1. No evidence of plasmid-mediated antibiotic resistance in North American Yersinia pestis
David M. Wagner1, Janelle Runberg1, Amy J. Vogler1, Judy Lee1, Lance B. Price2, David M. Engelthaler2, Jacques Ravel3, & Paul Keim1
1Northern Arizona University, Flagstaff, AZ; 2Translational Genomics Research Institute (TGen), Flagstaff, AZ; 3University of Maryland School of Medicine, Baltimore, MD

2. Plague Transmission Cycle
Wild Rodent Cycle
Secondary
plague
pneumonia
Wild
Rodent
Direct contact
Bubonic
or Septicemic
plague
Primary
pneumonic
plague
cases
Infective
Infective
Flea
Direct contact
contaminated soil
Flea
contact
Direct
Infective
Flea
Domestic
Rodent
Wild
Rodent
Pathways
Infective
usual
Flea
Domestic
occasional
Rodent
Commensal Rat Cycle
rare or
theoretical
Slide courtesy of Ken Gage

3. Three Plague Pandemics – 200 Million Deaths
Perry & Fetherston 1997
Achtman et al. 1999

4. Control of Plague – Hygiene & Antibiotics
Kill or eliminate habitat for rat hosts – very important in urban areas
Control flea vectors using insecticides
Rapid diagnosis, followed by
Standard treatment with antibiotics
Streptomycin
Tetracyclines
Sulfonamides

5. Plague Today – Global Distribution
Stenseth et al PLoS Medicine

6. Plague Today – Increases in Africa
Stenseth et al PLoS Medicine

7. Plague Today – Increases in Africa
Stenseth et al PLoS Medicine

8. Plague Vaccines – Little Success to Date
Killed vaccine no longer available in the US
Live attenuated vaccine not licensed for humans
Injected subunit vaccines show promise for future
As a result, efforts to save human lives are still focused on rapid diagnosis followed by treatment with antibiotics
Resistance to antibiotics could represent a serious threat to human health given high pathogenicity and ability to rapidly spread under optimal conditions

9. Antimicrobial Resistance in Y. pestis
Strain
17/95
16/95
Streptomycin Resistance
YES
Tetracycline Resistance NO
Sulfonamide Resistance
Other Resistance
Country of Origin
Madagascar
Year of Isolation
1995
Resistance Plasmid
pIP1202
pIP1203
Galimand et al New England Journal of Medicine

10. Typical and Atypical Plasmids in Y. pestis
Three main plasmids, all associated w/ virulence:
pCD1 (found in all pathogenic Yersinia)
pPCP1
pMT1
pMT1 very similar to plasmid in Salmonella enterica Serovar Typhi
Several different studies have documented atypical plasmids present in Y. pestis strains
Indicates that this species readily acquires plasmids
Filippov et al. 1990; Parkhill et al ; Prentice et al. 2001

11. Plasmid Acquisition Likely Occurs in Fleas
In co-infected fleas, E. coli donated pIP1202 to Y. pestis at frequency of 10-3 after three days
After four weeks, 95% of co-infected fleas contained MDR Y. pestis (Hinnebusch et al. 2002)
Y. pestis infected fleas can harbor diverse bacterial communities (Wagner et al. unpubl.)
Y. pestis infected fleas commonly co-infected with Salmonella spp. (Eskey et al. 1951)
What do we know about MDR plasmids in Y. pestis?

12. Plasmid pIP1202 from Y. pestis
Similar to MDR plasmids from Y. ruckeri and S. enterica Newport
All share the same plasmid backbone (IncA/C)
Backbone contains gene conferring resistance to sulfonamides (sul2)
Other resistance genes vary
Welch et al PLoS One

13. Similar MDR Plasmids in US Meat Products
Plasmids with similar IncA/C backbones and varying MDR profiles found in bacteria recovered from meat
Sources: turkey, chicken, beef, pork
States: CA, CO, CT, GA, IA, MD, MN, ND, NM, NY, TN, and OR
Hosts: S. enterica Typhimurium, Newport, Kentucky, Heidelberg, Dublin, Bredeney, Klebsiella spp., E. coli
Most resistant to tetracycline and many resistant to streptomycin and others, in addition to sulfonamides
Many strains readily transferred plasmids to Y. ruckeri
Welch et al PLoS One

14. No Evidence in North American Y. pestis
State N
Years
Arizona
151
1975, , , , 1998,
California
129
1943, 1962, 1970, 1977, ,
Colorado 97
1963, 1968, 1989, 1992, ,
Idaho 2
1987, 1997
Kansas 17
1997, 1999
Montana 11
1987,
North Dakota
1986, 1993
New Mexico
124
1950, , , , ,
Nevada 36
, 1987,
Oregon 18
1959, , 1977, 1979, , 1987
Texas 5
unknown
Utah 55
1965, , ,
Washington
1984
Wyoming 64
1978, 1980, , , , 1997,

15. Discussion/Conclusions
No IncA/C plasmid-mediated MDR in North American Y. pestis – why?
Our isolates mostly from human plague investigations
MDR resistant plasmids in meats probably arose in Concentrated Animal Feeding Operations (CAFOs)
Plague limited to 17 westernmost states, whereas most CAFOs in the eastern states
Plausible that MDR Y. pestis could arise in fleas co-infected with MDR enteric pathogens and Y. pestis
However, no obvious selection pressure to maintain these MDR plasmids in Y. pestis

16. Acknowledgements
Funding: NIH-NIAID, NIH Pacific-Southwest Regional Center of Excellence, Arizona Game & Fish, NAU-Cowden Endowment
CDC-Ft. Collins: Ken Gage, Becky Eisen, Jeannine Petersen, Marty Schriefer, Michael Kosoy
Arizona Department of Health Services: Craig Levy
Coconino County Health Department: Marlene Gaither
NAU Y. pestis Group: Amy Vogler, Becky Colman, Joe Busch, Judy Lee, Adina Doyle, Roxanne Nera