Microbiological Profile of Orthopaedic Implant Associated Infections: A Prospective Study

Abstract

Introduction: The incidence of orthopaedic implantation and implantation associated infections were correspondingly increasing among the elderly and trauma patients. The resistance among the pathogens pose a unique challenge to the clinicians in the management of the infection. Extended-Spectrum Beta-Lactamase (ESBL), AmpC beta-lactamases (AmpC), Metallo Beta-Lactamases (MBL) and Methicillin-Resistant Staphylococcus aureus (MRSA) producing bacterial pathogens are responsible for a high rate of relapsing infections and outbreaks of nosocomial infections. Aim: To focus on accounting the incidence of ESBL, AmpC, MBL and MRSA and its antibiogram for effective management of implant associated infection. Materials and Methods: The present study was a prospective observational study which was conducted using various samples like pus, wound swab, serous discharge. These samples were collected under aseptic precautions in sterile containers for the period of one year (February 2015-February 2016). A total of 200 samples were inoculated on Blood agar and McConkey agar and identified. The isolates were tested for detection of ESBL, AmpC, MBL and MRSA as per standard protocol. The statistical analysis was performed using Statistical Package for the Social Sciences (SPSS) software version 20.0 Chicago, USA. Results: Most commonly used implants were intramedullary interlocking nail 138 (65.7%) followed by dynamic compression plates 23 (11.0%) and anatomical plates 18 (8.6%). Of the total of 200 samples, 190 (95%) samples yielded monomicrobial isolates and 10 (5%) samples yielded polymicrobial isolate. gram negative isolates 108 (51.4%) were marginally higher than gram positive isolates 102 (48.6%). The predominant isolate was S. aureus 81 (38.5%) followed by Klebsiella spp. 28 (13.3%) and Pseudomonas aeruginosa 21 (10.0%). In gram negative isolates, 76 (70.4%) were ESBL and/or AmpC producers. Of which, 48 (44.4%) were ESBL and AmpC co-producers. There were no MBL producing isolates. In gram positive isolates, majority were S. aureus 81 (79.4%) followed by Coagulase-negative Staphylococcus 21 (20.6%). Out of 81 S. aureus isolates, 46 (56.8%) were MRSA. Out of 21 CoNS, majority 17 (81%) isolates were methicillin-resistant. Implant failures were observed in 28 (14%) cases. Out of 28, majority 12 (42.8%) of the implant failures were MRSA. Conclusion: High rates of ESBL, AmpC and MRSA infections associated with implant surgeries indicate the necessity to formulate antibiotic policies and control measures. ESBL and AmpC producing strains were found to show higher rates of resistance to the various class of antibiotics when compared to non-ESBL and non-AmpC producers. MRSA isolates were found to show higher rates of resistance to various classes of antibiotics when compared to MSSA.

Keywords

• extended-spectrum beta-lactamase
• implant infections
• staphylococcus aureus