Microbiology of Implant-Associated Infection

Abstract

Objective: to study the specifics of the infection process and its diagnostics through microbiological analysis of biomaterials harvested from patients with implant-associated infection. Materials and methods: 234 strains of gram-negative and gram-positive bacteria isolated from 168 samples of clinical material harvested from patients with inflammatory infectious complications after knee replacement. Wound discharge, aspirates, homogenized biopsy samples of periarticular soft tissues as well as sonication liquid received after ultrasound treatment of the removed endoprosthesis components were investigated. Microbiology examinations were run using differential diagnostic media and Crystal Autoreader (Becton Dickinson, USA) analyzer. Biofilm formation ability was estimated with the method proposed by О'Toole et al. that involved gentian violet binding and the degree of stain spectrofluorimetric absorption. Results: The prevalence of gram-positive cocci flora in the etiologic structure of periprosthetic infection pathogens was found; it accounted for 72.4 per cent of cases. A large number of mixed infections were observed; it was also established that the frequency of epidemiologically relevant and clinically significant pathogens in microbial associations was higher than that in monoculture. The informative value of various methods for microbiological diagnostics of periprosthetic infection was investigated, the most sensitive and specific methods were proposed. High ability for biofilm formation was found in implant-associated infection pathogens, the kinetics of biofilm formation and the effect of various antibiotic concentrations on it was researched. Conclusions: There are certain specifics in microbiological diagnostics of infectious complications after large joint replacements related to the sessile form of pathogens existence. The microbiological diagnostics therefore needs to be changed and methodological approaches optimized.