From October 2009 to September 2010, we collected the specimen from 432 patients with lower
respiratory tract infections in 16 institutions in Japan, and investigated the susceptibilities of isolated bacteria to various
antibacterial agents and patients' characteristics. All of 479 strains that were isolated from specimen (mainly from sputum) and assumed to be bacteria causing in
infection, were examined. The isolated bacteria were: Staphylococcus aureus 90, Streptococcus pneumoniae 74, Haemophilus influenzae 82, Pseudomonas aeruginosa (non-mucoid) 60, P. aeruginosa (mucoid) 31, Klebsiella pneumoniae 41, and Moraxella catarrhalis 34. Of 90 S. aureus strains, those with 2 μg/mL or less of MIC of
oxacillin (
methicillin-susceptible S. aureus: MSSA) and those with 4 μg/mL or more of MIC of
oxacillin (methicillin-resistant S. aureus: MRSA) were 43 (47.8%) and 47 (52.2%) strains, respectively. Against MSSA,
imipenem had the most potent antibacterial activity and inhibited the growth of all strains at 0.063 μg/mL or less. Against MRSA,
vancomycin and
arbekacin showed the potent activity and inhibited the growth of all the strains at 2 and 4 μg/mL, respectively.
Linezolid also showed the great activity and inhibited the growth of all the strains at 2 μg/mL.
Carbapenems and penems showed the most potent activities against S. pneumoniae and
panipenem inhibited the growth of all the strains at 0.125 μg/mL.
Imipenem and
faropenem also had a preferable activity and inhibited the growth of all the strains at 0.25 and 0.5 μg/mL, respectively. In contrast, there were high-resistant strains (MIC: > 128 μg/mL) for
erythromycin (51.4%) and
clindamycin (35.1%). Against H. influenzae,
levofloxacin showed the most potent activity and its MIC90 was 0.063 μg/mL or less.
Meropenem showed the most potent activity against P. aeruginosa (mucoid) and its MIC90 was 1 μg/mL. Against the non-mucoid type of P. aeruginosa,
tobramycin had the most potent activity and its MIC90 was 2 μg/mL. Against K. pneumoniae,
cefozopran had the most potent activity and inhibited the growth of all the strains at 0.125 μg/mL or less. All the
antibacterial agents except
ampicillin generally showed a potent activity against M. catarrhalis and the MIC90 of them were 2 μg/mL or less. The majority number (60.0%) of the patients with respiratory
infection was aged 70 years or older.
Bacterial pneumonia and
chronic bronchitis accounted for 48.8% and 31.7% of all the respiratory
infection, respectively. The bacteria frequently isolated from the patients with
bacterial pneumonia were S. aureus (21.5%), S. pneumoniae (20.2%), and H. influenzae (16.7%). S. aureus (21.9%) and P. aeruginosa (20.0%) also were frequently isolated from the patients with
chronic bronchitis. The bacteria frequently isolated from the patients were S. pneumoniae (21.5%) and H. influenzae (20.5%) before administration of the
antibacterial agents. The bacteria frequently isolated from the patients previously treated with cephems and
macrolides were P. aeruginosa, and the isolation frequencies were 28.6% and 47.2%, respectively.