Microorganisms Associated With Osteomyelitis of the Foot and Ankle.

Osteomyelitis of the foot and ankle is a challenge to treat and creates a significant demand on both the patient and the healthcare system. The purposes of this study were to determine the microorganisms associated with foot and ankle osteomyelitis, to evaluate the change in methicillin-resistant Staphylococcus aureus (MRSA) between 2005 and 2010, and to determine the relationship between these infecting organisms and patient comorbidities. The medical records for 302 patients diagnosed with osteomyelitis of the foot and ankle, 151 in 2005 and 151 in 2010, were randomly selected and evaluated. The authors reviewed the demographics, comorbidities, microorganism(s) confirmed with bone biopsy and culture, location, and use of antibiotics before bone biopsy. Gram-positive bacteria were the most prevalent, composing 81.9% of the isolates in 2005 and 59.6% in 2010. Methicillin-sensitive Staphylococcus aureus was the most common in both cohorts. Conversely, the incidence of MRSA statistically decreased from 28.3% to 10.6% from 2005 to 2010 (p < .0001). Gram-negative bacteria were found in 39.5% of the 2005 isolates and 31.8% of those from 2010. Pseudomonas sp. was the most common gram-negative bacteria. Patients with peripheral vascular disease had a significantly higher incidence of gram-negative bacteria (odds ratio 2.1, 95% confidence interval, 1.3 to 3.6, p = .003). The results of this study reveal that MSSA was the most common bacteria, incidence of MRSA decreased between the 2005 to 2010, and patients with peripheral vascular disease have a significantly higher incidence of gram-negative bacteria.