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Journal of Clinical Microbiology, September 2009, p. 2970-2974, Vol. 47, No. 9
0095-1137/09/$08.00+0     doi:10.1128/JCM.00319-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.

Prevalence of CTX-M β-Lactamases in Philadelphia, Pennsylvania{triangledown}

Shannon E. McGettigan,1 Baofeng Hu,1,2 Kathleen Andreacchio,1 Irving Nachamkin,1,3 and Paul H. Edelstein1*

Department of Pathology and Laboratory Medicine,1 Center for Clinical Epidemiology and Biostatistics,2 Center for Education and Research on Therapeutics, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 191043

Received 12 February 2009/ Returned for modification 9 April 2009/ Accepted 2 July 2009

CTX-M β-lactamases were thought to be rare in the United States, but a recent study in Texas showed that up to 70% of extended-spectrum β-lactamase (ESBL)-containing members of the Enterobacteriaceae family were CTX-M positive (J. S. Lewis, M. Herrera, B. Wickes, J. E. Patterson, and J. H. Jorgensen, Antimicrob. Agents Chemother. 51:4015-4021, 2007). We used PCR to detect CTX-M in all 291 extended-spectrum cephalosporin-resistant gram-negative bacteria isolated in our laboratory during 2007. Thirty (48%) Escherichia coli isolates, 6 (3%) Klebsiella sp. isolates, and 7 (100%) Proteus mirabilis isolates tested were CTX-M positive, with 15% of all Enterobacteriaceae tested being positive. The E. coli CTX-M groups were I (57%), IV (37%), II (3%), and not groupable (3%); three of the group IV isolates were positive for CTX-M-18, and three of the group I isolates were positive for CTX-M-15. One of seven positive P. mirabilis isolates was in group II, with the remainder being positive for a CTX-M-25-like β-lactamase; and 33% of the Klebsiella sp. isolates were in group I or IV, with the remainder not being in groups I to IV. CTX-M-producing bacteria were isolated from urine (n = 13), blood (n = 13), wounds (n = 12), and the respiratory tract (n = 4). All 31 CTX-M-positive isolates tested for the presence of ESBL were confirmed to produce ESBLs by the use of tests recommended by the CLSI. Pulsed-field gel electrophoresis of the CTX-M-positive isolates showed that six P. mirabilis isolates were clonal and that there were seven different E. coli clusters. Five of seven P. mirabilis isolates were from blood cultures. The CLSI tests for the confirmation of ESBL production reliably detect these isolates if both cefotaxime and ceftazidime are tested, but only about half would be classified as a possible CTX-M producers on the basis of the antibiogram alone. A new panprimer set increases the ability to detect CTX-M-producing strains. CTX-M-positive bacteria are common in our geographic region, are often invasive, and, with the exception of P. mirabilis, are multiclonal.

* Corresponding author. Mailing address: Clinical Microbiology Laboratory, 4 Gates, Department of Pathology and Laboratory Medicine, Hospital of the University of Pennsylvania, 3400 Spruce St., Philadelphia, PA 19104-4283. Phone: (215) 662-6651. Fax: (215) 662-6655. E-mail: phe{at}mail.med.upenn.edu

{triangledown} Published ahead of print on 8 July 2009.

Journal of Clinical Microbiology, September 2009, p. 2970-2974, Vol. 47, No. 9
0095-1137/09/$08.00+0     doi:10.1128/JCM.00319-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Sidjabat, H. E., Paterson, D. L., Adams-Haduch, J. M., Ewan, L., Pasculle, A. W., Muto, C. A., Tian, G.-B., Doi, Y. (2009). Molecular Epidemiology of CTX-M-Producing Escherichia coli Isolates at a Tertiary Medical Center in Western Pennsylvania. Antimicrob. Agents Chemother. 53: 4733-4739 [Abstract] [Full Text]  


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