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Screening Foodstuffs for Class 1 Integrons and Gene Cassettes
Published on: June 19, 2015
Integron presence in a multiresistant Morganella morganii isolate
Laura Rojas1, Teresa Vinuesa, Fe Tubau
1Section of Microbiology, Department of Pathology and Experimental Therapeutics, Campus de Bellvitge, University of Barcelona, Barcelona, Spain.
Abstract:
A multiresistant strain of Morganella morganii was isolated from a patient affected by several severe pathologies. The isolate was found to be resistant to the following antimicrobials: ampicillin, nalidixic acid, cefalothin, cefoxitin, ceftriaxone, ciprofloxacin, chloramphenicol, streptomycin, erythromycin, gentamicin, novobiocin, penicillin, rifampicin, tetracycline and violet crystal. Mechanisms leading to this multiresistance were studied. Porins of M. morganii multiresistant and wild-type strains were analysed by sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and were characterised by their ability to form channels in planar black lipid bilayers. The channels formed by porins from multiresistant and susceptible strains suggested that the porins of the multiresistant strain were not responsible for resistance. A 6.6 kb plasmid (pML2003) was detected, isolated and studied. pML2003 included two integrons. Direct sequencing revealed that one of the integrons contained two cassettes, aminoglycoside adenyltransferase (aadB) and chloramphenicol acetyltransferase (catB3) conferring resistance to aminoglycosides and chloramphenicol, respectively. The second integron contained carbenicillinase (blaP1b) and adenyltransferase (aadA2), which confer resistance to beta-lactamases and streptomycin, respectively.
Insights
A multiresistant Morganella morganii strain
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- A multiresistant strain of Morganella morganii was isolated from a patient with severe pathologies.
- The isolate exhibited resistance to a wide range of antimicrobials, including beta-lactams, aminoglycosides, and tetracyclines.
Purpose of the Study:
- To investigate the mechanisms underlying the multidrug resistance in the isolated Morganella morganii strain.
- To identify genetic elements, such as plasmids and integrons, responsible for conferring antimicrobial resistance.
Main Methods:
- Analysis of porins using sodium dodecylsulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and black lipid bilayer experiments.
- Plasmid isolation and characterization, including detection and sequencing of integrons and gene cassettes.
- Direct sequencing of identified integrons to determine the genes responsible for resistance.
Main Results:
- Porin analysis indicated that porins were not the primary cause of multidrug resistance in this strain.
- A 6.6 kb plasmid, designated pML2003, was identified and found to contain two integrons.
- One integron harbored cassettes conferring resistance to aminoglycosides (aadB) and chloramphenicol (catB3).
- The second integron contained cassettes conferring resistance to beta-lactams (blaP1b) and streptomycin (aadA2).
Conclusions:
- The multidrug resistance in this Morganella morganii isolate is primarily mediated by a plasmid carrying two integrons.
- These integrons contain specific gene cassettes that confer resistance to clinically significant classes of antibiotics.
- Understanding these genetic mechanisms is crucial for managing infections caused by multiresistant bacteria.
