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Pathogenicity and virulence of coagulase negative staphylococci in relation to adherence, hydrophobicity, and toxin
C Molnàr1, Z Hevessy, F Rozgonyi
1Department of Clinical Chemistry, University of Debrecen, Hungary.
Aims:
To study the pathogenicity and virulence characteristics of Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus sapro-phyticus.
Methods:
BALB/c mice were challenged intraperitoneally with graded doses of three strains belonging to each species. LD50s were measured for each strain. Haemolysin (alpha- and delta-) and enzyme (DNAase, lipase, and esterase) production in vitro were measured qualitatively and quantitatively. Adhesion to plastic was measured and related to cell surface hydrophobicity among the strains.
Results:
S saprophyticus proved the most virulent (LD50 = 2.7-2.9 x 10(7) cfu/g body weight) while S epidermidis was the least virulent (LD50 = 6-8 x 10(7) cfu/g body weight). An enlarged spleen was the most common macroscopic pathological feature. Kidney, liver, and more rarely peritoneal abscesses were also seen in the infected animals. No direct correlation was found between adherence in vitro, cell surface hydrophobicity, or toxin/enzyme biosynthesis and virulence in mice.
Conclusion:
The results show that coagulase negative staphylococci are pathogenic in BALB/c mice. It is clear that these bacteria can cause invasive disease. However, the in vitro characteristics of coagulase negative staphylococci are not related to the pathogenicity of the organisms in mice.
Insights
Coagulase-negative staphylococci, including Staphylococcus saprophyticus and Staphylococcus epidermidis, demonstrate pathogenicity in mice. In vitro characteristics do not predict the virulence of these staphylococci in vivo.
Area of Science:
- Microbiology
- Infectious Diseases
- Bacterial Pathogenesis
Background:
- Coagulase-negative staphylococci (CoNS) are common commensals but can cause opportunistic infections.
- Understanding the virulence factors of CoNS species like Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus saprophyticus is crucial for clinical management.
Purpose of the Study:
- To investigate the pathogenicity and virulence characteristics of Staphylococcus epidermidis, Staphylococcus haemolyticus, and Staphylococcus saprophyticus in a murine model.
- To correlate in vitro characteristics with in vivo pathogenicity.
Main Methods:
- BALB/c mice were intraperitoneally challenged with varying doses of three CoNS species.
- Lethal dose 50% (LD50) values were determined for each strain.
- In vitro assays measured haemolysin and enzyme production, adhesion to plastic, and cell surface hydrophobicity.
Main Results:
- Staphylococcus saprophyticus exhibited the highest virulence (LD50 = 2.7-2.9 x 10^7 cfu/g), while Staphylococcus epidermidis was least virulent (LD50 = 6-8 x 10^7 cfu/g).
- Common pathological findings included enlarged spleen, kidney and liver lesions, and peritoneal abscesses.
- No significant correlation was observed between in vitro adhesion, hydrophobicity, or toxin/enzyme production and in vivo virulence.
Conclusions:
- Coagulase-negative staphylococci are pathogenic in BALB/c mice and can cause invasive disease.
- In vitro characteristics of CoNS do not reliably predict their pathogenicity in a murine model.
- Further research is needed to identify key virulence factors responsible for CoNS-mediated infections.