Finding the Pearls in a Sea of Propionibacterium Acnes After Orthopaedic Hip and Knee Surgeries

Abstract

Background In January 2019, Infection Prevention (IP) was alerted of four patients with positive cultures from orthopedic surgeries with Proprionibacterium acnes (P.acnes) in the same week. This prompted an investigation into a possible outbreak. P.acnes in shoulders and other sterile body sites have previously been described in the literature. Methods Chart reviews were completed on the initial four cases and prospective surveillance for additional cases was initiated. All cases were reviewed for surgical site infection (SSI) criteria per Centers for Disease Control (CDC) definitions. Chart review included: Operating rooms (ORs), personnel, surgery duration, prior orthopedic surgery, prior joint injections, history of diabetes, ASA score, skin prep, hair removal, pre-op antibiotics and implants. OR observations were performed by IP to evaluate scrub technique, skin prep, culturing technique, and additional OR activities. Results Through May 2019, twelve additional cases were identified. No cases met CDC SSI criteria and no obvious breaches in technique were observed. Chart reviews revealed few commonalities of concern. Of the 16 patients, 42 cultures were collected and 36% grew <1+ P. acnes. Days to positivity ranged from 4-15 days with a mean of 7.5 days. Whole genome sequencing (WGS) was performed by an outside laboratory on isolates from the 16 distinct patients. Three isolates were identified by WGS as highly related and should be considered clonal. Two of the four initial cases from January were clonally related by WGS while the other clonally related isolate was from a surgery in May. Thirteen of the cases were not clonally related and likely represent a pseudo-outbreak. Conclusions Through WGS we were able to identify the clonally related cases, and focus on the true outbreak. Infection Preventionists (IPs) should consider molecular technology like WGS to better identify potentially linked cases especially in settings like orthopedic surgery with high rates of culturing. In January 2019, Infection Prevention (IP) was alerted of four patients with positive cultures from orthopedic surgeries with Proprionibacterium acnes (P.acnes) in the same week. This prompted an investigation into a possible outbreak. P.acnes in shoulders and other sterile body sites have previously been described in the literature. Chart reviews were completed on the initial four cases and prospective surveillance for additional cases was initiated. All cases were reviewed for surgical site infection (SSI) criteria per Centers for Disease Control (CDC) definitions. Chart review included: Operating rooms (ORs), personnel, surgery duration, prior orthopedic surgery, prior joint injections, history of diabetes, ASA score, skin prep, hair removal, pre-op antibiotics and implants. OR observations were performed by IP to evaluate scrub technique, skin prep, culturing technique, and additional OR activities. Through May 2019, twelve additional cases were identified. No cases met CDC SSI criteria and no obvious breaches in technique were observed. Chart reviews revealed few commonalities of concern. Of the 16 patients, 42 cultures were collected and 36% grew <1+ P. acnes. Days to positivity ranged from 4-15 days with a mean of 7.5 days. Whole genome sequencing (WGS) was performed by an outside laboratory on isolates from the 16 distinct patients. Three isolates were identified by WGS as highly related and should be considered clonal. Two of the four initial cases from January were clonally related by WGS while the other clonally related isolate was from a surgery in May. Thirteen of the cases were not clonally related and likely represent a pseudo-outbreak. Through WGS we were able to identify the clonally related cases, and focus on the true outbreak. Infection Preventionists (IPs) should consider molecular technology like WGS to better identify potentially linked cases especially in settings like orthopedic surgery with high rates of culturing.