Staphylococcus aureus Pneumonia: Preceding Influenza Infection Paves the Way for Low-Virulent Strains.

Christina Ehrhardt,Jennifer Geraci,Mathias Pletz,Bettina Löffler,Karoline Frieda Haupt,Stefanie Deinhardt-Emmer,Marina Garcia-Moreno,Christina Forstner

doi:10.3390/toxins11120734

Christina Ehrhardt, Jennifer Geraci + Show 6 more

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https://doi.org/10.3390/toxins11120734

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Journal: Toxins	Publication Date: Dec 17, 2019
Citations: 18	License type: CC BY 4.0

Affiliation: Jena University Hospital, Medical University of Vienna

Abstract

Staphylococcus aureus is a facultative pathogenic bacterium that colonizes the nasopharyngeal area of healthy individuals, but can also induce severe infection, such as pneumonia. Pneumonia caused by mono- or superinfected S. aureus leads to high mortality rates. To establish an infection, S. aureus disposes of a wide variety of virulence factors, which can vary between clinical isolates. Our study aimed to characterize pneumonia isolates for their virulent capacity. For this, we analyzed isolates from colonization, pneumonia due to S. aureus, and pneumonia due to S. aureus/influenza virus co-infection. A total of 70 strains were analyzed for their virulence genes and the host–pathogen interaction was analyzed through functional assays in cell culture systems. Strains from pneumonia due to S. aureus mono-infection showed enhanced invasion and cytotoxicity against professional phagocytes than colonizing and co-infecting strains. This corresponded to the high presence of cytotoxic components in pneumonia strains. By contrast, strains obtained from co-infection did not exhibit these virulence characteristics and resembled strains from colonization, although they caused the highest mortality rate in patients. Taken together, our results underline the requirement of invasion and toxins to cause pneumonia due to S. aureus mono-infection, whereas in co-infection even low-virulent strains can severely aggravate pneumonia.

Highlights

Staphylococcus aureus (S. aureus) is a facultative pathogenic bacterium that colonizes the nasopharyngeal area of many healthy individuals, but can cause severeToxins 2019, 11, 734; doi:10.3390/toxins11120734 www.mdpi.com/journal/toxinsToxins 2019, 11, 734 infections, such as pneumonia and bloodstream infections aggravating to sepsis and septic shock [3].Community-acquired pneumonia (CAP) is the most frequent infection requiring hospitalization and accounts for high morbidity and mortality worldwide
We found that strains from pneumonia reveal a higher invasive capacity and higher cytotoxicity against immune cells than strains from colonization and co-infection, suggesting that bacteria require a defined level of virulence to initiate a lung infection
We demonstrate that host cell invasion is a characteristic feature of strains that h we removed all extracellular bacteria by lysostaphin-treatment and incubated the infected host cells establish pneumonia

Summary

Introduction

Staphylococcus aureus (S. aureus) is a facultative pathogenic bacterium that colonizes the nasopharyngeal area of many healthy individuals (about 30% of the population [1,2]), but can cause severe. Community-acquired pneumonia (CAP) is the most frequent infection requiring hospitalization and accounts for high morbidity and mortality worldwide. CAP is the leading cause of death [4], and in the elderly (over 80 years of age) the incidence of pneumonia is high [5]. The problem is further aggravated by the emergence and spread of methicillin-resistant S. aureus (MRSA). S. aureus is relatively rare compared to pneumococcal CAP [6] but often very severe. In contrast to CAP, in hospital-acquired pneumonia (HAP) S. aureus is the most frequent pathogen

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