The Prevalence of Integrons as the Carrier of Antibiotic Resistance Genes in Natural and Man-Made Environments

Abstract

Class 1 integrase intI1 has been considered as a good proxy for anthropogenic pollution because of being linked to genes conferring resistance to antibiotics. The gene cassettes of class 1 integrons could carry diverse antibiotic resistance genes (ARGs) and conduct horizontal gene transfer among microorganisms. The present study applied high-throughput sequencing technique combined with an intI1 database and genome assembly to quantify the abundance of intI1 in 64 environmental samples from 8 ecosystems, and to investigate the diverse arrangements of ARG-carrying gene cassettes (ACGCs) carried by class 1 integrons. The abundance of detected intI1 ranged from 3.83 × 10 to 4.26 × 10° intI1/cell. High correlation (Pearson's r = 0.852) between intI1 and ARG abundance indicated that intI1 could be considered as an important indicator of ARGs in environments. Aminoglycoside resistance genes were most frequently observed on gene cassettes, carried by 57% assembled ACGCs, followed by trimethoprim and beta-lactam resistance genes. This study established the pipeline for broad monitoring of intI1 in various environmental samples and scanning the ARGs carried by integrons. These findings supplemented our knowledge on the distribution of class 1 integrons and ARGs carried on mobile genetic elements, benefiting future studies on horizontal gene transfer of ARGs.

Multidrug resistance and high prevalence of class 1 integrons inEscherichia coliisolated from waters and vegetables in Nsukka and Enugu, Nigeria

“…It is known that AMR and MDR in E. coli are acquired by the transfer of mobile genetic elements, such as plasmids, transposons and integrons [15, 18, 20]. In the present study, of the 178 E. coli isolates, class 1 integrons were detected (Fig 2) in 175 (98.3%), and class 2 in 5 (2.8%).…”

“…Considering that all the isolates were MDR, the detected high prevalence of class 1 integron is not surprising and compares with a previous study that reported that MDR phenotypes were observed in 96.8% of the integron-positive isolates [35]. These rates portend serious public health risks as it is known that class 1 integron could carry diverse antibiotic resistance genes (ARGs) and conduct horizontal gene transfer among microorganisms [20].…”

“…Along with transposons and plasmids, integrons, genetic elements commonly found in bacterial genomes that allow efficient acquisition and expression of exogenous genes, are central in the dissemination of antibiotic resistance among Gram-negative bacteria [18,19]. Horizontal transfer of integrons have been shown to play important role in the spread and maintenance of antimicrobial resistance among strains of E. coli and ARB can be transferred across borders by human travelers, animal and insect vectors, agricultural products and surface water [15,20]. Not much is known about the risk factors in spreading across local borders.…”

Rapidly mitigating antibiotic resistant risks in chicken manure by Hermetia illucens bioconversion with intestinal microflora

“…Conversion by the non-sterile larvae was the most effective treatment to attenuate ARGs, followed by conversion by sterile larvae. For the integrin genes, which function to facilitate ARG gene flow (Ma et al, 2017), the absolute abundance of intI 1 and intI 2 was also significantly decreased in both the non-sterile and sterile larvae treatments, but occurred more slowly in the controls. The results demonstrated that BSF larvae effectively reduced the abundance of ARGs and integrin genes.…”

Metagenomic analysis of effects of oxytetracycline and copper on antibiotic resistance genes and associated pathogenic hosts in swine manure compost

“…The study also identi ed the presence of MGEs, including three important integrons and one transposon [45,46] (Fig. 3), which play important roles in the transfer and acquisition of ARGs in various microorganisms via HGT.…”