Relative enterotoxigenicity of coliform bacteria

Area of Science:

• Microbiology
• Gastroenterology
• Toxicology

Background:

• Coliform bacteria are common inhabitants of the gastrointestinal (GI) tract.
• Some coliforms can produce enterotoxins, contributing to diarrheal diseases.
• Understanding the source and potency of these toxins is crucial for diagnosing and treating GI infections.

Purpose of the Study:

• To determine and compare the enterotoxigenicity of coliform bacteria from human GI tracts versus urine cultures.
• To characterize the heat-labile (LT) and heat-stable (ST) toxins produced by these strains.
• To assess the quantitative differences in toxin potency between GI and genitourinary (GU) isolates.

Main Methods:

• Isolated coliform strains (Enterobacter cloacae, Klebsiella pneumoniae, Escherichia coli) from GI and urine samples.
• Separated heat-labile (LT) and heat-stable (ST) toxin fractions using ultrafiltration.
• Assessed toxin effects on water transport in rat jejunum via in vivo perfusion.
• Defined enterotoxigenic activity by the induction of net water secretion.

Main Results:

• All 12 GI strains produced one or both enterotoxins (LT and/or ST) with high potency (minimal effective concentration 0.1-10 ng/ml).
• Six of 13 GU strains elaborated enterotoxins, but these were of significantly weaker or intermediate potency.
• A millionfold quantitative difference in toxin potency was observed between GI and GU isolates.

Conclusions:

• Coliforms from the GI tract of individuals with diarrhea or tropical sprue are potent enterotoxin producers.
• Coliforms from urine cultures exhibit significantly lower enterotoxigenic potential.
• These findings highlight the distinct pathogenic capabilities of coliforms based on their origin and their role in diarrheal diseases.