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Ciprofloxacin-Resistant S. enterica ser. Typhi | CDC EID

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Volume 17, Number 6–June 2011
Ciprofloxacin-Resistant Salmonella enterica Serotype Typhi, United States, 1999–2008
Felicita Medalla, Maria Sjölund-Karlsson, Sanghyuk Shin, Emily Harvey, Kevin Joyce, Lisa Theobald, Benjamin L. Nygren, Gary Pecic, Kathryn Gay, Jana Austin, Andrew Stuart, Elizabeth Blanton, Eric D. Mintz, Jean M. Whichard, and Ezra J. Barzilay
Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (F. Medalla, M. Sjölund-Karlsson, K. Joyce, L. Theobald, B.L. Nygren, G. Pecic, K. Gay, J. Austin, A. Stuart, E. Blanton, E.D. Mintz, J.M. Whichard, E.J. Barzilay); California Emerging Infections Program, Oakland, California, USA (S. Shin); and Massachusetts Department of Public Health, Jamaica Plain, Massachusetts, USA (E. Harvey)

Suggested citation for this article

We report 9 ciprofloxacin-resistant Salmonella enterica serotype Typhi isolates submitted to the US National Antimicrobial Resistance Monitoring System during 1999–2008. The first 2 had indistinguishable pulsed-field gel electrophoresis patterns and identical gyrA and parC mutations. Eight of the 9 patients had traveled to India within 30 days before illness onset.

Typhoid fever, caused by Salmonella enterica serotype Typhi, is a systemic bacterial illness that has been rare in the United States in the era of modern sanitation (1,2). However, typhoid fever remains common in many developing countries. In the United States, 72%–81% of patients with typhoid fever report international travel in the month before illness onset (1,3–5). Highest risk has been associated with travel to southern Asia (1–5).

Fluoroquinolones (e.g., ciprofloxacin) are frequently used to treat typhoid fever in adults (4,6). Ciprofloxacin resistance is rare; however, resistance to the quinolone nalidixic acid in the US National Antimicrobial Resistance Monitoring System (NARMS) increased from 19% of isolates tested in 1999 to 59% in 2008 (7). Nalidixic acid resistance in S. enterica serotype Typhi, which has been associated with overseas travel, particularly to southern Asia, correlates with decreased susceptibility to ciprofloxacin (MIC >0.12 μg/mL) (4–6,8). Increased risk for fluoroquinolone treatment failure has been demonstrated in Salmonella infections from strains with decreased susceptibility to ciprofloxacin (6,8,9). Chromosomal point mutations in the gyrA and parC topoisomerase genes are mechanisms of quinolone resistance in Salmonella spp. Other resistance mechanisms include efflux pumps, reduced outer membrane permeability, and plasmid-borne genes (e.g., qnr, aac-6′-Ib-cr genes) (6,8,10–12). We report 9 ciprofloxacin-resistant (MIC >4 μg/mL) S. enterica serotype Typhi isolates detected in the United States during 1999–2008.

Ciprofloxacin-Resistant S. enterica ser. Typhi | CDC EID

Suggested Citation for this Article
Medalla F, Sjölund-Karlsson M, Shin S, Harvey E, Joyce K, Theobald L, et al. Ciprofloxacin-resistant Salmonella enterica serotype Typhi, United States, 1999–2008. Emerg Infect Dis [serial on the Internet]. 2011 Jun [date cited].


DOI: 10.3201/eid1706.100594

Comments to the Authors
Please use the form below to submit correspondence to the authors or contact them at the following address:

Felicita Medalla, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, Mailstop D63, Atlanta, GA 30333, USA
; email: fmedalla@cdc.gov

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