Dissemination of nosocomial multiple-aminoglycoside-resistant Staphylococcus aureus caused by horizontal transfer of the resistance determinant (aacA/aphD) and clonal spread of resistant strains

  • Takezo Udou
    Reprint requests: Takezo Udou, PhD, Department of Clinical Microbiology, School of Health Sciences, University of Occupational and Envionmental Health, Yahatanishi-Ku, Kitakyushu 807-8555, Japan.
    From the University of Occupational and Environmental Health, Japan
    Search for articles by this author



      The multiple-aminoglycoside-resistant gene aacA/aphD exists as a transposable genetic element (Tn4001) in gram-positive cocci. Here we describe our retrospective investigation of the mechanism responsible for the dissemination of Tn4001 among staphylococci present in clinical isolates collected in our university hospital. At its peak, about 80% of the total isolates of methicillin-resistant Staphylococcus aureus showed multiple-aminoglycoside resistance, and all harbored aacA/aphD.


      Clonal relatedness was analyzed by pulsed field gel electrophoresis after SmaI endonuclease digestion of the genomic DNA from isolates collected in 1991 and 1997. To detect Tn4001 on the chromosome and conjugative plasmids, specific sequences from aacA/aphD and the insertion sequence IS256, whose inverted sequence flanks aacA/aphD, were amplified by polymerase chain reaction.


      Pulsed field gel electrophoresis of genomic DNA, plasmid analysis, and polymerase chain reaction detection of the resistance determinant all indicated the presence of disseminated clones that had survived among hospitalized patients through acquisition of conjugative plasmids harboring aacA/aphD. Futhermore, aacA/aphD also disseminated among nosocomial strains other than S aureus as a consequence of the self-transferability of Tn4001.


      The nosocomial prevalence of multiple-aminoglycoside-resistant staphylococci is the result of both horizontal and interspecific transfer of aacA/aphD and the clonal spread and survival of resistant strains.
      To read this article in full you will need to make a payment

      Purchase one-time access:

      Academic & Personal: 24 hour online accessCorporate R&D Professionals: 24 hour online access
      One-time access price info
      • For academic or personal research use, select 'Academic and Personal'
      • For corporate R&D use, select 'Corporate R&D Professionals'


      Subscribe to American Journal of Infection Control
      Already a print subscriber? Claim online access
      Already an online subscriber? Sign in
      Institutional Access: Sign in to ScienceDirect


        • Udou T
        Emergence of new-risk factors associated with nosocomial infection.
        J UOEH. 1998; 20: 361-368
        • Herwaldt L.A
        • Wenzel R.P
        Dynamics of hospital-acquired infection.
        in: Murray P.R Baron E.J Pfaller M.A Tenover F.C Yolken R.H Manual of clinical microbiology. 6th ed. ASM Press, Washington, DC1995: 169
        • Rice L.B
        Bacterial monopolists: the bundling and dissemination of antimicrobial resistance genes in gram-positive bacteria.
        Clin Infect Dis. 2000; 31: 762-769
        • Tanabe T
        • Udou T
        Molecular epidemiologic analysis of plasmids in clinical isolates of methicillin-resistant Staphylococcus aureus.
        J Jpn Soc Environ Infect. 1995; 10: 18-22
        • Lyon B.R
        • May J.W
        • Skurray R.A
        Analysis of plasmids in nosocomial strains of multiple-antibiotic-resistant Staphylococcus aureus.
        Antimicrob Agents Chemother. 1983; 23: 817-823
        • Udou T
        Functional characterization of a multiple-antibiotic resistant plasmid from clinical isolates of methicillin-resistant Staphylococcus aureus.
        J Jpn Assoc Infect Dis. 2001; 75: 382-389
        • Lyon B.R
        • May J.W
        • Skurry R.A
        Tn4001: a gentamicin and kanamycin resistance transposon in Staphylococcus aureus.
        Mol Gen Genet. 1984; 193: 554-556
        • Lipsitch M
        • Bergstrom C.T
        • Levin B.R
        The epidemiology of antibiotic resistance in hospitals: paradoxes and prescriptions.
        Proc Natl Acad Sci USA. 2000; 97: 1938-1943
        • Graffunder E.M
        • Venezia R.A
        Risk factors associated with nosocomial methicillin-resistant Staphylococcus aureus (MRSA) infection, including previous use of antimicrobials.
        J Antimicrob Chemother. 2002; 49: 999-1005
        • Paterson D.L
        Looking for risk factors for acquisition of antibiotic resistance: a 21st-century approach.
        Clin Infect Dis. 2002; 34: 1564-1567
        • Gentry C
        • Flournoy D.J
        • Reinert R.R
        Analysis of antimicrobial resistance among gram-negative bacilli and antimicrobial use in intensive care unit patients for 5 years in a Veterans Affairs medical center.
        Am J Infect Control. 2002; 30: 411-416
        • Murakami K
        • Minamide W
        PCR identification of methicillin-resistant Staphylococcus aureus.
        in: Persing D.H Smith T.F Tenover F.C White T.J Diagnostic molecular microbiology: principles and application. ASM Press, Washington, DC1993: 539
        • Kreiswirth B.N
        • Lofdahl S
        • Betley M.J
        • O'Reilly M
        • Schlievert P.M
        • Bergdoll M.S
        • et al.
        The toxic shock syndrome exotoxin structural gene is not detectably transmitted by a prophage.
        Nature. 1983; 305: 709-712
        • National Committee for Clinical Laboratory Standards
        Methods for dilution antimicrobial susceptibility tests for bacteria that grow aerobically: approved standard.
        in: NCCLS document M. 2nd ed (7-A3). National Committee for Clinical Laboratory Standards, Villanova (PA)1999
        • Dyke K.G.H
        • Aubert S
        • El Solh N
        Multiple copies of IS256 in staphylococci.
        Plasmid. 1992; 28: 235-246
        • Marmur J
        A procedure for the isolation of DNA from micro-organisms.
        J Mol Biol. 1961; 3: 208-218
        • Maslow J.N
        • Slutsky A.M
        • Arbeit R.D
        Application of pulsed-field gel electrophoresis to molecular epidemiology.
        in: Persing D.H Smith T.F Tenover F.C White T.J Diagnostic molecular microbiology: principles and application. ASM Press, Washington, DC1993: 563
        • Tenover F.C
        • Arbeit R.D
        • Goering R.V
        • Mickelsen P.A
        • Murray B.E
        • Persing D.H
        • et al.
        Interpreting chromosomal DNA restriction patterns produced by pulsed-field gel electrophoresis: criteria for bacterial strain typing.
        J Clin Microbiol. 1995; 33: 2233-2239
        • Casetta A
        • Hoi A.B
        • De Cespedes G
        • Horaud T
        Diversity of structures carrying the high-level gentamicin resistance gene (aac6-aph2) in Enterococcus faecalis strains isolated in France.
        Antimicrob Agents Chemother. 1998; 42: 2889-2892