Investigating the types of bacterial species with antimicrobial resistance genes in Iran’s wastewaters: a systematic review

This systematic review shows that wastewater in Iran is a major but under-monitored reservoir for antimicrobial resistance (AMR). Analyzing 43 studies published between 1990 and 2024, the authors found widespread antibiotic-resistant bacteria (ARB) and resistance genes (ARGs) in hospital, municipal, and industrial wastewater, with research heavily concentrated in Tehran and limited coverage elsewhere.

Hospital wastewater carried the highest burden of clinically important resistance, including MRSA, VRE, and ESBL-producing E. coli. Municipal wastewater frequently contained resistant Enterococcus species, ESBL-producing E. coli, and MRSA, while industrial wastewater—especially from slaughterhouses—showed extremely high levels of ESBL-producing E. coli, sometimes exceeding 90%. Across all wastewater types, key resistance genes such as blaCTX-M, vanA, mecA, tetracycline genes, and intI1 were repeatedly detected.

Most studies relied on culture and basic PCR methods, with limited use of advanced tools like qPCR, molecular typing, or metagenomics. Overall, the review highlights significant gaps in national AMR surveillance and underscores the need for standardized, nationwide wastewater monitoring using modern molecular approaches to support effective One Health–based public health strategies in Iran.