Role of Aged Zinc Oxide Nanoparticles on Loam Soil Physicochemical Properties and Antibiotics Susceptibility of Bacteria.

The role of aged zinc oxide nanoparticles on loam soil physicochemical properties and
antibiotic susceptibility of bacteria was assessed using standard microbiological methods. The
total heterotrophic bacterial counts (THBC) for the aerobic culture were 6.8 ± 0.2, 6.7 ± 0.2,
and 6.4 ± 0.2. Log10 CFU/g for 1000, 2000, and 4000 mg/kg ZnO nanoparticles respectively
compared to 7.2± 0.2 Log10 CFU/g in the control while the total heterotrophic bacterial counts
(THBC) for the anaerobic culture were 6.5 ± 0.8, 6.4 ± 0.7, and 6.4 ± 0.3 Log10 CFU/g for
1000, 2000, and 4000 mg kg⁻¹ ZnO nanoparticles respectively compared to 7.2± 0.4 Log10
CFU/g in the control. The organisms were members of the genera Bacillus, Corynebacterium,
Pseudomonas, Micrococcus, Enterococcus, Proteus, Staphylococcus, and Streptococcus. The
antibiotic susceptibility of microbial isolates against various antibiotics revealed distinct
patterns of sensitivity and resistance. Staphylococcus sp. was resistance to multiple
antibiotics, with the exception of Streptomycin and Erythromycin. Bacillus sp. was
susceptible, except to Streptomycin and Cefuroxime. Streptococcus sp. displayed
susceptibility to most antibiotics, except for Rifampicin, Levofloxacin, and Cefuroxime.
Proteus sp. and Enterococcus sp. were susceptible to all tested antibiotics. In contrast,
Pseudomonas sp. was resistant to all antibiotics except Ofloxacin and Augmentin, while
Clostridium sp. was resistant to all except Erythromycin. Zinc oxide nanoparticles altered the
physicochemical properties of loamy soil and also exerted concentration dependent