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Antimicrobial resistance, subtypes, and virulence in Salmonella from humans and swine

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Salmonella: important foodborne pathogen. ... Salmonella from humans are phenotypically and genotypically similar to those of ... – PowerPoint PPT presentation

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Title: Antimicrobial resistance, subtypes, and virulence in Salmonella from humans and swine


1
Antimicrobial resistance, subtypes, and virulence
in Salmonella from humans and swine
  • D. H. Coombs1, W.A. Gebreyes2, S. Thakur1
  • 1CVM, NCSU, Raleigh, NC. 2CVM, OSU, Columbus, OH.

2
Background
  • North Carolina second largest pork producing
    state in the U.S.
  • More than 10 million heads marketed per annum.
  • Human population 8.1 million.
  • Salmonella important foodborne pathogen.
  • Dissemination of antimicrobial resistance,
    particularly Multi-Drug Resistant (MDR).
  • Concern foodborne dissemination, environmental
    and occupational.

3
Hypothesis
  • Salmonella from humans are phenotypically and
    genotypically similar to those of swine origin,
    particularly in the major pork producing
    (eastern) part of the state.

4
Approaches
  • Comparison of antimicrobial resistance patterns
    between east (pig area) and west (no-pig area)
    among isolates from human
  • Comparison of antimicrobial resistance patterns
    between isolates from swine and human in the east
  • Diversity of genotypes among isolates from human
    and swine and between clinical and non-clinical
    settings
  • Identification of genes that may be responsible
    for similarities and differences among the two
    hosts (human and swine) and settings (clinical
    and non-clinical)

5
Methods
  • Isolates from human (NCSLPH)
  • 1038 clinical isolates included
  • Collected between 2000-2003.
  • Serotypes Typhimurium, Newport, Heidelberg and
    Muenchen
  • Isolates from swine (NCSU-CVM)
  • 1314 (1997-2000) and 559 (2002-2003) included.
  • Only 65 isolates were clinical.
  • 27 serotypes (predominantly Typhimurium, Typhim.
    Var. Copenhagen and Derby).

6
Methods
  • Antimicrobial susceptibility
  • Kirby-Bauer disc diffusion for 12 antimicrobials
    ampicillin (Am), chloramphenicol (Cm),
    streptomycin (St), sulfamethoxazole (Su),
    tetracycline (Te), amoxicillin/ clavulanic acid
    (Ax), amikacin (Ak), gentamicin (Gm), kanamycin
    (Km), cephalothin (Cf), ceftriaxone (Cro), and
    ciprofloxacin (Cip).
  • Epsilometric-test (confirmation of Cro).
  • NCCLS standards (M31-A2).
  • Genotyping
  • Pulsed-Field Gel Electrophoresis (PFGE)
  • PCR spvA gene profile
  • Statistical analysis chi-square

7
Human Isolates
8
Demographic Information
9
North Carolina Counties
West of I-95 East of
I-95 (Few Pigs)
(Many Pigs)
10
Serotypes of Human Isolates, by Geographic Origin
11
Resistance of Human Isolates from two
Geographical Areas
12
Frequency of antimicrobial resistance among
Salmonella
13
Genotyping of Isolates with MDR Patterns
Typhimurium
Human, Clinical
Swine, Non-clinical
Swine, Clinical
14
(No Transcript)
15
spvA gene among Swine MDR isolates
16
Summary of Findings
  • There was no evidence that the predominant
    Salmonella shed by asymptomatic pigs were
    phenotypically and/or genotypically linked to
    strains that cause illness in humans.
  • Frequency of antimicrobial resistance,
    particularly to tetracycline and ß-lactams (e.g.,
    ampicillin) was higher among isolates from swine
    than humans.
  • Swine (84 41) vs. humans (17 16)
  • Wider spectrum of resistance observed among
    isolates from humans.

17
Summary of Findings…
  • Clinical isolates from swine and humans were
    found to be genotypically similar.
  • The genotypic similarity of the disease causing
    Salmonella in swine and humans is an important
    finding.
  • Possibility that specific strains causing
    clinical illness in swine may also have the
    ability to make humans ill.
  • This was supported by the PFGE and occurrence of
    similar virulence gene markers.

18
Acknowledgements
  • NCSLPH
  • Leslie Wolf
  • Denise Briggs
  • NCSU-CVM
  • M. Suyemoto
  • C. Altier
  • Funding NCSU-CVM (intramural).
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