Related Experiment Video

Updated: Jun 19, 2026

Pseudomonas aeruginosa Induced Lung Injury Model
07:24

Pseudomonas aeruginosa Induced Lung Injury Model

Published on: October 29, 2014

PNEUMONIC LESIONS CAUSED BY BACILLUS MEGATHERIUM

M Wollstein1, S J Meltzer

  • 1Departments of Pathology and of Physiology and Pharmacology of The Rockefeller Institute for Medical Research, New York.

The Journal of Experimental Medicine
|October 30, 2009
PubMed

Insights

Saprophytic bacteria, like Bacillus megatherium, can cause pulmonary lesions resembling lobar pneumonia in experiments. These lesions show rapid development and resolution, differing quantitatively from typical bacterial pneumonia.

Area of Science:

  • Microbiology
  • Pathology
  • Pulmonary Medicine

Background:

  • Pneumonia is often associated with virulent bacterial pathogens.
  • The role of saprophytic bacteria in inducing pulmonary inflammation is less understood.

Purpose of the Study:

  • To investigate the capacity of the saprophytic bacterium Bacillus megatherium to induce pulmonary lesions.
  • To characterize the pathological features and temporal progression of experimentally induced lung lesions.

Main Methods:

  • Intranasal inoculation of Bacillus megatherium in experimental models.
  • Gross and microscopic examination of pulmonary tissues.
  • Assessment of lesion development, extent, and resolution over time.

Main Results:

  • Bacillus megatherium induced distinct pulmonary lesions grossly resembling lobar pneumonia.
  • Lesions featured intense, non-fibrinous, leucocytic exudation without significant bacterial presence or invasion.
  • Inflammation peaked within 24 hours, with resolution beginning by the third day, and no phagocytosis was observed.

Conclusions:

  • Saprophytic bacteria can produce pneumonic lesions similar in appearance to mild lobar pneumonia.
  • The induced lesions differ quantitatively, not qualitatively, from those caused by avirulent pneumococci.
  • Other saprophytes may similarly cause pneumonia-like lesions.

More Related Videos

Long Term Chronic Pseudomonas aeruginosa Airway Infection in Mice15:43

Long Term Chronic Pseudomonas aeruginosa Airway Infection in Mice

Published on: March 17, 2014

Visualization of Streptococcus pneumoniae within Cardiac Microlesions and Subsequent Cardiac Remodeling08:25

Visualization of Streptococcus pneumoniae within Cardiac Microlesions and Subsequent Cardiac Remodeling

Published on: April 7, 2015

Related Concept Videos

Pulmonary Tuberculosis II01:28

Pulmonary Tuberculosis II

Tuberculosis, or TB, is a bacterial infectious disease caused by Mycobacterium tuberculosis. While its primary impact is on the lungs, leading to pulmonary tuberculosis, it can also affect various other organs, a condition referred to as extrapulmonary tuberculosis.
Here is a detailed explanation of its pathophysiology:
Transmission: The process begins when a person inhales droplet nuclei containing M. tuberculosis. These are typically released into the air when an individual with pulmonary or...
Atypical Pneumonia01:14

Atypical Pneumonia

Atypical pneumonia, often caused by Mycoplasma pneumoniae, is a form of pulmonary infection that differs from the classical presentation of bacterial pneumonia in both its cause and clinical symptoms. Mycoplasma pneumoniae is a pleomorphic bacterium notable for its lack of a rigid cell wall. This structural characteristic imparts resistance to beta-lactam antibiotics and significantly influences the bacterium’s behavior within the human host.Other pathogens responsible for the disease include...
Tuberculosis01:23

Tuberculosis

Tuberculosis (TB) remains a significant global health concern, primarily targeting the lungs and spreading through airborne transmission. Infection begins when aerosolized droplet nuclei, expelled by an individual with active TB, are inhaled by another person. These microscopic particles carry Mycobacterium tuberculosis, the causative agent of TB. Upon reaching the alveoli, the bacilli are engulfed by alveolar macrophages. However, due to their specialized lipid-rich cell wall, these pathogens...
Inhalation Anthrax01:25

Inhalation Anthrax

Anthrax is a zoonotic disease caused by Bacillus anthracis, a Gram-positive, spore-forming bacterium. It primarily affects herbivorous animals but can be transmitted to humans through skin contact, ingestion, or inhalation of spores.Cutaneous anthrax, the most common form, typically results from direct contact with bacterial spores through skin abrasions and is generally less severe. Gastrointestinal anthrax results from eating undercooked or contaminated meat. It affects the mouth, throat, or...
Pneumonia I: Introduction01:29

Pneumonia I: Introduction

Pneumonia is an infection of the lower respiratory tract that leads to inflammation of the lung parenchyma, often resulting in the accumulation of inflammatory exudate in the alveoli and airways. Unlike the watery, low-protein fluid exudate in pulmonary edema, the exudate in this case is a thick fluid rich in immune cells, proteins, and debris produced during infection and inflammation.This impairs gas exchange and can lead to consolidation of lung tissue. The infection may be caused by a...
Pneumonia I: Introduction01:30

Pneumonia I: Introduction

Pneumonia is an acute respiratory infection that targets the lungs, specifically the alveoli. These tiny air sacs, essential for oxygen exchange, become engorged with pus and fluid, severely hindering breathing, decreasing oxygen absorption, and causing significant pain and discomfort during respiration.
Risk Factors
Various factors influence the likelihood of developing pneumonia. Age plays a crucial role, with infants, children under two, and individuals over 65 at increased risk due to their...