Salmonella in gut and droppings of three pest lizards in Nigeria

The carriage rate of Salmonella in the gut of three lizard species, namely the Agama lizard (Agama agama) (64), the wall gecko (Geckonidae) (60), the snake lizard (Ameiva ameiva) (52), and 60 samples of lizard dropping; and their survival under various environmental conditions was investigated. A gastrointestinal Salmonella carriage rate of 32, 39 and 48% were observed for the wall gecko, the Agama and snake lizards respectively. An isolation rate of 35% was also recorded for pooled lizard droppings. Salmonella survived in the droppings for 4 weeks in tap water and wet sand, 6 weeks in direct contact with air and up to 8 weeks when mixed with dry sand. An inoculum of 10⁶ c.f.u./g of a pure Salmonella isolate obtained from the lizard droppings proliferated extensively in sterile wet and dry soil samples, but decreased rapidly in the other environments. Salmonella was still detectable after 3 weeks in non-sterile wet and dry soil samples, up to 2 weeks in tap water, and approximately 8 days in powdered milk and gari. The potential public health significance of the observations is discussed.     

Occurrence of Salmonella spp and Cryptosporidium spp in a French coastal watershed: relationship with fecal indicators

Cryptosporidium and Salmonella are pathogenic microorganisms that can cause severe gastrointestinal illness in humans. Because these organisms are potentially transmitted through natural waters, this study was carried out to estimate the concentrations of both pathogens in a French coastal watershed and to determine the relationships with fecal indicators. Water samples from nine wastewater treatment plants and eight rivers were analyzed. Although both pathogens and indicators are released from sewage effluents, no clear correlation was found between the two enteric pathogens nor between a given pathogen and fecal indicators. These results suggest that fecal indicators do not adequately indicate the presence of Cryptosporidium and Salmonella in natural waters and that pathogens and indicators may have different behaviors in the aquatic environment.     

Prevalence of Salmonella serotypes in environmental waters and their relationships with indicator organisms

The incidence of serotypes of Salmonella in three types of environmental water (sea, river and fresh reservoirs) from north-east Spain was investigated. The study was performed at specific sampling locations during the summer for a period of five years (1992–1996). A total of 823 strains were isolated and 55 different serotypes were identified, 42 were recovered from sea water, 32 from river water and 12 from freshwater reservoirs. The most frequently isolated serotypes coincided with those involved in clinical cases in the area studied. Salmonella enteritidis was the most common (111 isolates), it was found in all types of water, although most predominantly in sea water (16.1% of the isolates). This serotype, together with S. hadar, significantly increased in frequency during the five year study period. The most frequent serotypes in river water and freshwater reservoirs were S. virchow (9.5%) and S. mikawasima (23.8%) respectively. Significant differences were assessed in the indicator organism densities between the samples with serotypes of clinical significance (S. enteritidis, S. infantis, S. typhimurium, S. virchow and S. paratyphi B) and those without clinical significance. Therefore their presence in all environmental waters may be of epidemiological significance.     

Restriction fragment length polymorphism (RFLP) of Salmonella organisms

Genetic relatedness of 20 Salmonella isolates comprising 16 serotypes was analysed by restriction endonuclease digestion of the total DNA with six endonucleases individually. The rDNA fingerprints generated by EcoRI were more polymorphic, each serotype showed a unique fingerprint sharing several core (monomorphic) bands with several polymorphic bands. Eight characteristic NciI rDNA fingerprints were found. Similar rDNA RFLP patterns were observed in strains of Salmonella from different serotypes.S.I. Koh-Luar and E. Lau are with the Department of Chemical Process & Biotechnology, Singapore Polytechnic, 500 Doyer Road, Singapore 139651. Republic of Singapore; S. T. Chew is with the Veterinary Public Health Laboratory (VPHL), Primary Production Department (PPD), 51 Jalan Buroh, Singapore 619415. Republic of Singapore. S.B. Chua is with the Veterinary Public Health Division, Primary Production Department, 5 Maxwell Road, No. 03-00, Tower Block, MND Complex, Singapore 069110. Republic of Singapore.     

Analysis of Salmonella Agona and Salmonella Weltevreden in Malaysia by PCR fingerprinting and antibiotic resistance profiling

Forty-eight strains of Salmonella enterica subsp. enterica serovar Agona and 33 strains of Salmonella enterica subsp. enterica serovar Weltevreden were characterized by random amplified polymorphic DNA (RAPD) fingerprinting using 3 different arbitrary primer, Enterobacterial Repetitive Intergenic Consensus-Polymerase Chain Reaction (ERIC-PCR) and antimicrobial susceptibility testing. By using RAPD, 81 strains (44 strains of S. Agona and 33 strains of S. Weltevreden) can be clustered into 14 groups and 6 single isolates whereas ERIC-PCR produced 7 clusters and 3 single isolates. Thirteen antimicrobial agents were used and all the isolates were resistant to erythromycin and showed Multiple Antimicrobial Resistance indexes, ranging from 0.08 to 0.62. Poultry still remain as the common reservoir for multi-drug-resistant Salmonella. On the other hand, vegetables contaminated with S. Weltevreden showed a gain in antimicrobial resistance. Besides that, consistent antibiograms were observed from S. Weltevreden isolated at Kajang wet market on 2000/08/02.     

Survival of a Salmonella typhimurium poultry isolate in the presence of propionic acid under aerobic and anaerobic conditions

Propionic acid is commonly found as a fermentation product in the gastrointestinal tracts of food animals and has also been used to limit the microbial contaminants in animal feeds. Because propionic acid is known to have antibacterial activity, the propionic acid encountered by foodborne pathogens during their life cycles may play an important role in inhibiting the survival of the pathogens. The survival patterns of Salmonella typhimurium poultry isolate were determined both in aerobic and anaerobic tryptic soy broth (TSB; pH 5.0 or 7.0) containing various concentrations of propionic acid (0-200 mM). The levels of recovered cells were consistently greater at pH 7.0 compared to those at pH 5.0. For the first 4 days, the levels were significantly decreased by incubation under anaerobic conditions as compared to aerobic condition at pH 7.0 (P<0.05). However, there were fluctuations of cell populations with different patterns depending on both concentrations and growth conditions. To characterize the nature of the capability which allowed the cell multiplication following decreases in cell population during incubation at pH 7.0, the cells isolated from the outgrowth cultures were tested for survival in aerobic or anaerobic TSB (pH 5.0 or pH 7.0) containing propionic acid (50 mM). The outgrowth isolates did not show significant differences in the level of recovered cells in the presence of propionic acid when compared to the wild type strain (P>0.05), suggesting that the cells in the outgrowth cultures did not harbour mutation(s) conferring increased resistance to propionic acid. In addition, the level of recovered cells of isogenic rpoS mutant strain of S. typhimurium was not significantly different from that of the wild type strain in the same assay conditions (P<0.05). The results of this study show that the bactericidal activity of propionic acid on S. typhimurium can be affected by environmental conditions such as acidic pH levels and anaerobiosis in food materials and gastrointestinal tracts. However, S. typhimurium is also able to multiply in the presence of sublethal concentrations of propionic acid at neutral pH during prolonged incubation under both aerobic and anaerobic conditions.     

Occurrence and distribution of culturable enteroviruses in wastewater and surface waters of north‐eastern Spain

Aims: Update information regarding occurrence and levels of culturable enteroviruses in several types of surface polluted waters in north‐eastern Spain and determine the proportion of the different species and serotypes. Methods and Results: The best procedures on hand in our laboratory for concentrating and quantifying culturable enteroviruses from different water sample types were used. Sequencing was used for typing the virus isolates. Geometric means of enteroviruses densities expressed in plaque forming units per litre were 968 in raw sewage, 12·51 in secondary effluents, 0·017 in tertiary effluents, 0·4 in river water and 0·36 in seawater. Enterovirus densities in wastewater revealed certain seasonality with a maximum at the end of spring – beginning of the summer. Coxsackievirus B, and amid them serotype CB4, were the most abundant species and serotypes detected. Conclusions: Densities of enteroviruses in different north‐eastern Spain surface waters are similar to those present in industrialized countries with temperate climate. No wild polioviruses were detected. Distribution of species showed a clear prevalence of coxsackieviruses. Significance and Impact of the Study: Information regarding enteroviruses in this geographical area provides valuable information to estimate the risk of enteroviruses transmission through water and for complementing clinical epidemiological data.     

Occurrence and densities of bacteriophages proposed as indicators and bacterial indicators in river waters from Europe and South America

AIMS: To evaluate the feasibility of bacteriophages as a complementary tool for water quality assessment in surface waters from different parts of the globe. METHODS AND RESULTS: Faecal coliform bacteria, enterococci, spores of sulphite-reducing clostridia, somatic coliphages, F-specific RNA bacteriophages and bacteriophages infecting Bacteroides fragilis were determined by standardized methods in raw sewage and in 392 samples of river water from 22 sampling sites in 10 rivers in Argentina, Colombia, France and Spain, which represent very different climatic and socio-economic conditions. The results showed that the indicators studied maintained the same relative densities in the raw sewage from the different areas. Classifying the river water samples according to the content of faecal coliform bacteria, it can be observed that the relative densities of the different bacterial indicators and bacteriophages changed according to the concentration of faecal coliform bacteria. There was a relative increase in the densities of all groups of bacteriophages and sulphite-reducing clostridia with respect to faecal coliforms and enterococci in the samples with low counts of faecal coliform bacteria. CONCLUSIONS: The numbers of bacterial indicators and bacteriophages were similar in the different geographical areas studied. Once released in rivers, the persistence of the different micro-organisms differed significantly. Bacteriophages and spores of sulphite-reducing clostridia persisted longer than faecal coliforms and enterococci. SIGNIFICANCE AND IMPACT OF THE STUDY: Bacteriophages in river water samples provide additional information to that provided by bacteria about the fate of faecal micro-organisms in river water. The easy, fast and cheap methods for phage determination are feasible both in industrialized and developing countries.     

Materials forPythium flora of Japan. X. Occurrence,identification and seasonality ofPythium spp. in three pond waters and mud soils in Osaka

Seasonal fluctuations ofPythium species in three pond waters and mud soils in Sakai, Osaka, were studied for periods of two years and 14 months, respectively. Thirteen species and four groups were isolated from the pond waters while nine species and three groups were obtained from the mud soils. The highest frequency and total number of species were recorded in the cold and moderately warm seasons and the lowest in summer. Most of the species isolated from the pond waters have been previously recorded from aquatic habitats.     

Interference of raw milk autochthonous microbiota on the performance of conventional methodologies for Listeria monocytogenes and Salmonella spp. detection

Pathogen detection in foods by reliable methodologies is very important to guarantee microbiological safety. However, peculiar characteristics of certain foods, such as autochthonous microbiota, can directly influence pathogen development and detection. With the objective of verifying the performance of the official analytical methodologies for the isolation of Listeria monocytogenes and Salmonella in milk, different concentrations of these pathogens were inoculated in raw milk treatments with different levels of mesophilic aerobes, and then submitted to the traditional isolation procedures for the inoculated pathogens. Listeria monocytogenes was inoculated at the range of 0.2–5.2 log CFU/mL in treatments with 1.8–8.2 log CFU/mL. Salmonella Enteritidis was inoculated at 0.9–3.9 log CFU/mL in treatments with 3.0–8.2 log CFU/mL. The results indicated that recovery was not possible or was more difficult in the treatments with high counts of mesophilic aerobes and low levels of the pathogens, indicating interference of raw milk autochthonous microbiota. This interference was more evident for L. monocytogenes, once the pathogen recovery was not possible in treatments with mesophilic aerobes up to 4.0 log CFU/mL and inoculum under 2.0 log CFU/mL. For S. Enteritidis the interference appeared to be more non-specific.     

Contribution of picoplankton to primary production in estuarine,coastal and equatorial waters of Brazil

Quantitative data on primary production of picoplankton are presented for three different Brazilian marine ecosystems: estuarine, coastal and oceanic. The size fraction from 0.45 μm to 1.0 μm was responsible for 3.0% to 28.5% of ¹⁴C uptake in estuarine waters; 18.5% to 40.4% in coastal waters, and 6.7% to 100.0% in oceanic waters, respectively. These results establish the importance of picoplankton as primary producers in different marine environments along the Brazilian waters.     

Toxic cyanobacteria (blue-green algae) in Finnish fresh and coastal waters

A survey of the occurrence of toxic blooms of cyanobacteria in Finnish fresh and coastal waters was made during 1985 and 1986. Toxicity of the freeze-dried water bloom samples was tested by mouse-bioassay (i.p.). Forty-four per cent (83/188) of the bloom samples were found to be lethally toxic. Hepatotoxic blooms (54) were almost twice as common as neurotoxic ones (29). Anabaena was the most frequently found genus in toxic and non-toxic blooms and it was present in all neurotoxic samples. Statistical associations were found between hepatotoxicity and incidence of Microcystis aeruginosa, M. viridis, M. wesenbergii, Anabaena flos-aquae and Anabaena spiroides. Neurotoxicity was statistically associated with Anabaena lemmermannii, Anabaena flos-aquae and Gomphosphaeria naegeliana. Isolation of strains of cyanobacteria confirmed the occurrence of hepatotoxic and neurotoxic strains of Anabaena, as well as hepatotoxic strains of Microcystis and Oscillatoria species.Toxic blooms caused cattle poisonings at three different lakes during the study period. Toxic blooms also occurred in drinking water sources. Our study shows that toxic cyanobacteria are more common in Finnish lakes than would be expected on the basis of animal poisonings. The results of this study show the existence of toxic cyanobacteria in Finnish water supplies and the need for their continued study as agents of water based disease.     

Occurrence ofDinophysis spp. and toxic shellfish in the Northern Adriatic

The dynamics of the toxicity of the musselMytilus galloprovincialis was compared between two different shellfish farms, 5 km apart, but using the same cultivation technique. The main differences concerned the freshwater influx and the open aspect to the Gulf of Trieste. It is suggested that a deep closed bay and abundant fresh water inflow are the two main conditions for the low toxicity levels in mussels and for shorter periods of danger. A detailed study of the phytoplankton samples revealed the presence of eight species ofDinophysis in the area of both shellfish farms. During the period of the DSP outbreak in Slovenia (autumn and winter 1989).D. fortii andD. acuminata were the most frequentDinophysis species. There was a high positive correlation between the onset of mussel toxicity and the appearance ofDinophysis spp.     

Occurrence of nitrogen fixation among Vibrio spp.

Virtually all Vibrio spp. known and available in culture collections and several newly isolated Vibrio sp. were tested for their ability to fix molecular nitrogen, using the acetylene reduction technique, the fixation of the heavy isotope ¹⁵N, and by growth on media devoid of combined nitrogen. Among the 27 species tested, four, including V. diazotrophicus, proved to be nitrogenase-positive. The potential of nitrogen fixation was now also discovered in V. natriegens, V. pelagius and V. cincinnatiensis. Among the 9 newly isolated strains, 4 were nitrogenase-positive. These strains were classified as V. diazotrophicus on the basis of DNA homology studies. Nitrogenase was only induced during growth under anaerobic conditions. Dissolved oxygen as low as 1 M inhibited nitrogenase completely. This inhibition at low oxygen concentration, however, was reversible. 50–100 M dissolved oxygen inhibited nitrogenase irreversibly.This work was carried out at Geomicrobiology Division, the University of Oldenburg, FRG     

Characterization of Salmonella spp. isolated from patients below 3 years old with acute diarrhoea

Fifteen strains of Salmonella were isolated from children with clinically diagnosed diarrhoea aged below 3 years old, who had been admitted to K7 ward, Pediatric Institute, Kuala Lumpur Hospital. The isolates were tested for their susceptibility to a range of antimicrobial agents, and typed by serological tests and randomly amplified polymorphic DNA (RAPD) fingerprinting. All the strains had a similar pattern of antimicrobial susceptibility, where they were susceptible to a wide range of antimicrobial agents. The serological test has typed them into three serovars, which were identified as Salmonella enterica ser. Akanji, Salmonella enterica ser. Hindmarch and Salmonella enterica ser. Richmond. In contrast, the RAPD fingerprinting classed them into two major clusters, cluster 1 consisting of 12 strains of Salmonella and cluster 2 consisting of three strains of Salmonella.     

A harpacticoid copepod Microsetella spp. from sub-Arctic coastal waters and its sensitivity towards the polyaromatic hydrocarbon pyrene

Species of the harpacticoid copepod genus Microsetella are commonly reported to occur in Arctic and sub-Arctic coastal waters, but nothing has yet been reported on their sensitivity towards toxic substances. Effects of the polyaromatic hydrocarbon pyrene on Microsetella spp. from Western Greenland were investigated by looking at survival of females, feeding status, and nucleic acid content after a 96-h exposure. Less than 10% survived at 100 nM exposure concentration, and a 50% reduced survival was also evident at 0.1 and 10 nM. The RNA:DNA ratio was significantly higher, 2.1 ng/individual, at the lowest concentration of 0.01 nM compared to 0.9 ng/individual in the control, which indicates increased metabolic activities. A reduced DNA content in higher exposure concentrations of 1–100 nM suggests inhibition of egg development. Gut content was significantly declining with increasing exposure concentrations with only 2% of exposed females displaying full guts at 100 nM pyrene. Together with reduced feeding activity, effects at the population level can be anticipated, but would have to be confirmed in future experiments. The data suggests a higher sensitivity of Microsetella spp. compared to other Arctic copepods, which implies more severe effects from oil on the pelagic food web in the areas and periods where Microsetella spp. dominates Arctic plankton food webs.     

Occurrence ofAzospirillum spp. in coconut-based farming systems

Occurrence of Azospirillum was investigated in coconut-based farming systems, such as high-density multispecies cropping (15 crops), multi-storeyed cropping (3 crops), mixed cropping with tea and coffee (2 crops), intercropping with tropical tubers (5 crops), mixed farming with grasses (3 crops) and in 3 crops, arecanut,Mimosa invisa and sugarcane from other plots. A total of 26 plantation crops and intercrops were included in the study. Incidence of Azospirillum was determined by 2,3,5-triphenyl-tetrazolium chloride reduction and by culturing root fragments in N-free semisolid malate medium. Root samples from guava, mango and mimosa did not show any tetrazolium reduction or sub-surface pellicular growth. The extent of occurrence of Azospirillum seemed to depend upon the crop combinations. In a mixed farming system where guinea grass was one of the component crops, more root fragments of coconut and pepper demonstrated tetrazolium reduction activity than when guinea grass was absent.Azospirillum lipoferum andA. brasilense constituted 42% and 45% of the isolates, respectively, in the coconut-based cropping systems. Isolates from guinea grass, sugarcane and jackfruit exhibited higher nitrogenase (C₂H₂ reduction) than those isolated from plantation crops, tuber crops and spices. The large variation in the extent of association and nitrogenase activity of isolates from different crops indicated the need for inoculation with efficient cultures in a number of crops in coconut-based cropping systems.Contribution No. 613 of Central Plantation Crops Research Institute, Kasaragod.     

Development of duplex PCR for the detection of Salmonella and Vibrio in drinking water

We report here a rapid protocol for the detection of Vibrio and Salmonella in drinking water using a duplex PCR reaction. The developed protocol can detect as few as 500 cells in a single reaction, which has been achieved by optimizing the temperature steps and magnesium chloride concentration for the reactions. The described PCR protocol could detect Vibrio and Salmonella spiked in drinking water.     

Rotifer distributions in the coastal waters of the northeast Pacific Ocean

Absolute abundance of rotifers was assessed from 5 to 80 km across the continental shelf off of the southern Oregon coast (U.S.A.) in the northeast Pacific Ocean. A total of 97 vertically stratified water samples were collected at 49 stations from two depths, 3 and 30 m. Coastal upwelling conditions were indicated, with decreased temperature, increased salinity and higher chlorophyll-a concentrations closer to shore. Two rotifer genera, Synchaeta and Trichocercaoccurred within 16 km of shore with densities increasing closer to shore. Synchaeta reached densities of 64 inds l^–1 while Trichocerca was sparse (<1 inds. l^–1). Rotifers were most abundant at 3 m and the densest aggregations appear to be associated with estuary outlets, suggesting that estuaries may be important in exporting rotifers to nearshore coastal waters.     

Isolation of stable aroA mutants of Salmonella typhi Ty2: properties and preliminary characterisation in mice

Summary Derivatives of the Salmonella typhi strain Ty2 carrying stable mutations in the aroA gene were isolated. The mutations were generated by transducing an aroA::Tn10 marker into Ty2 and selecting for derivatives which were tetracyline sensitive and dependent on aromatic compounds for growth. Isolates that did not revert to aromatic compound independence at a detectable frequency were obtained. An S. typhimurium derived aroA specific DNA probe was used to demonstrate the presence of DNA rearrangements in the aroA region of the chromosome of some of the S. typhi aroA mutants. Most of these isolates still expressed Vi antigen. Aromatic compound dependent mutants of S. typhi were less virulent in mice than S. typhi Ty2 following intraperitoneal challenge with bacteria suspended in mucin. Mice immunised with one of these mutants, named WBL85-1, were protected against a potentially lethal challenge of S. typhi Ty2.