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Antimicrobial Agents and Chemotherapy, July 2003, p. 2179-2185, Vol. 47, No. 7
0066-4804/03/$08.00+0     DOI: 10.1128/AAC.47.7.2179-2185.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

Survey of Plasmid-Associated Genetic Markers in Enterobacteriaceae with Reduced Susceptibilities to Cephalosporins

Karen E. Preston,1* Eileen M. Graffunder,2 Ann M. Evans,1 and Richard A. Venezia1

Departments of Laboratory Medicine,1 Epidemiology, Albany Medical Center Hospital, Albany, New York2

Received 16 December 2002/ Returned for modification 21 February 2003/ Accepted 21 April 2003

Clinical isolates of Enterobacteriaceae with reduced susceptibilities to cephalosporins were collected from 1993 to 2000. The organisms were screened for the extended-spectrum ß-lactamase (ESBL) phenotype, and plasmid extracts were screened for genetic markers by hybridization. A blaTEM probe was derived from pUC19; other probes were derived from pACM1, the plasmid responsible for the first known appearance of an ESBL in our institution. These probes included blaSHV, int, aac(3)-Ia, dfrA1, IS6100, tetA, IncM markers, and Anon 13, a marker for the Klebsiella pneumoniae chromosomal sequences that flank blaSHV-5. There were 42 hybridization patterns among 237 isolates. Patterns designated pACM1-like occurred in 44% of the isolates (eight species) and were always associated with the clavulanic acid (CA)-susceptible ESBL phenotype. The TEM marker was not predictive of the ESBL phenotype. Mapping indicated the presence of an SHV marker and up to 7.5 kb of its flanking chromosomal sequences in three non-IncM plasmids obtained in transformation experiments. We theorize that this DNA segment spread to other plasmids from pACM1-like sources. CA insensitivity became more frequent with time and was usually associated with either the TEM marker or the absence of both bla markers. One plasmid-encoded enzyme with characteristics of an AmpC ß-lactamase was observed in a transformant lacking both TEM and SHV markers. Although SHV type ESBLs were a continuing source of reduced susceptibility to cephalosporins in our institution, organisms with different resistance mechanisms were added to the hospital microflora in later years. These changes might be related, in part, to ESBL control strategies implemented in 1995.

* Corresponding author. Mailing address: MC 22, Albany Medical Center Hospital, 43 New Scotland Ave., Albany, NY 12208. Phone: (518) 262-4270. Fax: (518) 262-4337. E-mail: PrestoK{at}mail.amc.edu.

Antimicrobial Agents and Chemotherapy, July 2003, p. 2179-2185, Vol. 47, No. 7
0066-4804/03/$08.00+0     DOI: 10.1128/AAC.47.7.2179-2185.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Carattoli, A. (2009). Resistance Plasmid Families in Enterobacteriaceae. Antimicrob. Agents Chemother. 53: 2227-2238 [Full Text]  
  • Graffunder, E. M., Preston, K. E., Evans, A. M., Venezia, R. A. (2005). Risk factors associated with extended-spectrum {beta}-lactamase-producing organisms at a tertiary care hospital. J Antimicrob Chemother 56: 139-145 [Abstract] [Full Text]  
  • Machado, E., Canton, R., Baquero, F., Galan, J.-C., Rollan, A., Peixe, L., Coque, T. M. (2005). Integron Content of Extended-Spectrum-{beta}-Lactamase-Producing Escherichia coli Strains over 12 Years in a Single Hospital in Madrid, Spain. Antimicrob. Agents Chemother. 49: 1823-1829 [Abstract] [Full Text]  
  • Sherley, M., Gordon, D. M., Collignon, P. J. (2004). Evolution of multi-resistance plasmids in Australian clinical isolates of Escherichia coli. Microbiology 150: 1539-1546 [Abstract] [Full Text]  


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