Adherence capacity of methicillin resistant Staphylococcus aureus sequence type (ST) 5 isolates from health care and agricultural sources

Authors: HAU, SAMANTHA - Iowa State University; Kellner, Steven; EBERLE, KIRSTEN - Orise Fellow; WAACK, URSULA - Orise Fellow; Brockmeier, Susan; SUN, JISUN - University Of Minnesota; DAVIES, PETER - University Of Minnesota; FRANA, TIMOTHY - Iowa State University; Nicholson, Tracy

Submitted to: Applied and Environmental Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/28/2017
Publication Date: 1/15/2018
Citation: Hau, S.J., Kellner, S., Eberle, K.C., Waack, U., Brockmeier, S.L., Haan, J.S., Davies, P.R., Frana, T., Nicholson, T.L. 2018. Methicillin-resistant Staphylococcus aureus sequence type (ST) 5 isolates from health care and agricultural sources adhere equivalently to human keratinocytes. Applied Environmental Microbiology. 84(2):e02073-17. https://doi.org/10.1128/AEM.02073-17.
DOI: https://doi.org/10.1128/AEM.02073-17

Interpretive Summary: Livestock-associated methicillin-resistant Staphylococcus aureus (LA-MRSA) isolates raise public health concerns because of the potential for livestock to act as a reservoir for MRSA outside of the hospital setting. In the United States, swine harbor a mixed population of LA-MRSA isolates with the sequence type (ST) 398, ST9, and ST5 lineages being detected. LA-MRSA ST5 isolates are particularly concerning to the public health community because, while the ST398 and ST9 lineage are considered livestock adapted and are thought to be less able to colonize and cause disease in humans, the ST5 lineage is globally disseminated and a significant cause of disease in both the hospital and community setting. The ability of ST5 isolates to cause disease in humans is believed to result from acquisition of mobile genetic elements encoding virulence or host-adapted genes. This report assessed the ability of two subsets of MRSA ST5 isolates (swine associated LA-MRSA and clinical human MRSA) to adhere to human tissue culture cells and evaluated adherence genes harbored by these isolates. Both subsets of isolates adhered equivalently to human keratinocytes and contained an undistinguishable complement of adherence genes that possessed a high degree of sequence identity. Collectively our data indicate that, unlike LA-MRSA ST398 isolates, LA-MRSA ST5 isolates did not exhibit a reduced genotypic or phenotypic capacity to adhere to human keratinocytes.

Technical Abstract: Staphylococcus aureus is part of the nasal microbiome of many humans and has become significant public health burden due to infections with antibiotic resistant versions, including methicillin resistant S. aureus (MRSA). A subset of these isolates are found in livestock species and acquired by humans through contact with animals. These livestock associated MRSA (LA-MRSA) isolates raise public health concerns because of the potential for livestock to act as a reservoir for MRSA outside of the hospital setting. In the United States, swine harbor a mixed population of LA-MRSA isolates with the sequence type (ST) 398, ST9, and ST5 lineages being detected. LA-MRSA ST5 isolates are particularly concerning to the public health community because, while the ST398 and ST9 lineage are considered livestock adapted and are thought to be less able to colonize and cause disease in humans, the ST5 lineage is globally disseminated and a significant cause of disease in both the hospital and community setting. The ability of swine associated LA-MRSA ST5 isolates to adhere to human keratinocytes in vitro was investigated and adherence genes harbored by these isolates were evaluated and compared to clinical MRSA ST5 isolates from humans with no swine contact. The two subsets of isolates adhered equivalently to human keratinocytes in vitro and contained an undistinguishable complement of adherence genes that possessed a high degree of sequence identity. Collectively our data indicate that, unlike LA-MRSA ST398 isolates, LA-MRSA ST5 isolates did not exhibit a reduced genotypic or phenotypic capacity to adhere to human keratinocytes.