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Staphylococci, in vitro and in vivo
Abstract:
Strains of Staphylococcus aureus were grown in broth and by the membrane technique; both drug-free media and media containing cloxacillin were used. The staphylococci grown in broth containing cloxacillin showed one thick cross wall and were larger than those grown in drug-free broth: 1.6 micron in diameter as opposed to 0.9 micron. The staphylococci grown on membranes placed on agar containing cloxacillin were 2-3 microns in diameter and contained three or more cross walls. Mice were infected intraperitoneally with staphylococci. After treatment with cloxacillin, the peritoneal fluid and spleens contained staphylococci that were 2-3 microns in diameter with three or more cross walls. A staphylococcal endocarditis was induced in rabbits that were then treated with cloxacillin. The staphylococci in the vegetation of the treated rabbits were 2-3 microns in diameter and contained multiple cross walls. Large staphylococci with multiple cross walls were observed in specimens from patients with respiratory infections treated with beta-lactam antibiotics. It appears, therefore, that the ultrastructure of staphylococci in vivo is comparable to that of staphylococci grown on a solid support medium such as a membrane, and different from that of staphylococci grown in a liquid medium.
Insights
Cloxacillin treatment causes Staphylococcus aureus to grow larger with multiple cross walls, similar to growth on solid media. This observed ultrastructure in vivo differs from liquid culture findings.
Area of Science:
- Microbiology
- Cell Biology
- Pharmacology
Background:
- Staphylococcus aureus is a common pathogen.
- Antibiotic resistance is a growing concern.
- Understanding bacterial morphology under antibiotic pressure is crucial.
Purpose of the Study:
- To investigate the effect of cloxacillin on Staphylococcus aureus ultrastructure.
- To compare bacterial morphology in liquid versus solid-state growth conditions.
- To correlate in vitro findings with in vivo observations.
Main Methods:
- Culturing Staphylococcus aureus in liquid broth and on membranes with and without cloxacillin.
- Infecting mice and rabbits with Staphylococcus aureus and treating with cloxacillin.
- Analyzing bacterial morphology using microscopy.
Main Results:
- Staphylococci grown in broth with cloxacillin were larger (1.6 micron) with one thick cross wall compared to drug-free broth (0.9 micron).
- Staphylococci grown on membranes with cloxacillin were larger (2-3 microns) with multiple cross walls.
- In vivo, cloxacillin-treated staphylococci in mice and rabbits exhibited similar morphology (2-3 microns, multiple cross walls) to membrane-grown bacteria.
Conclusions:
- The ultrastructure of Staphylococcus aureus in vivo resembles that of bacteria grown on solid media (membranes), not liquid media.
- Cloxacillin induces significant morphological changes in Staphylococcus aureus, leading to larger cells with multiple cross walls.
- These findings highlight the importance of growth conditions in determining bacterial response to antibiotics.