Antibiotic resistance in plague

The ability to resist many of the antibiotics used against plague has been found so far in only a single case of the disease in Madagascar. But because the same ability is present in other kinds of bacteria from a broad range of livestock, antibiotic resistance could potentially spread to other Yersinia pestis and also other bacterial pathogens.

In a paper published March 21 in the journal PLoS ONE, the authors say this possibility represents a significant public health concern.

Genetic ability to disable antibiotics, including multi-drug resistance (MDR) sequences, is carried on plasmids, small circles of DNA that are passed easily between bacteria. In this study, the same MDR plasmids found in the Y. pestis from Madagascar were also present in bacteria such as salmonella and E. coli found in retail samples of beef, pork, chicken, and turkey from several US states.

"What we've done is revealed a mechanism for the acquisition of multi-drug resistance in Y. pestis. Obviously, this is an event that might have serious human health consequences. But the sequencing work we've done has given us a way to monitor this plasmid in future," said senior author Jacques Ravel of The Institute for Genomic Research (TIGR) in Rockville, MD.

"The fact that we found a plasmid usually found in salmonella in Y. pestis is a big problem. It also raises a question about how this happened, how it went from one to the other."

MDR salmonella and E. coli have been found in droppings from wild geese, raising the possibility that wild animals might be able to spread MDR far beyond the livestock where it originated.

"When we identified the first Y. pestis strain resistant to multiple antibiotics, we warned that if this type of strain spreads or emerges again, it would pose a serious health problem," said co-author Elisabeth Carniel, head of the Yersinia Research Unit at the Institut Pasteur in Paris.

"The discovery that the multi-resistance plasmid acquired by the plague bacillus is widespread in environmental bacteria reinforces this warning."