Erik Munson, PhD; Erin Hueppchen; Heather Zeman
Background: Antimicrobial resistance merits surveillance because of its impact on quality health care. Past surveillance efforts in Wisconsin involved generation of a statewide antibiogram on the basis of antibiogram compilation. However, this modality of surveillance possesses limitations.
Methods: To characterize Wisconsin antimicrobial susceptibility patterns and elucidate geographic variation in antimicrobial resistance, a statewide surveillance network was created. Clinical microbiology laboratories submitted clinically significant bacterial isolates to a centralized testing facility for performance of standardized broth microdilution testing. Analyzed data included organism-specific susceptible, intermediate, and resistant percentages, along with median and 90th percentile minimum inhibitory concentration values.
Results: In comparison of 378 isolates of Escherichia coli (E coli) and 279 isolates of Proteus mirabilis (P mirabilis), susceptibility rates of E coli were generally lower than P mirabilis, particularly in areas of Wisconsin bordering Lake Winnebago. P mirabilis resistance rates were generally higher in northern Wisconsin. From a 211-isolate collection of Pseudomonas aeruginosa, it was determined that higher rates of antimicrobial resistance were found in Southeast Wisconsin. On a geographic basis, susceptibility rates within a 212-isolate collection of Streptococcus pneumoniae were fairly consistent. However, Southcentral Wisconsin experienced increased rates of erythromycin resistance with this organism, as well as increased aminoglycoside resistance trending with other organisms. Antimicrobial agents with generally lower susceptibility rates statewide included fluoroquinolones and trimethoprim-sulfamethoxazole.
Conclusions: A surveillance program has been initiated in Wisconsin that not only summarizes susceptibility patterns but also has the capacity to indicate potential emerging resistance trends. Future annual studies can begin to characterize antimicrobial resistance in Wisconsin on a temporal basis.