Physicochemical characteristics and antibiotic resistance patterns of enteric bacteria isolated from harvested rainwater (HRW) in Oraukwu, Anambra State, Nigeria

Abstract

infections temperature, colour, turbidity, DO, TDS, TSS, alkalinity, hardness, chloride, and some heavy metals of the water samples were examined using APHA method. Bacteriological analyses were performed using the membrane filtration technique. Colonies formed were counted and expressed in CFU/100mL. Enteric bacteria were enumerated and characterized by their morphological characteristics and biochemical tests. Axenic cultures of the isolates were further subjected to antimicrobial susceptibility testing (AST) using the modified Kirby-Bauer disc diffusion method, based on the guidelines by CLSI. Results revealed that physicochemical parameters and some heavy metals were within acceptable limits, except for Fe (0.01-0.72 mg/L) and Pb (0.01-0.25 mg/L). Total bacterial counts ranged from 1.2×104 to 6.8×104 CFU/100mL, indicating high contamination. Morphological characteristics revealed twelve (12) isolates of enteric bacteria, comprising Escherichia coli (41.67%), Salmonella sp. (33.33%) and Shigella sp. (25%). All the isolates exhibited 100% resistant to augmentin and tetracycline, but showed varying degrees of susceptibilities; E. coli to levofloxacin (60%), Salmonella sp. to ertapenem, imipenem, levofloxacin and nalidixic acid (100%), and Shigella sp. to ceftriaxone and ertapenem (100%). ‘First flush’ diverters are recommended to be installed within the water collecting system, in order to divert runoff from the rooftop after a period of no rainfall. Antibiotics which the isolates were susceptible to are recommended for the treatment of infections caused by these pathogens.