Epidemics of drug-resistant bacterial infections observed in infectious disease surveillance in Japan, 2001-2005

Background: Drug-resistant bacteria have been increasing together with advancement of antimicrobial chemotherapy in recent years. In Japan, the target diseases in the National Epidemiological Surveillance of Infectious Diseases (NESID) include some drug-resistant bacterial infections. Methods: We used the data in the NESID in Japan, 2001-2005. Target diseases were methicillin-resistant Staphylocoocus aureus (MRSA), penicillin-resistant Streptocoocus pneumoniae (PRSP) and multi-drug-resistant Pseudomonas aeruginosa (MDRPA) infections. The numbers of patients reported by sentinel hospitals (about 500) on a monthly basis were observed. Results: The numbers of patients per month per sentinel hospital of 2001-2005 were 3.37-3.98 in MRSA, 6.96-1.19 in PRSP, and 0.11-0.13 in MDRPA infections. The sex ratios (male/female) of patients were 1.69-l.82, 1.34-1.43, and 1.71-2.52, respectively. More than 50% of all patients were adults aged 70 years or older in MRSA and MDRPA infections, but more than 60% were children under 10 years in PRSP infections. The number of patients per sentinel hospital in MRSA infections showed little variation between months but evidenced a large variation in PRSP and MDRPA infections. The annual trend in the number of patients per sentinel hospital was increasing significantly for the 5-year period in MRSA and PRSP infections, but not in MDRPA infections. Conclusions: We revealed sex-age distributions of the patients reported to NESID in Japan, 2001-2005. An increasing incidence of MRSA and PRSP infections and monthly variation in PRSP and MDRPA infections were observed for the 5-year period. Extended observation would be necessary to confirm these trends and variations.