In the Shadow: The Silent Spread of Superbugs in Coastal Waters of Karachi, Pakistan

Marine microbial composition is primarily habitat dependent. Physical, chemical, and biological factors influence microbial communities. Human-driven changes are altering functional and phylogenetic diversity of bacterioplankton. Spread of superbugs or antibiotic resistant bacteria, in coastal water poses a major human health hazard driven by human activities. The aim of this study was to assess presence of microorganism, identification, dispersal and antibiotic resistance under different environmental conditions. 72 seawater and sediment samples were collected from nine survey sites at Karachi coast during monsoon season of 2022–2023. Samples were analyzed for dissolved oxygen, heavy metals, bacterial presence, taxonomic identification and antimicrobial susceptibility pattern. Outcome of analysis revealed increase in temperature (4.2 °C), salinity (2.4) and decrease in pH (0.28), dissolved oxygen (1.1 mg/L) from 2022 to 2023 monsoon season. Concentrations of Cd (0.056 ± 0.0023 mg/L) and Ni (0.058 ± 0.05 mg/L) were high in seawater comparable to acceptable limits (Cd = 0.01 mg/L and Ni = 0.02 mg/L) by untreated sewage and industrial effluent. In detailed laboratory examinations, bacterial load was found most abundant in creeks area of Korangi, Gizri, sandy beach of Village wall point, dispersed more during southwest season-2023. Fecal indicator species such as Escherichia coli (23.35%), together with Vibrio alginolyticus (18.27%) were exceeded permitted limit of international norms. These infectious species also exhibited the highest level of multiple antibiotic resistance (20–100%), most prominently against third generation antibiotics: Ceftizoxime, Cefepime, Ceftazidime. The study confirms hostile impact of untreated sewage and industrial discharge on bacterial community and replacing native bacteria with resistant pathogens across coastline.