Noninvasive in vivo imaging to evaluate immune responses and antimicrobial therapy against Staphylococcus aureus and USA300 MRSA skin infections

J Invest Dermatol. 2011 Apr;131(4):907-15. doi: 10.1038/jid.2010.417. Epub 2010 Dec 30.

Abstract

Staphylococcus aureus skin infections represent a significant public health threat because of the emergence of antibiotic-resistant strains such as methicillin-resistant S. aureus (MRSA). As greater understanding of protective immune responses and more effective antimicrobial therapies are needed, a S. aureus skin wound infection model was developed in which full-thickness scalpel cuts on the backs of mice were infected with a bioluminescent S. aureus (methicillin sensitive) or USA300 community-acquired MRSA strain and in vivo imaging was used to noninvasively monitor the bacterial burden. In addition, the infection-induced inflammatory response was quantified using in vivo fluorescence imaging of LysEGFP mice. Using this model, we found that both IL-1α and IL-1β contributed to host defense during a wound infection, whereas IL-1β was more critical during an intradermal S. aureus infection. Furthermore, treatment of a USA300 MRSA skin infection with retapamulin ointment resulted in up to 85-fold reduction in bacterial burden and a 53% decrease in infection-induced inflammation. In contrast, mupirocin ointment had minimal clinical activity against this USA300 strain, resulting in only a 2-fold reduction in bacterial burden. Taken together, this S. aureus wound infection model provides a valuable preclinical screening method to investigate cutaneous immune responses and the efficacy of topical antimicrobial therapies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Administration, Topical
  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • Bridged Bicyclo Compounds, Heterocyclic / pharmacology
  • Community-Acquired Infections / drug therapy
  • Community-Acquired Infections / immunology
  • Community-Acquired Infections / pathology
  • Dermatitis / drug therapy
  • Dermatitis / immunology
  • Dermatitis / pathology
  • Dermoscopy / methods*
  • Disease Models, Animal
  • Diterpenes
  • Drug Monitoring / methods
  • Green Fluorescent Proteins / genetics
  • Interleukin-1alpha / immunology
  • Interleukin-1beta / immunology
  • Male
  • Methicillin-Resistant Staphylococcus aureus / immunology*
  • Mice
  • Mice, Inbred C57BL
  • Mice, Transgenic
  • Microscopy, Fluorescence / methods*
  • Mupirocin / pharmacology*
  • Staphylococcal Skin Infections* / drug therapy
  • Staphylococcal Skin Infections* / immunology
  • Staphylococcal Skin Infections* / pathology

Substances

  • Anti-Bacterial Agents
  • Bridged Bicyclo Compounds, Heterocyclic
  • Diterpenes
  • Interleukin-1alpha
  • Interleukin-1beta
  • enhanced green fluorescent protein
  • Green Fluorescent Proteins
  • retapamulin
  • Mupirocin