Occurrence and diversity of IncZ plasmids in Europe
Abstract
IncZ plasmids belong to the I-complex together with IncI1, IncI2, IncIγ, IncK1, IncK2 and IncB/O. The first IncZ plasmid was described in 1983. Later, seven additional distinct IncZ plasmid groups have been described. The most commonly used in silico plasmid typing scheme does not discriminate between the different plasmids within the IncK/B/O/Z group. The aim of this study was to investigate occurrence and diversity of IncZ plasmids in Europe. In this study 410 E. coli and Shigella sonnei isolates carrying IncK/B/O/Z replicons were collected in 10 European countries and Lebanon and subjected to short-read whole genome sequencing. The isolates originated from humans (n=124), poultry (n=233), pigs (n=28), dairy cattle (n=4), veal cattle (n=19) and environment (n=2). IncK/B/O/Z plasmids were further typed based on their RNAI sequence and categorized into IncK1, IncK2, IncB/O and IncZ plasmid incompatibility groups. Among the 410 isolates, IncZ was the most observed type within the IncK/B/O/Z plasmid group with 213 positive isolates (52%). IncZ plasmids carried a wide variety of genes conferring resistance to β-lactams, sulfonamides, aminoglycosides and colistin. The results indicate that human clinical samples have a significantly higher (p<0,001) occurrence of IncZ plasmids compared to carriage samples from humans. Additionally, a phylogenetic analysis based on the RNAI sequence suggests the existence of new clusters in addition to the previously described IncZ plasmid groups.
This study found a high occurrence of IncZ plasmids within the IncK/B/O/Z-harboring isolates from human and animal sources in Europe, carrying a wide variety of antimicrobial resistance genes. Additionally it revealed existence of potentially new IncZ plasmid types. In order to get more insight to this plasmid type, there is a need for a better typing and surveillance.