Value of Acid-Fast Bacilli and Fungal Cultures in Foot and Ankle Surgery in a US Hospital System.

Background: Acid-fast bacilli(AFB) and fungi are generally slow-growing, difficult to culture, and rarely the cause of infection. The goal of this study was to evaluate the value of routinely obtaining AFB and fungal cultures in foot and ankle surgery at a US hospital.

Methods: A retrospective review was conducted to determine the number of positive AFB and fungal cultures out of the total number of foot and ankle samples tested. Between 2014 and 2019, patients who underwent surgery for a foot and ankle infection for soft tissue infection, septic arthritis, infectious postoperative complications were identified. Charts were reviewed to identify the results of the microbiological tests performed. To determine the value of running AFB and fungal cultures, the costs of each were provided by the microbiology lab at our institution.

Results: Of the 322 patient charts reviewed, there were 434 AFB and 525 fungal cultures performed. None of these cultures were indicated to be positive for AFB (0%), and 22 (4.19%) were positive for fungi. The total labor and material costs were calculated to be $38 767. The AFB cultures cost $23 967, the positive fungal cultures cost $2371, and the negative fungal cultures cost $36 395.36.

Conclusion: This 322-case series of surgically managed foot and ankle infections showed 0% and 4.1% positivity rates of AFB and fungal cultures, respectively. Additionally, only 20% of cases with positive cultures were identified as pathologic requiring antifungal treatment. Further analysis is needed to determine best practices for obtaining vs declining to culture for AFB or fungal species, including assessing patient outcomes in the series of culture-positive(fungal-only) cases. Our results suggest that in our clinical setting of a US hospital system, routine fungal and AFB cultures may not be necessary but should be considered for chronic/recalcitrant infections, immunocompromised patients, and those with high surgeon suspicion.

Level Of Evidence: Level IV, case series.