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Typhoid data raise drug overuse spectre

New Delhi, Aug. 11: The share of typhoid caused by multi-drug resistant germs in Calcutta has nearly doubled over the past five years, possibly through widespread and indiscriminate use of antibiotics, a four-hospital study has suggested.

The study led by researchers at the National Institute of Cholera and Enteric Diseases (NICED) has found that the share of illness in children caused by MDR Salmonella typhi has increased from 13 per cent in 2009 to 25 per cent in 2013.

The NICED researchers have also found that a key antibiotic called ciprofloxacin that became the drug of choice to treat typhoid during the late-1990s is no longer effective in the illness. The study findings have just been published in the journal PLOS One.

“Drug-resistant typhoid bacilli have been around for more than two decades, but the failure of ciprofloxacin is an ominous sign,” said Shanta Dutta, a scientist at the NICED. “In only about 15 years, the germs have evolved to render ciprofloxacin non-functional.”

Doctors in India have been concerned about the emergence of MDR versions of the two typhoid bacilli — Salmonella typhi and Paratyphoid A — since the early-1990s when teams of microbiologists across the country started detecting germs that could survive some common antibiotics such as ampicillin, chloramphenicol, and co-trimaxazole widely used against the infection until then.

“By the late-1990s, ciprofloxacin became the most useful drug against typhoid,” Dutta said. “But indiscriminate use of this antibiotic not just in typhoid but in other infections appears to be responsible for the patterns of resistance we’re observing now,” she told The Telegraph.

Dutta and her colleagues at BC Roy Institute of Paediatric Sciences, Calcutta Medical Research Institute, Apollo Gleneagles and Advance Medical Research Institute, explored drug-resistance typhoid in 422 children below 15 years between 2009 and 2013.

They found that nearly 80 per cent of Salmonella typhi strains had decreased susceptibility to ciprofloxacin and 19 per cent had turned fully resistant to the antibiotic. And 76 per cent of Paratyphi A displayed decreased susceptibility and 20 per cent were resistant to ciprofloxacin.

“Ciprofloxacin is unlikely to work in typhoid,” Dutta said. But the resistance patterns the researchers have observed are not unique to Calcutta. Studies from other cities in India have over the past decade also hinted at emerging resistance to ciprofloxacin.

The Calcutta study has however found that an antibiotic called azithromycin and a set of antibiotics called the third-generation cephalosporins could still treat all the strains of typhoid they had isolated from the children.

“Azithromycin and the third-generation cephalosporins have now become the drugs of choice for typhoid, but doctors should use them with caution, only in confirmed typhoid cases,” Dutta said.