3. Lower Respiratory Tract

• acute inflammation of alevolar tissue in the lung
• 3rd cause of death worldwide, leading cause of death from infectious diseases

can be caused by all groups of organisms discussed

mucus, leukocytes and inflammatory fluid that has exited the capillaries into the lungs

scant sputum, dry cough - usually intracellular organisms

copious sputum, productive cough - extracellular growth

• gram-positive cocci in pairs
• alpha hemolytic
• pneumococcal pneumonia

• most common cause of community acquired pneumonia in people over 50
• 1/4 of people hospitalized with it die
• most common bacterial complication of influenza

respiratory route through large and medium droplets

• capsule prevents initial phagocytosis
• induces strong inflammatory response
• attachment mediated through a variety of proteins (no pili)
• can spread to other parts of boy and cause different diseases
• host produces specific antibody that opsonizes (along with C3b) and facilitates phagocytosis
• antibodies are not cross reactive - does not protect from infection from other types

• most infections are asymptomatic or mild
• when symptomatic, can cause variety of diseases - ear infection, pneumonia, bacteremia, meningitis

• rigor (shaking chill)
• high fever
• productive coughing (inflammatory fluid in lungs)
• death due to drowning in inflammatory fluid

• gram stain from sputum and sterile sites - gram+ cocci
• culture - alpha-hemolysis, catalase negative, susceptibility to optochin, bile soluble
• slide agglutination and coagulation
• DNA and RNA probes
• lab diagnosis crucial

antibiotics - resistance problem

23-valent polysaccharide vaccine - recommended for people who are older with underlying disease

13-valent polysaccharide conjugate vaccine - for young children

• about 1/3 of the world's population is infected with the bacteria
• declared global emergency, more people die of TB now than before

• mycobacterium tuberculosis
• has characteristic cell wall with a high amount of mycolic acid - acid-fast bacillus

• mostly a disease of poverty
• 13 countries responsible for 75% of world's TB cases
• rare in US

• respiratory route
• airborne in droplet nuclei
• low infectious dose
• spread by people with active disease, not subclinical carriers

• bacteria establish infection in lungs
• phagocytosed by dendritic cells and macrophages
• produce a granulomatous lesion called a tubercle
• delayed type hypersensitivity reaction -T cell mediated
• disease manifestation depends on bacterial proliferation, dissemination, and CMI response

• immune response controls infection, but doesn't clear bacteria
• person latently infected does not transmit disease

• proliferation of bacteria already in lungs (granuloma)
• usually occurs when there is deterioration in host immune function

• iceberg concept
• may form granuloma and control disease that way unless bacteria escape
• genetics, nutritional status and immune status play a role in who develops

• persistent cough
• weight loss
• weakness
• fever
• drenching night sweats
• blood coughed up from lungs
• can spread and damage other organs

• without proper diagnosis treatment is delayed
• time between onset of cough and healthcare provider, correct diagnosis, and treatment

• tuberculin skin test:
• indicates infection or exposure not active disease
• material from bacterial cell wall inject intradermally
• test measures cell mediated immune response

• interferon-gamma release assay:
• measures cytokine activity
• advantages - not affected by vaccine, less subjective, patient does not have to return
• disadvantages - needs freshly collected blood

• chest x-ray:
• determine if disease is active

staining of sputum for presence of antigen used most

rapid diagnostic for detection of TB and rifampicin resistance

• used to be sent to sanitoriums for fresh air, rest, sun
• drug therapy - resistance is problem

• multidrug-resistant TB
• extensively drug-resistant TB
• drug resistance caused exclusively by mutation targets, no horizontal gene transfer

• treatment of latent carriers - secondary prevention, prevents forming active disease
• isoniazid prophylaxis of contacts used in US as well
• treatment of people with active disease to prevent spread
• vaccine - not used in US because of skin test
• directly observed treatment short-course

infection of the respiratory tract with fungi

• histoplasma capsulatum - histoplasmosis
• coccidiodes immitis - coccidioidomycosis (valley fever)
• blastomyces dermatitidis - blastomycoses

• soil
• histoplasma capsulatum - midwestern US
• coccidiodes immitis - central valley, southwestern, northwestern mexico
• blastomyces dermatitidis - southeastern US

• by inhalation of conidia from soil
• not communicable

• inhaled conidia germinate into yeast form in the host's lungs
• innate and CMI cause grauloma formation like TB

• most people have mild or no symptoms
• small percentage of people develop severe disease, similar to TB

• skin test for H. capsulatum and C. immitis
• culture gives definitive diagnosis
• x-ray to show extent of disease
• medical history including geographic location

antifungals - severe side effects

• no successful vaccines
• modification of soil - dust control measure, cleaning up bird droppings