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PubMed2006

CD44 differentially activates mouse NK T cells and conventional T cells.

NK T (NKT) cells are an important component of the innate immune system and recognize the MHC class I-like CD1d molecule. NKT cells possess significant immunoregulatory activity due to their rapid secretion of large quantities of pro- and anti-inflammatory cytokines following CD1d-dependent stimulation. Because the innate immune system is programmed to respond to a multitude of diverse stimuli and must be able to quickly differentiate between pathogenic and endogenous signals, we hypothesized that, apart from stimulation via the TCR (e.g., CD1d-dependent activation), there must be multiple activation pathways that can be triggered through other cell surface receptors on NKT cells. Therefore, we analyzed the ability of CD44, a structurally diverse cell surface receptor expressed on most cells, to stimulate murine NKT cells, compared with conventional T cells. Stimulation of CD44 through Ab cross-linking or binding to its natural ligands hyaluronan and osteopontin induced NKT cells to secrete cytokines, up-regulate activation markers, undergo morphological changes, and resist activation-induced cell death, whereas conventional T cells only exhibited changes in morphology and protection from activation-induced cell death. This CD44-specific stimulation of NKT cells correlated with their ability to bind hyaluronan. Thus, fundamental differences in CD44 function between these lymphocyte subsets suggest an important biological role for CD44 in the innate immune response.

Animals↗

PubMed2026

Dental wastewater reveals a hidden reservoir of oral bacteriophage diversity.

Bacteriophages (phages) are being explored as alternatives or complements to antibiotics because of their ability to selectively kill bacterial pathogens. However, phages that infect many oral bacteria remain undiscovered. Here, we discovered that dental wastewater harbors previously underexplored phage diversity. Viral particles concentrated from dental wastewater displayed diverse morphologies, including abundant filamentous phage-like particles. Deep long-read metagenomic sequencing of concentrated viral particles generated 7.4 billion bases of sequence data and yielded 255 medium- to high-quality viral operational taxonomic units (vOTUs), including 46 predicted complete genomes. Comparison with large phage databases revealed that 63 of these 255 vOTUs had no detectable match, indicating that extensive sequencing of dental wastewater substantially expands the number of potential bacteriophages associated with the human oral microbiome. Host prediction linked many vOTUs to oral-associated bacterial taxa, including species with few or no previously reported phages, such as Porphyromonas gingivalis, Tannerella forsythia, and Candidatus Saccharibacteria. Functional annotation identified diverse genes associated with antiphage defense systems within a subset of vOTUs, suggesting that oral phages may contribute to the movement of genes encoding bacterial immune functions within the oral microbiome. Together, these findings expand the known oral phageome and show that dental wastewater contains a largely untapped diversity of phages.IMPORTANCEThe human oral cavity contains a diverse microbial community, but the bacteriophages (phages) that infect many oral bacteria remain poorly characterized. This gap limits our understanding of how phages shape oral microbial communities. Here, we show that dental wastewater is an underexplored source of oral phage diversity. Deep long-read metagenomic sequencing revealed 255 medium- to high-quality phage operational taxonomic units, many of which are not present in existing oral phage databases. These genomes include predicted phages of periodontal disease-associated bacteria and other oral taxa with few or no known phages. Dental wastewater therefore expands the known human oral phageome and reveals candidate phages linked to bacteria associated with oral health and disease.

Bacteriophages↗

PubMed2006

Quorum sensing and the lifestyle of Yersinia.

Bacterial cell-to-cell communication ('quorum sensing') is mediated by structurally diverse, small diffusible signal molecules which regulate gene expression as a function of cell population density. Many different Gram-negative animal, plant and fish pathogens employ N-acylhomoserine lactones (AHLs) as quorum sensing signal molecules which control diverse physiological processes including bioluminescence, swarming, antibiotic biosynthesis, plasmid conjugal transfer, biofilm development and virulence. AHL-dependent quorum sensing is highly conserved in both pathogenic and non-pathogenic members of the genus Yersinia. Yersinia pseudotuberculosis for example, produces at least eight different AHLs and possesses two homologues of the LuxI family of AHL synthases and two members of the LuxR family of AHL-dependent response regulators. In all Yersinia species so far examined, the genes coding for LuxR and LuxI homologues are characteristically arranged convergently and overlapping. In Y. pseudotuberculosis AHL-dependent quorum sensing is involved in the control of cell aggregation and swimming motility, the latter via the flagellar regulatory cascade. This is also the case for swimming and also swarming motility in Yersinia enterocolitica. Howeverthe role of AHL-dependent quorum sensing in Yersinia pestis remains to be determined.

4-Butyrolactone↗

PubMed2004

Non-encapsulated strains reveal novel insights in invasion and survival of Streptococcus suis in epithelial cells.

Streptococcus suis is a porcine and human pathogen causing invasive diseases, such as meningitis or septicaemia. Host cell interactions of S. suis have been studied mainly with serotype 2 strains, but multiple capsular serotypes as well as non-typeable strains exist with diverse virulence features. At present, S. suis is considered an extracellular pathogen. However, whether or not it can also invade host cells is a matter of controversial discussions. We have assessed adherence and invasion of S. suis for HEp-2 epithelial cells by comparing 10 serotype 2 strains and four non-typeable (NT) strains. Only the NT strains and a non-encapsulated serotype 2 mutant strain, but none of the serotype 2 strains, adhered strongly and were invasive. Invasion seemed to be affected by environmental signals, as suggested from comparison of strains grown in different media. Further phenotypic and genotypic characterization revealed a high diversity among the different strains. Electron microscopic analysis of invasion of selected invasive NT strains indicated different uptake mechanisms. One strain induced large invaginations comparable to those seen in 'caveolae' mediated uptake, whereas invasion of the other strains was accompanied by formation of filipodia-like membrane protrusions. Invasion of all strains, however, was similarly susceptible to hypertonic sucrose, which inhibits receptor-mediated endocytosis. Irrespective of the uptake pathway, streptococci resided in acidified phago-lysosome like vacuoles. All strains, except one, survived intracellularly as well as extracellular acidic conditions. Survival seemed to be associated with the AdiS protein, an environmentally regulated arginine deiminase of S. suis. Concluding, invasion and survival of NT strains of S. suis in epithelial cells revealed novel evidence that S. suis exhibits a broad variety of virulence-associated features depending on genetic variation and regulation.

Acids↗

PubMed2006

The application of high-throughput AFLP's in assessing genetic diversity in Fusarium oxysporum f. sp. cubense.

Fusarium oxysporum f. sp. cubense (Foc) is responsible for fusarium wilt of bananas. The pathogen consists of several variants that are divided into three races and 21 vegetative compatibility groups (VCGs). Several DNA-based techniques have previously been used to analyse the worldwide population of Foc, sometimes yielding results that were not always consistent. In this study, the high-resolution genotyping method of AFLP is introduced as a potentially effective molecular tool to investigate diversity in Foc at a genome-wide level. The population selected for this study included Foc isolates representing different VCGs and races, isolates of F. oxysporum f. sp. dianthi, a putatively non-pathogenic biological control strain F. oxysporum (Fo47), and F. circinatum. High-throughput AFLP analysis was attained using five different infrared dye-labelled primer combinations using a two-dye model 4200s LI-COR automated DNA analyser. An average of approx. 100 polymorphic loci were scored for each primer pair using the SAGA(MX) automated AFLP analysis software. Data generated from five primer pair combinations were combined and subjected to distance analysis, which included the use of neighbour-joining and a bootstrap of 1000 replicates. A tree inferred from AFLP distance analysis revealed the polyphyletic nature of the Foc isolates, and seven genotypic groups could be identified. The results indicate that AFLP is a powerful tool to perform detailed analysis of genetic diversity in the banana pathogen Foc.

DNA Fingerprinting↗

PubMed1998

Microbial contamination of advanced life support (ALS) systems poses a moderate threat to the long-term stability of space-based bioregenerative systems.

Microbial contamination of terrestrial hydroponic plant-growing systems provides an effective analogue for studying microbial contamination issues for space-based advanced life support (ALS) systems. If aggressive root or foliar pathogens are introduced into ALS hydroponic systems, severe epidemics are probable. Greater than 80% of the reported outbreaks of root pathogens in terrestrial hydroponic systems describe epidemics caused by fungal species of Fusarium, Phytophthora, and Pythium. However, it is likely that a comprehensive sanitation and quarantine program for space-based ALS modules will prevent contamination by Phytophthora and Pythium spp. because these pathogens are general soilborne. However, Fusarium spp. are typically airborne, can grow saprophytically on diverse substrates, and have been common contaminants of American spacecraft. If comprehensive sanitation and quarantine programs are established for space-based ALS modules, then the threat of pathogen introductions into these systems will be significantly mitigated. Microbial contamination studies in spacecraft over the last 30 years indicate that a high diversity of bacteria, fungi, and actinomycetes are commonly carried on board probably via clothing, equipment, air currents during spacecraft handling and loading, food, and the astronauts themselves. Species of Alternaria, Aspergillus, Botrytis, Candida, Cephalosporium, Cladosporium, Fusarium, Mucor, Penicillium, Phoma, and Trichoderma were the most prevalent fungi recovered, and species of Bacillus, Escherichia, Klebsiella, Micrococcus, Pseudomonas, Staphylococcus, and Streptococcus were the most prevalent bacteria recovered from spacecraft. Most of these genera contain species that have been reported as plant pathogens. Strict quarantine procedures were not effective in preventing contamination of spacecraft during these missions. Research must be initiated to better understand how microorganisms interact with plants and animals in microgravity environments because microbial contamination of spacecraft and ALS modules cannot be avoided. An integrated pest management (IPM) program likely will be developed for managing plant disease outbreaks in space-based ALS systems.

Ecological Systems, Closed↗

PubMed2000

On the particularity of pathogens.

In the elemental struggle between pathogenic microbes and the immune system of the host, each strives for a unique advantage and thus each exploits its own unique particularities in pathogenesis and protection. And each presumably selects for the diversity that generally characterizes the wide range of successful host-pathogen interactions.

Anti-Bacterial Agents↗

PubMed2006

Cutaneous manifestations of syphilis : recognition and management.

After a marked decline in the number of syphilis cases in the context of AIDS prevention campaigns, a significant increase has been observed in states of the former Soviet Union since 1994. In recent years, outbreaks have also been reported in the US, Canada, and several European countries. The current epidemic in the US and in different parts of Europe has largely involved men who have sex with men, many of whom are infected with HIV. Since a misdiagnosis of syphilis can have serious consequences for the patient and also for pregnancies and newborns, clinicians should be aware of the many manifestations of syphilis and difficulties in the diagnosis and management of the disease. Younger clinicians in particular are no longer familiar with the diverse clinical symptoms and the complex diagnostics of syphilis. Patients co-infected with HIV may present with atypical clinical manifestations and laboratory test results. Furthermore, through its association with an increased risk of HIV infection, syphilis has acquired a new potential for morbidity and mortality, and the diagnosis of syphilis should be routinely considered in patients with uveitis, sudden deafness, aortic thoracic aneurysm, or pregnancy. Only a minority of syphilis infections are detected in the primary stage. This may be because of atypical locations and, occasionally, atypical morphology of the lesions; however, it may also be because of the difficulty of detecting the pathogen. In the secondary stage, which is clinically extremely diverse, the diagnosis is confirmed serologically. There is a need for increased awareness of the symptoms and signs of acute infections, together with a willingness to consider the diagnosis of syphilis in patients with vague symptoms. An increasing number of diagnostic tests (both specific and nonspecific) are now available. However, in the absence of clinical symptoms or in cases with a low titer or inconsistent test results, diagnosis of syphilis can be difficult or even impossible. Treatment and follow-up should follow current guidelines designed for the involved area. In this article, the cutaneous manifestations of syphilis and their diagnostic and therapeutic management are described in detail.

Anti-Bacterial Agents↗

PubMed1994

Spontaneous substitutions in the vicinity of the V3 analog affect cell tropism and pathogenicity of simian immunodeficiency virus.

Simian immunodeficiency virus (SIV) exists within tissues of infected macaques as a mixture of diverse genotypes. The goal of this study was to investigate the biologic significance of this variation in terms of cellular tropism and pathogenicity. PCR was used to amplify and clone 3'-half genomes from the spleen of an immunodeficiency SIV-infected pig-tailed macaque (Macaca nemestrina). Eight infectious clones were generated by ligation of respective 3' clones into a related SIVsm 5' clone, and virus stocks were generated by transient transfection. Four of these viruses were infectious for macaque peripheral blood mononuclear cells (PBMC) or monocyte-derived macrophages (MDM). Three viruses with distinct tropism for macaque PBMC or MDM were tested for in vivo infectivity and pathogenicity. The ability of these three viruses to infect PBMC and macrophages correlated with differences in infectivity and pathogenicity. Thus, a virus that was infectious for both PBMC and MDM was highly infectious for macaques and induced AIDS in half of the inoculated animals. In contrast, virus that was less infectious for PBMC and not infectious for MDM induced only transient viremia. Finally, a virus that was not infectious for either primary cell type did not infect macaques. Chimeric clones exchanging portions of the envelope gene of the 62A and smH4 molecular clones and a series of point mutants were used to map the determinant of tropism to a 60-amino-acid region of gp120 encompassing the V3 analog of SIV. Naturally occurring mutations within this region were critical for determining tropism and, as a result, pathogenicity of these SIVsm clones.

Amino Acid Sequence↗

PubMed2006

[Study on a bacterial strain Bt8 for biocontrol against citrus bacterial canker].

Citrus bacterial canker is an important disease of Citrus species in China. The disease severely occurs especially in the coastal area. Integrated control system has been used for the control of the disease, in which chemotherapy plays an important role at present. The chemotherapy-dominant control system brought many problems to the environment, such as chemical residua in the products and induction of resistance to fungicide(s) by the pathogen. To solve these problems, an intensive study on biocontrol of citrus bacterial canker is needed. Isolations and characterizations of biocontrol agents are the basis for biocontrol of the disease. A bacterial strain Bt8 with strong inhibiting ability against Xanthomonas axonopodis pv. citri (Hasse) Vauterin, was isolated from citrus orchard soil in Nanning, China. The isolated bacterial strain was identified and characterized as Acinetobacter baumannii Bouvet et Grimont on the base of its morphology and 16S rDNA sequence analysis as well as physiological and biochemical characters. The inhibiting activity of the bacterium suspension against the pathogen was significantly influenced by environmental factors, such as temperatures, pHs and media. At temperatures of 18 degrees C to 33 degrees C, both the inhibiting activity of the bacterium suspension and the biomass of the bacterium increased with the increases of temperatures, suggesting that the influence of temperature on inhibiting activity of the bacterium suspension was in dependence on the bacterial biomass. In NA liquid medium of pH 10, the bacterium suspension showed the highest inhibiting activity against Xanthomonas axonopodis pv. citri, which was not in dependence on biomass of the bacterium. The bacterium suspension provided 55.2% inhibition against bacterial canker under greenhouse conditions. The results showed that Acinetobacter baumannii has potential as biocontrol agent against bacterial canker disease. Acinetobacter baumannii was reported as the pathogens infecting human and animals. The present study enriched the understanding on biological diversity in Acinetobacter baumannii to sciences. This is the first report on the isolation of Acinetobacter baumannii with strong inhibiting ability against plant pathogen.

Acinetobacter baumannii↗

PubMed1984

Microbial colonization of human ileal conduits.

Morphological and microbiological techniques were used to locate and identify the microorganisms that colonized the human ileal conduits in 17 different patients from 5 days after surgery up to as many as 16 years of service as a urine conduit. The ecological sequence of this colonization assumes some practical importance because the ascending growth of pathogenic organisms in this essentially open, unvalved urinary tract diversion system leads to the development of life-threatening pyelonephritis. Extensive examination of the microvillus surfaces of the ilea of five accident victims by both transmission and scanning electron microscopy showed that these tissue surfaces were not colonized by bacteria, even in the absence of prophylactic antibiotic therapy, and that these surfaces were not occupied by adherent microorganisms after several years of service as a urine conduit, even when the skin surface stoma and the conduit contents were heavily colonized by bacteria and yeasts. During the initial period (10 days) of postoperative antibiotic therapy, the mucus and urine within the conduit were largely colonized by yeasts. A mixed population of yeasts and gram-positive cocci subsequently developed in the conduit itself, and gram-positive cocci were seen to be avidly adherent to epidermal cells at the stoma. As antibiotic protection was gradually withdrawn, gram-negative organisms became a part of the mixed microbial flora of the conduit contents, and some of the potentially pathogenic organisms of this group (e.g., Escherichia spp., Proteus spp., Pseudomonas spp., etc.) were isolated from patients with pyelonephritis that appeared to come from the ileal conduit.(ABSTRACT TRUNCATED AT 250 WORDS)

Bacteria↗

PubMed2006

In vitro biofilm formation of commensal and pathogenic Escherichia coli strains: impact of environmental and genetic factors.

Our understanding of Escherichia coli biofilm formation in vitro is based on studies of laboratory K-12 strains grown in standard media. However, pathogenic E. coli isolates differ substantially in their genetic repertoire from E. coli K-12 and are subject to heterogeneous environmental conditions. In this study, in vitro biofilm formation of 331 nondomesticated E. coli strains isolated from healthy (n = 105) and diarrhea-afflicted children (n = 68), bacteremia patients (n = 90), and male patients with urinary tract infections (n = 68) was monitored using a variety of growth conditions and compared to in vitro biofilm formation of prototypic pathogenic and laboratory strains. Our results revealed remarkable variation among the capacities of diverse E. coli isolates to form biofilms in vitro. Notably, we could not identify an association of increased biofilm formation in vitro with a specific strain collection that represented pathogenic E. coli strains. Instead, analysis of biofilm data revealed a significant dependence on growth medium composition (P < 0.05). Poor correlation between biofilm formation in the various media suggests that diverse E. coli isolates respond very differently to changing environmental conditions. The data demonstrate that prevalence and expression of three factors known to strongly promote biofilm formation in E. coli K-12 (F-like conjugative pili, aggregative adherence fimbriae, and curli) cannot adequately account for the increased biofilm formation of nondomesticated E. coli isolates in vitro. This study highlights the complexity of genetic and environmental effectors of the biofilm phenotype within the species E. coli.

Bacteremia↗

PubMed2005

Diversity in times of adversity: probabilistic strategies in microbial survival games.

Population diversification strategies are ubiquitous among microbes, encompassing random phase-variation (RPV) of pathogenic bacteria, viral latency as observed in some bacteriophage and HIV, and the non-genetic diversity of bacterial stress responses. Precise conditions under which these diversification strategies confer an advantage have not been well defined. We develop a model of population growth conditioned on dynamical environmental and cellular states. Transitions among cellular states, in turn, may be biased by possibly noisy readings of the environment from cellular sensors. For various types of environmental dynamics and cellular sensor capability, we apply game-theoretic analysis to derive the evolutionarily stable strategy (ESS) for an organism and determine when that strategy is diversification. We find that: (1) RPV, effecting a sort of Parrondo paradox wherein random alternations between losing strategies produce a winning strategy, is selected when transitions between different selective environments cannot be sensed, (2) optimal RPV cell switching rates are a function of environmental lifecycle asymmetries and environmental autocorrelation, (3) probabilistic diversification upon entering a new environment is selected when sensors can detect environmental transitions but have poor precision in identifying new environments, and (4) in the presence of excess additive noise, low-pass filtering is required for evolutionary stability. We show that even when RPV is not the ESS, it may minimize growth rate variance and the risk of extinction due to 'unlucky' environmental dynamics.

Bacteria↗

PubMed1993

Emerging fungal pathogens in immunocompromised patients: classification, diagnosis, and management.

Fungi such as Fusarium species, Trichosporon species, Curvularia species, and Alternaria species previously were thought to represent contamination or harmless colonization when isolated from immunocompromised patients. More recently, the pathogenic role of these and other fungi has been clearly established. Three diverse groups of fungi are responsible for these emerging infections: the agents of phaeohyphomycosis and hyalohyphomycosis and certain yeasts. Reports of the emergence of these organisms as significant pathogens may be ascribed to increasing awareness by physicians and microbiologists, aggressive culture of patient specimens, increasingly cytotoxic chemotherapy, and selection of resistant organisms by the widespread empirical use of amphotericin B. Infections with these fungi tend to be disseminated and are frequently fatal in immunocompromised hosts. Treatment of these infections is not standardized. Experimental therapy in murine models of fungal infections suggests a role for newer agents, combination antifungal chemotherapy, and immunotherapy.

Fungi↗

PubMed2004

Comparative analysis of Gtf isozyme production and diversity in isolates of Streptococcus mutans with different biofilm growth phenotypes.

Streptococcus mutans is the main pathogenic agent of dental caries. Glucosyltransferases (Gtfs) produced by these bacteria are important virulence factors because they catalyze the extracellular synthesis of glucans that are necessary for bacterial accumulation in the dental biofilm. The diversity of GtfB and GtfC isozymes was analyzed in 44 genotypes of S. mutans that showed a range of abilities to form biofilms in vitro. Several approaches were used to characterize these isozymes, including restriction fragment length polymorphism analysis of the gtfB and gtfC genes, zymographic analysis of the identified GtfB and GtfC genotypes, and quantitation of isozyme production in immunoblot experiments with specific monoclonal antibodies. A high diversity of gtf genes, patterns of enzymatic activity, and isozyme production was identified among the isolates tested. GtfC and, to a lesser extent, GtfB were produced in significantly higher amounts by strains that had high biofilm-forming ability than by strains with low biofilm-forming ability. Biofilm formation was independent of the GtfB and GtfC genotype. Atypical strains that showed an apparent single Gtf isozyme of intermediate size between GtfB and GtfC were also identified. The results indicate that various expression levels of GtfB and GtfC isozymes are associated with the ability of distinct S. mutans genotypes to grow as biofilms, strengthening the results of previous genetic and biochemical studies performed with laboratory strains. These studies also emphasize the need to identify factors that control gtf gene expression.

Bacterial Proteins↗

PubMed2005

HIV vaccines: brief review and discussion of future directions.

A major barrier to the design of a successful HIV vaccine is virus diversity,which is particularly apparent in the envelope glycoprotein, the target of neutralizing antibodies. An antibody generated to one envelope glycoprotein may not recognize an isolate bearing a different envelope glycoprotein. Thus, single-envelope glycoprotein vaccines have protected against homologous but not necessarily against heterologous challenge. Antigenic diversity has been addressed in the design of vaccines for other pathogens by the preparation of polyvalent vaccines. The poliovirus vaccine, for example, comprises three serotypes of poliovirus, a feature that was essential in providing full protection against polio infection. Similarly, the authors propose that overcoming HIV diversity is likely to require the administration of a cocktail of envelope glycoprotein antigens. Delivery of such an array of envelope glycoproteins will elicit a broad immune response that is potentially capable of recognizing the diverse population of HIV-1 isolates. This article reviews data relevant to the development of cocktail vaccines which have been designed to elicit a wide range of envelope glycoprotein-specific B- and T-cell responses.

AIDS Vaccines↗

PubMed2006

Performance, diarrhea incidence, and occurrence of Escherichia coli virulence genes during long-term administration of a probiotic Enterococcus faecium strain to sows and piglets.

As part of an interdisciplinary research project, the performance response of sows and their litters to the probiotic strain Enterococcus faecium NCIMB 10415, as well as some health characteristics of the piglets, were studied. Gestating sows (n = 26) were randomly allotted into 2 groups. The probiotic was administered by dietary supplementation to 1 group of sows and their respective litters (probiotic group), whereas the second group (control group) received no probiotic supplementation. The duration of the treatment was nearly 17 wk for sows (d 90 ante partum until d 28 postpartum) and 6 wk for piglets (d 15 to 56). Body weight and feed consumption were recorded weekly. The frequency of 4 toxin and 5 adhesion genes of putative pathogenic Escherichia coli was monitored weekly (d 7 to 35) by multiplex PCR assays, and fecal consistency of weaned piglets was studied daily. Probiotic treatment of lactating sows led to an overall pre-weaning mortality of 16.2% compared with 22.3% in the control group (P = 0.44). Animal losses during the first 3 d of the suckling period were decreased in the probiotic group (P = 0.09). For piglets (n = 153), which were weaned at 28 d, there were no overall treatment differences in BW gain, feed intake, or feed efficiency. Probiotic supplementation, however, led to nearly a 40% reduction (P = 0.012). The actual percentage of piglets with postweaning diarrhea in the probiotic group was 21% compared with 38% in the control group (P = 0.05). The study on virulence factors of dominant fecal E. coli isolates revealed a high diversity with varying frequency and distribution of each single pathogenicity gene. The 440 isolates carried 29 different pathogenicity gene combinations as well as each of the 9 pathogenicity genes alone. Altogether, isolates with more than 2 pathogenicity genes were quite rare (< or = 10%), and up until d 28 isolates without any pathogenicity gene occurred most frequently. Depending on the time of sampling, one-third or more of all isolates contained est2 or est1b as single gene or in combination with other pathogenicity genes.

Animal Feed↗

PubMed2004

Distribution, genetic diversity, and variable expression of the gene encoding hyaluronate lyase within the Streptococcus suis population.

Although Streptococcus suis is an economically important pathogen of pigs and an occasional cause of zoonotic infections of humans knowledge of crucial virulence factors, and as a consequence targets for therapeutic or prophylactic intervention, remains limited. Here we describe a detailed study of the distribution, diversity, and in vitro expression of hyaluronate lyase, a protein implicated as a virulence factor of many mucosal pathogens. The gene encoding hyaluronate lyase, hyl, was present in all 309 bona fide S. suis isolates examined representing diverse serotypes, geographic sources, and clinical backgrounds. Examination of the genetic diversity of hyl by RFLP and sequence analysis indicated a pattern of diversity shared by many gram-positive surface proteins with a variable 5' region encoding the most distal cell surface-exposed regions of the protein and a much more conserved 3' region encoding domains more closely associated with the bacterial cell. Variation occurs by several mechanisms, including the accumulation of point mutations and deletion and insertion events, and there is clear evidence that genetic recombination has contributed to molecular variation in this gene. Despite the ubiquitous presence of hyl, the corresponding enzyme activity was detected in fewer than 30% of the 309 isolates. In several cases this lack of activity correlates with the presence of mutations (either sequence duplications or point mutations) within hyl that result in a truncated polypeptide. There is a striking absence of hyaluronate lyase activity in a large majority of isolates from classic S. suis invasive disease, indicating that this protein is probably not a crucial virulence factor, although activity is present in significantly higher numbers of isolates associated with pneumonia.

Animals↗