Emerg Infect DisEmerging Infect. DisEIDEmerging Infectious Diseases1080-60401080-6059Centers for Disease Control and Prevention17080579337308405-062910.3201/eid1202.050629Letters to the EditorLetterFluoroquinolone-resistant Salmonella sp. in CarcassesFluoroquinolone-resistant Salmonella sp. in CarcassesWangYu-Chih*YehKuang-Sheng†ChangChao-Chin*HsuanShih-Ling*ChenTer-Hsin*National Chung Hsing University, Taichung, Taiwan;Taipei Medical University, Taipei, TaiwanAddress for correspondence: Ter-Hsin Chen, The Graduate Institute of Veterinary Public Health, College of Veterinary Medicine, National Chung Hsing University, No. 250, Kuo Kuang Rd, Taichung 402, Taiwan; fax: 886-4-2285-2186; email: thc@mail.vm.nchu.edu.tw22006122351352Keywords: SalmonellafluoroquinoloneTaiwanletter

To the Editor: Fluoroquinolone (FQ)-resistant Salmonella has been isolated from patients in Taiwan (1–7). Recently, a report further indicated that several patients were infected with Salmonella enterica serovar Schwarzengrund with high-level FQ resistance (1). S. Schwarzengrund has never been isolated from food animals in Taiwan.

We report the isolation of FQ-resistant strains from pork and broiler carcasses sampled from 2000 to 2003: 27 in 2000, 3 in 2001, 4 in 2002, and 2 in 2003. These isolates made up 18.85% of the 191 Salmonella strains obtained from pork and broiler carcasses in the study period. Of these isolates, 16 FQ-resistant S. Schwarzengrund strains were further analyzed to elucidate the possible mechanism of FQ resistance. Ciprofloxacin MIC levels in these isolates ranged from 4 to 16 μg/mL, and all had high-level nalidixic acid resistance (>1,024 μg/mL). All of the 16 investigated strains displayed mutations possibly associated with high-level FQ resistance. The mutation sites included 2 sites (Ser83Phe and Asp87Gly) in the quinolone resistance–determining region (QRDR) of gyrA, 2 sites (Thr57Ser and Ser80Arg) in the QRDR of parC, and 1 site (Ser458Pro) in the QRDR of parE, respectively. Four strains had mutations in the QRDR of gyrA and parC only but not in the QRDR of parE (Table).

Characteristics of ciprofloxacin-resistant <italic>Salmonella enterica</italic> serovar Schwarzengrund strains from carcasses*†
Strain no.Origin*Year isolatedAntimicrobial drug resistance profileQuinolone MICs (μg/mL)
Substitutions in QRDR‡
NALFLUENRCIPgyrAparCparE
A5B, M2000CmSxtTc1,024512328Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
A16P, E2000ApCmNSxtTc2,048512328Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
A17P, E2000ApCmNSxtTc2,0485123216Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
A18P, E2000ApCmNSxtTc2,0485123216Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
A19P, E2000ApCmCnNSxtTc1,024512328Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
A20P, E2000ApCmNSxtTc2,048512328Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
A29B, S2000CmNSxtTc1,024512328Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
A36B, S2000ApCmSxtTc1,024512328Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
A41P, S2000ApCmCnNSxtTc1,0245123216Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
A45P, S2000ApCmNSxtTc1,0245123216Ser83Phe;
Asp87GlyThr57Ser;
Ser80Arg
A51P, S2000ApCmCnNSxtTc1,024512164Ser83Phe;
Asp87GlyThr57Ser;
Ser80Arg
A56B, M2000ApCmCnNSxtTc2,0485126416Ser83Phe;
Asp87GlyThr57Ser;
Ser80Arg
A61P, S2000CmSxtTc1,024512328Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
A62P, S2000ApCmCnSxtTc2,0485126416Ser83Phe;
Asp87GlyThr57Ser;
Ser80Arg
B16P, E2001ApCmCnCroTc2,0485123216Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro
B73P, N2003ApCmCnNSxtTc2,0485123216Ser83Phe;
Asp87GlyThr57Ser;
Ser80ArgSer458Pro

*QRDR, quinolone resistance–determining region; B, broiler; M, middle Taiwan; P, pork; E, east Taiwan; S, south Taiwan; N, north Taiwan.
†Antimicrobial agents are ampicillin (Ap), chloramphenicol (Cm), ciprofloxacin (CIP), enrofloxacin (ENR), flumequine (FLU), gentamicin (Cn), ceftriaxone (Cro), nalidixic acid (NAL),neomycin (N), trimethoprim/sulfamethoxazole (Sxt), and tetracycline (Tc).
‡No gyrB substitutions were detected.

In conclusion, high-level FQ resistance was detected in S. Schwarzengrund isolated from pork and chicken in Taiwan. Specific mutation sites of gyrA, parC, and parE were associated with high-level FQ resistance in all the isolates investigated. Our results warrant further investigation of the public health consequences of FQ use in food animals in Taiwan.

Suggested citation for this article: Wang Y-C, Yeh K-S, Chang C-C, Hsuan S-L, Chen T-H. Fluoroquinolone-resistant Salmonella sp. in carcasses [letter]. Emerg Infect Dis [serial on the Internet]. 2006 Feb [date cited]. http://dx.doi.org/10.3201/eid1202.050629

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