title: Genomic Heterogeneity of Methicillin Resistant Staphylococcus aureus Associated with Variation in Severity of Illness among Children with Acute Hematogenous Osteomyelitis.
abstract: BACKGROUND
  The association between severity of illness of children with osteomyelitis caused by Methicillin-resistant Staphylococcus aureus (MRSA) and genomic variation of the causative organism has not been previously investigated. The purpose of this study is to assess genomic heterogeneity among MRSA isolates from children with osteomyelitis who have diverse severity of illness.
  
  
  METHODS
  Children with osteomyelitis were prospectively studied between 2010 and 2011. Severity of illness of the affected children was determined from clinical and laboratory parameters. MRSA isolates were analyzed with next generation sequencing (NGS) and optical mapping. Sequence data was used for multi-locus sequence typing (MLST), phylogenetic analysis by maximum likelihood (PAML), and identification of virulence genes and single nucleotide polymorphisms (SNP) relative to reference strains.
  
  
  RESULTS
  The twelve children studied demonstrated severity of illness scores ranging from 0 (mild) to 9 (severe). All isolates were USA300, ST 8, SCC mec IVa MRSA by MLST. The isolates differed from reference strains by 2 insertions (40 Kb each) and 2 deletions (10 and 25 Kb) but had no rearrangements or copy number variations. There was a higher occurrence of virulence genes among study isolates when compared to the reference strains (p = 0.0124). There were an average of 11 nonsynonymous SNPs per strain. PAML demonstrated heterogeneity of study isolates from each other and from the reference strains.
  
  
  CONCLUSIONS
  Genomic heterogeneity exists among MRSA isolates causing osteomyelitis among children in a single community. These variations may play a role in the pathogenesis of variation in clinical severity among these children.
authors.affiliation: Department of Pediatric Infectious Disease, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America.
authors.forename: Claudia
authors.initials: C
authors.lastname: Gaviria-Agudelo
authors.affiliation: Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America.
authors.forename: Chukwuemika
authors.initials: C
authors.lastname: Aroh
authors.affiliation: Children's Medical Center, Dallas, Texas, United States of America.
authors.forename: Naureen
authors.initials: N
authors.lastname: Tareen
authors.affiliation: Department of Immunology, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America.
authors.forename: Edward K
authors.initials: EK
authors.lastname: Wakeland
authors.affiliation: Department of Biomedical Informatics, University of Texas Southwestern Medical Center, Dallas, TX, United States of America.
authors.forename: MinSoo
authors.initials: M
authors.lastname: Kim
authors.affiliation: Children's Medical Center, Dallas, Texas, United States of America; Texas Scottish Rite Hospital for Children, Dallas, Texas, United States of America; Department of Orthopaedic Surgery, University of Texas Southwestern Medical Center, Dallas, Texas, United States of America.
authors.forename: Lawson A
authors.initials: LA
authors.lastname: Copley
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003710:Demography; D018740:Genetic Heterogeneity; D059014:High-Throughput Nucleotide Sequencing; D006801:Humans; D007223:Infant; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D058885:Multilocus Sequence Typing; D010019:Osteomyelitis / Q000378:metabolism / Q000382:microbiology / Q000473:pathology*; D010802:Phylogeny; D020641:Polymorphism, Single Nucleotide; D011446:Prospective Studies; D017422:Sequence Analysis, DNA; D012720:Severity of Illness Index; D013203:Staphylococcal Infections / Q000378:metabolism / Q000382:microbiology / Q000473:pathology*; D014774:Virulence / Q000235:genetics