Elsevier

Anaerobe

Volume 11, Issue 6, December 2005, Pages 318-321
Anaerobe

Clinical medicine
Prevalence of Enterotoxigenic Bacteroides fragilis in patients with diarrhea: A controlled study

https://doi.org/10.1016/j.anaerobe.2005.06.001Get rights and content

Abstract

In this age matched controlled study performed in Malatya, a city in east region of Turkey, Enterotoxigenic Bacteroides fragilis (ETBF) was investigated in stool specimens obtained from children and adults with and without diarrhea. A nested polymerase chain reaction (PCR) method was used to detect the enterotoxin gene of B. fragilis in a total of 418 stool samples, including 221 samples from 117 children (aged 0–16 years) and 104 adults (aged >16 years) with diarrhea, and 197 samples from 102 children and 95 adults as control group that was the same age group with those having diarrhea. ETBF was detected in 13 of 117 diarrheal children (11.1%) and 8 of 102 control children (7.8%) (P>0.05). In children aged 1–5 years, the rate of ETBF was significantly higher in patients than in controls (25% versus 9.5%, respectively; P<0.05). On the other hand ETBF was detected similar rates (2.2% and 2.4%, respectively) in children younger than 1 year in both patients and controls. ETBF positivity was not significantly difference between patient and control groups who were older than 5 years of age and adults. The frequency of ETBF in the controls was slightly higher in older persons than in younger ones; however, it was not significant. The rate of ETBF as the only enteropathogen in the patients with ETBF was significantly higher than in controls with ETBF (88% versus 39%, respectively; P<0.02). We found that in east region of Turkey, the prevalence of ETBF was higher in the childhood diarrhea, particularly in aged 1–5. As the only enteropathogen, ETBF may play an important role in diarrheal diseases. Persons after 6 years old can be carrier for ETBF regardless diarrhea.

Introduction

Diarrhea is the second important cause of deaths in the worldwide. Although developed microbiologic methods have been used, the etiology cannot be explained in about half of diarrheal cases [1]. The involvement of Bacteroides fragilis which produces an enterotoxin (fragylisin) in the etiology of diarrheal diseases has been the subject of some investigations for last 25 years. These studies suggest that Enterotoxigenic Bacteroides fragilis (ETBF) may play possible role in diarrheal diseases in different populations [2], [3], [4], [5]. In contrast to these, according to some other reports non-diarrheic humans can be the carrier of ETBF [6], [7], [8].

Detection of ETBF from stool specimens is based on culturing on selective media and analysis of the specimens for the presence of B. fragilis enterotoxin by cytotoxicity assay in HT-29 cell cultures and polymerase chain reaction (PCR) methods [9]. Culture systems require time and their sensitivity can be affected by the storage condition of the specimens prior to culturing. Although the HT29/C1 cell assay is very sensitive detecting as picomolar level of B. fragilis toxin, PCR methods may well be more sensitive for diagnosis [7], [10], [11]. This study was performed to detect the prevalence of ETBF in stool specimens from children and adults with and without diarrhea by nested PCR method.

Section snippets

Patients

The patients with diarrhea who were admitted to the University Hospital and Government Hospital between 19 December 2003 and 16 August 2004 were studied prospectively. These hospitals serve a population of about 850 000 in Malatya, which is a city in east of Turkey. During the period there was no outbreak of diarrhea in this area. All of the patients were outpatients with acute watery diarrhea. Stool specimens were obtained from 104 adults (aged >16 years) and 117 children (aged 0–16 years).

Controls

Results

B. fragilis gene was detected in 22 (10.0%) of the 221 patients and in 23 (11, 7%) of the 197 controls. In totally, there was no significant difference on ETBF positivity between two groups. When the age groups were considered, we found that the prevalence of ETBF was slightly higher in children with diarrhea (11.1%) than in control children (7.8%) (P>0.05). Distribution of ETBF positivitiy according to age group of the patients and controls was shown in Table 1. The rate of ETBF in the

Discussion

Detection rate of ETBF in stool specimens depends on amount of toxin produced, sensitivity of the assay, and stability of the toxin which is susceptible to degradation by proteases [12]. Nested PCR used in this study is rapid, sensitive, specific and useful assay for diagnosis of ETBF in diarrheal diseases. This method can detect as little as 1 pg of enterotoxigenic DNA or 100–1000 cells of ETBF per g of stool [9], [13].

Living conditions in developing countries and different geographic areas may

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