Effect of physical stresses on survivability and post-exposure antibiotic susceptibility of coliforms in environmental waters and wastewaters

Background: Coliform bacteria are majorly introduced into water bodies (river and wastewater) as a result of faecal pollution, agricultural run-offs and several anthropogenic activities. Despite the effectiveness of water treatment methods, pathogens still persist in water; hence the relevance of assessing the ability of these pathogens to survive the lethal actions of physical stresses and the possible impact on antibiotic susceptibility pattern of the organisms. Methodology: The survivability of Escherichia coli strains (NCM3722, FAP1 and ST2747), Enterobacter cloacae GGT036 and Shigella sonnei 53G was assessed in environmental and waste waters for 21 days. The effect of three treatment regimens (UV radiation, solar radiation and boiling) on the survival of the coliforms was evaluated. Also, the antibiogram of the isolates post­UV exposure was assayed. Results: Although there was significant reduction (≥ 3-log) in the population of the bacteria overtime, all the coliforms survived in the waters for 21 days. The effect of UV radiation was significant on all organisms (> 3 log reductions). Solar radiation for 60 minutes had significantly lesser effect than boiling for 15 minutes. Surviving cells of all isolates demonstrated multiple drug-resistance post exposure to UV radiation. Conclusion: This study revealed the ability of coliforms to persist in waters after treatment and proves that UV radiation may not be effective in attenuation of antibiotic resistance

Antimicrobial Activities of Daucus Carota Seeds on Selected Pathogenic Micro-organisms

Background: The antibacterial/antifungal toxicity of Daucus carota (carrot) seeds was evaluated using selected multi-drug resistant bacteria and yeast of clinical origin. Methods: The active constituents of the Daucus carota seeds were extracted using conventional Plant Tissue Homogenization method using cold distilled water, Ethanol and Methanol as solvents. Varying concentrations (5-250 mg/ml) of the three extracts were assayed for antimicrobial activity against the selected isolates- Salmonella typhi, Staphylococcus aureus, Escherichia coli, Klebseilla pneumoniae and Candida albicans; the agar well diffusion method was used. The antibiogram profile of the organisms was also obtained through disc diffusion method. Results: Similar activity was observed in the methanolic and ethanolic extracts while cold distilled water showed no activity on any of the isolates. The antibiotic susceptibility results showed that the isolates used are highly multi-drug resistant. Ofloxacin exhibited the most pronounced activity against all the isolates. Gentamicin and erythromycin both showed activity on Escherichia coli and Salmonella typhi. Lower concentrations of both extracts presented no inhibitory effects on the test organisms, thus resulting in high MIC values recorded for both extracts. Also, the extracts showed no bactericidal action against the isolates.  Conclusions: Observations from this research therefore affirm that Daucus carota seeds possess antimicrobial properties that may be explored as a source of future antimicrobial compounds.