The 3' conserved segment of integrons contains a gene associated with multidrug resistance to antiseptics and disinfectants

Abstract

Nucleotide sequence analysis of ORF1 from the integron on the broad-host-range plasmid R751 revealed that the first 94 of 110 codons of ORF1 from R751 are identical to ORF4, an open reading frame from the 3' conserved segment of other integrons found in gram-negative bacteria, after which point they diverged completely. The predicted products of both ORFI and ORF4 share homology with the multidrug exporter QacC. Phenotypic analysis revealed that ORFI specifies a resistance profile to antiseptics and disinfectants almost identical to that of qacC, whereas ORF4 specifies much lower levels of resistance to these compounds. ORF4, whose product lacks the C-terminal 16 amino acids of the ORF1 protein, may have evolved by the interruption of ORF1 from the insertion of a DNA segment carrying a sufl sulfonamide resistance determinant. Hence, ORF1 was designated qacE, and its partially functional deletion derivative, ORF4, was designated qacEAI. Fluorimetric experiments indicated that the mechanism of resistance mediated by QacE, the protein specified by qacE, is active export energized by proton motive force. Amino acid sequence comparisons revealed that QacE is related to a family of small multidrug export proteins with four transmembrane segments.

Non‐palindromic attI sites of integrons are capable of site‐specific recombination with one another and with secondary targets

“…1B;Rå dströ m et al, 1994;Paulsen et al, 1993). The aadA1 cassette of Tn21 with surrounding sequences including attI and attC was cloned in pSU18 to yield plasmid 2123.…”

Novel Class 1 Integrons in Multi-drug Resistant Isolates from Eastern China

“…The 5 0 CS contains an integrase gene coding for site-specific integrase (intI) and a recombination site (attI) involving gene cassette site-specific recombination [6]. The 3 0 CS includes the truncated qacE and sul genes that encode resistance to quaternary ammonium compounds and sulfonamides, respectively [7]. The variable region consists of one or more gene cassettes captured by integron through site-specific recombination mechanism [6].…”

Inadequately Treated Wastewater as a Source of Human Enteric Viruses in the Environment

“…Similar findings were also noted by Ndi and Barton (2011) and Yu et al (2003). Since occurrence of sulfonamide resistance gene (sul1) and quaternary ammonium compounds resistance gene (qacEΔ1) is often associated with classic class 1 integrons (Paulsen et al 1993), in all intI1-positive isolates, presence of those genes was tested. In 25 isolates (29.76 %), sul1 gene was not detected, and in 23 of those isolates, we failed to amplify the variable regions.…”

“…Resistance to fluoroquinolones (ciprofloxacin and levofloxacin), trimethoprim/sulfamethoxazole, amoxicillin/clavulanate, and piperacillin/tazobactam was significantly associated with the presence of integrons (Fisher's exact test, P<0.05 for piperacillin/tazobactam, P <0.01 for the other abovementioned antibiotics). Presence of integrons together with STX resistance is not surprising, since occurrence of sulfonamide resistance gene (sul1) is often associated with classic class 1 integrons (Paulsen et al 1993). Correlation of other resistance with integrons is likely to the presence of numerous resistance genes in one genetic element, e.g., plasmids or transposons (Stalder et al 2012).…”

“…Additionally, the presence of sul1 and qacEΔ1 genes, which are usually associated with integrons (Stokes and Hall 1989;Paulsen et al 1993), was also checked. In order to determine the size of the variable gene cassette regions in integronpositive isolates, we used previously described primer sets 5CS-3CS and hepF-hepR (for class 1 and class 2 variable region, respectively) (Levesque et al 1995;White et al 2001).…”