Dataset Information

Class 1 integron in staphylococci.

ABSTRACT: As a major concern in public health, methicillin-resistant staphylococci (MRS) still remains one of the most prevalent pathogens that cause nosocomial infections throughout the world and has been recently labeled as a "super bug" in antibiotic resistance. Thus, surveillance and investigation on antibiotic resistance mechanisms involved in clinical MRS strains may raise urgent necessity and utmost significance. As a novel antibiotic resistance mechanism, class 1 integron has been identified as a primary source of antimicrobial resistance genes in Gram-negative organisms. However, most available studies on integrons had been limited within Gram-negative microbes, little is known for clinical Gram-positive bacteria. Based on series studies of systematic integrons investigation in hundreds of staphylococci strains during 2001-2006, this review concentrated on the latest development of class 1 integron in MRS isolates, including summary of prevalence and occurrence of class 1 integron, analysis of correlation between integron and antibiotic resistance, further demonstration of the role integrons play as antibiotic determinants, as well as origin and evolution of integron-associated gene cassettes during this study period.

SUBMITTER: Xu Z

PROVIDER: S-EPMC3136644 | biostudies-literature | 2011 Nov

REPOSITORIES: biostudies-literature

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Publications

Class 1 integron in staphylococci.

Xu Zhenbo Z Li Lin L Shi Lei L Shirtliff Mark E ME

Molecular biology reports 20110122 8

As a major concern in public health, methicillin-resistant staphylococci (MRS) still remains one of the most prevalent pathogens that cause nosocomial infections throughout the world and has been recently labeled as a "super bug" in antibiotic resistance. Thus, surveillance and investigation on antibiotic resistance mechanisms involved in clinical MRS strains may raise urgent necessity and utmost significance. As a novel antibiotic resistance mechanism, class 1 integron has been identified as a ...[more]

PMID: 21258866

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Project description:Integrons are bacterial genetic elements able to capture and express genes contained within mobile gene cassettes. Gene cassettes are expressed via a Pc promoter and can be excised from or integrated into the integron by integrase IntI. Although the mechanisms of gene cassette integration and excision are well known, the kinetics and modes of gene cassette shuffling leading to new gene cassette arrays remain puzzling. It has been proposed that under antibiotic selective pressure, IntI-mediated rearrangements can generate integron variants in which a weakly expressed gene cassette moves closer to Pc, thus leading to higher-level resistance. To test this hypothesis, we used an integron with four gene cassettes, intI1-aac(6')-Ib-dfrA15-aadA1-catB9, and applied selective pressure with chloramphenicol, resistance to which is encoded by catB9. Experiments were performed with three different Pc variants corresponding to three IntI1 variants. All three integrases, even when not overexpressed, were able to bring catB9 closer to Pc via excision of the dfrA15 and aadA1 gene cassettes, allowing their host bacteria to adapt to antibiotic pressure and to grow at high chloramphenicol concentrations. Integrase IntI1(R32_H39), reported to have the highest recombination activity, was able, when overexpressed, to trigger multiple gene cassette rearrangements. Although we observed a wide variety of rearrangements with catB9 moving closer to Pc and leading to higher chloramphenicol resistance, "cut-and-paste" relocalization of catB9 to the first position was not detected. Our results suggest that gene cassette rearrangements via excision are probably less cost-effective than excision and integration of a distal gene cassette closer to Pc.Integrons are bacterial genetic elements able to capture and express gene cassettes. Gene cassettes are expressed via a Pc promoter; the closer they are to Pc, the more strongly they are expressed. Gene cassettes can be excised from or integrated into the integron by integrase IntI. The kinetics and modes of gene cassette shuffling, leading to new gene cassette arrays remain puzzling. We used an integron with 4 antibiotic resistance gene cassettes and applied selective pressure with the antibiotic for which resistance was encoded by cassette 4. All IntI variants were able to bring cassette 4 closer to Pc. Rearrangements occur via excision of the previous gene cassettes instead of cut-and-paste relocalization of the fourth gene cassette.

Dataset Information

Class 1 integron in staphylococci.

Publications

Class 1 integron in staphylococci.

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