Caenorhabditis elegans as a host model for community-associated methicillin-resistant Staphylococcus aureus

Area of Science:

• Microbiology
• Pathogenesis Research
• Nematode Model Systems

Background:

• The nematode Caenorhabditis elegans is an emerging host model for investigating Staphylococcus aureus virulence.
• Understanding the differential pathogenicity of Staphylococcus aureus strains, particularly methicillin-resistant S. aureus (MRSA), is crucial for public health.

Purpose of the Study:

• To evaluate the toxicity and virulence of epidemic MRSA strains using the C. elegans model.
• To compare the pathogenicity of community-associated MRSA (CA-MRSA) versus hospital-associated MRSA (HA-MRSA) in a non-mammalian host.

Main Methods:

• Exposure of C. elegans nematodes to clinical isolates of MRSA, including USA300, USA400, CMRSA2, NCTC8325, CMRSA6, and M92.
• Assessment of nematocidal activity, nematode survival rates over 9 days, and inhibition of second-generation nematode growth.
• Analysis of bacterial growth curves and genetic profiles of both nematocidal and non-nematocidal strains.

Main Results:

• MRSA strains USA300, USA400, CMRSA2, and NCTC8325 demonstrated high nematocidal activity, killing >90% of nematodes and inhibiting growth.
• MRSA strain CMRSA6, colonization strain M92, and Staphylococcus epidermidis ATCC12228 showed no toxicity to C. elegans.
• Nematocidal strains exhibited similar low maximum density growth patterns but diverse genetic profiles, while non-nematocidal strains shared genomic backgrounds and virulence gene profiles.

Conclusions:

• Community-associated MRSA strains are more pathogenic than hospital-associated MRSA strains in the C. elegans model.
• The C. elegans model effectively differentiates the virulence of S. aureus strains.
• Further research is needed to elucidate specific virulence factors distinguishing pathogenic from non-pathogenic strains.