New structures simultaneously harboring class 1 integron and ISCR1-linked resistance genes in multidrug-resistant...

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Complex class 1 integrons, also known as sul1-type integrons, are associated with numerous antibiotic resistance genes.
• These structures act as mobile gene-capturing systems, facilitating the spread of antibiotic resistance.
• Multidrug-resistant (MDR) Gram-negative bacteria pose a significant global health threat.

Purpose of the Study:

• To investigate the structural organization of class 1 integrons and insertion sequence common region 1 (ISCR1)-linked resistance genes in clinical MDR Gram-negative isolates.
• To characterize the connecting regions between these elements to understand their gene-capturing mechanisms.

Main Methods:

• Isolation of 63 MDR Gram-negative bacterial strains harboring both class 1 integron and ISCR1-linked resistance genes from 2309 clinical isolates.
• Utilized long-extension PCR and DNA sequencing to analyze the connecting regions between class 1 integrons and ISCR1.

Main Results:

• The study confirmed a serial connection between class 1 integron variable regions and ISCR1-linked resistance genes in all 63 isolates.
• Identified 12 distinct structural types based on the arrangement of resistance genes, with 8 novel types not previously reported.
• Observed similarities but also significant differences compared to previously described structures.

Conclusions:

• This research provides the first detailed structural analysis of simultaneously occurring class 1 integrons and ISCR1-linked resistance genes in a large cohort of MDR bacteria.
• The identified complex integron structures carrying diverse resistance genes are strongly associated with multidrug resistance in Gram-negative bacteria from Southern China.