![[ Visit Client Website ]](images/banner.gif)
Objectives: We previously reported a significant decline in susceptibility to Proteus species for several antibiotics, including ceftriaxone. Since the phenotypic susceptibility pattern from the automated system appeared to resemble an ESBL isolate, we performed susceptibility testing for several antimicrobials using E-test. Surprisingly, none of the isolates produced an extended-spectrum beta-lactamase. Furthermore, all of the isolates were susceptible to ceftriaxone with all MICs being < 1 mcg/mL. Upon further investigation, it was discovered that the algorithm selected in the automated system led to classifying ceftriaxone and other beta-lactams as resistant. Building on previously reported data, this study will evaluate a yearly antibiogram for 7 antibiotics against Proteus species and determine the economic impact of resistant isolates.
Methods: All susceptibility data for Proteus cultures from 2006-2011 were obtained and duplicate isolates removed to create a yearly antibiogram for ampicillin, amoxicillin/clavulanate, cefazolin, ceftriaxone, gentamicin, ciprofloxacin or levofloxacin, and trimethoprim/sulfamethaxozole. Patient information collected from the health system's electronic medical records included: admission and discharge dates, age, prescriber, culture site, hospital location, and antibiotic therapy (prior to and after culture results). Length of hospital stay and antibiotic therapy cost will be calculated for each patient. Multi-drug resistance (MDR) was defined as resistant to ceftriaxone plus 2 other antibiotic classes.
Results: Overall, 1371 patients were identified of which 300 isolates were considered MDR. All antibiotics evaluated except ceftriaxone demonstrated a relative stable susceptibility pattern over the time period. Ceftriaxone susceptibility was 96% (2006), 85% (2007), 59% (2008), 64% (2009), 86% (2010), and 89% (2011). Amoxicillin/clavulanate displayed the highest percent susceptible (96%).
Conclusion: Selection of some algorithms in automatic susceptibility testing can lead to inappropriate susceptibility reporting and potential increased cost of therapy. The overall economic impact (i.e., cost of antibiotic therapy, hospital stay) of MDR Proteus infections will be presented.