By Sola Ogundipe
New hope for eradication of malaria has emerged following the discovery of a bacterium that is capable of killing the malaria parasite – Plasmodium falciparum – by stopping its development in the stomach of the mosquito.
Researchers at the Johns Hopkins Bloomberg School of Public Health who identified the bacterium called Enterobacter said it is part of the naturally occurring microbial flora of the malaria-transmitting mosquito’s gut. From their studies published in Science, they found that the bacterium kills the parasite by producing reactive oxygen species (free radicals).
Prof. George Dimopoulos, senior author of the study and Associate professor at the W. Harry Feinstone Department of Molecular Microbiology and Immunology, and the Johns Hopkins Malaria Research Institute, said their research had previously shown that the mosquito’s midgut bacteria can activate its immune system and thereby indirectly limit the development of the malaria parasite.
“In this study we show that certain bacteria can directly block the malaria parasite’s development through the production of free radicals that are detrimental to Plasmodium in the mosquito gut,” he stated. “We are particularly excited about this discovery because it may explain why mosquitoes of the same species and strain sometimes differ in their resistance to the parasite, and we may also use this knowledge to develop novel methods to stop the spread of malaria. One biocontrol strategy may, for example, rely on the exposure of mosquitoes in the field to this natural bacterium, resulting in resistance to the malaria parasite. ”
Like humans, mosquitoes have a variety of bacteria in their digestive systems. For the study, the researchers isolated the Enterobacter bacterium from the midgut of Anopheles mosquitoes collected near the Johns Hopkins Malaria Research Institute at Macha, in southern Zambia.
About 25 percent of the mosquitoes collected contained the specific bacteria strain. Laboratory studies showed the bacterium inhibited the growth of Plasmodium up to 99 percent, in the mosquito gut and in a test tube culture of the human malaria parasite. Higher doses of bacteria had a greater impact on Plasmodium growth.