SSIs are an important cause of hospital mortality, prolonging hospital stays, increasing antibiotic usage, and markedly increasing the financial burden of medical care [[1], [2], [3], [4]]; Therefore, SSIs are a key target for nosocomial infection control programs. A prevalence survey by the JHAIS program showed that 6.37 % of patients developed SSI after surgery, and the leading causative organism was Enterococcus faecalis, followed by Pseudomonas aeruginosa, Staphylococcus aureus, Enterobacter cloacae, and Escherichia coli [5]. Inappropriate antimicrobial therapy for SSIs causes poor clinical outcomes and increases the risk of the development of antibiotic-resistant organisms.

Nationwide surveys were conducted in Japan in 2010, 2014–2015, and 2018–2019 to investigate the antimicrobial susceptibility of pathogens isolated from SSIs [[6], [7], [8]]. Although the rate of detection of ESBL-producing strains of E. coli increased from 9.5 % in 2010 to 23 % in 2014–2015, the incidence decreased to 8.7 % in 2018–2019. Although high rates of susceptibility to TAZ/PIPC were detected, the geometric mean MICs were substantially higher than that to MEPM (2.67 vs 0.08 μg/mL). In contrast, relatively low geometric mean MICs (0.397 μg/mL) were observed for TAZ/CTLZ. Although the MRSA incidence rate decreased from 72 % in the first surveillance to 53 % in the second, no further decrease was detected in 2018–2019. For Bacteroides species, low levels of susceptibility were observed for MFLX (65.3 %), CFX (65.3 %), and CLDM (38.9 %). Low susceptibility to cefoxitin was demonstrated in non-fragilis Bacteroides, especially B. thetaiotaomicron. However, low susceptibility rates to CLDM were demonstrated in both B. fragilis and non-fragilis Bacteroides species, and a steady decrease in susceptibility was observed in all surveys (59.3 % in 2010, 46.9 % in 2014–2015, and 38.9 % in 2018–2019). These results indicate the need for continuous monitoring of these isolates. The purpose of the current study was to investigate changes in antimicrobial susceptibility and the prevalence of antimicrobial-resistant organisms compared to earlier studies.