Distribution de Pseudomonas aeruginosa et Aeromonas hydrophila dans les eaux de la nappe phréatique superficielle en zone équatoriale au Cameroun et relations avec quelques paramètres chimiques du milieu.

Une étude microbiologique et chimique a été menée pendant un an sur les eaux de sources et de puits de Yaoundé (Cameroun). Les analyses microbiologiques ont été faites suivant la technique des membranes filtrantes, et les analyses chimiques, suivant les techniques analytiques usuelles. Les abondances maximales mensuelles de Pseudomonas aeruginosa et de Aeromonas hydrophila varient respectivement de 1 à 22x103 UFC.100 ml-1 d'eau, et de 1 à 7,8x103 UFC.100 ml-1. Ces abondances bactériennes subissent d'amples fluctuations spatio-temporelles. Les eaux de sources et de puits analysées sont faiblement bicarbonatées, douces et présentent une minéralisation faible à moyenne. Le pH varie de 3 à 5 et les concentrations en CO2 dissous, de 300 à 532 mg.l-1. Un bon nombre des caractéristiques chimiques de ces eaux est relativement stable au cours du temps, en dépit des fluctuations spatiales apparentes. Le degré de corrélation entre les paramètres chimiques et la dynamique d'abondance des bactéries isolées, est hétérogène. Cela est nettement plus marqué dans les eaux de puits, en raison des conséquences de l'exploitation humaine de ces eaux, à l'origine d'apports allochtones divers.bacteriological and chemical study was carried out on the waters of four springs and six wells over 13 months and 12 months, respectively, in the town of Yaounde and its environs in Cameroon. For these groundwater points the study analysed the importance of pH, electrical conductivity, dissolved oxygen and carbon dioxide, and some ions such as sodium, potassium, calcium, magnesium, chloride and bicarbonate, for communities of Pseudomonas aeruginosa and Aeromonas hydrophila. The two bacteria P. aeruginosa and A. hydrophila are considered opportunistic pathogens. Different groundwater points were chosen on the basis of their spatial distribution and the size of the human population using them. Microbiological analyses were carried out by membrane filtration and chemical analyses were performed using standard analytical techniques.It has been noted that the monthly maximum abundance of P. aeruginosa and A. hydrophila varies from 1 to 22 x 103 CFU per 100 ml and from 1 to 7.8 x 103 CFU per 100 ml of water, respectively. These bacteria are sometimes rare and their abundance undergoes spatio-temporal fluctuations. The studied waters are slightly bicarbonate and soft, with a low to average level of mineralisation. The pH varied from 3 to 5 and the concentration of dissolved CO2 from 300 to 532 mg/l. Most chemical characteristics were relatively stable with time, but exhibited apparent spatial fluctuations. The level of correlation between the chemical parameters and the abundance dynamics of P. aeruginosa and A. hydrophila is heterogeneous. Depending on the origin (well or spring) of water samples and minimising their spatial variations, samples were grouped into single biotopes (either mother well or mother spring) which were separated into compartments. A correlation test was then carried out using data obtained from 52 monthly-average samplings in the four compartments of mother-spring water, and using data obtained from 72 monthly-average samplings in the six compartments of mother-well water. From this it emerged (P < 0.001) that in springs increases in pH, electrical conductivity, and in concentrations of chloride, sodium, potassium, calcium, magnesium and dissolved oxygen favoured the development of P. aeruginosa and A. hydrophila. High concentrations of dissolved carbon dioxide reduced (P < 0.001) the abundance of these bacteria. In wells, the ecology of P. aeruginosa and A. hydrophila is relatively unstable in comparison with springs. The higher instability in well water is ascribed to an increase in the number of confounding factors, which make wells appear more vulnerable than springs. This leads to the multiplication of asymmetrical interaction networks affecting bacterial population dynamics

Pollution bactériologique des puits d’eau utilisés par les populations dans la Communauté Urbaine de Douala - Cameroun

Une étude bactériologique a été menée sur 588 échantillons d’eau prélevés dans 49 puits de 7 quartiers de la ville de Douala. Les quartiers ont été choisis suivant la typologie de l’habitat. Les analyses des coliformes ont été faites suivant la technique par inclusion en une couche, et celle des streptocoques par ensemencement dans les tubes à vis avec bouillon de Rothe. Les résultats montrent que ces eaux abritent de nombreuses bactéries pathogènes, coliformes fécaux et streptocoques fécaux. Leurs densités subissent d’importantes fluctuations spatiales et temporelles, et varient entre 200 et 29*105 UFC/100 ml pour les coliformes totaux et entre 30 et 44*103 UFC/100 ml pour les coliformes fécaux ; les streptocoques fécaux sont le plus souvent présents. Les facteurs de variation sont l’environnement du puits, l’entretien, le niveau de la nappe dans le puits, la situation géographique. Les puits les plus contaminés sont ceux qui sont situés à moins de 5 m des sources de pollution telles que les latrines à fond perdu, les dépôts sauvages des ordures ménagères, l’absence ou le traitement régulier de l’eau, le niveau superficiel de l’eau dans le puits. Les puits aménagés, c'est-à-dire munis d’un couvercle bien utilisé et d’une margelle en béton, avec une profondeur d’au moins 4 m, situés au moins à 15 m en amont d’une quelconque source de pollution et dont le traitement est régulier, présentent tous une eau de qualité beaucoup améliorée ; les contaminations fécales y baissent d’au moins 1000 unités. Les points d’eau non aménagés sont très nombreux et les fortes densités de germes dans ces eaux montrent de grands risques sanitaires à court terme pour les consommateurs.© 2009 International Formulae Group. All rights reserved.Mots clés: Zone urbaine pauvre, coliformes totaux, coliformes fécaux, streptocoques fécaux, eaux de puits

Microbiological water quality of the Mfoundi River watershed at Yaound\ue9, Cameroon, as inferred from indicator bacteria of fecal contamination

Using the membrane filtration technique to count total coliform (TC), fecal coliform (FC) and fecal streptococci (FS), the microbiological water quality of the Mfoundi River and four of its representative tributaries at Yaound\ub4e, Cameroon, was assessed for human use and contact. Sampling was conducted so as to examine the potential origin of fecal contamination and how rainfall affects the measured concentrations of indicators organisms. Our results revealed that waters were not safe for human use or primary contact according to the standards for water quality established by theWord Health Organization (WHO). Indeed, these waters exhibited high concentrations of TC (Mean \ub1 SD = 5.6 7 10\u2078 \ub1 2.5 7 10\u2076 CFU/100 ml), FC (Mean \ub1 SD = 6.8 7 10\u2075 \ub1 2.4 7 10\ub3 CFU/100 ml) and FS (Mean \ub1 SD = 7.3 7 10\u2075 \ub1 2.1 7 10\ub3 CFU/100 ml) that varied with the sampling sites and points. FC/FS ratio suggested that this contamination was more from warm-blooded animals than humans and correlation analysis points to the role of rainfall as a contributing factor, which enhanced the bacterial numbers detected. We conclude that there is a great potential risk of infection for users of waters from the Mfoundi River and its tributaries at Yaound\ue9.NRC publication: Ye

Significance and suitability of Aeromonas hydrophila vs. fecal califorms in assessing microbiological water quality

We examined the significance and suitability of Aeromonas hydrophila versus fecal coliforms in assessing microbiological water quality. For this, we used the membrane filtration method to simultaneously estimate the abundance level of A. hydrophila and fecal coliforms in waters from the Mfoundi river watershed at Yaounde\ub4, and compared how fluctuations in A. hydrophila abundance matched those observed with fecal coliforms index as an indicator of water quality in the system under study. Our results revealed that waters were not safe according to the standards for water quality established by the Word Health Organization (WHO). They also indicated the prevalence of A. hydrophila as compared to fecal coliforms, and suggested that water from the Mfoundi River and its tributaries could be classified as hypereutrophic based on the density of Aeromonas. Moreover, the spatial distribution of fecal coliforms and A. hydrophila exhibited similar trends within the different water bodies investigated, suggesting that A. hydrophila can be used as indicator of water quality in highly polluted waters. We concluded that waters from the Mfoundi River watershed at Yaounde\ub4 represent a great potential risk of infection for users, and foresee that the next challenge will be to determine, among other factors, the physico-chemical factors influencing the observed spatial distribution.Peer reviewed: YesNRC publication: Ye

Determinants of the avoidance behaviour of households to cope with unsafe drinking water: case study of Douala and Yaoundé in Cameroon

Despite the effectiveness of home water treatment methods, this practice is not yet widespread in many countries, including Cameroon. This study analyses the determinants of the avoidance behaviour of households to cope with unsafe drinking water in the cities of Douala and Yaoundé in Cameroon. The study is based on primary data collected in 2013 from a sample of 789 households in the two cities. The nested logit model is used for empirical analysis. The main findings of the estimated models are as follows: the decision to improve water quality decreases when the head of the household is a man and when there is no child in the household. Furthermore, it decreases when wealth and the level of education are low. In addition, the probability of using a given avoidance method decreases with its cost of adoption and increases with its perceived efficiency (that is, the favourable opinion on the quality of water after treatment). The implications for public policies are discussed in this paper