Location: Virus and Prion ResearchTitle: Complete genome sequences of two Staphylococcus aureus ST5 isolates from California, USA
Submitted to: Genome Announcements
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/2/2017
Publication Date: 3/30/2017
Citation: Hau, S.J., Bayles, D.O., Alt, D.P., Nicholson, T.L. 2017. Complete genome sequences of two Staphylococcus aureus sequence type 5 isolates from California, USA. Genome Announcements. 5:e00099-17. doi.org/10.1128/genomeA.00099-17.
Interpretive Summary: Staphylococcus aureus causes a variety of human diseases ranging in severity. The pathogenicity of S. aureus can be partially attributed to their acquisition of mobile genetic elements. In this report, we provide two complete genomes from human clinical S. aureus isolates.
Technical Abstract: Staphylococcus aureus is a bacteria that can cause disease in humans and animals. S. aureus bacteria can transfer or exchange segments of genetic material with other bacteria. These segments are known as mobile genetic elements and in some instances they can encode for factors that increase the ability of bacteria to cause disease. The best known example of a staphylococcal mobile genetic element is the segment of DNA that contains the gene encoding resistance to the antibiotic methicillin, referred to as the staphylococcal cassette chromosome mec (SCCmec) element. The SCCmec element is easily transferred from one S. aureus bacterial strain to another and has been found in S. aureus isolates recovered from swine. The emergence and prevalence of livestock- associated (LA-MRSA) sequence type (ST) 398 isolates in Europe has been attributed in part to the in-feed use of zinc as an antidiarrheal agent. Since the gene encoding zinc resistance (czrC) and the gene encoding methicillin resistance are collocated on the SCCmec element, it has been suggested that the use of in feed zinc as an antimicrobial has the potential to contribute to the emergence and spread of MRSA in swine by increasing the selective pressure to maintain the SCCmec element in isolates from pigs. While investigating the gene encoding zinc resistance among S. aureus strains isolated from humans and swine, 16 human strains were identified to carry the czrC gene. In this report, we provide the complete genome sequence for two of these human isolates to demonstrate the czrC gene is located within the SCCmec element and nowhere else within the genome of these strains. Our data suggest that co-selection thought to be associated with the use of zinc in-feed as an antimicrobial agent is not playing a role in the emergence of livestock-associated methicillin resistant Staphylococcus aureus (LA-MRSA) ST5 in the US swine population. Additionally, our data indicate that zinc resistance is more associated with multi locus sequence type (MLST) lineage, suggesting a potential link between genetic lineage and carriage of genes encoding antibiotic resistance. This information is important to public health professionals, veterinarians, producers, and consumers because it can be used to ascertain the origin, evolution, and zoonotic potential of livestock-associated methicillin-resistant S. aureus found in US swine farms.