Abstract
Objective To investigate the molecular epidemiology and mechanisms of carbapenem resistance of Morganella morganii.Methods Seven carbapenem-non-susceptible M.morganii were isolated from Hangzhou Traditional Chinese Medicine Hospital from October 2010 to February 2011.Pulsed-field gel electrophoresis (PFGE) was performed to analysis the molecular epidemiology of isolates.Antibiotic susceptibilities were determined by agar dilution method.Conjugation experiments were carried out in mixed broth cultures.Plasmid DNA was obtained by an alkalinelysis technique and examined by electrophoresis.Specific PCRs and DNA sequencing were preformed to confirm the genotype of β-lactamases.Results PFGE indicated that 6 M.morganii isolates from emergency care unit were indistinguishable or closely related and 1 isolate from intensive care unit was distinguishable.Seven M.morganii showed similar antibiotic susceptibility patterns.M.morganii isolates were resistant to imipenem,were susceptible to meropenem,and were susceptible or intermediate resistant to ertapenem,with MICs of 8 μg/ml,1 μg/ml,and 0.25-0.50 μg/ml,respectively.M.morganii isolates were resistant to penicillins,aztreonam,and ciprofloxacin,were resistant or susceptible to cephalosporins,and were susceptible to amikacin.E.coli (EC600) acquired an approximately 60 kb plasmid from M.morganii by conjugation studies and resistant or intermediate resistant to carbapenems and other β-lactams.PCRs and DNA sequence analysis confirmed that all M.morganii isolates and their E. coli transconjugants produced the KPC-2 carbapenemase and carried the qnrS1 gene.Conclusion It is the first detection of KPC-2 in M.morganii isolates.Production of KPC-2 mainly contributed to the carbapenem resistance in M.morganii. Key words: Morganella morganii; Carbapenems; Antibiotic resistance; Klebsiella pneumoniae carbapenemase
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