Molecular Characterization of a Novel Integrative Conjugative Element ICEHpa1 in Haemophilus parasuis

Abstract

ICE<i>Hpa1</i> was identified in the genome of a serovar 8 <i>Haemophilus parasuis</i> ST288 isolate YHP170504 from a case of swine lower respiratory tract infection. The aim of the present study was to characterize the integrative conjugative element ICE<i>Hpa1</i> and its multiresistance region. Susceptibility testing was determined by broth microdilution and the complete ICE<i>Hpa1</i> was identified by WGS analysis. The full sequence of ICE<i>Hpa1</i> was analyzed with bioinformatic tools. The presence of ICE<i>Hpa1</i>, its circular intermediate and integration site were confirmed by PCR and sequence analysis. Transfer of ICE<i>Hpa1</i> was confirmed by conjugation. ICE<i>Hpa1</i> has a size of 68,922 bp with 37.42% GC content and harbors 81 genes responsible for replication and stabilization, transfer, integration, and accessory functions, as well as seven different resistance genes [<i>bla</i> _Rob- ₃, <i>tet</i>(B), <i>aphA1</i>, <i>strA</i>, <i>strB</i>, <i>aac(6)'-Ie-aph(2')-Ia</i>, and <i>sul2</i>]. Conjugation experiments showed that ICE<i>Hpa1</i> could be transferred to <i>H. parasuis</i> V43 with frequencies of 6.1 × 10^-6. This is the first time a multidrug-resistance ICE has been reported in <i>H. parasuis</i>. Seven different resistance genes were located on a novel integrative conjugative element ICE<i>Hpa1</i>, which suggests that the ICE<i>Hpa1</i> is capable of acquiring foreign genes and serving as a carrier for various resistance genes.