Learning Radiology xray montage
 
 
 
 
 
 

Gram Positive Pneumonias


Pneumococcal pneumonia

  • Most common gram positive pneumonia

  • 90% community acquired

  • Organism: strep pneumoniae

  • Usually found in compromised hosts, elderly, debilitated

  • Most often types 8, 4, 5 and 12

  • Type 3 is especially fatal to elderly

  • Sicklers are particularly prone to pneumococcal pneumonia

  • Produces inflammatory edema in the alveoli which spreads via pores of Kohn to more lateral alveoli

X-ray

  • Extensive infiltrate usually abutting pleural surface

  • Prominent air bronchograms (DDX: Staph has no air bronchogram)

  • Organism is aspirated into the lungs from the upper airways so it shows a predilection for lower lobes

  • Does not respect segmental boundaries

  • Resolution begins promptly with antibiotics – frequently within 24 hours

  • DDX for alveolar infiltrates with clearing in 24 hours includes

    • Hemorrhage into lungs,

    • Pulmonary edema

    • Pneumococcal pneumonia

    • Aspiration

Staph aureus pneumonia

  • Most common bronchopneumonia

  • Overwhelming majority hospital-acquired

  • Most common cause of death during influenza epidemics

  • Rarely develops in healthy adults

  • Hemolyzes blood agar

    • Coagulase positive

  • Its ability to produce pathology in humans is due to its production of coagulase

  • Produces its pathologic reaction in the conducting airways

X-ray

  • Rapid spread through the lungs

  • Empyema, especially in children

  • No air bronchogram

  • Pneumothorax

    • Pyopneumothorax

  • Abscess formation

  • Bronchopleural fistula

  • In children

  • Rapidly developing lobar/multilobar consolidation

  • Pleural effusion (90%)

  • Pneumatocoele

·       In adults
 ·       Patchy bronchopneumonia of segmental distribution, frequency bilateral
·       May be associated with atelectasis since airways are filled (not so with pneumococcal)
·       Pleural effusion (50%)  

Streptococcus pyrogenes pneumonia  

  • Most common in winter

    • Only 5% of bacterial pneumonias

  • Group A Beta hemolytic strep

  • Predisposed: Newborns and following measles

X-ray

  • Looks like staph pneumonia but with less of a tendency to produce pneumatocoeles

  • Almost always in the lower lobes

  • Patchy bronchopneumonia

  • Empyemas do form

  • Complications:

    • Bronchiectasis

    • Lung abscess

    • Glomerulonephritis

  • Associated with delayed onset of diaphragmatic hernias in newborns