Estimating the disease burden of methicillin-resistant Staphylococcus aureus in Japan: Retrospective database study of Japanese hospitals

OBJECTIVES: The nationwide impact of antimicrobial-resistant infections on healthcare facilities throughout Japan has yet to be examined. This study aimed to estimate the disease burden of methicillin-resistant Staphylococcus aureus (MRSA) infections in Japanese hospitals. DESIGN: Retrospective analysis of inpatients comparing outcomes between subjects with and without MRSA infection. DATA SOURCE: A nationwide administrative claims database. SETTING: 1133 acute care hospitals throughout Japan. PARTICIPANTS: All surgical and non-surgical inpatients who were discharged between April 1, 2014 and March 31, 2015. MAIN OUTCOME MEASURES: Disease burden was assessed using hospitalization costs, length of stay, and in-hospital mortality. Using a unique method of infection identification, we categorized patients into an anti-MRSA drug group and a control group based on anti-MRSA drug utilization. To estimate the burden of MRSA infections, we calculated the differences in outcome measures between these two groups. The estimates were extrapolated to all 1584 acute care hospitals in Japan that have adopted a prospective payment system. RESULTS: We categorized 93 838 patients into the anti-MRSA drug group and 2 181 827 patients into the control group. The mean hospitalization costs, length of stay, and in-hospital mortality of the anti-MRSA drug group were US$33 548, 75.7 days, and 22.9%, respectively; these values were 3.43, 2.95, and 3.66 times that of the control group, respectively. When extrapolated to the 1584 hospitals, the total incremental burden of MRSA was estimated to be US$2 billion (3.41% of total hospitalization costs), 4.34 million days (3.02% of total length of stay), and 14.3 thousand deaths (3.62% of total mortality). CONCLUSIONS: This study quantified the approximate disease burden of MRSA infections in Japan. These findings can inform policymakers on the burden of antimicrobial-resistant infections and support the application of infection prevention programs.