title: Can Methicillin-resistant Staphylococcus aureus Silently Travel From the Gut to the Wound and Cause Postoperative Infection? Modeling the "Trojan Horse Hypothesis".
abstract: To determine whether intestinal colonization with methicillin-resistant Staphylococcus aureus (MRSA) can be the source of surgical site infections (SSIs).
  
  
  
  We hypothesized that gut-derived MRSA may cause SSIs via mechanisms in which circulating immune cells scavenge MRSA from the gut, home to surgical wounds, and cause infection (Trojan Horse Hypothesis).
  
  
  
  MRSA gut colonization was achieved by disrupting the microbiota with antibiotics, imposing a period of starvation and introducing MRSA via gavage. Next, mice were subjected to a surgical injury (30% hepatectomy) and rectus muscle injury and ischemia before skin closure. All wounds were cultured before skin closure. To control for postoperative wound contamination, reiterative experiments were performed in mice in which the closed wound was painted with live MRSA for 2 consecutive postoperative days. To rule out extracellular bacteremia as a cause of wound infection, MRSA was injected intravenously in mice subjected to rectus muscle ischemia and injury.
  
  
  
  All wound cultures were negative before skin closure, ruling out intraoperative contamination. Out of 40 mice, 4 (10%) developed visible abscesses. Nine mice (22.5%) had MRSA positive cultures of the rectus muscle without visible abscesses. No SSIs were observed in mice injected intravenously with MRSA. Wounds painted with MRSA after closure did not develop infections. Circulating neutrophils from mice captured by flow cytometry demonstrated MRSA in their cytoplasm.
  
  
  
  Immune cells as Trojan horses carrying gut-derived MRSA may be a plausible mechanism of SSIs in the absence of direct contamination.
authors.affiliation: Center for Surgical Infection Research and Therapeutics, Pritzker School of Medicine, University of Chicago, Chicago, IL.
authors.forename: Monika A
authors.initials: MA
authors.lastname: Krezalek
authors.forename: Sanjiv
authors.initials: S
authors.lastname: Hyoju
authors.forename: Alexander
authors.initials: A
authors.lastname: Zaborin
authors.forename: Emeka
authors.initials: E
authors.lastname: Okafor
authors.forename: Laxmi
authors.initials: L
authors.lastname: Chandrasekar
authors.forename: Vitas
authors.initials: V
authors.lastname: Bindokas
authors.forename: Kristina
authors.initials: K
authors.lastname: Guyton
authors.forename: Christopher P
authors.initials: CP
authors.lastname: Montgomery
authors.forename: Robert S
authors.initials: RS
authors.lastname: Daum
authors.forename: Olga
authors.initials: O
authors.lastname: Zaborina
authors.forename: Susan
authors.initials: S
authors.lastname: Boyle-Vavra
authors.forename: John C
authors.initials: JC
authors.lastname: Alverdy
mesh_terms: D000038:Abscess / Q000382:microbiology; D000818:Animals; D000900:Anti-Bacterial Agents / Q000008:administration & dosage; D004195:Disease Models, Animal; D006498:Hepatectomy; D007422:Intestines / Q000382:microbiology*; D007511:Ischemia; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000276:immunology / Q000472:pathogenicity*; D008810:Mice, Inbred C57BL; D009504:Neutrophils / Q000276:immunology; D017568:Rectus Abdominis / Q000098:blood supply / Q000382:microbiology / Q000601:surgery; D012307:Risk Factors; D013203:Staphylococcal Infections / Q000382:microbiology*; D013530:Surgical Wound Infection / Q000382:microbiology*; D014774:Virulence
chemical_list: D000900:Anti-Bacterial Agents