EXPLODING BACTERIAMed Decision Speed Tools

Community-Acquired Pneumonia

Chest & BackUpdated 2026-03-24
Inpatient WITH Pseudomonas Risk Factors ± ICU
Consider antipseudomonal coverage if: prior Pseudomonas isolation from the respiratory tract, recent hospitalization with IV antibiotics (within 90 days), or structural lung disease (bronchiectasis, cystic fibrosis, advanced COPD).
ICU withOUT Pseudomonas Risk Factors
Non-ICU withOUT Pseudomonas Risk Factors
Outpatient or IV to PO Transition
β-LactamPick onerequired
+
FluoroquinolonePick onerequired
±
Anti-MRSAOptionalif risk
Choose ONE Antipseudomonal β-Lactam
Cefepime₄
2 g IV q8h
IV
500 mg1 g2 g
BrandsGeneric, Maxipime®
View full Cefepime page →
Ceftazidime₃
???
2 g IV q8h
IV
500 mg1 g2 g6 g
BrandsGeneric, Fortaz®, Tazicef®
View full Ceftazidime page →
Imipenem-Cilastatin
???
Your EMR may offer you a “helpful” allergy warning when ordering a carbapenem because your patient is allergic to penicillins or cephalosporins; the cross reactivity is very low and most people tolerate carbapenems with a low risk of allergic reaction.
500 mg IV q6h
IV
250 mg500 mg
BrandsGeneric, Primaxin®
View full Imipenem-Cilastatin page →
Meropenem
???
Can increase to 2 g IV q8h for CNS involvement.
Your EMR may offer you a “helpful” allergy warning when ordering a carbapenem because your patient is allergic to penicillins or cephalosporins; the cross reactivity is very low and most people tolerate carbapenems with a low risk of allergic reaction.
1 g IV q8h
IV
500 mg1 g
BrandsGeneric, Merrem®
View full Meropenem page →
Piperacillin-Tazobactam
???
Extended infusion (4 hr) preferred if available.
4.5 g IV q6h
IV
2.25 g3.375 g4.5 g
BrandsGeneric, Zosyn®
View full Piperacillin-Tazobactam page →
+
AND Choose ONE Fluoroquinolone
Ciprofloxacin
!!
400 mg IV q8h / 750 mg PO q12h
Tablets
250 mg500 mg750 mg
Liquid
250 mg/5 mL500 mg/5 mL
IV
200 mg/100 mL400 mg/200 mL
BrandsGeneric, Cipro®
View full Ciprofloxacin page →
Levofloxacin
???
750 mg IV/PO q24h
Liquid
25 mg/mL oral solution
Tablets
250 mg500 mg750 mg
IV
5 mg/mL (premix)25 mg/mL (vial)
BrandsGeneric, Levaquin®
View full Levofloxacin page →
±
Consider ONE Anti-MRSAONLY if risk factors
Add anti-MRSA only for a real risk factor — it is not routine in CAP.
Risks: prior MRSA (infection, colonization, or positive nasal PCR); hospitalization or IV antibiotics ≤90 days; severe, necrotizing, or cavitary pneumonia; empyema; recent influenza; ESRD/dialysis; injection drug use.
Negative nasal PCR (NPV ~95–99%) → reasonable to withhold or stop.
VancomycinMRSA
???
Monitor: target AUC/MIC 400–600; check a level before the 4th dose.
15–20 mg/kg IV q8–12h
IV
500 mg750 mg1 g1.25 g5 g
Capsules — PO, C. diff only
125 mg250 mg
BrandsGeneric, Vancocin®
View full Vancomycin page →
LinezolidMRSA · VRE
???
600 mg IV/PO q12h
Tablets
600 mg
Liquid
100 mg/5 mL
IV
600 mg/300 mL
BrandsGeneric, Zyvox®
View full Linezolid page →
AztreonamPick onerequired
+
FluoroquinolonePick onerequired
+
AminoglycosidePick onerequired
±
Anti-MRSAOptionalif risk
Select
Aztreonam
???
Do NOT give aztreonam to those with a Ceftazidime₃ allergy (shared side chain → cross-reactivity).
2 g IV q8h
IV / IM
1 g vial2 g vial
Inhaled (Cayston®)
75 mg
BrandsGeneric, Azactam®, Cayston® (inhaled)
View full Aztreonam page →
+
AND Select
Levofloxacin
???
750 mg IV/PO q24h
Liquid
25 mg/mL oral solution
Tablets
250 mg500 mg750 mg
IV
5 mg/mL (premix)25 mg/mL (vial)
BrandsGeneric, Levaquin®
View full Levofloxacin page →
+
AND Choose ONE Aminoglycoside
Amikacin
???
Requires drug level monitoring.
15–20 mg/kg IV q24h
IV / IM
250 mg/mL50 mg/mL
BrandsGeneric, Amikin®
View full Amikacin page →
Gentamicin
???
Requires drug level monitoring.
5–7 mg/kg IV q24h
IV / IM
10 mg/mL40 mg/mL
BrandsGeneric, Garamycin®
View full Gentamicin page →
Tobramycin
???
Requires drug level monitoring.
5–7 mg/kg IV q24h
IV / IM
10 mg/mL40 mg/mL
Inhaled (Tobi®)
300 mg/5 mL
BrandsGeneric, Tobi® (inhaled)
View full Tobramycin page →
±
Consider ONE Anti-MRSAONLY if risk factors
Add anti-MRSA only for a real risk factor — it is not routine in CAP.
Risks: prior MRSA (infection, colonization, or positive nasal PCR); hospitalization or IV antibiotics ≤90 days; severe, necrotizing, or cavitary pneumonia; empyema; recent influenza; ESRD/dialysis; injection drug use.
Negative nasal PCR (NPV ~95–99%) → reasonable to withhold or stop.
VancomycinMRSA
???
Monitor: target AUC/MIC 400–600; check a level before the 4th dose.
15–20 mg/kg IV q8–12h
IV
500 mg750 mg1 g1.25 g5 g
Capsules — PO, C. diff only
125 mg250 mg
BrandsGeneric, Vancocin®
View full Vancomycin page →
LinezolidMRSA · VRE
???
600 mg IV/PO q12h
Tablets
600 mg
Liquid
100 mg/5 mL
IV
600 mg/300 mL
BrandsGeneric, Zyvox®
View full Linezolid page →

Pneumonia Severity Index (PSI)

Helps determine risk of mortality from Community-Acquired Pneumonia (CAP) and guides home vs. admit; PSI is favored over CURB-65 by ATS/IDSA but is cumbersome to use, resulting in many preferring CURB-65.

← Back to ABX Selector
Class II · Low risk
0.6% mortality
Consider outpatient treatment
0pts
Patient age
yr
0
Demographics
Nursing home resident
Comorbidities
Neoplastic disease
Liver disease history
CHF history
Cerebrovascular disease history
Renal disease history
Exam findings
Altered mental status
Respiratory rate ≥30 breaths/min
Systolic blood pressure <90 mmHg
Temperature <35°C or >39.9°C
Pulse ≥125 beats/min
Labs & imaging
pH <7.35
BUN ≥30 mg/dL
Sodium <130 mmol/L
Glucose ≥250 mg/dL
Hematocrit <30%
PaO₂ <60 mmHg
Pleural effusion on x-ray

CURB-65

Estimates the mortality of community-acquired pneumonia (CAP) and suggests inpatient vs. outpatient treatment. PSI is favored over CURB-65 by ATS/IDSA, but PSI is cumbersome to use — so many prefer CURB-65.

← Back to ABX Selector
Low risk
Score 0–1 · ~1.5% 30-day mortality
Consider outpatient treatment
0pts
Confusion (new disorientation to person, place, or time)
Urea (BUN) >19 mg/dL (>7 mmol/L)
Respiratory rate ≥30 breaths/min
Low blood pressure (SBP <90 mmHg or DBP ≤60 mmHg)
Age ≥65 years

DRIP

Attempts to predict the risk of drug-resistant organisms (DRPs) in community-acquired pneumonia (CAP).

← Back to ABX Selector
Low DRP risk
Score 0–3
Low risk of drug-resistant pathogens — consider standard CAP therapy, WITHOUT broad-spectrum antibiotics
0pts
Major risk factors — 2 points each
Antibiotic use within previous 60 days
Current resident of SNF, LTACH, or inpatient rehab
Tube feeding
Prior infection with a DRP within previous 1 year
Minor risk factors — 1 point each
Hospitalization within previous 60 days
Chronic pulmonary disease
Poor functional status
PPI / H2 blocker within last 14 days
Currently receiving active wound care
MRSA colonization within previous 1 year

ICU Guidelines

Helps determine the need for the ICU in patients with community-acquired pneumonia (CAP), as outlined by the American Thoracic Society (ATS) / IDSA. Meeting ≥3 minor criteria suggests ICU-level care.

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Below ICU threshold
0–2 minor criteria
ICU not indicated by this rule; floor admission reasonable
0pts
Vitals & mental status
Confusion / disorientation
Hypothermia (core temp <36°C / <96.8°F)
Hypotension requiring aggressive fluid resuscitation
Respiratory rate ≥30 breaths/min
Oxygenation & imaging
PaO₂/FiO₂ ratio <250
Multilobar infiltrates
Labs
Leukopenia (WBC <4,000/mm³, not from chemotherapy)
Thrombocytopenia (platelets <100,000/mm³)
Uremia (BUN >20 mg/dL)

TLDR

Acute infection of the lung parenchyma acquired outside of the hospital; fever, productive cough, dyspnea, lung infiltrates. Typical pathogens include Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Atypical pathogens include Mycoplasma pneumoniae, Chlamydia pneumoniae, Legionella pneumophila, and Coxiella burnetii (Q fever). Their treatments are incorporated into this algorithm.