s per the latest study by Goa-based National Institute of Oceanography, during monsoon season overflowing water bodies bring in considerable number of pathogens from various sources which cause multi antibiotic resistance (MAR), posing a health risk for Goans.
MAR occurs when micro-organisms such as bacteria, viruses, fungi and parasites change their nature in such a way that the medications used to cure the infections become ineffective. When the micro-organisms become resistant to most antimicrobials they are often referred to as superbugs.
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India has one of the highest rates of resistance to antimicrobial agents used both in humans and food animals. The environment, especially the water bodies, have also reported the presence of resistant organisms or their genes. Over-use of antibiotics and inadequate treatment of waste waters are key reasons for MAR in India.
“The two adjacent estuaries of the rivers Mandovi and Zuari, along the Goa coast are a large complex aquatic system hosting diverse natural habitats. The water quality in these habitats is affected by various human activities as they are extensively used for transportation, fisheries and various recreational activities,” said Dr Durbar Ray, Principal Scientist at CSIR-NIO.
In the present study, changes in the water quality and levels of microbial pollution during the pre-monsoon, monsoon and post-monsoon seasons were determined.
The water quality index was estimated based on the parameters: temperature, salinity, dissolved oxygen, biochemical oxygen demand and nutrients. The seasonal changes in the microbial pollution load were also assessed based on the abundance of pollution indicator organisms and its resistivity towards multiple antibiotics.
“The appearance of antibiotic-resistant bacteria in Indian coastal waters has been reported frequently in the last few years. A couple of previous studies have reported antibiotic resistance microbial populations in coastal waters adjacent to thickly populated Indian cities. Keeping these in mind, the proposed studies were carried out to assess the antibiotic resistance nature of available Pollution Indicator Organisms (PIOs) from the estuarine system along with basic water quality parameters,” Dr Ray said.
Estuaries are the wide part (mouth) of a river where it joins the sea. The seasonal water quality indexes (WQI) based on basic physicochemical parameters of these estuarine waters, indicate the overall water quality is slightly dropped during non-monsoonal seasons as compared to monsoon. The observed differences in seasonal water qualities are mostly due to the mixing of estuarine waters with large volume of freshwater during monsoon relative to dry seasons. At the same time, the monsoonal flushes bring more land-washed materials; and that likely stimulates the microbial population having higher MAR values the study area.
Earlier studies show that due to the rapid increase in human activities, the level of sediments entering these estuarine environments along the river discharge has been rising at an alarming ratein the Mandovi and Zuari estuaries which are considered to be the lifeline of Goa.
Studies also show deterioration of environmental quality due to an increase in the levels of various pathogenic microbes such as coliforms (bacteria that are always present in the digestive tracts of animals, including humans, and are found in their wastes), Vibrio sp., Salmonella sp., Shigella sp. And Streptococcus sp.
Adding to this, regular urban effluents bringing in medical wastes, especially antibiotic loads, increase the threat to the ecosystem. This not only introduces antibiotic- resistant microbial strains into the environment but also accelerates the spread of resistance genes to indigenous bacterial flora. As a consequence, the emergence of multidrug resistance is a major threat faced by today’s world.
“In the present study, it was decided to monitor the basic water quality at selected sampling stations (16 nos.) around both Mandovi and Zuari estuaries on a seasonal basis (i.e., pre-monsoon, monsoon and post-monsoon). At each sampling site, the surface and near bottom waters and top part of sediments were collected for quality monitoring,” he said.
Water samples were analysed for various parameters like pH, Dissolved oxygen, B.O.D (Biological oxygen demand is essentially a measure of the amount of oxygen required to remove waste organic matter from water), dissolved nitrate, phosphate, silicate, chlorophyll, etc.
While, each sediment sample was studied for its texture, organic carbon and toxic metals contents, both water and sediments were also monitored for microbiological parameters like total viable bacterial counts and counts for certain bacterial, pollution indicator organisms (PIOs) including the species like Streptococcus (responsible for diarrhea, nausea, vomiting) Vibrio, Shigella, Coliform, Staphylococcus, Pseudomonas.
Approximately 90 representative isolates of major pollution indicator bacterial groups from all three seasons were tested for their susceptibility towards 16 different antibiotics belonging to bacteriostatic and bactericidal classes. Among the 35 isolates tested from the pre-monsoon season, 30 isolates showed resistance to Clindamycin (prescribed for treating bacterial infections), while all of them were susceptible to Ofloxacin and Tetracycline (for treating urinary tract infections).
About 86% of the isolates tested showed an MAR index of less than 0.2, which can be categorised as low risk pollution indicators.
Results also showed that such counts of PIOs with very high risk factor are extremely low (9.1% of total population). However, based on the results of this preliminary study, it is difficult to predict about the direct impacts (if any) of such seasonal variations of estuarine water quality on the people.
“The development of drugs resistivity in common pollution indicator bacterial strains is not good indicator for any environmental quality, in general. Of course, in our investigation, it has been found that very few bacterial strains (max 9.0% of total strains tested) have high MAR index values (>0.4); classified as a high risk category. Therefore, in the present situation, such drug resistance factors might not impact detrimentally,” Dr Ray said.
However, considering the current scenario, regular monitoring of the estuarine habitats to determine the health of the coastal water bodies is required. It can directly impact the surrounding riverine systems, and its deterioration can have a major threat to the human population dependent on them,the study stated.
The study titled ‘Seasonal variations in the water quality and antibiotic resistance of microbial pollution indicators in the Mandovi and Zuari estuaries, Goa, India’ has been published in the Article in Environmental Monitoring and Assessment journal. The study has been done by team of scientists led by Dr Durbar Ray which includes Ashwini D. Toraskar, Cathrine S Manohar, Charmaine L. Fernandes, Abigayle D. Gomes and Ajit Antony.
