We determined MICs of antibacterial agents against 2,562 clinical strains of aerobic Gramnegative bacteria(18 genus or species)isolated at 17 facilities across Japan in 2010 and 2012.

The ratio of strains producing extended-spectrum β-lactamases (ESBL) had a trend to increase until 2012. The prevalence of ESBL-producing Escherichia coli increased from 10.3% of all isolated E. coli in 2010 to 22.5% in 2012, which was significant increase from 3.8% in 2008 reported on our previous surveillance. The prevalence of ESBL-producing Klebsiella pneumoniae increased slightly from 3.7% in 2010 to 4.6% in 2012. Although the prevalence of ESBL-producing Klebsiella oxytoca decreased from 12.1% in 2010 to 9.6% in 2012, our previous surveillance revealed the gradual increase of the ratio of ESBL-producing K. oxytoca from 3.2% in 2006 to 12.1% in 2010. With these increase of ESBL-producer, the MIC₉₀s of ceftazidime and cefepime against E. coli showed significant increase from 2μg/mL and 8μg/mL in 2010 to 32μg/mL and 64μg/mL in 2012, respectively. On the other hand, the MIC₉₀s of flomoxef and cefmetazole against E. coli were maintained as similar level between 2010 and 2012.

Against glucose-non-fermentative Gram-negative bacteria, the activities of most antibacterial agents were similar to those against the isolates in 2008.

The ratio of multidrug-resistant Pseudomonas aeruginosa increased from 1.1% in 2008 to 5.8% in 2010, however, it decreased to 2.4% in 2012. The multidrug-resistant Acinetobacter were 3.2% and 0% from all isolated Acinetobacter spp. in 2010 and in 2012, respectively.

In Japan, the high incidence of aseptic meningitis associated with a mumps vaccine strain led to the discontinuation of measles-mumps-rubella vaccine administration in 1993, interrupting routine mumps immunization. Voluntary immunization with monovalent mumps vaccines later resumed, and many Japanese pediatricians claim that the incidence of aseptic meningitis following immunization with monovalent mumps vaccines (“postvaccinal aseptic meningitis incidence”) has decreased. However, there are no reports verifying this contention. To investigate changes in the annual postvaccinal aseptic meningitis incidence, we assessed the annual incidence of aseptic meningitis following vaccination with Torii strain from 2004 to 2015. Our incidence estimates are based on the number of spontaneous reports regarding suspected cases of adverse reactions due to Torii strain-derived mumps vaccine and the number of vaccine shipments from Takeda Pharmaceutical Company Limited. During this period, there were a total of 4,610,080 vaccine shipments and 127 suspected cases of aseptic meningitis, yielding a mean annual postvaccinal aseptic meningitis incidence of 2.8 ± 1.0 cases/100,000 doses (lowest annual incidence: 1.3 cases/100,000 doses [2005]; highest annual incidence: 4.4 cases/100,000 doses [2007]). The annual incidence did not change significantly between 2004 and 2015. The cause for the possible decrease in comparison with incidence around 1990 requires further investigation.