AIM: Given the biofilm formation abili- ty of different ST-type Klebsiella pneumoniae, our study was aimed at exploring the inhibitory and clearance of azithromycin combined with levofloxacin on the biofilm of Klebsiella pneumoniae of different ST-types and providing a new strategy for the prevention of biofilm formation in the treatment of post-infectious Klebsiella pneumoniae. METHODS: 9 strains of Klebsiella pneumoniae from all susceptibility groups, 19 strains of Klebsiella pneumoniae producing extended-spectrum β - lactamases (ESBLs), and 37 strains of Carbapenem-resistant Klebsiella pneumoniae (CRKP) were randomly collected from the samples of patients hospitalized in the First Affiliated Hospital of Wannan Medical College from August 2019 to November 2021. The isolates were identified using VITEK MS IVD KB V3.2 and VITEK 2-Compact 60. Multilocus sequence typing (MLST) was performed to analyze the homology of each strain; crystal violet staining was used for semi -quantitative detection of biofilm to compare the differences in biofilm formation ability between different ST-type Klebsiella pneumoniae. Different ST-type strains were selected, and the partial inhibitory concentration index (FICI) was calculated by micro broth dilution method to judge the combination effect and select the optimal combination concentration; crystalline violet staining method was used to investigate the inhibition and clearance effect of azithromycin combined with levofloxacin on the biofilm of different ST-type Klebsiella pneumoniae; laser scanning confocal fluorescence microscopy was used to observe the structural changes of the biofilm of Klebsiella pneumoniae before and after the effect of the antibacterial drugs. RESULTS: MLST typing results showed that the sensitive group of Klebsiella pneumoniae strains had 8 sequences such as ST86, ST727, etc., the ESBLs group strains belonged to 14 sequence types such as ST15, ST37, ST11, etc., of which ST15 accounted for 26.32% (5 / 19). The CRKP group strains belonged to 9 sequence types such as ST11, ST15, ST656, etc., of which ST11 accounted for 48.65% (18/37), ST15 accounted for 27.03% (10/37); ST15 (ESBLs), ST11 (CRKP), ST15 (CRKP) type Klebsiella pneumoniae biofilms all reached maturity on the 5th day, the ST15 (ESBLs) group had a stronger ability to produce material to be membranous than the ST15 (CRKP) group. The ST11 (CRKP) group had a stronger ability to produce material to be membranous than the ST15 (CRKP) group (P<0.01); the results of azithromycin combined with levofloxacin drug sensitivity showed that it had an additive effect on different ST-type Klebsiella pneumoniae bacteria; in the inhibition of biofilm formation and clearance test, the 2×MIC azithromycin group and the combined concentration group had a stronger inhibition of biofilm formation of different ST-type Klebsiella pneumoniae bacteria, and the inhibitory ability of the combined group was better than that of the single-drug group, and the highest inhibition rate could reach 89.93%; the clearance effects were all combined drug group>azithromycin>levofloxacin, and the highest clearance rate was 44.79%. CONCLUSION: There are differences in biofilm formation ability between different ST-type Klebsiella pneumoniae, and azithromycin combined with levofloxacin has a better inhibitory effect on different ST-type Klebsiella pneumoniae biofilm, conbined application can be used in the treatment of biofilm infections early stage.