The last plague pandemic began in Hong Kong in 1894 and spread throughout the world. Plague still exists as an endemic disease in many parts of the world, including the southwestern U.S. Prevention of plague is based on rodent control, and the use of insect repellents to minimize flea bites. Nevertheless, plague is now considered a reemerging disease, with recent epidemics in a number of countries after an absence of as much as 3 decades. The resistant genes are apparently carried by a plasmid that can conjugate to other Y. pestis isolates. So this pathogen species, heretofore considered universally susceptible to antibiotics, is now exhibiting high and spreadable resistance to these drugs.
Epidemiologists are alarmed and are urging an international effort to deal with the problem.
The consensus is apparently that a compensatory mutation has occurred, a mutation that compensates for the loss of fitness produced by the gene that confers antibiotic resistance, and which results in long-term survival of the resistant strain. The implication is that the evolutionary development of bacterial resistance to antibiotics will not be reversed by reducing the use of these antibiotics, which means the effective- ness of these antibiotics is essentially irreversibly lost.