Emerg Infect DisEmerging Infect. DisEIDEmerging Infectious Diseases1080-60401080-6059Centers for Disease Control and Prevention24751334401281113-157510.3201/eid2005.131575Letters to the EditorLetterCiprofloxacin-Resistant Salmonella enterica Serotype Kentucky Sequence Type 198S. enterica Serotype Kentucky ST198Rickert-HartmanReganFolsterJason P.Centers for Disease Control and Prevention, Atlanta, Georgia, USAAddress for correspondence: Jason P. Folster, Centers for Disease Control and Prevention, 1600 Clifton Rd NE, Mailstop G29, Atlanta, GA 30329, USA; email: gux8@cdc.gov52014205910911Related: MulveyMR , BoydDA , FinleyR , FakharuddinK , LangnerS , AllenV , Ciprofloxacin-resistant Salmonella enterica serovar Kentucky in Canada. Emerg Infect Dis. 2013;20:9991001 .10.3201/eid1906.121351Keywords: antimicrobial resistanceSalmonellaSalmonella enterica serotype Kentuckysalmonellaeciprofloxacinserotypebacteria

To the Editor: Mulvey et al. (1) reported the emergence of ciprofloxacin resistance in Salmonella enterica serovar Kentucky of multilocus sequence type 198 (ST198) in Canada (1). Ciprofloxacin resistance in S. enterica ser. Kentucky was reported in 2011 in patients from Europe, most of whom had traveled to Africa and the Middle East (2). Since then, S. enterica ser. Kentucky ST198 with additional resistance to third-generation cephalosporins and carbapenems has been reported from France and Morocco, again associated with travel (3). Poultry has been implicated as the most likely vehicle for infection by this sequence type (2,3). Resistance to third-generation cephalosporins and carbapenems has not been seen in North America; however, the emergence of ciprofloxacin-resistant infections has been observed (1).

In the United States, S. enterica ser. Kentucky is the most common serotype isolated from chickens and the second most common found among retail chicken, but ciprofloxacin resistance has not been documented among these sources (4). We sought to determine if ciprofloxacin- or ceftriaxone-resistant S. enterica ser. Kentucky has emerged in humans in the United States. We examined isolates and data from the National Antimicrobial Resistance Monitoring System to document antimicrobial resistance and sequence type and to assess possible risk factors for acquiring infection.

Participating state and local public health laboratories submit every 20th nontyphoidal Salmonella (NTS) isolate to the Centers for Disease Control and Prevention for susceptibility testing. MICs of >15 antimicrobial agents were determined by using broth microdilution (Sensititer, Cleveland, OH, USA) according to the manufacturer’s instructions. Where available, Clinical and Laboratory Standards Institute performance standards were used for interpretation of MICs; otherwise, interpretations established by the National Antimicrobial Resistance Monitoring System were used (5,6).

During 2009–2012, a total of 21 (0.2%) of the 9,225 NTS isolates tested were S. enterica ser. Kentucky. Six (29%) were resistant to ciprofloxacin; all were susceptible to ceftriaxone (Table) (5). As was observed in Canada, the 6 resistant isolates were >80% similar by pulsed-field gel electrophoresis analysis (XbaI; data not shown), and all 6 were ST198. Although a rare cause of human infection, S. enterica ser. Kentucky represented 23% (6/26) of all ciprofloxacin-resistant NTS detected during 2009–2012.

Patient and isolate information for 6 cases of infection with ciprofloxacin-resistant <italic>Salmonella enterica</italic> serotype Kentucky sequence type 198 detected by the National Antimicrobial Resistance Monitoring System, United States, 2009–2012*
Isolate IDPatient age, y/sexPatient racePatient travel historyYear specimen collectedSpecimen typeAntimicrobial resistance†
AM41047<1/FBlackEthiopia2009StoolAMP, FIS, GEN, NAL, STR, TET
AM4582054/FUnknownUnknown2010UrineAMP, COT, FIS, GEN, NAL, STR, TET
AM4705256/FAsianIndia2011UrineAMP, FIS, GEN, NAL, STR, TET
2012AM-10812/FAsianIndia2012StoolAMP, NAL
AM5077337/MAsianIndia2012StoolAMP, AUG, FIS, GEN, NAL, STR, TET
2012AM-035342/FWhiteSaudi Arabia2012UrineAMP, FIS, FOX, KAN, NAL, STR, TET

*ID, identification; AMP, ampicillin; AUG, amoxicillin-clavulanic acid; COT, trimethoprim-sulfamethoxazole; FIS, sulfisoxazole; FOX, cefoxitin; GEN, gentamicin; KAN, kanamycin; NAL, nalidixic acid; STR, streptomycin; TET, tetracycline.
†Resistance of isolate from infected patient to antimicrobial agents other than ciprofloxacin.

The median age of the 6 patients with ciprofloxacin-resistant S. enterica ser. Kentucky infections was 32 years (range 9 months–56 years); 5 (83%) were female. Of the 4 patients for whom information was available, 2 were hospitalized, and 1 died. Specimen sources were stool (n = 3) and urine (n = 3). Travel histories were obtained for 5 patients, and all had traveled internationally in the 7 days before specimen submission: 2 were residents of other countries (Saudi Arabia and Ethiopia), and 3 were US residents who had returned from travel to India. By comparison, only 3 of 10 patients with ciprofloxacin-susceptible infections had traveled (p = 0.02).

Resistance to ciprofloxacin in Salmonella is a growing concern because it limits treatment options for invasive disease. We describe ciprofloxacin-resistant S. enterica ser. Kentucky isolated from 6 patients in the United States. The emerging global story of S. enterica ser. Kentucky ST198 demonstrates the need for international integration of surveillance for antimicrobial drug resistance.

Suggested citation for this article: Rickert R, Folster JP. Ciprofloxacin-resistant Salmonella enterica serotype Kentucky sequence type 198 [letter]. Emerg Infect Dis [Internet]. 2014 May [date cited]. http://dx.doi.org/10.3201/eid2005.131575

ReferencesMulvey MR, Boyd DA, Finley R, Fakharuddin K, Langner S, Allen V, Ciprofloxacin-resistant Salmonella enterica serovar Kentucky in Canada. Emerg Infect Dis. 2013;19:9991001 . 10.3201/eid1906.12135123735312Le Hello S, Hendriksen RS, Doublet B, Fisher I, Nielsen EM, Whichard JM, International spread of an epidemic population of Salmonella enterica serotype Kentucky ST198 resistant to ciprofloxacin. J Infect Dis. 2011;204:67584 10.1093/infdis/jir40921813512Le Hello S, Harrios D, Bouchrif B, Sontag L, Elhani D, Guibert V, Highly drug-resistant Salmonella enterica serotype Kentucky ST198-X1: a microbiological study. Lancet Infect Dis. 2013;13:6729 10.1016/S1473-3099(13)70124-523721756US Food and Drug Administration. National Antimicrobial Resistance Monitoring System retail meat annual report, 2011 [cited 2013 Jul 1]. http://www.fda.gov/AnimalVeterinary/SafetyHealth/AntimicrobialResistance/NationalAntimicrobialResistanceMonitoringSystem/ucm334828.htmClinical and Laboratory Standards Institute. Performance standards for antimicrobial susceptibility testing; Twenty-third informational supplement. CLSI document M100–S23. Wayne (PA): The Institute; 2013Centers for Disease Control and Prevention. National Antimicrobial Resistance Monitoring System human isolates annual report, 2011 [cited 2013 Jul 1]. http://www.cdc.gov/narms/pdf/2011-annual-report-narms-508c.pdf