Objective To observe the bacteriostatic effect of chitosan lactate with different relative molecular masses in vitro. Methods The MICs of the chitosans lactate with different relative molecular masses against the usual pathogens were detected,and the MBCS against two standard strains were also determined. Levofloxacin hydrochloride was used as a control drug. Results The MIC90 of chitosan lactate with 10,30,50kDa against 50 strains of gram-positive cocci and 50 strains of gram-negative bacilli were 0.5,1~4,0.5~4mg?mL-1 and 1~4,0.5~1 ,0.5~4mg?mL-1,respectively. The MIC90 of levofloxacin hydrochloride against the 50 strains of gram-positive cocci and 50 strains of gram-negative bacilli were 4～8 and 8～16?g?mL-1,respectively. ATCC 25923 strain of S.aureus and ATCC 25922 strain of E.coli could be killed by 10kDa chitosan lactate in the concentration of 4mg?mL-1. The MBCS of levofloxacin hydrochloride against ATCC25923 strain of S.aureus and ATCC 25922 strain of E.coli were 2 and 4?g?mL-1,respectively. Conclusion The 4 species of the experimental bacteria could be inhibited by the chitosan lactate with 10,30 and 50kDa Mr in vitro,but the inhibitory effect of the chitosan lactate with 10kDa Mr was stronger among them. ATCC 25923 strain of S.aureus and ATCC25923 strain of E.coli could be killed only by 10kDa chitosan lactate in vitro,not by others.

Objective To evaluate the application value with Energy Spectrum CT multi -parameter quanti-tative value in differentiating pulmonary occupying lesions (>0.5cm in diameter).Methods Those were retrospec-tively analyzed on 58 cases in pulmonary occupying lesions performed spectrum dual -phase enhanced CT scan and confirmed by pathology,including malignant group 48 cases;10 cases of benign group.Iodine content(IC)was meas-ured in arterial phase(AP)and venous phase (VP)in iodine based on the image and the level of the aorta,and nor-malized iodine concentrations were calculated in the two phases lesions compared with aorta,and the difference between the two normalized iodine concentrations ICD (ICD =NICvp -NICap).To measure the CT value of lesions on 50keV and 100keV energy image,and calculate the energy attenuation curve slope,namely |Hu (100 kev -50kev)/Hu50 |.The differences of NIC,curve slope,and ICD were compared between benign and malignant pulmonary occupying lesions using independent sample t test method.Results In two phase scan,NIC,curve slope of the venous phase and ICD in malignant group were significantly higher than the benign group,(NIC,curve slope of the venous phase and ICD of the malignant group:NICap:0.180 ±0.051,NICvp:0.463 ±0.086,1.696 ±0.475,ICD:0.284 ± 0.071;NIC,curve slope of the venous phase and ICD of the benign group:NICap:0.123 ±0.062,NICvp:0.290 ± 0.119,1.169 ±0.582,ICD:0.166 ±0.073,),but there was no significant difference between the patients with benign and malignant lesions in curve slope of the arterial phase.Conclusion Energy spectrum CT dual -phase enhanced scan can differentiate the nature of benign and malignant pulmonary occupying lesions,and has certain clinical application value.