Lower respiratory tract bacteria Flashcards
describe bacterial pneumonia
= inflammation of the lung as a result of bacterial infection
General features:
- fever, malaise, cough, pleuritic chest pain, dyspnea and potentially sputum production
- Sputum = rust-colored, currant-jelly, purulent, mucoid, foul-smelling
- Crackles (crepitations/rales) upon auscultation (common for TYPICAL, less common for atypical)
- Often secondary to viral respiratory tract infections
Describe the pathogenesis of bacterial pneumonia
1) bacteria enter small airways or alveoli and grow in rich lung environment to produce virulence factors
2) Local effects due to inflammatory immune response to bacteria cause irritation, pain, dyspnea
3) accumulation of fluid, bacteria, neutrophils and fibrin leads to consolidation or infiltrate that is seen as opacity on chest X-ray
Describe the bacteria involved in Typical or lobar pneumonia
Streptococcus pneumoniae Staphylococcus aureus Haemophilus influenzae *Most Gram-negative bacteria* cause consolidation in one lobe of the lung (seen on chest x-ray)
Describe the bacteria involved in Atypical or Patchy pneumonia
Mycoplasma pneumoniae
chlamydophila pneumoniae
Legionella pneumophila
–> cause patchy consolidation throughout the whole lung. (grow in a web work appearance)
Describe the clinical symptoms of Typical Pneumonia vs Atypical _____ vs _____
- Onset: Sudden vs Gradual
- Facies (looks): Toxic vs Well (walking pneumonia)
- Cough: Productive vs Nonproductive
- Sputum: purulent (bloody) vs scant, watery
- Temp.: 103-104 vs less than 103
- consolidation: Frequent vs rare
- WBC count: Elevated with left shift (mostly neutrophils) vs normal or elevated (no neutrophils)
- Common Cause: streptococcus pneumoniae vs mycoplasma pneumoniae
describe pathology of typical pneumoniae
bacteria enter alveoli and causing inflammatory response damaging the alveoli wall that leads to pus/ fluid build up in the entire lobe of the lung
What are the complications of pneumonia
- Pleural effusion = sterile effusion in the pleural space
- Hematologic = anemia with chronic pneumonia, disseminated intravascular coagulation, thrombocytopenia
- Chronic complications = decreased arterial pO2, weight loss and muscle atrophy, bronchiectasis (irreversible dilation of the bronchi and bronchioles.
Describe Aspiration Pneumonia
= introduction of foreign material into the bronchial tree (usually fluid like saliva, food, nasal secretions etc)
- carry bacteria in
- large volume of liquid dilutes/ prevents proper host response and clearance
Associated with alcoholics, coma patients, and stroke patients
Secondary bacterial pneumonia
Define Community acquired pneumonia (CAP) vs hospital acquired pneumonia (HAP)
CAP = any pneumonia not acquired in a healthcare setting
HAP = nosocomial, acquired in a health-care setting
- immunocompromised, associated w/ ventilator use (VAP)
- frequently caused by MDR gram-negatives
Describe labs that could be representative of pneumoniae
CBC: elevated WBC; “left shift” = increase in immature neutrophils = typical bacterial pathogens
Blood culture = positive = severe disease
Sputum analysis = more than 25 PMNs and less 10 epithelial cells per 100x field indicates pneumonia
Describe Streptococcus pneumoniae
CAUSES TYPICAL PNEUMONIAE (pneumococcal pneumonia)
- normal colonizer of the URT.
- Gram-positive diplococci in chains
- Alpha-hemolytic (not complete, green tint)
- CATALASE NEGATIVE (diff. from staph)
- LOTS OF SEROTYPES: classified by capsular polysaccharides
Describe the virulence factor of Pneumococcal
- IgA protease = Cleaves IgA, prevents clearance
- Pneumolysin = pore forming toxin, colonization, invasion, inflammation, complement activation
- Teichoic acid/peptidoglcan = inflammation
- capsule = antiphagocytic
Describe the pneumonia presentation
- cough, fever, dyspnea, chest pain, crackles, sputum production
- Rust-colored sputum = rare but considered indicative
- ABRUPT spiking fever with chills
- poor oxygenation
Describe the laboratory diagnosis of S. Pneumoniae
- Gram-stain of sputum
- Culture and biochemical tests
- -> blood and sputum
- -> alpha-hemolysis on blood agar
- -> catalase negative (diff from staphylococcus)
- -> bile solubility positive
- -> optochin sensitive
- Urine collection/concentration (test for pneumococcal polysaccharide
Describe treatment and prevention of S. pneumoniae
Treatment:
- penicillin for sensitive strains
- macrolide (azithromycin
- serious case: azithromycin + cephalosporin
- Antimicrobial susceptibility testing for directed therapy
Prevention:
- vaccination
Describe staphylococcus aureus
CAUSES Typical Pneumoniae
- normal microbiota in some individuals
- gram-positive cocci in clusters
- catalase POSITIVE (diff froms trep)
- Coagulase POSITIVE (diff from other staphylococci)
Describe the virulence factors of Staphylococcus aureus
- Coagulase = clotting of blood
- Protein A = binds Fc portion of antibody
- Panton-Valentine leukocidin (PVL) = causes severe necrotizing pneumonia (pore forming cytotoxin
Describe MRSA
Methicillin resistant Staphylococcus aureus (MRSA)
- resistant to all BETA-LACTAM antibiotics (including cephalosporins)
- NOT MORE VIRULENT, just harder to treat
Treatment:
- penicillins/cephalosporins if not resistant
-MRSA –> linezolid (newer 50S inhibitor class) or vancomycin
Describe pneumonia caused by Gram-negative bacteria
- more likely to be nosocomial (HAP)
- common in aspiration pneumonia
- Klebsiella pneumoniae and pseudomonas aeruginosa are most common causes
Describe the characteristics of Gram-Negative pneumonia
- patients generally have an underlying disease
- Symptoms = cough, purulent sputum, fever, chest pain, dyspnea, crackles
- Anaerobic bacterial etiology = FOUL SMELLING SPUTUM
- Any lobe may be affected
- 1/4 have pleural effusion
- antibiotic resistance is a BIG problem
describe the labs for diagnosis and treatment of Gram-negative pneumonia
Labs: - Sputum culture and gram-staining - blood culture = 20% are positive Treatment: - Broad spectrum antibiotics - multiple drug therapy (cover most possibilities before ID)
Describe characteristics of Klebsiella pneumoniae
- Gram-negative Rod
- non-motile
- mucoid colonies (capsules)
- strains commonly produce extended-spectrum beta lactamases
- OXIDASE NEGATIVE
describe the presentation of Klebsiella pneumoniae
Presents as a classic lobar pneumonia
–> bloddy sputum from necrosis and abscess (“currant jelly sputum”)
Virulence factors = LPS (endotoxin), capsule
Describe the treatment of Klebsiella pneumoniae
Treatment:
- same as other gram-negative pneumonias (50% mortality rate even with treatment)
- increasing rate of antibiotic resistance (extended spectrum beta lactamase (ESBL) producing strains are very problematic)
Prevention:
- disinfection of environment
- use of sterile respiratory equipment
