Description of a new non-Tn4401 element (NTE-IIe) harboured on IncQ plasmid in Citrobacter werkmanii from recreational coastal water.

OBJECTIVES

Here we describe an IncQ1-like plasmid carrying bla in a new non-Tn4401 element found in Citrobacter werkmanii recovered from coastal water.

METHODS

In vitro and in silico approaches were used to assess antimicrobial resistance determinants, as well as bla vicinities.

RESULTS

The LB-887 isolate showed a multidrug-resistant phenotype and was identified as C. werkmanii. Resistome analysis identified further acquired resistance determinants to β-lactams, aminoglycosides, sulphonamides/trimethoprim, tetracyclines, chloramphenicol, macrolides, rifampicin and fluoroquinolones. Plasmidome included incompatibility groups IncA, IncC2, IncR, Col and IncQ families. The bla was inserted on a new variant of NTE-II, called here NTE-IIe, carried by an InQ1-like plasmid of 7930 kb (pKPC-LB887). NTE-IIe differed from NTE-IId by the complete absence of ISKpn6-tnpA. The InQ1-like backbone harbouring this element had been described in Enterobacterales recovered from clinical and environmental settings.

CONCLUSION

Unravelling genetic structures related to bla dissemination in different settings may provide clues on the main forces driving evolution of this important resistance determinant. Indeed, the occurrence of bla in a new NTE variant from an environmental source highlights the ongoing evolution of this mobile genetic element. In addition, bla carriage on a small and highly mobilizable IncQ plasmid in C. freundii complex from recreational water, similar to others found in clinical isolates, may suggest its relevance for bla dissemination among different compartments.