ASSESSMENT OF THE FREQUENCY OF ISOLATED MICROORGANISMS AND CHANGE OF THEIR ANTIBIOTIC RESISTANCE OVER TIME AFTER PRIMARY AND REVISION KNEE ARTHROPLASTIES AT A TERTIARY REFERRAL HOSPITAL

OBJECTIVE: Increased number of total knee arthroplasty has led to an increases the risk of periprosthetic joint infection (PJI) and other complications over time. Therefore, the current trends in infection and microbiology data are necessary to be understood to prevent and treat knee PJI. For this reason, we aimed to identify the course of bacterial species isolated after revision total knee arthroplasty and to investigate the change of antibiotic resistance over time.MATERIAL AND METHODS: Two groups of patients were evaluated, retrospectively. Group 1 consisted of patients who had surgery that caused the development of infection performed between 2005 and 2011 while group 2 consisted of patients between 2012 and 2018. The variation of isolated microorganisms species and their antibiotic resistances over time were investigated. Cefazolin (clindamycin in case of allergy) was the antibiotic used for routine prophylaxis between 2005 and 2018.RESULTS: Overall, 42 patients (43 knee joints) were included in the study. The most frequently isolated bacterium was Staphylococcus epidermidis while Staphylococcus aureus was the second most isolated bacterium in groups 1 and 2. An increased rate of gram-negative bacteria (Pseudomonas aeruginosa) isolation was observed in time. According to statistical analysis, a significant increase in antibiotic resistance to ciprofloxacin (p=0.0021), gentamicin (p=0.0001), tetracycline (p=0.043) and trimethoprim/sulfamethoxazole (p=0.0016) were observed over time. No increased antibiotic resistance observed over time against clindamycin (p=0.88) which we used in case of cefazoline allergy. Cefazoline resistance significantly decreased during 2012 and 2018 (p<0.0001). Vancomycin resistance was observed in only one patient.CONCLUSIONS: Our results and the literature has showed a steady increase in gram-negative bacteria isolation rates in patients with PJI. Therefore, it will become more necessary to use prophylactic antibiotic regimens including gram-negative bacteria in knee arthroplasty surgery. Although an increased resistance to ciprofloxacin, gentamicin, tetracycline and trimethoprim/sulfamethoxazole was found over time in the current study, these were not the antibiotics we used for routine prophylaxis. Instead of using cefazolin or clindamycin alone for prophylaxis, it is necessary to combine these anatibiotics with gentamicin.