Everything that goes down our drains will find its way to the sea, including the stuff we flush down the toilet. This quirky way by which humans pollute the water systems has shown to cause antibiotic resistance of disease causing bacteria in the aquatic and marine environment of Metro Manila, a study found.
Monitoring conducted by the researchers revealed sulfamethoxazole (SMX) as a major contaminant along the waterways of the Metro. SMX belongs to a group of antibiotic drugs called sulfanomides. It is a common medicine used for treating infection in humans and animals. It is believed SMX in the water come from manure and wastewater that are released to Laguna Lake and Pasig River, subsequently concluding in the Manila Bay area.
Sulfonamides, as compared to other major groups of antibiotics commonly found along the waterways of Southeast Asia, are more likely to trigger drug resistance in bacteria. In the study, researchers looked for bacteria that have acquired resistance to sulfonamides and the genes responsible for this trait.
Cultures of bacteria from surface water samples taken in different areas in Laguna Lake, Pasig River and Manila Bay showed that both bacteria naturally found in the environment and bacteria naturally found in human intestines are present in Laguna Lake and Pasig River. Both developed resistance to sulfanomides.
DNA tests on collected intestinal and environmental bacteria revealed three different types of genes that allow these microorganisms to resist antimicrobial actions of sulfanomides. However, only two of the three genes were found to be present in bacteria collected from Laguna Bay and Pasig River while all of them are found in samples from Manila Bay.
Researchers discussed that the three types of antibiotic resistant genes most likely have human origin carried by bacteria in wastewaters thrown in Laguna Lake and Pasig River. Contact between the marine bacteria with microorganisms in the wastewater allowed transfer of the genes in the environment’s natural ecosystem.
Citing that antibiotic resistant genes are difficult to eliminate once they have been acquired, drug resistance could be passed among different species and generations of bacteria in Manila Bay. Researchers warned that even in areas considered pristine, colonies of bacteria are found to have acquired the genes for drug resistance.
Direct implication to health of the drug resistance has not yet been identified. However, the study presented a different perspective on how human activities affect the environment.
When we think about water pollution, we think about toxic wastes, solid garbage and even oil spill. However, the study showed that less obvious contaminants such as antibiotics can have an enormous effect on the living organisms and biodiversity of the region.
Suzuki S, Ogo M, Miller TW, Shimizu A, Takada H, Siringan MA. (2013). Who possesses drug resistance genes in the aquatic environment?: sulfamethoxazole (SMX) resistance genes among the bacterial community in water environment of Metro-Manila, Philippines. Frontier in Microbiology. 4:102.