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PubMed1999

Intestinal protozoa in HIV-infected patients in Apulia, South Italy.

Protozoa are important enteric pathogens in patients with human immunodeficiency virus (HIV) infection. In this study the prevalence of intestinal protozoa in 154 HIV-infected patients, with or without diarrhoea, in our region (Apulia, South Italy) was evaluated between December 1993 and February 1998. In the majority of patients CD4+ T cell count was below 200/microl. The overall prevalence of intestinal protozoa was 43/154 (27.92%). Twenty-eight (43.08%) out of 65 patients with diarrhoea and 15 (16-85%) out of 89 non-diarrhoeic patients were parasitized. In particular, in the group of 65 patients with diarrhoea the following protozoa were identified: Cryptosporidium parvum in 14 (21.54%), Blastocystis hominis in 7 (10.77%), microsporidia in 6 (9.23%), Giardia lamblia in 4 (6.15%) and Isospora belli in 1 (1.54%). Three patients were Cryptosporidium parvum-microsporidia co-infected. In patients without intestinal symptoms, prevalence was 3/89 (3.37%) for Cryptosporidium parvum, 9/89 (10.11%) for Blastocystis hominis, 1/89 (1.12%) for microsporidia and 2/89 (2.25%) for Giardia lamblia. A significant (P<0.001) correlation was observed between protozoan infection and the presence of diarrhoea. In particular, Cryptosporidium parvum and microsporidia infections were significantly (P<0.001) and P = 0.046, respectively) associated with diarrhoeal illness. Moreover, the majority of cases of cryptosporidiosis were first diagnosed in the periods of heaviest rainfall. Therefore, drinking water contamination may be a possible source of human infection in our area.

Adult↗
PubMed2002

Influence of ciliate protozoa on biochemical changes and hydrolytic enzyme profile in the rumen ecosystem.

AIMS: To assess the effect of presence or absence of rumen protozoa on fermentation characteristics and enzyme profile in growing lambs. METHODS AND RESULTS: Weaner lambs (G1, G2, G3, G4, G5 and G6 groups) were defaunated by oral administration of sodium laurel sulphate (at 8 g 100 kg(-1) body weight). The lambs of G4, G5 and G6 groups were refaunated. The roughage and concentrate ratio in the diet of G1 and G4, G2 and G5, and G3 and G6 were 50:50 (R1), 65:35 (R2) and 80:20 (R3), respectively. Daily dry matter intake was similar in defaunated and faunated lambs. However, digestibility of organic matter (OM), cellulose and gross energy were lower in defaunated lambs while crude protein (CP) digestibility was similar in both defaunated and faunated lambs. The rumen pH and NH3-N were lower (P < 0.01) while TVFA, total-N and TCA-ppt-N were higher (P < 0.01), in defaunated lambs. Ruminal activity of carboxymethyl cellulase was lower (P < 0.01) in defaunated lambs and amylase, xylanase, protease and urease were similar in faunated and defaunated lambs. Nutrient utilization, rumen metabolites and ciliate protozoal count were higher, whereas digestibility of fibre fractions was lower in high rather than low concentrate fed lambs. The rumen protozoa present before defaunation were B-type and the protozoa which re-established on refaunation were also B-type. CONCLUSIONS: Absence of ciliate protozoa decreased nutrient digestibility and increased ruminal TVFA and total-N with lower NH3-N concentration, indicating better energy and protein utilization in defaunated lambs. SIGNIFICANCE AND IMPACT OF THE STUDY: Defaunation improved energy and protein utilization in lambs.

Animal Feed↗
PubMedDate not supplied

Protozoa involved in butyric rather than lactic fermentative pattern during latent acidosis in sheep.

We used six ruminally cannulated Texel wethers to study the relative role of protozoa and lactate-metabolizing bacteria in ruminal fermentative patterns during an induced latent acidosis. The sheep were fed an alfalfa hay diet (H) and latent acidosis was induced, following a short transition period of one week, with a grain-rich acidotic diet (W, 60% wheat + 40% alfalfa hay). Ruminal pH, ruminal volatile fatty acids (VFA), lactate and NH3 concentrations, protozoa and lactate-utilizing bacterial counts, the relative proportions of three main bacteria implicated in lactate metabolism (a lactate-producing species, Streptococcus bovis, and two lactate-utilizing species, Selenomonas ruminantium, and Megasphaera elsdenii) using specific 16S-rRNA-targeting oligonucleotide probes, and lactate dehydrogenase (LDH) activity were determined for both diets. The pH parameters (mean, minimum, maximum, time and area under pH 6.0 and 5.5) measured with the W diet were indicative of a latent (i.e., subacute and maintained) acidosis. However, a butyric rather than lactic latent acidosis was observed in this study. Total ruminal lactate concentration remained at low levels with the acidotic diet (< 4 mmol x L(-1)), but changes were observed in VFA composition, which was oriented towards butyrate at the expense of acetate (P < 0.05), while propionate remained constant. In agreement with the low ruminal lactate concentration, no changes in the proportion of S. bovis 16S-rRNA were observed. The lactate-metabolizing bacterial population also remained fairly constant in number, proportion and activity. The increase in butyrate concentration was accompanied by a proliferation of entodiniomorphs (P < 0.01). These results suggest that the protozoa limited lactate accumulation and possibly also the decrease in pH during latent acidosis. Experiments with defaunated and faunated sheep could provide further evidence of the role of protozoa in the development of rumen latent acidosis.

Acidosis↗
PubMed1992

Legionella pneumophila mip gene potentiates intracellular infection of protozoa and human macrophages.

Legionella pneumophila is an intracellular parasite of freshwater protozoa and human macrophages. Recent studies determined that the macrophage infectivity potentiator (Mip) surface protein, a prokaryotic homolog of the FK506-binding proteins, is required for optimal infection of macrophages. To determine whether Mip is also involved in L. pneumophila infection of protozoa, we examined the ability of a strain lacking Mip to parasitize Hartmannella amoebae and Tetrahymena ciliates. After 3 days of incubation, approximately 1000-fold fewer bacteria were recovered from protozoan cocultures infected with the Mip- strain than from those cocultures infected with an isogenic Mip+ strain. The mip mutant was, however, not impaired in its ability to bind to amoebae cell surfaces, indicating that Mip is involved in bacterial resistance to intracellular killing and/or intracellular multiplication. These data suggest that L. pneumophila employs similar genes and mechanisms to infect human cells and protozoa. Furthermore, they support the hypothesis that the ability of L. pneumophila to parasitize macrophages and hence to cause human disease is a consequence of its prior adaptation to intracellular growth within protozoa.

Amoeba↗
PubMed1986

The passage of protozoa from the reticulo-rumen through the omasum of sheep.

1. Protozoa in rumen contents and omasal effluent of growing wethers were counted. The wethers were equipped with rumen and abomasal cannulas, and omasal sleeves attached to the omasal-abomasal orifice. Rumen fluid dilution rates were elevated by continuous infusions of hypertonic mineral solutions (3-4 litres/d) for 24 d. Rumen contents and omasal effluent were sampled between 9 and 21 h during the last 10 d of each experiment. 2. Protozoal concentrations in omasal effluent were only 0.2-0.3 those found in the rumen under normal conditions. The ratio of protozoal concentrations in rumen: those in omasal effluent was for small Diplodinium spp. 4.6 (SD 0.9), for Ophryoscolex spp. 4.3 (SD 1.0), for Dasytricha ruminantium 4.0 (SD 0.5), for Isotricha spp. 3.8 (SD 0.8), for Entodinium spp. 3.6 (SD 0.9) and for Polyplastron multivesiculatum 2.6 (SD 0.5). 3. Elevation of rumen fluid dilution rate by 20 and 55% respectively, increased protozoal concentrations in omasal effluents from 22 to 33% and from 31 to 47% those in rumen contents. The apparent residence times of protozoa in the rumen were decreased 50% by the infusion of a mineral-salt solution. The increase in rumen fluid dilution rate had no significant effect on concentrations of protozoa in the rumen or on the differences of the apparent residence times between different species. The apparent residence time of holotrichs remained the same before and after infusion of the mineral-salt solution. 4. Apparent residence times of individual species of protozoa in the rumen were, under normal feeding conditions, 2.55 d, and were four to six times longer than the mean residence time of CrEDTA in the rumen.

Animals↗
PubMed1997

Influence of foliage from African multipurpose trees on activity of rumen protozoa and bacteria.

Samples and extracts of foliage from African multipurpose trees were screened for their effects on rumen protozoa and bacteria with a view to predicting their safety as feed supplements and for identifying species with potential antiprotozoal activity. The species tested were Acacia aneura, Chamaecytisus palmensis, Brachychiton populneum, Flindersia maculosa, Sesbania sesban, Leucaena leucocephala and Vernonia amyedalina. Antimicrobial effects were mild except for S. sesban, which was highly toxic to rumen protozoa in vitro, and A. aneura, which was toxic to rumen bacteria. The antiprotozoal factor in S. sesban was apparently associated with the fraction of the plant containing saponins. When S. sesban was fed to sheep, protozoal numbers fell by 60% after 4 d, but the population recovered after a further 10 d. In vitro experiments demonstrated that washed protozoa from later times were no more resistant to S. sesban than on initial exposure, suggesting that other micro-organisms, probably the bacteria, adapted to detoxify the antiprotozoal agent. Thus S. sesban may be useful in suppressing protozoa and thereby improving protein flow from the rumen, but only if the bacterial metabolism of the antiprotozoal factor can be avoided.

Africa↗
PubMed1991

Total protozoa counts and ammonia in the rumen of mature dry Friesian cows on hay-based rations.

The present work was an attempt to determine whether the variations in ruminal ammonia concentrations could be directly correlated to corresponding changes in total protozoa numbers of cattle. Four dry Friesian cows fed with hay-based rations were used through several experiments in which the twice daily feeding (6.15-15.30 h) as well as a 30 h-fasting period were studied. Simultaneously to a continuous or a regular collection of rumen liquor (for NH3), samples of rumen contents (for total protozoa numbers) were regularly withdrawn from the ventral sac. Any definite nycthemeral cycle of the protozoa numbers could not be related to feeding time. Moreover, no significant relationship could be found between the ruminal ammonia and the corresponding total protozoa numbers measured in the nocturnal interprandial period or during starvation. The data suggest that the nycthemeral ammonia profiles recorded in cattle are not directly related to protozoal activity.

Ammonia↗
PubMed1990

Ingested Listeria monocytogenes survive and multiply in protozoa.

Listeria monocytogenes cells are ingested by protozoa such as Acanthamoeba sp. or Tetrahymena pyriformis. However, they are not killed, but survive within the protozoa and may multiply intracellularly. The protozoa are lysed within about 8 days, releasing viable L. monocytogenes. No co-existence was observed between L. monocytogenes and Tetrahymena. A co-culture of L. monocytogenes and Acanthamoeba sp. showed a decay of locomotive forms and release of listeria from vegetative protozoan cells whereas the bacteria were destroyed in cysts. These phenomena provide an insight into the pathogenesis of listeria infection in man and warm-blooded animals because intracellular processes occurring in protozoa after ingestion of L. monocytogenes may be similar to those observed in mammalian cells.

Acanthamoeba↗
PubMed1996

Inhibition by 1,10-phenanthroline of the breakdown of peptides by rumen bacteria and protozoa.

The rate of peptide breakdown in the rumen frequently exceeds the rate at which the amino acids released can be used for microbial growth. The final step in this often wasteful process involves the cleavage of dipeptides. The main rumen bacterial species with high dipeptidase activity, Prevotella ruminicola, Fibrobacter succinogenes, Lachnospira multipara and Megasphaera elsdenii, had activities which were inhibited > 95% by 1,10-phenanthroline, a chelator of divalent metal ions and metalloprotease inhibitor. Dipeptidase activity in digesta taken from the rumen of sheep decreased by 33% in the presence of 1,10-phenanthroline, while mixed bacteria from the same samples were inhibited by 80% and the activity of mixed protozoa decreased by only 15%. Thus a substantial amount of dipeptide breakdown appears to be due to ciliate protozoa in the mixed population. Extensive washing of the protozoa increased the sensitivity of protozoal dipeptidase activity to 1,10-phenanthroline, suggesting that protozoa too have a metallo-dipeptidase activity but that it is normally protected from inhibition by 1,10-phenanthroline. Breakdown of the pentapeptide, Ala5, was also inhibited 27% by 1,10-phenanthroline in the mixed population, and when Trypticase, a pancreatic casein hydrolysate containing a mixture of oligopeptides, dipeptides and amino acids, was incubated with rumen fluid, the production of ammonia and free amino groups was inhibited 71% by 1,10-phenanthroline. It was concluded that metal ion chelation inhibits oligopeptidase and dipeptidase activities of rumen micro-organisms and may be a means of controlling ammonia production from peptides in the rumen.

Ammonia↗
PubMed1995

Interactions between rumen anaerobic fungi and ciliate protozoa in the degradation of rice straw cell walls.

Suspensions of mixed rumen protozoa were added to incubations of the anaerobic fungus Neocallimastix patriciarum with rice straw cell walls. The protozoa did not influence the dry matter lost from the straw, or the solubilization of monosaccharides, but they had a marked effect on the fermentation products formed. Studies with 14C-labelled protozoa suggested that the presence of protozoa reduced the fungal carboxymethylcellulase activity to around half of that found in pure cultures of the fungus.

Anaerobiosis↗
PubMed1987

The number of species of rodent coccidia and of other protozoa.

About 447 species of coccidia have been named from the 1687 living, known species of rodents; 207 host species, 92 host genera, and 15 host families are represented; this is about 12% of the known species of rodents. About 4600 species of apicomplexan protozoa have been named. Assuming that the same proportion of the total number of apicomplexan species has been named as of the coccidian species, there must actually be about 38,333 species of apicomplexan protozoa. There are 5.4 times as many protozoan genera as of apicomplexan genera. Assuming that the number of species in each genus is the same for all the protozoa as it is for the Apicomplexa, there may actually be 206,998 species of protozoa. This may be too conservative an estimate. Based on other criteria, an estimate of over 20 million species could be made.

Animals↗
PubMedDate not supplied

Hydrogen production by rumen holotrich protozoa: effects of oxygen and implications for metabolic control by in situ conditions.

Experiments with washed suspensions of holotrich protozoa (Isotricha spp. and Dasytricha ruminantium) showed that both organisms have an efficient O2-scavenging capability (apparent Km values 2.3 and 0.3 microM, respectively). Reversible inhibition of H2 production increased almost linearly with increasing O2 up to 1.5 microM; higher levels of O2 gave irreversible inhibition. In situ determinations of H2, CH4, O2 and CO2 in ovine rumen liquor, using a membrane inlet mass spectrometer probe, indicated that O2 was present before feeding at 1-1.5 microM and decreased to undetectable levels (less than 0.25 microM) within 25 min after feeding. A transient increase in O2 concentration after feeding occurred only in defaunated animals and resulted in suppression of CH4 and CO2 production. The presence of washed holotrich protozoa decreases the O2 sensitivity of CH4 production by suspensions of a cultured methanogenic bacterium Methanosarcina barkeri. It is concluded that holotrich protozoa play a role in ruminal O2 utilization as well as in the production of fermentation end products (especially short-chain volatile fatty acids) utilized by the ruminant and H2 utilized by methanogenic bacteria. These hydrogenosome-containing protozoa thus both control patterns of fermentation by influencing O2 levels, and are themselves regulated by the low ambient O2 concentrations they experience in the rumen.

Animals↗
PubMedDate not supplied

Rumen ciliate protozoa of the blue duiker (Cephalophus monticola), with observations on morphological variation lines within the species Entodinium dubardi.

Protozoal concentrations were determined in rumen and cecal contents of 20 blue duikers (Cephalophus monticola). Ten animals of each sex were fed either a high concentrate or high roughage diet. Rumen protozoa were present in 19 of the 20 animals and concentrations ranged from 4.5 to 33.7 x 10(6) per g of rumen contents. At the higher concentrations, protozoal cells equaled between 30-40% of the total rumen contents volume. No protozoa were found in cecal contents. Weight of rumen contents was higher in females than in males (P < 0.01), and rumen protozoa concentrations were higher in males (P < 0.05) and in those animals fed the high concentrate diet (P < 0.05). All the protozoa were identified as belonging to a single species, Entodinium dubardi. However, an average of about 30% of the E. dubardi cells varied from the typical morphology of this species. These cells appeared to be on variation lines leading toward 7-10 other non-caudate species of Entodinium. The present data were used to evaluate and discuss the concept of variation lines within E. dubardi.

Animals↗
PubMedDate not supplied

The interaction of protozoa with their potential prey bacteria in the rhizosphere.

Extensive colonization of the rhizosphere by beneficial bacteria is desirable but it is not yet clear whether the feeding patterns of protozoa exert any ecological impact on the competence of bacteria in the rhizosphere. To determine whether the successful colonization of the rhizosphere by bacteria can be explained by inherent abilities of the bacteria to resist predation, six bacteria categorized as poor, mediocre or good rhizosphere colonists were tested. The populations of protozoa in the rhizosphere consistently increased to a maximum density in two days but then declined to a stable level. Grazing by protozoa increased the doubling time of all of the test bacteria but did not significantly affect the final densities of bacteria in the rhizosphere. The differences in the colonization ability of the six bacteria tested were not attributable to inherent differences in their susceptibility to predation by protozoa.

Acanthamoeba↗
PubMed1979

Mode of attack on orchardgrass leaf blades by rumen protozoa.

Leaf blade sections of orchardgrass were incubated with rumen fluid and examined by scanning and transmission electron microscopy for the mode of attack on tissues by rumen protozoa. Rumen protozoa resembling Epidinium ecaudatum from caudatum degraded forage tissue in diluted, whole rumen fluid suspensions of microbes containing 1.6 mg of streptomycin per ml, which inhibited bacterial fiber-digesting activity. Cell walls of mesophyll, parenchyma bundle sheath, and epidermis became swollen and frayed to reveal a microfibrillar network and loss of electron density, indicating partial degradation. Then the protozoa ingested whole cells and fragments of cell walls with the aid of their cilia. Plant cells with partially degraded walls as well as chloroplasts without walls were present within the protozoa. These entodiniomorphs digested orchardgrass leaves by partially degrading the plant cell walls apparently by extracellular enzymes and then ingestion of the plant cells and cell wall fragments.

Journal Article↗
PubMed1984

Evaluation of subsampling and fixation procedures used for counting rumen protozoa.

Total numbers of protozoa can be significantly lower in rumen fluid than in whole rumen contents, depending on the time of sampling and the procedure used to separate the fluid and solid fractions. Moreover, generic distribution in rumen fluid was significantly affected in all cases tested. The percentage of Entodinium spp. increased, whereas percentages of Diplodinium spp. and Ophryoscolex spp. decreased. Microscopic observation of fresh and fixed rumen contents did not indicate any marked attachment of protozoa to particulate matter. In addition, dilution of whole rumen contents with water, 5 mM sucrose, or 0.1% Tween 80 before fixation did not affect total numbers or generic composition of protozoa. It was thus concluded that attachment to feed particles is probably not a problem in counting procedures. Blending of whole rumen contents to facilitate subsampling caused a decrease in numbers of protozoa. The concentration of formaldehyde used for preservation of rumen contents, 4, 10, or 18.5%, did not affect the total count.

Animals↗
PubMed1987

Distribution of protozoa in subsurface sediments of a pristine groundwater study site in oklahoma.

Sediment core samples were obtained at a groundwater study site in Oklahoma in January and June 1985. Most-probable-number estimates showed that protozoan numbers declined steeply with depth in subsoil. Flagellates and amoebae dominated the protozoan population, which declined to a most probable number of 28 . g (dry weight) in a clay loam layer at the bottom of the unsaturated zone. Samples from a texturally variable interface zone between 3 and 4 m down also were variable in their content of protozoa. Four contiguous clay loam samples in a single core from this zone contained variable numbers of amoebae ranging from 0.2 to 44 . g (dry weight). However, a sandy clay loam layer at the bottom of the core contained a mixture of flagellates and amoebae with a combined population density of 67 . g (dry weight). A slow-growing filose amoeba was isolated from interface zone samples and was tentatively classified in a new family in the order Aconchulinida. Protozoa were not detected in the saturated zone except in a very permeable gravelly, loamy sand layer at a depth of approximately 7.5 m. Low numbers (4 to 6 . g [dry weight]) of surface-type flagellates and amoebae, as well as the filose amoeba seen in the interface zone, were observed in this layer. Acid-treated and untreated samples contained equivalent numbers of protozoa, showing that the majority of protozoa in the layer at 7.5 m and the interface zone samples were encysted. Increased numbers of bacteria also were found in the layer at 7.5 m, indicating that it was biologically more active than other saturated-zone layers. Cyanobacteria grew in illuminated samples from this layer, suggesting that it may be connected hydrologically to a nearby river.

Journal Article↗
PubMed1990

Omasal ciliated protozoa in cattle, bison, and sheep.

Omasal contents were collected from slaughtered cattle (n = 54), bison (n = 15), and sheep (n = 40) to determine numbers and generic distribution of ciliated protozoa. Total protozoan numbers were significantly lower in omasal contents than in ruminal contents of all three species, but the percent composition of all protozoan genera was similar between omasal and ruminal populations. The highest numbers of omasal protozoa found were 7.61 X 10(5)/g in cattle, 7.01 X 10(5)/g in bison, and 1.29 X 10(6)/g in sheep. Omasal dry matter was significantly higher than ruminal dry matter in all species and ranged up to 51.5% in cattle fed high-concentrate diets. The omasal pH was similar to the ruminal pH in all species. The number of omasal laminae averaged 149, 145, and 74 for cattle, bison, and sheep, respectively. Although protozoan concentrations in omasal contents were approximately 80% lower than those in ruminal contents, the omasum harbored relatively high numbers of ciliated protozoa. The resident omasal protozoa are extremely difficult to remove, particularly in cattle, and apparently are responsible for reinoculating transiently defaunated rumens.

Animals↗