Download Pneumococcal Pneumonia

Lower respiratory tract
• Lungs are axenic (no normal flora)
– Pneumonia
• Described by location, pathogen or way contracted
– Pleurisy
Pneumococcal Pneumonia
• Most common bacterial pneumonia
• Causative agent
– Streptococcus pnuemoniae
• Gram positive
• Encapsulated, diplococci
• Signs and Symptoms
–
–
–
–
Cough; fever; congestion; chest pain; rust tinged sputum
Breathing becomes shallow and rapid
Skin becomes dusky due to poor oxygenation
Consolidation may occur
– Recovery is usually complete
• Most strains do not cause permanent damage to
lung tissue
– Complications
•
•
•
•
Pleural effusions
Septicemia
Endocarditis
Meningitis
• Epidemiology
– 75% of healthy individuals carry encapsulated
strain in their throat
• Bacterial rarely reach lung
• Risk of pneumonia rises when cilia destroyed
• Gram stain of sputum used for diagnosis
• Pneumococci confirmed with quelling reaction
• Bacteria that reach alveoli cause inflammatory
response
•
•
•
•
•
Adhesions
Capsule
Phosphorylocholine in cell wall
Pneumolysin (cytotoxin)
IGA proteases
• Prevention
– Pneumococcal vaccine
• Treatment
– Antibiotics successful if given early
• Penicillin (some resistance)
• Erythromycin, cephalosporin and chloramphenicol
Klebsiella Pneumonia
• Leading cause of
nosocomial pneumonia
• Causative agent
– Klebsiella pneumoniae
• Gram negative
• Encapsulated, Bacillus
• Produce mucoid colonies
• Signs and Symptoms:
– Typical pneumonia symptoms combined with
a thick, bloody sputum and recurrent chills
– Organism causes tissue death
• Leads to formation abscess in lung or other tissues
• Endotoxin can trigger shock and disseminated
intravascular coagulation
• Epidemiology
– Endogenous
– Difficult for K. pneumoniae to infect lungs of
healthy persons
• Leading causes of nosocomial death
• Also causes UTI, meningitis and wound infections
– Diagnosed with chest x-ray and sputum culture
• Prevention
– No vaccine available
– Employ good aseptic technique
• Treatment
– Antimicrobial treatment limited
• Cephalosporin combined with an aminoglycoside
• Tissue damage and release of endotoxin can cause
permanent damage to lungs
• High fatalities even with treatment
Mycoplasmal Pneumonia
• “Walking pneumonia”
– Leading pneumonia in
children
• Causative agent
– Mycoplasma
pneumoniae
• Small, pleomorphic,
Gram +
• No cell wall
• Prominent capsule
• Signs and Symptoms
– Onset is gradual
• 1-4 week incubation period
– First symptoms include
• Fever, headache, muscle pain, fatigue, sore throat
and excessive sweating
• atypical for pneumonia
• Persistent dry cough for several weeks
• Organism attaches to receptors on epithelium
– Adhesion protein
– Interferes with cilia, cells die and slough off
– Capsule protects it from phagocytosis
– Inflammation initiates thickening of bronchial
and alveolar walls
• Causes difficulty in breathing
• Epidemiology
– Spread through aerosol droplets
• Survive for long periods in secretions
– Grow slowly in culture
• 2-6 weeks for “fried egg” colonies to appear
– Diagnosis difficult
• Serological tests required
• Prevention and treatment
– No practical prevention
• Avoid crowding in schools and military facilities
• Aseptic technique
– Antibiotic treatment
• Penicillins are ineffectual (WHY?)
• Antibiotics of choice are tetracycline and erythromycin
Pertussis
• Whooping Cough
• Causative agent
– Bordetella pertussis
• Small, Gram negative
• Encapsulated, coccobacillus
• Signs and Symptoms:
– Catarrhal stage – cold symptoms (1-2 weeks)
– Paroxysmal stage – severe coughing (2-4 weeks)
•
•
•
•
Coughing followed by characteristic “whoop”
May cause vessels in eyes to rupture
Cyanosis
Vomiting, diarrhea and seizure may occur
– Convalescent phase –persistent cough (months)
• Pathogen enters respiratory tract and attaches to
ciliated cells
– Produces 2 forms of adhesions
• Colonizes upper and lower respiratory tract
– Produces numerous toxic products
• Mucus secretion increases and cilia action decreases
• Cough reflex is only mechanism for clearing
secretions
• Decreased blood flow and WBC activity
• Epidemiology
–
–
–
–
–
Spreads via infected respiratory droplets
Highly contagious
Most infectious during runny nose period
Classically disease of infants
Often overlooked as a persistent cold in adults
– High risk of secondary infections!
• Prevention
– Immunization
• Combined with Diphtheria and tetanus toxoids
• DTaP
• Treatment
– Primarily supportive
– Erythromycin may reduce infectivity if given early
Tuberculosis
• TB; Consumption
• Causative agent
– Mycobacterium
tuberculosis
• Gram positive
• Acid fast, slender
bacillus
• Cord factor
• Signs and Symptoms
– Chronic illness
– Initial symptoms:
• Minor cough and mild fever
– Progressive symptoms:
• Fatigue; night sweats; weight loss; chest pain and
labored breathing
• Chronic productive cough
– Sputum often bloody
• 3 types of tuberculosis:
– Primary TB- initial case of tuberculosis disease
– Secondary TB - reactivated
– Disseminated TB- tuberculosis involving multiple
systems
• Primary TB
– Transmitted through respiratory droplets
– Pathogens taken up by alveolar macrophages
• fusion of phagosome with lysosomes prevented
– Pathogen replicates inside macrophages slowly killing
them
– Intense immune reaction occurs
• WBCs surround infected cells and release
inflammatory chemicals
– Other body cells deposit
collagen fibers
– macrophages and lung cells
form tubercle
– Infected cells die producing
caseous (cheesy) necrosis
– Body may deposit calcium
around tubercles
• Ghon complex
– Secondary TB
• tubercle ruptures and reestablishes active infection
• More common in immunosupressed
• Leading killer of HIV+ individuals
– Disseminated TB
• Some macrophages carry pathogen through blood
and lymph to other sites of body
• Bone marrow, spleen, kidneys, spinal cord and
brain
• Epidemiology
– 1/3 of world population infected
– Annual mortality of ~ 2 million
– Estimated 10 million Americans infected
• Rate highest among non-white, elderly poor people
– Small infecting dose
• As little as ten inhaled organisms
• Not very virulent but high mortality
• Tuberculin test
• Tuberculosis antigen injected
under skin
• Injection site become red and
firm if positive
• Positive test does not indicate
active disease
• Definitive tests include sputum
samples and chest x-rays
• Prevention
– Vaccination used in other parts of the world
– Prophylactic antibacterial treatment for exposed
individuals
• Treatment
– Antibiotic treatment
• Rifampin, Isoniazid, streptomycin and ethambutol
• MDR strains
• Therapy lasts up to 6 months (DOTS)