Volume VII, Number 1 | April 2023

The Utility of AFB and Fungal Cultures in Orthopedic Infections

Sanderford J, Krumrey J, Pipitone O
Good Samaritan Regional Medical Center, Corvallis, Oregon, United States

INTRODUCTION: When diagnosing suspected osteomyelitis fungal and acid-fast bacilli (AFB) cultures are often obtained intraoperatively. These cultures are difficult and time consuming to grow and increase health care costs. This study aimed to quantify the rate of positive AFB and fungal cultures in orthopedic infections and to compare potential risk factors for a positive result.

METHODS: Orthopedic surgical cases for suspected infection at one institution from March 2013 through December 2019 were included. Data was collected on patient demographics and procedure characteristics for patients with surgical AFB or fungal lab tests ordered. The percent of positive AFB and fungal cultures were calculated. Patients with a positive versus negative fungal culture result were compared. The crude and adjusted odds of a positive culture result by peripheral vascular disease (PVD) status and operating region were estimated.

RESULTS: Of the 813 patients for whom intraoperative AFB or fungal cultures were ordered, 3.8% (31/813) had a positive result. Of these 31 patients with a positive result, only one patient with a known history of AFB infection had a positive AFB culture result, leaving 3.7% (30/813) with a positive fungal culture. Patients with a positive versus negative fungal culture result did not differ significantly by age, sex, ASA score, diabetes, obesity, or HIV/AIDS. In both crude and adjusted analyses, PVD was associated with higher odds of a positive fungal culture result (Adjusted OR=3.6, 95% CI=1.4-8.7). Likewise, in both crude and adjusted models, a hand/foot operating region was associated with higher odds of a positive fungal culture result compared with all other regions (Adjusted OR=4.7, 95% CI=2.1-11.5).

CONCLUSION: Intraoperative fungal cultures may only be useful in hand or foot infections and patients with PVD. AFB cultures may not be warranted in any patient without a history of mycobacterial infection.

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The Journal of the American Osteopathic Academy of Orthopedics

Steven J. Heithoff, DO, FAOAO

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