Chicken May Be Spreading Superbugs Through India's Food Chainby
Scientists find more virulent form of drug-evading bacteria
Superbugs found in 11% of chicken samples in India’s Hyderabad
Stealthy drug-evading bacteria with heightened virulence and ability to infect humans have turned up in chickens in India, scientists said, indicating an “alarming” consequence of the nation’s fast-growing poultry industry and the misuse of antibiotics.
Eleven percent of chickens sampled at fresh produce markets around the southern city of Hyderabad carried a multidrug-resistant form of a bacteria commonly found in birds and known to sicken people, a study found. The supergerms were detected in both intensively farmed broilers and free-range fowl, and were capable of thwarting routine antibiotics, scientists from the University of Hyderabad and the Robert Koch Institute in Berlin said.
The finding suggests contaminated meat may be spreading superbugs through the food chain and the environment, potentially causing hard-to-treat infections in people. Farms supplying India’s biggest poultry-meat companies routinely use antibiotics classified by the World Health Organization as “critically important” as a way of staving off disease, a months-long investigation by Bloomberg News in the Hyderabad region this year showed.
“Our findings provide scientific support to what is known about the use of antibiotics in the food-animal sector amid a lack of a properly enacted antibiotics policy in this country,” said Niyaz Ahmed, a senior author on the paper, which was published Nov. 4 in the journal Applied and Environmental Microbiology, in an e-mail.
The Helicobacter pullorum bacteria found in the chickens was remarkable because, beside harboring various genes for drug resistance, strains were also armed with the ability to produce toxins that potentially can damage the DNA of human cells, the researchers found. Their research was based on a study of the gastrointestinal tracts of 55 broiler and 45 free-range chickens bought at seven produce markets in Hyderabad.
More than 100 virulence genes were identified in the bacterial samples, including 40 related to motility, which could enhance the pathogen’s ability to take hold inside the intestinal tracts of both chickens and people, and 20 that enhanced the microbe’s ability to persist, including in warmer-bodied poultry, the authors said. Some genes also better equipped the bacteria to evade the immune system’s defenses.
In humans, H. pullorum is thought to cause gastroenteritis and may be associated with cancer and cirrhosis of the liver.
“If this organism uses antimicrobial resistance to augment its fitness, persistence and thereby its transmission, then it can emerge as a significant threat to human health,” said Ahmed, who is now senior director of Bangladesh’s International Centre for Diarrhoeal Disease Research.
The fact that free-range chickens, which aren’t routinely administered antibiotics, carried the superbugs was “truly unexpected,” he said.
It could indicate that these fowl occasionally eat antibiotic-containing feed, or are exposed to the bugs via contaminated water and food, or of the feces of infected animals and people, Ahmed said. But it means the gene-altered bacteria from the intensive poultry industry have spread to “even the stocks that were so far considered as a safe choice,” he said.
Agricultural systems in emerging economies such as China and India have changed radically in recent years, becoming increasingly intensive in order to meet growing domestic and global demands for animal protein, the Food and Agriculture Organization of the United Nations said in a report Wednesday. This is likely to heighten the occurrence and spread of infectious diseases in these systems, leading to increased antibiotic usage and resistance.
Indians consume 14 times more chicken meat than they did in 1985, and the market is one of the fastest-growing in the world. A study last year predicted the use of antibiotics in livestock could more than quadruple by 2030 in some parts of India, primarily driven by “extreme” growth in chicken consumption.
The bulk of antibiotics are used to spur animal growth. Stopping that practice in India would result in an annual loss of meat production worth about $1.1 billion, an Organisation for Economic Co-operation and Development report last year found.
Drug-resistant infections have the potential to cause a level of economic damage similar to -- and likely worse than -- that caused by the 2008 financial crisis, the World Bank said in September. Worldwide, it could add as much as $1 trillion a year to health-care costs by 2050.
India doesn’t have regulatory provisions for the use of antimicrobial drugs in cattle, chickens and pigs raised for domestic consumption, Ramanan Laxminarayan, a researcher with the Public Health Foundation of India, said in a study in March. A separate study published in April found 4 percent of chicken bought from shops in the eastern city of Kolkata harbored strains of salmonella, most of which were resistant to one or more antibiotics.
The latest study found that the H. pullorum bacteria were vulnerable to several older antibiotics, including the last-resort drug colistin, Ahmed said. Unless the use of the bacteria-fighting medicines are controlled on farms, it’s “only a matter of time” before the germs won’t be stopped by any drug, he said.