Pneumonia Flashcards
3 Routes of Infection
- Micro- aspiration of upper airway secretions or gastric contents
- Aerosolization (inhaled from infected person or environment)
- Hematogenous spread - rare; seen in Staph aureus R sided endocarditis (high risk in IV drug users)
What normal colonizes the airway?
viridans strep, Neisseria, Candida, anaerobes
Aspiration Pneumonitis (+3 phases)
- Acute lung injury after inhalation of regurgitated gastric contents (usually w/ intoxication or dysphagia post-stroke)
- Low pH –> chemical burn –> inflammation NOT infection
- Phases
- 1- direct effects of acid in 1-2 hrs
- 2- neutrophils in alveoli in 4-6 hrs
- Mimics infectious pneumonia (chest X ray infiltrate, fever, leukocytosis)
- 3- inflamm response resolves in about 48 hrs
- Usually sterile due to low pH so no need for abx unless gram neg rods from stomach flora
5 Most Common Causes of CAP
- Strep pneumo
- Haemophilus influenza / M. catarrhalis
- Viruses (adeno, rhino, flu, SARS/MERS, RSV, metapneumovirus)
ATYPICALS - mycoplasma pneumoniae & Chlamydophila pneumoniae
-Legionella
3 Rare Causes of CAP (when does each normally occur?)
- Staph aureus - usually secondary pneumonia (viral infection like flu 1st)
- Klebsiella - enteric gram neg (esp in alcoholics/malnourished/DM - aspirate from gut)
- Pseudomonas - CF/bronchiectasis, recent abx, recent ICU stay
CAP Therapy
- Empiric Tx - want to cover strep pneumo, gram neg H flu and atypicals
- Doxycycline (tetracyclin - bind ribosomes w/ cation to inhibit protein synthesis; bacteriostatic)
- Azithromycin (macrolide - bind ribosomes to inhibit protein synthesis; bacteriostatic)
- Levofloxacin (Fluroquinolone - inhibit DNA synthesis - careful of C diff)
***Must ask them if they have been on recent abx - exclude those in case of resistance
Signs/Symptoms/Tests for CAP
- Prod cough, fever, pleuritic chest pain (when inspire you stretch pleura; worse if bradykinin or PGE2), SOB, chills, may have rusty sputum
- Inc WBC, left shift of neutrophils
- Gram stain (neg if atypical or viral); then do specific stain or PCR for virus
- Sputum cx, blood or pleural cx more accurate b/c normally sterile
- Legionella = urinary antigen test
3 Types of Healthcare-Associated Pneumonia (common bugs and tx for ea)
- 1- Early Onset VAP (<48 hrs) - looks like CAP
- Strep pneumo, H flu, Staph aureus
- Tx = amp/sulbactam - 2- Late Onset VAP (2-5 dys)
- MRSA, Pseudo, gram neg rods
- Tx = vancomycin, cefepime, tobramycin - 3- HAP, non-VAP (not on vent)
- aerobic and anaerobic gram neg rods
- Tx = piperacillin/tazobactam
Typical Infections in HIV/AIDS Based on CD4+ Count
> 200 - Strep pneumo, M tuberculosis
<200 - Strep pneumo, M tuberculosis, Pneumocyctis (PJP)
<50 - Strep pneumo, M tuberculosis, Pneumocyctis (PJP), CMV (enlarged cells)
Typical Infections Post-Transplant By Time Elapsed
<1 mo - MRSA, Pseudomonas (and other gram neg rods), Legionella, Aspergillus
1-6 mo - CMV, Aspergillus, Legionella
> 6 mo - Nocardia (brain involvement too), mycobacteria, Cryptococcus, Coccidodes immitis (SW US)
In General, What Types of Immune Def Correspond w/ What??
Opsonization/Complement Def (SLE or asplenia) -
- Encapsulated organisms (Strep pneumo, H flu, Neisseria mening)
IgG Def - encapsulated (Strep pneumo and H flu Neisseria mening)
IgA Def - Giardia
T Cell Def - Opportunistic (Cryptococcus, Candida, Pneumocystis jaroveci, Toxoplasma parasites, Tb, MAC) AND Viruses (HSV, VZV, CMV, KSHV, HPV, JC, BK)
Granulocytes/ Neutrophils (neutropenia/CGD) - Catalase-pos organisms (Aspergillus, Pseudomonas, Staph aureus)
Wiskott-Aldrich (dec T cell # and function; low IgM/IgG) - so viruses, PJP and encapsulated
Lobar Pneumonia (+4 phases)
- most or all of a single lobe involved
- Most common in strep pneumo (95%) or Klebsiella (5%)
- Phases
- 1- Congestion (<24 hr) congested vessels and edema w/ pale eosinophilic fluid (RBCs and neutrophils); distended
- 2- Red Hepatization - exudate, hemorrhage and neutrophils fill alveolar air spaces –> SOLID/firm consistency (like liver)
- 3- Gray Hepatization (2-3 dys) red cells degraded and leukocytes in alveoli (red –> gray); firm fibrinopurulent exudate
- 4- Resolution - patchy but systematic degradation of fibrinopurulent exudate; may have macrophages taking up debris and/or fibroblasts (may go back to normal or have thickening/permanent adhesions)
Lobular Pneumonia
- (bronchopneumonia) patchy pattern of consolidation; 1+ lobes involved (multi-focal)
- Most common pattern of bacterial pneumonia
- Proteinaceous exudate in alveolar spaces
- Patchy yellow, tan infiltrate grossly
- Numerous neutrophils on histo
Interstitial Pneumonia
- inflammation confined to alveolar wall NOT airspaces
- Most common in viral pneumonia and atypical bacterial pneumonia (mycoplasma and chlamydophilia)
- Usually more mild symptoms (“atypical” or “walking” pneumonia)
- If severe - may have desquamation of alveolar epithelial cells –> fluid or blood accumulation in alveolar space –> consolidation and hyaline membranes
Mycobacteria Pathology
Tb or MAC (avium and intracellulare)
- acid-fast stain (Ziehl-Neelsen)
- necrotizing granulomas and giant cells
