Polymerase chain reaction testing may detect bacterial species prior to infection
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TAMPA, Fla. — Results showed polymerase chain reaction testing may detect a spectrum of bacterial DNA species and allow for targeted treatment and prevention of surgical site infections in orthopedic surgery prior to signs of infection.
“This screening could be used to identify culprits of [surgical site infection] SSI prior to signs of infection and prior to surgery at times, thus, leading patient optimization protocols and decreasing negative outcomes,” Preston N. Wolfe said in his presentation at the Orthopaedic Research Society Annual Meeting.
Wolfe and colleagues collected two intraoperative swabs before and after open reduction and internal fixation among patients with either distal radius fractures or peri-articular ankle fractures, as well as swabs from the nasal and oral cavity, the skin surrounding the surgical site after intraoperative preparation and the joint immediately after arthrotomy among patients undergoing total hip, knee or shoulder arthroplasty. Researchers also left swabs exposed during the surgery to determine the potential ambient OR bacterial load profile.
Bacteria among fracture patients
Researchers extracted bacterial DNA from each swab and stored at –80°C until used for analysis of bacterial genome. After polymerase chain reaction testing of each swab, researchers identified and further analyzed samples with greater than 1,000 RNA sequences. Researchers also calculated the mean RNA sequences per collection site for each sample, identified the top three bacteria at each site and determined the mean percent of total bacterial load.
“The ambient OR sample had low levels of bacteria detected on the swabs, with the most prevalent bacteria present on the swabs not any of the common infection causing bacteria or ones that caused any infections in the study, which was good to see,” Wolfe said.
Wolfe noted no significant differences in bacteria load between before and after treatment time points among patients in the fracture group. One patient who tested positive for interior bacteria had an increase in bacterial load percentage of 10.9% before treatment compared with an average of 0.13% in non-infected patients and a bacterial load percentage of 18.6% after treatment compared with an average of 0.05% in non-infected patients, according to Wolfe.
Bacteria in total joint arthroplasty
While researchers found no infections in patients undergoing total shoulder arthroplasty, Wolfe noted Corynebacterium and Staphylococcus were the most abundant bacteria in patients undergoing total knee arthroplasty, with the nasal cavity having greater bacterial load than the joint or surrounding the skin of the joint.
“One patient did have an infection that showed symptoms and had a wound swab that had a growth of rare, identifiable gram-positive cocci bacterium,” Wolfe said. “Interestingly, this patient had a preoperative nasal swab that contained 95.3% of the bacterial load as a Streptococcus bacteria, which is dramatically increased from the average non-infected 16.6%.”
He added patients undergoing total hip arthroplasty had similar bacterial profiles in the nasal and oral cavity as patients undergoing TKA compared with the joint and skin locations.
“One of the patients did have an infection, as well, and its wound swab did produce a rare Staphylococcus species growth,” Wolfe said. “So, the patient that did have this infection had a joint swab that contained 33.6% of its bacterial load of Staphylococcus compared to the average of 4.5% and, once again, we saw the nasal swab had an increase of Staphylococcus in this infected patient at 98% of its bacterial load compared to the average of 32.3%.”
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Wolfe P, et al. Paper 185. Presented at: Orthopaedic Research Society Annual Meeting; Feb. 4-8, 2022; Tampa, Fla.
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