From October 2006 to September 2007, we collected the specimen from 356 patients with lower
respiratory tract infections in 14 institutions in Japan, and investigated the susceptibilities of isolated bacteria to various
antibacterial agents and patients' characteristics. Of 414 strains that were isolated from specimen (mainly from sputum) and assumed to be bacteria causing in
infection, 407 strains were examined. The isolated bacteria were: Staphylococcus aureus 64, Streptococcus pneumoniae 96, Haemophilus influenzae 87, Pseudomonas aeruginosa (non-mucoid) 52, P. aeruginosa (mucoid) 11, Klebsiella pneumoniae 20, and Moraxella catarrhalis 44. Of 64 S. aureus strains, those with 2 microg/ml or less of MIC of
oxacillin (
methicillin-susceptible S. aureus: MSSA) and those with 4 microg/ml or more of MIC of
oxacillin (methicillin-resistant S. aureus: MRSA) were 27 (42.2%) and 37 (57.8%) strains, respectively. Against MSSA,
imipenem had the most potent antibacterial activity and inhibited the growth of all strains at 0.063 microg/ml or less. Against MRSA,
vancomycin and
linezolid showed the most potent activity and inhibited the growth of all the strains at 1 microg/ml.
Carbapenems showed the most potent activities against S. pneumoniae and in particular,
panipenem inhibited the growth of all the strains at 0.063 microg/ml or less.
Imipenem and
faropenem also had a preferable activity and inhibited the growth of all the strains at 0.125 and 0.5 microg/ml, respectively. In contrast, there were high-resistant strains (MIC: over 128 microg/ml) for
erythromycin (45.8%) and
clindamycin (20.8%). Against H. influenzae,
levofloxacin showed the most potent activity and its MIC90 was 0.063 microg/ml or less.
Meropenem showed the most potent activity against P. aeruginosa (mucoid) and its MIC90 was 0.5 microg/ml. Against P. aeruginosa (non-mucoid),
tobramycin had the most potent activity and its MIC90 was 2 microg/ml. Against K. pneumoniae,
cefozopran was the most potent activity and inhibited the growth of all the strains at 0.063 microg/ml or less. Also, all the
antibacterial agents except
ampicillin generally showed a potent activity against M. catarrhalis and the MIC90 of them were 2 microg/ml or less. The approximately half the number (50.6%) of the patients with respiratory
infection were aged 70 years or older.
Bacterial pneumonia and
chronic bronchitis accounted for 49.2% and 28.1% of all the
respiratory infections, respectively. The bacteria frequently isolated from the patients with
bacterial pneumonia were S. pneumoniae (29.2%), S. aureus (20.8%), and H. influenzae (12.9%). H. influenzae (25.0%) and P. aeruginosa (21.7%) also were frequently isolated from the patients with
chronic bronchitis. Before the
antibacterial agent administration, the bacteria frequently isolated from the patients were S. pneumoniae (27.5%) and H. influenzae (22.5%). The bacteria frequently isolated from the patients treated with
macrolides was P. aeruginosa, and its isolation frequently was 39.4%.