Assessment of Physicochemical, Bacteriological Quality and Antibiotic-Resistant Bacteria in Groundwater Wells at Zawiyat Al-Mahjoub, Misrata

Abstract

Groundwater is the primary water source in Libya, yet its quality has deteriorated due to excessive extraction, lack of sewage infrastructure, and agricultural activities. In Zawiyat Al-Mahjoub, rising salinity, microbial contamination, and the emergence of antibiotic-resistant bacteria pose increasing public health risks. This study assessed the physicochemical properties, bacteriological quality, and antibiotic resistance profiles of groundwater wells in Zawiyat Al-Mahjoub, Misrata. Twenty wells from three geographical zones were sampled. Physicochemical parameters were analyzed following ASTM and WHO methods. Bacteria were isolated using selective differential media, and antibiotic susceptibility testing was performed using the Kirby–Bauer disk diffusion method according to CLSI guidelines. Electrical conductivity, total dissolved solids, hardness, sodium, and chloride exceeded WHO limits in most samples. Bacteriological contamination was detected in 70% of wells, yielding 25 bacterial isolates, including only 2 isolates of fecal E. coli. Several isolates showed high resistance to commonly used antibiotics, particularly Trimethoprim–Sulfamethoxazole (100%) and Ampicillin (88%). Groundwater in Zawiyat Al-Mahjoub is chemically degraded and microbiologically unsafe, with the presence of antibiotic-resistant bacteria representing an additional health concern. These findings highlight the urgent need for improved well protection and wastewater management strategies.