Isolation and Characterisation of Esherichia coli O157 in Human Stool Samples from Parts of K...

H.O. AbdulAziz, Maryam Aminu, D. A. Machido

American Journal of Food Science and Technology

Isolation and Characterisation of Esherichia coli O157 in Human Stool Samples from Parts of Kaduna Metropolis Nigeria

H.O. AbdulAziz1,, Maryam Aminu1, D. A. Machido1

1Department of Microbiology, Faculty of Science, Ahmadu Bello University Zaria


Esherichia coli O157 is pathogenic strain of Esherichia coli that is known to cause diarrhoea leading to fluid loss, electrolyte imbalance and other severe complications like haemolytic uraemic syndrome. This work was therefore aimed at isolating and serologically characterising Esherichia coli O157 from human stool with the set objectives of identifying the risk factors associated with diarrhoea and determining the serological characteristics of Esherichia coli isolates. A total of one hundred and forty four (144) stool samples were collected from patients with age ranging from zero to sixty (0-60) years, statistical analysis of the risk factors showed that only zero to five years age range of the respondents had a significant statistical difference of 0.012 (P<0.05). The presumptive Esherichia coli isolates that appeared as green metallic sheen on Eosin Methylene Blue agar were picked and confirmed biochemically as Esherichia coli using Microgen biochemical test kit. The confirmed E. coli isolates were then cultured on Sorbitol MacConkey Agar and the two isolates that appeared colourless on SMAC were confirmed serologically as Esherichia coli O157 using the latex agglutination test kit. Although 1.39% prevalence rate of Esherichia coli O157 was obtained it is pertinent to note that, Esherichia coli O157 is becoming a public health threat because of the debilitating effects it has on humans and also due to its low infectivity dose. There is therefore, the need for more public awareness to educate our citizens on ways of improving on the unsanitary environment.

Cite this article:

  • H.O. AbdulAziz, Maryam Aminu, D. A. Machido. Isolation and Characterisation of Esherichia coli O157 in Human Stool Samples from Parts of Kaduna Metropolis Nigeria. American Journal of Food Science and Technology. Vol. 4, No. 5, 2016, pp 125-128.
  • AbdulAziz, H.O., Maryam Aminu, and D. A. Machido. "Isolation and Characterisation of Esherichia coli O157 in Human Stool Samples from Parts of Kaduna Metropolis Nigeria." American Journal of Food Science and Technology 4.5 (2016): 125-128.
  • AbdulAziz, H. , Aminu, M. , & Machido, D. A. (2016). Isolation and Characterisation of Esherichia coli O157 in Human Stool Samples from Parts of Kaduna Metropolis Nigeria. American Journal of Food Science and Technology, 4(5), 125-128.
  • AbdulAziz, H.O., Maryam Aminu, and D. A. Machido. "Isolation and Characterisation of Esherichia coli O157 in Human Stool Samples from Parts of Kaduna Metropolis Nigeria." American Journal of Food Science and Technology 4, no. 5 (2016): 125-128.

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1. Introduction

Enteric pathogens are gastrointestinal organisms known to cause gastrointestinal infection. Gastrointestinal infection also known as gastroenteritis is any infection caused by Viruses, Bacteria or Parasites and is characterised by excessive watery diarrhoea and stomach pain. Acute diarrhoea is a common cause of death in developing countries and the second most common cause of infant deaths worldwide [16]. It is estimated that 1.3 billion episodes of diarrhoea occur in children below five years of age with about 760,000 deaths occurring yearly [18].

Escherichia coli is a common inhabitant of the human and animal gut, but can also be found in the physical environment such as; water, soil and vegetation and are thus referred to as being ubiquitous. Many Escherichia coli strains are usually not harmful and act as commensals in the intestine of warm blooded animals, but some few strains have been found to cause mild to severe disease in man. Escherichia coli O157:H7 is a pathogenic strain of Escherichia coli that is known to cause diarrhoea and other severe complications such as haemolytic colitis, haemolytic uraemic syndrome and thrombotic thrombocytopenic pupura in humans. The majority of E. coli O157:H7 strains can be distinguished from most E. coli by their inability to ferment sorbitol rapidly and by their lack of production of glucuronidase [1, 5]. They also differ from other E. coli because of their ability to produce verocytotoxins (VT) or shiga toxins (ST).

Escherichia coli O157:H7 is a zoonotic food borne and waterborne pathogens with cattle serving as the main reservoir for this organism which they shed in their faeces and is often times used as manure by farmers. Transmission of this organism is usually through faecal oral route and Humans become infected with this pathogen through consumption of faecally contaminated fruits, vegetables and water or through person to person contact and direct contact with infected faeces.

Escherichia coli O157:H7 is responsible for several outbreaks of gastroenteritis around the world and causes approximately 70,000 illnesses and 60 deaths annually in the United States [8]. In developing countries where diarrhoeal disease and associated mortality are much more pervasive there is very limited information about E. coli 0157:H7 prevalence [9]. The first major outbreak of bloody diarrhoea in the developing world associated with E. coli 0157:H7 occurred in Swaziland in 1992 [3] and infection with this pathogenic strain may have accounted for tens of thousands of cases during this epidemic. There have also been reported outbreaks in Democratic Republic of Congo.In Nigeria, some prevalence studies have been reported in some South Western cities [11, 12, 14].

Due to the low infective dose of E. coli O157:H7, the potential severity of the infection and the possibility of laboratory-acquired infections [15], an inoculation of fewer than 10 to 100 colony forming units (cfu) of E. coli O157:H7 is sufficient to cause infection, compared to over one-million cfu for other pathogenic E. coli strains [4]. Their ability to survive in the environment and the environmental contamination with Escherichia coli O157:H7 may be an important public health problem [7, 10]. Also another major problem with E. coli O157:H7 is that it is not detected by the usual methods used to isolate and identify “traditional” enteric bacterial pathogens therefore, most microbiology laboratories in many countries of Africa do not routinely test for E.coli O157:H7, hence many infections may go unrecognized (Wittenberg, 1999). This work therefore, sought to isolate and characterise Escherichia coli O157 from human stool in parts of Kaduna Metropolis, Nigeria.

2. Material and Method

2.1. Study Area

Kaduna metropolis is located in Kaduna state Northern Nigeria, and with a global location of between longitude 30o east of Greenwich meridian and latitude 0900 and 11 30o North of the equator. Kaduna Metropolis is made up of 3 Local Government Areas namely Igabi, Kaduna South and Chikun. Therefore, samples were collected from 5 hospitals located within these Local governments.

2.2. Sampling

A total of 144 stool samples were collected from 5 different hospitals located within Kaduna state which are; Yusuf Dantsoho Memorial hospital Tudun wada, Gwamna Awan General Hospital Kakuri, Kawo General Hospital Kawo, Ungwar rimi primary health clinic Ungwar rimi and Shehu Idris School of Health Technology practice area Tudun Wada.

2.3. Isolation of and Identification of E. coli Isolates

The stool samples were cultured on Eosin Methylene Blue (EMB) agar and the colonies that appeared as green with black metallic sheen were pick and sub cultured on fresh EMB agar plates to obtain presumptive E. coli isolates. These presumptive E. coli isolates were subjected to the conventional biochemical test for E. coli (IMViC), isolates that had typical E. coli characteristics on IMViC test were then further confirmed by biochemically characterizing them using the MicrogenGnA+B-ID System test kit.

2.4. Isolation of E. coli O157

The confirmed E. coli isolates were cultured on SorbitalMacConkey Agar plates (SMAC), the colonies that appeared colourless on SMAC were tagged as presumptive E. coli O157 and were Serologically confirmed as E. coli O157 using the latex agglutination test kit (Oxoid, Basingstoke, and Hampshire, England).

3. Results

A total of 17 (11.80%) isolates were biochemically confirmed as Escherichia coli isolates out of the 144 stool samples collected. Yusuf Dantsoho Memorial Hospital had the highest number of isolates while Kawo General Hospital had the lowest number of isolates. This result is presented on Table 1.

Table 1. Frequency of Occurrence of E. coli in Stool Samples Collected from 5 Hospitals in Kaduna Metropolis

Analysis of the risk factors associated with diarrhoea was carried out using the Fischer Exact Test and the result shows that only age of the respondents had a statistical significant difference of p<0.05 (p=0.012). the other risk factors that were analysed had p values greater than 0.05 which means they had no statistical significant difference. This result is highlighted on Table 2.

Serological characterisation was carried out and the result shows that only 2 isolates were positive for E. coli O157 and these 2 isolates were obtained from Yusuf Dantsoho Memorial Hospital with a prevalence of 6.1%. These results are presented on Table 3 and Table 4.

Table 3. Identification of Escherichia coli O157:H7

Table 4. Frequency of Occurrence of E. coli O157 in Stool Collected From Five Hospitals in Kaduna

4. Discussion

The findings in this study indicates that age remains a major risk factor in diarrhoea disease, children between the ages of 0-5 are highly vulnerable to diarrhoea as this study has shown. The prevalence of 9.8% diarrhoea in respondents 0-5 years in this work, is higher than the 2.6% obtained by Yilgwan and Okolo, [17] in Jos Plateau State and lower than the 43.1% obtained by Ifeanyi et al. [6] in Abuja. These differences might be due to breaches in sanitation and hygiene infrastructure of the respondents from these cities. The high occurrence rate of diarrhoea among children 0-5 years in this study may be due to the fact that children within this age group on their own cannot differentiate between what to eat and what not to eat; they have not learnt the rudiment of adherence to aseptic or hygienic practices. Another reason for their high vulnerability to diarrhoea may be due to weaker immunity as a result of them having lost their inborn immunity after being weaned from breast milk. Young children use more water over the course of a day given their higher metabolic rates, also their kidneys are less able to conserve water compared to older children and adults as such diarrhoea is usually prevalent and often life threatening too. In this study, it was observed that the number of diarrhoeic stool gotten from adults was quite small compared to that obtained from children and this might not be unrelated to the fact that, adults in the locality rarely visit health institutions when they have diarrhoea unless they perceive the diarrhoea as being serious, usually if blood is present as reported by Okeke et al. [13].

The 1.39% prevalence rate of E. coliO157in this study is lower than the 6% prevalence by Olorunshola et al. [14] in Lagos and the 20% prevalence recorded by Esumeh et al. [2] in Benin. Although there are differences in prevalence rate of Escherichia coli O157 in the stool samples in different parts of Nigeria, this result however shows that Escherichia coli O157 remains an aetiological agent for diarrhoea in Nigeria. The presence of Escherichia coli O157 in stool samples might not be unconnected to the fact that patients have been exposed to unsanitary conditions such as consumption of contaminated water, food, fruits and vegetables.

5. Conclusion

This study has established that diarrhoea is higher among younger children than adults and also confirms the fact that Escherichia coli O157 even though is not part of the routine tests carried out for enteric pathogens in most laboratories visited is still an important aetiology for diarrhoea. It is pertinent to note that an exceptionally low dose of this organism is able to cause infection and once introduced into a closed group or family, it can spread by person-to-person transmission especially by children who are not toilet trained.


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