‘Su­per­bug’ gene alarms Canada health of­fi­cials

China Daily (Canada) - - FRONT PAGE - By HENG WEILI in New York

A gene that makes bac­te­ria re­sis­tant to a strong an­tibi­otics — first re­ported in China — has made its way to Canada, ac­cord­ing to pub­lished re­ports.

The gene is called MCR-1, which pro­duces an en­zyme that makes bac­te­ria in­vin­ci­ble to col­istin, a toxic an­tibi­otic used when all oth­ers have failed, the Toronto Star re­ported.

MCR-1 was ini­tially re­ported in Novem­ber by Chi­nese sci­en­tists, who pub­lished a pa­per in The Lancet, an in­ter­na­tional med­i­cal jour­nal.

“The emer­gence of MCR-1 her­alds the breach of the last group of an­tibi­otics, polymyx­ins, by plas­mid-me­di­ated re­sis­tance,” the Lancet re­port said. “Al­though cur­rently con­fined to China, MCR-1 is likely to emu­late other global re­sis­tance mech­a­nisms such as NDM-1. Our find­ings em­pha­sise the ur­gent need for co­or­di­nated global ac­tion in the fight against pan-dru­gre­sis­tant Gram-neg­a­tive bac­te­ria.”

Re­searchers in China found 260 sam­ples of E. coli with the MCR-1 gene on meat, hos­pi­tal pa­tients and farm an­i­mals.

E. coli, or Escherichia coli, is a germ (bac­terium) found in the di­ges­tive tracts of hu­mans and an­i­mals. A per­son can get an E. coli in­fec­tion by com­ing into con­tact with hu­man or an­i­mal fe­ces.

The re­searchers found E. coli with MCR-1 on 21 per cent of slaugh­ter­house pigs and 15 per cent of raw chicken and pork. Six­teen hos­pi­tal pa­tients were found to have had MCR-1 in­fec­tions.

“The ef­fect on hu­man health by mo­bile col­istin re­sis­tance can­not be un­der­es­ti­mated,” the re­searchers said.

A key find­ing was that MCR-1 is lo­cated on a plas­mid, a freefloat­ing piece of DNA that bac­te­ria can share.

“It’s clearly the big­gest story to come out (in 2015),” said Lance Price, an en­vi­ron­men­tal health pro­fes­sor at Ge­orge Wash­ing­ton Univer­sity, told the Star. “There have been hor­ri­ble things all year but this is the most dis­turb­ing.”

About a dozen other coun­tries have since found the MCR1 gene, the Star re­ported, in­clud­ing Canada, which launched an in­ves­ti­ga­tion in De­cem­ber.

The Cana­dian re­sults have not been pub­lished, but a case re­port was sub­mit­ted to the Lancet, Dr Michael Mul­vey, chief of an­timi­cro­bial re­sis­tance with the Pub­lic Health Agency of Canada in Win­nipeg, told the Star.

The gene was found in three dif­fer­ent sam­ples of E. coli, all pre­vi­ously col­lected for re­search projects: one from a 62-year-old pa­tient in Ot­tawa and two from ground beef in On­tario. The Ot­tawa pa­tient likely got the bug in Egypt, where she lived for sev­eral years, ac­cord­ing to Dr. Bald­win Toye.

The beef sam­ples were dis­cov­ered nearly a year apart in dif­fer­ent lo­ca­tions in On­tario, a butcher shop and a gro­cery chain, Mul­vey said. They were col­lected in 2010, be­fore the sam­ples from China, which were gath­ered be­tween 2011 and 2014, the Star re­ported.

Col­istin be­longs to a group of an­tibi­otics called polymyx­ins. It was dis­cov­ered in the late 1940s but its use was dis­con­tin­ued be­cause of its highly toxic side ef­fects.

“We’ve sort of run out of our good drugs,” Price said. “So out of des­per­a­tion … we have to re­vive this old drug be­cause it’s all we have left.”

Col­istin is rarely used in hu­man medicine be­cause doc­tors want to pre­serve its ef­fec­tive­ness. But polymyx­ins are given to live­stock to pre­vent in­fec­tions, par­tic­u­larly in China.

Col­istin isn’t used in agri­cul­ture in Canada, but polymyxin B, a sim­i­lar com­pound, is, the Star re­ported.

Ti­mothy Walsh, a mi­cro­bi­ol­o­gist with Cardiff Univer­sity who co-au­thored the ini­tial Lancet pa­per, said the Chi­nese gov­ern­ment is tak­ing MCR1 se­ri­ously and he expects it will ban col­istin in agri­cul­tural use.

“Any an­tibi­otic class used for hu­mans should never be used for an­i­mals (un­less they’re sick),” he told the Star.

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