Investigation of biofilm formation by Enterobacter sakazakii isolated from different food samples

In this study a total of 100 food samples (50 cheese and 50 minced meat) presented for consumption in different markets of Ankara were used as material. From 50 cheese samples, a total of 69 Enterobacteriaceae isolates were obtained and 41 Enterobacteriaceae isolates were also obtained from 50 minced meat samples. Biofilm formation by Enterobacter sakazakii and other members of Enterobacteriaceae was investigated by using microplate, congo red agar and standard tube methods. Antibiotic resistance of isolates was determined by using Kirby-Bauer disc diffusion method. Out of 69 Enterobacteriaceae isolates obtained from cheese samples, 20 (29%) Klebsiella spp., 17 (24,64%) Escherichia spp., 15 (21,74) Hafnia spp., 5 (29%) Enterobacter spp., 5 (21,74%) Providencia spp., 2 (2,9%) Serratia spp., 2 (2, 9%) Pantoea spp., 1(1, 45%) Shigella spp., 1(1,45%) Kluyvera spp., 1(1,45%) Yokenella spp., were identified. Similarly, out of 41Enterobacteriaceae isolates obtained from minced meat samples, 7(17,1%) Enterobacter spp.,7 (17,1%) Pantoea spp., 6 (14,6%) Providencia spp., 4 (9,8%) Klebsiella spp., 4 (9,8%) Escherichia spp., 4 (9, 8%) Hafnia spp.,3 (7, 3%) Serratia spp.,3 (7,3%) Citrobacter spp., 2 (4,9%) Kluyvera spp., 1 (2,4%) Leclercia spp.,were identified. Proteolytic, lipolytic, DNase, hemolytic and gelatinase activity of Enterobacter spp. were also investigated. Out of 12 Enterobacter spp., (E. sakazakii, E. cloceae, E. carcenogenus, E. aerogenus) tested , proteolytic, lipolytic, DNase, hemolytic and jelatinaz activity was detected in 7 (58,3%), 9 (75%), 8 (66,7%), 8 (66,7%) and 4 (33,3%) isolates, respectively. By using microplate method all Enterobacter sakazakii isolates showed strong biofilm formation after 24 hours of incubation on tryptone soy broth containing 2% of glucose. On the same media after 48 hours of incubation 78,5% of Enterobacter sakazakii isolates showed strong biofilm formation. After 24 hours of incubation on tryptone soy broth without glucose 50 % of Enterobacter sakazakii isolates showed strong biofilm formaion and on same media after 48 hours of incubation 35,7%of Enterobacter sakazakii izolates showed strong biofilm formation. After 24 hours of incubation on Congo red agar 92,9% of Enterobacter sakazakii izolates were slime factor positive. By using standard tube method 78,6% of Enterobacter sakazakii izolates showed strong biofilm after 24 hours of incubation on TSB containng %2 glucose. After 48 hours of incubation on TSB % 71,42 of Enterobacter sakazakii izolates showed strong biofilm formation. A total of 64 members of Enterobacteriaceae isolates were found to be resistant to streptomycin (78,1%), kanamycin (75%), ampicillin (53.1%), amikacin (45,3%), tetracycline (39%), tobramycin (35,9%), chloramphenicol (14%), nalidik acid (12.5%), imipenem (9,4%), gentamicin (7,8%), cefotaxime (6,3%), trimethoprim-sulfamethoxazole (4,7%).