Emergence of Hypervirulent, Multidrug‐Resistant <scp> <i>Klebsiella pneumoniae</i> </scp> Harboring <i>magA</i> in Coastal Water Sources: A Public Health Threat in Flood‐Prone Communities

Coastal flooding increasingly compromises water security while accelerating antimicrobial resistance through enhanced microbial gene transfer. In light of growing concerns over the widespread occurrence of multidrug-resistant Klebsiella pneumoniae in natural environments, we investigated the emergence and specific traits of classical and hypervirulent phenotypes of K. pneumoniae from domestic water sources in Cochin, India, a region frequently affected by flooding. Isolates were identified using 16S rRNA gene sequencing. Phenotypic characterization included the string test for hypermucoviscous traits, while antimicrobial susceptibility was determined via disc diffusion and microdilution. The ESBL production was confirmed using the combined disc diffusion test. Biofilm formation was quantified via the microtiter plate method with crystal violet staining. Finally, PCR was employed to detect key resistance (bla_TEM, bla_SHV, and blao_XA) and virulence (magA) genes. Findings revealed that 95% of the isolates were multidrug resistant, with 75% confirmed as ESBLs and 42% displaying hypermucoviscous phenotype. Resistance was observed against critically important antibiotics, including carbapenems and colistin, with the highest Minimum inhibitory concentration (MIC) values against ceftazidime and ampicillin (> 256 μg/mL). Hypervirulent strains exhibited significantly higher resistance levels and formed thicker biofilms compared to classical strains (p = 0.01) and highly correlated with multiple antibiotic resistance index (ρ = 0.90, p < 0.001), suggesting enhanced environmental persistence. Both phenotypes harbored key resistance genes (bla_TEM, bla_SHV, and bla_OXA), indicating a high potential for severe hard-to-treat infections. These findings underscore the urgent need for continuous environmental surveillance and One Health interventions to combat the rise of environmental hypervirulent K. pneumoniae and protect public health in flood-prone regions.