Repeat cultures in septic arthritis, do they change antibiotic management?

Abstract

Objectives: Septic arthritis is an orthopedic surgical emergency. Repeat cultures increase cost and patient discomfort; however, it is unknown whether repeat cultures have any merit in guiding treatment. The primary purpose of this investigation is to determine if repeat septic arthritis synovial fluid cultures alter antibiotic management. The secondary purpose is to identify independent risk factors that may alter subsequent antibiotic therapy. Methods: Septic arthritis cases were retrospectively reviewed using the International Classification of Diseases, Ninth Revision codes between January 2011 and December 2015. Inclusion criteria were patients >18 years with >1 positive synovial culture taken >2 days apart. Results: Two hundred and ninety-two synovial cultures were taken. Seventy were repeat cultures. Around 3 quarters (74.3%) yielded the same bacteria and 25.7% yielded different bacteria. Less than half (45.7%) of repeat cultures were associated with a change in antibiotics. Of the 18 repeat cultures that yielded different bacteria, six repeat cultures contained the same bacteria ± a different organism. Thirteen of the eighteen repeat cultures with different bacteria required a change in antibiotics. Patients who had their antibiotic therapy changed after repeat cultures were more likely to have diabetes mellitus (66.7% vs. 38.5%; P = 0.04, OR = 3.2 [1.04, 9.89]). Patients with hepatitis C more frequently required a different antibiotic regimen on repeat cultures (69.2% vs. 40.4%; P = 0.06, OR = 3.3 [0.91, 12.1]). Conclusion: Repeat culture data in patients with septic arthritis changed antibiotic regimens in 45.7% of patients and yielded different bacteria in 25.7%. Patients with diabetes more frequently required alternate antibiotic regimens.