Responses of swine associated methicillin-resistant Staphylococcus aureus against human lung carcinoma epithelial cell line A549

Abstract

Staphylococcus aureus (S. aureus) has been shown to adhere, invade, and induce the death of various host cells. The
prominent lineage of livestock-associated methicillin-resistant S. aureus (LA-MRSA) in Asia is the sequence type (ST) 9
that has emerged as a potential zoonotic pathogen. However, the virulence of LA-MRSA ST9 remains not clear. In this
study, sixteen representative Taiwan LA-MRSA isolates were selected for adherence, invasion, and cytotoxicity studies
against the human lung carcinoma epithelial cell line A549. The isolates showed 100% of cytotoxicity, 35.2% - 61% of
adhesion, and 18% - 52.5% of invasion against A549 cells. Different adherent abilities to A549 cells were found for the
isolates from swine nasal group (43.3±8.4%) and the isolates from environmental group (31.4±6.2%) (p < 0.05), but no
differences were found against A549 cells on invasion of both groups. Differences of cell cycle distribution in the
apoptotic (sub-G1) phase of the A549 cells were also noted, with significantly more cells in the swine nasal group than
that in environmental group, implying differential gene expression patterns resulting in physiological changes. This
study characterized the adhesion and invasion capabilities as well as the cytotoxicity of LA-MRSA ST9 isolates against
A549 cells for the first time. These findings reveal the risk for humans and animals to have potential invasion by this
novel emerging MRSA lineage. More attention is needed concerning the spread of this bacterium between hospitaland community-associated environments.