Recent Publication

Coastal Water Quality Degradation by Virulent and Antibiotic-Resistant Enteric Pathogens: Seasonal Patterns and Anthropogenic Drivers in the Jaffna Peninsula, Sri Lanka

Meddage Anjana Kelum Mithurangana Madhura Kumara , Pathmalal Marakkale Manage , Ganepola Arachchilage Pradeep Ruchitha Ganepola , Ponnamperuma Arachchige Kasun Chamara Wijerathna , Weiping Liu  and Shanshan Yin

More Info: https://www.mdpi.com/2073-4441/18/12/1519

Highlights

What are the main findings?

  • Jaffna coastal waters show persistent virulent enteric pathogen contamination across seasons.
  • STEC harbouring stx1, stx2, and eae genes were detected at multiple coastal and harbour sites.
  • Trimethoprim–sulfamethoxazole resistance was dominant; ciprofloxacin and piperacillin–tazobactam retained efficacy.
  • Faecal loading and nutrient enrichment are potential environmental factors influencing pathogen occurrence.
  • Virulence genes were detected at sites with low E. coli counts in both seasons.

What are the implications of the main findings?

  • Faecal indicator monitoring alone is insufficient to capture true coastal microbiological risk.
  • Seasonally adaptive, virulence-integrated surveillance frameworks are urgently needed.
  • The Jaffna coast is identified as a priority zone for integrated water safety and AMR management.
  • Findings support a replicable AMR surveillance model for low-resource settings.
  • Results align with SDG 3, SDG 6, and SDG 14 priorities.

Abstract

Tropical coastal waters are increasingly recognized as critical reservoirs for virulent, antibiotic-resistant enteric pathogens, yet seasonal dynamics governing their spatial distribution remain poorly characterized. We hypothesized that hydrological shifts and anthropogenic nutrient enrichment drive the seasonal distribution, virulence profiles, and antimicrobial resistance (AMR) of Escherichia coli, Salmonella spp., and Shigella spp. in the Jaffna Peninsula, Sri Lanka. Across 25 coastal sites during dry and transitional seasons, we integrated physicochemical water quality assessment, culture-based enumeration, PCR-based virulence gene profiling, Minimum Inhibitory Concentration (MIC) assays, GIS mapping, and statistical analyses. Key water quality parameters, including ammonium, nitrite, and total phosphorus, showed significant seasonal variation (p < 0.05), reflecting distinct hydrological regimes across seasons. A total of 220 E. coli, 200 Salmonella spp., and 100 Shigella spp. isolates were examined for virulence gene profiles and antibiotic tolerance. E. coli was detected at 80–88% of sites, Salmonella spp. at 72–88%, and Shigella spp. at 32–48%. Among E. coli isolates, stx1 was detected at 20–28% of sites and eae at 16% across both seasons. The stn gene was detected in Salmonella spp. at 12–28% of sites seasonally. Virulence profiling confirmed STEC harbouring stx1, stx2, and eae; Salmonella spp. carried stn; and Shigella spp. possessed invasion-associated genes. Trimethoprim–sulfamethoxazole resistance was recorded in 63.2% of E. coli, 33.0% of Salmonella spp., and 31.0% of Shigella spp. isolates at the lowest tested concentration of 4 µg/mL., while ciprofloxacin and piperacillin–tazobactam retained greater efficacy. Correlation analyses revealed significant associations among faecal contamination, nutrient enrichment, and virulence gene prevalence, implicating untreated sewage discharge and eutrophication as likely ecological factors associated with pathogen occurrence. These findings designate the Jaffna coastal zone as a significant reservoir of virulent AMR enteric pathogens, underscoring the urgent need for integrated One Health surveillance and seasonally adaptive coastal water quality management.

Occurrence and spatial distribution of Antibiotic-Resistant bacteria and antibiotic resistance genes in surface and groundwater of the Kelani River Basin, Sri Lanka

Authors: Meddage Anjana Kelum Mithurangana Madhura Kumara, Gayani Yasodara Liyanage, Fathima Sumaiya Idroos, Jayakodi Achchige Ganguli Vimansa Sewmi, Weiping Liu, Shanshan Yin, Rohan Goonetilleke, Rohitha Bandara, Lakmal Diyawaththege, Pathmalal Marakkale Manage
Abstract
Antimicrobial resistance (AMR) in aquatic environments represents a critical global public health threat, yet comprehensive environmental surveillance data remain scarce in low- and middle-income countries. The Kelani River Basin, supplying approximately 80% of Colombo’s potable water and Sri Lanka’s most industrially impacted waterway, lacks a basin-wide characterization of antibiotic-resistant bacteria (ARB) and antibiotic resistance genes (ARGs) across spatial and seasonal gradients. This study provides the first comprehensive basin-wide assessment of ARB distribution, ARG occurrence, minimum inhibitory concentrations (MICs), and multidrug-resistant (MDR) pathogen diversity across surface water and groundwater during wet and dry seasons. A total of 71 water samples (surface water: 53; groundwater: 18) were screened against ten clinically relevant antibiotics using standard pour-plate and agar dilution methods. ARG profiling was conducted using environmental DNA (eDNA)-based PCR, and MDR isolates were characterized by sequencing of the 16S rRNA gene. The transitional zone was identified as the principal contamination hotspot, with ARB loads significantly elevated during the wet season (p < 0.05). Phenotypic resistance was highest against cloxacillin (20.4%), amoxicillin (14.8%), and cefuroxime (14.4%), while ciprofloxacin and tetracycline exhibited the lowest resistance rates. MIC profiling revealed that 41.9% of isolates tolerated concentrations up to 600 µg/mL, with MDR isolates exhibiting MICs ≥ 540 µg/mL. MAR indices ranged from 0.1 to 1.0, with high MAR (≥ 0.5) predominant in dry (59.9%) and wet (43.5%) seasons. ARG screening detected sul1 (93%), qnrB (66.2%), mefA (43.7%), and blaCTX-M (23.9%) basin-wide across both water compartments. 16S rRNA sequencing confirmed clinically significant pathogens, including Klebsiella pneumoniae, Pseudomonas fluorescens, and Proteus mirabilis among high-level MDR isolates. Water temperature, total phosphorus, and nitrogen compounds were significantly associated with ARB abundance spatially and seasonally (p < 0.05). These findings reveal the Kelani River Basin as a high-risk environmental AMR reservoir, while delivering a low-cost, replicable surveillance framework for resource-limited settings to support evidence-based water quality policy and Sri Lanka’s National Action Plan for AMR.
More Info: https://link.springer.com/article/10.1007/s00284-026-04915-0

Environmental surveillance of antibiotic-resistant Escherichia coli in Sri Lankan inland waters: Detection of resistance genes and Shiga toxin–producing strains

Authors: Meddage Anjana Kelum Mithurangana Madhura Kumara, Gayani Yasodara Liyanage, Pavithrani Sadupama Manage & Pathmalal Marakkale Manage

Abstract 

The global rise in antimicrobial resistance (AMR) among environmental bacteria poses an escalating threat to public health, particularly in developing regions where antibiotic use in agriculture, aquaculture, and clinical settings remains poorly regulated. This study characterized antibiotic resistance patterns, virulence traits, and antibiotic resistance genes (ARGs) of Escherichia coli isolated from 24 major inland water bodies across Sri Lanka. A total of 120 isolates were recovered and subjected to susceptibility testing against seven clinically and agriculturally relevant antibiotics: amoxicillin (AMX), cloxacillin (CLOX), tetracycline (TET), oxytetracycline (OTC), piperacillin (PIP), cefotaxime (CTX), and ceftazidime (CAZ). Isolates were confirmed using standard biochemical tests and Gram staining, and minimum inhibitory concentrations (MICs) were determined via the agar dilution method (60 to 360 µg/mL). Multiple antibiotic resistance (MAR) indices were calculated to assess prior antibiotic exposure at each sampling site. PCR assays detected resistance genes (tetA, tetM) and virulence genes (eae, stx1, stx2). Widespread resistance was observed against AMX (100%) and CLOX (100%), while most isolates remained susceptible to the third-generation cephalosporins CTX and CAZ, suggesting the absence of extended-spectrum β-lactamase activity. MAR indices exceeded 0.2 across all sites, indicating pervasive prior antibiotic exposure. Resistance genes tetA (8.3%) and tetM (6.0%) were detected at moderate prevalence, consistent with widespread TET use in agricultural and veterinary contexts. Virulence genes eae and stx2 were absent; nevertheless, stx1 was detected in 2.0% of isolates from Minneriya Canal and Mahakandarawa Tank, indicating the presence of Shiga toxin–producing E. coli (STEC) with pathogenic potential. These findings demonstrate that Sri Lankan inland water bodies serve as critical reservoirs for ARG dissemination and potentially pathogenic strains, posing direct risks to communities dependent on these waters for domestic use, irrigation, and food production. Furthermore, this study provides a replicable methodological framework for future AMR surveillance studies in environmental and freshwater contexts. Systematic AMR surveillance, enhanced wastewater management, and targeted public health interventions are urgently needed, in alignment with One Health priorities and the United Nations Sustainable Development Goals.

More Info: https://link.springer.com/article/10.1007/s10661-026-15271-8

Kakunawela Pathirana Amaya Imanthi, Fathima Sumaiya Idroos and Marakkala Manage Pathmalal

published in Songklanakarin J. Sci. Technol.

Microbial Fuel Cell (MFC) is an environmentally friendly and sustainable technology where microbial degradation on organic substrates generates electricity, with potential application to wastewater treatment. This study mainly focused on investigating the effects of wastewater source on efficient electricity generation using a bio-cathode. Carbon cloth (2 × 4 cm2) were used as anode and cathode electrodes with 0.33Ω external resistor. Anode medium was leachate (setup 01) and rice wash water (setup 02) and cathode medium was Chroococcus sp. culture. Control setup was maintained by adding distilled water in cathode. Landfill leachate and rice wash water were used as the wastewater sources, all other conditions were the same in both setups. Highest electricity generation and wastewater treatment were recorded in setup 02 with rice wash water. The maximum voltage was 1,111 mV with current 3,366.67 mA and 467.55 mW m-2 power density. The wastewater treatment efficiencies reported as reductions in COD, Nitrate, Nitrite and Orthophosphate were 61.94%, 61.01%, 55.14%, and 26.01% in setup 02. These study outcomes disclose that dual chamber MFC with rice wash water as the wastewater source has potential for simultaneous power generation and wastewater treatment.