Molecular Detection of New SHV β-lactamase Variants in Clinical Escherichia coli and Klebsiella pneumoniae Isolates from Egypt.

The emergence of multidrug-resistant (MDR) pathogens was reported worldwide. Herein, SHV extended-spectrum β-lactamase (SHV-ESBL) variants detection was investigated in MDR E. coli and K. pneumoniae isolates recovered from human subjects (n = 144), one day-old chicks (n = 36) and broiler clinical samples (n = 90). All examined samples were positive for E. coli (n = 246/270; 91.11%) and Klebsiella pneumoniae (n = 24/270; 8.89%). Antimicrobial susceptibility testing was performed on E. coli and K. pneumoniae. SHV-ESBL producing isolates were defined followed by SHV-ESBL amino acids sequence and proteins structure-function analyses. Phylogenetic analysis of 11 MDR isolates resistant to at least 6 β-lactams was designed to determine their genetic relationship with those previously identified in Egypt. SHV-ESBL variants were detected in 28% and 16% of E. coli and K. pneumoniae isolates, respectively. Among the 11 SHV-ESBL producing isolates, one isolate displayed 100% blaSHV-12 similarity with three point mutations, while the other 10 isolates displayed amino acid substitutions at previously non-reported sites. Amino acid sequence analyses of these 10 isolates displayed 96-100% identity to blaSHV-10 (2 isolates with 3-6 point mutations), blaSHV-18 (one isolate with 4 point mutations), blaSHV-58 (4 isolates with 4-5 point mutations), and blaSHV-91 (3 isolates with 3-7 point mutations). These mutations altered SHV-enzyme pocket dimensions and its binding sites chargeability. The blaSHV phylogeny analysis revealed occurrence of variants in closely related lineages with blaSHV-5 and blaSHV-12 with possibility of blaSHV gene transfer between human and birds. The occurrence of these variants in Egypt could help in epidemiological studies and could explain the emergent resistance to β-lactams.
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