1. Ubukata K, Asahi Y, Okuzumi K, Konno M, The Working Group for Penicillin-Resistant S. pneumoniae. Incidence of penicillin-resistant Streptococcus pneumoniae in Japan, 1993-1995. J Infect Chemother. 1996; 2: 177-184.
2. Ubukata K, Asahi Y, Yamane A, Konno M. Combinational detection of autolysin and penicillin-binding protein 2B genes of Streptococcus pneumoniae by PCR. J Clin Microbiol. 1996; 34: 592-596.
3. Yamane A, Nakano H, Asahi Y, Ubukata K, Konno M. Directly repeated insertion of 9-nucleotide sequence detected in penicillin-binding protein 2B gene of penicillin-resistant Streptococcus pneumoniae. Antimicrob Agents Chemother. 1996; 40: 1257-1259.
4. Ubukata K, Muraki T, Igarashi A, Asahi Y, Konno M, The Working Group for PRSP. In vitro evaluation of the activity of β-lactams, new quinolnes, and other antimicrobial agents against Streptococcus pneumoniae. J Infect Chemother. 1996; 2: 213-221.
5. Ubukata K, Muraki T, Igarashi A, Asahi Y, Konno M. Identification of penicillin and other beta-lactam resistance in Streptococcus pneumoniae by polymerase chain reaction. J Infect Chemother. 1997; 3: 190-197.
6. Asahi Y, Ubukata K. Association of a Thr-371 substitution in conserved amino acid motif of penicillin-binding protein 1A with penicillin resistance of Streptococcus pneumoniae. Antimicrob Agents Chemother.1998; 42: 2267-2273.
7. Asahi Y, Takeuchi Y, Ubukata K. Diversity of substitutions within or adjacent to conserved amino acid motifs of penicillin-binding protein 2X in cephalosporin-resistant Streptococcus pneumoniae isolates. Antimicrob Agents Chemother. 1999; 43: 1252-1255.
8. Nagai K, Shibasaki Y, Hasegawa K, Davis TA, Jacobs MR, Ubukata K, Appelbaum PC.  Evaluation of PCR primers to screen for Streptococcus pneumoniae isolates and beta-lactam resistance, and to detect common macrolide resistance determinants. J Antimicrob Chemother. 2001; 48: 915-918.
9. Ubukata K, Iwata S, Sunakawa K. In vitro activities of new ketolide, telithromycin, and eight other macrolide antibiotics against Streptococcus pneumoniae having mefA and ermB genes that mediate macrolide resistance. J Infect Chemoteher. 2003; 9: 221-226.  
10. Ubukata K, Chiba N, Hasegawa K, Kobayashi R, Iwata S, Sunakawa K. Anitbiotic susceptibility in relation to penicillin-binding protein genes and serotype distribution of Streptococcus pneumoniae strains responsible for meningitis in Japan, 1999-2002. Antimicrob Agents Chemother. 2004; 48: 1488-1494.
11. Maeda K, Ida T, Sanbongi Y, Suzuki T, Hukushima T, Kurazono M, Yonezawa M, Ubukata K, Inoue M. Comparison of activities of beta-lactam antibioitics against Streptococcus pneumoniae with recombinant penicillin-binding protein genes from a penicillin-resistant strain. J Infect Chemother. 2005; 11: 107-111.
12. Chiba N, Kobayashi R, Hasegawa K, Morozumi M, Nakayama E, Tajima T, Iwata S, Ubukata K. Antibiotic susceptibility according to genotype of penicillin-binding protein and macrolide resistance genes, and serotype of Streptococcus pneumoniae isolates from community-acquired pneumonia in children. J Antimicrob Chemother. 2005; 56: 756-760.
13. Kobayashi R, Konomi M, Hasegawa K, Morozumi M, Suzuki E, Sunakawa K, Ubukata K. In vitro activity of tebipenem, a new carbapenem antibiotic, against penicillin-nonsusceptible Streptococcus pneumoniae. Antimicrob Agents Chemother. 2005; 49: 889-894. 
14. Chiba N, Morozumi M, Sunaoshi K, Takahashi S, Takano M, Komori T, Sunakawa K, Ubukata K, IPD Surveillance Study Group. Serotype and antibiotic resistance of isolates from patients with invasive pneumococcal disease in Japan. Epidemiol Infect. 2010; 138: 61-68.
15. Sakai F, Chiba N, Ono A, Murayama SY, Ubukata K, Sunakawa K, Takahashi T. Molecular epidemiologic characteristics of Streptococcus pneumoniae isolates from children with meningitis in Japan from 2007 through 2009. J Infect Chemother. 2011; 17: 334-340.
16. Rakov AV, Ubukata K, Robinson DA. Population structure of hyperinvasive serotype 12F, clonal complex 218 Streptococcus pneumoniae revealed by multilocus boxB sequence typing. Infect Genet Evol. 2011; 11: 1929-1939.
17. Chiba N, Morozumi M, Ubukata K. Application of the Real-Time PCR Method for Genotypic Identification of β-Lactam Resistance in Isolates from Invasive Pneumococcal Diseases. Microb Drug Resist. 2012; 18: 149-156.
18. Chiba N, Morozumi M, Shouji M, Wajima T, Iwata S, Ubukata K, the Invasive Pneumococcal Diseases Surveillance Study Group. Marked changes of capsular type and genetic antimicrobial resistance in isolates from children under 18 years old with invasive pneumococcal diseases in Japan after introduction of 7-valent conjugate vaccine. Emerg Infect Dis. 2014;20:1132-1139.
19. Ubukata K, Chiba N, Hanada S, Morozumi M, Wajima T, Shouji M. Iwata S, IPD Surveillance Study Group. Serotype changes and drug resistance in invasive pneumococcal diseases in adults after vaccinations in children, Japan, 2010-2013. Emerg Infect Dis. 2015;21:1956-1965.
20. Hanada S, Iwata S, Kishi K, Morozumi M, Chiba N, Wajima T, Takata M, Ubukata K. Host factors and biomarkers associated with poor outcomes in adults with invasive pneumococcal disease. PLoS One. 2016;11: e0147877.
21. Nishikawa-Nakamura N, Okada T, Nishimura K, Iwai T, Ubukata K, Iwata S, Iwai A. An infant with concurrent serotype 6C invasive pneumococcal disease and infectious mononucleosis. J Infect Chemother. 2017; 23:785-787.
22. Chiba N, Murayama SY, Morozumi M, Iwata S, Ubukata K. Genome evolution to penicillin resistance in serotype 3 Streptococcus pneumoniae by capsular switching. Antimicrob Agents Chemother. 2017; 61:e00478-17.
23. Ubukata K, Morozumi M, Sakuma M, Takata M, Mokuno E, Tajima T, Iwata S; and the AOM Surveillance Study Group. Etiology of acute otitis media and characterization of pneumococcal isolates after introduction of 13-valent pneumococcal conjugate vaccine in Japanese children. Pediatr Infect Dis J. 2018;37:598-604.
24. Ubukata K, Takata M, Morozumi M, Chiba N, Wajima T, Hanada S, Shouji M, Sakuma M, Iwata S. Effects of pneumococcal conjugate vaccine on genotypic penicillin resistance and serotype changes, Japan, 2010-2017. Emerg Infect Dis. 2018; 24:2010-2020.

Review

Ubukata K. Problems associated with high prevalence of multidrug-resistant bacteria in patients with community-acquired infections. J Infect Chemother. 2003; 9: 285-291.