Mixture of Sodium Hypochlorite and Hydrogen Peroxide on Adhered Aeromonas hydrophila to Solid Substrate in Water: Impact of Concentration and Assessment of the Synergistic Effect

International audienceThe synergistic effects of the combined treatments of NaOCl and H 2 O 2 on the elimination of A. hydrophila adhered to polythene under static and dynamic conditions were evaluated. The concentrations 0.1, 0.2, and 0.3‰ NaOCl and 0.5, 1, and 1.5‰ H 2 O 2 were used. The contact periods were 180, 360, 540, and 720 minutes. The abundance of cells adhered reached 2.47 and 2.27 units (log (CFU/cm 2)), respectively, under static and dynamic conditions after action of the mixture of disinfectants, whereas it reached 2.41 and 3.39 units (log (CFU/cm 2)) after action of NaOCl and H 2 O 2 alone, respectively. Increase in the incubation period resulted in a significant decrease in the abundance of cells adhered when the mixture of 0.3‰ NaOCl and 1.5‰ H 2 O 2 was used (í µí± < 0.01). For each cell growth phase, there was a significant difference amongst the mean densities of cells adhered after action of the mixture of disinfectants (í µí± < 0.05). Although the Freundlich isotherm parameters relatively varied from one experimental condition to another, the í µí°¾ í µí± value registered in the exponential growth phase was relatively higher in static state than in dynamic regime; cells adhered under dynamic condition seem more sensitive to the synergistic action than those adhered under static condition

Synergistic effect of light, pH and Artemisia annua extract on Enterococcus faecalis in aquatic microcosms

International audienceSynergistic effect of abiotic and biotic factors is not completely established in the process of disinfecting water by plant extracts. The present study aims to evaluate the synergistic effect of different pH values (4, 5, 6, 7, 8 and 9) and different infusion concentrations (10, 20 and 30%) of Artemisia annua on Enterococcus faecalis growth in aquatic microcosm under dark and lighting conditions. The results showed that under dark condition, there was a relative increase in abundance of E. faecalis cells in the presence of A. annua extract. Under lighting, there is a decrease in the abundance of E. faecalis at different infusion concentrations of A. annua. Extract of A. annua seems to favour the growth of E. faecalis cells in the dark, especially at slightly acidic pH. This growth was relatively significant at pH 6. In the presence of light, A. annua extract inhibited the growth of E. faecalis cells and this varied from one extract sample to another; and was significant at slightly basic pH. Under the lighting, different pH values do not appear to have significant influence on the inhibition of bacterial growth except for pH 8. Monoterpenes, sesquiterpenes and triterpenes molecules present in infusions could be involved in chemical reactions responsible for cellular inhibition under light condition. Research on photosensitizing compounds and a comparative study with conventional photosensitizers might attest for the involvement of photosensitivity reaction with the A. annua extracts

Effects of aqueous and hydro-ethanolic Moringa oleifera Lam leaf extracts on the cultivability of 2 Bacillus strains isolated from rainwater

International audienceIn most developing countries, rainwater is used by many people to meet their water needs. Many Bacillus species known to be harmful to humans have also been identified in rainwater samples. Improving the microbiological quality of the rainwater using modern techniques seems expensivein rural areas for poor people. Extracts from several medicinal plants are often used in rural areas to treat certain bacterial infections. Water and alcohol are often used in traditional therapy to extract the principles of medicinal plants. But little is known about their functional differences orsimilarities. This study aims to assess the effects of aqueous and hydro-ethanolic leaf extracts of Moringa oleifera Lam on the cultivability of Bacillus cereus and Bacillus thuringiensis isolated from rainwater. Leaf extracts of concentrations 2, 1.5, 1 and 0.5 g/L in contact with cells were incubated at 23°C and 37°C for 3 h, 6 h, 9 h and 24 h. The results showed a decrease in cultivable cells abundance. In most cases, cell abundances between the aqueous extract and hydro-ethanolic extract were not significantly different (P>0.05). A significant difference (P<0.05) was noted amongst cell abundances from each incubation period to another. The effectiveness of each extract for cell inhibition was evaluated and then expressed as a decrease percentage in the number of cultivable cells. A decrease in cultivable B. thuringiensis abundance varied from 75.09 to 99.68% in hydro-ethanolic extract and from 70.75 to 97.94% in aqueous extract. That of B. cereus varied from 0 to 98.86% in hydro-ethanolic extract and from 41.09 to 92.20% in the other. This difference could be linked to the differences in the cell species intrinsic properties. It could also be linked to the presence of some compounds identified. Some of these compounds would act as nutrients for cell growth, counterbalancing cell inhibition caused by others that have antimicrobial effects

Relative importance of the bacteria Brucella, Salmonella, Staphylococcus and other indicator bacteria in some mountain farm waters in West-Cameroon (Central Africa) and the potential role of some environmental factors

International audienceA bacteriological and physicochemical study was conducted in the waters of farms in mountainous regions of Cameroon. The different water samples were collected during two campaigns in December 2018 and February 2019. Ten stations representing the drinking water supply points in our study area were identified. The results showed that these waters contained both pathogenic and commensal fecal bacteria. The highest abundances reached 10x10 3 CFU/100mL for Salmonella sp., 72x10 3 CFU/100mL for Staphylococcus aureus, 102x10 3 CFU/100mL for Brucella suis and 40x10 3 CFU/100mL for Brucella abortus. These abundances were subject to space-time fluctuations. Water contamination by tweezers was not general and was present only in surface waters (rivers and ponds). The water in the ponds, rivers and wells analyzed were all basic, with low mineralization on average. The dissolved oxygen ranged from 37.5 to 70.6%, nitrate from 3.7 to 19.8 mg/L and iron from 0.01 to 3.5 mg/L. Most of the physicochemical parameters were relatively stable during the two campaigns. The degree of correlation between the physicochemical parameters and the abundance dynamics of the isolated bacteria was heterogeneous. This was clearly more pronounced with Salmonella sp. and Brucella suis. This would be due to the fraction of metabolically active cells present when the bacteria are exposed to unfavorable conditions. Correlations with the abiotic factors were less marked with Staphylococcus aureus and Brucella abortus; this would be due to their tolerance to environmental stresses

Antibiotics susceptibility of some Bacillus strains isolated in the ground and rainwater in urbanized area in Cameroon (Central Africa), and potential impact of the season change

International audienceThis study assessed the antibiotics susceptibility of Bacillus cereus, B. thuringiensis and B. subtilis strains isolated in wells and rainwater samples in Yaounde (Cameroon). Water samples in wells were collected monthly during a long dry season (LDS), a short dry season (SDS), a long rainy season (LRS) and a short rainy season (SRS), and during the LRS and the SRS for rainwater. The antibiotics considered included Imipenem, Amikacin, Gentamycin, Ciprofloxacin, Ofloxacin, Sulfamethazol, and Tetracycline. With strains from the groundwater, the antibiotic inhibition diameters varied from 9.13 mm (Sulfametazole during SDS) to 32.78 mm (Imipenem during LDS) with B. thuringiensis, from 8.2 mm (Sulfametazole during SDS) to 35.25 mm (Imipenem during LDS) with B. cereus, and from 5.05 mm (Ofloxacin during LRS) to 29.25 mm (Imipenem during LDS) with B. subtilis. With those from the rainwater, they varied from 4.55 mm (Sulfametazole during LRS) to 25.65mm (Imipenem during LRS) with B. thuringiensis, from 2.13 mm (Imipenem during LRS) to 20.05mm (Imipenem during SRS) with B. cereus, and from 5.03 mm (Gentamicin during SRS) to 25.15mm (Tetracycline during SRS) with B. subtilis. Bacillus strains isolated during LRS were multiresistant to the majority of antibiotics. The inhibition diameters of the most antibiotics varied significantly from one season to another (p<0.05)

Minimum inhibition and bacterial concentrations of the plant Moringa Oleifera extracts against the bacteria Escherichia coli and Staphylococcus aureux

International audienceThis study aimed at assessing the MICs (Minimum Inhibitory Concentrations) and the MBCs (Minimum Bactericidal Concentrations) of the methanolic extracts from 4 different parts (leaves, seeds, stem, roots) of the plant Moringa oleifera against the bacteria E. coli and S. aureus. Phytochemical profile of each extract has been determined using LC/MS analyses. Microbial analyses were done using 96-wells plate method. Results showed that the four parts on the plants contain heterosides and glucosinolates. Iridoids were found in leaves, stem and roots. Flavonoids were found in leaves and stem. Phenolic acids were found only in leaves and carboxylic acids found only in stem. The abundance and the number of identified compounds of a given class varied from one part of plant to another. The MICs and MBCs varied with respect to the microorganism and the part of the plant. With E. coli, the MICs varied from 0.009 (leaves) to 1.25 mg/mL (seeds), and the MBCs varied from 0.156 (leaves) to 2.5 mg/mL (seeds and stem). With S. aureus, the MICs varied from 0.009 (stem and roots) to 0.039 mg/mL (leaves and roots), and the MBCs varied from 0.078 (leaves) to 4 mg/mL (stem). The bactericidal or bacteriostatic properties of the extracts varied depending on the part of the plant and the microorganism considered. Against E. coli, the leaves, stem and roots extracts were bacteriostatic whereas seeds extract was bactericidal. Against S. aureus, the seeds, stem and roots extracts were bacteriostatic whereas leaves extract was bactericidal