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International Journal of Current Research and Academic Review-e-iSSN - 2347 - 3215

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Abstract                 Volume:7  Issue-3  Year-2019          Original Research Articles

Online ISSN : 2347 - 3215
Issues : 12 per year
Publisher : Excellent Publishers
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Determination of Antibacterial Activity of Cell Free Extracts of Lactobacillus bulgaricus and Streptococcus thermophilus against Local Isolates of E. coli O157:H7
Zainab M. AlZubaidy*
Diyala University/ Coll. Science, Iraq
*Corresponding author

Escherichia coli serotype O157:H7 is a recently recognized human pathogen associated with hemorrhagic colitis, the efficacy of MacConkey agar containing sorbitol (SMAC medium) instead of lactose as a differential medium for the detection of E. coli O157:H7 in foods cultures was determined in comparison with MacConkey agar. The study involving 200 different food samples, the growth of E. coli O157:H7 on SMAC medium was appeared and purified in pure culture as colorless colonies in contrast to other E. coli, from the total(200) different ready to eat food samples; 96(66.7%) were contaminated with bacteria E. coli O157:H7 and 48 (33.3%) for other E. coli. Bacteriological investigation were done on (200) samples of (meat steak, grilled chicken, shawerma meat and chicken), the result indicated that 144 (72. %) of samples was contaminated with E. coli divided as 96 (66.7%) and 48 (33.3%) for E. coli O157:H7 and other E. coli respectively. The percentage of contamination with E. coli O157:H7 isolated from meat steak, meat shawerma, chicken shawerma, grilled chicken samples were 16(16.6%), 27(28.1%), 32(33.33%), 21(21.8%)) respectively. The susceptibility of E. coli to different antimicrobial drugs was carried out using antibiotic discs, the percentage of sensitivity were (100, 93.7, 89.5, 58.3, 50)%. Against danofloxacin, imipenem, fosfomycin, ciprofloxacin, azithromycin, respectively, and 41.6% for each; trimethoprim, gentamicin and doxycyclin. On the other hand the resistance to ampicillin, amikacin, amoxicillin, cefixime and trtracycline were (97.9, 95.8, 89.5, 68.7, 56.2)% while the isolated bacteria appeared the resistance percentage (83.3%) to chloramphenicol and erythromycin, while it was varied in resistant to cephalothin, nalidixic acid and cefazoline. All the isolates of E. coli O157: H7 96(100%) were resistance to ampicillin, amikacin, chloramphenicol and erythromycin, as well as were resistance to tetracycline, amoxicillin, cefixim and trimethoprim, while all the isolates 96(100%) were sensitive to danofloxacin. The percentage of resistance to gentamycin and nalidixic acid were 38(39.5), and the resistant to azithromycin, cefazoline, doxycycline and cephalothine were varied as 80(83.3), 46(47.9), 44(45.8) and 40(41.6), respectively. In present study Cell free extract (CFE) metabolites of lactic acid bacteria (LAB) include(2) strains of Lactobacillus bulgaricus (LB), and Streptococcus thermophilus (ST) grown in MRS and M17 media have inhibitory effect against E. coli O157:H7and E. coli, by using well diffusion method. The minimum inhibitory concentration of CFE of Lactobacillus bulgaricus and Streptococcus thermophilus at 50, 75 and 100 µl v/v which concentrated for two folds, appeared that the inhibition zones increase as the concentration of CFE increase, and ranged from (10-16)mm against bacteria E. coli, while the effect of Streptococcus thermophilus varied between (6-10) mm against same bacteria. On the other hand the effect of Lb. bulgaricus and St. thermophiles on the growth of E. coli O157:H7 were ranged between (12-20) mm and (5-14) mm respectively, The recent study demonstrated that the two genus of starter bacteria when cultured together gave the greatest antibacterial activity against the two isolates E. coli and E. coli O157:H7, and the inhibition zone was increased as12-22 mm. and 12-18 mm. respectively.

Keywords: E. coli 0157:H7, Starter, SMAC media.
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How to cite this article:

Zainab M. AlZubaidy. 2019. Determination of Antibacterial Activity of Cell Free Extracts of Lactobacillus bulgaricus and Streptococcus thermophilus against Local Isolates of E. coli O157:H7.Int.J.Curr.Res.Aca.Rev. 7(3): 22-31
doi: https://doi.org/10.20546/ijcrar.2019.703.003