Background and Objectives: Waste water from abattoirs could harbour bacteria some of which are pathogenic. Therefore, this study aimed to assess the quality of wastewater from some abattoirs in Ilorin, Nigeria. Materials and Methods: The counts of viable bacteria, total coliform, faecal coliform, enterococci, S. aureus, P. aeruginosa and Salmonella/Shigella spp. of the wastewater was determined using selective media. The sanitary condition appraisal, antibiotic susceptibility test and plasmid profile of the isolates were assessed using standard methods. Results: The highest count of viable bacteria and total coliform obtained were 9.0 × 107 and 3.0 × 107 CFU/ml respectively. Faecal coliform and enterococcal count had the same highest value of 3.0 × 105  CFU/ml. The highest count of pathogenic bacteria: Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella spp. were 2.5 ×  108, 1.9 ×  107  and 3.0 × 104 CFU/ml respectively. The abattoirs sanitary scores ranged from 28.6-57.1%.  The isolates showed multiple antibiotic resis- tance (MAR) index ranging from 0.5-1.0. Plasmid curing with 0.1 mg/ml of acridine orange solution led to reduction in the MAR index of most of the Gram negative bacteria. Pseudomonas stutzeri was susceptible to all the antibiotics while Proteus vulgaris was resistant to all the antibiotics after curing. Most of the Gram negative bacteria isolated belong to the families Enterobacteriaceae and Pseudomonadaceae while the Gram positive bacteria belong to the families Staphylococcaceae, Enterococcaceae and Streptococcaceae. Conclusion: It was concluded from this study that wastewaters from the abattoirs were contaminated by bacteria with high MAR index. Most of these bacteria borne their antibiotic resistant factors in their plasmid.

Chlorination has been the method of choice for disinfecting water used for drinking purposes. However, some stressed bacteria during chlorination are able to recover and alter the potability of water. This study assessed the recovery of stressed bacteria in dechlorinated water. Ten chlorinated water samples were collected from different points within Ilorin metropolis, Kwara, Nigeria. The samples (100ml) were dechlorinated with 0.1ml of 11.4mM sodium thiosulphate solution. The physicochemical characteristics of the chlorinated water samples were determined while bacteriological analyses were carried out on both chlorinated and dechlorinated water samples. The antibiotic susceptibility pattern of the isolates was determined using disc diffusion method. The physicochemical characteristics of the water samples ranged as follow: pH 7.3-8.4, chloride content 4.37-6.85 mg/l, suspended solids 0.004-0.017 g/100ml, and total hardness 30-72mg/l. The chlorinated water samples had bacterial, total, and faecal coliform counts ranging from 1.0 × 101 – 1.9 × 104cfu/ml, 0 – 480 MPN/100ml, and zero, respectively. The dechlorinated water sample had corresponding counts of 5.4 × 102 – 7.36 × 104cfu/ml, 6 - 1100 MPN/100ml, and 0 – 380 MPN/100ml. A total of eleven bacterial species belonging to the genera Bacillus, Burkholderia, Citrobacter, Enterobacter, Enterococcus, Escherichia, Staphylococcus, Serratia, and Streptococcus were isolated. Not lower than 60% of the bacterial isolates were susceptible to ofloxacin and ciprofloxacin. All the isolates exhibited multiple antibiotic resistances.  The antibiotic resistance pattern of an isolate of Citrobacter freundii to cefuroxime, cefixime, and gentamycin changed remarkably and was plasmid-mediated, while that of E. coli and Enterobacter agglomerans remained unchanged to all the antibiotics and was non-plasmid mediated. Chlorination of water at the point of use is recommended. It is concluded that chlorination is essential in order to prevent reactivation of stressed bacteria during distribution and prevent infection by bacteria with high multiple antibiotic resistance index.

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