Microbiological profile of surgical site infections in orthopedic surgery at the university teaching hospital; Lusaka, Zambia.

Abstract

Background and purpose: Surgical site infection (SSI) is the infection to the surgical site occurring within a year of surgery (if an implant is used) or within 30 days if no implant is used. SSI is a known cause of poor outcomes, increased healthcare cost on patients, sometimes leading to significant disability and even death, following orthopaedic surgery the world over. The microbiological profile of SSI following orthopaedic surgery at University Teaching Hospital (UTH) in Lusaka, Zambia was unknown as, before this study, no such research had been conducted. The SSI following orthopaedic surgery at UTH was seen as a growing problem with the possibility of antimicrobial resistance. Hence, this study set out to investigate SSI following orthopaedic surgery in this setting, to determine the causative microorganisms, their prevalence and antimicrobial sensitivity patterns. Methods: A cross-sectional study was conducted at UTH, Lusaka, Zambia from March 2019 to March 2020. A structured questionnaire was used to collect data and sampling was done using a systematic random sampling after getting informed consent. Using AMIES pus swabs, samples were collected and sent to the microbiology laboratory at UTH for microscopy, culture and sensitivity studies. All cultures were done on three primary media MacConky, chocolate and blood agar, and the antimicrobial sensitivity studies for the cultured microorganisms were done on Mueller Hinton agar. STATA statistical software version 13 was used for the analysis of results obtained to come up with a microbiological profile of SSI. Results: A total of 119 (79 male and 40 female) participants were recruited. The mean age was 31.75 (SD, 17.07) of the participants; 66.4% of the participants were male. The HIV prevalence was 15.1%. Out of 119 participants, 100 had culture-positive results giving a prevalence of 84.0%. S. aureus was the most prevalent 35 (29.4%) causative microorganism, with MRSA comprising 54.3% of the S. aureus. Other prevalent organisms included Pseudomonas aeruginosa (P. aeruginosa) 17 (14.3%), Klebsiella oxytoca (K. oxytoca) 13 (10.9%), Proteus mirabilis (P. mirabilis) 13 (10.9%) and Coagulase-negative staphylococci (CNS) 7 (5.9%). Methicillin-resistance was 54.3% and 71.4% in S. aureus and CNS, respectively. Gentamicin sensitivity to S. aureus and CNS was 68.8% and 83.3%, respectively. P. aeruginosa exhibited relatively low resistance to most antibiotic classes. K. oxytoca and E. coli were resistant against most antimicrobial agents, including ciprofloxacin, co-trimoxazole, ampicillin/sulbactam, and third and fourth-generation cephalosporin. The percentages of the sensitive P. aeruginosa isolates against most antibiotics were relatively low in this study. There was no significant association between the various factors and SSI, each with a p-value greater than 0.05. Conclusions: The prevalence of culture-positive SSI was 84.0%. The most prevalent SSI causative microorganisms included S. aureus (29.4%), P. aeruginosa (14.3%), K. oxytoca (10.9%), P. mirabilis (10.9%) and CNS (5.9%). More than half of S. aureus was MRSA while CNS had more than two-thirds being methicillin-resistant. Gentamicin is a promising treatment for both S. aureus and CNS SSI. Third and fourth-generation cephalosporin, penicillin and co-trimoxazole had low susceptibility against most isolates. The relatively higher resistance of P. aeruginosa isolates against most antibiotics is a concern for possible drug resistance in the near future. Further studies on the risk factors, prevalence and incidence of SSI following orthopaedic operations should be done. Key Words: Surgical Site Infection, Microbiological Profile of SSI, Orthopaedic Surgery.