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Plasmid Profiles and Toxicity of Escherichia Coli Isolated from Frozen Shrimp in Bangladesh

SHANCHITA RAHNUMA KHAN
Department of Microbiology, University of Dhaka, Dhaka-1000, Bangladesh

KAISAR ALI TALUKDER
International Centre for Diarrhoeal Disease Research,Bangladesh, Mohakhali, GPO Box 128, Dhaka-1000, Bangladesh.

S. I. KHAN
Department of Microbiology, University of Dhaka, Dhaka-1000, Bangladesh

Abstract/ Executive Summary:

A total of 17 locally available and exportable frozen shrimp samples were analyzed for the identification of food poisoning bacteria. Of these, Escherichia coli were isolated from eight samples, two were exportable and six locally available samples. Two isolates were resistant to ampicillin, amoxycillin, bacitracin, erythromycin and tetracycline and a 70 MDa plasmid was detected from these two isolates. None of the eight E. coli isolates produced any thermolabile toxin (LT) and thermostable toxin (ST). They also lacked a- and -hemolysins.

Keywords: Escherichia coli, Plasmid profile, Antimicrobial resistance, Frozen shrimp

Location: Department of Microbiology, University of Dhaka, Dhaka

Start Date: 00-10-2000

End Date: 00-02-2001

Program Area: Animal Health and Management

Commodity: Shrimp

Objectives:

To observe the presence of ETEC strains among E. coli isolated from frozen shrimp, and their antibiotic resistance pattern against important clinical antibiotics and whether the resistance resulted from the presence of plasmids.

Methodology:

During the period of October 2000 to February 2001, a total of 17 shrimp samples were collected directly from processing plants and from outlets of various fish processors, local retailers and department stores in Dhaka. All the shrimp samples were frozen and most of them were processed. Specific amount of the frozen shrimp samples were homogenized in a sterile homogenizer. The smooth homogenate was then subjected to ten-fold serial dilution and 0 .1 ml was spread on MacConkey agar plates (Difeo) and incubated overnight at 37°C. From the plates lactose fermenting pink colonies were picked, and identified as E. coli following standard microbiological and biochemical methods. Plasmid DNA was prepared by the rapid alkaline lysis method of Kado and Liu with some modifications indicated previously. The molecular weight of the unknown plasmid DNA was measured as described by Haider et al. Plasmids present in strains E. coli PDK-9, Rl, RP₄, Sa and V517 described previously were used as molecular weight standards. The E. coli isolates were inoculated on blood agar plates (Difeo) containing 5% defibrinated sheep blood. Following incubation overnight at 37°C, the plates were examined for zones of hemolysis. The isolates were diagnosed for the production of heat-labile toxin (LT) using GMI-ELISA immunoenzyme assay. For the detection of LT-positive strains, ETEC strains positive for LT (ETEC strain 286C2) and negative for LT (ETEC strain ST 6411) were used as the positive and negative controls, respectively for each assay. The presence of pure heat-stable toxin (ST) in E. coli strains was determined by inhibition ELISA as described earlier.

Source of Information: Dhaka Univ. J. Biol. Sci. 13(2): 173-179, 2004 (July)

Article Link (Online Journal):

Funding Source:

Total Budget (Tk.) :

Achievement/Findings:

In this study, although 70 MDa plasmids were isolated from two of the isolated E. coli strains, but neither of these isolates showed any hemolytic activity on the blood agar plates. The E. coli isolates were studied for production of ST/LT. None of the isolates were found to possess either LT or ST. This suggests that none of the eight isolates were enterotoxigenic

Knowledge Management: Journal