Search

A study aimed at evaluating the abundance and the diversity of staphylococci in surface and underground water points was carried out in the city of Yaoundé during the period from February to August 2020. The bacteria sought were heterotrophic bacteria aerobic mesophiles (BHAM) and staphylococci. They were isolated by the technique of surface spreading on a Petri dish on PCA (Plate Count Agar) and the membrane filter technique on Chapman mannitol medium (Mannitol Salt Agar), for BHAMs and staphylococci respectively. The bacteria isolated were identified by standard methods. Some abiotics parameters were measured according to usual analytical techniques. These analyses show that the abiotic variables have varied throughout from one sampling period to another and from one point to another. Thus, it was noted that the waters are acidic and not very mineralized. The high nitrogen and orthophosphate values recorded at all the sampling points testify to the richness of organic matter in the water analysed. Bacteriological analyses revealed that these waters harbor a high density bacterial microflora consisting of BHAM and bacteria of the genus Staphylococcus. In fact, concerning the BHAMs, their mean densities in CFU per 100 ml were 4, 42 and 4, 13 respectively in the Olézoa stream and the various wells. In addition, Staphylococcus aureus and Staphylococcus epidermidis are the different species of genus Staphylococcus found with an average density of 4, 26 log CFU/100 ml and 2, 79 log CFU/100 ml for Staphylococcus aureus and 1, 11 log CFU/100 ml and 2, 79 log CFU/100 ml for Staphylococcus epidermidis respectively in the Olézoa stream and the different wells studied in the Olézoa watershed. The densities of staphylococci in the wells were less abundant but more diversified than those in watercourse. Significant correlations were observed between these germs and parameters such as electrical conductivity, color, suspended matter, dissolved O2, dissolved CO2, PO43- and NH4+. The degradation of the quality of these waters is favoured by their proximity to the sources of pollution with sampling stations, the exogenous inputs and the poor maintenance of the wells. These waters without any treatment, are not recommended for human consumption according to the World Health Organization standards.

Escherichia coli (E. coli) is a bacterial indicator of sanitary and hygienic importance widely used in the evaluation of the quality of drinking water, mainly because they are easy to detect and enumerate in water. Its presence in water reflects a deterioration in water quality. The E. coli species is heterogenous in its biotypes, serotypes and lysotypes as in its ecology and its association with pathologies. Studies have reported several cases of infections, sometimes even fatal, caused by contact or consumption of water contaminated by pathogenic strains of E. coli. The detection of E. coli in surface water was shown in field studies to have significant information about the microbial quality of water contaminated with enteric pathogens. Studies using the properties of plant extracts for the inhibition of this bacterium have been widely carried out. Some studies show the potential exploitation of Artemisia annua, Eucalyptus microcorys and Moringa Oleifera extracts treatment of bacterio-contaminated water. The effect of some aqueous extracts on planktonic cells of E. coli in the planktonic and adhered state are summarized in this chapter.

The present work used multiple linear regression (MLR) models and corrgram to assess the importance of environmental parameters on diversity and abundance dynamics of Vibrio sp. in waters of few landing stages in the city of Douala (Cameroon). It was recorded in all the five selected stations, the presence of four species of Vibrio namely, Vibrio parahaemolyticus, Vibrio cholerae, Vibrio fluvialis and Vibrio alginolyticus whose highest abundance reached 5.65, 6.26, 4.9 and 4.83 log CFU/100 ml respectively. Vibrio cholerae was the most isolated during the study with a frequency of 65%. The abundance dynamics of these germs is strongly influenced by nitrates, salinity, dissolved carbon dioxyde (CO2) and ammonium ions (NH4+). The visualization of corrgram shows high degree of association between studied parameters. We note a coefficient of determination r2 = 0.50 for the multiple linear regression model for Heterotrophic Aerobic Bacteria (HAB) and a coefficient of determination r2 = 0.58 for the MLR model for V. cholerae. The physicochemical parameters explain at 43% (r2 = 0.43) the distribution of the abundances of V. parahaemolyticus, at 45% (r2 = 0.45) the distribution of abundances of V. alginolyticus and at 26% (r2 = 0.26) for V. fluvialis. Keywords: Multiple linear regression, visualization of corrgram, environmental parameters, distribution patterns, Vibrionaceae.

A study was carried out with the objective of evaluating the microbiological and physicochemical quality of surface water in the Nkolafamba subdivision, Center Region of Cameroon. Five sampling points were selected based on several criteria. The bacteria isolated were Mesophilic Aerobic Heterotrophic Bacteria (BHAM), bacteria that were witnesses to faecal contamination and Pseudomonas. Some abiotic parameters were measured using the usual techniques. The results show that some physicochemical parameters such as temperature was almost constant around 25 °C during the study period. There is also a pH which tended towards neutrality pH de (7,04 ± 1,03 U.C). However, it was noted that the stations are quite oxygenated (63,96%). Bacteriological analyzes revealed that an average value of 5.17 units (logUFC / 100mL) was recorded for BHAM. Overall, the abundances of total coliforms averaged 4.18 units (logUFC / 100mL). The waters of Nkolafamba also harbor a pathogenic microflora, with bacteria such as P. aeruginosa P. pasteurella, the abundance of which can sometimes reach 5,462 units (log CFU / 100mL). These germs can be the cause of eye infections or septicemia on users of these waters. These waters have a high bacterial load, and the microbiological pollution observed is predominantly animal. Some abiotic parameters such as pH, electrical conductivity, Suspended Solid (SS), nitrates and turbidity have influenced the distribution of these germs. The degradation of the quality of these waters is favoured by their proximity to sources of pollution, the runoff of contaminated water in the stations. These waters, without any treatment, are not recommended for human consumption according to the standards of the World Health Organization.Keywords: Abiotic variables, faecal coliforms, faecal streptococci, pathogenic bacteria, rivers.

Introduction: Foodborne resistant bacteria have become a challenge to food security. Milk and milk products are easy vectors of transmission of foodborne pathogens, these being the main sources of human infection by antimicrobial resistant pathogens. The present study aimed at making a comparative approach of the antibiotic sensitivity/resistance of 3 bacterial strains (Escherichia coli, Salmonella spp. and Brucella spp.) isolated from milk, drinking water and green fodder consumed by cows in the West Cameroon region (Central Africa). Methodology: A total of 48 raw milk samples, 48 water samples and 48 green fodder samples were collected during the year 2020 and subjected to culture and identification of Escherichia coli, Salmonella spp. and Brucella spp. Antibiotic susceptibility testing was performed using the antibiotic disc diffusion method. Results: Escherichia coli isolates showed high resistance (56-100%) to ampicillin, amoxicillin/clavulanic acid, cefotaxime, ceftazidime and ceftriaxone in all three samples. Salmonella spp. isolates showed resistance to ampicillin only (62, 67 and 67%). Brucella spp. strains isolated from raw milk and drinking water showed high sensitivity (78-100%) to azithromycin, doxycycline, ciprofloxacin, levofloxacin, gentamicin, rifampicin and trimethoprim/sulfamethoxazole, streptomycin and tetracycline. Antibiotic sensitivity/resistance to Escherichia coli and Salmonella spp. strains largely did not differ between samples (P>0.05). No difference in sensitivity/resistance (P>0.05) of Brucella spp. strains isolated from milk and water was observed with respect to the 10 antibiotics tested. Conclusions: The emergence of resistance to various antibiotics commonly used in medical and veterinary practices has important implications for public health. It seems necessary to strengthen of the regulations covering the sale and prescription of antibiotics.

International audience; This 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.

International audience; The health problems caused waterborne pathogens bacteria belonging to the Enterobacteriaceae family are aggravated by the rise of antimicrobial resistant bacteria phenomenon. This has been identified as one of the biggest global health challenges. The present study aims to make a comparative approach of the sensitivity/resistance to antibiotics of 4 Enterobacteriaceae Enterobacter cloacae, Citrobacter freundii, Salmonella typhi and Shigella sonnei isolated from wastewater, streams and groundwater in Yaounde town (Cameroon, Central Africa). Bacteria were isolated using standard methods their identification using the API 20E systems. The antibiogram tests were carried out using the Müller-Hinton antibiotic disc diffusion method. Results showed that inhibition diameters of antibiotic varied (P

A study was carried out in an aquatic microcosm with the aim of evaluating the importance of some chemical factors of the environment and some parameters intrinsic to cells, on the retention of bacterial contaminants in the aquatic environment on solid substrates. The rocky substrates used were sandstone, basalt, granite and micaschist. Four rocks with different petrographic and mineralogical structures. Bacteria isolated by standard techniques and used for adhesion testing were Pseudomonas aeruginosa, Vibrio cholerae and Enterococcus faecalis. These bacteria are rod, comma, and spherical in shape, respectively, and may or may not have a flagellum. In addition, this ciliature, when it exists, can be single or in a tuft and in a polar position or over the entire cell. The chemical parameters of the medium which varied were the pH, the concentrations of BOM and of salts. The incubation periods to allow the bacteria to adhere to the substrates ranged from 180min to 1440min. The adhered cells were then detached in sterile condition by introducing the rocks successively into 3 test tubes containing 10 ml of sterile physiological water (0.85% NaCl). It appears that bacteria contained in surface or groundwater can adhere to the surfaces of inorganic rocks at varying concentrations. The adhesion and retention of bacteria contributes to the natural purification of wastewater. P. aeruginosa, V. cholerae and E. faecalis adhered undergo temporal variations. Adhesion rates overall vary from 11 to 12.44x103 cells/cm2/h, with E. faecalis being the bacteria which adheres more quickly due to gravity alone. These variations of rates are linked to environmental conditions and to the chemical properties of rocks and soil. The presence of flagellum plays a dual role in approaching and relaunching the bacteria from the substrates.

International audience; The present study assessed the abiotic factors of Moringa stenopetala (M. stenopetala) extracts against Staphyloccoccus aureus in aquatic microcosm. Bacterial survival was assessed using colony forming unit (CFU) method on culture agar medium at different concentration levels (0.5 to 2 g/L). The incubation duration varied from 3 to 24 hours, and the temperatures were between 7°C and 44°C. Phytochemical screening showed that most of the constituents obtained from the extracts are the alkaloids, flavonoids and the tannins. It was observed that increase in extract concentration significantly inhibited the number of CFU obtained. Compared to the control {9.27 Log(CFU/100 mL)}, cells abundance from different concentrations of leaves extracts fluctuated between 4.74 and 0 {Log(CFU/100 mL)} after 3h incubation; 5.46 and 0 {Log(CFU/100 mL)} after 6h; 4.75 and 0 {Log(CFU̸/100 mL)} after 9h, and 4.85 and 0 {Log(CFU/100 mL)} after 24h incubation. As for root extracts, the abundance were between 4.80 and 0 {Log(CFU/100 mL)} under 7°C incubation; 5.03-5.23 and 0 {Log(CFU/100 mL)} under 23°C and 37°C, and 4.66 and 0 Log (CFU/100 mL) under 44°C incubation when considering the whole extract concentrations used. Incubation temperature and extracts concentration significantly impacted bacterial abundances. When the decoction extracts of roots were used, the amount of S. aureus cells inhibited was registered after 3-24 hours incubation. The Pearson correlation coefficient in most cases, revealed an inversely proportional relationship between the plant extracts and S. aureus cultured cells in a dose-dependent manner (P≤0.05). The use of M. stenopetala extracts could constitute an alternative in the treatment of water intended for human consumption.

International audience; A 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.

Microcosm experiments were carried out to investigate the effect of Eucalyptus microcorys aqueous plant extract on pathogenic Escherichia coli survival in water. The results clearly showed that the combined effect of light and extract concentration impacted significantly survival of the bacteria. The dark inhibition coefficient (KD) was 0.102 h-1, 0.116 h-1, 0.111 h-1, 0.123 h-1, 0.136 h-1 and 0.146 h-1 with 0.05%, 0.1%, 0.5%, 1%, 1.5% and 2% of extract concentration respectively. In the light conditions, we noted a relative increase of light inhibition coefficient (KL). The Self-Organizing Map according to incubation duration of cells in the extract solution permitted to group bacterial abundances in three clusters. Cluster I is the abundance of cells registered after 24 hours incubation in the plant extract solution. Cluster II is made up of all cells abundances registered after 9 and 12 hours incubation and Cluster III is constituted by cells abundances obtained after 3 and 6 hours incubation. Globally, for extract concentration 1, 1.5 and 2%, a calculation using Chick-Watson model resulted to a value of log(N/No) = -0.1Ct which is very close to chlorine disinfectant Chick-Watson model log(N/No) = -0.16 Ct. These results can improve in the new alternative method of treatment water by plant extracts.

An experimental study in aquatic microcosm was carried out to determine the major factors involved in the inhibition of Enterococcus faecalis in the presence of aqueous extract of Eucalyptus microcorys. The planktonic bacterial cells remained in various concentrations of the aqueous solution at light intensities which fluctuated between 0 and 3,000 lx and incubation periods which ranged from 3 to 24 hours. A hierarchisation of studied factors revealed that the aqueous extract concentration, followed by experimental temperature, light intensity and incubation duration influence the inhibition of E. faecalis cells, respectively, with a rate of 86.82%, 7.03%, 5.25% and 0.90%. The cell abundances dropped significantly at 1.5% (λ = 0.491 and F = 5.518) and 2% (λ = 0.568 and F = 4.055) concentrations coupled with 1,000, 2,000 and 3,000 lx. The highest light intensities and extract concentration produce the highest log removal values. The disinfectant properties of E. microcorys were evaluated by the Chick–Watson model. This Chick–Watson model so obtained varied between log (N/No) = −0.09 Ct and log (N/No) = −0.17 Ct for extract concentrations of 1, 1.5 and 2%. Aqueous extract of E. microcorys could be used for water disinfection.

Water is a key factor conditioning our lives and the minerals dissolved in it are one of the main sources of supplementing their deficiency. Water makes up about 60% of the body weight of an adult human, while the human body does not store water, which is why it is very important to permanently refill it. Without water, it would be impossible to have many processes in the body such as digestion, regulation of body temperature, proper mobility of joints or intrabody transport of nutrients and metabolic products. Water supplied to the body comes mainly from two distribution channels, as bottled water or water from the water conduit. In recent years, there has been a significant increase in the consumption of bottled water, which is the result of ubiquitous advertising of drinking water in this form. However, there is a group of consumers who drink tap water. The aim of the work was to compare the content of selected minerals in botteled waters purchased in stores and water from the water supply network. An attempt was made to answer the question whether the incurring of higher costs for the purchase of bottled water is justified in order to satisfy the body's needs for minerals or perhaps tap water meets these needs to a similar degree. Comparison of the content of selected mineral components in tap water and bottled water shows that in most cases tap water is not inferior to the content of the determined minerals in bottled water.

International audience

Escherichia coli (E. coli) is a bacterial indicator of sanitary and hygienic importance widely used in the evaluation of the quality of drinking water, mainly because they are easy to detect and enumerate in water. Its presence in water reflects a deterioration in water quality. The E. coli species is heterogenous in its biotypes, serotypes and lysotypes as in its ecology and its association with pathologies. Studies have reported several cases of infections, sometimes even fatal, caused by contact or consumption of water contaminated by pathogenic strains of E. coli. The detection of E. coli in surface water was shown in field studies to have significant information about the microbial quality of water contaminated with enteric pathogens. Studies using the properties of plant extracts for the inhibition of this bacterium have been widely carried out. Some studies show the potential exploitation of Artemisia annua, Eucalyptus microcorys and Moringa Oleifera extracts treatment of bacterio-contaminated water. The effect of some aqueous extracts on planktonic cells of E. coli in the planktonic and adhered state are summarized in this chapter.

The presence of pathogenic bacteria in drinking water poses serious health problems because of the persistence of water-borne diseases such as gastroenteritises, cholera and typhoid fever. These recent years, a detailed attention has focused on the disinfection of water by the use of plant extracts. The present study is to evaluate the impact of the aqueous extract of Eucalyptus microcorys plant on the cultivability of some bacterial species of medical health importance. In this study, The aqueous extract concentration of E. microcorys, contact time of bacteria in the extract solution, temperature of the extract solution, light intensity and the physical (planktonic and adhered state to the substrate) and metabolic (cellular growth phases) states of the bacteria cell, are the factors considered in various experimentation carried out in aquatic microcosm. The bacteria species used in this study were enteropathogenic and commensal Escherichia coli, Enterococcus faecalis, Salmonella typhi and Vibrio cholerae. In the first series of experimental tests, the planktonic bacterial cells remained in various concentrations (0.05 %, 0.1 %, 0.5 %, 1 %, 1.5 % and 2 %) of the aqueous solution of E. microcorys at incubation temperatures which varied between 7 and 44 °C, light intensities which fluctuated between 0 and 3000 lux; and incubation periods which ranged from 3 to 24 hours. For the second series of experimental tests, the adhered enteropathogenic E. coli cells, harvested from the different cellular growth phases, were incubated in the aqueous extract solution of E. microcorys for a contact time varying between 1 and 3 h.Phytochimical screening showed that alkaloids, anthraquinones, flavonoïds and saponins are the major components of the aqueous extract of E. microcorys. Whereas anthocyanines, gallic tannins, polyphenols and triterpenes are found in negligible quantity. Results of these experiments show that abundances of planktonic cells undergo a temporal variation dependent on the extract concentration and the incubation period. In most cases, the lower cell abundances were registered at a 44 C temperature of incubation. The lowest abundance of the enteropathogenic E. coli cells is 6.91 napierian logarithmic units (CFU/100 ml) obtained after 12 hours of incubation in 2 % extract solution concentration. The cell abundance of commensal E. coli and E. faecalis were 13.91 and 9.68 napierian logarithmic units (CFU/100 ml) respectively, registered at a 44°C incubation’s temperature, in 2% extract solution concentration, after 24 and 6 hours of incubation respectively. During the study, cells abundance has decreased with the increase of the incubation’s temperature, duration of incubation and the extract concentration; Cells being less affected in psychrophilous condition. Planktonic cells of enteropathogenic and commensal E. coli, S. typhi, V. cholerae and E. faecalis appeared to be relatively highly resistant to the antibacterial effects of E. microcorys aqueous extracts in psychrophilous condition. Inhibition’s percentage reaching 100 % were found at 37 °C and 44 °C incubation’s temperature. A negative and significant correlation (P

The presence of pathogenic bacteria in drinking water poses serious health problems because of the persistence of water-borne diseases such as gastroenteritises, cholera and typhoid fever. These recent years, a detailed attention has focused on the disinfection of water by the use of plant extracts. The present study is to evaluate the impact of the aqueous extract of Eucalyptus microcorys plant on the cultivability of some bacterial species of medical health importance. In this study, The aqueous extract concentration of E. microcorys, contact time of bacteria in the extract solution, temperature of the extract solution, light intensity and the physical (planktonic and adhered state to the substrate) and metabolic (cellular growth phases) states of the bacteria cell, are the factors considered in various experimentation carried out in aquatic microcosm. The bacteria species used in this study were enteropathogenic and commensal Escherichia coli, Enterococcus faecalis, Salmonella typhi and Vibrio cholerae. In the first series of experimental tests, the planktonic bacterial cells remained in various concentrations (0.05 %, 0.1 %, 0.5 %, 1 %, 1.5 % and 2 %) of the aqueous solution of E. microcorys at incubation temperatures which varied between 7 and 44 °C, light intensities which fluctuated between 0 and 3000 lux; and incubation periods which ranged from 3 to 24 hours. For the second series of experimental tests, the adhered enteropathogenic E. coli cells, harvested from the different cellular growth phases, were incubated in the aqueous extract solution of E. microcorys for a contact time varying between 1 and 3 h.Phytochimical screening showed that alkaloids, anthraquinones, flavonoïds and saponins are the major components of the aqueous extract of E. microcorys. Whereas anthocyanines, gallic tannins, polyphenols and triterpenes are found in negligible quantity. Results of these experiments show that abundances of planktonic cells undergo a temporal variation dependent on the extract concentration and the incubation period. In most cases, the lower cell abundances were registered at a 44 C temperature of incubation. The lowest abundance of the enteropathogenic E. coli cells is 6.91 napierian logarithmic units (CFU/100 ml) obtained after 12 hours of incubation in 2 % extract solution concentration. The cell abundance of commensal E. coli and E. faecalis were 13.91 and 9.68 napierian logarithmic units (CFU/100 ml) respectively, registered at a 44°C incubation’s temperature, in 2% extract solution concentration, after 24 and 6 hours of incubation respectively. During the study, cells abundance has decreased with the increase of the incubation’s temperature, duration of incubation and the extract concentration; Cells being less affected in psychrophilous condition. Planktonic cells of enteropathogenic and commensal E. coli, S. typhi, V. cholerae and E. faecalis appeared to be relatively highly resistant to the antibacterial effects of E. microcorys aqueous extracts in psychrophilous condition. Inhibition’s percentage reaching 100 % were found at 37 °C and 44 °C incubation’s temperature. A negative and significant correlation (P

International audience; The abundance dynamic of some freshwater invertebrates in relation with the abiotic factors of the medium was studied from March 2013 to March 2014 on the main streams of the Wouri and Sanaga basins. Individuals of Copepoda, Atyidae, Chironomidae and Physidae were collected, identified and counted. Samplings were carried out monthly; meanwhile measurements of the environmental variables were taken. Results of the physico-chemical analyses revealed that water of the Sanaga basin is globally well oxygenated (77%-92%) and faintly mineralized (14-107 µS/cm), excepted in the stations receiving household pollutants. Inversely, in the Wouri basin, waters are hypoxic with high content of organic matters (27.79 ± 9.43 mg/L). During rainy season (June-September), there is a dilution-dispersion of the organic matter due to stormwaters. Concerning biological analyses, the families of Physidae and Chironomidae were more abundant in urban stations than in stations situated in suburban area, especially during low water level period, showing that they are well adapted to anthropogenic and organic pollutions. The hypoxic conditions of urban waterways do not favor the proliferation of sensitive taxa such as Atyidae and Copepoda. These taxa preferred well oxygenated waters with rapid flow, and are more abundant during rainy season in stations located in suburban area or which are less subjected to anthropogenic disturbances.

The synergistic effects of the combined treatments of NaOCl and H2O2 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‰ H2O2 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/cm²)), respectively, under static and dynamic conditions after action of the mixture of disinfectants, whereas it reached 2.41 and 3.39 units (log (CFU/cm²)) after action of NaOCl and H2O2 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‰ H2O2 was used (P<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 (P<0.05). Although the Freundlich isotherm parameters relatively varied from one experimental condition to another, the Kf 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.

This study aimed to evaluate in microcosm condition, the survival of Aeromonas hydrophila and Enteropathogenic Escherichia coli (EPEC) , in the presence of M. oleifera aqueous seeds extract at concentrations varying from 1 to 40 g/L, and under 4 °C and 23 °C incubation temperature. It has been noted that cell abundances decrease gradually with the increasing in the seeds extract concentration. However, a marked cells regrowth was sometimes noted. In monospecies cell incubation condition, under 4 °C, the EPEC cells inhibition percentages (CIP) values varied from 52.12 to 99.84%. Those of A. hydrophila varied from 13.2 to 96%. The lowest CIPs were noted at the extract concentration 1g/L for EPEC and A. hydrophila . The highest CIP value was registered at 10 and 40 g/L for EPEC and at 15 g/L for A. hydrophila . Under 23 °C incubation, the EPEC CIPs values varied from 74.04 to 99.9% and those of A. hydrophila varied from 21.2 to 97.8%. For E. coli , the lowest and the highest CIP were recorded at the extract concentration 1g/L and 30 g/L, respectively. In bispecies cells incubation condition, the CIPs were relatively different. These results show the potential exploitation of M. oleifera extracts in the microbiological treatment of potable water.

The aim of this study was to determine the cultivability of E. faecalis and enteropathogenic E. coli (EPEC) under different light intensities in the presence of different concentrations of mercury chloride (HgCl2) and biodegradable organic compound (BOC). Studied light intensities were 0, 500, 1000, 1500 and 2000 lux while studied HgCl2 concentrations were 0.001, 0.01, 0.1 and 1μg/L. The BOC used was glucose at concentrations of 0.001, 0.01, 0.1 and 1mg/L and at pH 7. The BOC used was glucose at concentrations of 0.001, 0.01, 0.1 and 1mg/L and at pH 7. The duration of incubation under light was 6 h. Results showed that E. faecalis and EPEC bacteria are inactivated by HgCl2 irrespective of studied concentration. The cells inhibition percentage (CIP) of E. faecalis varied from 94.46% to 99.53% at 0.001μg/L, from 94.77% to 99.55% at 0.01μg/L, from 94.92% to 99.57% at 0.1μg/L and from 96.97% to 99.77% at 1μg/L of HgCl2. For EPEC cells, the CIP fluctuated between 89.87% and 98.99%, between 90.67% and 99.14%, between 92.05% and 99.14% and 93.50% and 99.25% respectively in solutions containing 0.001, 0.01, 0.1 and 1µg/L of HgCl2. The highest abundance was observed under 1500 lux for E. faecalis and 500 lux for EPEC. Exposure to light seemed to intensify the toxic action of HgCl2 in the medium. Cells metabolism reactivations under 2000 lux for E. faecalis and 1000 lux for EPEC were nevertheless observed. The level of this photo-reactivation varies from one organism species to another. The oligotrophic nature of the medium could not allow studied the microorganisms to set up specific protection mechanism against HgCl2 and light.

After cell adhesion processes in microcosm, the impact of sodium hypochlorite (NaOCl) and hydrogen peroxide (H2O2) on the detachment of Enterococcus faecalis from polythene fragments immersed in water under stationary and dynamic conditions was assessed. The abundance of planktonic cells was also evaluated. The density of E. faecalis adhered in absence of disinfectant fluctuated between 2 and 4 units (Log CFU/cm2). After living in disinfected water, the density of E. faecalis remained adhered to polythene sometimes reached 2 units (Log CFU/Cm2). This highest abundance of cells remained adhered was recorded with cells coming from the lag, exponential and stationary growth phases in water treated with 0.5‰ NaOCl. In H2O2 disinfected water, the highest value was recorded at all cells growth phases with 5‰ H2O2 concentration. Adhered E. faecalis cells have been sometimes completely or partially decimated respectively by NaOCl and H2O2 treated water. Considering separately each experimental condition, it was noted that increasing the concentration of disinfectant caused a significant decrease (P≤0.01) in abundance of cells stay adhered after living in water disinfected by the two disinfectants. Changes in disinfectant concentrations in different experimental conditions had an impact on the detachment of E. faecalis cells from the substrates.

International audience; Phytotherapy is increasingly used against infections in many parts of the world. Plants of the genus Artemisia, Asteraceae, are among those most exploited and several of its species were thus described as having antibacterial and antifungal effects. The infusions of Artemesia annua has been indicated as having disinfecting capacity in bacteriological contaminated water. The cultivability of Enterococcus faecalis and Escherichia coli was carried out in different extract solutions of A. annua aimed at describing the order of importance of some abiotic factors on this process. The bacterial abundance undergoes temporal variation with respect to pH of extract, A. annua extract and glucose concentrations, light intensity. The hierarchical organization of these factors has been carried out by expressing percentage and ranking in descending order of the sum of squares of each MANOVA test factor. It showed that cultivability of E. faecalis in A. annua extract solutions was influenced by the incubation durations, followed by the type of dilutions, light intensity, pH of extract, concentration of A. annua extract, and glucose concentrations. On the contrary, the cultivability of E. coli in A. annua extract solutions was influenced by the incubation durations, pH of infusion, type of dilutions, concentrations of A. annua extract, glucose concentrations and light intensity. The increase of the incubation durations, light intensity and pH of extract solutions caused a significant (P≤0.01) decrease of the effect of A. annua on E. faecalis and E. coli cultivability.

International audience; Synergistic 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.

International audience; The abundance dynamics of planktonic Vibrio cells and those associated with thefreshwater shrimps Atyidae were assessed in the coastal surface waters ofCameroon (Central Africa). Two pathogenic species V. parahaemolyticus and V.alginolyticus were identified. The concentration of Vibrio cells associated toshrimps was relatively high, as compared to the planktonic cells. Thisconcentration was very high during the great rainy season. The concentration ofVibrio associated with Atyidae undergoes variations under the effect of theproliferation of shrimps and influenced by color and rainfall. The physico-chemicalanalyses showed a strong organic pollution. Low nutrient levels suggested highwater column turnover rate, which Vibrio compensated for by using organicmatters leaking from shrimp. Stepwise regression analyses showed that theconcentration of plaktonic Vibrio cells increase significantly in response to changesto dissolved oxygen and organic matter accumulated in the water column due toanthropogenic activities. Vibrio associated with shrimp Atyidae in surface watersare a real risk of public health.

International audience; This study aimed to assess the inhibition of the commensally and enteropathogenic E. coli strains in aquatic microcosm under various concentrations of Eucalyptus microcorys leaves extract incubated under different temperatures. The extract concentrations were 1%, 1.5% and 2%. The incubation temperatures were 7°C, 23°C, 37° and 44°C. The abundance of the colony forming units (CFU) of each of the cell strains in the presence of Eucalyptus extract, decreased in most cases with respect to the increasing of the concentration of aqueous extract and the incubation temperature. The highest CAIRs were registered at 2% of aqueous extract for both cell strains. The highest CAIRs of the commensally E. coli strains were 4.176.h - 1 ,5.722.h-1 , 5.865.h -1 and 6.319.h -1 registered under the incubation temperature 7°C, 23°C, 37°C and 44°C respectively. For the Enteropathogenic E. coli strains they were 3.547.h -1 , 6.112.h -1 , 8.365.h -1 and 7.027.h -1 under the same incubation temperatures respectively. The cell inhibition percentage varied from one strains to another and with respect to the extract concentration and temperature incubation. With each E. coli strains, the highest cell inhibition percentage was registered under 37°C at 1%, and under 23°C and 37°C at 1.5% of the extract concentration. At the extract concentration 2%, the highest values of the inhibition percentages were noted with most of the incubations temperatures. A significant difference was noted between the inhibition rate of commensally and enteropathogenic strains (P

A 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 10x103CFU/100mL forSalmonella sp., 72x103CFU/100mL forStaphylococcus aureus, 102x103CFU/100mL forBrucella suisand 40x103CFU/100mL forBrucella 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 withSalmonella sp.andBrucella 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 withStaphylococcus aureusandBrucella abortus; this would be due to their tolerance to environmental stresses.&nbsp

The health problems caused waterborne pathogens bacteria belonging to the Enterobacteriaceae family are aggravated by the rise of antimicrobial resistant bacteria phenomenon. This has been identified as one of the biggest global health challenges. The present study aims to make a comparative approach of the sensitivity/resistance to antibiotics of 4 EnterobacteriaceaeEnterobacter cloacae,Citrobacter freundii,Salmonella typhiandShigella sonneiisolated from wastewater, streams and groundwater in Yaounde town (Cameroon, Central Africa). Bacteria were isolated using standard methods their identification using the API 20E systems. The antibiogram tests were carried out using the Müller-Hinton antibiotic disc diffusion method. Results showed that inhibition diameters of antibiotic varied (PE. cloacaestrain has been sensitive. The proportion of sensitive strains of other species varied between 5.88% and 23.53%. For the 2 aminoglycosides tested, 5.88% of the strains of each isolated species were resistant to gentamycin. Of the 3 quinolones tested, all strains ofE. cloacaeandC. freundiiisolated were fully resistant to Norfloxacin and of Ofloxacin. For the 3 Sulfonamides+trimethoprim, all strains ofC. freundiiandS. typhiisolated were resistant to Nurofurantoin and Fosfomycin. Most of bacteria strains isolated in wastewater and surface water were resistant to all the antibiotics tested. Many bacterial strains tested were multi-resistant. This multidrug resistance was more marked inE. cloacaeandC. freundiispecies isolated from wastewater and surface water. This represents a health risk for humans and the aquatic environment.