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Published on: September 5, 2013
Methicillin-Resistant Staphylococcus aureus ST80 Induce Lower Cytokine Production by Monocytes as Compared to Other
Fevronia Kolonitsiou1, Matthaios Papadimitriou-Olivgeris2, Anastasia Spiliopoulou1
1Department of Microbiology, School of Medicine, University of Patras, Patras, Greece.
Abstract:
Methicillin-resistant Staphylococcus aureus (MRSA) remains an important cause of nosocomial and community-associated infections due to its ability to produce toxins and evade host's immune responses. The aim of the present study was to investigate the association of monocytes immune response in terms of cytokines produced after inoculation with different MRSA clones. Thirty-one clinical MRSA strains were selected on the basis of clonal types, accessory gene regulator (agr) groups and toxin genes carriage. Isolates were identified as S. aureus by Gram stain, catalase, coagulase production and PCR for nuc gene. The presence of mecA, lukS/lukF-PV (Panton-Valentine Leukocidin) and tst (Toxic Shock Syndrome Toxin-1) genes, as well as, the determination of agr groups was performed by PCR. Clonality was investigated by means of multi-locus sequence typing (MLST). Peripheral blood mononuclear cells were stimulated with live bacterial cells for 45 min at a ratio of 1:10. Cells were incubated for 10 h and supernatants were collected. The levels of Tumor Necrosis Factor alpha (TNFa), IL-1b, IL-8, IL-6, IL-12p40, IL-10, interferon-gamma (IFN-γ) and IL-2, were measured by Human Cytokine Multiplex Immunoassay kit. Thirteen strains were tst and 12 lukS/lukF-PV-positive. Seven strains belonged to ST80 and ST225, five to ST30 and ST239, while the remaining seven isolates were grouped together as "other." Strains belonging to ST80 induced statistically lower levels of TNFa, IL-1b, IL-8, IL-6, IL-10, IFN-γ, and IL-2. PVL-positive strains classified into ST80 clone induced statistically lower concentrations of most cytokines as compared to PVL-positive strains belonging to other clones, tst-positive strains and toxin-negative ones. Strains of agr3 group belonging to ST80 induced statistically lower concentrations of most tested cytokines as compared to agr3 strains not-belonging to ST80, agr2 or agr1. This low induction of immune response by MRSA ST80 cannot be attributed to the presence of neither lukS/lukF-PV nor agr3.
Insights
Methicillin-resistant Staphylococcus aureus (MRSA) ST80 clone shows a reduced immune response, producing lower cytokine levels. This immune evasion by MRSA ST80 is not linked to Panton-Valentine Leukocidin or agr3 group.
Area of Science:
- Immunology
- Microbiology
- Infectious Diseases
Background:
- Methicillin-resistant Staphylococcus aureus (MRSA) causes significant nosocomial and community infections.
- MRSA's ability to produce toxins and evade immune responses contributes to its virulence.
- Understanding the host-pathogen interaction is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the association between different MRSA clones and the immune response of monocytes.
- To analyze cytokine production by human peripheral blood mononuclear cells upon stimulation with various MRSA strains.
- To determine if specific MRSA clones, toxin genes, or accessory gene regulator (agr) groups influence cytokine profiles.
Main Methods:
- Selection of 31 clinical MRSA strains based on clonal types, agr groups, and toxin carriage.
- Identification of MRSA and detection of virulence genes (mecA, lukS/lukF-PV, tst) and agr groups using PCR.
- Multi-locus sequence typing (MLST) for clonality.
- Stimulation of peripheral blood mononuclear cells (PBMCs) with live MRSA strains and measurement of cytokines (TNFa, IL-1b, IL-8, IL-6, IL-12p40, IL-10, IFN-γ, IL-2) via multiplex immunoassay.
Main Results:
- MRSA ST80 strains induced significantly lower levels of multiple cytokines (TNFa, IL-1b, IL-8, IL-6, IL-10, IFN-γ, IL-2) compared to other MRSA clones.
- Panton-Valentine Leukocidin (PVL)-positive ST80 strains showed reduced cytokine induction compared to PVL-positive strains from other clones, tst-positive strains, and toxin-negative strains.
- MRSA strains belonging to the agr3 group and ST80 clone exhibited lower cytokine production than agr3 strains not belonging to ST80, or agr1/agr2 strains.
Conclusions:
- The MRSA ST80 clone is associated with a significantly attenuated host immune response, characterized by lower cytokine production.
- This immune evasion by MRSA ST80 is independent of the presence of Panton-Valentine Leukocidin (PVL) or the agr3 group.
- Further research is needed to elucidate the specific mechanisms behind MRSA ST80's immune-modulatory properties.
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