Phenotypic and Genotypic Characteristics for Escherichia coli strains responsible for bacterial bloom events in Australia
type: CreativeWork
description: Escherichia coli is widely used as an indicator of recent faecal contamination of drinking and recreational waters. However, evidence suggests that E. coli can proliferate in the environment outside a host, confounding its use as a faecal indicator. E. coli strains that produce significantly elevated counts of 10,000 - 100,000 cells/100 ml of water (bloom events) are reported from freshwater reservoirs and recreational lakes in Australia. Bloom strains are not faecal associated and may represent free-living E. coli. A limited number of strains are responsible for bloom events and all belong to E. coli phylogroups A and B1. Bloom strains have acquired a capsule originating from Klebsiella. Diversity and distribution of Klebsiella capsules in E. coli overall and in bloom strains were investigated. A PCR-based protocol was developed to detect capsule-positive E. coli and discriminate strains that harbour bloom strain-associated capsule types. Bloom strain attributes that could lead to the elevated cell densities observed in bloom events were experimented. The B1 bloom strain from the east coast (termed B1-001) which is numerically dominant and always present in bloom events was further characterised, and why B1-001 strain has not been detected in recent bloom events assessed using the Colilert-18 system was investigated. Frequency of Klebsiella capsules in E. coli was only 7% and 23 different Klebsiella capsule types were detected. All bloom strains were encapsulated and seven Klebsiella capsule types were detected among the eight bloom strains isolated to date. Capsules were observed only in strains from E. coli phylogroups A, B1, and C, and all encapsulated strains were of O-serogroups O8, O9, and O89. Capsule gene region and the adjacent O-antigen gene region in encapsulated E. coli are a result of a horizontal gene transfer event that occurred between E. coli and Klebsiella. The PCR accurately detected known bloom, non-bloom encapsulated, and capsule-negative strai…
abstract: Escherichia coli is widely used as an indicator of recent faecal contamination of drinking and recreational waters. However, evidence suggests that E. coli can proliferate in the environment outside a host, confounding its use as a faecal indicator. E. coli strains that produce significantly elevated counts of 10,000 - 100,000 cells/100 ml of water (bloom events) are reported from freshwater reservoirs and recreational lakes in Australia. Bloom strains are not faecal associated and may represent free-living E. coli. A limited number of strains are responsible for bloom events and all belong to E. coli phylogroups A and B1. Bloom strains have acquired a capsule originating from Klebsiella. Diversity and distribution of Klebsiella capsules in E. coli overall and in bloom strains were investigated. A PCR-based protocol was developed to detect capsule-positive E. coli and discriminate strains that harbour bloom strain-associated capsule types. Bloom strain attributes that could lead to the elevated cell densities observed in bloom events were experimented. The B1 bloom strain from the east coast (termed B1-001) which is numerically dominant and always present in bloom events was further characterised, and why B1-001 strain has not been detected in recent bloom events assessed using the Colilert-18 system was investigated. Frequency of Klebsiella capsules in E. coli was only 7% and 23 different Klebsiella capsule types were detected. All bloom strains were encapsulated and seven Klebsiella capsule types were detected among the eight bloom strains isolated to date. Capsules were observed only in strains from E. coli phylogroups A, B1, and C, and all encapsulated strains were of O-serogroups O8, O9, and O89. Capsule gene region and the adjacent O-antigen gene region in encapsulated E. coli are a result of a horizontal gene transfer event that occurred between E. coli and Klebsiella. The PCR accurately detected known bloom, non-bloom encapsulated, and capsule-negative strai…
author: Nanayakkara, Buddhie
language: en_AU
date published: 2019
date modified: 2026-07-24T01:07:16Z
provider: Australian Catholic University
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: Australian Catholic University

PropertyValue
property ID: Handle
value: http://hdl.handle.net/1885/173566