Enterohemorrhagic Escherichia coli O157 in milk and dairy products from Libya: Isolation and molecular identification by partial sequencing of 16S rDNA.

Aboubaker M Garbaj,Salah M Azwai,Ashraf A Moawad,Fatim T Gammoudi,Said K Abolghait,Hesham T Naas,Ilaria Barbieri,Enas M Awad,Ibrahim M Eldaghayes

doi:10.14202/vetworld.2016.1184-1189

Abstract

Aim:The aim of this work was to isolate and molecularly identify enterohemorrhagic Escherichia coli (EHEC) O157 in milk and dairy products in Libya, in addition; to clear the accuracy of cultural and biochemical identification as compared with molecular identification by partial sequencing of 16S rDNA for the existing isolates.Materials and Methods:A total of 108 samples of raw milk (cow, she-camel, and goat) and locally made dairy products (fermented cow’s milk, Maasora, Ricotta and ice cream) were collected from some regions (Janzour, Tripoli, Kremiya, Tajoura and Tobruk) in Libya. Samples were subjected to microbiological analysis for isolation of E. coli that was detected by conventional cultural and molecular method using polymerase chain reaction and partial sequencing of 16S rDNA.Results:Out of 108 samples, only 27 isolates were found to be EHEC O157 based on their cultural characteristics (Tellurite-Cefixime-Sorbitol MacConkey) that include 3 isolates from cow’s milk (11%), 3 isolates from she-camel’s milk (11%), two isolates from goat’s milk (7.4%) and 7 isolates from fermented raw milk samples (26%), isolates from fresh locally made soft cheeses (Maasora and Ricotta) were 9 (33%) and 3 (11%), respectively, while none of the ice cream samples revealed any growth. However, out of these 27 isolates, only 11 were confirmed to be E. coli by partial sequencing of 16S rDNA and E. coli O157 Latex agglutination test. Phylogenetic analysis revealed that majority of local E. coli isolates were related to E. coli O157:H7 FRIK944 strain.Conclusion:These results can be used for further studies on EHEC O157 as an emerging foodborne pathogen and its role in human infection in Libya.

Highlights

Milk has played a major contribution in the human diet in many different countries across the world
With the exception of ice cream samples that revealed no growth on tellurite-cefixime-sorbitol MacConkey (TC-SMAC), other samples showed differences in the recovery rate of suspected colonies; the lowest recorded in goat’s milk where only 7.4% (2/27) showed colonies suspected to be Escherichia coli (EHEC) O157, while the highest rates of isolation recorded in Massora cheese 33% (9/27) followed by fermented cow’s milk 26% (7/27) (Table-1)
Bacterial isolates recovered (27) from growth on TC-SMAC were subjected to molecular analysis by DNA extraction followed by partial sequencing of their 16S rDNA

Summary

Introduction

Milk has played a major contribution in the human diet in many different countries across the world. It is not surprising that considerable attention has been paid over many years to improve milk quality and in particular the hygienic quality. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/ publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated

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