Incidence of Class 1 and 2 Integrases in Clinical and Commensal Bacteria from Livestock, Companion Animals, and Exotics

Abstract

Many pathogenic and commensal organisms are multidrug resistant due to exposure to various antibiotics. Often, this antimicrobial resistance is encoded by integrons that occur on plasmids or that are integrated into the bacterial chromosome. Integrons are commonly associated with bacterial genera in the family Enterobacteriaceae. We determined that class 1 integrases were present in approximately 46% of the isolates from the family Enterobacteriaceae; class 2 integrases were present only among Escherichia coli and Salmonella isolates. Seven percent of veterinary isolates were positive for class 3 integrase by DNA-DNA hybridization but could not be confirmed to be positive by PCR. None of the veterinary isolates possessed the class 4 integrase gene. The distribution of these integrase genes was variable within the members of the family Enterobacteriaceae when some or all integrase classes were absent from a particular genus. There was also considerable variability in the distribution of these integrases within a species, depending on the animal host. Unlike the class 1 integrases, the other integrase class, intI2, appears to be more restricted in its distribution among the members of the family Enterobacteriaceae. There is also considerable variability in the distribution of the class 1 integrases within E. coli strains isolated from different food animals. The class 1 integrases are the most widely disseminated of the four classes among the members of the family Enterobacteriaceae from both the clinical and normal flora of animals. This is the first report to closely examine the distribution of class 2 integrases in members of the family Enterobacteriaceae isolated in the United States.

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

“…Based on the encoded sequence of integrase, three classes of integron have so far been found associated with the mobilization of resistance genes [2]. Class 1 integrons are the most important and clinically relevant, with a wide distribution among bacteria species [4], whereas class 2 integrons are less common, and class 3 integrons few reported in clinical isolates [5].…”

“…Over the past decades, much work has been done on the epidemiology of integrons and their important roles in bacterial resistance in both clinical and natural environments [2,4,[8][9][10][11]. Surveillance of integrons therefore is essential for the investigation of MDR bacteria evolution.…”

Gram-positive bacteria are a major reservoir of Class 1 antibiotic resistance integrons in poultry litter

“…1 A) and 2 (Tn7-like; Fig. 1B) are most frequently found in bacteria that colonize food animals (16)(17)(18), in domesticated and wild birds (17), and in human clinical specimens (19,20). Although studied exclusively in the Enterobacteriaceae, Class 1 integrons have been seen fortuitously on three occasions in single strains of Gram-positive bacteria (21)(22)(23).…”

Response of activated sludge to the treatment of oxytetracycline production waste stream

“…Similarly, class 1 and 2 integrons (intI1 and intI2), transposon Tn916/1545, insertion sequence common region (ISCR1), bacterial 16S rRNA gene, and fungal 18S rRNA gene were also quantified. Primers and amplification conditions of all tested genes are listed in Table S1 ( Aminov et al 2001Aminov et al , 2002Goldstein et al 2001;Ng et al 2001;Roberts et al 2001;Koike et al 2007;Xia et al 2010;Prevost-Boure et al 2011).…”