The plague bacterium could easily develop drug-resistance and become a major health threat, warn scientists.
A study, published this week (21 March) in PLoS ONE, found that the drug-resistance genes in a plague bacterium from a 1995 case of the disease were the same as those in many common bacteria and are able to 'jump' from bacteria to bacteria.
The researchers say this illustrates how easily Yersinia pestis — the bacterium causing plague — can develop resistance to antibiotics, which are vital in the treatment and prevention of the disease. There is no vaccine available for plague.
The authors say this "represents a significant public health concern".
In 1995, a new multi-drug-resistant form of Yersinia pestis was found in a 16-year-old boy in Madagascar. The strain had developed resistance to eight antibiotics including streptomycin and tetracycline.
Researchers discovered that the genes conferring this resistance are also in common food bacteria — such as salmonella, E. coli and klebsiella — from market samples of beef, pork, chicken and turkey in the United States.
As these genes are able to transmit themselves between bacteria, it raises the possibility of drug resistant Y. pestis emerging easily.
Lead author Jacques Ravel, of the US-based Institute for Genomic Research, says, "Our agricultural and medical use and abuse of antibiotics is generating a large reservoir of bacteria carrying resistance genes. These genes can move from bacteria to bacteria."
The key to containing any outbreak of plague lies in prompt treatment with common antibiotics such as tetracycline and streptomycin, which can reduce death rates from 60 to 15 per cent.
"Without antibiotics it is going to be extremely difficult to contain the disease. This is not a scenario we want," Ravel told SciDev.Net.
Kamal Krishna Datta, former director of India's National Institute of Communicable Diseases — who oversaw the 1994 plague outbreak in Surat, western India — said the discovery "needs to be widely shared and discussed and the disease surveillance mechanism strengthened through a global network."
Plague is one of the oldest diseases known to humans and has caused over 200 million deaths worldwide.
In the past five years alone, plague has been reported in Algeria, India, Malawi and Zambia. The last reported case was in the Democratic Republic of Congo in 2006.
Link to full paper in PLoS ONE
Reference: PLoS ONE 2(3): e309 (2007)