The effect of Lactobacillus species as probiotic on some virulence factor of Escherichia coli

Other Title(s)

تأثير بكتريا الحليب العصوية كمفرز حيوي لتثبيط بعض عوامل الضراوة لبكتريا القولون

Dissertant

al-Maliki, Alya Abd al-Husayn

Thesis advisor

Hamzah, Subhi Jawad

Comitee Members

Nasir, Nizar E.
al-Qazzaz, Abd al-Karim Abd al-Razzaq Abd al-Wahhab
al-Saffar, Janan Muhammad Jawad

University

University of Baghdad

Faculty

College of Science

Department

Biotechnology Department

University Country

Iraq

Degree

Master

Degree Date

2011

English Abstract

♣ A total of twenty isolates of Lactobacillus species were selected from samples collected from different sources (food and mouth cavity).

Also twenty one isolates of E.coli were selected from samples collected from children with diarrhea infection.

♣ All these isolates were characterized according to their colonial morphology and microscopic characteristics, and biochemical tests.

Number of Lactobacillus species were later identified to species level as L.salivarius, L.acidophilus, L.acidophilus, and L.amylophilus.

♣ The twenty one isolates of E.coli were tested for adhesion and the results showed that all isolates were able to adhere to human buccal cavity epithelial cells, isolates AH17, AH7, and AH2 were selected as long as they show the highest adherence with a significant difference (p≤ 0.05) when mean values of adhesion capabilities were (60.50 ± 7.101), (60.15 ± 6.877), (46.95 ± 7.379) bacteria / epithelial cell respectively, whereas isolate AH18 represent the lowest adherence capability among the whole isolates with mean value (19.05 ± 3.578) bacteria / epithelial cell.

Thus these four isolates were selected for further experiments to detected the virulence factors including capsule and type 1 pili.

Results showed that the four isolates were able to expressed type 1 pili, while isolates AH17, and AH7 were able to form capsule.

♣ Antibiotics sensitivity of E.coli were tested towards number of antibiotics, then minimal inhibitory concentration (MIC) were specified for tetracycline and streptomycin in the range (256 – 1024 μg/ml), while the lowest MIC was for chloramphenicol in the range (8-16 μg/ml).

♣ Antagonism experiments indicate that a high inhibitory effect towards all E.coli isolates were found with the presence of cultured Lactobacillus species as well as either concentrated washed cells or filter sterilized liquid of cultured Lactobacillus.

The effect were reduced dramatically with dilutions.

I ♣ Inhibition of E.coli Adhesion by different concentrations of Lactobacillus species was studied by using suspended bacterial cells of selected isolates of Lactobacillus (L.salivarius lact1, L.acidophilus lact2, L.acidophilus lact5, and L.amylophilus lact13), it was found that a strongly inhibitory effect towards E.coli adhesion (AH17) by using concentrated suspended Lactobacillus cells, as well as concentrated filter sterilized liquid.

♣ Agarose gel electrophoresis was performed to generate a plasmid profile for the selected isolate of E.coli.

It was found that AH17 contain two bands of small plasmids DNA their molecular sizes ranged from (4kb) for the smaller one to (10.5kb) for the larger one as compared with DNA of molecular size marker (lambda phage digested with EcoR1& Hind III).

♣ Plasmid curing experiment for E.coli was performed by using chemical agents (SDS, ethidium bromide).

The results showed that treating with ethidium bromide (500 μg / ml) was efficient to cure the plasmids, and the AH17 isolate show phenotypic changes for antibiotic sensitivity as well as significant decrease in adherence capability (p≤ 0.05) with mean (1.1 ± 1.6).

♣ Transformation of plasmid DNA of E.coli was performed using standard E.coli HB101 strain as recipient for the plasmids of AH17 isolate.

The results showed that the highest transformation frequency with antibiotics resistance was for chloramphenicol with average (9.4×10-2), while the lowest transformation frequency was for Cephalothin with average (2×10-3).

During inspecting their adhesability, it was observed that a transformant, designated (T17), show adherence capability with means : (53.45 ± 1.25).

However, other transformant showed no significant differences (p≥ 0.05) in the adherence capability, besides that, the mean of adhesion capabilities for these transformant were less than of the wild type isolate.

Main Subjects

Biology

Topics

• Bacterioses
• Bacteria
• classification Libraries

No. of Pages

168

Table of Contents

• APA
• MLA
• AMA

Language

English

Data Type

Arab Theses

Record ID

BIM-600682