How Common is MRSA in Adult Septic Arthritis?

From the Department of Emergency Medicine, Alameda County Medical Center–Highland Campus, Oakland, CA (Frazee, Lambert); and the Department of Emergency Medicine, University of California San Francisco, San Francisco, CA (Frazee, Fee).

INTRODUCTION

Background

Acute monoarticular arthritis is a common problem in emergency medicine. Among the leading causes, septic arthritis is the most important emergency to identify because it leads to rapid cartilage destruction and is associated with significant inhospital mortality. Because the clinical examination is unreliable to rule out septic arthritis, emergency physicians must maintain a very low threshold for performing diagnostic arthrocentesis. The level of synovial fluid leukocytosis generally correlates with likelihood of bacterial infection; however, a low cell count does not rule out the diagnosis. Synovial fluid culture is considered the criterion standard test to establish the diagnosis. The decision whether to admit and begin empiric antibiotics while awaiting culture results often must be based on the overall clinical picture, including age, comorbidities, and presence of fever, as well as synovial fluid leukocyte count, crystals, and Gram’s stain. The choice of empiric antibiotics isdictated by the susceptibility patterns of the most likely pathogens.

Although Staphylococcus aureus is the predominant causal pathogen in septic arthritis, the current prevalence of methicillin-resistant S aureus (MRSA) in this infection type is not clear. Community-associated MRSA is now the predominant cause of skin and soft tissue infections in US emergency departments (EDs), and MRSA is an increasingly common cause of invasive infections of all types, both community and hospital acquired. At the public hospital in this study, 41% of all clinical S aureus isolates in 2007 were MRSA.

Importance

We sought to evaluate the current cause of septic arthritis in a predominantly adult ED population. We hypothesized that MRSA would account for a significant proportion of recent cases. If so, antibiotics with activity against MRSA should be included in the empirical treatment of septic arthritis.

Goals of This Investigation

The primary goal of this study was to determine the proportion of ED patients with septic arthritis caused by MRSA. The secondary goal was to describe clinical features of adult MRSA septic arthritis case patients … read the full PDF article

Source: Annals of Emergency Medicine

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