Diarrhoea bug develops resistance to Colistin, antibiotic widely used for poultry

Muhammad Zahir Hassan Nabil

One major diarrhoea-causing pathogen recently found in Dhaka city sludge has shown resistance to 'Colistin' - a last-resort antibiotic for infection control, widely used in the poultry industry in Bangladesh.

Nearly 30 percent poultry farms are reportedly using Colistin in Bangladesh. Photo: GMB Akash / icddr,b

The Colistin-resistant bacterium Escherichia coli (E. coli) was multi-drug resistant (MDR), showing resistance to 11 different antibiotics tested.

“Resistance to Colistin is a public health concern because it is a last resort against bacteria resistant to carbapenems, which is another last-resort antibiotic,” opines Dr Munirul Alam, senior scientist at icddr,b and senior author of the study reported in the journal Gut Pathogens.

E. coli are a diverse group of bacteria found across the environment, e.g. in food, and in the intestines of people and animals. Although many E. coli strains are innocuous, some may cause serious illnesses including diarrhoea.

Colorised scanning of E.Coli under electron micrograph. Photo: NIH-NIAID. CC BY 2.0

The MDR E. coli identified in the study was shown to carry the mcr-1 gene - an established indicator for Colistin resistance. This is the first ever identification of mcr-1 in Bangladesh, according to the study jointly supported by icddr,b, NIH, USA and National Institutes of Infectious Diseases (NIID), Japan.

Last-resort drugs like Colistin are being used more frequently since more and more antibiotics have been failing due to growing antibiotic resistance – a phenomenon when antibiotics do not work as certain bacteria become immune to specific drugs.

“It is a vicious cycle. E. coli turning resistant to so many antibiotics means that it may be difficult for many patients to recover if they are affected by this MDR bacterium,” adds Dr Alam.

Infographic: Inamul Shahriar / Muhammad Nabil / icddr,b

“According to survey reports, up to 30 percent poultry farms are using Colistin in Bangladesh. It is clear from recent evidences that such overuse of drugs is contributing to multi-drug resistance in E. coli and others infectious agents worldwide,” says Mr Aminul Islam Arif, research officer at icddr,b and author of the study.


The environment is involved

In Bangladesh, urban sludge is often channelled to water bodies due to the congested city setting and the lack of proper drainage and sewerage treatment systems. Overuse and disposal of drugs increases residual antibiotics in the environment, allowing the rise of such multi-drug resistant bacteria. This often remains unnoticed, but poses a serious threat to humans and animals.

Dr Alam went on to explain that humans also consume antibiotics indirectly as the residues enter the food-chain from the environment, through drinking water and poultry-based foods such as meat and eggs containing absorbed antibiotics. Such exposure is potentially fatal because commensal strains of E. coli and other bacteria in the human gut can acquire resistance to these antibiotics, making it difficult to treat when the same drug-resistant bacteria cause opportunistic infections.

To fend off such mounting crisis, many scientists worldwide are uniting under a novel concept called One Health, which addresses health concerns affecting humans, animals and the environment as a whole.

Many poultry farms are built over water bodies. Photo: Hasin Hayder. CC BY-NC-ND 2.0

As many people acquire water from unsafe sources in Dhaka city, the study warns that widespread faecal-oral contamination might allow these MDR pathogens to transmit rapidly and cause illness. The icddr,b report also strongly recommends broader surveillance in both clinical and environmental settings in Bangladesh in order to prevent further spread of bacteria carrying mcr-1.

Recommendations from the icddr,b study suggest that relevant authorities should take action in order to ensure that the rational usage of antibiotics is implemented across the country.

Additionally, monitoring of clinical settings like hospitals, clinics and drug production facilities is essential to make sure that antibiotics are not released into the environment without proper disposal systems.

Antibiotic-resistant bacteria can cause illnesses that are difficult to cure. Photo: GMB Akash / icddr,b

Inappropriate exposure of antibiotics turns bacteria into lethal mercenaries, so much so that diseases caused by them may become incurable in the future. Through different and complex pathways, these bacteria may cause formidable illnesses.

The recent findings remind us to clearly communicate that the environment encompasses animals as well as humans. An environment fraught with too many antibiotic resistance bacteria is a clear threat to all who encounter it. Action is needed today to prevent misuse or careless disposal of the drugs, which will determine our ability to fight disease in the future.