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Abstract
Abattoirs play a vital role in environmental pollution and negatively affect the health of people living around, and even those who some distance stay away from them through air, water and
food contamination. This study evaluated the bacteriological and physicochemical properties of abattoir effluent-contaminated soil
in Benin City, Edo state with a view to highlighting the associated environmental and public health impacts. Samples in this study were collected seasonally at different depths (2.5, 22.5 and 42.5cm) from four different abattoirs (Oluku, University of Benin, Ewah Road, and Dumez Road) in Benin City. Standard chemical analytical methods were used to evaluate the physicochemical
parameters while standard bacteriological methods were used to determine the bacterial load and identity. Antibiotic susceptibility pattern was determined by disc diffusion method, and plasmid
profiling (before and after curing) of selected resistant isolates were carried out using TENS method. . The physico-chemical analysis of soil samples revealed a pH range of 6.25 - 6.76, electrical conductivity varied from 89 -161 µs/cm, organic matter (9.10-13.30%), iron (37.22-140.29 mg/kg), and phosphorus (4.91 – 12.82 mg/kg) for contaminated soil. For control samples, pH
ranged between 6.28 and 6.90, electrical conductivity varied from 73 - 119 µs/cm, organic matter at 9.92 – 14.83%, iron (27.19 – 101.23 mg/kg), and phosphorus (5.22 – 12.88 mg/kg). Mean heterotrophic bacterial count (HBC) for contaminated soil in rainy season ranged 0.57×10 8 - 1.90×10 8 cfu/g, while that of dry season ranged 0.55×10 7 - 1.97×10 7 cfu/g. Topsoil layer
consistently showed higher bacterial load across seasons. Isolates obtained in this study included Bacillus subtilis, Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Proteus
mirabilis, Proteus vulgaris, Salmonella spp., Klebsiella spp., Enterococcus spp. and Alcaligenes spp. There was a seasonal shift of Proteus vulgaris isolated in dry season to P. mirabilis in the rainy season. Staphylococcus aureus was the most occurring isolate at 20.4% for the dry season and 21.2% in the rainy season. Bacillus subtilis and Klebsiella spp. exhibited the highest virulence. All isolates were sensitive to Imipenem, but none were sensitive to Ceftriaxone and Ceftazidime Bacillus subtilis, Escherichia coli, Klebsiella spp., and Pseudomonas spp. had Multiple
Antibiotic Resistance index (MAR) values of 0.6, 0.6, 0.5 and 0.4, respectively. Klebsiella spp., Pseudomonas aeruginosa and Bacillus subtilis were positive for Plasmid DNA while
Escherichia coli was negative for Plasmid DNA. After curing, the MAR index values decreased to 0.3 for Bacillus subtilis and Klebsiella spp., while that of Pseudomonas aeruginosa decreased
to 0.1. The presence of the pathogenic bacterial isolates in abattoir effluent-contaminated soil highlights significant environmental and public health concerns
food contamination. This study evaluated the bacteriological and physicochemical properties of abattoir effluent-contaminated soil
in Benin City, Edo state with a view to highlighting the associated environmental and public health impacts. Samples in this study were collected seasonally at different depths (2.5, 22.5 and 42.5cm) from four different abattoirs (Oluku, University of Benin, Ewah Road, and Dumez Road) in Benin City. Standard chemical analytical methods were used to evaluate the physicochemical
parameters while standard bacteriological methods were used to determine the bacterial load and identity. Antibiotic susceptibility pattern was determined by disc diffusion method, and plasmid
profiling (before and after curing) of selected resistant isolates were carried out using TENS method. . The physico-chemical analysis of soil samples revealed a pH range of 6.25 - 6.76, electrical conductivity varied from 89 -161 µs/cm, organic matter (9.10-13.30%), iron (37.22-140.29 mg/kg), and phosphorus (4.91 – 12.82 mg/kg) for contaminated soil. For control samples, pH
ranged between 6.28 and 6.90, electrical conductivity varied from 73 - 119 µs/cm, organic matter at 9.92 – 14.83%, iron (27.19 – 101.23 mg/kg), and phosphorus (5.22 – 12.88 mg/kg). Mean heterotrophic bacterial count (HBC) for contaminated soil in rainy season ranged 0.57×10 8 - 1.90×10 8 cfu/g, while that of dry season ranged 0.55×10 7 - 1.97×10 7 cfu/g. Topsoil layer
consistently showed higher bacterial load across seasons. Isolates obtained in this study included Bacillus subtilis, Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli, Proteus
mirabilis, Proteus vulgaris, Salmonella spp., Klebsiella spp., Enterococcus spp. and Alcaligenes spp. There was a seasonal shift of Proteus vulgaris isolated in dry season to P. mirabilis in the rainy season. Staphylococcus aureus was the most occurring isolate at 20.4% for the dry season and 21.2% in the rainy season. Bacillus subtilis and Klebsiella spp. exhibited the highest virulence. All isolates were sensitive to Imipenem, but none were sensitive to Ceftriaxone and Ceftazidime Bacillus subtilis, Escherichia coli, Klebsiella spp., and Pseudomonas spp. had Multiple
Antibiotic Resistance index (MAR) values of 0.6, 0.6, 0.5 and 0.4, respectively. Klebsiella spp., Pseudomonas aeruginosa and Bacillus subtilis were positive for Plasmid DNA while
Escherichia coli was negative for Plasmid DNA. After curing, the MAR index values decreased to 0.3 for Bacillus subtilis and Klebsiella spp., while that of Pseudomonas aeruginosa decreased
to 0.1. The presence of the pathogenic bacterial isolates in abattoir effluent-contaminated soil highlights significant environmental and public health concerns
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