Occurrence of class 1 integrons in uropathogenic fluoroquinolone-resistant clinical Escherichia coli isolates from Jamaica

摘要

Quinolone resistance is generally caused by chromosomal mutations, but has been more recently found associated with the plasmid-mediated qnr genes. The objective of this study was to screen and analyse polymorphisms of integrons in clinical isolates of Escherichia coli in Jamaica. Previous studies in Jamaica identified fluoroquinolone resistance in predominantly uropathogenic E. coli clinical isolates: 45% harbouring qnrA, qnrB and/or qnrS, and 17% were (Extended-spectrum beta-lactamase) ESBL-producers. These isolates were analysed for the presence and variation of class 1 and 2 integrase genes, 5′- and 3′- conserved segments and the Orf513 recombinase gene by primer-specific polymerase chain reaction (PCR) and restriction fragment-length polymorphism (RFLP). Results indicated integron-encoded integrases in 93% of isolates primarily harbouring class 1 integrase genes; four of 58 isolates carried both classes. The Orf513 and 5′- and 3′-conserved segment (CS) regions were identified in 83% and 55% of the isolates respectively. RFLP evaluation of the 5′- and 3′-CS regions in int1-positive strains yielded two main types. The reduced diversity, but wide dispersion of class 1 integrons harbouring qnr genes may give rise to the conservation of the mobile genetic elements in which they are carried.