[Susceptibilities of bacteria isolated from patients with lower respiratory infectious diseases to antibacterial agents (2011)].

From October 2011 to September 2012, we collected the specimen from 316 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 357 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 51, Streptococcus pneumoniae 73, Haemophilus influenzae 88, Pseudomonas aeruginosa (non-mucoid) 34, P. aeruginosa (mucoid) 9, Klebsiella pneumoniae 21, and Moraxella catarrhalis 33. Of 51 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 31 (60.8%) and 20 (39.2%) 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 showed the potent activity and inhibited the growth of all the strains at 1 μg/mL. 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 0.5 and 1 μg/mL, respectively. In contrast, there were high-resistant strains (MIC: > 128 μg/mL) for erythromycin (53.4%) and clindamycin (3 5.6%). Against H. influenzae, levofloxacin showed the most potent activity and its MIC90 was 0.063 μg/mL or less. Ciprofloxacin showed the most potent activity against P. aeruginosa (mucoid) and inhibited the growth of all the strains at 2 μg/mL or less. Against the non-mucoid type of P. aeruginosa, tobramycin had the most potent activity and its MIC90 was 2 μg/mL. Against K. pneumoniae, imipenem had the most potent activity and inhibited the growth of all the strains at 0.125 μg/mL. 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 (52.9%) of the patients with respiratory infection was aged 70 years or older. Bacterial pneumonia and chronic bronchitis accounted for 59.2% and 19.3% of all the respiratory infection, respectively. The bacteria frequently isolated from the patients with bacterial pneumonia were S. aureus (17.8%), S. pneumoniae (21.6%), and H. influenzae (16.9%). H. influenzae (36.8%) and S. pneumoniae (22.1%) also were frequently isolated from the patients with chronic bronchitis. The bacteria frequently isolated from the patients were S. pneumoniae (23.2%) and H. influenzae (27.3%) before administration of the antibacterial agents. The bacteria frequently isolated from the patients previously treated with cephems were H. influenzae and P. aeruginosa, and the isolation frequencies were 38.5% and 23.1%, respectively. The bacteria frequently isolated from the patients previously treated with macrolides were H. influenzae, the isolation frequencies were 30.0%.