Isolation of gram negative bacteria from raw milk samples in Burdur province, identification by MALDI-TOF MS and determination of some virulence characteristics

33 Gram-negative bacteria were isolated from CHROMagar™ ESBL broth from milk samples collected from Burdur province and its districts. Out of 33 bacteria, 15 Stenotrophomanos maltophilia, 5 Pseudomonas aeruginosa, 5 Escherichia coli, 3 Klebsiella oxytoca, 2 Chryseobacterium gleum, 1 Enterobacter claocoe 1 Hafnia alvei and Acinetobacter baumannii were identified by MALDI TOF-MS. When all antibiotics were evaluated in the disk diffusion method, it was determined that the most sensitive strain was H. alvei YH102A. H. alvei YH102A strain was found to be sensitive to ceftazidime (30 µg), cefpodaxime (10 µg), cefotaxime (30 µg), cefepime (30 µg) and cefepime (5 µg) antibiotics. With the VITEK® 2 Compact system, the highest resistance was detected in the ceftiofur antibiotic, and the highest sensitivity was detected in the trimethoprim/SMZ antibiotic. In our study, it was determined that E. coli YH131A strain had the highest antibiotic resistance profile, while it was resistant to 13 of the 16 antibiotics used in the study, it was sensitive only to amoxicillin/calvulanic acid, ticarcillin/clavulanic acid and imipenem antibiotics. As a result of the analysis carried out to determine virulence characteristics, DNAse activity was not determined in all strains examined. S. maltophilia (YH6A, YH100, YH101, YH103, YH129D), E. coli (YH131A, YH140B), C. gleum YH67B and A. baumannii YH138B strains were found to be positive for gelatinase production. While decarboxylase activity was not determined in histidine, ornithine and lysine amino acids of the strains, the most decarboxylated amino acid by the strains was determined as tryptophan. P. aeruginosa (YH27C, YH152B, YH138A, YH148A), S. maltophilia (YH101, YH103, YH113, YH135B) and E. cloacae YH27A strains showed beta hemolysis. Eventhough S. maltophilia YH64 strain showed alpha hemolysis. S. maltophilia (YH12A, YH94A, YH97B, YH99, YH129D), E. coli (YH126A, YH131A), K. oxytoca YH98B, H. alvei YH102A showed weak alpha hemolysis, other strains did not show hemolysis. S. maltophilia YH6A and P. aeruginosa YH27C strains were found to be strong biofilm producers with a value of 0.64, while other strains were found to be weak biofilm producers between 0.15 and 0.38. In the experiment of extracellular protease production; It was determined that 17 strains formed a zone in casein, milk and skim milk agar, and E. coli YH140B was the only strain that did not form a zone in all three media.