell
Neuraminidase spike protein: binds to exit host cell
antigenic drift: spontaneous mutations in viral genome → reassortment → new virus
A: variety of hosts (associated with pandemics)
B: human hosts only
Transmission
coughing, sneezing, talking
Clinical Presentation
Acute respiratory disease, runny nose, fatigue, myalgia, fever, vomiting, diarrhea
Complications
ear infections, sinusitis, bronchitis, pneumonia, exacerbations of asthma + CHF
Diagnosis
RT-PCR
Treatment
Adamantine
Neuraminidase inhibitors (oseltamivir, zanamivir, peramivir)
Interferons, IgA
Coronavirus
Paramyxoviruses
Diagnosis
RT-PCR
↑IgE
Treatment
Ribavirin
Other Viruses:
Parainfluenza virus
Measles virus
Mumps virus
Respiratory Syncytial Virus
Highly infectious
(-) ssRNA genome
Bronchiolitis, pneumonia
Transmission
Respiratory droplets + contact
Clinical Presentation
Incubation period 3-5 days
Bronchiolitis (distinct clinical syndrome)
Herpes virus