Survival and Growth of Vibrio cholerae, Escherichia coli, and Salmonella Spp. in Well Water Used for Drinking Purposes in Garoua (North Cameroon).

The ability of strains of faecal bacteria (Vibrio cholerae, Escherichia coli ATCC 25922, and four strains of Salmonella isolated, resp., from well water, pig, poultry, and human urine in Garoua) to survive or grow in well water microcosms was compared. Water samples were obtained from two wells in Garoua (north Cameroun). Autoclaving at 121°C for 15 min and filtration through 0.2 µm filter were used to make microcosms. Microcosms were constituted of unfiltered-autoclaved, filtered-nonautoclaved, and filtered-autoclaved well waters. Bacterial strains were inoculated at initial cell concentration of 3 Log10CFU/mL. All strains were able to survive/grow in used microcosms, and a maximal concentration of 5.61 Log10CFU/mL was observed. Survival abilities were strain and microcosm dependent. The declines were more pronounced in filtered-nonautoclaved water than in the other microcosms. E. coli and Salmonella sp. (poultry strain) lowered to undetectable levels (<1 Log10CFU/mL) after two days of water storage. V. cholera decreased over time, but surviving cells persisted for longer period in filtered-nonautoclaved water from well W1 (1.91 Log10CFU/mL) and well W2 (2.09 Log10CFU/mL). Competition for nutrients and/or thermolabile antimicrobial substances synthesized by "ultramicrocells" or by the autochthonous bacteria retained by the filter might affect the bacterial survival.

Multiple contaminations of chickens with Campylobacter, Escherichia coli and Salmonella in Yaounde (Cameroon).

INTRODUCTION: Food-borne diseases associated with Campylobacter, Escherichia coli, and Salmonella are mainly caused by the consumption of raw or undercooked poultry meat. The objective of this study was to evaluate the prevalence of Campylobacter, Escherichia coli, and Salmonella in chickens. METHODOLOGY: One hundred and fifty chickens collected from eight retail markets in Yaounde were examined for the presence of Campylobacter, Escherichia coli, and Salmonella using standard bacteriological procedures. RESULTS: Of the 150 chickens collected, 135 (90%) were contaminated with Campylobacter (68.9% C. coli and 31.1% C. jejuni). All the chickens were positive for E. coli. Among the 150 isolates, 17 (11.3%) were enteropathogenic E. coli (EPEC). Additionally, 103 Salmonella strains were recovered from 90 chickens. Salmonella Enteritidis (45.6%) and Salmonella Hadar (28.1%) were the most frequent serotypes. Multiple contamination was found in 142 chickens (94.6%), of which 83 (55.3%) were concurrently contaminated with Campylobacter, Escherichia coli, and Salmonella. CONCLUSION: These results show that chickens in Cameroon are highly contaminated with Campylobacter, Escherichia coli, and Salmonella. The multiple contaminations of chickens is a potential risk of infection for consumers and highlights the necessity of public awareness for food safety.

Photoinactivation of Staphylococcus aureus and Vibrio parahaemolyticus in the model aquatic microcosm: effect of light intensity and dissolved biodegradable organic compound.

The impact of light (1,000 × 100,000 lx) on the inactivation of S. aureus and V. parahaemolyticus has been assessed under different concentrations of dissolved biodegradable organic compound (BOC) at pH 7.0. First, a gradual decrease in the number of cultivable cells was observed. Secondly, a cell reactivation was observed and it was marked in the absence of BOC. In the absence of BOC, the lowest value of cell inhibition rate (CIR) during the first 3 h was 0.138 h(-1) for S. aureus and 0.218 h(-1) for V. parahaemolyticus. In the presence of 10,100 and 1,000 mg/l of BOC, it was 0.196 h(-1), 0.243 h(-1) and 0.257 h(-1) for S. aureus respectively, and 0.285 h(-1), 0.306 h(-1) and 0.409 h(-1) for V. parahaemolyticus respectively. The CIRs values of each bacterial species significantly varied (P<0.001) with the changes in BOC concentration. In most cases, no significant difference was noted in the CIRs of both species when they were under the same light intensity and BOC. Nevertheless, it seems important to consider the impact of dissolved BOC during the treatment of bacterial polluted water.

Involvement of cell shape and flagella in the bacterial retention during percolation of contaminated water through soil columns in tropical region.

Microorganisms' retention in soil contributes to the natural purification of groundwater. Bacteria found in groundwater are generally of various shapes. The aim of this study was to assess the importance of cell shape and flagella in bacterial retention during polluted water percolation through two soil columns CA and CB, in the equatorial region in Central Africa. Percolation tests were carried out using different water loads samples which were contaminated by Escherichia coli (straight rods, peritrichous flagella), Vibrio parahaemolyticus (rods bacteria, polar flagella), and Staphylococcus saprophyticus (spherical, free-flagellum). It has been noted that showed that through soil column CA, the mean values of cells retention ratios (T(R)) varied with bacteria species considered, and from one applied water load sample to another. E. coli T(R) and that of S. saprophyticus were not significantly different (P> 0.05) for the two soil columns. V. parahaemolyticus T(R) significantly differed from that of E. coli and S. saprophyticus through soil column CA (P< 0.01) when the highest water load was applied, and through soil column CB (P< 0.05) for each of water load applied. A relative hierarchical arrangement of retained cells based on the T(R) showed that V. parahaemolyticus was less retained through the 2 soil columns. S. saprophyticus in most cases was more retained than others. The physical properties of the bacterial cell must be taken into consideration when evaluating the transfer of bacteriological pollutants towards groundwater.

Bionomics of Anopheline species and malaria transmission dynamics along an altitudinal transect in Western Cameroon.

BACKGROUND: Highland areas of Africa are mostly malaria hypoendemic, due to climate which is not appropriate for anophelines development and their reproductive fitness. In view of designing a malaria control strategy in Western Cameroon highlands, baseline data on anopheline species bionomics were collected. METHODS: Longitudinal entomological surveys were conducted in three localities at different altitudinal levels. Mosquitoes were captured when landing on human volunteers and by pyrethrum spray catches. Sampled Anopheles were tested for the presence of Plasmodium circumsporozoite proteins and their blood meal origin with ELISA. Entomological parameters of malaria epidemiology were assessed using Mac Donald's formula. RESULTS: Anopheline species diversity and density decreased globally from lowland to highland. The most aggressive species along the altitudinal transect was Anopheles gambiae s.s. of S molecular form, followed in the lowland and on the plateau by An. funestus, but uphill by An. hancocki. An. gambiae and An. ziemanni exhibited similar seasonal biting patterns at the different levels, whereas different features were observed for An. funestus. Only indoor resting species could be captured uphill; it is therefore likely that endophilic behaviour is necessary for anophelines to climb above a certain threshold. Of the ten species collected along the transect, only An. gambiae and An. funestus were responsible for malaria transmission, with entomological inoculation rates (EIR) of 90.5, 62.8 and zero infective bites/human/year in the lowland, on the plateau and uphill respectively. The duration of gonotrophic cycle was consistently one day shorter for An. gambiae as compared to An. funestus at equal altitude. Altitudinal climate variations had no effect on the survivorship and the subsequent life expectancy of the adult stage of these malaria vectors, but most probably on aquatic stages. On the contrary increasing altitude significantly extended the duration of gonotrophic cycle and reduced: the EIR, their preference to human blood and consequently the malaria stability index. CONCLUSION: Malaria epidemiological rooting in the outskirts of Western Cameroon highlands evolves with increasing altitude, gradually from stable to unstable settings. This suggests a potential risk of malaria epidemic in highlands, and the need for a continuous epidemiological surveillance.

Prevalence and antimicrobial resistance of Salmonella serotypes in chickens from retail markets in Yaounde (Cameroon).

From February 2006 to January 2007, 150 chickens were collected from eight retail markets in Yaounde, and 90 (60%) tested positive for Salmonella. Seventy-nine chickens were contaminated with only one Salmonella serotype, 10 with two different serotypes, and 1 with four serotypes. The most prevalent serotypes were Enteritidis (47 strains) and Hadar (29 strains). The isolates were tested for their susceptibilities to amoxicillin, amoxicillin/clavulanic acid, cefoxitin, cefotaxime, gentamicin, streptomycin, tetracycline, chloramphenicol, sulfonamides, nalidixic acid, ciprofloxacin, and trimethoprim/sulfamethazole by disk diffusion assay. Minimum inhibitory concentrations of ampicillin, streptomycin, tetracycline, sulfonamides, and nalidixic acid were determined for the resistant strains by agar dilution method. Eleven isolates (10.7%) of the 103 tested were susceptible to all antimicrobials. Resistance was most observed to tetracycline (84.5%), streptomycin (44.7%), and nalidixic acid (34%). Forty-one isolates (39.8%) were multidrug resistant (resistant to three or more antimicrobials from different classes), of which 68.3% were Hadar and 21.9% Enteritidis. The most frequent resistant pattern in Hadar was streptomycin-tetracycline-nalidixic acid. These results highlight once more the need for surveillance of Salmonella contamination in poultry.

[Measuring resistant forms of two pathogenic protozoa (Giardia spp and Cryptosporidium spp) in two aquatic biotopes in Yaoundé (Cameroon)]. / Evaluation de l'abondance des formes de résistance de deux protozoaires pathogènes (Giardia sp et Cryptosporidium sp) dans deux biotopes aquatiques de Yaoundé (Cameroun).

Organisms of the genera Cryptosporidium and Giardia are enteric parasites that are responsible for cryptosporidiosis and giardiasis respectively. They are characterised by profuse diarrhoea, abdominal pain and cramping. The symptoms can be fatal for immunodepressed subjects and children because these are opportunistic pathogens. These pathogenic infections are rampant in developing countries due to the unhygienic and improper disposal of wastewater and the use of surface water as the major sources of potable water. Little information is available about the resistant forms of these microorganisms in the hydrosystems of Cameroon in particular and other sub-Saharan ecosystems in general. The aim of this research was to isolate, identify, and measure these forms of these emerging protozoa in the waste and surface waters of Yaoundé, Cameroon. Giardia spp cysts were identified by Lugol iodine staining, and the Cryptosporidium spp oocysts by the Ziehl-Neelsen technique. The cysts were oval in structure and varied in length from 7 um to 12.0 um. Axostyles were visible along the median line and nuclei were present. The oocysts were round in structure and varied in diameter from 4 um to 6 um. A double cell wall was seen in the apicomplexa. The highest concentrations of Giardia spp cysts were 560 cysts/L in the surface water and 650 cysts/L in the residual effluent, while the corresponding figures for Cryptosporidium spp were 1,110 oocysts/L in the stream and 1,500 oocysts/L in the effluent. The cyst and oocyst counts were higher in the direct effluent because they are released directly into the wastewater by feces, while they are diluted in the surface water, reducing their abundance. Turbidity has a significant effect (p<0.05) on the population dynamics of these microorganisms, thereby indicating the importance of suspended or colloidal particles in the dissemination of these pathogens in aquatic media. The suspended particles in the wastewater adsorb the oocysts and cysts, probably because of the interactions between the electric charges carried by suspended particles and those present at the surface of the parasites. The positive correlation observed between these parasites and ammonia may account for some of the die-off of these resistant forms, because ammonium ions in water are known to inactivate trophozoites and sporozoites present in cysts and oocysts. This may be due to the permeability of the protozoan membrane to the ammonium ion and other alkaline earth metals present in aqueous form in the biotope. These parasite forms in these media represent a considerable health risk to the inhabitants of the study zone who depend on this surface water for drinking. The small size of these parasitic forms, the nonfunctional water purification stations and ineffective water treatment systems expose the community to outbreaks of giardiasis and cryptosporidiosis.

Shifts in microbial community functions and nitrifying communities as a result of combined application of copper and mefenoxam.

In this microcosm study, we focused on the effect of a combined application of copper and mefenoxam on the functional diversity of soil microbial communities. Treatments with combined and separate applications of copper and mefenoxam were sampled at 24 and 60 days and control soil was sampled at 0, 24 and 60 days. Structural and metabolic profiling of microorganisms were performed by arbitrarily primed (AP) and RNA arbitrarily primed-PCR (RAP-PCR). Cluster analysis resulted in separate grouping of AP and RAP-PCR profiles, with differences between control and treatments being more pronounced with respect to RAP-PCR profiles. amoA, a functional molecular marker for beta-subgroup ammonia-oxidizing bacteria, could only be detected at day 60 in treatments of mefenoxam, and mefenoxam+copper, with higher gene copies in the latter. There was also an increase in potential nitrification activity on application of mefenoxam and mefenoxam+copper. Comparison of amoA diversity was performed by denaturing gradient gel electrophoresis followed by construction of a clone library of amoA fragments amplified from the mefenoxam+copper-treated sample. Analysis of clones was performed by restriction digestion and subsequent sequencing. Patterns 1 and 5 were seen in 93% of the clones and clustered together with amoA sequences of Nitrosospira, indicating that Nitrosospira-like organisms are the major nitrifiers under mefenoxam treatments.

Sorption kinetics of Escherichia coli and Salmonella sp on two soil layers associated with a groundwater table in Yaounde, Cameroon (Central Africa).

A laboratory study has been carried out on two soil layers (H[X] and H[Y]) located above a groundwater table in Yaounde, Cameroon (Central Africa). The main purpose of this study was to assess the retention potential or sorption kinetics of Escherichia coli and Salmonella sp. on these soil layers. For both soil layers, bacterial sorption on soil particles occurred rapidly during the first 30 minutes of incubation of bacteria and soil particles in aqueous media, and increased gradually with incubation time up to 300 min. In some cases, adsorption rates fluctuated after 30 min of incubation, probably due to bacterial cell sorption to and de-sorption from soil particles. Using Freundlich isotherms, it was noted that adsorption coefficient related to adsorption capacity varied from 19 to 4026 E. coli.mg(-1) of soil, and from 506 to 847 Salmonella sp.mg(-1) of soil. For both bacterial species, the adsorption coefficient of layer H[Y] (located in close proximity of the water table) was greater than that of H[X] (located above layer H[Y]) and seemed to positively correlate with the pH values and N/P ratios, and to negatively correlate with the values of C/N and C/P ratios. The linearity coefficient related to adsorption intensity varied from 0.5841 to 1.0023 for E. coli, and from 0.7068 to 1.5236 for Salmonella sp. The physico-chemical characteristics of soil particles seemed to influence the sorption kinetics of bacteria on soil.

Antimicrobial resistance of Gram-negative bacilli isolates from inpatients and outpatients at Yaounde Central Hospital, Cameroon.

OBJECTIVE: To determine and compare antimicrobial susceptibility patterns of pathogenic bacteria from inpatients and outpatients at a university teaching hospital in Yaounde, Cameroon. METHODS: Gram-negative bacilli isolates (n = 522), obtained from a wide range of clinical specimens (urine, pus and blood) from inpatients and outpatients at Yaounde Central Hospital between March 1995 and April 1998, were evaluated for resistance to antibiotics (amoxicillin, amoxicillin/clavulanate, piperacillin, cefazolin, cefoxitin, cefotaxime, ceftazidime, aztreonam, imipenem, gentamicin, tobramicin, ofloxacin and trimethoprim/sulfamethoxazole). RESULTS: Of the 522 isolates recorded, 80.3% were Enterobacteriaceae. A high incidence of resistance to amoxicillin (85%), piperacillin (75%) and trimethoprim/sulfamethoxazole (71%) was observed. The proportion of antimicrobial-resistant isolates from inpatients was significantly higher than that from outpatients (P < 0.05), except for piperacillin, tobramicin and trimethoprim/sulfamethoxazole. The combinations of antimicrobial and organism showed that the percentage of ceftazidime-resistant Pseudomonas aeruginosa and ceftazidime-resistant Enterobacter cloacae were 26.8% and 24% respectively. The rate of antimicrobial resistance in isolates from inpatients was not significantly higher than that in isolates from outpatients for all the antimicrobial/organism combinations, except for ceftazidime-resistant Escherichia coli, which was exclusively found in isolates from inpatients. Among Enterobacteriaceae, high and low level penicillinase (mostly in E. coli (13.6% and 11% respectively) and Klebsiella spp. (9% and 8% respectively) were the most important beta-lactam resistance phenotypes (31.2% and 23.6%, respectively). Wild type (exclusively observed in E. coli, Proteus mirabilis and Salmonella spp.) and low level penicillinase were higher in outpatient than inpatient isolates (wild type--17.9% vs 10.8% and low level penicillinase--29.4% vs 20.5%, respectively; P < 0.05). However, extended spectrum beta-lactamase strains (Klebsiella spp. (3.5%), E. coli (2.6%), Citrobacter spp. (0.7%), Enterobacter spp. (0.4%) and P. mirabilis (0.2%)) were exclusively recovered from inpatients. Penicillinase and high level cephalosporinase resistance phenotypes were frequently observed in non-fermenter Gram-negative bacilli (46.6% and 29.1% respectively). However, there were no significant differences in penicillinase and cephalosporinase resistance between inpatient and outpatient isolates. CONCLUSION: As the incidence of antimicrobial resistance is substantially higher in isolates from inpatient than outpatient pathogens, more resources should be allocated within the hospital to encourage good antibiotic practices and good hospital hygiene.

Faecal coliforms and faecal streptococci community in the underground water in an equatorial area in Cameroon (Central Africa): the importance of some environmental chemical factors.

A bacteriological and chemical study was carried out within 1 year on spring and well water of Yaounde. It assessed the importance of some chemical factors on some faecal bacterial communities. The monthly average densities of faecal coliforms and faecal streptococci varied, respectively, from 1 to 72 x 10(2) CFU 100 ml(-1), and from 1 to 31 x 10(2) CFU 100 ml(-1) of water. These bacterial abundances undergo spatio-temporal fluctuations. These spring and well waters which are slightly bicarbonate, are acidic, soft, with low to average mineralisation. Most of the chemical characteristics of these waters are relatively stable with time, with respect to apparent spatial fluctuations. The degree of correlation between chemical parameters and the abundance dynamics of isolated bacteria is heterogeneous. In an artificially constituted spring biotope, the increase in pH, electrical conductivity, concentration of dissolved oxygen, chloride, sodium, potassium, calcium and magnesium favoured (P<0.01) the abundance of faecal coliforms and faecal streptococci. The high concentration of dissolved CO2 reduces (P<0.001) the abundances of these bacteria. They would nevertheless have developed such a mechanism allowing to minimise inhibitory effects of some environmental factors. In the well water, the ecology of faecal streptococci and faecal coliforms undergoes a relative instability, probably due to the variability of the resultant interaction network.