Superbugs becoming frequent travellers
International travel boom has helped spread germs and antibiotic resistance especially from India and China
Smallpox, syphilis, plague, cholera – some of the planet’s most notorious scourges drastically expanded their reach, thanks to unsuspecting travellers.
With a record 3.77-billion air passengers worldwide in 2016, new disease-causing microbes have never traversed the
A woman in Reno, Nevada, who died recently from a rare bacterial infection is a tragic reminder. She picked up a variant of a germ called Klebsiella pneumoniae, probably while she was treated in India for a leg fracture and hip infection, health authorities said.
Tests found the bacterium was resistant to 26 antibiotics. No available drug could stop it from poisoning her bloodstream weeks after she was admitted to a hospital in Nevada.
The fatal case fits a pattern doctors in North America, Europe and Australia have observed for more than a decade: travellers who have spent time in India have an especially high risk of returning home with unwanted germs.
Most often, the drug-evading bugs are ingested in faecally contaminated food or water, and take up residence in the intestines, where they are incorporated into the body’s normal bacterial flora.
The stowaways can be dangerous if they escape from the bowel into other body tissues, such as the bladder, or enter into the bloodstream.
"There are lots of studies that show that being in India does put you at risk for these infections," says Ramanan Laxminarayan, a New Delhi-based director for the Centre for Disease Dynamics, Economics and Policy in Washington.
India carries one of the highest healthcare burdens from antibiotic-resistant bacteria in the world. Sepsis caused by drug-defying germs kills more than 58,000 newborns in India, according to Laxminarayan.
The overuse of antimicrobial medicines, and the lack of toilets and clean water, help propagate and spread the mutant microbes in the environment.
The Indian government is trying to counter that. The direct sale of antibiotics to the public was prohibited in March 2014 to halt excessive, unnecessary use. Later the same year, Prime Minister Narendra Modi began a programme to wipe out open defecation within five years as part of a nationwide "Clean India" campaign.
Johann Pitout, a medical microbiologist at the University of Calgary, was one of the first doctors to make the link between travel and the spread of resistant germs.
When he arrived in Calgary in 2002, the South African-trained doctor noticed his laboratory was receiving a disproportionately high number of supergerm-containing patient specimens from general practitioners and nursing homes, instead of hospitals – which typically are the biggest source of hard-to-kill bacteria.
The microbes that piqued Pitout’s interest were intestinal-dwelling bacteria that harboured enzymes, known as extended-spectrum beta-lactamases (ESBLs), which destroy most penicillin-and cephalosporin-based antibiotics.
"ESBLs were mostly in the community setting, which was the first time I’d ever seen that," Pitout says.
He began surveying patients to understand why and found the answer in responses to a question on travel history.
"The majority of patients had previously travelled to India and China. Those were the two places that stood out," he says.
India is predicted to be the world’s third-biggest air travel market by 2035. Since Pitout noted the infection link, it has come up as the country from which travellers are most likely to return with digestive tracts colonised by ESBL-producing bacteria in at least eight studies by research groups from Australia to New York.
In one study, doctors in Sweden tested rectal swabs from 105 volunteers who were about to travel internationally.
Only one already had E. coli with the drug-resistance enzyme before departure. Of the remaining 104 travellers, 100 provided a second rectal swab on returning to Sweden, 24 of whom were colonised with ESBL-producing bacteria.
Of the eight who travelled to India, seven carried the superbug in their digestive tract.
Taking an antibiotic, such as for travellers’ diarrhoea, increases the risk because it disturbs normal gut flora, allowing new intestinal microbes to take hold. Once inside the bowel, the supergerms can migrate to cause a difficult-to-treat urinary tract infection, Pitout says.
They also pose a risk for men undergoing a prostate biopsy or anyone having bowel or gallbladder surgery, says Peter Collignon, head of infectious diseases at Canberra Hospital in Australia, who sits on a panel advising the World Health Organisation (WHO) about antimicrobial resistance.
Patients in hospital with an invasive ESBL infection are usually treated with a medicine from the carbapenem class, though even those antibiotics are failing now that bacteria are increasingly harbouring carbapenemase enzymes that neutralise these drugs. In many cases, that leaves just one antibiotic: colistin. That too is losing its potency, thanks to a bacterial gene first identified in China that has since turned up in at least 20 countries.
That finding and other recent studies show antimicrobial resistance is a growing worldwide problem, with an especially high incidence in countries in South Asia, Southeast Asia, China and some areas in southern Europe, such as Greece, says Lindsay Grayson, head of infectious diseases at the Austin Hospital in Melbourne.
"The extent of the spread of these organisms and the size of the problem is still being defined," Grayson says in a phone interview from Geneva, where he is assisting the WHO in formulating clinical guidelines to control the spread.
"In Australia, we have increasing concerns about travellers, such as businessmen, who have recently returned from China who are about to undergo surgical procedures. They should undergo faecal screening to see if they have acquired similarly resistant organisms that could later affect their healthcare."
The bacterium that killed the woman in Nevada resisted carbapenem as well as colistin. It was fortified with a gene that has been dubbed New Delhi metallo-beta-lactamase — a reference to the city where a Swedish man was hospitalised in 2007 with an infection that could not be stopped by carbapenem or any commonly prescribed antibiotic treatment.
The gene is now found in bacteria worldwide including in the US, making it impossible to prove whether or not the Nevada patient, who was in her 70s, picked it up during her extended visit to India, says Laxminarayan.
Even still, it’s plausible that India was the source.
"Carbapenem resistance is rife in India — both in the community and in hospitals," he says.