Pathogenic Effect of Prevotella intermedia on a Mouse Pneumonia Model Due to Methicillin-Resistant Staphylococcus aureus With Up-Regulated α-Hemolysin Expression.

Yu Yamashita,Kentaro Nagaoka,Norihito Kaku,Masaru Suzuki,Tatsuya Fukumoto,Kasumi Hayasaka,Hiroki Kimura,Katsunori Yanagihara,Yoshitomo Morinaga,Satoshi Konno

doi:10.3389/fmicb.2020.587235

Abstract

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a common causative agent of pneumonia; however, the detailed mechanism underlying severe MRSA pneumonia, including association with oral hygiene or periodontitis, remains poorly characterized. In this study, we examined the pathogenic effect of Prevotella intermedia, a major periodontopathic pathogen, on MRSA pneumonia.Methods: The pathogenic effect of the supernatant of P. intermedia (Pi Sup) was investigated in a murine MRSA pneumonia model, using several clinical strains; whereas the bactericidal activity of polymorphonuclear leukocytes (PMNs) was investigated in vitro. The effect of Pi Sup on messenger RNA (mRNA) expression of the toxin/quorum sensing system (rnaIII) was investigated by quantitative reverse transcription PCR both in vitro and in vivo.Results: Mice infected by hospital-acquired MRSA (HA-MRSA) with Pi Sup exhibited a significantly lower survival rate, higher bacterial loads in the lungs, and higher α-hemolysin (hla) expression in the lungs, than those without Pi Sup. A similar effect of Pi Sup was not observed with MRSA strains producing Panton-Valentine leucocidin (PVL) or toxic shock syndrome toxin (TSST). In vitro, Pi Sup suppressed bactericidal activity of PMNs against the HA-MRSA strain. HA-MRSA was the clinical strain with the highest ability to proliferate in the lungs and was accompanied by time-dependent up-regulation of rnaIII and hla.Conclusions: Our results provide novel evidence that the product of P. intermedia exerts a pathogenic effect on MRSA pneumonia, in particular with a strain exhibiting strong proliferation in the lower airway tract. Moreover, our results indicate that P. intermedia affects MRSA toxin expression via quorum sensing in a strain-dependent fashion, which might be important for understanding the pathogenesis of severe MRSA pneumonia.

Highlights

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen in hospitals and intensive care units (Chastre et al, 2014)
Given the emergence of community-acquired MRSA (CA-MRSA) pneumonia (Mediavilla et al, 2012), we examined the effect of P. intermedia on expression of Panton-Valentine leucocidin (PVL) and toxic shock syndrome toxin (TSST), the two main toxins produced by CA-MRSA strains
In vivo experiments using the HUYM strain revealed that MRSA-infected mice exhibited significantly lower survival rates, higher MRSA bacterial loads in the lungs, and inflammatory cytokines in BAL fluid (BALF) when treated with PINU499 was obtained from and its supernatant (Pi Sup) than when not treated

Summary

Introduction

Methicillin-resistant Staphylococcus aureus (MRSA) is an important pathogen in hospitals and intensive care units (Chastre et al, 2014). A high (36–59%) in-hospital mortality rate has been reported among severe cases of MRSA-NP including ventilator-associated pneumonia (Hanberger et al, 2011; Bouza et al, 2012). Risk factors for developing lethal MRSA-NP are not fully clarified, several have been reported so far, such as prior use of antibiotics, history of chronic obstructive pulmonary disease, or high severity score on admission to the intensive care unit (Graffunder and Venezia, 2002; Dryden et al, 2010; Fukuta et al, 2012). Methicillin-resistant Staphylococcus aureus (MRSA) is a common causative agent of pneumonia; the detailed mechanism underlying severe MRSA pneumonia, including association with oral hygiene or periodontitis, remains poorly characterized. We examined the pathogenic effect of Prevotella intermedia, a major periodontopathic pathogen, on MRSA pneumonia

Methods

Results

Discussion

Conclusion