title: In vitro activity of tebipenem, a new oral carbapenem antibiotic, against penicillin-nonsusceptible Streptococcus pneumoniae.
abstract: The in vitro activity of tebipenem (TBM), a new oral carbapenem antibiotic, against Streptococcus pneumoniae clinical isolates (n = 202) was compared with those of 15 reference agents. The isolates were classified into five genotypic classes after PCR identification of abnormal pbp1a, pbp2x, and pbp2b genes: (i) penicillin-susceptible S. pneumoniae (PSSP) isolates with no abnormal pbp genes (n = 34; 16.8%), (ii) genotypic penicillin-intermediate S. pneumoniae (gPISP) isolates with only an abnormal pbp2x gene [gPISP (2x)] (n = 48; 23.8%), (iii) gPISP isolates with abnormal pbp1a and pbp2x genes (n = 32; 15.8%), (iv) gPISP isolates with abnormal pbp2x and pbp2b genes (n = 16; 7.9%), and (v) genotypic penicillin-resistant S. pneumoniae (gPRSP) isolates with three abnormal pbp genes (n = 72; 35.6%). The majority of the strains tested had mefA (n = 59; 29.2%) or ermB (n = 91; 45%) gene-mediating macrolide resistance. For these isolates the MIC at which 90% of isolates are inhibited was significantly lower for TBM than for the reference oral antibiotics, as follows: 0.002 microg/ml for PSSP, 0.004 mug/ml for gPISP (2x), 0.016 microg/ml for gPISP (isolates with abnormal pbp1a and pbp2x genes and isolates with abnormal pbp2x and pbp2b genes), and 0.063 microg/ml for gPRSP. In addition, TBM showed excellent bactericidal activity against gPRSP isolates, which exhibited a 3-log(10) decrease within 2 h when they were incubated with a concentration greater than or equal to the MIC. Inhibition of cell wall synthesis toward the long axis and subsequent cell lysis were observed by scanning electron microscopy after a short-term exposure to TBM, unlike the effects seen with cephalosporins. These data suggest that TBM has potent activity against multidrug-resistant S. pneumoniae, the causative pathogen of community-acquired respiratory tract infections.
authors.affiliation: Laboratory of Infectious Agents Surveillance, Kitasato Institute for Life Sciences and Graduate School of Infection Control Sciences, Kitasato University, Shirokane, Minato-ku, 108-8641 Tokyo, Japan.
authors.forename: Reiko
authors.initials: R
authors.lastname: Kobayashi
authors.forename: Mami
authors.initials: M
authors.lastname: Konomi
authors.forename: Keiko
authors.initials: K
authors.lastname: Hasegawa
authors.forename: Miyuki
authors.initials: M
authors.lastname: Morozumi
authors.forename: Keisuke
authors.initials: K
authors.lastname: Sunakawa
authors.forename: Kimiko
authors.initials: K
authors.lastname: Ubukata
mesh_terms: D000284:Administration, Oral; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D015780:Carbapenems / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D010403:Penicillin Resistance; D013296:Streptococcus pneumoniae / Q000187:drug effects*
chemical_list: D000900:Anti-Bacterial Agents; D015780:Carbapenems; C500135:tebipenem
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