Prevalent feature of complex class 1 integrons in drug-resistant bacteria isolated from aquaculture environment

Abstract:

[Objective] In order to understand the distribution and genomic characteristics of complex class 1 integron in aquaculture environment. [Methods] 108 strains of drug-resitstiant bacteria were isolated from aquaculture farms in Fujian province to check the carrying status of the upstream and downstream conserved and variable regions of the complex class 1 integron by PCR and sequencing. [Results] The results showed that 86 strains (79.6%) carried class 1 integrons and 47 strains (43.5%) carried ISCR1 elements. However, only 26 strains (24.1%) have both of the elements, of which 16 strains (14.8%) were successfully amplified upstream and downstream variable regions, involving 9 species, 8 genera. Furthermore, splicing and analysis of upstream and downstream sequences indicated that these 16 strains carried two types of complex class 1 integrons: (1) intI1-aac(6′)-Ib-cr-arr-3-dfrA27-aadA16-qacE△1-sul1-ISCR1-sdr-qnrB6-qacE△1-sul1(15 strains); intI1-aac(6′)-Ib-cr-arr-3-dfrA27-aadA16-qacE△1-sul1-ISCR1-sapA-like-qnrB2-qacE△1(truncated)-sul1 (only Klebsiella pneumoniae C12 strain), which is a noval structure of complex class 1 integron. [Conclusion] The complex class 1 integron is not infrequent in aquaculture environment and exists in various bacteria, yet its gene structure lacks diversity.