Alcohol and Pulmonary Immunity to MRSA

Lsu Health Sciences Center, New Orleans LA

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Abstract

Staphylococcus aureus is the leading cause of skin infections that presents to the emergency department. With the advent of methicillin resistant strains, outbreaks of community-acquired methicillin- resistant S. aureus (CA-MRSA) pneumonia have emerged as a very possible threat. The incidence of CA- MRSA has been increasing and presently at about 20 per 100,000 pneumonia cases. Although many factors of S. aureus virulence have been extensively studied, the mechanisms of human host defense against this pathogen have yet to be fully characterized. However alcohol abuse leads to susceptibility to multiple pulmonary bacterial infections. We have found that administration of alcohol 30 minutes lead to decreased pulmonary clearance of MRSA at 20 hours in mice. With acute alcohol, proinflammatory cytokine interleukin 22 (IL-22) was increased however, IL-22 inducible antimicrobial protein Reg3y was not increased proportionally. Acute alcohol intoxication has been shown to increase expression of Suppressor of Cytokine Signaling (SOCS) 1 and 3, which ultimately inhibit Signal Transducer and Activator of Transcription 3 (STAT3) signaling. Therefore we hypothesize that acute alcohol intoxication suppresses STAT3 signaling needed for IL-22 induction of Reg3y leading to increased pulmonary MRSA susceptibility. In support of this hypothesis, Reg3y inhibits MRSA growth in vitro and Hyper IgE Syndrome (HIES) patients are susceptible to recurrent S. aureus skin and pulmonary infections as a result of mutations in STAT3. To test our hypothesis that alcohol inhibits IL-22/STAT3 induction of Reg3y that is critical for MRSA pneumonia, we will observe bacterial burden, STAT3 activation and signaling, within cell cultures and after MRSA oropharyngeal aspiration in an acute alcohol mouse model.