Identification of yeasts present in artisanal yoghurt and traditionally fermented milks consumed in the northern part of Cameroon

Bacteria generally ferment milk but, sometimes, yeasts are found in fermented milks. The presence of these yeasts in the microbial community of some fermented milks could be intentional or accidental. The Diversity of yeasts in the products was investigated using a molecular technique employing variable regions of 26S rDNA profiles generated by PCR-DGGE (Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis). Two types of samples: artisanal or handcraft yoghurt and traditionally fermented milks were collected in three towns of the three regions of the northern part of Cameroon. Firstly, a comparison was made between the 16 traditionally fermented milks collected in Maroua, Garoua and Ngaoundre each of the 3 regions. Secondly, it was between 26 artisanal fermented milks of each region and finally, between the two types of products. The different PCR-DGGE 26S rDNA profiles obtained were analyzed and DNA sequencing was used to compare yeasts from each method of production. Twelve (12) species of Yeasts were identified as: Malassezia globosa, Hanseniaspora uvarum, Galactomyces candidum, Candida tropicalis, Aureobasidium pullulans, Torulaspora globosa, Saccharomyces cerevisiae/paradoxus, Pichia kluyveri, Candida parapsilosis, Torulaspora delbrueckii, Kluyveromyces marxianus, Candida orthopsilosis and Pseudozyma sp. Yeast diversity was higher for artisanal fermented milks (yoghurt) with at least 10 species, while for traditionally non packed fermented milks only 5 species were identified with a predominance strain of Galactomyces candidum, Candida parapsilosis, Torulaspora delbrueckii, Saccharomyces cerevisiae/paradoxus and Kluyveromyces marxianus. The different species of yeast might be introduced accidentally in artisanal yoghurt; however, for traditionally fermented milks their presence might be associated to the starter

Comparison of bacterial communities of tilapia fish from Cameroon and Vietnam using PCR-DGGE (polymerase chain reaction-denaturing gradient gel electrophoresis)

Fishes in general and tilapia in particular are traded all over the world. However, it is difficult to find out their exact geographical location. One of the techniques used in the traceability of fish and its byproducts consist in analysing in a global way the whole viable and non viable bacterial communities. For this purpose, the molecular technique employing the bacterial 16S DNA banding profiles generated by PCR-DGGE (polymerase chain reaction-Denaturing gradient gel electrophoresis) was used to evaluate the differences between the bacterial profiles of fishes from Vietnam (An Giang, south province) and those of Cameroon (Yagoua, Maga, Lagdo). The different PCR-DGGE 16S rDNA banding profiles obtained were analysed and results showed that there were specific bands for each geographical location though some bands common to Cameroon and Vietnam were observed. This method could be used as a rapid analytical traceability tool for fish products and could be considered as a provider of a unique biological bar code. (Résumé d'auteur

Microbiological quality of lettuce (Lactuca sativa) consumed on the streets of Maroua (Cameroon: Effect of disinfecting agents used by some vendors

This study was carried out to determine and compare the microbiological quality of lettuce (Lactuca sativa) from market (unwashed) and those ready to eat in Maroua. The results revealed that 92.3% of lettuce vendors in Maroua, used Chlorine and 7.7% used potassium permanganate as cleaning method. The microbial concentration of lettuce varied from one vendor to another. Total flora ranged from 2.3 to 4.9 Log CFU/g for unwashed samples and from 2 to 4.51 Log CFU/g for washed samples; fungi counts were comprised between 0.76 to 2.65 Log CFU/g for unwashed samples and 0.26 to 2.17 Log CFU/g for washed samples; total coliforms ranged from 2.84 to 3.60 Log CFU/g for unwashed, and 0.26 to 3.00 Log CFU/g for washed lettuce; fecal coliforms ranged from 1.29 to 3.60 Log CFU/g for unwashed samples and 1.70 to 3Log CFU/g for washed samples. These results show also that Vibrio spp. was found amongst the 69% of unwashed samples, but was absent in all the washed samples. Salmonella spp. was present in 85% samples of unwashed lettuce, but absent in washed samples. The results revealed also that; there was a significant difference between the bacterial concentration of unwashed and washed lettuce samples (P<0.05). Most of the analysed samples (92%) composed of washed and unwashed samples were not satisfactory for consumption. (Résumé d'auteur

Characterization of the bacterial flora of tilapia (Oreochoromis niloticus) harvested from four lakes in the north of Cameroon

The aim of this study was to investigate the presence of Aeromonas spp., Vibrio spp. and Plesiomonas shigelloides in Cameroonian tilapia.120 samples of tilapia were collected from June to December 2005 in four localities in the north of Cameroon and were delivered to the laboratory in cool boxes. For the sample preparation to isolate the bacteria, 50 g of sample (gills, intestine and skin of individually fish) were taken using a sterile scalpel. These 50 g were homogenized in 450 ml of sterilised peptone solution. After 18 h of incubation, the homogenate sample was inoculated on thiosulphate citrate bile salt sucrose (TCBS) using an inoculation loop and incubated at 37°C for 18 to 24 h. The isolated colonies were subjected to morphological, physiological and commercially available API kits tests. In addition, the antimicrobial pattern of the identified strains to ten different antibiotics was studied using the agar disk diffusion method. The results obtained from this study show the presence of bacterial species belonging to Aeromonas spp. (n=39), Vibrio spp. (n=41) and P. shigelloides (n=14). The results of antimicrobial susceptibility show that the highest rates of resistance was found in ampicillin (100% of isolates), nitrofurantoin (more than 68% of isolates), association of trimethoprim and sulfamethoxazole (51% of isolates) and sulfamide (46 % of isolates). This work therefore highlights an important incidence of Aeromonas spp., Vibrio spp. and P. shigelloides with potential antimicrobial resistance, isolated from tilapia in four localities of Cameroon. (Résumé d'auteur

Influence of technological treatments on bacterial communities in tilapia (Oreochromis niloticus) as determined by 16S rDNA fingerprinting using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE)

Food quality and safety are major concern among consumers throughout the world in the context of globalization. Hence, the origin and the history of a food item are of prime interest when food quality is questioned. Precise determination of contamination source relies on the use of efficient and reliable methods. This study was carried out to assess the microbial ecology of fish upon technological treatments using 16S rDNA polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) fingerprinting. Samples of tilapia from Montpellier (South-east of France) and Yagoua (far north of Cameroon) were used for this purpose. The technological treatments applied on fillets were marinade, drying, smoking and deep-freezing. When the 16S rDNA profiles were analysed by multivariate analysis, distinct microbial communities were detected. The band profiles of fish bacteria after each treatment were different and specific. Technological treatments applied on fillets from Montpellier did not have an effect on the biological markers present on the fillets. These bands could be used as specific markers for this region. One of the treatments, the marinade applied on the samples of Yagoua induced the disappearance of some bands on the DGGE profile. In spite of treatment applied on samples, it is possible to recover the geographical origin by using DNA of the bacterial community in fish even if it was treated. (Résumé d'auteur

Research of some physicochemical and biological pollution indicators in four fisheries of the northern part of Cameroon

The bacteriological and physicochemical characteristics of water and sediment collected in four fisheries situated in the north of Cameroon were evaluated. In these locations, all the analysed parameters (temperature, pH, salinity, conductivity, turbidity, suspended matter, organic matter, phosphates, sulphates, nitrates, chloride, calcium, magnesium, iron and nitrogen) were the highest, except for chlorides. Total mesophile aerobic flora varied between 1.4±0.50×105 in Tibati and 5.57±0.50×106 CFU/mL in Lagdo. Salmonella concentration was comprised between 66.66±1.62 in Tibati and 274±3.16 CFU/mL in Yagoua. There was about 10±0.50 CFU/mL Vibrio in Lagdo and 342.27±5.53 CFU/mL in Maga. Staphylococcus concentration was between 1.4±0.55×103 CFU/mL in Tibati and 4.44±0.9×104 in Maga. Clostridia were comprised between 0.33±0.00 in Tibati and 226.66±4.29 CFU/mL in Maga while Pseudomonas concentration was comprise between 16.26±0.70 in Tibati and 326.66±6.00 CFU/mL in Lagdo. Faecal Streptococcus varied between 0.33±0.00 in Tibati and 238.66±8.15 CFU/mL in Yagoua. The total mesophile aerobic flora was significantly high (P&lt;0,005) in Lagdo while Clostridium, faecal streptococcus, and Streptococcus concentration were significantly high in Maga, Yagoua and Lagdo. Lake's sediments in Maga were the most infected. The different analysis revealed that the fisheries were relatively polluted. Some of the bacteria counted like Pseudomonas and Vibrio might be pathogenic for fishes. (Résumé d'auteur

Fungal llora and ochratoxin a associated with coffee in Cameroon

Aims: 104 samples were collected from the west region and the coastal plain of Cameroon during two coffee campaigns, 2009 and 2010. Two coffee processes were evaluated (wet and dry processes) at different stages from harvesting to storage. Study Design: Food contaminants. Place and Duration of Study: Food Microbiology Laboratory, Department of Food Science and Nutrition (ENSAI) University of Ngaoundere; UMR 95 Qualisud, CIRAD of Montpellier, between May 2009 and September 2012. Methodology: Fungi profile was evaluated by direct plating techniques and identified using morphological and molecular tools. OTA levels were analyzed using HPLC technique after extraction and filtration using an immunoaffinity column. Results: Results obtained revealed an overall percentage of fungal contamination between 60-92% in 2009 and 70-90% in 2010. There was no ecological difference in the composition of ochratoxigenic species present in five sites. Coffee beans sampled in 2009 had a colonization incidence of 18-40% A. carbonarius, 12-22% A. niger, 3-15% A. ochraceus while those of 2010 had a colonization incidence of 15-30% A. carbonarius, 35-40% A. niger, and 2-7% A. ochraceus. Fungal diversity was not correlated with the geographical origin, coffee cultivar and processing method. There was no difference between the processes studied in terms of occurrence of ochratoxigenic fungi. OTA levels were mostly below the recommended standards although some isolated cases of extreme contamination were observed in 2009. A higher level of OTA was detected in the presence of A. niger, A. carbonarius and A. ochraceus than when only A. niger was present. Conclusion: The important fungi with the potential to produce OTA in Cameroonian coffee beans are A. carbonarius and A. niger. These two species were predominant on each type of coffee beans. It was also observed that once a toxigenic strain was isolated from a coffee sample, the sample contained OTA. (Résumé d'auteur

Geological context of the Boumnyebel talcschists (Cameroun): Inferences on the Pan-African Belt of Central Africa Le contexte géologique des talcschistes de Boumnyebel (Cameroun) : implications pour la chaîne panafricaine d'Afrique centrale

International audienceThe talcschists of the Boumnyebel area (southern Cameroon) form ≤ 30 m thick discontinuous layers within a Pan-African nappe unit (Yaoundé group), which includes, at the base, muscovite + biotite ± garnet micaschists associated with amphibolites and pyroxenites, and, at the top, muscovite + biotite + garnet + kyanite micaschists locally associated with marble and amphibolites. The metamorphic peak (not, vert, similar650 °C/9.5 kbar; ca. 620 Ma) postdates nappe emplacement. Isograds are in normal position, micaschists passing downwards to migmatites in the northwestern part of the area studied. The rock types in the lower part of this nappe suggest active margin environments with detrital input from a nearby continental crust (arc or back-arc context)

Determination of coffee origin by using 28S rDNA fingerprinting of fungal communities by PCR-DGGE: Application to the Cameroonian coffee

The new European regulation 178/2002 imposes the determination of the geographical origin in the traceability process of foodstuffs at the moment of commercial transactions. In practice, it is difficult to determine with accuracy the geographical origin of foodstuffs. For this purpose, the total analysis of fungal communities in samples of coffee is used. In the present study the molecular technique using 28S rDNA profiles generated by PCR-DGGE was used in order to detect the variation in fungal community structures of coffee from five different locations in West and Coastal plain in Cameroon and the effect of treatment and coffee species on these fungal profiles. When the 28S rDNA profiles were analyzed by multivariate analysis, distinct microbial communities were detected. The band profiles obtained from different samples of coffee and specific for each location and could be used as a bar code to certify the origin of the coffee. This method is a new traceability tool which provides coffee products with a unique biological bar code and makes it possible to trace back the coffee to their original location. (Résumé d'auteur

Influence des conditions de la traite sur les qualités physico-chimiques et microbiologiques du lait cru collecté à Maroua, Cameroun

Cette étude a été réalisée dans le but d'apprécier les qualités physico-chimiques et microbiologiques et, d'évaluer l'effet de l'amélioration des conditions hygiéniques du lait cru de vache trait à Maroua. Deux types d'échantillons ont été prélevés pour les analyses : le lait trait dans les conditions ordinaires (CO) de traite, pratiquées dans les fermes ; et le lait trait dans les conditions améliorées (CA), après application de quelques règles d'hygiène. Les analyses physico-chimiques révèlent que la température du lait est comprise entre 33,25 et 37,65°C ; le pH, entre 6,75 et 7,67; l'acidité Dornic et la densité sont comprises respectivement entre 18,70 et 26,72 °D et entre 1,023 et 1,03°D. Les analyses microbiologiques révèlent que dans l'ensemble, la flore détectable des échantillons décroit des conditions ordinaires (CO) vers les conditions améliorées (CA). La flore totale passe ainsi de 4,6 - 7,67 Log10UFC/mL dans les CO à 2,3 - 5,95 Log10UFC/mL dans les CA ; la flore fongique passe de 1,24 - 5,54 dans les CO à 0,70 - 3,22 Log10UFC/mL dans les CA. Les coliformes fécaux passent de 2,18-3,95 Log10UFC/mL dans les CO à 1,30 - 3,23 Log10UFC/mL (CA) ; les streptocoques fécaux passent de 0,67 - 1,76 Log10UFC/mL (CO) à 0,46-0,9 Log 10UFC/mL (CA) ; les staphylocoques passent de 2,04 - 4,11 Log10UFC/mL (CO) à 1,84 - 2,78 Log 10UFC/mL (CA) Dans l'ensemble seuls deux échantillons sont contaminés par les salmonelles. L'amélioration des conditions hygiéniques de la traite, a permis de réduire la charge microbienne des échantillons de lait cru analysés. Ces réductions moyennes sont de l'ordre de 26,41 à 99,98 pour la FAMT ; 92,42 pour les coliformes fécaux ; 96,66 % pour les coliformes totaux ; 99,33 % pour la flore fongique ; 94,70 % pour les Streptocoques fécaux et 100 % pour les staphylocoques et salmonelles. Il ressort de ces travaux que tous les échantillons prélevés dans les CO sont de mauvaise qualité. Après application de quelques règles d'hygiène, 50 % des échantillons analysés respectent la norme