CHENNAI: Antibiotic misuse in poultry farms may worsen the crisis of multi-drug resistant bacteria, suggests a recent study published by the Centre for Science and Environment (CSE). Tamil Nadu, which contributes more than a sixth of total poultry production in India, would be at a serious risk of breeding these drug-resistant pathogens.
Multi-drug resistance is a global problem in which disease-causing bacteria evolves to become resistant to more than one antibiotic. Subsequently, diseases caused by these microbes are harder to treat. The study, ‘Antibiotic resistance in poultry environment’ established that antibiotic resistance is moving out of poultry farms and into agricultural fields (as manure) through untreated litter.
Isolates of three types of bacteria — E.coli, Klebsiella pneumoniae and Staphylococcus lentus were extracted from poultry litter, and tested for resistance against 16 antibiotics. Ten of these antibiotics have been declared Critically Important (CI) for humans by World Health Organisation (WHO).
The study found that 100 per cent of the E.coli, 92 per cent of Klebsiella pneumoniae and 78 per cent of Staphylococcus lentus isolated from the poultry environment were multi-drug resistant. About 40 per cent of E.coli and 30 per cent of Klebsiella pneumoniae isolates were resistant to at least 10 out of 13 antibiotics against which these bacteria were tested for resistance.
The study also found that both E.coli and Klebsiella pneumoniae had very high resistance to antibiotics that are of critical importance to humans as they are used as a last resort antibiotic in hospitals. The antibiotics that these bacteria were resistant to include penicillins, fluoroquinolones, third and fourth generation cephalosporins and carbapenems.
Antibiotics are given to poultry in the first six weeks to prevent early chick death. “Most poultry farms administer antibiotics in the first week for sure,” said D Kannan from College of Poultry Production and Management, Hosur. Low dosage of these drugs are also used as growth promoters in some farms. “Nearly 99 per cent of all antibiotics will be excreted by broilers within a week to 10 days,” he added.
This untreated litter is then used as manure in agricultural fields where the bacteria diffuses into the soil, mixing with pre-existing bacteria. “This is the part where the multi-drug resistant bacteria from the excreta mixes with non-resistant ones,” observed Amit Khurana, the lead author of the study, remarking that the resistance spreads within microbes through horizontal gene transfer.
This creates a larger reservoir of multi-drug resistant bacteria, that can eventually penetrate into pathogens that infect humans. “From the agricultural fields, these bacteria can go anywhere — into groundwater and food — and can infect agricultural workers and animals, thereby becoming a public health threat” he said.
Alarming findings
A study found 100% of E.coli, 92% of Klebsiella pneumoniae and 78% of Staphylococcus lentus were multi-drug resistant.
Antibiotics given to poultry are excreted and when this litter is used as manure, the multi-resistent bacteria in it mixes with other bacteria, multiplying the threat