CTX-M–producing Non-Typhi Salmonella spp., USA | CDC EID

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Volume 17, Number 1–January 2011
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CTX-M–producing Non-Typhi Salmonella spp. Isolated from Humans, United States

Maria Sjölund-Karlsson, Comments to Author Rebecca Howie, Amy Krueger, Regan Rickert, Gary Pecic, Kathryn Lupoli, Jason P. Folster, and Jean M. Whichard

Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (M. Sjölund-Karlsson, J.M. Whichard); and Atlanta Research and Education Foundation, Decatur, Georgia, USA (R. Howie, A. Krueger, R. Rickert, G. Pecic, K. Lupoli, J.P. Folster)

Suggested citation for this article

Abstract
CTX-M–type β-lactamases are increasing among US Enterobacteriaceae isolates. Of 2,165 non-Typhi Salmonella isolates submitted in 2007 to the National Antimicrobial Resistance Monitoring System, 100 (4.6%) displayed elevated MICs (>2 mg/L) of ceftriaxone or ceftiofur. Three isolates (serotypes Typhimurium, Concord, and I 4,5,12:i:–) contained blaCTX-M-5, blaCTX-M-15, and blaCTX-M-55/57, respectively.

Severe non-Typhi Salmonella (NTS) infections are commonly treated with fluoroquinolones such as ciprofloxacin or, in children, with extended-spectrum cephalosporins such as ceftriaxone. The emergence of Salmonella spp. isolates that display resistance to extended-spectrum cephalosporins is of increasing public health concern. In the United States, almost all resistance to extended-spectrum cephalosporins among Salmonella spp. isolates is caused by AmpC-type β-lactamases; extended-spectrum β-lactamases (ESBLs), including cefotaximases (CTX-M), rarely have been reported. Likewise, among other Enterobacteriaceae isolates in the United States, CTX-M enzymes have been considered rare until recently.

In 2007, Lewis et al. reported that CTX-M was the predominant ESBL among Enterobacteriaceae isolates in a US health care system (San Antonio, TX) (1). Among the ESBL-producing isolates collected, CTX-M enzymes increased in prevalence from 25% in 2002 to 70% in 2006. The emergence was observed mainly in urinary tract isolates of Escherichia coli, and the predominating enzyme was CTX-M-15 (1). Similarly, a US study investigating clinical samples of Enterobacteriaceae submitted to The Hospital of the University of Pennsylvania (Philadelphia, PA) in 2007 reported that 48% of cephalosporin-resistant E. coli isolates were CTX-M positive (2). Furthermore, CTX-M enzymes, and CTX-M-15 in particular, were common among ESBL-producing Enterobacteriaceae isolates collected at 15 US medical centers participating in the Meropenem Yearly Susceptibility Test Information Collection Program during 2007 (3).

In the United States, the National Antimicrobial Resistance Monitoring System (NARMS) has systematically monitored antimicrobial susceptibility of NTS since 1996. This program is a collaborative effort between the Centers for Disease Control and Prevention (CDC), the Food and Drug Administration, and the US Department of Agriculture. Reports on increased prevalence of CTX-M enzymes among Enterobacteriaceae isolates in the United States prompted us to investigate CTX-M enzymes among NARMS NTS isolates collected from humans in 2007.

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CTX-M–producing Non-Typhi Salmonella spp., USA | CDC EID


Suggested Citation for this Article

Sjölund-Karlsson M, Howie R, Krueger A, Rickert R, Pecic G, Lupoli K, et al. CTX-M–producing non-Typhi Salmonella spp. isolated from humans, United States. Emerg Infect Dis [serial on the Internet]. 2011 Jan [date cited].
http://www.cdc.gov/EID/content/17/1/97.htm

DOI: 10.3201/eid1701.100511

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Maria Sjölund-Karlsson, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, Mailstop G29, Atlanta, GA 30333, USA; email: fwt4@cdc.gov