Temporal appearance of plasmid-mediated quinolone resistance genes

Area of Science:

• Microbiology
• Molecular Biology
• Genetics

Background:

• Quinolone antibiotics are crucial for treating gram-negative bacterial infections.
• The emergence of plasmid-mediated quinolone resistance (PMQR) genes poses a significant threat to antimicrobial therapy.
• The aac(6')-Ib-cr variant and qnr genes are common PMQR determinants.

Purpose of the Study:

• To investigate the prevalence of specific PMQR genes, including the aac(6')-Ib-cr variant, in historical gram-negative isolates.
• To determine the earliest occurrence of PMQR genes in clinical isolates from 1981 to 1991.

Main Methods:

• One hundred fifty AAC(6')-Ib-positive gram-negative bacterial isolates collected between 1981 and 1991 were analyzed.
• Polymerase chain reaction (PCR) was employed to detect the presence of aac(6')-Ib-cr, qnrA, qnrS, qnrC, qepA, and qnrB genes.

Main Results:

• None of the isolates harbored the aac(6')-Ib-cr variant, qnrA, qnrS, qnrC, or qepA genes.
• Two gram-negative strains isolated in 1988 were found to possess qnrB alleles.
• These qnrB-positive strains represent the earliest identified instances of PMQR genes in the studied collection.

Conclusions:

• The studied collection of AAC(6')-Ib-positive gram-negative isolates from 1981-1991 did not carry prevalent PMQR genes like aac(6')-Ib-cr or qnrA/S/C/qepA.
• The identification of qnrB alleles in 1988 isolates provides crucial historical data on the early emergence of PMQR genes.
• This finding highlights the importance of historical surveillance for understanding the evolution and spread of antimicrobial resistance.