Antibiogram Profile and Heavy Metal Tolerance of Bacteria Cultured from Soils Collected from Metal Scrap Dump-Sites Located in Benin City, Nigeria

Abstract

The study investigated the antibiogram profile and heavy metal

tolerance of bacteria cultured from soils collected from metal scrap

dumpsites in Benin City. Enumeration and characterization of

bacterial isolates were carried out using standard procedures. The

agar diffusion and Kirby-Bauer disc diffusion methods were used in

determining the minimum inhibitory concentration (MIC) and the

antibiotic susceptibility profile respectively. The total heterotrophic

bacteria count ranged from 12.50 ± 3.44 to 22.50 ± 8.12 (×103

cfu/g),

while the control sample has 34.50±11.57(×103

cfu/g), Six (6)

bacterial isolates were identified; Bacillus subtilis, Micrococcus sp.,

Arthrobacter sp., Corynebacterium sp., Pseudomonas aureginosa

and Escherichia coli. The Minimum inhibitory concentrations of the

various isolates ranged from 5 to 25mg/l. Lead and cadmium showed

the highest inhibition against bacterial isolates with MIC values

between 5 and 10mg/l except Pseudomonas aeruginosa which

tolerated cadmium at 15mg/l. Iron and zinc highly inhibited the

isolates with MIC values ranging from 10 to 25mg/l. The bacteria

isolates showed about 67% resistance to at least three test antibiotics

with a multiple antibiotic resistance index of 0.3. The presence of

resistant bacteria to heavy metal and antibiotics in the scrapyard

soils could be critical to the health of the nearby residents as the

scrapyard may act as a reserviour for the transmission of the

antimicrobial agents