Bacteriology and genotoxicity of some pharmaceutical wastewaters in Nigeria
Wastewaters from two pharmaceutical production processes, cotrimoxazole B wastewater (BWW) and Piriton wastewater (PWW), were examined microbiologically and for physico-chemical parameters. Furthermore, the wastewaters were also screened for genotoxicity using Allium cepa assay to assess the risk associated with the discharge of untreated pharmaceutical wastewaters into the environment. The effluents induced various types of chromosomal aberrations, namely, disturbed spindle, vagrant and chromosome bridge, and also showed a dose-dependent reduction in the number of dividing cells. The mitotic inhibition ranged from 38.6 to 67.2%. The mean root length at 20% of BWW and all concentrations except 1% of PWW were significantly different from the control values (p < 0.05). The EC50 of the root growth inhibition was 4.17 and 12.45% for PWW and BWW, respectively. The wastewater physico-chemical analysis revealed that most parameters were within the allowable limits. The wastewaters had similar microbial load index of 107 cfu ml−1, indicating dense populations of bacteria, which may be due to the richness of the wastewaters in nutrients particularly sulphate, nitrate and phosphate. Coliform bacteria concentrations in the PWW and BWW wastewaters were 50MPN/100 ml and 550MPN/100 ml, respectively. The identified bacterial isolates included Staphylococcus aureus, Escherichia coli, Serratia marcescens, Klebsiella sp, Streptococcus pyogenes, Bacillus licheniformis, Yersinia sp, Proteus vulgaris and Bacillus subtilis. The resistance of the bacterial isolates ranged from 10% for gentamicin to 100% for augmentin, amoxycillin, cloxacillin and nalidixic acid. PWW isolates were more resistant. Seven patterns of multiple drug resistance ranging from 5 to 11 antibiotics were obtained amongst the isolates.
Keywords: Allium cepa, bacteria, environment, genotoxicity, multidrug resistance, pharmaceutical effluent, wastewater, Nigeria, untreated effluent, risk assessment, drug resistance, antibiotics