Jonas D, Engels I, Daschner F D, Frank U
National Reference Centre of Hygiene and Institute of Environmental Medicine and Hospital Epidemiology, University Hospital Freiburg, Hugstetter Strasse 55, D-79106 Freiburg, Germany.
J Antimicrob Chemother. 2000 Sep;46(3):385-90. doi: 10.1093/jac/46.3.385.
We investigated the antimicrobial efficacy of clinically meaningful, low concentrations of azithromycin against intracellular growth of two clinical isolates of Legionella pneumophila. The mature monocytic cell line Mono Mac 6 was used as a model to investigate the effects of antimicrobial agents on L. pneumophila. Extracellular susceptibility was determined by microdilution susceptibility testing in BYEalpha broth after 48 h of incubation. Mono Mac 6 cells infected with L. pneumophila were incubated with various concentrations of azithromycin. After 2 days of incubation, intracellular bacteria were released from the phagocytes and plated on to BCYEalpha agar. Addition of the intracellular-acting antibiotics azithromycin or ciprofloxacin at their MICs (0.5 and 0. 015 mg/L, respectively) resulted in a significant decrease in cfu, of up to approximately 1 log(10) after 48 h of incubation. In contrast, incubation of intraphagocytic L. pneumophila in the presence of antibiotics without intracellular activity (ceftizoxime, imipenem or amoxycillin-clavulanic acid) did not have any effect. Azithromycin inhibited intracellular replication at concentrations as low as 0.125 mg/L, approximately one-quarter of the extracellular MIC. The Mono Mac 6 cell line is a useful infection model for investigating the intracellular activity of antimicrobial agents in vitro. In accordance with clinical data and animal experiments, azithromycin and ciprofloxacin inhibited the intraphagocytic replication of L. pneumophila. In particular, azithromycin killed ingested legionellae in vitro at concentrations below the peak serum concentrations and below the MIC.
我们研究了具有临床意义的低浓度阿奇霉素对两株嗜肺军团菌临床分离株细胞内生长的抗菌效果。成熟单核细胞系Mono Mac 6被用作模型来研究抗菌剂对嗜肺军团菌的影响。通过在BYEalpha肉汤中孵育48小时后的微量稀释药敏试验来确定细胞外药敏性。将感染嗜肺军团菌的Mono Mac 6细胞与不同浓度的阿奇霉素一起孵育。孵育2天后，将细胞内细菌从吞噬细胞中释放出来并接种到BCYEalpha琼脂平板上。添加细胞内作用抗生素阿奇霉素或环丙沙星，其浓度分别为各自的最低抑菌浓度（MIC，分别为0.5和0.015mg/L），孵育48小时后，菌落形成单位（cfu）显著减少，最多约减少1个对数（10）。相比之下，在无细胞内活性的抗生素（头孢唑肟、亚胺培南或阿莫西林-克拉维酸）存在下孵育吞噬细胞内的嗜肺军团菌没有任何效果。阿奇霉素在低至0.125mg/L的浓度下就能抑制细胞内复制，约为细胞外MIC的四分之一。Mono Mac 6细胞系是用于体外研究抗菌剂细胞内活性的有用感染模型。根据临床数据和动物实验，阿奇霉素和环丙沙星抑制了嗜肺军团菌在吞噬细胞内的复制。特别是，阿奇霉素在体外能在低于血清峰值浓度和低于MIC的浓度下杀死被吞噬的军团菌。
