A new study found a higher prevalence of antibiotic-resistant Escherichia coli in water and child stool samples taken from rural areas of Bangladesh with high arsenic contamination levels in drinking water compared to areas with less contamination.
The research, led by Mohammad Aminul Islam, an assistant professor at Washington State University's Paul G. Allen School for Global Health, was recently published in the journal PLOS Pathogens.
Antibiotic resistance is one of the leading causes of death and hospitalization worldwide. While the major drivers of antibiotic resistance are the overuse and misuse of antibiotics, natural elements such as heavy metals can also promote antibiotic resistance.
"Bacteria may use similar mechanisms to become resistant to heavy metals and antibiotics. Therefore, it is likely that humans and animals that are exposed to heavy metals may be colonized by antibiotic-resistant organisms even without being exposed to antibiotics," Islam said. "This means even optimum use of antibiotics in human and animal medicines may not be sufficient to combat antimicrobial resistance in those areas where people are naturally exposed to the high concentration of heavy metals."
The collaborative study involved researchers from WSU, the International Centre for Diarrhoeal Disease Research, Bangladesh; University of Washington; Oregon State University; and Eawag in Switzerland.
Researchers collected water and stool samples from both mothers and young children of 100 families in two rural subdistricts in Bangladesh. Families in the Hajiganj subdistrict use drinking water from shallow tube wells that have a high concentration of arsenic, a toxic heavy metal ubiquitously present in the environment, while families from the Matlab area collect their drinking water from arsenic-free deep tube wells.
The median arsenic concentration in the 50 water samples from Hajiganj was 481 micrograms per liter (about 1.7 ounces to a quart) while the median arsenic concentration in the 50 water samples from Matlab was 0 micrograms per liter. The prevalence of antibiotic-resistant E. coli was significantly higher in water in Hajiganj (48%) compared to water in Matlab (22%) and among children in Hajiganj (94%) compared to children in Matlab (76%), but not among mothers. Moreover, a higher proportion of E. coli from Hajiganj were resistant to multiple antibiotics, including penicillin, cephalosporin, and chloramphenicol.
"We found that arsenic-resistant E. coli are more likely to be resistant to a certain group of antibiotics, especially the third-generation cephalosporins, which are commonly used for the treatment of bacterial infections," said Prabhat Talukdar, a postdoctoral researcher in Islam's lab and first author of the publication. "Our current study is investigating the mechanisms of co-resistance to arsenic and antibiotics among these isolates."
The researchers wrote that the findings show this is an important public health concern that warrants redoubling efforts to reduce arsenic exposure. "Heavy metals such as arsenic are more stable than antibiotics in the environment, and they continue to exert selective pressure on bacteria over a more extended period driving the evolution and expansion of antimicrobial resistance in the community," Islam said. "The extent to which this phenomenon drives the observed higher rates of antimicrobial resistance, as opposed to other confounders, would benefit from the further study; nevertheless, it is critical to contain this environmental driver of antimicrobial resistance along with responsible antimicrobial usage in medicine and agriculture."
