Clinical and Microbiological Profile of Chronic Osteomyelitis Cases with Reference to Virulence Markers in Staphylococcus aureus

Abstract

A B S T R A C T BACKGROUNDDue to increase in road traffic accidents resulting in compound fractures and also increase in the number of orthopaedic surgeons using implants, iatrogenic and chronic osteomyelitis is being encountered more frequently. The objective of this study was to describe clinical and microbiological characteristics of acute and chronic osteomyelitis with regard to virulence markers and antibiogram of isolates to prevent unnecessary morbidity and mortality. METHODSA total of 148 samples like pus or exudates or pieces of necrotic tissues were collected during surgery, if possible, otherwise aspirated. All samples were subjected to Gram staining and culture. Various organisms were identified by standard methods. Various virulence determinants were detected by phenotypic tests. Kirby-Bauer method was employed to perform the antimicrobial susceptibility on Mueller-Hinton agar [MHA]. For detection of methicillin-resistant Staphylococcus aureus (MRSA), MHA supplemented with 4% NaCl was used. RESULTSOut of the 148 cases studied, 110 (74.3%) were male and 38 (25.6%) were female. The predominant number of osteomyelitis cases was found in the age group of 26-30 years, of these 48.5% (16/33) occurred following orthopaedic implants and 24.2% (8/33) due to post-operative wound infections. Staphylococcus aureus was the main isolate [43.9% (58/132)]. Escherichia coli [44.4% (4/9)] was the predominant isolate in the age group 36-40 years. The only isolate in the age group 46-50 years was Pseudomonas aeruginosa [100% (2/2)]. Almost all the bones were involved in all age groups, but spine was mainly infected in the 46-50 years age group. Differences in the presence of clumping factor, DNase, phosphatase, lipase, gelatinase, and presence of haemolysis on blood agar in MRSA were statistically insignificant (p= 0.13, 0.27, 0.95, 0.22, 0.40, 0.92 respectively) as compared to MSSA strains. CONCLUSIONSMRSA strains expressing some virulence factors with multi drug resistance might play a role in pathogenesis of osteomyelitis. Therefore, novel therapeutics targeting these virulence markers, instead of conventional antibiotic therapy, as well as following new guidelines, should take place in the future that might aid in the prevention and control of MRSA infections in our hospitals.