Respiratory Infections 6

Question 1

Risk factors of typical pneumonia

Answer 1

• Underlying lung disease or compromised muco-ciliary function -> risk of bronchopneumonia esp. smokers, COPD/CF, alcoholics, ventilation
• Preceding viral infection -> risk of secondary superinfection
• Suppressed immune system -> risk of bacteremia and meningitis with encapsulated bacteria esp. asplenia

Question 2

Risk of sepsis with ____________ is ~500x higher in children with sickle cell compared to healthy children

Answer 2

Risk of sepsis with S. pneumoniae is ~500x higher in children with sickle cell compared to healthy children

Question 3

Gram positive causes of typical pneumonia

Answer 3

Streptococcus pneumoniae (most common for community acquired pneumonia)
Staphylococcus aureus
Bacillus anthracis

Question 4

Gram negative causes of typical pneumonia

Answer 4

More hospital acquired
Klebsiella pneumoniae
Pseudomonas aeruginosa
Enterobacteriaceae (E. coli, Serratia, Enterobacter) Non-typeable Haemophilus influenzae NTHi Moraxella catarrhalis

Question 5

Klebsiella pneumoniae Biology

Answer 5

• Family: Enterobacteriaeceae
• Gram -ve bacillus
•Prominent capsule (mucoid appearance)
• Non-motile, facultative anaerobe 
• Lactose Fermenter*
Grows on macConkey agar

Question 6

Klebsiella Epidemiology

Answer 6

• Part of microbial flora (oral cavity and intestines) ~5%. Asymptomatic carriage if bacteria remains in colon
• Community-Acquired, Aspiration - Chronic alcohol abuse
• Hospital-Acquired, Ventilator-Associated – Intubated COVID patients
• Multiple Drug Resistance is MAJOR HEALTH THREAT!!

Question 7

Klebsiella Pathogenesis

Answer 7

• Pili (fimbriae)
• Biofilm
• LPS (Endotoxic effect of LipidA)
- Triggers robust inflammatory response via TLR4 signing (IL-8, TNFα leads to neutrophil recruitment)
• Capsular Polysaccharide – K Antigen
- Anti-phagocytic, immune evasion contributes to progression from pneumonia to sepsis
• Intrinsic antibiotic resistance via MDR Efflux Pump
• MDR plasmids - Highly mobile passed by Horizontal Gene Transfer
• Extended Spectrum β-Lactamase ESBL - Klebsiella
• Carbapenemase CR-Klebsiella or CR-Enterobacteriaceae

Question 8

Aspiration pneumonia

Answer 8

Microbes originate from gastrointestinal tract and aspirated in patient with loss of gag reflex ex. vomiting CAP or intubation HAP

> 1 area of lung parenchyma replaced by cavities filled with debris.
▪ Putrid odor to breath & sputum

Large % of cases are polymicrobial (>1 species) and can progress to Lung Abscess formation
• Facultative anaerobes (Klebsiella, MRSA) on exterior of abscess consume environmental oxygen and create an anoxic core, allowing growth of anaerobes (Gram Negative Anaerobic Rods GNAR, ex. Bacteroides)
• Extensive necrosis “Necrotizing Pneumonia”

Question 9

Complications of aspiration pneumonia

Answer 9

bacteremia, septicemia, meningitis

Question 10

Clinical Presentation of

Typical Pneumonia/ Lobar Bronchopneumonia

Answer 10

Rapid onset hours to days

Productive cough, sputum is thick, viscous due to high neutrophil influx
• Dyspnea
• Hemoptysis
• S. pneumoniae = “rust-colored sputum”
• Klebsiella = “currant jelly sputum”
• High fever
Signs of Sepsis 
• Tachycardia
• Hypotension 
• Edema

Question 11

Typical Bacterial Pneumonia

Answer 11

• Strep pneumoniae, MRSA
• Klebsiella pneumoniae, Pseudomonas aeruginosa

Bronchitis pneumonia to lobar pneumonia to necrotizing abscess