Susceptibilities of bacteria isolated from patients with lower respiratory infectious diseases to antibiotics (2006)

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 2μg/ml or less of MIC of oxacillin (methicillin-susceptible S. aureus: MSSA) and those with 4μg/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 0.063μg/ml or less. Against MRSA, vancomycin and linezolid showed the most potent activity and inhibited the growth of all the strains at 1μg/ml. Carbapenems showed the most potent activities against S. pneumoniae and in particular, panipenem inhibited the growth of all the strains at 0.063μg/ml or less. Imipenem and faropenem also had a preferable activity and inhibited the growth of all the strains at 0.125 and 0.5μg/ml, respectively. In contrast, there were high-resistant strains (MIC: over 128μg/ml) for erythromycin (45.8%) and clindamycin (20.8%). 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 0.5μg/ml. Against P. aeruginosa (non-mucoid), tobramycin had the most potent activity and its MIC₉₀ was 2μg/ml. Against K. pneumoniae, cefozopran was the most potent activity and inhibited the growth of all the strains at 0.063μg/ml or less. Also, 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 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%.