Learning Radiology xray montage

Gram Negative Pneumonia

Pseudomonas aeruginosa

  • Gram negative rod

  • Frequently hospital acquired

  • Affects patients with COPD, CHF alcoholism, kidney disease, those with trachs

  • Frequently related to use of inhalators or nebulizers

  • Many patients are on multiple antibiotics and/or steroids


  • Resembles staph pneumonia

  • Predilection for the lower lobes

  • Usually affects both lungs

  • Has multiple small lucencies within it

  • Lung abscess greater than 2 cm may also occur

  • Widespread nodular shadows is another manifestation

Klebsiella, Enterobacter, Serratia

  • Encapsulated,  gram negative rods

  • Most are hospital acquired

  • Most are chronic alcoholics

  • Aspirated into lungs so most are unilateral and right sided


  • Produces excessive amounts of inflammatory exudate which cause the affected lung to gain volume and the fissures to bulge

  • Abscess and cavity formation are common

  • Pleural effusion and empyema are common

  • May result in gangrene of the lung where massive pieces of lung tissue fall into an abscess cavity

  • Serratia marcescens may cause bronchopneumonia

Anaerobic organisms

  • Frequently from aspiration of gastric contents

  • Organisms include Bacteroides melaninogenicus, B. fragilis


  • Almost always lower lobes

  • Frequently right sided

  • Homogeneous consolidation

  • About 70% will have pleural involvement–effusion, empyema–which may progress very rapidly

  • Half develop abscesses