Endocardial Thickening in the Sprague-Dawley Rat

Thickening of the endocardium is sometimes observed in rats and other animals as a spontaneous or experimentally induced lesion. However, its nature, pathogenesis, and significance are not well understood.

In this study, 480 Sprague-Dawley CD outbred albino rats between the ages of 6 and 25 months were examined grossly and microscopically. Endocardial thickening was observed in six cases. It was diffuse and was caused by proliforation of fibroblast-like cells, most frequently involving the left ventricle.

Endocardial thickening in Sprague-Dawley rats appears to be primarily due to endomyocardial fibrosis. It may represent repair of damage to subendocardial myocardium occurring spontaneously or as a consequence of exposure to chemicals or other agents.

Exoplanet detection. A terrestrial planet in a ~1-AU orbit around one member of a ~15-AU binary

Using gravitational microlensing, we detected a cold terrestrial planet orbiting one member of a binary star system. The planet has low mass (twice Earth's) and lies projected at ~0.8 astronomical units (AU) from its host star, about the distance between Earth and the Sun. However, the planet's temperature is much lower, <60 Kelvin, because the host star is only 0.10 to 0.15 solar masses and therefore more than 400 times less luminous than the Sun. The host itself orbits a slightly more massive companion with projected separation of 10 to 15 AU. This detection is consistent with such systems being very common. Straightforward modification of current microlensing search strategies could increase sensitivity to planets in binary systems. With more detections, such binary-star planetary systems could constrain models of planet formation and evolution.

Air and surface contamination patterns of meticillin-resistant Staphylococcus aureus on eight acute hospital wards

BACKGROUND

Meticillin-resistant Staphylococcus aureus (MRSA) can be recovered from hospital air and from environmental surfaces. This poses a potential risk of transmission to patients.

AIM

To investigate associations between MRSA isolates recovered from air and environmental surfaces with those from patients when undertaking extensive patient and environmental sampling.

METHODS

This was a prospective observational study of patients and their environment in eight wards of a 700-bed tertiary care hospital during 2010 and 2011. Sampling of patients, air and surfaces was carried out on all ward bays, with more extended environmental sampling in ward high-dependency bays and at particular times of the day. The genetic relatedness of isolates was determined by DNA microarray profiling and spa typing.

FINDINGS

MRSA was recovered from 30/706 (4.3%) patients and from 19/132 (14.4%) air samples. On 9/132 (6.8%) occasions both patient and air samples yielded MRSA. In 32 high-dependency bays, MRSA was recovered from 12/161 (7.4%) patients, 8/32 (25%) air samples, and 21/644 (3.3%) environmental surface samples. On 10/132 (7.6%) occasions, MRSA was isolated from air in the absence of MRSA-positive patients. Patient demographic data combined with spa typing and DNA microarray profiling revealed four likely transmission clusters, where patient and environmental isolates were deemed to be very closely related.

CONCLUSION

Air sampling yielded MRSA on frequent occasions, especially in high-dependency bays. Environmental and air sampling combined with patient demographic data, spa typing and DNA microarray profiling indicated the presence of clusters that were not otherwise apparent.

A longitudinal of Parkinson's disease: clinical and neuropsychological correlates of dementia

Neuropsychological assessments were performed in ninety-one de novo patients participating in the Sydney Multicentre Study of Parkinson's disease. Assessments were made at baseline and after 3 and 5 years. Performance at baseline and after 5 years was compared with controls. At baseline 37% of patients whose symptoms of Parkinson's disease had begun after the age of 70 years were demented. This compared with a prevalence of dementia of 8.8% in patients whose symptoms had begun before the age of 70 years. By 5 years the prevalence of dementia in the two groups had risen to 62.3% and 17.3% respectively. The death rate was higher over the 5 year period in the demented patients. Demented patients had more symmetrical signs, higher disability and bradykinesia scores and more impairment of gait and balance at baseline than non-demented patients. The presence of dementia at baseline predicted a poor response to treatment. The dementia at baseline had features of a subcortical dementia. Subsequently, aphasia, apraxia and agnosia emerged, making the dementia indistinguishable from that of Alzheimer's disease. Patients with well preserved cognitive function at baseline had a good response to levodopa and were more likely to develop levodopa induced dyskinesia. These results show that the clinical features of Parkinson's disease and response to treatment are influenced by the age of onset of symptoms and by the presence of dementia.

Transmission of endemic ST22-MRSA-IV on four acute hospital wards investigated using a combination of spa, dru and pulsed-field gel electrophoresis typing

The transmission of meticillin-resistant Staphylococcus aureus (MRSA) between individual patients is difficult to track in institutions where MRSA is endemic. We investigated the transmission of MRSA where ST22-MRSA-IV is endemic on four wards using demographic data, patient and environmental screening, and molecular typing of isolates. A total of 939 patients were screened, 636 within 72 h of admission (on admission) and 303 >72 h after admission, and 1,252 environmental samples were obtained. Isolates were typed by spa, dru and pulsed-field gel electrophoresis (PFGE) typing. A composite dendrogram generated from the three sets of typing data was used to divide isolates into 'dendrogram groups' (DGs). Ten percent of patients (92/939) were MRSA-positive; 7 % (44/636) on admission and 16 % (48/303) >72 h after admission (p = 0.0007). MRSA was recovered from 5 % of environmental specimens (65/1,252). Most isolates from patients (97 %, 85/88) and the environment (97 %, 63/65) exhibited the ST22-MRSA-IV genotype. Four DGs (DG1, DG4, DG16 and DG17) accounted for 58 % of ST22-MRSA-IV isolates from patients. Epidemiological evidence suggested cross-transmission among 44/92 patients (48 %) but molecular typing confirmed probable cross-transmission in only 11 instances (13 %, 11/88), with the majority of cross-transmission (64 %; 7/11) occurring on one ward. In the setting of highly clonal endemic MRSA, the combination of local epidemiology, PFGE, spa and dru typing provided valuable insights into MRSA transmission.

Triclosan antagonizes fluconazole activity against Candida albicans

Triclosan is a broad-spectrum antimicrobial compound commonly used in oral hygiene products. Investigation of its activity against Candida albicans showed that triclosan was fungicidal at concentrations of 16 mg/L. However, at subinhibitory concentrations (0.5-2 mg/L), triclosan antagonized the activity of fluconazole. Although triclosan induced CDR1 expression in C. albicans, antagonism was still observed in cdr1Δ and cdr2Δ strains. Triclosan did not affect fluconazole uptake or alter total membrane sterol content, but did induce the expression of FAS1 and FAS2, indicating that its mode of action may involve inhibition of fatty acid synthesis, as it does in prokaryotes. However, FAS2 mutants did not exhibit increased susceptibility to triclosan, and overexpression of both FAS1 and FAS2 alleles did not alter triclosan susceptibility. Unexpectedly, the antagonistic effect was specific for C. albicans under hypha-inducing conditions and was absent in the non-filamentous efg1Δ strain. This antagonism may be due to the membranotropic activity of triclosan and the unique composition of hyphal membranes.

Lower filamentation rates of Candida dubliniensis contribute to its lower virulence in comparison with Candida albicans

Candida albicans and C. dubliniensis are very closely related yeast species. In this study, we have conducted a thorough comparison of the ability of the two species to produce hyphae and their virulence in two infection models. Under all induction conditions tested C. albicans consistently produced hyphae more efficiently than C. dubliniensis. In the oral reconstituted human epithelial model, C. dubliniensis isolates grew exclusively in the yeast form, while the C. albicans strains produced abundant hyphae that invaded and caused significant damage to the epithelial tissue. In the oral-intragastric infant mouse infection model, C. dubliniensis strains were more rapidly cleared from the gastrointestinal tract than C. albicans. Immunosuppression of Candida-infected mice caused dissemination to internal organs by both species, but C. albicans was found to be far more effective at dissemination than C. dubliniensis. These data suggest that a major reason for the comparatively low virulence of C. dubliniensis is its lower capacity to produce hyphae.

Bioavailable iron and heme metabolism in Plasmodium falciparum

Iron metabolism is essential for cell function and potentially toxic because iron can catalyze oxygen radical production. Malaria-attributable anemia and iron deficiency anemia coincide as being treatable diseases in the developing world. In absolute amounts, more than 95% of Plasmodium metal biochemistry occurs in the acidic digestive vacuole where heme released from hemoglobin catabolism forms heme crystals. The antimalarial quinolines interfere with crystallization. Despite the completion of the Plasmodium genome, many 'gene gaps' exist in components of the metal pathways described in mammalian or yeast cells. Present evidence suggests that parasite bioavailable iron originates from a labile erythrocyte cytosolic pool rather than from abundant heme iron. Indeed the parasite has to make its own heme within two separate organelles, the mitochondrion and the apicomplast. Paradoxically, despite the abundance of iron within the erythrocyte, iron chelators are cytocidal to the Plasmodium parasite. Hemozoin has become a sensitive biomarker for laser desorption mass spectrometry detection of Plasmodium infection in both mice and humans.

Azole susceptibility and resistance in Candida dubliniensis

Candida dubliniensis is a recently described species of pathogenic yeast that shares many phenotypic features with Candida albicans. It is primarily associated with oral colonization and infection in HIV-infected individuals. Isolates of C. dubliniensis are generally susceptible to commonly used azole antifungal agents; however, resistance has been observed in clinical isolates and can be induced by in vitro exposure. Molecular mechanisms of azole resistance in C. dubliniensis include increased drug efflux, modifications of the target enzyme and alterations in the ergosterol biosynthetic pathway.

Discovery of a cool planet of 5.5 Earth masses through gravitational microlensing

In the favoured core-accretion model of formation of planetary systems, solid planetesimals accumulate to build up planetary cores, which then accrete nebular gas if they are sufficiently massive. Around M-dwarf stars (the most common stars in our Galaxy), this model favours the formation of Earth-mass (M(o)) to Neptune-mass planets with orbital radii of 1 to 10 astronomical units (au), which is consistent with the small number of gas giant planets known to orbit M-dwarf host stars. More than 170 extrasolar planets have been discovered with a wide range of masses and orbital periods, but planets of Neptune's mass or less have not hitherto been detected at separations of more than 0.15 au from normal stars. Here we report the discovery of a 5.5(+5.5)(-2.7) M(o) planetary companion at a separation of 2.6+1.5-0.6 au from a 0.22+0.21-0.11 M(o) M-dwarf star, where M(o) refers to a solar mass. (We propose to name it OGLE-2005-BLG-390Lb, indicating a planetary mass companion to the lens star of the microlensing event.) The mass is lower than that of GJ876d (ref. 5), although the error bars overlap. Our detection suggests that such cool, sub-Neptune-mass planets may be more common than gas giant planets, as predicted by the core accretion theory.

Reproductive performance in anestrous dairy cows following treatment with two protocols and two doses of progesterone

The objectives of this study were to evaluate the effect using two doses of progesterone (P4) releasing devices in two different programs on reproductive performance of anestrous dairy cows. Cows (n = 1555) not detected in estrus by 10 d before the planned start of the seasonal breeding program and in which no CL was palpable were treated with an intravaginal P4-releasing device ('Single'; approximately 1.56 g of P4) or a modified device with triple the normal P4 dose ('Triple'; approximately 4.7 g of P4). The devices were in place for either 6 d ('Short') or 8 d ('Long'), with 1mg estradiol benzoate (EB) given 24 h after device removal. The 'Long' program also included treatment with 2 mg EB at device insertion. The Long program resulted in a higher first service conception rate (RR = 1.18 (95% CI = 1.03-1.33); P = 0.02), but had no effect on the 28-d, 56-d or final pregnancy rate compared to the Short program. There were no effects of dose of P4 on any outcome. In conclusion, the Long compared to the Short program, but not the dose of P4, improved first service conception rates in anestrous cows.

Search for Low-Mass Exoplanets by Gravitational Microlensing at High Magnification

Observations of the gravitational microlensing event MOA 2003-BLG-32/OGLE 2003-BLG-219 are presented, for which the peak magnification was over 500, the highest yet reported. Continuous observations around the peak enabled a sensitive search for planets orbiting the lens star. No planets were detected. Planets 1.3 times heavier than Earth were excluded from more than 50% of the projected annular region from approximately 2.3 to 3.6 astronomical units surrounding the lens star, Uranus-mass planets were excluded from 0.9 to 8.7 astronomical units, and planets 1.3 times heavier than Saturn were excluded from 0.2 to 60 astronomical units. These are the largest regions of sensitivity yet achieved in searches for extrasolar planets orbiting any star.

Management and outcome of bloodstream infections due to Candida species in England and Wales

This two-year prospective hospital population-based study of candidaemia is the first to be conducted in the UK. It was carried out on behalf on the British Society for Medical Mycology (BSMM) as part of the European Confederation of Medical Mycology (ECMM) epidemiological survey of candidaemia. Six hospitals in England and Wales acted as sentinel hospitals. Main outcome measures were hospital population-based incidence and 30-day mortality. There were 18.7 episodes of candidaemia per 100,000 finished consultant episodes or 3.0/100,000 bed days and 45.4% cases occurred in intensive care unit (ICU) patients. Candida albicans was isolated in 64.7% of confirmed cases. The majority of isolates were sensitive to standard antifungal agents, including fluconazole. The overall 30-day mortality was 26.4% and removal of the central venous catheter was associated with a significant reduction in mortality. In conclusion, the incidence of candidaemia in England and Wales is similar to that of the USA, the majority of isolates remain sensitive to commonly used antifungal agents and mortality associated with this infection appears to be falling.

Effective control of dental chair unit waterline biofilm and marked reduction of bacterial contamination of output water using two peroxide-based disinfectants

Bacterial biofilm in dental unit waterlines (DUWs) is a widespread problem, and poses a potentially significant risk of infection to dental staff and patients, particularly those who are medically compromised or immunocompromised. The purpose of the present study was to investigate the level of bacterial contamination of dental chair unit output water in the Dublin Dental Hospital, and to investigate the efficacy of two hydrogen peroxide-based disinfectants in reducing bacterial loads to < or =200 cfu/mL as recommended by the American Dental Association. The chemical quality of dental chair unit input and output water was well within the limits recommended for potable water. Water supplied to the units yielded an average aerobic heterotrophic bacterial cell density of 184 cfu/mL. However, the corresponding density in output water was considerably higher; the average cell density in water from the three-in-one air/water syringes and cup fillers in 12 chairs was 8200 and 4300 cfu/mL, respectively. Dental unit water obtained from 18 separate reservoir-supplied units in general practices in the Dublin area yielded an average of 66000 cfu/mL. The bacterial species found were predominantly environmental organisms, which were also present at low levels in the input water. Some of the species identified (e.g., Burkholderia cepacia and Pseudomonas fluorescens) are known opportunistic pathogens. The capacity of two disinfectants, Sterilex Ultra and Sanosil, to reduce bacterial contamination to safe levels was compared. In a controlled study, once weekly overnight (15 h) disinfection using either agent reduced the bacterial density to below the American Dental Association recommended level of 200 cfu/mL. However, once disinfection ceased the bacterial loads increased to unacceptably high levels within three weeks. Electron microscopic analysis showed that both disinfectants markedly reduced biofilm in the DUWs, but the biofilm rapidly became extensive again when once weekly disinfection ceased. While both disinfectants were equally effective in lowering the bacterial counts to acceptable levels, Sterilex Ultra was associated with clogging of DUWs in some dental chair units after repeated usage, suggesting that Sanosil is a more suitable agent for routine use.

Candida dubliniensis candidaemia in an HIV-positive patient in Ireland

Candida dubliniensis was first identified in Dublin in 1995 in oral isolates recovered from human immunodeficiency virus (HIV)-infected individuals. Although C. dubliniensis has been primarily recovered from the oral cavities of HIV-infected individuals, the number of reports describing its isolation from HIV-negative individuals, including cases of candidaemia, is growing. To date there has only been one report of C. dubliniensis candidaemia in an HIV-infected patient, in this case from the USA. In the present study, 2 Candida isolates recovered from blood samples were presumptively identified as C. dubliniensis on the basis of their dark green coloration on CHROMagar Candida medium and lack of growth at 45 degrees C. This identification was confirmed by carbohydrate assimilation profile analysis and by polymerase chain reaction (PCR) analysis with C. dubliniensis-specific PCR primers. Both isolates were susceptible to fluconazole. The isolates were found retrospectively to be from a single HIV-infected patient who was receiving broad-spectrum antibacterials at the time of isolation of C. dubliniensis from blood. This study represents the first documented case of C. dubliniensis bloodstream infection in Ireland and is only the second case of C. dubliniensis bloodstream infection identified in an HIV-infected individual anywhere in the world.

MDR1-mediated drug resistance in Candida dubliniensis

Candida dubliniensis is a recently described opportunistic fungal pathogen that is closely related to Candida albicans. Candida dubliniensis readily develops resistance to the azole antifungal agent fluconazole, both in vitro and in infected patients, and this resistance is usually associated with upregulation of the CdMDR1 gene, encoding a multidrug efflux pump of the major facilitator superfamily. To determine the role of CdMDR1 in drug resistance in C. dubliniensis, we constructed an mdr1 null mutant from the fluconazole-resistant clinical isolate CM2, which overexpressed the CdMDR1 gene. Sequential deletion of both CdMDR1 alleles was performed by the MPA(R)-flipping method, which is based on the repeated use of a dominant mycophenolic acid resistance marker for selection of integrative transformants and its subsequent deletion from the genome by FLP-mediated, site-specific recombination. In comparison with its parental strain, the mdr1 mutant showed decreased resistance to fluconazole but not to the related drug ketoconazole. In addition, we found that CdMDR1 confers resistance to the structurally unrelated drugs 4-nitroquinoline-N-oxide, cerulenin, and brefeldin A, since the enhanced resistance to these compounds of the parent strain CM2 compared with the matched susceptible isolate CM1 was abolished in the mdr1 mutant. In contrast, CdMDR1 inactivation did not cause increased susceptibility to amorolfine, terbinafine, fluphenazine, and benomyl, although overexpression of CdMDR1 in a hypersusceptible Saccharomyces cerevisiae strain had previously been shown to confer resistance to these compounds. The effect of CdMDR1 inactivation was identical to that seen in two similarly constructed C. albicans mdr1 mutants. Therefore, despite species-specific differences in the amino acid sequences of the Mdr1 proteins, overexpression of CaMDR1 and CdMDR1 in clinical C. albicans and C. dubliniensis strains seems to confer the same drug resistance profile in both species.

Multicenter prospective surveillance of oral Candida dubliniensis among adult Brazilian human immunodeficiency virus-positive and AIDS patients

The incidence of C. dubliniensis in South America has not yet been determined. In the present study, oral swab samples were taken from 108 HIV-infected/AIDS individuals attending 6 separate Brazilian HIV-treatment centers to determine the incidence of C. dubliniensis in this population. Swabs were plated onto CHROMagar Candida medium and 155 isolates, presumptively identified as C. albicans or C. dubliniensis were further investigated. In a preliminary screen for C. dubliniensis, 13 of the 155 isolates showed no or poor growth at 42 degrees C, and all them were subjected to randomly amplified polymorphic DNA (RAPD) and polymerase chain reaction (PCR) analysis using C. dubliniensis-specific primers. We confirmed that 4 out of 13 isolates were C. dubliniensis, representing an incidence rate of 2.8% for the Brazilian HIV-infected population infected with yeasts exhibiting green colonies on CHROMagar Candida. This value is significantly lower than those reported in Ireland and the United States.

Emerging pathogens

The ever increasing numbers of immunosuppressed individuals has led to a significant increase in the incidence of opportunistic infections, particularly those caused by fungi. The epidemiology of infections caused by the common fungal pathogens such as Candida albicans, Cryptococcus neoformans and Aspergillus fumigatus has been well documented. However, in addition to these, a number of species which have previously been unrecognized (e.g., C. dubliniensis) or have previously been assumed to be non-pathogenic (e.g., Saccharomyces cerevisiae, Scedosporium spp. and Fusarium spp.) have emerged as agents of human disease. Since these species have only been identified recently as human pathogens, their role in disease is poorly understood. In most cases, identification of these species is problematic and therefore their epidemiology has yet to be elucidated adequately. In addition, several of these species fail to respond to conventional antifungal therapies. In this article, we describe the emergence of two separate yeast species (C. dubliniensis and S. cerevisiae) and two separate groups of moulds (Scedosporium prolificans and Fusarium spp.), as human pathogens. It is apparent from what we already know, that much work has yet to be performed before we have a clear understanding of how these species cause disease and most importantly how they can be controlled.

Isogenic strain construction and gene targeting in Candida dubliniensis

Candida dubliniensis is a recently described opportunistic fungal pathogen that is closely related to Candida albicans but differs from it with respect to epidemiology, certain virulence characteristics, and the ability to develop fluconazole resistance in vitro. A comparison of C. albicans and C. dubliniensis at the molecular level should therefore provide clues about the mechanisms used by these two species to adapt to their human host. In contrast to C. albicans, no auxotrophic C. dubliniensis strains are available for genetic manipulations. Therefore, we constructed homozygous ura3 mutants from a C. dubliniensis wild-type isolate by targeted gene deletion. The two URA3 alleles were sequentially inactivated using the MPA(R)-flipping strategy, which is based on the selection of integrative transformants carrying a mycophenolic acid resistance marker that is subsequently deleted again by site-specific, FLP-mediated recombination. The URA3 gene from C. albicans (CaURA3) was then used as a selection marker for targeted integration of a fusion between the C. dubliniensis MDR1 (CdMDR1) promoter and a C. albicans-adapted GFP reporter gene. Uridine-prototrophic transformants were obtained with high frequency, and all transformants of two independent ura3-negative parent strains had correctly integrated the reporter gene fusion into the CdMDR1 locus, demonstrating that the CaURA3 gene can be used for efficient and specific targeting of recombinant DNA into the C. dubliniensis genome. Transformants carrying the reporter gene fusion did not exhibit detectable fluorescence during growth in yeast extract-peptone-dextrose medium in vitro, suggesting that CdMDR1 is not significantly expressed under these conditions. Fluconazole had no effect on MDR1 expression, but the addition of the drug benomyl strongly activated the reporter gene fusion in a dose-dependent fashion, demonstrating that the CdMDR1 gene, which encodes an efflux pump mediating resistance to toxic compounds, is induced by the presence of certain drugs.

Hemoglobin metabolism in the malaria parasite Plasmodium falciparum

Hemoglobin degradation in intraerythrocytic malaria parasites is a vast process that occurs in an acidic digestive vacuole. Proteases that participate in this catabolic pathway have been defined. Studies of protease biosynthesis have revealed unusual targeting and activation mechanisms. Oxygen radicals and heme are released during proteolysis and must be detoxified by dismutation and polymerization, respectively. The quinoline antimalarials appear to act by preventing sequestration of this toxic heme. Understanding the disposition of hemoglobin has allowed identification of essential processes and metabolic weakpoints that can be exploited to combat this scourge of mankind.

Haemoproteus and Schistosoma synthesize heme polymers similar to Plasmodium hemozoin and beta-hematin

Many parasites digest hemoglobin as an amino acid source, but only a few produce heme polymer pigment instead of catabolizing heme via heme oxygenase. This work compares purified heme polymers produced by Haemoproteus columbae and Schistosoma mansoni to that of Plasmodium falciparum hemozoin and synthetic beta-hematin. Fourier-transform infrared spectroscopy identifies the signature peaks of the common iron-carboxylate bond characteristic in all four heme polymers. However, all pigments could be distinguished by quite different three-dimensional structure visualized by Field Emission Inlens Scanning Electron Microscopy. Both P. falciparum and H. columbae heme polymers had a symmetrical shape unlike the amorphous S. mansoni heme polymer and beta-hematin. All four heme pigments serve as templates for heme polymer extension, which was inhibitable by chloroquine and other quinoline antimalarials. The polymers showed different levels of resistance to hydrogen peroxide degradation. This work identifies another genus, Haemoproteus, capable of intracellular heme polymer formation. The different three-dimensional structures of each pigment implicate genus specific formation of heme polymer, variation of inhibition of polymer extension by the quinolines and degradation by hydrogen peroxide.

Plasmodium falciparum: histidine-rich protein II is expressed during gametocyte development

Both early gametocytes (I-II) and asexual trophozoite stages of Plasmodium falciparum digest hemoglobin and detoxify haem by polymerizing it into parasite pigment called hemozoin. The mechanism of polymerization is unclear but it has been proposed that histidine-rich protein II may facilitate transport of hemoglobin to the food vacuole and catalyze the polymerization in asexual stages. We describe the transcription of histidine-rich protein II in gametocytes by Northern blot analysis and the expression of the protein in these stages by immunoprecipitation and Western blotting. Localization of histidine-rich protein II within the gametocyte by immunofluorescence assay and immunoelectron microscopy clearly illustrated the presence of this molecule in the infected red cell cytosol in the early stages of gametocyte development and internalization in the later gametocyte as it matures. There is a strong correlation between the stage-specific trafficking of histidine-rich protein II in gametocytes and the susceptibility of early but not late gametocytes to the antimalarial drug chloroquine.

Muscle force production and functional performance in spastic cerebral palsy: relationship of cocontraction

OBJECTIVE

To determine cocontraction's relation to strength and motor function in children with spastic cerebral palsy (CP).

DESIGN

Prospective evaluation with a convenience sample of 10 subjects.

SETTING

Pediatric rehabilitation center at a tertiary care hospital.

PATIENTS

Ten ambulatory children with spastic CP, mean age 5 to 14yrs.

MAIN OUTCOME MEASURES

A single comprehensive assessment of hamstring and quadriceps muscle strength; gait analysis while monitoring electromyographic (EMG) activity in those muscles; administration of the Gross Motor Function Measure (GMFM); heart-rate monitoring during quiet rest versus gait to compute an energy expenditure index (EEI). Cocontraction ratios and magnitudes were determined for the gait and strength testing trials using the EMG data.

RESULTS

Cocontraction ratios during strength tests correlated directly with those during free gait. Cocontraction magnitude and total EMG magnitude had an inverse relationship to EEI; children with more muscle activity in the agonist and antagonist tended to be more energy efficient. Knee extensor muscle strength correlated positively with the GMFM and gait velocity. Neither cocontraction ratio nor magnitude during gait was related to strength.

CONCLUSIONS

Children with CP used a similar muscle activation strategy across two different motor tasks. Strength and cocontraction were uniquely related to different aspects of motor function. Further research is needed to quantify more precisely cocontraction and force to EMG relations in this population.

Termination of life support after major trauma

As the population continues to age, greater numbers and more severely injured elderly patients require care in ICUs. With the attendant increase in the medical complexity of such patients, investigators anticipate that trauma and critical care resources will become increasingly stretched. Because of economic and societal forces, it will become increasingly important for trauma surgeons to appropriately counsel patients and their families regarding the outcome from their injuries and to become comfortable approaching families about withdrawal of support when medical futility is recognized. The authors propose the following guidelines for discussing limitation or termination of life support with patients and their families. Physicians should (1) discuss the patient's wishes regarding life support on admission or early in the hospital course; (2) at the initial discussion, establish who the decision maker will be if the patient is or becomes incapacitated; (3) maintain regular communication and continuity of care; and (4) inevitably, when conflict occurs, involve consultants and a hospital ethics committee for assistance in its resolution.

Isolation of C. dubliniensis from insulin-using diabetes mellitus patients

The identification of the novel candidal species, C. dubliniensis, from oral swab studies of HIV-seropositive and -seronegative individuals has led to speculation that such a species may also reside in the oral cavity of other patient groups. In this study involvement of the newly described species, C. dubliniensis, was investigated in oral carriage and disease in 414 insulin-using diabetes mellitus patients. Seventy-seven percent of the diabetic patients carried candidal species in the oral cavity. C. albicans was the most commonly identified candidal species. This was followed by C. dubliniensis, which was isolated on 64 occasions. Colonisation with multiple candidal species was common, and C. dubliniensis was present in both carriage and disease states. Seven patients without signs of oral disease had C. dubliniensis isolated as the sole candidal species, while the same species was associated with various forms of oral candidosis in six patients.

New monoclonal antibody specific for Candida albicans germ tube

Hydrophobic components of the germ tube of the dimorphic pathogenic fungus Candida albicans were used as immunogens to prepare monoclonal antibodies (MAbs). Among the resulting MAbs, one (MAb 16B1-F10) was shown by indirect immunofluorescence to be specific to the surface of the mycelium phase of the C. albicans and C. stellatoidea species. No labeling of any other genera and Candida species tested was observed, including C. dubliniensis, a newly described species which has many phenotypic similarities to C. albicans. This phase-specific epitope resides on a protein moiety. The molecular mass of the antigen released by Zymolyase digestion was determined by gel filtration and ranges from 25 to 166 kDa. The antigen was also shown to be highly hydrophobic. This anti-C. albicans cell wall surface-specific MAb may be a good candidate for use in tests for the rapid differentiation of the two closely related species C. albicans and C. dubliniensis.

Identification of Candida dubliniensis based on temperature and utilization of xylose and alpha-methyl-D-glucoside as determined with the API 20C AUX and vitek YBC systems

To have a better understanding of the role of Candida dubliniensis in clinical infections, it is essential that microbiology laboratories can identify this species rapidly and accurately in clinical specimens. C. dubliniensis has been reported to lack the ability to utilize xylose (XYL) and alpha-methyl-D-glucoside (MDG) and to grow poorly or not at all at 45 degrees C, whereas Candida albicans isolates utilize XYL and MDG and usually grow well at 45 degrees C. We tested 66 isolates of C. dubliniensis and 100 isolates of C. albicans with both the API 20C AUX and Vitek YBC systems to evaluate the ability of the XYL and MDG tests contained within each of these systems to distinguish between the two species. The ability to grow at 45 degrees C was also examined. None of the C. dubliniensis isolates grew at 45 degrees C, and 23 of 100 C. albicans isolates (23%) exhibited poor or no growth at 45 degrees C. The XYL and MDG tests contained within the API 20C AUX system were both negative for all 66 C. dubliniensis isolates and were positive for 98 (XYL) and 56 (MDG) of the 100 C. albicans isolates. With the Vitek system, 64 of 66 C. dubliniensis isolates (97.0%) were XYL negative and 63 (95.0%) were MDG negative. Conversely, 96 of 100 C. albicans isolates (96.0%) were XYL positive and 100 (100.0%) were MDG positive with the Vitek system. Clinical microbiology laboratories could use lack of growth at 45 degrees C and a negative XYL test with either the API 20C AUX or Vitek yeast identification system to provide a presumptive identification of C. dubliniensis. A negative MDG test result with either system would also be helpful but may misclassify C. albicans as C. dubliniensis, especially when the API 20C AUX system is used.

Rapid identification of Candida dubliniensis with commercial yeast identification systems

Candida dubliniensis is a newly described species that is closely related phylogenetically to Candida albicans and that is commonly associated with oral candidiasis in human immunodeficiency virus-positive patients. Several recent studies have attempted to elucidate phenotypic and genotypic characteristics of use in separating the two species. However, results obtained with simple phenotypic tests were too variable and tests that provided more definitive data were too complex for routine use in the clinical laboratory setting. The objective of this study was to determine if reproducible identification of C. dubliniensis could be obtained with commercial identification kits. The substrate reactivity profiles of 80 C. dubliniensis isolates were obtained by using the API 20C AUX, ID 32 C, RapID Yeast Plus, VITEK YBC, and VITEK 2 ID-YST systems. The percentages of C. dubliniensis isolates capable of assimilating or hydrolyzing each substrate were compared with the percentages from the C. albicans profiles in each kit's database, and the results were expressed as percent C. dubliniensis and percent C. albicans. Any substrate that showed >50% difference in reactivity was considered useful in differentiating the species. In addition, assimilation of methyl-alpha-D-glucoside (MDG), D-trehalose (TRE), and D-xylose (XYL) by the same isolates was investigated by the traditional procedure of Wickerham and Burton (L. J. Wickerham and K. A. Burton, J. Bacteriol. 56:363-371, 1948). At 48 h (the time recommended by the manufacturer for its new database), we found that the assimilation of four carbohydrates in the API 20C AUX system could be used to distinguish the species, i.e., glycerol (GLY; 88 and 14%), XYL (0 and 88%), MDG (0 and 85%), and TRE (15 and 97%). Similarly, results with the ID 32 C system at 48 h showed that XYL (0 and 98%), MDG (0 and 98%), lactate (LAT; 0 and 96%), and TRE (30 and 96%) could be used to separate the two species. Phosphatase (PHS; 9 and 76%) and alpha-D-glucosidase (23 and 94%) proved to be the most useful for separation of the species in the RapID Yeast Plus system. While at 24 h the profiles obtained with the VITEK YBC system showed that MDG (10 and 95%), XYL (0 and 95%), and GLY (26 and 80%) could be used to separate the two species, at 48 h only XYL (6 and 95%) could be used to separate the two species. The most useful substrates in the VITEK 2 ID-YST system were TRE (1 and 89%), MDG (1 and 99%), LAT (4 and 98%), and PHS (83 and 1%). While the latter kit was not yet commercially available at the time of the study, it would appear to be the most valuable for the identification of C. dubliniensis. Although assimilation of MDG, TRE, and XYL proved to be the most useful for species differentiation by the majority of commercial systems, the results with these carbohydrates by the Wickerham and Burton procedure were essentially the same for both species, albeit following protracted incubation. Thus, it is the rapidity of the assimilation achieved with the commercial systems that allows the differentiation of C. dubliniensis from C. albicans.

Rapid PCR test for discriminating between Candida albicans and Candida dubliniensis isolates using primers derived from the pH-regulated PHR1 and PHR2 genes of C. albicans

The development of a satisfactory means to reliably distinguish between the two closely related species Candida albicans and Candida dubliniensis in the clinical mycology laboratory has proved difficult because these two species are phenotypically so similar. In this study, we have detected homologues of the pH-regulated C. albicans PHR1 and PHR2 genes in C. dubliniensis. Restriction fragment length polymorphism analysis suggests that there are significant sequence differences between the genes of the two species. In order to exploit this apparent difference, oligonucleotide primers based on the coding sequence of the C. albicans PHR1 structural gene were designed and used in PCR experiments. Use of these primers with C. albicans template DNA from 17 strains yielded a predicted 1.6-kb product, while C. dubliniensis template DNA from 19 strains yielded no product. We therefore propose that PCR using these primers is a rapid and reliable means of distinguishing the two germ tube- and chlamydospore-producing species C. albicans and C. dubliniensis.

In vitro susceptibilities of Candida dubliniensis isolates tested against the new triazole and echinocandin antifungal agents

Candida dubliniensis is a newly recognized fungal pathogen causing mucosal disease in AIDS patients. Although preliminary studies indicate that most strains of C. dubliniensis are susceptible to established antifungal agents, fluconazole-resistant strains have been detected. Furthermore, fluconazole-resistant strains are easily derived in vitro, and these strains exhibit increased expression of multidrug resistance transporters, especially MDR1. Because of the potential for the development of resistant strains of C. dubliniensis, it is prudent to explore the in vitro activities of several of the newer triazole and echinocandin antifungals against isolates of C. dubliniensis. In this study we tested 71 isolates of C. dubliniensis against the triazoles BMS-207147, Sch 56592, and voriconazole and a representative of the echinocandin class of antifungal agents, MK-0991. We compared the activities of these agents with those of the established antifungal agents fluconazole, itraconazole, amphotericin B, and 5-fluorocytosine (5FC) by using National Committee for Clinical Laboratory Standards microdilution reference methods. Our findings indicate that the vast majority of clinical isolates of C. dubliniensis are highly susceptible to both new and established antifungal agents. Strains with decreased susceptibilities to fluconazole remained susceptible to the investigational agents as well as to amphotericin B and 5FC. The increased potencies of the new triazole and echinocandin antifungal agents may provide effective therapeutic options for the treatment of infections due to C. dubliniensis.

Importance of Candida species other than Candida albicans as opportunistic pathogens

Candida species other than C. albicans have become a significant cause of infection in humans. Several of the more commonly isolated of these species are less susceptible to commonly used azole antifungal drugs, a factor that poses significant difficulties for effective treatment. The modern mycology laboratory has an important role to play in several aspects relating to these organisms, including therapy, detection, identification and epidemiological analysis. The application of molecular techniques and phylogenetic analysis has led to the identification of a new species of Candida associated with mucosal candidiasis in HIV-infected individuals named Candida dubliniensis, the clinical significance of which is currently under investigation. Molecular techniques are also being applied to the analysis of determinants involved in pathogenicity of species such as Candida glabratta. These approaches should lead to a better understanding of these organisms and there ability to cause disease and should also provide more effective treatment.

Hyperparasitism: multitrophic ecology and behavior

Hyperparasitoids are secondary insect parasitoids that develop at the expense of a primary parasitoid, thereby representing a highly evolved fourth trophic level. This review evaluates multitrophic relationships and hyperparasitoid ecology. First, hyperparasitoid communities of various taxa of phytophagous and predacious insects are described. Second, specific patterns of hyperparasitoid community organization and hyperparasitoid ecology are described in detail, using the aphid-parasitoid-hyperparasitoid food web as a model system. Aphid hyperparasitoid communities consist of ecto- and endohyperparasitoids, with ectohyperparasitoids being less host specific than endohyperparasitoids. Lifetime fecundity and intrinsic rate of increase of hyperparasitoids are generally lower than those of their primary hosts. Aphid ectohyperparasitoids search randomly for hosts and do not use specific cues, whereas endohyperparasitoids gain information that originates from host plants or hosts for long-range search. Interactions with adult primary parasitoids do not influence hyperparasitoid searches, but aphid-attending ants typically prevent successful hyperparasitoid foraging. Impact of hyperparasitism on biological control is reviewed.

A common mechanism for blockade of heme polymerization by antimalarial quinolines

The antimalarial quinolines are believed to work by blocking the polymerization of toxic heme released during hemoglobin proteolysis in intraerythrocytic Plasmodium falciparum. In the presence of free heme, chloroquine and quinidine associate with the heme polymer. We have proposed that this association of the quinoline-heme complex with polymer caps the growing heme polymer, preventing further sequestration of additional heme that then accumulates to levels that kill the parasite. In this work results of binding assays demonstrate that the association of quinoline-heme complex with heme polymer is specific, saturable, and high affinity and that diverse quinoline analogs can compete for binding. The relative quinoline binding affinity for heme polymer rather than free heme correlates with disruption of heme polymerization. Mefloquine, another important antimalarial quinoline, associated with polymer in a similar fashion, both in cultured parasites and in the test tube. In parasite culture, blocking heme release with protease inhibitor was antagonistic to mefloquine action, as it is to chloroquine action. These data suggest a common mechanism for quinoline antimalarial action dependent on drug interaction with both heme and heme polymer.

Rapid identification of Candida dubliniensis by indirect immunofluorescence based on differential localization of antigens on C. dubliniensis blastospores and Candida albicans germ tubes

There is a clear need for the development of a rapid and reliable test for the identification of Candida dubliniensis and for the discrimination of this species from Candida albicans. In the present study we have investigated the potential use of C. dubliniensis-specific antigens as a basis for its identification. We produced an anti-C. dubliniensis serum which, after adsorption with C. albicans blastospores, was found to differentially label C. dubliniensis isolates in an indirect immunofluorescence test. In this test, the antiserum reacted with blastospores and germ tubes of C. dubliniensis and with blastospores of Candida krusei and Rhodotorula rubra but did not react with blastospores of several other Candida species including C. albicans. The antiserum also reacted with C. albicans germ tubes. The anti-C. dubliniensis adsorbed serum reacted with specific components of 25, 28, 37, 40, 52, and 62 kDa in the C. dubliniensis extract and with a variety of antigens from other yeast species. The antigens from non-C. dubliniensis yeasts showing reactivity with the anti-C. dubliniensis adsorbed serum are mostly expressed within the cell walls of these yeast species, and this reactivity does not interfere with the use of the anti-C. dubliniensis adsorbed serum in an indirect immunofluorescence test for the rapid identification of C. dubliniensis.

Identification and expression of multidrug transporters responsible for fluconazole resistance in Candida dubliniensis

Candida dubliniensis is a recently described Candida species associated with oral candidosis in human immunodeficiency virus (HIV)-infected and AIDS patients, from whom fluconazole-resistant clinical isolates have been previously recovered. Furthermore, derivatives exhibiting a stable fluconazole-resistant phenotype have been readily generated in vitro from fluconazole-susceptible isolates following exposure to the drug. In this study, fluconazole-resistant isolates accumulated up to 80% less [3H] fluconazole than susceptible isolates and also exhibited reduced susceptibility to the metabolic inhibitors 4-nitroquinoline-N-oxide and methotrexate. These findings suggested that C. dubliniensis may encode multidrug transporters similar to those encoded by the C. albicans MDR1, CDR1, and CDR2 genes (CaMDR1, CaCDR1, and CaCDR2, respectively). A C. dubliniensis homolog of CaMDR1, termed CdMDR1, was cloned; its nucleotide sequence was found to be 92% identical to the corresponding CaMDR1 sequence, while the predicted CdMDR1 protein was found to be 96% identical to the corresponding CaMDR1 protein. By PCR, C. dubliniensis was also found to encode homologs of CDR1 and CDR2, termed CdCDR1 and CdCDR2, respectively. Expression of CdMDR1 in a fluconazole-susceptible delta pdr5 null mutant of Saccharomyces cerevisiae conferred a fluconazole-resistant phenotype and resulted in a 75% decrease in accumulation of [3H]fluconazole. Northern analysis of fluconazole-susceptible and -resistant isolates of C. dubliniensis revealed that fluconazole resistance was associated with increased expression of CdMDR1 mRNA. In contrast, most studies showed that overexpression of CaCDR1 was associated with fluconazole resistance in C. albicans. Increased levels of the CdMdr1p protein were also detected in fluconazole-resistant isolates. Similar results were obtained with fluconazole-resistant derivatives of C. dubliniensis generated in vitro, some of which also exhibited increased levels of CdCDR1 mRNA and CdCdr1p protein. These results demonstrate that C. dubliniensis encodes multidrug transporters which mediate fluconazole resistance in clinical isolates and which can be rapidly mobilized, at least in vitro, on exposure to fluconazole.

Identification and characterization of an unusual double serine/threonine protein phosphatase 2C in the malaria parasite Plasmodium falciparum

We have cloned a gene from Plasmodium falciparum with homology to the Mg2+-dependent serine/threonine protein phosphatase 2C (PP2C) family. The predicted coding region is 920 amino acids long, twice the size of other members of this family. We show that this protein can be divided into two halves (Pf2C-1 and Pf2C-2), each a complete phosphatase unit with homology to other phosphatases of this class. To study the function of this PP2C, we have tested the ability of different constructs to complement conditional null mutants of yeast. Our results show that expression of the full-length protein, the first half alone, the second half alone, or a hybrid with the N terminus of the first half and the C terminus of the second half was able to complement the heat shock response defect of a Schizosaccharomyces pombe strain with a PP2C (PTC1) deletion. Recombinant P. falciparum PP2C expressed in Escherichia coli was active in dephosphorylating 32P-labeled casein in an Mg2+- or Mn2+-dependent reaction. Each half alone was also active in recombinant form. Using the two-hybrid system, we have shown that the two halves can interact. Gel filtration assay of P. falciparum protein extracts suggests that full-length PfPP2C is a dimer, and phosphatase activity competition experiments indicate that dimerization of PfPP2C is required for its optimal activity. This unusual phosphatase molecule appears to be composed of four catalytic units on two polypeptide chains.

Long-term cytokine alterations following allogeneic blood transfusion

BACKGROUND

Allogeneic blood transfusion is associated with an increased risk of infection and higher cancer recurrence rates. Previous research has shown that blood transfusion results in multiple immune effects, including cytokine alterations. The purpose of this study was to measure the long term kinetics of splenocyte cytokine production in transfused mice.

METHODS

Balb/c mice received either syngeneic transfusion (Syn-BT) or allogeneic transfusion (Allo-BT) from C3H-HeN mice. Splenocyte production of IL-2, IL-6, IL-10, and IFN-gamma was quantitated by ELISA on post-transfusion days 5, 10, 21, and 30.

RESULTS

Both Allo-BT and Syn-BT produced significant alterations in cytokine production, but Allo-BT produced the most dramatic and enduring effects as summarized: IL-2: Production of IL-2 was suppressed at day 5, (p < 0.0001), but then rose, peaking at day 21, 30% greater than control values (p < 0.05). IL-6: Allo-BT mice showed suppression of IL-6 throughout the study period (p < 0.005 vs controls, each time point). IL-10: A 5-fold increase in IL-10 production was seen at day 5 after Allo-BT (p < 0.0001 vs control). Production of IL-10 was suppressed at days 10 and 21 (p < 0.001), but returned to control levels by day 30, gamma-IFN: At day 5 post Allo-BT, gamma-IFN was 4 x greater than controls (p < 0.0001). Gamma-IFN production was suppressed at day 10, but then rose at days 21 and 30 to nearly 3 x control levels (p < 0.0001).

CONCLUSION

Allo-BT produced multiple cytokine alterations that were of prolonged duration. These results provide a theoretic explanation for the multiple, long-term immunomodulating effects seen in patients who have received transfusions.

Distinct effects of allogeneic blood transfusion on splenocyte cytokine production after hemorrhagic shock

Allogeneic blood transfusion is known to be immunosuppressive in the settings of cancer and transplantation, but the contribution of blood transfusion to immunomodulation after hemorrhage is unknown. Our purpose was to determine the influence of allogeneic blood transfusion upon cytokine profiles following hemorrhagic shock, using a model which approximates the clinical setting.

METHODS

Male C3H/HeN mice were hemorrhaged via femoral arterial catheters to a mean arterial pressure (MAP) of 35 +/- 5 mm Hg, which was maintained for 1 h. Mice were resuscitated with autologous blood (auto BT) or allogeneic blood (allo BT) from Balb/c mice (both equivalent to volume of shed blood), and crystalloid (2X the volume of shed blood)-infused at 0.05 ml/min. Animals were sacrificed at 1, 2, and 5 days postshock, and splenocytes were cultured for 24 h with anti-CD3 antibody. Supernatants were assayed for IL-2, IL-6, IL-10, and gamma-IFN by ELISA.

RESULTS

Regardless of transfusion status, hemorrhagic shock resulted in increased IL-6 and gamma-IFN by Day 2 postshock. Distinct cytokine alterations after allogeneic transfusion were as follows. IL-2: transient elevation of splenocyte IL-2 production in the shock + allo BT group (P < 0.005 vs. shock + auto BT) at Postshock Day 2. IL-6: suppression in IL-6 production in the shock + allo BT group by Postshock Day 5 (P < 0.05 vs. shock + auto BT). IL-10: persistently elevated IL-10 production following shock + allo BT (Day 1, P < 0.001 vs. shock + auto BT; Day 5; P < 0.05 vs. shock + auto BT). gamma-IFN: elevation in gamma-IFN production by Day 5 in the shock + allo BT group (P < 0.0005 vs. shock + auto BT).

CONCLUSIONS

Allogeneic blood transfusion results in distinct alterations in splenocyte production of IL-2, IL-6, IL-10, and gamma-IFN after hemorrhagic shock. This model reflects the clinical usage of blood products and demonstrates some of the immune alterations after transfusion.

Antifungal drug susceptibilities of oral Candida dubliniensis isolates from human immunodeficiency virus (HIV)-infected and non-HIV-infected subjects and generation of stable fluconazole-resistant derivatives in vitro

Candida dubliniensis is a recently described species of Candida associated with oral candidiasis in human immunodeficiency virus (HIV)-infected individuals. Nineteen oral isolates of C. dubliniensis recovered from 10 HIV-positive and 4 HIV-negative individuals and one vaginal isolate from an additional HIV-negative subject were assessed for fluconazole susceptibility by broth microdilution (BMD), hyphal elongation assessment, and Etest. The susceptibilities of these 20 isolates to itraconazole and amphotericin B and of 10 isolates to ketoconazole were also determined by BMD only. Sixteen of the C. dubliniensis isolates were susceptible to fluconazole (MIC range, 0.125 to 1.0 microgram ml-1), and four (recovered from two AIDS patients) were fluconazole resistant (MIC range, 8 to 32 micrograms ml-1). Fluconazole susceptibility data obtained by hyphal elongation assessment correlated well with results obtained by BMD, but the corresponding Etest MIC results were one to four times higher. All of the isolates tested were found to be sensitive to itraconazole, ketoconazole, and amphotericin B. Sequential exposure of two fluconazole-sensitive (MIC, 0.5 microgram ml-1) C. dubliniensis isolates to increasing concentrations of fluconazole in agar medium resulted in the recovery of derivatives which expressed a stable fluconazole-resistant phenotype (BMD-determined MIC range, 16 to 64 micrograms ml-1), even after a minimum of 10 consecutive subcultures on drug-free medium and following prolonged storage at -70 degrees C. The clonal relationship between the parental isolates and their respective fluconazole-resistant derivatives was confirmed by genomic DNA fingerprinting and karyotype analysis. The results of this study demonstrate that C. dubliniensis is inherently susceptible to commonly used antifungal drugs, that fluconazole resistance does occur in clinical isolates, and that stable fluconazole resistance can be readily induced in vitro following exposure to the drug.

Genomic DNA fingerprinting of clinical isolates of Helicobacter pylori using short oligonucleotide probes containing repetitive sequences

The ability of oligonucleotide probes containing short repetitive sequence motifs to differentiate between isolates of Helicobacter pylori was investigated. Genomic DNA preparations from H. pylori were digested with the restriction enzyme HindIII, electrophoresed in agarose gels and transferred to nylon filters. Five separate oligonucleotide probes were tested for hybridization sequentially to fingerprint the digested DNA from a panel of 29 clinical isolates and one type strain of H. pylori, and their relative discriminatory abilities were assessed. Four probes, (GACA)4, (GT)8, (GTG)5 and (GGAT)4, were each shown to yield highly informative hybridization band profiles allowing differentiation of H. pylori isolates. The DNA fingerprints of individual isolates obtained with each probe were distinct and reproducible. Direct comparison with ribotyping revealed that oligonucleotide fingerprinting had far superior discriminatory power. Computer-assisted similarity analysis of (GGAT)4-generated hybridization profiles of pairwise combinations of H. pylori isolates revealed that there was no correlation between ribotype and oligonucleotide fingerprint patterns. The results of this study demonstrate that oligonucleotide probes containing microsatellite sequences provide a new and powerful tool for isolate discrimination of H. pylori.