Genomic and antimicrobial resistance genes diversity in multidrug-resistant CTX-M-positive isolates of Escherichia coli at a health care facility in Jeddah.

BACKGROUND: Whole genome sequencing has revolutionized epidemiological investigations of multidrug-resistant pathogenic bacteria worldwide. Aim of this study was to perform comprehensive characterization of ESBL-positive isolates of Escherichia coli obtained from clinical samples at the King Abdulaziz University Hospital utilizing whole genome sequencing. METHODS: Isolates were identified by MALDI-TOF mass spectrometry. Genome sequencing was performed using a paired-end strategy on the MiSeq platform. RESULTS: Nineteen isolates were clustered into different clades in a phylogenetic tree based on single nucleotide polymorphisms in core genomes. Seventeen sequence types were identified in the extended-spectrum ß-lactamase (ESBL)-positive isolates, and 11 subtypes were identified based on distinct types of fimH alleles. Forty-one acquired resistance genes were found in the 19 genomes. The blaCTX-M-15 gene, which encodes ESBL, was found in 15 isolates and was the most predominant resistance gene. Other antimicrobial resistance genes (ARGs) found in the isolates were associated with resistance to tetracycline (tetA), aminoglycoside [aph(3″)-Ib, and aph(6)-Id], and sulfonamide (sul1, and sul2). Nonsynonymous chromosomal mutations in the housekeeping genes parC and gyrA were commonly found in several genomes. CONCLUSION: Several other ARGs were found in CTX-M-positive E. coli isolates confer resistance to clinically important antibiotics used to treat infections caused by Gram-negative bacteria.

Molecular characterization, antimicrobial resistance and clinico-bioinformatics approaches to address the problem of extended-spectrum ß-lactamase-producing Escherichia coli in western Saudi Arabia.

The goal of this study was to genotypically characterize extended-spectrum ß-lactamase-producing Escherichia coli isolates from the western region of Saudi Arabia and to identify active antibiotics against these isolates using phenotypic and molecular modeling. In total, 211 ESBL-producing E. coli isolates recovered from heterogeneous clinical specimens were identified by MALDI-TOF. Thirty-two sequence types (STs) were identified from a multilocus sequence typing (MLST) analysis of ESBL-producing E. coli, including a novel ST (ST8162). The most common ST in the Saudi and expatriate population was ST131, followed by ST38. All the isolates were multidrug resistant (MDR), and >95% of the isolates were resistant to third-generation (ceftriaxone and ceftazidime) and fourth-generation (cefepime) cephalosporins. The ESBL-positive E. coli isolates primarily harbored the blaCTX-M and blaTEM genes. No resistance was observed against the carbapenem antibiotic group. All the ESBL-producing E. coli isolates were observed to be susceptible to a ceftazidime/avibactam combination. Molecular interaction analyses of the docked complexes revealed the amino acid residues crucial for the binding of antibiotics and inhibitors to the modeled CTX-M-15 enzyme. Importantly, avibactam displayed the most robust interaction with CTX-M-15 among the tested inhibitors in the docked state (∆G = -6.6 kcal/mol). The binding free energy values for clavulanate, tazobactam and sulbactam were determined to be -5.7, -5.9 and -5.2 kcal/mol, respectively. Overall, the study concludes that 'ceftazidime along with avibactam' should be carefully used as a treatment option against only carbapenem-resistant MDR ESBL-producing E. coli in this region.