Diversity and Antibiotic Resistance of Bacillus spp. Isolated from Lake and Drinking Water of Udaipur city, India: Indication for One Health

In Udaipur, the lake water is treated and distributed throughout the city to ensure drinking water supply. However, Bacillus spp. may persist in treated drinking-water supplies due to their ability to form endospores, which are resistant to desiccation, heat, ultraviolet radiation, and many disinfectants. Antimicrobial resistance (AMR) is one of the key threats to public health, largely driven by antibiotic overuse and improper disposal. In this study, water samples (n = 90) were collected across all three seasons from various lakes (Fateh Sagar, Badi, Pichola, Rang Sagar, and Doodh talai) and localities of Udaipur and Bacillus spores were enumerated using the plate count method. The highest Bacillus spore count was recorded in summer, with Badi Lake consistently exhibiting the maximum count across all seasons. Characterization of Bacillus spp. was performed using morphological, biochemical, and 16 S rRNA sequencing. To the best of our knowledge, this study provides the first documented evidence of Bacillus infantis, Cytobacillus oceanisediminis, Cytobacillus kochii and Fictibacillus phosphorivorans inhabiting freshwater lake ecosystem. Four putative novel taxa, Bacillus subtilis (LB 8), Bacillus cereus (LB 65), Bacillus licheniformis (LB 56), and Bacillus cereus (LB 87) were identified. Maximum antibiotic resistance was found against β-lactam antibiotics, indicating the prevalence of putative extended-spectrum beta-lactamase (ESBL) producers. A significant portion of the Bacillus isolates (47.22%) were multidrug-resistant, and multiple antimicrobial resistance (MAR) indices of 92% of isolates exceeded the threshold value (0.2). The presence of AMR Bacillus in water raised concerns regarding the dissemination of resistant genes among potentially pathogenic bacteria. This research provides evidence to support recommendations against antibiotic abuse and the development of preventive strategies for maintaining water quality, emphasizing the necessity of integrating a One Health approach.