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Theme: Inclusion and Collaboration Theme: Inclusion and Collaboration

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Building an Empiric Antibiotic Algorithm as a Function of Patient and Infection Factors: A Prospective, High-Powered Analysis of the Pathogenic Microbiology of Surgical Hand and Forearm Infections
Ketan Sharma, MD, MPH1; Aaron Mull, MD2; James Friedman, MD3; Deng Pan, BS2; Jennifer Yu, MD1; Ida Fox, MD4; Moore M Amy, MD5; (1)Washington University in St Louis, St Louis, MO, (2)Washington University St Louis, St Louis, MO, (3)University of Pennyslvania, Philadelphia, PA, (4)Washington University St. Louis, St Louis, MO, (5)Department of Surgery, Division of Plastic and Reconstructive Surgery, Washington University School of Medicine, Saint Louis, MO

Introduction

Existing evidence concerning the pathogenic microbiology of hand and forearm infections is limited to retrospective case series in specific patient populations. A high-powered, prospective, inclusive analysis can lead to an improved epidemiologic understanding of the pathogenic microbiology, determine if the distribution of causative micro-organisms varies meaningfully by patient or infection factors, and build an empiric antibiotic algorithm that decreases the risks of unnecessarily-broad initial antibiotic coverage and accelerates functional recovery.

Materials and Methods

A prospective cohort study was created of all patients with surgical infections of the hand and forearm evaluated at a single institution over a three year period. Patient and infection factors were recorded. Patient variables included age, smoking, history of intravenous drug use (IVDU), diabetes, and previous history of hand infection. Infection factors included mechanism, location, and type. Culture results from first drainage were tabulated and were grouped as methicillin-sensitive Staph. Aureus (MSSA), methicillin-resistant Staph. Aureus (MRSA), non-Staph Gram-positives (NSGP), Gram-negatives (GN), and fungal (F).

Results

388 patients were accrued. Average age was 42 years, with 67% male, 52% active smokers, 26% with history of intravenous drug use (IVDU), and 19% with a previous history of a hand infection. The most common mechanisms were: idiopathic 29%, other trauma 27%, IVDU 20%, and animal bite 11%.

Amongst all cultures, the prevalence of MSSA was 22%, MRSA 22%, NSGP 32%, GN 14%, and F 3%.

Patients with a previous history of hand infection were less likely to grow MSSA and more likely to grow NSGP (p=0.048). Patients with diabetes were more likely to grow F (p<0.01). Patients with a history of IVDU were more likely to grow NSGP (p<0.01). Infections resulting from animal bites were more likely to grow GNs, while mechanisms due to other trauma were less likely to grow MSSA (p<0.01). Infections in the digits or thumb were more likely to grow MSSA (p<0.01). Lastly, paronychias were more likely to grow MSSA (p<0.01), while felons were more likely to grow MRSA (p<0.01).

Conclusion

In this high-powered, prospective study, there are several clinically-significant differences in the distribution of pathogenic microbiology of surgical hand and forearm infections by patient factors and infection mechanism, location, and type. These results can be coupled with sensitivity data to build an empiric antibiotic algorithm as a function of patient and infection factors to optimize initial antibiotic therapy prior to culture results.


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