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Virulence properties of Escherichia coli O111:H12 strains
V Monteiro-Neto1, L C Campos, A J Ferreira
1Departamento de Microbiologia, Universidade de São Paulo, Brazil.
Insights
This study found that certain Escherichia coli O111:H12 strains causing childhood diarrhea exhibit aggregative adherence. Their specific adherence genes differ from previously identified ones in enteroaggregative E. coli.
Area of Science:
- Microbiology
- Infectious Diseases
- Molecular Biology
Background:
- Escherichia coli (E. coli) is a common cause of diarrheal diseases in children.
- Certain serotypes, like O111:H12, have been historically linked to infantile diarrhea.
- Understanding the virulence factors of specific E. coli strains is crucial for disease management.
Purpose of the Study:
- To investigate the adherence properties and virulence characteristics of E. coli O111:H12 strains isolated from children with acute diarrhea.
- To determine if these strains possess known virulence genes associated with enteropathogenic E. coli.
- To characterize the genetic basis of the observed adherence phenotype.
Main Methods:
- Isolation of E. coli O111:H12 strains from fecal samples of children with diarrhea.
- Assessment of adherence patterns to HEp-2 cells and red blood cell agglutination.
- Screening for gene sequences homologous to known virulence factors using DNA probes.
- Evaluation of fluid accumulation in the rabbit ileal loop assay.
- Plasmid profiling of the studied strains.
Main Results:
- All seventeen E. coli O111:H12 strains displayed aggregative adherence to HEp-2 cells and mannose-dependent hemagglutination.
- These strains lacked gene sequences for aggregative adherence fimbria I and other tested virulence genes.
- Most strains (16/17) possessed the enteroaggregative E. coli heat-stable enterotoxin 1 (EAST) gene.
- The rabbit ileal loop assay was negative for fluid accumulation in all but one strain.
- A 60-70 MDa plasmid was identified in 16 of the strains.
Conclusions:
- The E. coli O111:H12 serotype, implicated in infantile diarrhea, fits the enteroaggregative E. coli category.
- The genetic mechanisms underlying the adherence phenotype of these strains are novel and distinct from previously described factors.
- These findings highlight the genetic diversity of virulence factors within enteroaggregative E. coli.
Abstract:
Seventeen Escherichia coli O111:H12 strains isolated from the feces of children with acute diarrhea were studied with regard to their adherence properties and other virulence characteristics. All strains showed an aggregative adherence pattern to HEp-2 cells and agglutinated bovine and sheep red cells in the presence of mannose. These strains did not have gene sequences homologous to the aggregative adherence fimbria I gene and did not react with any of the DNA probes used to detect other virulence genes in enteropathogens. With one exception, the O111:H12 strains did not induce fluid accumulation in the rabbit ileal loop assay, although 16 of the strains had the enteroaggregative E. coli heat-stable enterotoxin 1 (EAST) gene sequences. A 60-70 MDa plasmid was present in 16 of the strains studied. We conclude that the O111:H12 serotype, one of the first E. coli identified in infantile diarrhea, belongs to the enteroaggregative E. coli category but the genes encoding its adherence phenotype are distinct from those previously described.