An integron cassette encoding erythromycin esterase, ere(A), from Providencia stuartii

Area of Science:

• Microbiology
• Genetics
• Molecular Biology

Background:

• Multidrug resistance in bacteria is a growing global health concern.
• Integrons are genetic elements that play a crucial role in the acquisition and dissemination of antibiotic resistance genes.
• Class 1 integrons are commonly found in clinical settings and are associated with various resistance determinants.

Purpose of the Study:

• To characterize the genetic structure of two class 1 integrons identified in the multiresistant bacterial strain Providencia stuartii 1723.
• To determine the gene cassette arrangements within these integrons and identify the associated antibiotic resistance genes.
• To analyze the sequence of a specific gene cassette and compare it to known variants.

Main Methods:

• DNA sequencing of the variable regions of the two class 1 integrons.
• Bioinformatic analysis to identify gene cassettes and their arrangements.
• Sequence comparison of identified gene cassettes against existing databases.

Main Results:

• Integron 1 was found to contain a novel arrangement of gene cassettes: aacA4-aadB-aadA1. This combination confers resistance to all clinically relevant aminoglycoside antibiotics.
• Integron 2 contained a variant of the ere(A) gene cassette, encoding an erythromycin esterase.
• The nucleotide sequence of the ere(A) variant showed 93.7% DNA identity to the ere(A) gene from Escherichia coli BM2195 plasmid pIP1100.

Conclusions:

• The identified gene cassette arrangement in Integron 1 represents a new mechanism for conferring broad-spectrum aminoglycoside resistance.
• The variant ere(A) cassette in Integron 2 highlights the genetic diversity and evolution of antibiotic resistance genes.
• These findings contribute to understanding the genetic basis of multidrug resistance in Providencia stuartii and have implications for antimicrobial stewardship.