Study towards the detection of virulence factor genes in diarrhoeagenic Escherichia coli

  • Daniel Alves De Figueiredo Filho

    Student thesis: Masters by Research - CDU


    Diarrhea remains one of the main sources of mortality and morbidity in today's world and a significant causal agent is diarrheagenic Escherichia coli. These bacteria are a particular problem in developing countries although traveler's diarrhea and hemorrhagic colitis are also a problem in developed countries (Nataro et al, 1998).

    In the Northern Territory (NT) of Australia, Aboriginal children are greatly exposed to: bacterial pathogens in contaminated food and water; overcrowded living conditions with high rates of faecal-oral transmission; frequent intestinal infections;and small bowel bacterial contamination which result in more frequent diarrheal episodes (Brewster et al, 2002).

    This study was developed to provide new information about the prevalence of diarrheagenic E. coli virulence factors, specially EAggEC and EIEC which have been suspected in sporadic infections of diarrheal and non-diarrheal Aboriginal children(<6 years old) admitted to the Royal Darwin Hospital.

    The importance of virulence factors in diarrheagenic E. coli as a possible cause of acute and chronic diarrhea in Aboriginal children was investigated. From 128 bacterial samples collected from 72 Aboriginal children admitted to hospital, 64 with diarrhea and 8 healthy controls, broth cultures were prepared and processed for DNA extractions and used in polymerase chain reactions (PCR). PCR made possible thedetection of (aafl, aaj3, EAggEC, DAEC, EJEC, hlyA, eaeA, bfpA, stxl and stx2)virulence factor genes used to identify specific diarrheagenic E. coli types.

    Positive PCR bacterial samples of all identified diarrheagenic E. coli were then statistically analysed to see the prevalence of their virulence factors. Also, positive PCR samples of EJEC and EAggEC were then tested by using the restriction fragment length of polymorphism (RFLP) and randomly amplified polymorphic DNA (RAPD)analysis.

    From this study, it was found that both EAggEC and EPEC were the most prevalent potential bacteria found in Aboriginal children with diarrhea and as well in healthy controls. Prevalence of EJEC bacteria suspected to cause infection in Aboriginal children was not significantly found in our study. Also, RFLP and RAPD results revealed that diarrhea cases in Aboriginal children could possibly be associated with potentially EAggEC carrying multiple virulence factors or harboured by different AA mobile plasmid.

    Information in this study will play an important role in the future epidemiological study of diarrhoea in Aboriginal children. And subsequently be used as a helpful source of information in understanding what etiological agents are prevalent in the Aboriginal community children admitted to the hospital.
    Date of Award2004
    Original languageEnglish
    SupervisorPeter Fagan (Supervisor)

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