Microbiology of Pneumonia

Clinical Setting



(n€jm 2002.347:2039)

S. pneumoniae

Mycoplasma. Chlamydia, viral (espec. in young & healthy)

H. influenzae, M. catarrhal (espec. in COPD'ers)

Legionella (espec. in elderly, smokers, i immunity)

Klebsiella & other GNR (especially in alcoholics & aspirators)

S. aureus (espec. postviral infection)

Influenza A & B (espec. in elderly and pulm. disease)

(no organism identified in 40-60% cases)


GNR including Pseudomonas, Klebsiella, £ coli, Enterobacter, Serratia, Acinetobacter, & S. aureus (MRSA)


AJI of the above • PCP. fungi. Nocardia, atypical mycobacteria, CMV.HSV


(nejm 2001:334:665)

Chemicol pneumonitis due to aspiration of sterile gastric contents Bacterial pneumonia due to inhalation of oropharyngeal microbes outpatients: typical oral flora (Strep. Staph, anaerobes) inpatients or chronically ill: GNR and S. aureus

Clinical manifestations

• "Typical": acute onset of fever, cough productive of purulent sputum, dyspnea.

consolidation on CXR

• "Atypical" (originally described as culture ©): insidious onset of dry cough.

extrapulmonary sx (N/V, diarrhea, headache, myalgias, sore throat), patchy interstitial pattern on CXR

• Symptoms do not reliably distinguish between "typical" (S. pneumoniae, H. influenzae) and

"atypical" (Mycoplasma, Chlamydia, Legionella) pathogens

• Influenza: fever, chills, sweats, malaise, headache, myalgias, nonproductive cough serious illness, espec. in elderly and in those w/ cardiopulmonary disease can lead to 2° bacterial pneumonia

Diagnostic studies

• Sputum Gram stain: utility debated

Is it a good sample (ie, sputum or spit)? — should be <10 squamous cells/lpf Is it a purulent sample? -» should be 25 PMNs/lpf

• Sputum culture: sample should be transported to lab w/in 1-2 h of collection

• Blood cultures (before antibiotics!): © in 10% of inPts, depending on pathogen

• CXR (PA & lateral): effusions >1 cm should be tapped

• Other laboratory evaluation: CBC w/ differential, electrolytes. BUN/Cr. glucose. LFTs

• Special microbiologic studies:

Mycoplasma: PCR of throat or sputum/BAL

Legionella: urine Ag (detects L pneumophilia L1 serotype. 70% of clinical disease) S. pneumoniae urinary Ag Rapid influenza assay (Se 70%)

MTb: induced sputum for acid-fast stain and mycobacterial cx (empiric respiratory isolation while results pending); request rapid DNA probe if stain © Induced sputum for PCP if HIV © or known decreased cell-mediated immunity Viruses: nasal washings or swabs for EIA or DFA HIV test if Pt 15-54 y

• Bronchoscopy: consider if Pt immunosuppressed. critically ill. failing to respond, or has chronic pneumonia. Also in suspected MTb if no adequate sputum and in suspected PCP if induced sputum unavailable or 0.

• CT scan: consider if failing to respond to appropriate therapy

P.O.R.T. Score, Prognosis, and Recommended Triage




Suggested Triage


age <50, no comorbidities










! Brief inpatient












Men (age in y), women (age -

10). nursing home resident (-10)

Coexist probs Neoplasm (• 30). liver disease (-20). CHF (410). CVA (• 10).

renal disease (*10) Exam aMS (• 20). RR >30 (♦ 20). SBP 90 (• 20).

Temp 35' or 40°(-15).HR 125 ( -10) Laboratory pH 7.35 (• 30). BUN 30(-20).Na 130(-20).glc 250 (-10).

Hct 30 10). P.O? < 60 or S.O> 90 (• 10). pleural effusion (• 10)

(NiJM 1997:336:243)

Clinical scenario Outpatient

Community-acquired, hospitalized Community-acquired, hospitalized, ICU Hospital-acquired with risk factors for MDR pathogens Immunocompromised Aspiration Influenza A & B

Route of therapy


Empiric treatment guidelines41

No recent abx: macrolide or doxycydine Recent abx: [macrolide • (high-dose amoxicillin or amoxicillin/clavulanate or 2nd generation ceph.)] or respiratory FQ

[3rd gen. ceph. • macrolide] or respiratory FQ

[3rd gen. ceph. • macrolide] or respiratory FQ (assuming no risk for Pseudomonas) [Antipseudomonal PCN or 3rd gen. ceph. or FQ or carbapenem] and vancomycin use FQ or add azithromycin if suspect Legionella As above - TMP-SMX - steroids to cover PCP (3rd gen. ceph. or FQ] • [clindamycin or metronidazole] M2 inhib. (amantidine. rimantidine) effective against A only Neuraminidase inhib. (oseltamivir. zanamivir) effective against A & B

Drugs 1 duration of illness only if started 48 h from onset Inpatients should initially be treated with IV antibiotics A to PO when clinically responding and able to take POs

•When posubte. organtjm-direcced therapy, guided by m vnro iuJcepoWiuci or tool patterns of drug rwntance should be utilized. For ventilaior-auociated pneumonu. 8 1S d of Rx. cxccpc for Pseudomonos and other noo-fermenung GNR (JAMA 2003:290:2588). (OD 2003.37:1405: AfUCCM 2005:171:388: MMWR 2005.54:1)

Prognosis (also see PORT score above)

• Pneumonia and influenza arc the 8th leading cause of death in the USA

• Pts usually stabilize in 2-3 d (jama 1998:2791452)

• For low-risk Pts. can discharge immediately after switching to PO abx (Che« 1998.113142)

• CXR resolves in most by 6 wks; important to document complete resolution to r/o underlying malignancy


• Inactivated influenza vaccine: persons 50 y of age. at risk for complications of influenza.

health care workers, caretakers of high-risk persons

• Pneumococcal polysaccharide vaccine: persons 65 y of age and those with high-risk

Was this article helpful?

0 0

Post a comment