Detection of Novel GyrB Mutations Associated with <i>Escherichia coli </i>Clinical Isolates

DNA supercoiling and regulation of intrinsic β-lactamase in pathogenic Escherichia coli

This review addresses the involvement of DNA supercoiling in the development of virulence and antibiotic profiles for uropathogenic Escherichia coli and the emergence of new pathotypes such as strain ST131 (serotype O25:H4). The mechanism suggests a role for topoisomerase enzymes and associated mutations in altering the chromosomal supercoiling state and introducing the required DNA twists for expression of intrinsic β-lactamase by ampC and certain virulence factors. In Escherichia coli, constitutive hyperexpression of intrinsic ampC is associated with specific mutations in the promoter and attenuator regions. However, many reports have documented the involvement of slow growth interventions in the expression of intrinsic resistance determinants. There is evidence that a stationary phase transcriptional switch protein, "BolA," is involved in the expression of the intrinsic ampC gene under starvation conditions. The process involves changes in the activity of the enzyme "gyrase," which leads to a change in the chromosomal DNA topology. Consequently, the DNA is relaxed, and the expression of the bolA gene is upregulated. The evolution of the extraintestinal pathogenic E. coli strain ST131 has demonstrated successful adaptability to various stress conditions and conferred compensatory mutations that endowed the microbe with resistance to fluoroquinolones and β-lactams. The results of this study provided new insights into the evidence for the influence of DNA topology in the expression of virulence genes and various determinants of antibiotic resistance (e.g., the intrinsic ampC gene) in Escherichia coli pathotypes.

Characterization of previously identified novel DNA fragment associated with Pathogenicity Island III536 reveals new blaCTX-M gene

In the Kingdom of Bahrain a high percentage of extra-intestinal infectious diseases are reported as urinary tract infections UTIs. These UTIs are repeatedly diagnosed as multidrug resistant isolates. In a recent investigation, a novel DNA segment was identified in a UTI cefotaxime resistant Escherichia coli isolate. The DNA sequence was associated to pathogenicity island III₅₃₆ locus. The current work is investigating/elucidating the genomic context of the newly identified locus in the UTI isolate using Single Genome Specific Primer-PCR (SGSP-PCR) approach. The isolate was characterized and redefined as strain EC1091 (genotype: bla_TEM, bla_CTX-M, gyrB, chuA, yjaA, TSpE4.C2) and its novel genomic contents were found to acquire antibiotic resistance genes: bla_CTX-M and aac (3). The bla_CTX-M was found to be a new beta-lactamase allele with no significant BLASTN results in the National Center for Biotechnology Information (NCBI), but a protein PSI-BLAST against non-redundant database revealed a remote similarity to CTX-M proteins.