A total of 685 clinical Streptococcus pneumoniae isolates from patients with pneumococcal diseases were collected from 14 centers in 11 Asian countries from January 2000 to June 2001. The in vitro susceptibilities of the isolates to 14 antimicrobial agents were determined by the broth microdilution test. Among the isolates tested, 483 (52.4%) were not susceptible to penicillin, 23% were intermediate, and 29.4% were penicillin resistant (MICs ≥ 2 mg/liter). Isolates from Vietnam showed the highest prevalence of penicillin resistance (71.4%), followed by those from Korea (54.8%), Hong Kong (43.2%), and Taiwan (38.6%). The penicillin MICs at which 90% of isolates are inhibited (MIC ₉₀ s) were 4 mg/liter among isolates from Vietnam, Hong Kong, Korea, and Taiwan. The prevalence of erythromycin resistance was also very high in Vietnam (92.1%), Taiwan (86%), Korea (80.6%), Hong Kong (76.8%), and China (73.9%). The MIC ₉₀ s of erythromycin were >32 mg/liter among isolates from Korea, Vietnam, China, Taiwan, Singapore, Malaysia, and Hong Kong. Isolates from Hong Kong showed the highest rate of ciprofloxacin resistance (11.8%), followed by isolates from Sri Lanka (9.5%), the Philippines (9.1%), and Korea (6.5%). Multilocus sequence typing showed that the spread of the Taiwan ^19F clone and the Spain ^23F clone could be one of the major reasons for the rapid increases in antimicrobial resistance among S. pneumoniae isolates in Asia. Data from the multinational surveillance study clearly documented distinctive increases in the prevalence rates and the levels of antimicrobial resistance among S. pneumoniae isolates in many Asian countries, which are among the highest in the world published to date.

To find potential targets of novel antimicrobial agents, we identified essential genes of Streptococcus pneumoniae using comparative genomics and allelic replacement mutagenesis. We compared the genome of S. pneumoniae R6 with those of Bacillus subtilis, Enterococcus faecalis, Escherichia coli, and Staphylococcus aureus, and selected 693 candidate target genes with > 40% amino acid sequence identity to the corresponding genes in at least two of the other species. The 693 genes were disrupted and 133 were found to be essential for growth. Of these, 32 encoded proteins of unknown function, and we were able to identify orthologues of 22 of these genes by genomic comparisons. The experimental method used in this study is easy to perform, rapid and efficient for identifying essential genes of bacterial pathogens.

To investigate the evolutionary pattern and genotypic characteristics of methicillin-resistant Staphylococcus aureus (MRSA) strains in the Asian region, 74 MRSA strains isolated from 12 Asian countries were analyzed by multilocus sequence typing (MLST) and SCC mec typing. Overall, a total of 16 genotypes based on sequence type and SCC mec types were identified among MRSA strains from Asian countries. Data revealed two major genotypes of MRSA strains in Asia, with unique geographic distributions. By MLST analysis, all strains from Korea and Japan except one belonged to clonal complex 5 (CC5) while most MRSA isolates from other Asian countries belonged to CC239. SCC mec typing showed that most isolates from Korea and Japan were SS mec type II whereas SCC mec type III (or IIIA) was the most common type in strains from other Asian countries. Our data documented a unique geographic distribution and evolutionary pattern of MRSA clones in Asia.

To investigate the impact of imipenem resistance on the mortality rate among patients with Acinetobacter bacteraemia. A retrospective, pairwise-matched (1:1), risk-adjusted (age, Pitt bacteraemia score) cohort study was performed at three tertiary care hospitals in Korea from January 2000 to June 2005. Forty patients with imipenem non-susceptible Acinetobacter bacteraemia (INAB group) and 40 matched subjects (1:1 ratio) with imipenem-susceptible Acinetobacter bacteraemia (ISAB group) were included. Both groups had similar clinical features related to the severity of illness. The 30 day mortality rate was higher in the INAB group (57.5%) than the ISAB group (27.5%) (P = 0.007). The rate of discordant antimicrobial therapy was higher in the INAB group (65.0%) than the ISAB group (20.0%) (P < 0.001). The 30 day mortality rate was higher in the patients with discordant antimicrobial therapy (67.6%) than concordant antimicrobial therapy (23.9%) (P < 0.001). Multivariate analysis showed that age, the Pitt bacteraemia score, immunosuppressive status, and discordant antimicrobial therapy were independent risk factors for 30 day mortality among patients with Acinetobacter bacteraemia (P < 0.05). When discordant antimicrobial therapy was excluded in the multivariate analysis, the imipenem resistance was associated with 30 day mortality (P = 0.005). Imipenem resistance has a significant impact on the mortality rate among patients with Acinetobacter bacteraemia, and this is mainly attributable to the higher rate of discordant antimicrobial therapy.

Severe fever with thrombocytopenia syndrome (SFTS) is a tick-borne viral disease. The SFTS virus (SFTSV) has been detected in the Haemaphysalis longicornis, which acts as a transmission host between animals and humans. SFTSV was first confirmed in China in 2009 and has also been circulating in Japan and South Korea. However, it is not known if a genetic connection exists between the viruses in these regions and, if so, how SFTSV is transmitted across China, South Korea, and Japan. We therefore hypothesize that the SFTSV in South Korea share common phylogenetic origins with samples from China and Japan. Further, we postulate that migratory birds, well-known carriers of the tick H. longicornis, are a potential source of SFTSV transmission across countries. Our phylogenetic analysis results show that the SFTSV isolates in South Korea were similar to isolates from Japan and China. We connect this with previous work showing that SFTSV-infected H. longicornis were found in China, South Korea, and Japan. In addition, H. longicornis were found on migratory birds. The migratory bird routes and the distribution of H. longicornis are concurrent with the occurrence of SFTSV. Therefore, we suggest that migratory birds play an important role in dispersing H. longicornis-borne SFTSV.