Risk assessment studies of E. coli host-vector systems.

Area of Science:

• Microbiology
• Genetics
• Environmental Health

Background:

• Escherichia coli K-12 survival and plasmid transfer in the gut are critical for risk assessment.
• Antibiotic resistance in coliforms is a growing public health concern.

Purpose of the Study:

• To evaluate the survival and plasmid transfer of E. coli K-12 in mammalian gut environments.
• To assess the prevalence of antibiotic-resistant coliforms in human and animal populations.

Main Methods:

• In vivo studies using mouse models to assess E. coli K-12 colonization and plasmid (pBR322) transfer.
• Analysis of spontaneous chromosomal mutations affecting E. coli K-12 competitiveness.
• Surveys of antibiotic resistance in coliforms from fecal samples of human and animal populations.

Main Results:

• E. coli K-12 demonstrated poor survival and minimal plasmid transfer in the human and mouse gut.
• Transferable plasmids showed reduced transfer rates in the gut environment.
• Spontaneous antibiotic-resistant mutants of E. coli K-12 were poor colonizers.
• Antibiotic selection did not enhance E. coli K-12 survival, indicating a selective disadvantage.
• High frequencies of antibiotic-resistant coliforms were observed, with higher percentages in hospitalized patient populations.

Conclusions:

• E. coli K-12 is unlikely to establish significant populations or transfer plasmids effectively in the gut.
• The prevalence of antibiotic-resistant coliforms, particularly in clinical settings, poses a considerable risk.
• Existing data on phage and bacterial frequencies are valuable for future risk assessments.