title: Nontyphoidal Salmonella from human clinical cases, asymptomatic children, and raw retail meats in Yucatan, Mexico.
abstract: BACKGROUND
  We report the results of a 3-year Salmonella surveillance study of persons with diarrhea; asymptomatic children; and retail pork, poultry, and beef in Yucatan, Mexico.
  
  
  METHODS
  Isolates were characterized according to serotype, antimicrobial susceptibility, and genetic relatedness with pulsed-field gel electrophoresis.
  
  
  RESULTS
  Salmonella Typhimurium was the most common serotype found in ill humans (21.8% of isolates), followed by Salmonella Agona (21% of isolates). Salmonella Enteritidis was a minor serotype (4.2% of isolates). Asymptomatic children carried S. Agona (12.1% of isolates), Salmonella Meleagridis (11.6% of isolates), Salmonella Anatum (8% of isolates) and S. Enteritidis (5.8% of isolates). A high percentage of retail meat samples contained Salmonella; it was most commonly found in pork (58.1% of samples), followed by beef (54% of samples) and poultry (39.7% of samples). Resistance to oral drugs used for the treatment of salmonellosis was observed for ampicillin (14.6% of isolates were resistant), chloramphenicol (14.0% of isolates), and trimethoprim-sulfamethoxazole (19.7% of isolates). Resistance to ceftriaxone emerged in 2002 and was limited to the serotype S. Typhimurium. Twenty-seven percent of the isolates were resistant to nalidixic acid, and none were resistant to ciprofloxacin. Multidrug resistance was most common among isolates of serotypes S. Typhimurium and S. Anatum. Pulsed-field gel electrophoresis showed that strains found in retail meats were genetically identical to strains found in both asymptomatic children and ill patients.
  
  
  CONCLUSIONS
  Our study found a high prevalence of Salmonella in retail meats and persons with enteric infection; many of these isolates were resistant to clinically important antimicrobials. A random selection of isolates from people and retail meat showed genetic relatedness, which suggests that, in Yucatan, considerable transfer of Salmonella occurs through the food chain.
authors.affiliation: Laboratorio de Investigación, Hospital General O'Horan, Mérida, Yucatan, Mexico. mbzaidi@yuc.quik.com
authors.forename: Mussaret B
authors.initials: MB
authors.lastname: Zaidi
authors.forename: Patrick F
authors.initials: PF
authors.lastname: McDermott
authors.forename: Paula
authors.initials: P
authors.lastname: Fedorka-Cray
authors.forename: Verónica
authors.initials: V
authors.lastname: Leon
authors.forename: Claudia
authors.initials: C
authors.lastname: Canche
authors.forename: Susannah K
authors.initials: SK
authors.lastname: Hubert
authors.forename: Jason
authors.initials: J
authors.lastname: Abbott
authors.forename: Magda
authors.initials: M
authors.lastname: León
authors.forename: Shaohua
authors.initials: S
authors.lastname: Zhao
authors.forename: Marcia
authors.initials: M
authors.lastname: Headrick
authors.forename: Linda
authors.initials: L
authors.lastname: Tollefson
mesh_terms: D000293:Adolescent; D000328:Adult; D000818:Animals; D002417:Cattle; D002648:Child; D002675:Child, Preschool; D005516:Food Microbiology; D006801:Humans; D007223:Infant; D008460:Meat / Q000382:microbiology*; D008800:Mexico; D011200:Poultry; D015995:Prevalence; D012475:Salmonella / Q000302:isolation & purification*; D012478:Salmonella Food Poisoning / Q000453:epidemiology* / Q000382:microbiology*; D013552:Swine