The gene causing colistin resistance is called mcr-1, and this has been found in pig farms and marketed meats. Colistin fell out of favour post-development in treatment plans as it was found to cause severe renal damage. However, in China colistin is widely used in the agricultural industry, as low doses of the antibiotic stimulates growth in animals.
Unfortunately, bacterial evolution is dynamic, and as bacteria in the animals evolves, antibiotic resistance arised, even to colistin. What is more disturbing is a Lancet report, showing evidence that mcr-1 has transferred across species, from pigs to humans, possibly due to consumption of said meat.
Resistance gene made trans-species leap, from pigs to human beings
Earlier this year, Chinese officials approved the use of colistin in hospitals as a reserved last-line option against superbug infections. However, following the discovery that mcr-1 has leapt from pigs to humans, fears have arised that hospital usage of this drug may aggravate the resistance issue.
In the aforementioned study, approximately 1 per cent of 17,000 samples from patients with gut infections of common bacteria were found to be colistin-resistant. The samples were collected from two hospitals in the Zhejiang and Guangdong provinces.
The emergence of mcr-1 is currently confined to China but authors of the study have warned that it is likely to spread well beyond Chinese borders, urging an urgent need for coordinated global efforts in battling a potential worldwide ‘antibiotic apocalypse’.
Superbugs in the MTR
Nonetheless, merely avoiding the consumption of meat treated with colistin may not be a sufficient protection against superbugs. Numerous investigations have found that bacteria resistant to all commonly used antibiotics have infested the Hong Kong’s MTR commuter rail network, with the highest concentrations found on trains connecting Kowloon and the Chinese border – the East Rail Line and the Ma On Shan line.
Such bacteria were also found to be present on the hands of students who boarded various MTR lines.
Superbugs in the sea
In Hong Kong, treated sewage gets disinfected with chlorine before it is released into watercourses and the sea. But chlorine alone does not kill drug-resistant superbugs entirely.
“In the sea, swimmers are at risk of picking up disease-causing bacteria that have acquired the genes for resistance,” said Professor Tong Zhang, of the Department of Civil Engineering, University of Hong Kong.
“Others might catch them from infected seafood. If people get sick, the bacteria will multiply in their bodies and be added to the sewage system, starting the process all over again,” he added.
Careful use of antibiotics
Given all these, there is no doubt that the use of antibiotics in the hospitals, especially colistin, should be restricted to prevent the worsening of antibiotic resistance. The case of mcr-1 serves as a warning for the possible, if not eventual, scenario where no effective antibiotics can be found any longer to treat superbug infections. MIMS
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