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Biomedical subjects

A H Havelaar

Publications and source records attributed to A H Havelaar.

At least 19 recordsLinked to original sources
PubMed1992

[Health complaints in relation to quality of swimming water in participants of a triathlon].

Participants in a triathlon in Alphen aan den Rijn, the Netherlands, reported gastrointestinal symptoms to the local health authority. A study was performed to establish the number of complaints and the relation with the microbiological water quality at the surface water swimming site, which met current standards. An epidemiological survey was carried out with a questionnaire among 629 participants, with non-participating relatives as controls. Faecal samples of patients and water samples were investigated by conventional methods. 439 participants and 217 controls completed the questionnaire. 140 participants had at least one gastro-intestinal symptom and 28 (6.4%) had highly credible gastroenteritis. Participants had an odds ratio for gastro-enteritis of 14.7 (95% CI: 2.39-604.45). Electron microscopic examination in six of 12 patients showed viruses able to cause such symptoms. Water samples showed considerable faecal pollution at the time of the triathlon (geometric mean counts: thermotolerant coliforms 725/100 ml; faecal streptococci 23/100 ml). The most likely source is the effluent discharge of the nearby waste water treatment plant. A surface water swimming site meeting current standards does not exclude health complaints among tri-athletes.

Adolescent↗
PubMed1992

Typing of Aeromonas strains from patients with diarrhoea and from drinking water.

Aeromonas strains (187) from human diarrhoeal stools and from drinking water (263) in The Netherlands were typed by three different methods. Biotyping alone was found to be of little value for epidemiological studies because 84% of all strains belonged to only 10 biotypes. Common biotypes could be further differentiated by serotyping. Gas-liquid chromatography of cell wall fatty acid methyl esters (FAME) was useful for species identification as well as for typing: 86% of all strains could be identified to the species level, and within this group 92% of all identifications corresponded with the biotype. Cluster analysis and principal component analysis of FAME profiles could be used for comparison of strains from different sources and gave the same general conclusions as bio- and serotyping. There was little overall similarity between Aeromonas strains from human (diarrhoeal) faeces and from drinking water, differences being most pronounced for Aeromonas caviae and least for A. sobria.

Aeromonas↗
PubMed1992

Lack of colonization of 1 day old chicks by viable, non-culturable Campylobacter jejuni.

Seven strains of Campylobacter jejuni, isolated from various sources [human (n = 2), chicken (n = 3), water (n = 2)], were studied under starvation conditions in filter-sterilized and pasteurized surface water by acridine orange direct count (AODC), viable count (DVC) and culture methods. Plate counts showed a rapid decline (2 log-units/day) for all strains under these conditions. Only one of the seven strains (14%) showed a (prolonged) viable, non-culturable 'state'. The ability of these viable, non-culturable cells to colonize the intestine was tested on day-old chicks. The infectious oral dose of freshly cultured cells of this model was 26-260 cfu; 1.8 x 10(5) viable, non-culturable C. jejuni were introduced to day-old chicks orally. Campylobacter jejuni was not isolated from the caeca of the chicks after incubation for 7 d. Also, passage through the allantoic fluid of embryonated eggs did not recover viable, non-culturable C. jejuni. These findings cast serious doubts on the significance of the viable, non-culturable 'state' in environmental transmission of C. jejuni.

Animals↗
PubMed1990

[Aeromonas species as cause of diarrhea and infections outside the gastrointestinal tract in The Netherlands].

In a national survey in the period May 1986-December 1987, Aeromonas was isolated from 277 out of 16,857 (1.6%) samples of watery, bloody or mucous stool, from patients with diarrhoea. There was a clear seasonal pattern (less than 1% in winter, up to 3% in summer). A. caviae was isolated most frequently (49%), followed by A. sobria (35%) and A. hydrophila (15%). Some non-identifiable strains were isolated as well. Aeromonas were isolated in particular from faeces of patients aged over 70 years (predominantly A. sobria) or under 5 years (predominantly A. caviae). In 67% Aeromonas was isolated as the only possible bacterial cause of diarrhoea, but in 33% other enteropathogenic bacteria were found as well (17% Campylobacter, 14% Salmonella, 2% Shigella). In addition, all Aeromonas isolates were collected which were obtained in normal diagnostic activities in the participating laboratories, among others from blood, from pus or wound fluid, from faecal samples which did not meet the above mentioned criteria. A. caviae was the dominant species in 'other' faeces and 'various' body sites but was not isolated from blood. The results of this study do not indicate that routine examinations for Aeromonas in faeces of patients with diarrhoea are necessary.

Adolescent↗
PubMed1990

F-specific RNA bacteriophages and sensitive host strains in faeces and wastewater of human and animal origin.

Faeces of humans, pigs, cattle and chickens were investigated for the presence of somatic coliphages, F-specific bacteriophages and Escherichia coli strains sensitive to infection by F-specific phages. Attention was given to the possible effect of age and use of antibiotics on the prevalence of the FRNA phages and sensitive E. coli strains. Somatic coliphages were often detected in high numbers in all types of faeces. In contrast, FRNA phages were rarely detected in faeces from humans and cattle but more often in faeces from pigs and adult chickens. Samples from young chickens (with or without antibiotics) were consistently positive for FRNA phages (up to 3 x 10(6) pfu/g). F-specific RNA phages were found in substantial numbers (greater than 10(3) pfu/ml) in a variety of wastewaters: domestic, hospital, slaughterhouses and occasionally in 'grey water'. Their origin in wastewater was not clear. Strains from faeces usually belonged to serogroups I and IV. These types were also found in wastewater, as were group II and III strains. Serogroup II phages were abundant in wastewater of human origin but rare in faeces. Escherichia coli strains sensitive to infection by F-specific phages were common in faeces (overall 290/1081: 27%). No strains with fully depressed F-pilus synthesis were detected among the sensitive strains. It is concluded that the occurrence of F-specific RNA bacteriophages in water points to sewage pollution rather than faecal pollution; the mechanism of replication of these organisms in wastewater is not understood.

Aging↗
PubMed1990

The presence of Aeromonas in drinking water supplies in The Netherlands.

The occurrence of Aeromonas in raw, treated and distributed waters of 20 different treatment stations in the Netherlands was studied over a one-and-a-half year period. River water yielded highest numbers (greater than 10,000 cfu/100 ml) of predominantly anaerogenic strains. In open storage reservoirs for river water or dune infiltrate, numbers were usually between 1,000 and 10,000/100 ml with a majority of aerogenic strains, in particular A. sobria. River water after dune infiltration or pure dune water, collected in closed systems, as well as aerobic or anaerobic groundwater, were usually free of Aeromonas in 100 ml. Treated waters showed low counts (usually less than 10 cfu/100 ml), irrespective of raw water source. Regrowth of aeromonads occurred in 16 out of 20 distribution systems examined. Geometric means counts (2nd half of 1986) in these systems varied between 1 and 440 cfu/100 ml and maximum counts between 10 and 3300 cfu/100 ml. Aeromonas-densities were related to temperature and residence time, but not to total organic matter or heterotrophic plate counts. Regrowth occurred particularly in drinking water derived from anaerobic groundwater containing methane. A. hydrophila was the most frequently isolated species from distribution waters, but A. caviae and A. sobria were predominant in a few systems.

Aeromonas↗
PubMed1989

Complexing of copper in drinking water samples to enhance recovery of Aeromonas and other bacteria.

The presence of copper in drinking water samples at concentrations as low as 10 micrograms/l resulted in a rapid die-off of aeromonads. Coliform bacteria, heterotrophic plate count bacteria and faecal streptococci were also sensitive to copper but to a lesser degree than aeromonads. The effect was particularly noticeable in soft water (less than 3 meq/l Ca + Mg) and at pH-values below 8.0. The toxic effect of copper concentrations up to 500 micrograms/l could be neutralized for a period of up to 24 h by the addition to samples of 50 mg/l of disodium-ethylene-diamino-tetraacetate (Na2EDTA) and keeping the samples on melting ice.

Aeromonas↗
PubMed1988

Evaluation of the Anderson Baird-Parker direct plating method for enumerating Escherichia coli in water.

The direct plating (DP) method for enumerating Escherichia coli in food was adapted for water analysis by membrane filtration and a standardized protocol was described. The DP method was found to give equal or better recoveries of E. coli than a membrane filtration method using 0.1% sodium lauryl sulphate agar; the repeatability of the DP method was markedly better. The necessity to transfer membranes from the non-selective medium tryptone soy agar (TSA) to the selective medium tryptone bile agar (TBA) after pre-incubation for 4 h was considered disadvantageous for practical purposes. A double-layer method, where the membrane filter is placed on a layer of TSA poured over TBA, with incubation in an incubator that automatically switches from 37 degrees to 44 degrees C after 4 h, was found to be an acceptable alternative. Recovery of E. coli and inhibition of competitive flora were equal or only slightly less than for the standard DP method.

Bacteriological Techniques↗
PubMed1987

Virus, bacteriophages and water purification.

Water can be a vector of viral disease, but direct virological analysis of water has logistic and practical limitations. Viruses of major importance for water hygiene (e.g. hepatitis and gastro-enteritis viruses) cannot yet be grown in tissue culture. Therefore, as in bacteriological quality procedures, model organisms are required for the evaluation of virological quality of water and the effectiveness of virus removal by water treatment processes. On the basis of published information, the F specific RNA (FRNA) phages have been chosen for this purpose. For the enumeration of the phages a particular Salmonella typhimurium strain with an artificially introduced F plasmid was developed as a host strain and was found to give accurate and reliable results. FRNA phages were found in very high numbers (10(2)-10(5) pfu/ml) in all types of waste water investigated. FRNA phages are seldom found in non-faecally contaminated waste water. Surprisingly low numbers are found in faeces. FRNA phages in waste water effluent were found to be highly resistant to chloramines and relatively resistant to UV inactivation. The FRNA phages can thus effectively be used as indicator organisms for human pathogenic viruses in the evaluation of disinfection processes for water treatment plants.

Animals↗
PubMed1987

Ampicillin-dextrin agar medium for the enumeration of Aeromonas species in water by membrane filtration.

Published selective media were evaluated for the isolation of Aeromonas spp. from environmental samples by membrane filtration. Satisfactory recoveries were obtained only with mA agar (Rippey & Cabelli) and dextrin-fuchsin-sulphite agar (Schubert), but neither was sufficiently selective. The positive aspects of these two media were combined in a new medium, ampicillin-dextrin agar. Recovery from pure cultures and environmental samples was optimal at an ampicillin concentration of 10 mg/l and incubation for 24 h at 30 degrees C under aerobic conditions, and specificity was high (i.e. confirmation rate usually greater than 90%, no false negative colonies encountered). The medium can also be used for isolation of Aeromonas spp. from sea water provided that the vibriostatic agent 0/129 is added at 50 mg/l.

Aeromonas↗
PubMed1987

Proficiency testing of water microbiology laboratories in The Netherlands.

In a 3-year period, four series of simulated water samples containing selected test strains were distributed to more than 50 laboratories in The Netherlands for bacteriological testing. Participating laboratories examined the samples by enrichment or membrane filtration methods, or both, for total coliform organisms, thermotolerant coliform organisms, faecal streptococci and standard plate counts (37 degrees and 22 degrees C) according to Dutch standard methods. The results were quantitatively satisfactory: the distribution of positive and negative results with subsamples conformed to stochastic variation; the standard deviation of membrane or plate counts was usually in the range which may be expected from a Poisson distribution, and there was good correspondence between average counts in participating laboratories and those expected from controls in the organizing laboratory. Problems of a qualitative nature were frequently encountered, however. Among them were a false positive response with a strain of Enterobacter cloacae in the thermotolerant coliform test; a false positive result with Clostridium perfringens in enrichment tests for total or thermotolerant coliform organisms and false positive results with Micrococcus varians in the faecal streptococcus test by membrane filtration. It is concluded that quality assessment should be a consistent activity in water microbiology laboratories. For this purpose, stable and well characterized reference materials are needed.

Bacteria↗
PubMed1987

Bacteriophages as model organisms in water treatment.

F-specific RNA bacteriophages have great potential as model organisms for monitoring the fate of human viruses in water treatment processes. They are consistently present in large numbers in all kinds of wastewaters and their resistance to inactivation is relatively high. A simple and reliable enumeration method is available.

Bacteriophages↗
PubMed1986

[Botulism].

In view of large-scale outbreaks of botulism among waterfowl and farm animals in the Netherlands, studies were done designed to estimate the risks incurred by man. The presence of C. botulinum in the environment as well as contamination cycles and the potential for multiplication were studied. Raw materials used in the production of food were frequently found to be contaminated with types of C. botulinum pathogenic for man. The growth of C. botulinum in foods and meat preservatives other than nitrite were examined. To reduce the use of laboratory animals in research on botulism, immunological methods to detect botulinum toxins were developed.

Animals↗
PubMed1986

Bacteriophages and indicator bacteria in human and animal faeces.

In an attempt to explain the presence of F-specific (RNA) bacteriophages in waste-water, faecal material from humans and a variety of animals was examined. The phages were detected in appreciable numbers only in faeces from pigs, broiler chickens, sheep and calves but not from dogs, cows, horses and humans. Parallel examinations for somatic coliphages, thermotolerant coliforms, faecal streptococci and spores of sulphite-reducing clostridia revealed the consistent presence of these organisms in all types of samples, albeit in variable numbers. The number of F-specific bacteriophages was related to the total number of somatic coliphages, but phage counts were unrelated to bacterial counts. F-specific RNA phages were grouped by serotyping and all animal isolates were found to belong to either group I (MS2 subtype) or IV (four different subtypes). Among the group IV isolates, most belonged to well-known subtypes SP (24 isolates) or FI (18 isolates) but five isolates were related to phage ID2 and one isolate was a new subtype. In contrast with animal isolates, 19 isolates from hospital wastewater belonged to serogroups II or III.

Animals↗
PubMed1986

C-390 as sole selective agent for isolation of Pseudomonas aeruginosa from hospital waste water.

Pseudomonas aeruginosa was recovered (in numbers ranging from 10(2) to 10(5) colony-forming units per millilitre) from heavily contaminated hospital waste water when grown at 41.5 degrees C on a differential medium agar containing 9-chloro-9-(4-diethylaminophenyl)-10-phenylacridan (C-390) at a final concentration of 30 micrograms/mL. The medium appeared to be highly selective for P. aeruginosa with 95-100% of all colonies isolated from four different hospital waste waters being identified as P. aeruginosa. Many strains of P. aeruginosa isolated from hospital waste waters failed to hydrolyse casein when grown on skim milk agar and this medium appeared to restrict pigment production to only pyoverdin (detectable only under ultraviolet light). However, most strains were capable of casein hydrolysis when grown on a modified skim milk medium.

Acridines↗
PubMed1985

[Incidence of Clostridium botulinum on cattle farms].

Clostridium botulinum, mainly type B, was constantly found to be present on cattle farms. The organism was isolated both from samples of the soil of pastures and from the faeces of cattle during the winter housing period. The number of C. botulinum type B in samples of soil varied from 10 to 300 organisms per 100 grams. Contamination with C. botulinum was found to be of a similar order of magnitude on farms on which pastures are regularly dressed with sewage sludge. C. botulinum was detected in 13 per cent of the faecal samples (420 samples of one gram each). Particularly grass silage pits prepared with wilted grass were found to provide a possible link between contamination of pastures and cattle.

Animals↗
PubMed1985

A note on legionellas in whirlpools.

Water samples from 52 whirlpools (jacuzzi), water temperature 35-40 degrees C, and from 50 swimming pools, water temperature 8-30 degrees C, were investigated for the presence of Legionella pneumophila. This was isolated from 11 of 28 whirlpools with free available chlorine less than 0.3 mg/l. No legionellas were detected in 23 whirlpools with free available chlorine over 0.3 mg/l. Legionella pneumophila was found in two swimming pools. The results indicate that 0.3 mg/l of free available chlorine is sufficient to eliminate legionellas from whirlpools.

Legionella↗