Extracellular killing of inhaled pneumococci in rats
Early clearance of inhaled Staphylococcus aureus is believed to be caused by phagocytosis by alveolar macrophages. In murine models inhaled pneumococci are cleared even more rapidly than S. aureus. Conventional opsonins appear to play no role in this clearance, and recently it has been shown that murine alveolar lining material contains free fatty acids and other soluble factors that are directly bactericidal for pneumococci. To determine whether non-phagocytic factors are involved in pneumococcal clearance, we compared the site of killing of inhaled pneumococci and S. aureus in rats using histologic methods and bronchoalveolar lavage. Spontaneous lysis of pneumococci was prevented by use of autolysin-defective pneumococci or by substitution of ethanolamine for choline in the cell wall. Histologic studies showed that the percent of inhaled staphylococci associated with alveolar macrophages always exceeded the percent of staphylococci cleared, whereas there was little association of pneumococci with macrophages during clearance. Analysis of the intracellular or extracellular location of iron 59 in bronchoalveolar lavage fluid of rats that had inhaled aerosols of /sup 59/Fe-labeled bacteria suggested that staphylococci were killed predominantly in macrophages and pneumococci in the extracellular space. When /sup 59/Fe-labeled pneumococci or staphylococci were ingested and killed by macrophages in vitro, the /sup 59/Fe remained with the macrophages, suggesting that the extracellular location of /sup 59/Fe during pneumococcal killing in vivo was not caused by rapid turnover of /sup 59/Fe in macrophages. Studies of the site of killing of inhaled type 25 pneumococci labeled exclusively in the cell wall with carbon 14-ethanolamine confirmed the results obtained with /sup 59/Fe-labeled pneumococci. Thus, early killing of inhaled pneumococci, unlike staphylococci, appears to take place outside of macrophages.
- Research Organization:
- Veterans Administration, Lexington, KY
- OSTI ID:
- 5603972
- Journal Information:
- J. Lab. Clin. Med.; (United States), Vol. 110:6
- Country of Publication:
- United States
- Language:
- English
Similar Records
Effect of ozone on concentrations of lysozyme in phagocytizing alveolar macrophages
Modulation of pulmonary defense mechanisms by acute exposures to nitrogen dioxide. [Staphylococcus aureus; Proteus mirabilis; Pasteurella pneumotropica]
Related Subjects
PNEUMOCOCCUS
INHALATION
LUNG CLEARANCE
PHAGOCYTOSIS
BIOLOGICAL MODELS
CARBON 14 COMPOUNDS
CARBOXYLIC ACIDS
CELL KILLING
COMPARATIVE EVALUATIONS
IRON 59
MACROPHAGES
RATS
STAPHYLOCOCCUS
TRACER TECHNIQUES
ANIMAL CELLS
ANIMALS
BACTERIA
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CLEARANCE
CONNECTIVE TISSUE CELLS
DAYS LIVING RADIOISOTOPES
EVEN-ODD NUCLEI
EXCRETION
INTAKE
INTERMEDIATE MASS NUCLEI
IRON ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
LABELLED COMPOUNDS
MAMMALS
MICROORGANISMS
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PHAGOCYTES
RADIOISOTOPES
RODENTS
SOMATIC CELLS
VERTEBRATES
550901* - Pathology- Tracer Techniques