Asymptomatic Isolates Research Articles

Plant wounding and Ophiostoma mitovirus 3a (OMV3a) influence infection of creeping bentgrass by Sclerotinia homoeocarpa

Colonization and lesion development by virulent, asymptomatic and hypovirulent isolates of Sclerotinia homoeocarpa on nonwounded (NW) and wounded (W) leaves of creeping bentgrass were characterized. Hypovirulent and asymptomatic isolates contain the fungal virus, Ophiostoma mitovirus 3a, and virulent isolates are virus-free. On NW leaves, all isolates infected leaves with appressoria along cell walls and through stomata by 48 hours post-inoculation (hpi). Inter- and intracellular hyphae formed on heavily colonized, NW leaves at 96 hpi. Wound-inoculated grass had a colonization front characterized by inter- and intracellular hyphal colonization within nonsymptomatic tissues at 8 hpi by direct infection of the wound site. The colonization front grew ahead of symptom development for 50 hpi on both NW and W leaves. In contrast to virulent and asymptomatic isolates, the hypovirulent isolate seldom colonized more than 30% of leaf tissue of the NW or W leaves. Callose accumulation under fungal appressoria, oxalate oxidase activity, and hydrogen peroxide accumulation at lesion borders were also demonstrated. The results indicate that S. homoeocarpa is capable of colonizing creeping bentgrass without causing visible symptoms. In addition, the fungus causes disease more rapidly on W than NW grass, and the etiology of virulent, asymptomatic and hypovirulent isolates was similar. The results of this study contribute to our understanding of the basic biology of S. homoeocarpa and may influence integrated management practices.

Predictive value of Escherichia coli susceptibility in strains causing asymptomatic bacteriuria for women with recurrent symptomatic urinary tract infections receiving prophylaxis

A significant proportion of women develop a recurrence following an initial urinary tract infection (UTI). In women with recurrent UTI, the predictive value of asymptomatic bacteriuria (ASB) for the development of a subsequent UTI has not yet been established and it is not known whether information from an asymptomatic sample is useful in guiding antimicrobial therapy. To address these questions, we used data that originated from the ‘Non-antibiotic prophylaxis for recurrent urinary tract infections’ (NAPRUTI) study: two randomized controlled trials on the prevention of recurrent UTI in non-hospitalized premenopausal and postmenopausal women (n = 445). During 15 months of follow-up, no difference was observed in the time to a subsequent UTI between women with and without ASB at baseline (hazard ratio: 1.07, 95% CI 0.80–1.42). The antimicrobial susceptibility and pulsed-field gel-electrophoresis (PFGE) pattern of 50 Escherichia coli strains causing a UTI were compared with those of the ASB strain isolated 1 month previously. The predictive values of the susceptibility pattern of the ASB strain, based on resistance prevalence at baseline, were ≥76%, except in the case of nitrofurantoin-and amoxicillin-clavulanic acid-resistance. Asymptomatic and symptomatic isolates had similar PFGE patterns in 70% (35/50) of the patients. In the present study among women with recurrent UTI receiving prophylaxis, ASB was not predictive for the development of a UTI. However, the susceptibility pattern of E. coli strains isolated in the month before a symptomatic E. coli UTI can be used to make informed choices for empirical antibiotic treatment in this patient population.

Effects of symptomatic and asymptomatic isolates of Blastocystis hominis on colorectal cancer cell line, HCT116

The pathogenesis of Blastocystis hominis in human hosts has always been a matter of debate as it is present in both symptomatic and asymptomatic individuals. A recent report showed that B. hominis isolated from an asymptomatic individual could facilitate the proliferation and growth of existing cancer cells while having the potential to downregulate the host immune response. The present study investigated the differences between the effects of symptomatic and asymptomatic derived solubilized antigen of B. hominis (Blasto-Ag) on the cell viability and proliferation of colorectal cancer cells. Besides that, the gene expression of cytokine and nuclear transcriptional factors in response to the symptomatic and asymptomatic B. hominis antigen in HCT116 was also compared. In the current study, an increase in cell proliferation was observed in HCT116 cells which led to the speculation that B. hominis infection could facilitate the growth of colorectal cancer cells. In addition, a more significant upregulation of Th2 cytokines observed in HCT116 may lead to the postulation that symptomatic Blasto-Ag may have the potential in weakening the cellular immune response, allowing the progression of existing tumor cells. The upregulation of nuclear factor kappa light chain enhancer of activated B cells (NF-κB) was observed in HCT116 exposed to symptomatic Blasto-Ag, while asymptomatic Blasto-Ag exhibited an insignificant effect on NF-κB gene expression in HCT116. HCT116 cells exposed to symptomatic and asymptomatic Blasto-Ag caused a significant upregulation of CTSB which lead to the postulation that the Blasto-Ag may enhance the invasive and metastasis properties of colorectal cancer. In conclusion, antigen isolated from a symptomatic individual is more pathogenic as compared to asymptomatic isolates as it caused a more extensive inflammatory reaction as well as more enhanced proliferation of cancer cells.

Ophiostoma mitovirus 3a, ascorbic acid, glutathione, and photoperiod affect the development of stromata and apothecia by Sclerotinia homoeocarpa

Hypovirulence in Sclerotinia homoeocarpa is associated with infection by Ophiostoma mitovirus 3a (OMV3a). OMV3a is also present in asymptomatic isolates, with growth and virulence comparable to that of virus-free isolates. Hypovirulent isolates have impaired mitochondrial function resulting in increased activity of the alternative oxidase pathway, which is implicated in the reduction of reactive oxygen species in other fungi. In this study, hypovirulent, asymptomatic, and virus-free isolates were grown on potato dextrose agar amended with ascorbic acid or glutathione and were incubated under various photoperiods to determine the importance of reactive oxygen species, light, and OMV3a infection for differentiation of stromata and apothecia by S. homoeocarpa. Hypovirulent isolates did not form stromata or apothecia. Glutathione and darkness reduced stromata size and apothecia production by virulent and asymptomatic isolates. Apothecia formed under several different photoperiods, and ascorbic acid increased apothecia production. Ascospores were not detected in these apothecia. The results suggest that hypovirulence, light, and the superoxide radical are important factors in the formation of stromata and apothecia by S. homoeocarpa isolates. This is the first report of sterile apothecia production by North American isolates of S. homoeocarpa and provides a starting point for attempts to produce fertile apothecia.

The influence of Ophiostoma mitovirus-3a (OMV3a) on the respiration and growth of the dollar spot pathogen, Sclerotinia homoeocarpa (Bennett)

Sclerotinia homoeocarpa is the causal agent of dollar spot disease of turfgrass. Although both asymptomatic and hypovirulent isolates of S. homoeocarpa contain the mitochondrial virus Ophiostoma novo-ulmi mitovirus 3a (OMV3a), only asymptomatic isolates display growth rates and virulence levels comparable to that of virus-free isolates. In this study, the respiration and growth of asymptomatic, hypovirulent and virulent isolates of S. homoeocarpa were characterized using antimycin A (AA) as a complex III inhibitor, and salicylhydroxamic acid (SHAM) as an alternative oxidase inhibitor. Results of this study indicate that alternative oxidase contributes substantially to respiration by hypovirulent isolates. All S. homoeocarpa isolates appear to utilize the alternative pathway to some extent; however, hypovirulent isolates demonstrated a substantial increase in AOX transcription relative to asymptomatic and virulent isolates. These results demonstrate that OMV3a infection interferes with the normal function of mitochondria in S. homoeocarpa in hypovirulent isolates.

Identification of an avirulent Entamoeba histolytica strain with unique tRNA-linked short tandem repeat markers

Highly polymorphic, non-coding short tandem repeats (STR) are scattered between the tRNA genes in Entamoeba histolytica in a unique tandemly arrayed organization. STR markers that correlate with the virulence of individual E. histolytica strains have recently been reported. Here we evaluated the usefulness of tRNA-linked STR loci as genetic markers in identifying virulent and avirulent strains of E. histolytica from 37 Japanese E. histolytica samples (12 diarrheic/dysenteric, 20 amebic liver abscess (ALA), and 5 asymptomatic cases). Twenty three genotypes, assigned by combining the STR sequence types from all 6 STR loci, were identified. One to 8 new STR sequence types per locus were also discovered. Genotypes found in asymptomatic isolates were highly polymorphic (4 out of 5 genotypes were unique to this group), while in symptomatic isolates, almost half of the genotypes were shared between diarrhea/dysentery and ALA. One asymptomatic isolate (KU27) showed unique STR patterns in 4 loci. This strain, though associated with the typical pathogenic zymodeme II, failed to induce amebic liver abscess by animal challenge, which suggests that inherently avirulent E. histolytica strains exist, that are associated with unique genotypes. Furthermore, STR genotyping and in vivo challenge of 2 other asymptomatic isolates (KU14 and KU26) verified the covert virulence of these strains.

Identification of Blastocystis hominis isolates from asymptomatic and symptomatic patients by PCR

Despite years of study, the pathogenic role of Blastocytis hominis is still controversial. Genotypic differences between the asymptomatic and symptomatic isolates should assist in determining the pathogenicity of Blastocystis. In this study, we genotyped 32 Blastocystis isolates obtained from 12 asymptomatic healthy individuals and 20 symptomatic patients pain by polymerase chain reaction using known seven kinds of sequence tagged site primers in this study. When we compared genotype of Blastocystis isolates between the symptomatic and asymptomatic patient group, we found that subtype3 is the most dominant genotype in asymptomatic individual (9/12) and subtype1 determined all of symptomatic patients (20/20).

Western Ontario Regional Meeting, 2008

Biological control products reduce the inoculum of Sclerotium cepivorum, the causal agent of onion white rot. S. Balint, G.J. Boalnd, and M.R. McDonald. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; and (G.J.B.) Department of Environmental Biology, Bovey Building, University of Guelph, Guelph, ON N1G 2W1, Canada Verticillium resistance in tomato is a concerted effort of early and late defense response genes. C.D.M. Castroverde, H.O. Shittu, R.N. Nazar, and E.J. Robb. Department of Molecular and Cellular Biology, College of Biological Science Axelrod Building 201, University of Guelph, Guelph, ON N1G 2W1, Canada The molecular identification and characterization of host proteins associated with soybean mosaic virus infection X. Cui and A. Wang. Southern Crop Protection and Food Research Centre, Agriculture and Agri0Food Canada, 1391 Sandford Street, London, ON N5V 4T3, Canada Multi-site mutations in β-tubulin gene sequences are involved in thaibendazole resistance in Penicillium spp. collected from Southern Ontario. M. Czerwinski, V. popovic, and D. Errampalli. Southern Crop Protection and Food Research Centre, Agriculture and Agri-Food Canada, Vineland Station, 4902 Victoria Avenue North, ON L0R 2E0, Canada Effect of seeding date and fungicide on incidence and severity of clubroot of Asian vegetables. K.C. Kalpana, M.R. McDonald, B.D. Gossen, and S.M Westerveld. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; (B.D.G.) Saskatoon Research Centre, Agriculture and Agri-Food Canada, 107 Science Place, Saskatoon, SK S7N 0X2, Canada; and (S.M.W.) Simcoe Research Station, Department of Plant Agriculture, University of Guelph, 1283 Blueline Road, P.O. Box 587, Simcoe,On N3Y 4N5, Canada A novel technology to extract nucleic acids from defferent environmental samples including plant, water, and soil W.-S. KIm and Y. Haj-Ahmad. (W.-S.K., Y.H.-A.) Norgen Biotek Corp., 3430 Schmon Parkway, Thorold, ON L2V 4Y6, Canada; and (Y.H.-A.) Brock University, 500 Glenridge Avenue, St.Catherines, ON L2S 3A1, Canada Reactive oxygen species scavengers and light influence the formation of stroma and apothecia by virulent, asymptomatic, and hypovirulent isolates of Sclerotinia homoeocarpa A.M. Orshinsky and G.J. Boland. Department of Environmental Biology, Bovey Building, University of Guelph, Guelph, ON N1G 2W1, Canada Detecting ascospores of Sclerotinia sclerotiorum in carrot crops in Ontorio — prelude to regional level forecasting of sclerotinia rot of carrot M. Parker, M.R. McDonald, and G.J. Boland. Department of Plant Agriculture, Crop Science Building, University of Guelph, 50 Stone Road East, Guelph, ON N1G 2W1, Canada; and (G.J.B.) Departmeny of Environmental Biology, Bovey Building, University of Guelph, Guelph, ON N1G 2W1, Canada Differential gene expression in tomatoes during dual infections with an endophytic and a pathogenic Verticillium H.O. Shittu, C.D.M. Castroverde, R.N. Nazar and J. Robb. Departmeny of Molecular and Cellular Biology, College of Biological Science, Axelrod Building 201, University of Guelph, Guelph, ON N1G 2W1, Canada Deoxynivalenol (DON), 15-ADON, and 3-ADON level in wheat in Ontario. L. Tamburic- Ilincic, D. Gaba, T. Nowicki, and A. Schaafsma. Ridgetown Campus, University of Guelph, 120Main Street East, Ridgetown, ON N0P 2C0, Canada; and (D.G., T.N.) Grain Research Laboratory, Canadian Grain Commission, 1404-303 Main Street, Winnipeg, MB R3C 3G8, Canada

Phenotypic and genotypic characterisation of Blastocystis hominis isolates implicates subtype 3 as a subtype with pathogenic potential

Despite frequent reports on the presence of Blastocystis hominis in human intestinal tract, its pathogenicity remains a matter of intense debate. These discrepancies may be due to the varying pathogenic potential or virulence of the isolates studied. The present study represents the first to investigate both phenotypic and genotypic characteristics of B. hominis obtained from symptomatic and asymptomatic individuals. Symptomatic isolates had a significantly greater size range and lower growth rate in Jones' medium than asymptomatic isolates. The parasite cells of symptomatic isolates exhibited rougher surface topography and greater binding affinity to Canavalia ensiformis (ConA) and Helix pomatia (HPA). The present study also identifies further phenotypic characteristics, which aided in differentiating the pathogenic forms from the non-pathogenic forms of B. hominis. Blastocystis subtype 3 was found to be correlated well with the disease.

Pathophysiological variability of different genotypes of human Blastocystis hominis Egyptian isolates in experimentally infected rats

The genotyping of Blastocystis hominis clinical isolates obtained from 28 gastrointestinal symptomatic patients and 16 asymptomatic individuals were identified by polymerase chain reaction using sequenced-tagged site (STS) primers. Then, pathophysiological variability between different B. hominis genotypes was evaluated in experimentally infected rats. Only four B. hominis subtypes (1, 2, 3, and 4) were detected (18.2%, 9.1%, 54.5%, and 18.2%, respectively) in human isolates. In symptomatic isolates, subtypes 1, 3, and 4 were detected in 8 (28.6%), 16 (57.1%), and 4 (14.3%) patients, respectively. In asymptomatic isolates, subtypes 2, 3, and 4 were identified in 4 (25%), 8 (50%), and 4 (25%), respectively. Subtype 3 was the commonest in humans. Different degrees of pathological changes were found among infected rats by symptomatic subtypes compared with asymptomatic subtypes. The moderate and severe degrees of pathological changes were found only in symptomatic subtypes infected rats while mild degree was found only in asymptomatic subtypes infected rats. Only subtype 1 induced mortality rate with 25% among infected rats. On evaluation of the intestinal cell permeability in the Ussing chamber, a prominent increase in short circuit current (DeltaIsc) was found in symptomatic subtype 1 compared to symptomatic subtypes 3 and 4 infected rats. Minimal effects were found in the asymptomatic and control groups. The results proved that subtype 1 was clinically and statistically highly relevant to the pathogenicity of B. hominis while subtype 2 was irrelevant. Also, the results suggest the presence of pathogenic and nonpathogenic strains among subtypes 3 and 4.

Genotypic diversity and antimicrobial resistance in asymptomatic Salmonella enterica serotype Typhimurium DT104

The recent emergence of multidrug-resistant Salmonella enterica subspecies enterica serotype Typhimurium phage-type DT104 represents a challenge to health workers from both human and veterinary medicine. In an effort to develop effective control strategies, it is vital to characterize accurately the extent of genetic and phenotypic variation present in the pathogen population. While previous studies have focused on disease-associated populations, we report the genetic diversity and the diversity in antimicrobial resistance associated with asymptomatic Salmonella Typhimurium DT104 isolates found in pigs. Using pulsed-field gel electrophoresis ( XbaI and SpeI), we identified 62 different genotypes associated to 13 different antimicrobial resistant phenotypes among 80 asymptomatic DT104 isolates collected from the Canadian swine industry. When rarefaction curves of a subsample the asymptomatic isolates were compared to that of disease-associated isolates from a similar spatial and temporal scale, we identified significantly more genotypes among the asymptomatic populations with 27 PFGE patterns against 23.0 ± 1.4 (95% confidence intervals) in the latter. Also, using Simpson's diversity index, we observed considerably higher genetic and phenotypic diversity in the asymptomatic isolates within herds and detected possible patterns of periodic selection within the disease-associated population. We thus concluded that an important aspect of Salmonella population structure and ecology is overlooked in investigations of disease-associated isolates.

Differential transcription profiles in Trypanosoma cruzi associated with clinical forms of Chagas disease: Maxicircle NADH dehydrogenase subunit 7 gene truncation in asymptomatic patient isolates

The majority of individuals in the chronic phase of Chagas disease are asymptomatic (indeterminate form). Every year 2–3% of these individuals develop severe clinical manifestations (cardiac and digestive forms). In this study a Trypanosoma cruzi DNA microarray was used to compare the transcript profiles of six human isolates: three from asymptomatic and three from cardiac patients. Seven signals were expressed differentially between the two classes of isolates, including tryparedoxin, surface protease GP63, cyclophilin, some hypothetical proteins and the pre-edited maxicircle gene NADH dehydrogenase subunit 7 (ND7). The approximately 30-fold greater signal in cardiac strains for ND7 was the most pronounced of the group, and differential levels of pre-edited ND7 transcript confirmed the microarray analysis. The ND7 gene from asymptomatic isolates showed a deletion of 455bp from nt 222 to nt 677 relative to ND7 of the CL Brener reference strain. The ND7 gene structure correlated with disease manifestation for 20 isolates from clinically characterised, chronic phase patients. The ND7 lesion produces a truncated product that could impair the function of mitochondrial complex I. Possible links between the integrity of the electron transport chain and symptom presentation are discussed. We propose that ND7 and other genes of the pathway constitute valuable targets for PCR assays in the differential diagnosis of the infective T. cruzi strain. While this hypothesis requires validation by the examination of additional recent parasite isolates from patients with defined pathologies, the identification of specific molecular markers represents a promising advance in the association between parasite genetics and disease pathology.

PCR fingerprinting of Blastocystis isolated from symptomatic and asymptomatic human hosts

Genomic DNA from 16 Blastocystis hominis isolates comprising of eight asymptomatic isolates (A1-A8) and eight symptomatic isolates (S1-S8) was amplified by arbitrarily primed polymerase chain reaction (AP-PCR) using 38 arbitrary 10-mer primers. Six primers (A10, B5, C20, D1, F6, and F10) generated reproducible DNA fingerprints. AP-PCR amplification revealed similar DNA fingerprints among all symptomatic isolates (S1-S8) with common bands at 850 bp using primer A10, 920 bp using primer B5, and 1.3 kbp using primer D1. Isolates A1, A3, A4, A5, A6, and A7 showed similar DNA banding patterns and all asymptomatic isolates (A1-A8) shared a major band at 1 kbp using primer B5. Isolates A2 and A8 showed distinct DNA banding patterns that differed from the remainder of the isolates. The results of the phylogenetic analyses showed that all symptomatic isolates (S1-S8) formed a clade with >70% similarity among the isolates and which were clearly separate from asymptomatic isolates A1, A3, A4, A5, A6, and A7. Asymptomatic isolates A2 and A8 formed two distinct and separate clades. AP-PCR revealed higher genetic variability within the asymptomatic isolates than within the symptomatic isolates. The present study suggests that AP-PCR can be a valuable method for differentiating between isolates of B. hominis and our results support the hypothesis that our asymptomatic and symptomatic B. hominis isolates may represent two different strains/species with varying pathogenic potential.

Trichomonas vaginalis: random amplified polymorphic DNA analysis of isolates from symptomatic and asymptomatic women in India

Trichomonas vaginalis, the causative agent for human trichomoniasis, is a protozoan parasite. Trichomoniasis is the most common non-viral sexually transmitted disease. The infection in women may be asymptomatic or may lead to severe vaginitis, cervicitis and severe sequelae. Despite its high prevalence, the genetic variability and factors leading to symptomatic infection have been poorly understood. One thousand women in childbearing age group were screened for the presence of T. vaginalis. Thirty-eight women were found positive for T. vaginalis and out of these 22 (57.9%) were having symptomatic infection and 16 (42%) were asymptomatic. Fresh isolates from 15 symptomatic and 15 asymptomatic women were axenised and subjected to random amplified polymorphic DNA (RAPD) analysis with the use of five different random primers (OPD 1–OPD 5). The isolates with similar banding pattern were assigned as a single type. OPD 3 indicated least (nine types) while OPD 4 indicated highest typing (18 types) ability. Phylogenetic analysis using RAPD distance software indicated two distinct lineages; upper branch consisting of only seven symptomatic isolates while lower branch consisting of all the 15 asymptomatic isolates the other eight symptomatic isolates were recorded in separate cluster. The study indicated that RAPD technique might be helpful to delineate the pathogenic mechanism(s) for its virulence; however, further studies on large number of isolates are desired to elucidate the findings.

Genetic variability between Trichomonas vaginalis isolates and correlation with clinical presentation

The random amplified polymorphic DNA (RAPD) technique was used to determine genetic differences among isolates of Trichomonas vaginalis and these genetic data were correlated with patient records. A panel of 10 random primers was used to determine the type and extent of intraspecific polymorphism in 40 isolates of T. vaginalis. All primers detected DNA polymorphism among isolates. Numerical analysis of 124 RAPD amplified bands generated by these 10 primers were carried out with the unweighted pair group methods analysis (UPGMA) using Jaccard’s Similarity Coefficient and data were used to construct a dendrogram. Four main groups can be distinguished by RAPD data, these groups coincide with four different patient categories (asymptomatic and symptomatic: light, moderate, and severe infection). These patients did not have any concomitant vaginal infection. Each of the four groups can be characterized by specific genetic markers, but a specific 490 bp marker was found to be specific for all symptomatic isolates, not the asymptomatic isolates. This is the first description of a possible virulence marker for T. vaginalis. Further studies will be necessary to ascertain the importance and function of this genetic marker in clinical infection.

METHICILLIN RESISTANCE IN STAPHYLOCOCCAL ISOLATES FROM CLINICAL AND ASYMPTOMATIC BACTERIURIA SPECIMENS: IMPLICATIONS FOR INFECTION CONTROL

The study assessed the importance of Staphylococcus aureus as a urinary pathogen and the incidence of multidrug resistant (MDR), methicillin-resistant Staphylococcus aureus (MRSA). A total of 86 staphylococcal isolates made up of 50 clinical isolates from urine samples submitted to the Medical Microbiology Laboratory of Ahmadu Bello University Teaching Hospital and 36 asymptomatic bacteriuria isolates from urine samples of ‘healthy' volunteers within the university community were tested for their susceptibility to various antibiotics and production of b-lactamase enzyme. A total of 27 isolates (31.4%) were methicillin resistant, with 12(44.4%) being methicillin resistant coagulase-negative staphylococci (MRCNS). Majority of the isolates tested were resistant to the cheap, readily available broad-spectrum antibiotics; ampicillin, amoxicillin, chloramphenicol, tetracycline and penicillin G. All the isolates were resistant to three or more of the antimicrobial agents tested. A total of 14/50 (28%) of the clinical isolates and 17/36 (47.2%) of the ‘community' isolates from healthy volunteers were resistant to 7 or more of the antimicrobial agents tested. Analysis of the multiple antibiotic resistance (MAR) index of isolates and the production of b-lactamase enzyme showed that 56 isolates representing 65.1% of the total number tested had an MAR index of 0.5 and above indicating that they probably originated from an environment where antibiotics are frequently used. The implication of these findings for instituting effective control measures aimed at reducing the pool of antibiotic-resistant organisms is discussed. Key words: Methicillin-resistant, staphylococcus aureus, asymptomatic bacteriuria, infection control (Af J Clinical & Exp Microbiology: 2003 4(2): 79-90)

Specific IgA response, T-cell subtype and cytokine profile in experimental intravaginal trichomoniasis.

Trichomoniasis caused by Trichomonas vaginalis may lead to either a complete absence of symptoms or to severe inflammatory manifestations in infected women. Studies of the role of immune responses in the pathogenesis and varied symptomatology of this disease are lacking. Mice may prove useful as an experimental model for intravaginal trichomoniasis in developing an understanding of the role of local immune responses in the pathogenesis and varied symptomatology of this disease. The present study reports the levels of anti-Trichomonas IgA antibodies in serum and vaginal washes, and T-cell subtype and cytokine profile in vaginal cervical tissues of mice infected intravaginally with T. vaginalis isolates from 15 symptomatic and 15 asymptomatic women. It also correlates the responses with symptomatology of the patients. Successful intravaginal infection was established by inoculating T. vaginalis in BALB/c mice preinoculated with Lactobacillus acidophilus and pretreated with oestradiol. A significant increase in specific IgA antibody levels was detected with enzyme-linked immunosorbent assay in vaginal secretions and serum samples collected on the 7th post-infection day from animals infected with isolates from asymptomatic women when compared with mice infected with isolates from symptomatic women. T-cell subset analysis showed significant differences, with increased CD4+ T-cell count in animals infected with isolates from asymptomatic women compared with animals infected using isolates from symptomatic women. No difference in CD8+ T cells was observed between the two groups. Cytokine profile revealed significantly higher (P < 0.001) production of gamma-IFN and IL-2 in mice infected with asymptomatic isolates compared with animals infected with symptomatic isolates, using T. vaginalis crude antigen extract and nonspecific mitogen (ConA) as stimulants for vaginal cervical lymphocytes. However, no difference in IL-4 levels was observed in the two groups of animals. In contrast, significant increase in tumour necrosis factor (TNF-alpha) levels was observed in animals infected with asymptomatic isolates compared with those infected with isolates from symptomatic women and controls, thereby indicating that TNF-alpha may play an important role in the inflammatory response to trichomoniasis. The study further suggests that specific IgA antibodies might help to protect asymptomatic individuals from severe infection and T-lymphocytes may play an important function in the eradication of the parasite. The cytokine profile indicated the involvement of Th-1 like responses in mice infected with asymptomatic isolates, compared with those infected with symptomatic isolates.

Haemophilus somnus induces apoptosis in bovine endothelial cells in vitro.

Haemophilus somnus causes pneumonia, reproductive failure, infectious myocarditis, thrombotic meningoencephalitis, and other diseases in cattle. Although vasculitis is commonly seen as a result of systemic H. somnus infections, the pathogenesis of vascular damage is poorly characterized. In this study, we demonstrated that H. somnus (pathogenic isolates 649, 2336, and 8025 and asymptomatic carrier isolates 127P and 129Pt) induce apoptosis of bovine endothelial cells in a time- and dose-dependent manner, as determined by Hoechst 33342 staining, terminal deoxynucleotidyl transferase-mediated dUTP-FITC nick end labeling, DNA fragmentation, and transmission electron microscopy. H. somnus induced endothelial cell apoptosis in as little as 1 h of incubation and did not require extracellular growth of the bacteria. Viable H. somnus organisms induced greater endothelial cell apoptosis than heat-killed organisms. Since viable H. somnus cells release membrane fibrils and blebs, which contain lipooligosaccharide (LOS) and immunoglobulin binding proteins, we examined culture filtrates for their ability to induce endothelial cell apoptosis. Culture filtrates induced similar levels of endothelial cell apoptosis, as did viable H. somnus organisms. Heat inactivation of H. somnus culture filtrates partially reduced the apoptotic effect on endothelial cells, which suggested the presence of both heat-labile and heat-stable factors. We found that H. somnus LOS, which is heat stable, induced endothelial cell apoptosis in a time- and dose-dependent manner and was inhibited by the addition of polymyxin B. These data demonstrate that H. somnus and its LOS induce endothelial cell apoptosis, which may play a role in producing vasculitis in vivo.

Arbitrarily primed PCR fingerprinting of RNA and DNA in Entamoeba histolytica.

Differences were detected in the gene expression of strains of E. histolytica using RNA (RAP-PCR) and DNA fingerprinting (RAPD). Analysis of the electrophoretic profiles of the gels revealed some polymorphic markers that could be used in the individual characterization of the strains. The 260 bands generated by using five different primers for RAP-PCR, as well as RAPD, were employed in the construction of dendograms. The dendogram obtained based on the RAPD products permitted the distinction of symptomatic and asymptomatic isolates, as well the correlation between the polymorphism exhibited and the virulence of the strains. The dendogram obtained for the RAP-PCR products did not show a correlation with the virulence of the strains but revealed a high degree of intraspecific transcriptional variability that could be related to other biological features, whether or not these are involved in the pathogenesis of amebiasis.

Giardia lamblia: Effect of Infection with Symptomatic and Asymptomatic Isolates on the Growth of Gerbils (Meriones unguiculatus)

Astiazarán-García, H., Espinosa-Cantellano, M., Castañón, G., Chávez-Munguía, B., and Martínez-Palomo, A. 2000. Giardia lamblia: Effect of infection with symptomatic and asymptomatic isolates on the growth of gerbils (Meriones unguiculatus). Experimental Parasitology95, 128–135. Gerbils (Meriones unguiculatus) were intragastrically inoculated with axenic Giardia lamblia cultures from symptomatic and asymptomatic children. All isolates were able to colonize the duodenum. However, the colonization capacity of the symptomatic isolates was significantly higher compared to that of the asymptomatic ones. Despite the different colonization capacity of the isolates, the growth curves of infected animals were significantly lower than those of controls. The study demonstrates that acute giardia infections are capable of altering the corporal development of the host. These results may suggest that not only symptomatic, but also asymptomatic giardiasis in children, often unnoticed by parents and clinicians, could be causing a silent detriment in their nutritional status.