Diversity of pulsed-field gel electrophoresis pulsotypes, serovars, and antibiotic resistance among Salmonella isolates from wild amphibians and reptiles in the California Central Coast

Foodborne Pathog Dis. 2013 Jun;10(6):540-8. doi: 10.1089/fpd.2012.1372. Epub 2013 Apr 11.

Abstract

A survey of cold-blooded vertebrates and associated surface waters in a produce-growing region on the Central California Coast was done between May and September 2011 to determine the diversity of Salmonella. Samples from 460 amphibians and reptiles and 119 water samples were collected and cultured for Salmonella. Animals sampled were frogs (n=331), lizards (n=59), newts (n=5), salamanders (n=6), snakes (n=39), and toads (n=20). Salmonella was isolated from 37 individual animals, including frogs, lizards, snakes, and toads. Snakes were the most likely to contain Salmonella, with 59% testing positive followed by 15.3% of lizards, 5% of toads, and 1.2% of frogs. Fifteen water samples (12.6%) were positive. Twenty-two different serovars were identified, and the majority of isolates were S. enterica subsp. IIIb, with subsp. I, II, and IIIa also found. The serovar isolated most frequently was S. enterica subsp. IIIb 16:z₁₀:e,n,x,z₁₅, from snakes and frogs in five different locations. S. enterica subsp. I serovar Typhimurium and the monophasic I 6,8:d:- were isolated from water, and subspecies I Duisburg and its variants were found in animals and water. Some samples contained more than one type of Salmonella. Analysis of pulsed-field gel electrophoresis pulsotypes indicated that some strains persisted in animals and water collected from the same location. Sixty-six isolates displayed antibiotic resistance, with 27 isolates resistant to more than one antibiotic, including a subspecies IIIb isolate from snake having resistance to five different antibiotics. Twenty-three isolates were resistant to more than one class of antibiotic, and six isolates were resistant to three classes. While these subspecies of IIIa and IIIb cause fewer instances of human illness, they may serve as reservoirs of antibiotic resistance, determinants in the environment, and be sources of contamination of leafy greens associated with product recalls.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Agriculture
  • Amphibians / growth & development
  • Amphibians / microbiology*
  • Animals
  • Anti-Bacterial Agents / pharmacology*
  • California
  • Disease Reservoirs
  • Drug Resistance, Bacterial*
  • Drug Resistance, Multiple, Bacterial
  • Electrophoresis, Gel, Pulsed-Field
  • Environmental Monitoring
  • Humans
  • Molecular Typing
  • Reptiles / growth & development
  • Reptiles / microbiology*
  • Salmonella / classification
  • Salmonella / drug effects*
  • Salmonella / growth & development*
  • Salmonella / isolation & purification
  • Salmonella Infections / microbiology
  • Salmonella arizonae / classification
  • Salmonella arizonae / drug effects
  • Salmonella arizonae / growth & development
  • Salmonella arizonae / isolation & purification
  • Salmonella enterica / classification
  • Salmonella enterica / drug effects
  • Salmonella enterica / growth & development
  • Salmonella enterica / isolation & purification
  • Salmonella typhimurium / classification
  • Salmonella typhimurium / drug effects
  • Salmonella typhimurium / growth & development
  • Salmonella typhimurium / isolation & purification
  • Vegetables / growth & development
  • Vegetables / microbiology
  • Water Microbiology
  • Wetlands

Substances

  • Anti-Bacterial Agents