The Ganges Brims With Dangerous Bacteria

“When bacteria are stressed, they turn on their S.O.S. system,” said David W. Graham, a professor of ecosystems engineering at Newcastle University in Britain and a pioneer in antibiotic-resistance testing. “It accelerates the rate at which they rearrange their genes and pick up new ones.”

Eight years ago, Dr. Ahammad, a former student of Dr. Graham, suggested testing Indian waters.

“Until then,” Dr. Graham said, “I had avoided India because I thought it was one huge polluted mess.” With antibiotic-resistant bacteria so ubiquitous, it would be hard to design a good experiment — one with a “control,” someplace relatively bacteria-free.

“We needed to find some place with clear differences between polluted and unpolluted areas,” Dr. Graham said.

That turned out to be the Ganges.

Although it is officially sacred, the Ganges is also a vital, working river. Its numerous watersheds in the mountains, across the Deccan Plateau and its vast delta serve 400 million people — a third of India’s population — as a source of drinking water for humans and animals, essential for crop irrigation, travel and fishing.

Twice a year, two of Dr. Ahammad’s doctoral students, Deepak K. Prasad and Rishabh Shukla, take samples along the whole river, from Gangotri to the sea, and test them for organisms with drug-resistance genes.

The high levels discovered in the river’s lower stretches were no surprise. But the researchers found bacteria with resistance genes even in the river’s first 100 miles, after it leaves Gangotri and flows past the next cities downstream: Uttarkashi, Rishikesh and Haridwar.

More important, the researchers found that the levels were consistently low in winter and then surged during the pilgrimage season, May and June.