Microbiological Structure of Pathogens of Periprosthetic Infection of Large Joints in the Post-Covid Period

A continuous comparative retrospective study of cases of PJI of the joints of the extremities with positive microbiological growth of microorganisms in the pre-Covid (2018-2019) and post-Covid (2021-2022) periods was carried out on the data basis from the medical information system (MIS) of the Federal Center for Traumatology, Orthopedics and Arthroplasty of Ministry of Health of Russia (Cheboksary, Russia), hereinafter referred to as the Center. Verification of the diagnosis of deep PJI was carried out according to the diagnostic criteria of the Society for Musculoskeletal Infections. The sample included cases of deep and superficial infection after arthroplasty of the knee, hip, shoulder and wrist joints, regardless of the location of the primary operation. Isolated microorganisms were identified based on growth in one or more cultures obtained from punctate synovial fluid, intraoperative tissues, and from removed implants (after their ultrasonic treatment). The infection was classified as polymicrobial or monomicrobial. The role of the leading pathogen was determined in the structure of monomicrobial infection. Polymicrobial infection is represented by cases of simultaneous isolation of two or more pathogens in one patient. The antibiotic resistance profile included all isolated pathogens of mono- and polymicrobial PJI. At least 4 samples of intraoperative material (tissue biopsies, joint aspirate, removed endoprosthesis components) were taken from patients for examination. The aspirate from the joint was placed into FA plus, FN plus bottles of the Bact/Alert 3D analyzer (Bio Merieux, France). If the sample volume was insufficient (less than 1 ml), it was inoculated into a vial with Schedler's broth and, when turbid, subcultured onto solid media. The endoprosthesis components removed during surgery were placed in a sterile plastic container and delivered to the laboratory. In the laboratory, saline solution was added to the container and processed in an ultrasonic machine according to the author's method. After ultrasonication, 0.5 ml of the resulting liquid was applied to solid media. Homogenized tissue samples were placed in broth with thioglycollate medium. The cultures were incubated at 37°C for up to 14 days, subcultured on solid nutrient media: on the 1st day - on Columbia, Chocolate and Schedler agars; on the 5th day - on Chocolate and Schedler agar and on the 10th day - only on Schedler agar. For aerobic, anaerobic and capnophilic microorganisms, incubation conditions were created using gas-generating packages. Identification of isolated microorganisms and sensitivity to antibiotics was carried out using an automatic analyzer (Vitec2 compact; Bio Merieux, France) and a semi-automatic analyzer (Multiscan FC; Thermo Fisher, USA) using kits (Erba Lachema, Czech Republic), test systems ("Diagnostic systems", Russia). Sensitivity to antibacterial drugs was tested using the disk diffusion method and analyzer kits. Antibiotic sensitivity assessment was carried out in accordance with the criteria of EUCAST 2018 (studies in 2018-2019), EUCAST 2021 (studies in 2021-2022).