Bugs and the city

Tue, Aug 7, 2012, 01:00

Just as cities are gathering places for people, they are also gathering places for organisms, writes CLAIRE O'CONNELL

WHY COULD cities act as engines for the spread of so-called “superbugs”? Because cities are large gatherings of people and can provide ideal conditions for antibiotic resistance to spread, according to journalist and author Maryn McKenna, who will talk at the Science Gallery in Dublin this evening.

A regular blogger on infectious disease at Wired, US-based McKenna is no stranger to the world of infectious disease. She spent 10 years reporting on how the Centers for Disease Control were gathering intelligence on epidemics, and her book, Beating Back the Devil, chronicled some of those investigations. Another book, Superbug, focused on the rise of MRSA. But this evening she will turn her focus to cities, and particularly how they can catalyse the spread of antibiotic resistance, which is a growing problem.

“Antibiotic resistance is the ability of disease-causing organisms, bacteria and viruses to defend themselves against insults, and it’s something that happened long before humans came along,” explains McKenna.

“Bacteria always had the ability to produce chemical compounds that allowed them to defend themselves against other bacteria, to compete for resources or clear out living space.”

Since the first medical use of penicillin in mid-20th century, we have been identifying such antibiotic compounds and manufacturing them in labs ourselves, but we haven’t been using them properly, she notes.

“Since bacteria were always able to defend themselves against each other’s compounds, we shouldn’t really be surprised that they could also defend themselves against us. And by not taking that seriously, we have made antibiotic resistance so much worse, because as we expose bacteria to the precious chemical weapons we have, they recognise them and develop mutations and defend against them.”

McKenna describes how the overuse and misuse of antibiotics both in medicine and agriculture has created a kind of “Darwinian battle ground” where the bacteria that develop resistance to the drugs can survive and take advantage of the living space of the weak bacteria being killed off.

Meanwhile, against this backdrop, we have vulnerable patients gathered in hospitals, large numbers of people living at close quarters in cities and the fluid movement of people around the world, offering ripe conditions for the so-called “superbugs” with antibiotic resistance to potentially gain footholds and spread.

McKenna describes as “chilling” the recent emergence of resistance factors in bacteria that enable them to withstand a class of antibiotics called carbapenems. She cites two outbreaks in particular, involving an enzyme called NDM-1, which is thought to have originated in India, and Klebsiella pneumoniae carbapenemase (KPC) in the US.

Bacteria with the resistance factors can be carried in healthy people and can then cause problems for vulnerable patients if the antibiotic-resistant bugs get into a hospital setting.

“The thing that makes these so apocalyptic is they confer resistance to carbepenems, which most people who deal with infectious disease really think of as last resort drugs,” says McKenna.

She has been keeping an eye on the spread of recorded carbapenem resistance factors, and describes how they can move in and out of hospital settings and be spread between locations as people travel. So where do cities come in?

“We think of cities as these things that make all these great things so easily available to us, these concentrations of art and culture,” says McKenna. “But since they are also gathering places for people, they are gathering places for organisms as well.”

The rise of “megacities” could offer a particular case in point, she notes.

“They are megacities because people are being drawn to them from other parts of the country due to a perceived economic opportunity, and for the most part, the fringes of megacities tend to be mostly quite poor. That means they may not have good municipal systems, good water delivery, sewage transport or food transport, so there are already conditions that are positive for spreading these organisms around.”

In addition, says McKenna, there may not be adequate surveillance of emerging diseases. “There could be a lack of a system to keep these things confined and also a lack of surveillance to notice that they are happening.”

At 6pm this evening in the Science Gallery on Pearse St, Dublin 2, Maryn McKenna will give a talk called An Outbreak of Antibiotic Resistance to tie in with the gallery’s ongoing Hack the City exhibition. Claire O’Connell will be MC/presenter at the event. Admission €5. To book, go to sciencegallery.com

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