The infection of carbapenem resistant klebsiella pneumoniae (CRKP) is increasingly serious.Based on the early experimental basis and relevant research background,this study intends to separate and purify the CRKP from the bronchoalveolar lavage fluid (BALF) of the clinical patients.Designed by checkerboard assay and time-kill assay(TKA)，this study can explore the best combination therapy based on carbapenems.

1. Collect the BALF from patients diagnosed with CRKP infection in surgical intensive care unit（SICU）of Shanghai 10th people's hospital.
2. Separate and purify the BALF. Divide each CRKP into four treatment groups based on meropenem.

3.1 By checkerboard method and microdilution broth method,get the minimal inhibitory concentration (MICS) of two antibiotics,then calculate the fractional inhibitory concentration (FIC) index according to MIC results.

3.2 Observe the effect of two antibiotics on the growth of CRKP by TKA.

4.By the above two invitro experiments, analyze the data of the experimental results and get the best combination therapy based on carbapenems.

Inclusion Criteria:

• age from 18 to 90.
• infected with CRKP firstly .

Exclusion Criteria:

• APACHE II score > 35
• Vital signs are unstable
• Unable to tolerate fiberoptic bronchoscopy