Susceptibilities of bacteria isolated from patients with lower respiratory infectious diseases to antibacterial agents (2009)

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 2μg/mL or less of MIC of oxacillin (methicillin susceptible S. aureus: MSSA) and those with 4μg/mL or more of MIC of oxacillin (methicillinresistant 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 0.063μg/mL or less. Against MRSA, vancomycin and arbekacin showed the potent activity and inhibited the growth of all the strains at 2 and 4μg/mL, respectively. Linezolid also showed the great activity and inhibited the growth of all the strains at 2μg/mL. Carbapenems and penems showed the most potent activities against S. pneumoniae and panipenem inhibited the growth of all the strains at 0.125μg/mL. Imipenem and faropenem also had a preferable activity and inhibited the growth of all the strains at 0.25 and 0.5μg/mL, respectively. In contrast, there were high-resistant strains (MIC: >128μg/mL) for erythromycin (51.4%) and clindamycin (35.1%). Against H. influenzae, levofloxacin showed the most potent activity and its MIC90 was 0.063μg/mL or less. Meropenem showed the most potent activity against P. aeruginosa (mucoid) and its MIC90 was 1μg/mL. Against the non-mucoid type of P. aeruginosa, tobramycin had the most potent activity and its MIC90 was 2μg/mL. Against K. pneumoniae, cefozopran had the most potent activity and inhibited the growth of all the strains at 0.125μg/mL or less. All the antibacterial agents except ampicillin generally showed a potent activity against M. catarrhalis and the MIC90 of them were 2μg/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 iso