Title : Surveillance of multidrug resistant enterococcus faecalis in hospital and academic wastewaters- A Delhi-NCR case study

Background: Antimicrobial resistance (AMR) is an increasing public health and environmental concern, and wastewater from healthcare facilities may serve as an important reservoir and dissemination pathway for antimicrobial-resistant bacteria. This study investigated the occurrence and antimicrobial susceptibility patterns of Enterococcus faecalis and other bacterial isolates recovered from hospital-associated and non-hospital wastewater sources in the Delhi-National Capital Region (NCR), India.

Methods: A total of 120 bacterial isolates were recovered from wastewater samples and characterized by Gram staining, culture, biochemical testing, and antibiotic susceptibility testing using the Kirby–Bauer disk diffusion method. Six highly resistant isolates were further evaluated by minimum inhibitory concentration (MIC) testing using a 96-well microdilution assay. Descriptive statistical analysis was performed using GraphPad Prism.

Results: Of the 120 isolates, 85 (70.83%) originated from hospital-associated environments and 35 (29.17%) from non-hospital sources. Gram-positive bacteria accounted for 74 (61.67%) isolates. Among 12 E. faecalis isolates, 100% were resistant to gentamicin and ceftriaxone, 91.6% to azithromycin, and 83.3% to ampicillin. Ceftazidime resistance was observed in 41.7% of isolates, whereas ciprofloxacin showed the highest susceptibility (83.3%). MIC testing of six isolates resistant to all tested antibiotics demonstrated no inhibition even after 48 hours, indicating high-level resistance.

Conclusion: The findings demonstrate a substantial burden of antimicrobial-resistant bacteria, particularly multidrug-resistant E. faecalis, in wastewater from the Delhi-NCR region, with hospital-associated environments representing important potential hotspots. Routine environmental AMR surveillance, prudent antimicrobial use, improved wastewater treatment, and molecular investigation of resistance mechanisms are warranted to limit the environmental dissemination of resistant bacteria and associated public health risks.

Keywords: Antimicrobial resistance; Enterococcus faecalis; Multidrug-resistant bacteria; Wastewater surveillance; Environmental microbiology; Antibiotic susceptibility

To be updated shortly..