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H2S bacteria of seafish flesh are weakly halophilic and require on average 1.68% NaCl according to statistical studies. Enumeration is optimal on PCA-H2S(a PCA medium supplemented with sulfur sources and increased NaCl concentrations) incubated at 25C. Total aerobic bacteria can be counted simultaneously on this medium. The proportion of H2S bacteria relative to total aerobic bacteria increased slightly during prolonged storage of the fish, but was highly variable. Models relating H2S bacterial counts to spoilage of fish are sigmoidal and showed that when the count exceeds 10,000 CFU/g, whole or filleted fish stored in ice at 0C are unfit for consumption. Shewanella putrefaciens accounted for 69% of the H2S bacteria at the fifth day of storage and 100% at the fifteenth.

H2S+ bacteria responsible for the degradation of sulfur-containing amino acids of fish muscle are currently little used to evaluate the microbiological pal quality of fish. Shewanella putrefaciens greatly predominates in this flora, and was therefore used to define a suitable culture method and medium. Inoculations by the Spiral surface method at 25C, with an incubation of 72h, gave the best counts on a medium containing two sources of sulfur (organic and inorganic) for H2S+ bacteria. The culture medium and the NaCl concentration were determinant in the evaluation of this flora. At present there is no standard medium which meets these requirements.

The total aerobic flora of seafish flesh is weakly halophilic, and requires on average 1.38% NaCl according to statistical studies. Enumeration is optimal on tryptone soya agar or on NaCl supplemented plate count agar (-H2S), incubated at 20 and 25C, respectively. Plate count agar (-H2S) was selected because it can also be used for enumeration of hydrogen sulfide-producing bacteria by degradation of sulfur-containing proteins, which are abundant in fish The models employed are sigmoidal. The initial bioburden is too great for there to be a lag phase during storage in ice at 0C. The models show that when the total aerobic microflora count exceeds 100,000 cfu/g, whole or filleted fish stored on ice at 0C are unfit for consumption.

Seventy-eight strains were isolated from fillets of vacuum-packed smoked and salted herring (Clupea harengus) on APT glucose medium at 5°C or 20°C . All the isolates belonged to the genus Lactobacillus. CO2 production and arginine degradation were characteristic of the isolates. A dichotomous key is proposed, using only four characters (growth on Rogosa broth, fermentation of ribose, presence of meso-diaminopimelic acid, isomer of lactate produced) for presumptive identification of lactobacilli from fish. The isolates could be allocated to three groups related to Lactobacillus groups II or III of Kandler and Weiss. Most of the strains possess important technological capacities : tolerance of high levels of NaCl, liquid smoke and bile salts. No lipolytic activity was found but some proteolytic activity was found on casein. Inhibitory activity against pathogenic or spoilage organisms was frequent and probably due to the production of hydrogen peroxide, or organic acids or both. No Carnobacterium strains were isolated despite the use of suitable temperature and isolation medium, probably because of the smoking of the fish.

Spoilage yeasts, identified asCandida pelliculosaandKloeckera apis, were isolated from fermented pasteurized pineapple juice, guava and passion fruit nectars, and studied for their heat resistance in relation to the pasteurization process of the beverages. The decimal reduction times (DT) obtained between 55 and 60°C forK. apisvaried from 1.41 to 2.49 min, and those forC. pelliculosaobtained between 60 and 75°C varied from 1.03 to 4.90 min depending upon the beverage and the tested temperatures.C. pelliculosaseemed to be more heat resistant thanK. apis. Thez-values or the increase in temperature needed to reduce theDTby 10, determined between 60 and 75°C forC. pelliculosa, were 31.75±0.03°C (r2=0.91) in pineapple juice, 27.70±0.04°C (r2=0.90) in passion fruit nectar and 34.84±0.02°C (r2=0.998) in guava nectar. ForK. apis, thez-values determined between 55 and 60°C were 21.88±0.07°C (r2=0.97) in pineapple juice, 22.73±0.04°C (r2=0.99) in guava nectar and 29.07±0.01°C (r2=0.999) in passion fruit nectar. The minimal pasteurizing valuesPTzwere determined forC. pelliculosaat 70°C and at 75°C, at a pasteurization efficiency (logN0/N) of 9. In pineapple juice,Pz70=27.91 min andPz75=13.5 min would have be applied to destroy almost any vegetative forms of the yeast. In passion fruit nectar,Pz70=20.25 min andPz75=9.27 min, and in guava nectarPz70=16.83 min would have be applied.

The market for vacuum-packed pasteurized seafood products is developing rapidly. The stability and safety of pasteurized products rely on pasteurization processes and subsequent storage at refrigeration temperatures. The aim of this work was to study the heat resistance of characteristic bacterial flora responsible for spoilage in pasteurized seafood products and to determine the minimal pasteurizing value required for the destruction of nonsporeforming bacteria. The D T and z-values were determined for various bacteria selected from among the most heat-resistant bacteria isolated from seafood products (Pseudomonas paucimobilis, Pseudomonas putida, Micrococcus varians, Enterococcus faecium and Staphylococcus aureus). Thermal resistance was measured in different media (fish fillet, fish terrine and M/15 phosphate buffer). The most heat-resistant microorganism found was Pseudomonas paucimobilis: the D 70 varied between 1.16 and 3.36 min, and the z-value, between 5.8 and 9.1 o C, depending upon the medium. The minimal pasteurizing values required to destroy a sufficient proportion of nonsporulated bacteria were determined. In France, the pasteurizing value is designated P T z . The reference temperature was 70 o C (the official reference temperature in France). In fish, the minimal pasteurizing value, P 70 6 =15 min, should be applied to ensure the destruction of almost any vegetative forms of bacteria. In a fish terrine, the minimal pasteurizing value should be P 70 9 =30 min

The behaviour of Rhizobium meliloti and Bradyrhizobium japonicum (three strains of each) during storage in atmospheres of controlled relative humidities (r.h.) offrom 3 to 83.5% at 30°C in the presence of air were investigated. Whatever the r.h. values imposed, the desiccation step did not significantly affect the survival rates except for B. japonicum G49. However, differences in behaviours and tolerances against protracted storage at the five r.h. values tested were noted between rhizobia and bradyrhizobia. Rhizobium meliloti strains were found more susceptible to storage at 3 or 83.5% r.h. than B. japonicum strains. Whatever the r.h. values, cell populations of B. japonicum declined at a rather constant rate and no surviving cells were observed after 100 days of storage. On the contrary, two step decreases were noted for R. meliloti stored at ⩽ 67.8% r.h. and appreciable survival rates were still obtained after 100 days of storage at 22, 43.6 or 67.8% r.h. Based on scanning electron microscope examinations, it was found that drying by itself did not morphologically affect brady(rhizobia) cells. The combined processes of drying and rehydration led to minor increases in cell volumes (for cells stored at 83.5% r.h.) and appearance of numerous granules and strands of exopolymers (for cells stored at 3% r.h.). After storage in their dried states, loss of infectiveness was observed for B. japonicum cells whereas R. meliloti cells maintained the same degree of symbiotic infectivity.

Adhesion of 11 Rhizobiaceae strains on soybean roots was investigated. Whether these strains were able or not to nodulate soybean, they were found to adhere to these roots. Bacterial concentration above 1 × 1010 cells∙mL−1 was necessary to saturate root surfaces. Homologues and heterologous strains were used in mixed inoculation with Bradyrhizobium japonicum G49 StrR, used as reference strain in low number. Competition for adhesion was obtained at saturating concentrations of competitive strains. Only partial inhibition (R strain adhesion in the presence of heterologous strains was obtained, suggesting the occurrence of two modes of G49 StrR strain adhesion on the host roots: (i) a nonspecific adhesion of the B. japonicum and (ii) a specific adhesion of the B. japonicum or of strain G49 StrR. With homologous strains, inhibition of G49 StrR strain adhesion indicated a different competitive behavior between the four strains used belonging to the two DNA homology groups. Thus, the existence of species-specific recognition for all strains of B. japonicum, on soybean roots, remains to be confirmed.Key words: Rhizobiaceae, soybean, competition, adhesion, root.

Production of Bradyrhizobium japonicum cell concentrates by spray-drying in skim milk plus sucrose medium and the feasability of storing dried inocula over long periods were investigated. Storage of spray-dried cells under mild vacuum was equivalent to storage under nitrogen. Oxygen and ambient temperature were found detrimental for survival of dried cells. High initial cell concentration and storage under low relative humidities ( 10 9 cfu g -1 during at least a 25 week storage period) without altering the symbiotic properties of B. japonicum

The extracellular inulinase system of a strain of Arthrobacter sp. consists of a β-fructofuranosidase active on inulin raffinose and sucrose with a relative rate inulin/sucrose (I/S) of 0.2. Crude enzyme preparations were obtained by fractionation of the liquid culture at stationary phase of growth with ammonium sulphate. Purification was carried out by DEAE cellulose chromatography and ultrogel ACA 34. Only one protein band was observed by electrophoresis. The enzyme was stable at high temperatures and was active at neutral or slightly alkali pH. Fructose is liberated as the sole reaction product of inulin hydrolysis, suggesting that the enzyme was an exoinulinase. The Michaelis constant (calculated at 40°C and pH 6) was 0.25 × 10-2 mol/l for the inulin and 0.12 × 10-2 mol/l for sucrose. The enzyme was suitable for fructose production from root extracts of plants rich in polyfructosans or sucrose.

The drinking water supply in Yaounde, Cameroon, often fails to meet demand and this leads many people to seek water from springs and wells the microbiological quality of which is unknown. We carried out a microbiological survey of five spring water points and ten wells. The fifteen study sites were located in various residential districts and were selected according to geographical location and number of users. Microorganisms were isolated on specific culture media using the membrane filter technique. We found that these water supplies contained many types of bacteria including Pseudomonas aeruginosa, Aeromonas hydrophila and indicators of fecal contamination. Maximum annual concentrations differed at the various sites and over time, from 750 to 98,000 CFU/l for P. aeruginosa, 40 to 78,000 CFU/l for A. hydrophila and 300 to 58,000 CFU/l for fecal indicator bacteria. The density of fecal bacteria was strongly correlated (p0.01) with those of P. aeruginosa in spring water and A. hydrophila in well water. The degree of correlation between microbial concentrations differed between sites. The source of fecal contamination differed between sites and was animal, human or both. The densities of bacteria recorded were high. Therefore, consumers of water drawn from these sources are at short-term risk of contracting waterborne diseases.

The growth, survival, and death of Listeria monocytogenes were studied in a synthetic medium as a function of temperature, NaCl content, and amount of liquid smoke, and the findings were validated in smoked fish products. The smoke preservative compound was simulated by adding liquid smoke, and the concentration was expressed as phenol concentration. The growth of L. monocytogenes was limited at a temperature as low as 4 degrees C or at a phenol concentration as high as 20 ppm. The predicted values were obtained using a mathematical model established in liquid medium in a previous study. They accurately fit values observed in L. monocytogenes challenge tests on smoked fish. After 21 days of storage the deviation between the predicted and experimental values was within 0.5 log for 60% of the data. This model may be useful in predicting Listeria contamination in smoked fish. Moreover, this study emphasizes the importance of phenol concentration to control the growth of Listeria spp. in smoked food products.

The combined effects of temperature (2-46 degrees C) and pH (1.55-6.25) on the growth of Candida pelliculosa isolated from guava nectar produced in Cameroon were studied using a turbidity method, ie measurement of optical density at 630 nm. A quadratic polynomial model was constructed to predict the effects and interactions of these two environmental conditions on the maximal optical density obtained (i2 = 0.97). The relation between optical density and population density of C. pelliculosa (CFU ml-1) was also established using an exponential regression (2 = 0.99). According to the model, maximal growth conditions were 37 degrees C and pH 6.25 for obtaining the maximal optical density of 1.25 corresponding to about 60 x 10(6) CFU ml-1. A good agreement of the model was found between the predicted values and the observed values of maximal optical density. The model was validated by the experimental values of maximal optical density obtained in the growth of C. pelliculosa in commercial guava nectar (pH 3.15).

Three hundred samples of ice cream produced in two main towns in Cameroon (Douala and Yaoundé) are evaluated for their hygienic quality. The microbiologic examinations show that many of them are contaminated with bacteria of faecal origin, pathogenic Staphylococcus and Salmonella respectively in 71.3, 49.6 and 5% of the products examinations in the study. The use of non potable water and the disrespect of the hygienic rules during the production are the main causes of contamination. Recommendations are made to preserve the public health in the developing country.

14 activites enzymatiques (3 deshydrogenases et 11 hydrolases) ont ete recherchees systematiquement sur les electrophoregrammes en gel d'agar des extraits de 2 souches de Aspergillus fischeri et de 14 souches de A. fumigatus (8 isolees de lesions humaines ou animales intitulees souches ‘pathogenes’, et 6 souches d'origine saprophytique). La composition enzymatique de A. fumigatus est apparue tres polymorphe et sans rapport avec l'origine des souches.

The sanitary quality of perishable food products can be evaluated through an assessment of the bacterial microflora or by chemical tests such as the determination of total volatile basic nitrogen (TVBN). For deep frozen fish fillet, a method was developed based on the reduction of trimethylamine oxide (TMAO) to trimethylamine (TMA), as measured by a pH change in the cultured medium. The technique is rapid (8 h incubation at 25°C) and can be easily applied in laboratories. Comparison of the results obtained by this method with those based on TVBN and TMA determinations gave good correlations.

The dynamics of the development of delayed hyperssnsitivity (D.H.) in the CBA mouse and the Wistar rat experimentally infected with trichinosis was studied by means of macrophage inhibition in relation to the following, the level of infestation, variations in the numbers of peritoneal cells, host-parasite antigens, and the level of adaptation of the parasite. The study demonstrated that: 1. (1) D.H. appeared by the seventh day following introduction of the parasites; 2. (2) it was depressed by the 14th day; 3. (3) it decreased progressively and disappeared by the fourth month; 4. (4) it was influenced to a certain extent by the level of infestation, but only at the beginning of the experimental disease; 5. (5) it did not seem to be affected by host-parasite antigens; 6. (6) it seemed inversely proportional to the level of the parasitic adaptation. D.H. is probably related to the release of antigens by the first moults of the larvae and it might play an important role in the establishment of immunity against T spiralis.

Les variations relatives des constituants seriques au cours de l’evolution de la toxoplasmose chez la Souris C B A, ont ete etudiees par electrophorese en acetate de cellulose.La technique d’immunodiffusion radiale a ete utilisee pour caracteriser dans le temps les diverses classes d’immunoglobulines.Entre le 7e et le 21e jour d’evolution de la maladie, on assiste a une diminution significative de l’albumine et conjointement a une augmentation significative des β-globulines.Une augmentation continue des γ-globulines est contrebalancee par une diminution des α-globulines.Apres le 14e jour, les immunoglobulines IgG2a et IgM sont relativement augmentees ; les IgG2b restent constantes jusqu’au 84e jour alors que les IgG1 et les IgA, apres une augmentation sensible au 7e jour, diminuent au 14e jour pour reprendre leur valeur normale au 84e jour.Par ailleurs, la reinfection par une souche virulente au 14e jour de l’infection chronique produit en 3 jours une augmentation des IgG2a aussi forte que celle observee apres 42 jours d’evolution de la souche chronique seule.

Resume Les auteurs rapportent chez une femme de 69 ans, la decouverte d'un specimen adulte de Dicrocoelium dentriticum au cours d'une intervention chirurgicale sur les voies biliaires pour cholecystite lithiasique chronique. Apres la description du parasite, ils envisagent pour cette helminthiase humaine exceptionnelle, les differentes possibilites diagnostiques, cliniques, parasitologiques et immunologiques.

Resume Les variations des immunoglobulines et des globulines seriques ont ete etudiees dans le temps au cours de la trichinose experimentale de la souris CBA et du rat Wistar, par electrophorese sur acetate de cellulose et immunodiffusion radiale. Chez le rat et la souris, on assiste a une diminution significative des albumines et parallelement a une augmentation des γ globulines. Le phenomene est cependant beaucoup plus precoce et marque chez la souris que chez le rat, ces differences pouvant traduire une adaptation parasitaire meilleure de la trichine chez le rat. Toutes les classes d'immunoglobulines sont precocement augmentees chez la souris, apres 7 jours d'evolution de la maladie. Les IgG2a et les IgA sont les immunoglobulines les plus interessees par cette augmentation. Les diverses immunoglobulines qui apres 120 jours d'evolution de la parasitose persistent a des valeurs superieures a celle des temoins ont cependant tendance a diminuer apres 2 mois d'evolution, hormis les IgA qui augmentent sensiblement entre 60 et 120 jours.

Un mutant acido-tolerant deR. meliloti a ete isole. Le caractere de resistance en milieu acide n'a pas ete obtenu par adaptation sur des milieux de plus en plus acides mais par mutageneses successives provoquees par la N-methyl-N'nitroso-N-nitrosoguanidine (NTG) et selection sur milieu acide de facon a rendre stable le caractere acido-tolerant. Ce mutant acide presente la propriete de se developper plus lentement que la souche sauvage sur milieu pauvre. Ceci ne l'empeche pas de presenter sensiblement la meme efficience que cette derniere a pH voisin de la neutralite en milieu synthetique.

En vue d'une etude, au laboratoire, de la nodulation et de la symbiose plante-bacterie des preparations de protoplastes de mesophylle et de nodule racinaire ont ete effectuees chez le haricot (Phaseolus vulgaris variete Constant). Pour chaque preparation, les conditions operatoires et les concentrations optimales de cellulase et de pectinase en solution, dans du mannitol 0,6M ont ete definies.

A partir de la souche deR. meliloti Ve 26 mobile et chimiotactique, un mutant non mobile (mob−) et un mutant hyper-mobile (mob+) ont ete isoles. L'importance du role de la mobilite dans les phenomenes d'infection et de nodulation lors d'inoculations mixtes realisees en miniserre experimentale, est montree: le mutant Ve 26 mob+ forme 86% et 48% de nodules respectivement quand il est inocule en melange avec le mutant Ve 26 mob− ou avec la souche 2011 (non mobile par rapport au mutant Ve 26 mob+).

Des mutants non mobiles (mob−) et non chimiotactiques (chem−) deRhizobium meliloti Ve 26 ont ete isoles afin de connaitre l'importance de ces caracteres dans la nodulation de la luzerne en milieu liquide et en milieu solide. En milieu liquide les mutants produisent un nombre de nodules equivalent a ceux des souches parentales; par contre, en milieu solide (perlite, sol) l'etude realisee dans une ‘miniserre’ experimentale adaptee montre que les caracteres de mobilite et de chimiotactisme favorisent la nodulation et augmentent notablement le pouvoir competitif des souches qui les possedent.

Summary The resistance of 81 Rhizobium strains and 11 Agrobacterium strains to 16 antibiotics was investigated. Most strains were resistant even to high concentrations of lincomycin. All the strains of the species Rhizobium meliloti, Rhizobium phaseoli, Rhizobium japonicum and the genus Agrobacterium reacted relatively homogeneously to all the antibiotics, unlike Rhizobium trifolii, Rhizobium leguminosarum and Rhizobium spp. The majority of the fast-growing species of Rhizobium tested was found to be resistant to > 32 μg/ml penicillin and to Rhizobium were susceptible to penicillin concentrations 1 μg/ml. The majority of the Agrobacterium strains tested were resistant to streptomycin concentrations > 32 μg/ml, allowing them to be distinguished from strains of R. meliloti which were rarely resistant to such high concentrations.

Rat liver microsome UDP-glucuronyltransferase and labelled UDP-glucuronic acid were incubated either with P.R.T. or the compounds obtained by the in vitro metabolism of the toxin. Under the same conditions, labelled P.R.T. or its labelled metabolites were incubated with UDP glucuronyltransferase. Radioactive metabolites were produced with Eremofortin C and Eremofortin C alcohol and in each case, were identified as the corresponding beta-glucuronide conjugate. No measurable glucuronidation of P.R.T. or P.R.T. alcohol was observed. The results outlined in this paper show a good correlation between the biological effects and the ability of forming a glucuronide conjugate.

Un antigène très purifié, extrait de Fasciola hepatica, a été utilisé en intradermoréaction chez des zébus atteints de fasciolose. A la dose de 0,00015 mg et en considérant comme positives les réactions papuleuses de diamètre supérieur à 5 mm, il n'a permis de diagnostiquer l'infestation des bovins que dans 32,2 p. 100 des cas. Bien que ce résultat ait été acquis sans erreur par excès, il paraît encore insuffisant