Quinolone resistance in Escherichia coli from Accra, Ghana

Abstract

Background: Antimicrobial resistance is under-documented and commensal Escherichia coli can be used as indicator organisms to study the resistance in the community. We sought to determine the prevalence of resistance to broad-spectrum antimicrobials with particular focus on the quinolones, which have recently been introduced in parts of Africa, including Ghana.

Results: Forty (13.7%) of 293 E. coli isolates evaluated were nalidixic acid-resistant. Thirteen (52%) of 2006 and 2007 isolates and 10 (66.7%) of 2008 isolates were also resistant to ciprofloxacin. All but one of the quinolone-resistant isolates were resistant to three or more other antimicrobial classes. Sequencing the quinolone-resistance determining regions of gyrA and parC, which encode quinolone targets, revealed that 28 quinolone-resistant E. coli harboured a substitution at position 83 of the gyrA gene product and 20 of these isolates had other gyrA and/or parC substitutions. Horizontally-acquired quinolone-resistance genes qnrB1, qnrB2, qnrS1 or qepA were detected in 12 of the isolates. In spite of considerable overall diversity among E. coli from Ghana, as evaluated by multilocus sequence typing, 15 quinolone-resistant E. coli belonged to sequence type complex 10. Five of these isolates carried qnrS1 alleles.

Conclusions: Quinolone-resistant E. coli are commonly present in the faecal flora of Accra residents. The isolates have evolved resistance through multiple mechanisms and belong to very few lineages, suggesting clonal expansion. Containment strategies to limit the spread of quinolone-resistant E. coli need to be deployed to conserve quinolone effectiveness and promote alternatives to their use.

Figure 1

Proportion of E. coli isolates resistant to each of eight broad-spectrum antibacterials in 2006, 2007 and 2008.

Figure 2

eBURST output for 165 E. coli isolates in the http://www.mlst.net database that were isolated in Ghana, including 48 isolates sequence-typed in this study. Each ST is marked as a dot or node. The size of the node is proportional to the number of isolates contained in that ST. Blue nodes represent predicted founder STs and sub-founders are indicated in yellow. All other STs marked as black dots. STs annotated in green are comprised of quinolone-resistant strains only and those written in pink contain quinolone-sensitive and quinolone-resistant isolates.