Microbiological Epidemiology at Chris Hani Baragwanath Academic Hospital: Poly-Microbial Osteomyelitis Analysis

Background: The majority of the patients seen and treated at our clinical setting present during chronic osteomyelitis stage, which is anecdotally likely to be poly-microbial. Adults with poly-microbial infection have a predilection for gram-negative bacteria and anaerobes, a scenario that hypothetically leads to a higher morbidity of poly-microbial osteomyelitis following high-energy trauma. Our study looks into the epidemiology of poly-microbial osteomyelitis treated at our Tumour and Infection unit. Methods: This was a retrospective study of patients treated for osteomyelitis from 1st of June 2016 to 30th of May 2021. Medical records of eligible patients were retrieved for examination. Demographic data such as age, sex and race were recorded. Clinical presentation, and organisms cultured, including their anti-microbial sensitivities were documented. Results: There were 63 participants in the study. Thirty-one (49.21%) participants had mono-microbial osteomyelitis with 32 (50.79%) participants having poly-microbial osteomyelitis. Majority of the poly-microbial patients presented with a draining sinus (68.75%) and most was located in the tibia (50%). Multiple mixed pathogens (both gram-positive and gram-negative) were cultured in combination in our patients and this comprised 71.21% of the total bacteria cultured. Staphylococcus Aureus was the commonest bacteria (30%) isolated, followed by Enterococcus faecalis (12%). The commonest gram-negative bacteriae cultured was Enterococcus cloacae (10%) followed by Acinetobacter baumannii at 7%. Most enterobacteriacae species were sensitive to Ertapenem and Ceftazidime. Conclusion: A slightly higher incidence of poly-microbial osteomyelitis was found in our study than that reported in literature. Furthermore, our study demonstrated a wide variety of organisms found in poly-microbial osteomyelitis, with a large contribution made by gram-negative anaerobic rod-shaped bacteria. Cephalosporins were not shown to be valuable as broad-spectrum cover drugs, and most bacteria cultured were found to be insensitive to them. What we suggest is tailoring antibiotics to the specific cultured bacteria and sensitivity. Prompt management of patients with open fractures with early administration of intravenous antibiotics and adequate surgical management may lead to a reduction in the prevalence of chronic osteomyelitis.