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Volume 17, Number 6—June 2011

Dispatch

Ciprofloxacin-Resistant Salmonella enterica Serotype Typhi, United States, 1999–2008

Felicita MedallaComments to Author , 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: 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); Massachusetts Department of Public Health, Jamaica Plain, Massachusetts, USA (E. Harvey)

Main Article

Table 1

MICs of antimicrobial agents tested for 9 ciprofloxacin-resistant Salmonella enterica serotype Typhi isolates detected in the National Antimicrobial Resistance Monitoring System, United States, 1999–2008

Antimicrobial class and agent* MIC, µg/mL,* by patient no. (isolate)
Patient 1 (MA-03) Patient 2† (CA-05) Patient 3 (CA-06) Patient 4 (TX-06) Patient 5 (AZ-06) Patient 6 (NY-07) Patient 7 (CA-07) Patient 8 (NJ-07) Patient 9 (LAC-07)
Quinolones
Ciprofloxacin >4 >4 >4 >4 >4 >4 >4 >4 >4
Nalidixic acid
>32
>32
>32
>32
>32
>32
>32
>32
>32
Aminoglycosides
Amikacin <0.5 1 1 1 1 1 1 1 1
Gentamicin <0.25 <0.25 <0.25 <0.25 <0.25 <0.25 <0.25 <0.25 <0.25
Kanamycin <8 <8 <8 <8 <8 <8 <8 <8 <8
Streptomycin
<32
<32
<32
>64
<32
<32
<32
<32
<32
β-lactam–β-lactamase inhibitor
Amoxicillin-clavulanic acid
<1/0.5
<1/0.5
<1/0.5
8/4
<1/0.5
<1/0.5
<1/0.5
<1/0.5
<1/0.5
Cephems
Cefoxitin 4 4 4 4 2 4 4 4 4
Ceftiofur 0.5 0.5 0.5 0.5 0.25 0.5 0.5 0.5 0.5
Ceftriaxone
<0.25
<0.25
<0.25
<0.25
<0.25
<0.25
<0.25
<0.25
<0.25
Folate pathway inhibitors
Sulfonamide‡ >512 >256 <16 >256 >256 <16 >256 <16 <16
Trimethoprim-
sulfamethoxazole
>4/76
>4/76
<0.12/ 2.38
>4/76
>4/76
<0.12/ 2.38
>4/76
<0.12/ 2.38
<0.12/ 2.38
Penicillins
Ampicillin
2
<1
<1
>32
<1
<1
<1
<1
<1
Phenicols
Chloramphenicol
4
4
4
>32
4
4
4
4
4
Tetracyclines
Tetracycline >32 >32 <4 <4 >32 <4 >32 <4 <4

*Classes of antimicrobial agents defined by the Clinical and Laboratory Standards Institute (CLSI) were used to categorize agents (7,13). MICs were interpreted by using CLSI criteria when available (7,13): ciprofloxacin (resistance breakpoint, >4 µg/mL); nalidixic acid (>32); amikacin (>64); gentamicin (>16); kanamycin (>64); amoxicillin-clavulanic acid (>32/16); cefoxitin (>32); ceftiofur (>8); ceftriaxone (>4); sulfamethoxazole/sulfisoxazole (>512); trimethoprim-sulfamethoxazole (>4/76); ampicillin (>32); chloramphenicol (>32); and tetracycline (>16). For streptomycin, resistance was defined as MIC >64 µg/mL (7). If growth was not inhibited by the highest concentration of the agent in the panel, the MIC was reported as above the highest concentration.
†Isolate was cultured from a blood specimen. Another isolate was cultured from fecal samples, which had MIC <0.5 µg/mL for amikacin and same MICs for other agents tested.
‡Sulfamethoxazole was used during 1999–2003 and sulfisoxazole since 2004 to represent sulfonamides.

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