A Comparative study of microbial population heterogeneity resistance to antibiotics in tissue culture and sonication fluid culture in explanted internal fixation components

Abstract

Background. Periprosthetic joint infection (PJI) is one of the most demanding complications in reconstructive hip and knee surgery. Accurate microbiological diagnosis of periprosthetic infections is critical because decisively influences the direction of treatment (antibacterial treatment and surgical rehabilitation) and the course of surgery.“Heterogeneity” describes a phenomenon where subpopulations of seemingly isogenic bacteria exhibit a range of susceptibilities to a particular antibiotic Purpose. The aim of this study is to investigate the change in resistance of microbes isolated after PJI, as well as the correlation of microbial resistance to conventional antimicrobial antibiotics.

Methods. Between May 2014 and June 2019, we investigated 76 patients, at our institution, undergoing revision osteosynthesis, because of loosening of the prostheses or because of PJI. All patients had periprosthetic tissue culture, sonication of prosthesis and direct inoculation of SF into blood culture bottles. We calculated the sensitivity, specificity, positive predictive value, and negative predictive value of each method separately as well as their combination.

Results. Using standard non-microbiological criteria to determine PJI, it was found that 29 patient (61.8%) had aseptic loosening while 47 patients (38.2 %) had PJI. Comparing the two methods, the results of our study showed that the method of sonication was significantly more sensitive than tissue culture [45% (30-60) vs 91.5% (79-97); p<0.005]. In a twenty-six (26) patients out of forty-seven (47) the diagnosis of peri-prosthetic infection was performed only by the method of sonication as no bacteria were detected by the conventional method. In this study, heterogeneity was reported in 6 cases. This figure represents 12.8% of all infections (47 records) and 2.5% in the total population (76 participants). In our study, S. epidermidis was the most commonly isolated strain followed by S. aureus, at a rate of 36.0% and 17.0%, respectively. Antibiotics in which the microorganisms exhibited heterogeneous bacterial behavior most frequently were Gendamicin (5.9%), Vancomycin (5.4%), Tigecycline (5,8%) and Oxacillin (5.0%).

Conclusions. There is increasing evidence that heterogeneity can lead to therapeutic failure and that the detection of this phenotype is a prerequisite for a proper antibiotic choice to have a successful therapeutic effect. The ability of sonication method to detect heterogeneity resistance of microbial populations may reduce the therapeutic failures of the administered antimicrobial treatment.