Researchers' discovery may explain difficulty in treating Lyme disease

"It hasn't been entirely clear why it's dif­fi­cult to treat the pathogen with antibi­otics since there has been no resis­tance reported for the causative agent of the dis­ease," explained Uni­ver­sity Dis­tin­guished Pro­fessor Kim Lewis, who led the North­eastern research team.

In other chronic infec­tions, Lewis' lab has tracked the resis­tance to antibi­otic therapy to the pres­ence of per­sister cells--which are drug-tolerant, dor­mant vari­ants of reg­ular cells. These per­sister cells are exactly what they've iden­ti­fied here in Bor­relia burgdor­feri, the bac­terium that causes Lyme disease.

The researchers have also reported two approaches--one of them quite promising--to erad­i­cate Lyme dis­ease, as well as poten­tially other nasty infections.

Lewis and his col­leagues pre­sented their find­ings in a paper pub­lished online last week in the journal Antimi­cro­bial Agents and Chemotherapy. He co-authored the paper with North­eastern doc­toral stu­dents Bijaya Sharma and Autumn Brown, both PhD'16; recent grad­uate Nicole Matluck, S'15, who received her Bach­elor of Sci­ence in Behav­ioral Neu­ro­science; and Linden T. Hu, a pro­fessor of mol­e­c­ular biology and micro­bi­ology at Tufts University.

The research was sup­ported by grants from the Lyme Research Alliance and the National Insti­tutes of Health.

Lyme dis­ease affects 300,000 people annu­ally in the U.S., according to the Cen­ters for Dis­ease Con­trol and Pre­ven­tion, and is trans­mitted to people via bites from infected black­legged ticks. If caught early, patients treated with antibi­otics usu­ally recover quickly. How­ever, about 10 to 20 per­cent of patients, par­tic­u­larly those diag­nosed later, who have received antibi­otic treat­ment may have per­sis­tent and recur­ring symp­toms including arthritis, muscle pain, fatigue, and neu­ro­log­ical prob­lems. These patients are diag­nosed with Post-treatment Lyme Dis­ease Syndrome.

In addi­tion to iden­ti­fying the pres­ence of these per­sister cells, Lewis' team also pre­sented two methods for wiping out the infection--both of which were suc­cessful in lab tests. One involved an anti-cancer agent called Mit­o­mycin C, which com­pletely erad­i­cated all cul­tures of the bac­terium in one fell swoop. How­ever, Lewis stressed that, given Mit­o­mycin C's tox­i­city, it isn't a rec­om­mended option for treating Lyme dis­ease, though his team's find­ings are useful to helping to better under­stand the disease.

The second approach, which Lewis noted is much more prac­tical, involved pulse-dosing an antibi­otic to elim­i­nate per­sis­ters. The researchers intro­duced the antibi­otic a first time, which killed the growing cells but not the dor­mant per­sis­ters. But once the antibi­otic washed away, the per­sis­ters woke up, and before they had time to restore their pop­u­la­tion the researchers hit them with the antibi­otic again. Four rounds of antibi­otic treat­ments com­pletely erad­i­cated the per­sis­ters in a test tube.

"This is the first time, we think, that pulse-dosing has been pub­lished as a method for erad­i­cating the pop­u­la­tion of a pathogen with antibi­otics that don't kill dor­mant cells," Lewis said. "The trick to doing this is to allow the dor­mant cells to wake up."

He added: "This gives you an idea that you could, in prin­ciple, estab­lish a sim­ilar reg­i­ment for treating patients for this and other chronic diseases."

Lewis is a fac­ulty member in the biology depart­ment and directs Northeastern's Antimi­cro­bial Dis­covery Center. Over the past decade he has led pio­neering work on this spe­cial­ized class of cells pro­duced by all pathogens known as per­sis­ters. Ear­lier this year, Lewis, biology pro­fessor Slava Epstein, and other col­leagues pub­lished ground­breaking research in Nature pre­senting a new antibi­otic that kills pathogens without encoun­tering any detectable resistance.

In pre­vious work, Lewis' lab iden­ti­fied a com­pound called ADEP that causes dor­mant per­sister cells in MRSA to self-destruct. This com­pound was among the first options the researchers tried out to combat Lyme dis­ease. But it didn't work, and nei­ther did com­bi­na­tions of stan­dard antibi­otics used to treat the dis­ease. The team thought it had hit a dead end yet remained vig­i­lant in its quest to iden­tify promising alter­na­tive options.

"What we came up with was the pulse-dosing reg­imen, which worked beau­ti­fully," Lewis explained. "I think this could be very useful, espe­cially for antibi­otics for which resis­tance doesn't rapidly develop."

Though the researchers iden­ti­fied the pres­ence of these per­sister cells, they also note in their paper that the mech­a­nisms by which the per­sis­ters are able to sur­vive remain unknown. More work in this area will be required, they wrote.