Carbapenem resistance exposures via wastewaters across New Delhi

Antimicrobial resistance (AMR) is a major global concern, especially in India where the burden of infectious diseases is high and health care spending is low. Here we quantified total coliform, faecal coliforms (FC), carbapenem-resistant enteric bacteria (CRE), bla_NDM-1, and three integron genes in samples collected from wastewater effluent of 12 hospitals, 12 sewage treatment plants (STPs), 20 sewer drains, and five locations along the Yamuna River in New Delhi over two seasons. Significant correlations were found between FC levels, CRE (r = 0.903, p = 0.004, n = 49) and bla_NDM-1 (r = 0.787, p = 0.003, n = 49) concentrations across all samples. Concentrations of coliforms, CRE, bla_NDM-1, int1, and int3 were highest in hospital effluents compared to other locations in both seasons. Although absolute concentration data indicate greater abundances of CRE and bla_NDM-1 in the winter, normalised data indicates greater carriage of bla_NDM-1 per cell in summer samples. In general, observed CRE levels were highest in surface water downstream of areas with higher population densities. Among CRE isolates (n = 4077), 82%, 75%, 71% and 43% of the strains from hospitals, sewer drains, river samples, and STPs, respectively, contained bla_NDM-1, implying STPs have relatively fewer bla_NDM-1 positive CRE in their effluents. The most common CRE isolates in the drains were Pseudomonas putida (39%) followed by Acinetobacter baumanni (20%) and Pseudomonas montelli (19%). The present scenario in New Delhi highlights the urgent need for increased coverage of appropriate waste treatment facilities across the city to reduce CRE exposures from polluted surface waters.