Instrument

• Genetic data from the bacteria causing these infections – think CSI for E. coli – tells another story: Most health care-associated infections are caused by previously harmless bacteria that patients already had on their bodies before they even entered the hospital.
• We show that many surgical site infections after spinal surgery are caused by microbes that are already on the patient’s skin.

Surgical infections are a persistent problem

• Among the different types of heath care-associated infections, surgical site infections stand out as particularly problematic.
• A 2013 study found that surgical site infections contribute the most to the annual costs of hospital-acquired infections, totaling over 33% of the US$9.8 billion spent annually.

• Still, surgical site infections occur following about 1 in 30 procedures, typically with no explanation.
• While rates of many other medical complications have shown steady improvement over time, data from the Agency for Healthcare Research and Quality and the Centers for Disease Control and Prevention show that the problem of surgical site infection is not getting better.

BYOB (Bring your own bacteria)

• Prior studies on surgical site infection have been limited to a single species of bacteria and used older genetic analysis methods.
• But new technologies have opened the door to studying all types of bacteria and testing their antibiotic resistance genes simultaneously.
• Over a one-year period, we sampled the bacteria living in the nose, skin and stool of over 200 patients before surgery.

• In fact, 86% of the bacteria causing infections after spine surgery were genetically matched to bacteria a patient carried before surgery.
• That number is remarkably close to estimates from earlier studies using older genetic techniques focused on Staphylococcus aureus.
• They likely acquired these antibiotic-resistant microbes through prior antibiotic exposure, consumer products or routine community contact.

Preventing surgical infections

• At face value, our results may seem intuitive – surgical wound infections come from bacteria that hang out around that part of the body.
• If the most likely source of surgical infection – the patient’s microbiome – is known in advance, this presents medical teams with an opportunity to protect against it prior to a scheduled procedure.
• The fact that most infections don’t actually start with sources in the hospital is probably a testament to the efficacy of these protocols.

Dustin Long receives funding from the National Institutes of Health. Dr Bryson-Cahn receives funding from the Gordon and Berry Moore Foundation and is the co-medical director for Alaska Airlines.