Osteomyelitis is an acute or chronic inflammation of the bone caused by an infectious organism and is a challenging clinical problem. It is essential to identify the etiological agents to treat the infection.

The present study, after investigating a cohort of 57 patients, found that the mean age of patients was 46.4 years & 78.9% of patients were male. Similar results were found by Jiang N et al. where they found the median age to be 42 years & increased male predilection¹.

We observed out of 57 cases, 73.7 % of them had chronic osteomyelitis and a significant number of them were in the age group of 31-60 years (30/42, 71.4%). Similarly, Prieto-Pérez et al.² found more number of chronic osteomyelitis cases among patients within the age group of 41- 60 years. The incidence of acute osteomyelitis was only 26.3%. Acute osteomyelitis is more common in children less than five years of age due to bacteremic seeding of bone¹⁸. As we have not included children in our study, so less number of acute osteomyelitis had been depicted. Chronic osteomyelitis is much less observed among children^3.

Several etio-pathogenic mechanisms for osteomyelitis were reported in the past. Infection can occur secondary to a contiguous-focus, by direct contamination after trauma or surgery or infections originating from the bloodstream⁴. In this study, we found, most of the disease developed by direct inoculation (45/57, 78.9%) of bacteria or by seeding of them from next focus (31.6%). Jorge SL et al. also depicted that the incidence of osteomyelitis by direct inoculation has increased over the last decades⁵. This is due to the increased frequency of accidents followed by more use of orthopaedic fixation devices and joint prostheses. Traditional chronic hematogenous osteomyelitis is now supplemented by frequently encountered postop (33.3%), post-traumatic (28%) & implant-related infection (33.3%)⁶. The primary underlying predisposing factor was diabetes (36.8%) for acute & chronic osteomyelitis secondary to contagious soft tissue infection. It has been reported that up to one-half of patients with dia­betes develop peripheral neuropathy, which may reduce their awareness of wounds and increase the risk of unrecognized infections.

The metatarsal bones of the foot followed by the tibia and femur were the most commonly affected bones in our study (38.6%, 22.8% & 15.9% respectively). Jiang N et al.¹ observed the tibia was the most common site in traumatic osteomyelitis, while the femur and toes were the most common sites in hematogenous and diabetic foot osteomyelitis. We found frequent infection in metatarsal bones as a complication of diabetic foot.

Clinical symptoms of osteomyelitis can be nonspecific and difficult to recognize. Signs and symptoms change depending on the category of infection, organism & anatomical location of the disease. In our study, the majority of the patients with osteomyelitis presented with pain (79.4%) & discharging sinus (76.5%). Pain & discharging sinuses were common clinical presentations in chronic cases, whereas pain & swelling were frequent in acute cases.

During the study period, a total of 86 samples were collected from 57 patients for microbiological analysis. Out of 57patients, monomicrobial infection observed among 55.3% of patients & co-infection was 42.6%. In our study, the majority of postoperative and post-traumatic infections were caused by two microbes (12/27=44.4%) similar to Mathewa PG et al.²⁶ but higher than Trampuz et al. (27%)⁷. Monomicrobial infection by Gram positive bacteria was commonly observed (9/16, 56.2%) in contagious osteomyelitis due to the spread from adjacent ulcer site. This is in contrast to Calhoun JH et al.⁸.

Staphylococcus aureus (46.9%) was the most frequently isolated bacteria overall similar to Lobati F et al⁹. We also had a fair number of beta-hemolytic Streptococcus spp (20%) from chronic cases. Generally, they are frequent etiological agent among children, rare in adults¹⁰.

In view of chronic osteomyelitis, PG Mthethwa et al.¹¹ found Enterobacterales as a most common organism (34%). In contrast, we found S. aureus as the most prevalent organism for both acute (46%) & chronic infection (50%) followed by Enterobacterales (18.8%& 24% respectively). Prevalence of P. aeruginosa in our study was 9.1% similar to other study (11%)¹¹.

Out of 31 isolates of S.aureus, 41.9% were MRSA with 100% of them being susceptible to vancomycin. Reason for the high number of MRSA could be that most of our cases were having post-traumatic or post-op infection. They showed high susceptibility for co-trimoxazole (80.6%) which have been found to achieve bone concentrations at ∼50% of serum & as effective as vancomycin. Other than co-trimoxazole, clindamycin is another oral agent available against community-acquired MRSA, which reliably penetrates bone at levels of approximately 40%–70% of serum. In our study, susceptibility of clindamycin was 76.9%¹². We also found, out of 15 Enterobacterales, more than 80% of them were ESBL producers, resistant to ampicillin, amoxy-clavulanic acid & first, second & third generation of cephalosporins. More than 80% of the ESBL producers were susceptible to carbapenem, piperacillin-tazobactam & cefepime similar to Mthethwa PG et al. 60% of Gram-negatives also showed resistance against fluoroquinolones & aminoglycosides in contrast to Spellberg et al.¹². So piperacillin-tazobactam along with clindamycin can be considered for empirical therapy which can be modified later based on culture findings.

46.7% of the Enterobacterales were found to be MDR. Most common MDR was K. pneumoniae (75%) & 50% of them were carbapenem resistance. Pseudomonas also showed carbapenem resistance of 16.7% in contrast to Mthethwa PG et al¹¹. We also observed quite a high number of morbidity in our study due to persistence of the MDR organisms (61.1%). Among the MDROs, MDR MRSA contributed (8/11) 72.7% whereas MDR GNBs not attributed much (27.3%). But we did not find any significant correlation (p=0.5) when we compared clinical outcomes between patients with and without MDR organisms.

21% of our patient had undergone amputation. Even, out of the 16 patient with an implant, 6 of them had implant failure (37.5%) within six months.