Association between dnd gene cluster and the DNA degradation phenotype of untypeable Escherichia coli strains

Chieng, Yeo Chew (2014) Association between dnd gene cluster and the DNA degradation phenotype of untypeable Escherichia coli strains. In: 21st Malaysian Society for Molecular Biology & Biotechnology (MSMBB) Annual Scientific Meeting, 01-03 October 2014, Monash University Malaysia.

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Abstract

Pulsed-field gel electrophoresis (PFGE) is generally accepted as the “gold standard” subtyping method for Escherichia coli. However, strains suffering from in-gel DNA degradation (probably due to presence of dnd operon) during PFGE run can impact on the molecular epidemiological data. Although DNA degradation is common in many different bacteria, studies reporting the association of the Dnd phenotype and genotype are still lacking. The objective of this study was thus to improve the typeability of E. coli and to determine the association between the presence of dnd gene cluster and the Dnd phenotype. We would also aim to determine whether the Dnd phenotype is associated with an inherent clonal trait. A total of 60 human and zoonotic E. coli strains including 12 strains with the Dnd phenotype (Dnd+) were studied. PCR detection of dndB-E genes of the 60 strains was carried out. PFGE was performed on XbaI-digested genomic DNA of Dnd+ strains with and without the addition of thiourea. There was a 100% improvement on the typeability of Dnd+ E. coli strains. Dnd phenotype was also observed in both clonal and genetically diverse E. coli strains. Nine out of the 12 Dnd+ E. coli strains shared indistinguishable PFGE profile. Another three Dnd+ strains were genetically diverse. The dndBCDE genes (dnd operon) were detected in all Dnd+ E. coli strains by PCR and association between the phenotype and genotype of DNA degradation was also found. The untypeable problem of Dnd+ strains should be overcome as all of the Dnd+ strains in this study were obtained from unhealthy hosts and their epidemiological data may be of clinical importance.

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