Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) sequence type (ST)398 is a livestock associated (LA) lineage with zoonotic potential, especially in humans with live pig contact. The objective of this study was to characterize two S. aureus strains of lineage ST398 (one methicillin-resistant (MRSA), one methicillin-susceptible (MSSA)) isolated from the same nasal sample of a patient admitted in the Intensive-Care Unit of a Spanish Hospital, and with previous occupational exposure to live pigs, by whole-genome-sequencing (WGS). The sample was obtained during routine surveillance for MRSA colonization. Purified genomic DNA was sequenced using Illumina HiSeq 2000 and processed using conventional bioinformatics software. The two isolates recovered were both S. aureus t011/ST398 and showed similar resistance-phenotypes, other than methicillin susceptibility. The possession of antibiotic resistance genes was the same, except for the mecA-gene located in SCCmecV in the MRSA isolate. The MSSA isolate harbored remnants of a SCCmec following the deletion of 17342bp from a recombination between two putative primases. Both isolates belonged to the livestock-associated clade as defined by three canonical single-nucleotide-polymorphisms, and neither possessed the human immune evasion cluster genes, chp, scn, or sak. The core genome alignment showed a similarity of 99.6%, and both isolates harbored the same mobile genetic elements. The two nasal ST398 isolates recovered from the patient with previous occupational exposure to pigs appeared to have a livestock origin and could represent different evolutionary steps of animal-human interface lineage. The MSSA strain was formed as a result of the loss of the mecA gene from the livestock-associated-MRSA lineage.
Highlights
Methicillin-resistant Staphylococcus aureus (MRSA) belonging to the sequence type (ST)398 is a livestock-associated (LA) lineage [1] found in people and animals, demonstrating little host species specificity
The two isolates recovered from the nasal sample of the pig truck driver were confirmed as S. aureus, one MRSA and the other methicillin-susceptible S. aureus (MSSA)
Multilocus sequence typing of the resulting assembly confirmed them to be ST398 and was used to identify the livestock-associated lineage canonical single-nucleotide polymorphisms (SNPs)
Summary
Methicillin-resistant Staphylococcus aureus (MRSA) belonging to the sequence type (ST)398 is a livestock-associated (LA) lineage [1] found in people and animals, demonstrating little host species specificity. Phylogenetic studies showed that this MRSA ST398 probably originated as a methicillin-susceptible S. aureus (MSSA) lineage found in humans, which subsequently spread to animals, where it acquired methicillin resistance [2]. The carriage of an animal lineage ST398 MRSA by a human subject is likely to have resulted from zoonotic transmission, either directly or indirectly. This lineage seems to ready colonize both people and livestock, and represents a significant proportion of human MRSA isolates in regions with a high density of pig farms
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
