Distribution of Virulence Genes, Enterotoxin and Biofilm Formation Among Enteroaggregative Escherichia Coli (EAEC) Strains Isolated From Stools of Children With Diarrhea in South East Iran

Abstract

Background:Enteroaggregative Escherichia coli (EAEC) is commonly associated with pediatric diarrhea, in developing countries. Objectives: In this study, we investigated the distribution of virulence genes, enterotoxin and biofilm formation among EAEC strains isolated from stools of children with diarrhea referred to three hospitals in south east Iran. Patients and Methods: A total of 464 diarrheic stools were screen for the presence of E. coli using conventional tests. Well isolated colonies were then evaluated for the presence of EAEC diagnostic genes (aggR and pCVD432) by duplex polymerase chain reaction (D-PCR). Positive samples were further subjected to three sets of multiplex-PCR for detection of fimbrial subunits (AAF), serine protease autotransporter toxins (SPATE) and at least one enterotoxin gene. Hemolytic activity was observed on sheep blood agar. Biofilm formation was measured by using a microtiter plate assay. Results: Among the 322 E. coli isolated, 23 were identified as EAEC. All EAEC carried a 630-bp fragment of the plasmid (pAA) encoded pCVD432 and aggR genes. Four major EAEC fimbriae variants aggA, agg4A, agg3A and aafA were detected, with the frequencies of 21.7% (n = 5), 26.8% (n = 6), 21.7% (n = 5) and 4.3% (n = 1), respectively. The class I and II virulence toxins pic, sat, sepA, pet and sigA were detected with frequencies of 56.5% (n = 13), 30.4% (n = 7), 26.8% (n = 6), 21.7% (n = 5) and 4.3% (n = 1), respectively. A heat-stable Shigella enterotoxin-1 gene (astA) was detected in 17.3% (n = 4) of the cases. In addition, 56.4% of the EAEC isolates were α-hemolytic. Quantification of the biofilm revealed six isolates with strong biofilm. Conclusions: Overall, except for pCVD432 and aggR, we detected high heterogeneity of virulence factors among EAEC isolates causing diarrhea in children. One set of genes, in the combination, pic-sepA-agg4A, was associated with strong biofilm.

Genetic Virulence Profile of Enteroaggregative Escherichia coli Strains Isolated from Danish Children with Either Acute or Persistent Diarrhea

“…Colonization of the gut is accomplished by adhesion facilitated by the EAEC aggregative adhesion fimbriae (AAFs) with five variants AAF/I—AAF/V (Czeczulin et al, 1997 ; Shamir et al, 2010 ; Jønsson et al, 2015 ; Nezarieh et al, 2015 ). An important pathogenic trait of EAEC is the formation of biofilm (Hicks et al, 1996 ), which is in general associated with persistent infection (Costerton et al, 1999 ).…”

“…An important pathogenic trait of EAEC is the formation of biofilm (Hicks et al, 1996 ), which is in general associated with persistent infection (Costerton et al, 1999 ). Biofilm formation has been associated with the genes aatA, aggR, pic, sepA , and sigA (Mohamed et al, 2007 ; Mendez-Arancibia et al, 2008 ; Nezarieh et al, 2015 ) and the AAFs (Czeczulin et al, 1997 ; Shamir et al, 2010 ; Jønsson et al, 2015 ; Nezarieh et al, 2015 ). The genes sat and the pet are toxins that causes considerable damage to the intestinal epithelium (Eslava et al, 1998 ; Taddei et al, 2005 ).…”

Relationship between Nutritional Status, Food Insecurity, and Causes of Hospitalization of Children with Infectious Diseases

“…Infectious diseases are the most common cause of hospitalization in children aged 2 -6 years, which could be owing to their poor nutrition (9). These infectious diseases can include gastrointestinal infections such as diarrhea as an important factor affecting child mortality worldwide (10,11), respiratory tract infections as the most important cause of death in children under 5 years old (12), as well as pediatric tuberculosis (TB) as the cause of mortality among thousands of children per year (13,14), which is different from adult TB in various aspects (15). Additionally, tooth decay in children is another disease that can have an enormous impact on their lives (16) and it is associated with a person's type of nutrition (17).…”

Antimicrobial Susceptibility Patterns of Enteroaggregative E. coli, as the Most Common Diarrheagenic E. coli, Associated to Gastroenteritis Outbreaks in Iran

“…However, some strains of E. coli have acquired specific virulence factors and have developed the ability to cause a variety of diseases in the gastrointestinal tract, urinary, as well as central nervous system (2,3). Diarrheagenic E. coli represent 1 of the most common etiological causes of community-acquired diarrhea in children worldwide (1,4). Among the E. coli that cause diarrhea, there are at least 6 well-described groups, each corresponding to a distinct clinical syndrome with distinct epidemiological and pathologic schemes.…”

“…Enteroaggregative E. coli was first discovered in 1987 by Nataro and his colleagues (5) and was commonly recognized as a cause of endemic and epidemic diarrhea worldwide (6,7). Diarrhea caused by this diarrheagenic E. coli is often watery, but could also be accompanied by mucous and blood (4,5). Enteroaggregative E. coli is identified by the presence of the known virulence genes including an enteroaggregative heat stable toxin (astA), a transcriptional activator (aggR), and a dispersin secretory protein (aap) (2,8).…”