Results of a five-year study of the spectrum of gram positive and gram negative pathogens in periprosthetic joint infection

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Introduction Periprosthetic joint infection (PJI) is a severe destructive process characterized by the formation of microbial biofilms that are difficult to treat. Staphylococcus aureus and coagulasenegative staphylococci ( CoNS ) are the most common pathogens. The spectrum of pathogens varies depending on the medical facility and requires regular monitoring. Purpose To monitor the pathogens of PJI in large joints for the period 2021–2025 in order to determine the spectrum of leading Gram-positive and Gram-negative microorganisms and analyze their temporal trends. Materials and Methods A single-center retrospective study of microbiological culture results was conducted in 218 patients with large joint PJI. The spectrum of pathogens and their temporal trends were studied. Statistical analysis was performed using the Pearson χ2 test. Results Positive cultures were obtained in 75.7 % of patients. A total of 225 microbial isolates were identified: gram-positive — 81.8 %, gram-negative — 17.8 %, fungi — 0.4 %. Microbial associations were detected in 26.1 %. In 10.3 % of patients, a change in pathogen spectrum was noted during treatment. Discussion The leading pathogens causing PJI are S. aureus (30.2 %), S. epidermidis (23.1 %), Corynebacterium spp . (7.1 %), P. aeruginosa (5.3 %), Enterococcus spp . (4.9 %), S. haemolyticus , K. pneumoniae , and E. coli (3.1 % each, respectively). For the period 2021–2025, an increase in the role of Corynebacterium spp ., CoNS and anaerobes ( C. acnes , Clostridium spp .), a decrease in the proportion of E. faecalis was noted. PJI is predominantly monomicrobial (73.9 %) with a ratio of Gram(+) to Gram(–) pathogens of 7:1. The most commonly isolated as single pathogens are MSSA (71.2 %), MRSE (73.2 %) and MSSE (72.7 %), while Enterococcus spp . (90.9 %), Corynebacterium spp . (75 %) and Gram(–) bacteria are more frequent in microbial associations. The identified microbial shift (10.3 %), including the emergence of new species ( B. cepacia , A. niger ) and highly resistant strains ( MRSA , resistant to vancomycin and linezolid), necessitates regular microbiological monitoring. Conclusion The leading Gram-positive pathogens are S. aureus , S. epidermidis , Corynebacterium spp ., Enterococcus spp ., and S. haemolyticus ; the leading Gram-negative pathogens are P. aeruginosa , K. pneumoniae , and E. coli . An increase in the role of Corynebacterium spp ., CoNS, and anaerobes was observed, along with a decrease in the proportion of E. faecalis . PJI retains a monomicrobial Gram‑positive pattern. The identified pathogen shift necessitates regular microbiological monitoring.