Hemolysin Activity Research Articles

Raw bovine milk as a reservoir of yeast with virulence factors and decreased susceptibility to antifungal agents.

We identified 66 yeast isolates, including 26 different yeast species from 910 individual milk samples. Our results indicate that individual milk samples may serve as a source of yeasts with the potential to trigger infection and may have reduced sensitivity to tested antifungal agents.

Potential Pathogenicity of Candida Species Isolated from Oral Cavity of Patients with Diabetes Mellitus.

Introduction In the recent decade, the increased immunocompromised population such as diabetic patients makes a high incidence of invasive Candida infections. Diabetes mellitus is the most common endocrine metabolic disorder, and diabetic patients are more susceptible to oral candidiasis infection. Candidiasis is an opportunistic fungal infection caused by many species of Candida. Secretion of exoenzymes plays an important role in the virulence and pathogenesis of Candida species. The aim of this study was to evaluate the potential role of phospholipase, esterase, and hemolytic activity of Candida species isolated from oral cavity lesions of diabetic patients. Methods A total of 108 Candida species including 75 Candida albicans and 33 non-Candida albicans species were recovered from the oral cavity of diabetic patients included in our study. Egg yolk agar, Tween 80 opacity medium, and blood agar plate assays were used for determining phospholipase, esterase, and hemolytic activities, respectively. Results Candida albicans species had the most exoenzyme activity in comparison to non-albicans isolates. Candida albicans isolates showed 97.3%, 100%, and 77.3% phospholipase, hemolysin, and esterase activities, respectively. The difference between Candida albicans and non-Candida albicans was significant in phospholipase (P < 0.001) and hemolytic activity (P = 0.027), but not significant in esterase activity (P = 0.076). Conclusion This study showed that most of the isolates had different enzymatic patterns, and Candida albicans isolates had the most exoenzyme activity. So due to the potential effects of these enzymes in pathogenesis and virulence effects of Candida species, we can conclude that the severity of extracellular enzymes may play a role in the severity of signs and symptoms of Candida oral cavity infections in diabetic patients.

Pathogenicity Assessment of Colombian Strains of Candida auris in the Galleria mellonella Invertebrate Model.

Candida auris, first described in 2009, is an opportunistic pathogenic yeast that causes nosocomial outbreaks around the world, with high mortality rates associated with therapeutic failure. In this study, we evaluated the pathogenicity of 107 isolates from two cities in Colombia, associated with fungemia or colonization processes; to achieve this, we used the Galleria mellonella invertebrate model to compare pathogenicity. Our results showed that less than half of the total isolates of C. auris presented a high pathogenicity compared to the reference strain SC5314, and most of those highly pathogenic strains were from colonization processes. We observed that there was formation of large aggregates of cells that cannot be disrupted easily, without statistically significant differences between the pathogenicity of the aggregated and non-aggregated strains. In addition, protease activity was observed in 100% of the C. auris strains; phospholipase and hemolysin activity were observed in 67.3 and 68.2% of the studied strains, respectively. In conclusion, these results highlight the utility of determining survival using G. mellonella, which allowed us to provide new information on the pathogenicity, enzymatic activity, and the relationship of the aggregated and non-aggregated phenotypes of C. auris in this model.

Genotyping, antifungal susceptibility, enzymatic activity, and phenotypic variation in Candidaalbicans from esophageal candidiasis.

BackgroundEsophageal candidiasis is the most frequent form of esophagitis. The pathogenicity of Candida spp. is related to a combination of microbial factors, hydrolytic enzyme secretion and phenotypic switching. This study was designed to investigate esophageal candidiasis, antifungal activity, enzymatic activity patterns, phenotyping, and genotyping profiles of Candida albicans species.MethodsNine hundred thirty‐three visited patients were evaluated, and esophageal biopsies from patients were included in this study during 2019–2020. Direct smear, Gram staining, and culture on CHROMagar were performed for each sample. Isolated species were identified with conventional procedures and PCR‐RFLP. Susceptibility to antifungals was determined according to CLSI guidelines. ABC typing, phenotype switching, hemolysin, proteinase, phospholipase, and esterase activity were also determined with the appropriate protocols.ResultsTwenty‐three (2.5%) patients (mean age 55.2 years) were diagnosed with esophageal candidiasis. The species isolated were 19(82.6%) C. albicans, 3(13.1%) C. glabrata, and 1(4.3%) C. tropicalis. Genotype A (57.9%) was the predominant type in C. albicans isolates. 50% of C. albicans isolates exhibited a white phenotype. A high level of phospholipase (47.4%), hemolysin (68.4%), and proteinase activity (36.8%) was observed in the C. albicans isolates. Only three C. glabrata isolates displayed non‐wild type susceptibility to voriconazole and itraconazole.ConclusionThis study shows that C. albicans are still the most frequent isolates from patients with esophageal candidiasis. The predominance of genotype A, the white phenotype, and strong hemolysin activity may indicate a high prevalence of pathogenicity in these isolates. Sensitivity to antifungal drugs was greatest for amphotericin and fluconazole.

The corruption of innate immunity by Streptococcus anginosus group

Abstract Streptococcus anginosus group (SAG), formerly known as Streptococcus milleri, consists of three distinct streptococcal species: Streptococcus anginosus, Streptococcus constellatus, and Streptococcus intermedius. SAG was considered as commensal bacteria of colon, oral cavity and vagina. Recent observation reported those bacteria as potent pathogens found in brain or liver abscess. Mechanism of SAG pathogenesis is still unknown, despite the strong set of clinical data. In our study, we determined the virulence of different SAG clinical isolates by examining the activity of hemolysins, DNAses and proteases. By using Dictyostelium discoideum as model for screening SAG virulence we selected a few high and low virulence strains out of 41 SAG isolates. Finally, we established and characterized the infection process of selected SAG strains by wax worm Galleria mellonella. Therefore, we aimed to characterize how those bacteria can interact with human innate immunity. In our experiments, using both human serum and whole blood we demonstrated, that these bacteria are resistant to killing by non-specific mechanisms of the immune response. Our studies have demonstrated that SAG have numerous virulence factors which differ among examined strains, and which allow bacteria to effectively colonize the human body and avoid elimination by the immune system. Supported by National Science Centre, Poland 2018/29/B/NZ6/00624

Virulence Factors and Antifungal Susceptibility Profile of C. tropicalis Isolated from Various Clinical Specimens in Alexandria, Egypt

Background: The incidence of candidiasis caused by non-albicans Candida (NAC) species is increasing. Candida tropicalis has emerged as one of the most important NAC species. This study aims to examine the antifungal susceptibility profile and some virulence factors of C. tropicalis isolated from various clinical specimens. Methods: A total of 71 C. tropicalis isolates from various clinical specimens (69.01%, 18.31%, 9.86%, and 2.82% of isolates were collected from urine, respiratory samples, blood, and skin and soft tissue infections, respectively) from ICU patients in Alexandria, Egypt. The isolates were identified at species level by CHROMagar Candida and VITEK 2 compact system. Furthermore, the antifungal susceptibility was determined using the VITEK 2 system AST-YS07 card containing different antifungals. Hemolysin, phospholipase, and proteinase activity and biofilm formation were also tested as virulence factors. Results: Only 30 isolates (42.25%) were non-susceptible (MIC ≥ 4 µg/mL) to fluconazole, of which 28 isolates showed non-susceptibility (MIC ≥ 0.25 µg/mL) to voriconazole. All isolates showed both hemolysin and proteinase activities, while only 9 isolates (12.68%) showed phospholipase production and 70 isolates (98.59%) demonstrated biofilm formation. Strong biofilm production was observed among the blood culture isolates (85.71%), followed by the respiratory and urinary isolates (61.54% and 46.94%, respectively). Conclusions: This study sought to provide useful data on the antifungal susceptibility of C. tropicalis isolates from ICU patients suffering from invasive infections with an increased trend towards elevated MICs levels of both fluconazole and voriconazole. Due to the high incidence of systemic candidiasis and antifungal resistance, C. tropicalis is emerging as a serious root of infections. Therefore, early and accurate identification of Candida species along with susceptibility testing is of utmost importance.

Identification, genotyping and invasive enzyme production of oral Candida species from denture induced stomatitis patients and healthy careers

ObjectiveDenture induced stomatitis (DIS) is often associated withCandida infection. This study aimed to identify oral Candida species from DIS patients and healthy careers and to evaluate their invasive enzyme production. MethodsCandida from DIS patients (n = 38) and healthy careers (n = 23) were identified using chromogenic agar and molecular techniques. Phospholipase, esterase and hemolysin activities of C. albicans were evaluated using in vitro assays. ResultsChromogenic agar revealed 29 C. albicans and 09 non-C. albicans Candida among pathogenic isolates. Commensal isolates consisted of 18 C. albicans and 05 non-C. albicans Candida. PCR-RFLP analysis identified C. albicans (76.3 %) as the commonest pathogenic species followed by C. glabrata (13.2 %), C. parapsilosis (5.3 %) and C. tropicalis (5.3 %). Within commensal isolates, C. albicans (78.3 %) was leading followed by C. parapsilosis (13 %), C. glabrata (4.3 %) and C. guilliermondii (4.3 %). Furthermore, ABC genotyping revealed that pathogenic C. albicans genotype A (69 %) was predominant followed by genotypes C (20.7 %) and B (10.3 %). Commensal C. albicans had only the genotype A. Phospholipase, esterase and hemolysin activities of pathogenic C. albicans were significantly higher (P < 0.05) than that of commensals. ConclusionsC. albicans is the leading Candida species isolated from DIS patients and healthy careers. C. albicans genotype A remains predominant in both pathogenic and commensal isolates while prevalence of genotype C is more than the genotype B among the pathogenic isolates. C. albicans from DIS patients has significantly higher phospholipase, esterase and haemolysin activities compared to commensals which may contribute in pathogenesis.

Quantitative Hemolysis Assays.

Many strains of Staphylococcus aureus produce a variety of cytolysins that target many different cell types to both fight the immune system and acquire nutrients. This includes hemolysins which destroy erythrocytes and are well studied virulence factors. Traditionally, hemolysin activity is measured on blood agar plates due to the simplicity of the assay. While this is telling, it cannot encapsulate the full story because S. aureus is known to behave differently in broth and on agar. Furthermore, plate-based assays are primarily semiquantitative and often a more accurate determination of hemolytic potential is needed to discern differences between strains. Here, we describe a method to quantify hemolysin activity from broth or similarly grown cells.

Assessment of Vibrio parahaemolyticus levels in oysters (Crassostrea virginica) and seawater in Delaware Bay in relation to environmental conditions and the prevalence of molecular markers to identify pathogenic Vibrio parahaemolyticus strains.

This study identified Vibrio parahaemolyticus in oyster and seawater samples collected from Delaware Bay from June through October of 2016. Environmental parameters including water temperature, salinity, dissolved oxygen, pH, and chlorophyll a were measured per sampling event. Oysters homogenate and seawater samples were 10-fold serially diluted and directly plated on CHROMagarᵀᴹ Vibrio medium. Presumptive V. parahaemolyticus colonies were counted and at least 20% of these colonies were selected for molecular chracterization. V. parahaemolyticus isolates (n = 165) were screened for the presence of the species-specific thermolabile hemolysin (tlh) gene, the pathogenic thermostable direct hemolysin (tdh)/ thermostable related hemolysin (trh) genes, the regulatory transmembrane DNA-binding gene (toxR), and V. parahaemolyticus metalloprotease (vpm) gene using a conventional PCR. The highest mean levels of the presumptive V. parahaemolyticus were 9.63×103 CFU/g and 1.85×103 CFU/mL in the oyster and seawater samples, respectively, during the month of July. V. parahaemolyticus levels in oyster and seawater samples were significantly positively correlated with water temperature. Of the 165 isolates, 137 (83%), 110 (66.7%), and 108 (65%) were tlh+, vpm+, and toxR+, respectively. Among the V. parahaemolyticus (tlh+) isolates, 7 (5.1%) and 15 (10.9%) were tdh+ and trh+, respectively, and 24 (17.5%), only oyster isolates, were positive for both genes. Potential pathogenic strains that possessed tdh and/or trh were notably higher in oyster (39%) than seawater (15.6%) isolates. The occurrence of total V. parahaemolyticus (tlh+) was not necessarily proportional to the potential pathogenic V. parahaemolyticus. Co-occurrence of the five genetic markers were observed only among oyster isolates. The co-occurrence of the gene markers showed a relatedness potential of tdh occurrence with vpm. We believe exploring the role of V. parahaemolyticus metalloprotease and whether it is involved in the toxic activity of the thermostable direct hemolysin (TDH) protein can be of significance. The outcomes of this study will provide some foundation for future studies regarding pathogenic Vibrio dynamics in relation to environmental quality.

Prevalence, virulence and antifungal activity of C. albicans isolated from infected root canals

BackgroundThere is limited data on the prevalence of Candida species in infected root canal systems of human teeth. We attempted to investigate the prevalence, genotype, virulence and the antifungal susceptibility of Candida albicans isolated from infected root canals of patients with primary and post-treatment infections in a UAE population.MethodsMicrobiological samples from 71 subjects with infected root canals were aseptically collected, and cultured on Sabouraud dextrose agar, and C. albicans was identified using multiplex polymerase chain reaction, and the isolates were further subtyped using ABC genotyping system. Their relative virulence was compared using further four archival samples of endodontic origin from another geographical region, and four more salivary isolates, as controls. The virulence attributes compared were biofilm formation, and production of phospholipase and haemolysin, and the susceptibility to nystatin, amphotericin B, ketoconazole, and fluoconazole was also tested.Results4 out of 71 samples (5.6%) yielded Candida species. On analysis of variance among the groups, the intracanal isolates, mainly Genotype A, possessed a high degree of phospholipase and haemolysin activity (p < 0.05). The UAE and Finland isolates were stronger biofilm formers and had superior phospholipase production capacity compared with the salivary isolates. All isolates were sensitive to the antifungal chemicals used. The salivary isolates were more sensitive to fluoconazole compared to other groups (p < 0.05).ConclusionThe prevalence of C. albicans in infected root canals of patients attending a dental hospital in UAE is low. The strains isolated were good biofilm formers, possessed strong phospholipase and haemolysin activity and were mostly of the genotype A. The fact that the root canal isolates possessed significant hydrolase activity, imply that they are equipped with virulence attributes necessary for survival within a harsh intracanal ecosystem.

Do mangrove habitats serve as a reservoir for Medicopsis romeroi, a clinically important fungus

Medicopsis romeroi is one of the frequent pathogens causing subcutaneous infections in immunocompromised patients. In this study, a sexual morph of Medicopsis romeroi was found on a decaying woody stem of the mangrove plant Suaeda monoica and its asexual morph was produced on malt extract agar. The sexual morph connection was established based on both morphological data and multigene phylogenetic analyses. Neomedicopsis chiangmaiensis comb. nov. is proposed by transferring Medicopsis chiangmaiensis to the genus Neomedicopsis based on morphology and multigene phylogenetic analyses. The preliminary pathogenicity tests on Medicopsis romeroi strain demonstrated beta haemolysin and esterase activities, and its ability to grow at 37 °C. It also exhibited strong activity in in vitro tests for aspartyl proteases, extracellular phospholipase, lipase and chitinase and mild activity for amylase and urease suggesting that this strain of Medicopsis romeroi, isolated from a mangrove habitat, could be an opportunistic pathogen to immunocompromised patients.

High detection of virulence factors by Candida species isolated from bloodstream of patients with candidemia

ObjectiveCandida species are the normal inhabitants of the skin and mucosa that cause a wide range of debilitating diseases in immunocompromised patients and other susceptible individuals. The present study aimed to evaluate the production of exoenzymes and the biofilm formation capacity of Candida species isolated from candidemia. Materials and methodsIn this study, a total of 100 stock Candida species isolates consist of 50 Candida albicans and 50 non-Candida albicans Candida species (24 C. glabrata, 15 C. parapsilosis, 5 C. dubliniensis, 3 C. tropicalis, 2 C. krusei and 1 C. fabianii) which previously were recovered from patients with candidemia were used. The enzymatic activity tests for hemolysin, proteinase, and phospholipase were performed by using blood Sabouraud dextrose agar, bovine serum albumin medium and egg yolk agar, respectively. Biofilm formation was determined by microplate assay method. ResultAll of the Candida albicans species could produce hemolysin. The predominant enzyme activity of species included strong and very strong levels of phospholipase, proteinase and hemolysin activity were belonged to Candida albicans isolates. There were statistically significant differences in hemolysin (P < 0.001), proteinase (P = 0.003) and phospholipase (P < 0.001) activity between two groups of albicans and non-albicans species. The biofilm formation was seen in 30 (60%) of C. albicans and 49 (98%) of non-C. albicans species. There was significant statistical differences between the two groups of isolates in biofilm formation (P < 0.001). ConclusionIt is clear that Candida species have ability to produce several enzymes as virulence factors to contribute its pathogenicity. There were significant differences in virulence factors between the two C. albicans and non- C. albicans group. The ability for biofilm formation and producing exo-enzyme were an important virulence factors in Candida species isolates. This differences found in this report might have role in severity of disease caused by different species.

Effect of Acridine Orange on Pathogenicity of E. coli Isolated from Urinary Tract Infection Patients

A total of (108) isolate from Urinary tract infection (UTI) patients, only (47) isolate gave a positive result(43.51%) after a number of morphological and biochemical characterization. Our result showed only 28isolate have the ability for protease production and haemolysin production (59.5%), and E. coli no.6 wasthe highest protease production isolate (24mm of lysis area) while the E. coli no.18 was lowest proteaseproduction (12 mm of lysis area). After incubtion on skim milk agar medium at 37°C for 18h and with(100%) haemolysin activity for all 28 isolates after growing on blood agar medium. In our study, firstattempt made on the effect of acridine orange (0.1%) as a curing agent on virulence factors of pathogenicbacteria ( both protease and haemolysin productin) by highly producer E. coli no.6 at concentrations ( 0, 10-1to 10-10) and the results showed that E. coli no.6 loss the protease and haemolysin productin at concentrationof (10-1 to 10-4) while little and normal activities were observed at concentration of (10-5 to 10-10) of acridineorange. Also, this study was investigate the agarose - gel electrophoresis of both cured and normal cells andthe results showed the presence of both chromosomal and plasmid bands in the normal cells and only thepresence of chromosomal band for the cured cells E. coli treated with acridine orange at concentrations of(10-2 to 10-4).

In vitro antifungal activity of Cinnamomum zeylanicum bark and leaf essential oils against Candida albicans and Candida auris

Candida infections are a significant source of patient morbidity and mortality. Candida albicans is the most common pathogen causing Candida infections. Candida auris is a newly described pathogen that is associated with multi-drug-resistant candidiasis and candidaemia in humans. The antifungal effects of various essential oils and plant compounds have been demonstrated against human pathogenic fungi. In this study, the effect of cinnamon leaf and bark essential oils (CEOs) was determined against both C. albicans and C. auris. The disc diffusion (direct and vapour) and broth microdilution method was used to determine antifungal activity of the EOs against selected strains (C. albicans ATCC 10231, C. albicans ATCC 2091 and C. auris NCPF 8971) whilst the mode of action and haemolysin activity of the CEOs were determined using electron microscopy and light microscopy. Direct and vapour diffusion assays showed greater inhibitory activity of bark CEO in comparison with leaf CEO. The minimum inhibitory concentrations (MICs) and minimum fungicidal concentrations (MFCs) of bark CEO for all tested strains was below 0.03% (v/v), which was lower than the MICs of the leaf CEO (0.06–0.13%, v/v) dependent on the strain and the MFCs at 0.25% (v/v). In the morphological interference assays, damage to the cell membrane was observed and both CEOs inhibited hyphae formation. The haemolysin production assay showed that CEOs can reduce the haemolytic activity in the tested C. albicans and C. auris strains. At low concentrations, CEOs have potent antifungal and antihaemolytic activities in vitro against C. albicans and C. auris.Key points• Essential oils from Cinnamomum zeylanicum Blume bark and leaf (CBEO and CLEO) demonstrated fungicidal properties at very low concentrations.• The antifungal activity of CBEO was greater than that of CLEO consistent with other recent published literature.• The mode of action of CBEO and CLEO was damage to the membrane of C. albicans and C. auris.• Both CBEO and CLEO inhibited the formation of hyphae and reduced haemolysin production in C. albicans and C. auris.Graphical abstract

Virulence and in vitro antifungal susceptibility of Candida albicans and Candida catenulata from laying hens

In spite of evidence that domestic and wild birds may act as carriers of human pathogenic fungi, data on the role of laying hens as reservoirs of drug resistant and virulent yeasts is lacking. Here, we assess several virulence factors (phospholipase and haemolysin activity) and the antifungal susceptibility profiles of 84 Candida albicans and 17 Candida catenulata strains isolated from cloacae (group A), faeces (group B) and eggs (group C) of laying hens. Of these strains, 95% C. albicans and 23% C. catenulata strains displayed phospholipase and haemolytic activities. For C. albicans, the highest values of phospholipase (Pz = 0.62) and haemolytic activities (Hz = 0.49) were recorded among the strains from group C whilst for C. catenulata (Pz = 0.54; Hz = 0.49) among those from group A. High minimum inhibitory concentration (MIC) values for azoles and amphotericin B (AmB) were recorded irrespective of their sources in all C. albicans strains. A total of 22 C. albicans strains were multidrug resistant, displaying resistance to fluconazole, itraconazole (ITZ), voriconazole (VOR) and posaconazole (POS). All C. catenulata strains from group C were resistant to ITZ, POS, micafungin and anidulafungin and susceptible to AmB. In this study, C. albicans and C. catenulata isolated from the cloacae, faeces and eggs of laying hens produced phospholipase and haemolysin and might be multidrug resistant. In the environment (faeces) or in eggs, C. albicans and C. catenulata strains might acquire pathogenic virulence traits and/or show multidrug resistance profiles. Based on these results, breeding and handling of laying hens and/or eggs may have implications for human and animal health.

Laurel extracts inhibit Quorum sensing, virulence factors and biofilm of foodborne pathogens

Antimicrobial, antibiofilm, anti-Quorum sensing (QS) and virulence factors inhibitory capacity of different polarity Laurus nobilis extracts against several pathogenic microorganisms were studied. Some extracts exhibited antibiotic effect against Staphylococcus aureus multidrug-resistant strains. However, all extracts (100 μg/mL) inhibited to some extent the biofilm of most bacteria tested (until 40% for Gram-negative and 76% for Gram-positive). Hexane (HE) and chloroform extract (CE) were potent inhibitors of S. aureus biofilm and the microscopies further confirmed an important reduction in adherent cells. Polystyrene surfaces coated with these extracts showed a decrease in bacterial adhesion with the resulting inhibition of S. aureus biofilm formation and biofilm activity. Moreover, they also interfere with the coagulase and hemolysin activities of this bacterium. With respect to Gram-negative bacteria, these extracts showed anti-QS activity against Chromobacterium violaceum and inhibited biofilm formation, swarming motility, pyocyanin production, and elastase activity of Pseudomonas aeruginosa. Chemical analysis of HE and CE revealed that the fatty acids were the main compounds, particularly linolenic, oleic and hexadecanoic acids followed by the oxygenated monoterpenes. Non-toxic laurel extracts offer a natural alternative to control contamination and/or spoilage of food, as well as infectious diseases, by attacking the biofilm and the virulence of Gram-positive and Gram-negative bacteria.

Diclofenac mitigates virulence of multidrug-resistant Staphylococcus aureus.

Staphylococcus aureus is an opportunistic pathogen that has the ability to cause a wide range of diseases including superficial infection and severe invasive life threatening infections. The pathogenicity of S. aureus is mediated by a group of virulence factors that mediate the colonization and penetration. The antibiotic resistance of S. aureus has evolved due to the abuse of antibiotics rendering the cure of infection very difficult especially with the shortage in new antibiotic production. To combat this shortage, repurposing of FDA-approved drugs against the virulence factors is a new strategy. The analgesic drug Diclofenac was found to have anti-virulence activity against Pseudomonas aeruginosa and Proteus mirabilis. This study aimed to demonstrate the anti-virulence effect of diclofenac against clinical MRSA isolates phenotypically and genotypically using qRT-PCR. In this study, diclofenac showed significant reduction in biofilm formation when compared to controls, the inhibition ranged between 22.67% and 70%. Also, remarkable inhibition of hemolysin activity was found (5.4-66.34%). Additionally, diclofenac has inhibitory activity against the staphyloxanthin production (8-57.2%). The results were confirmed by qRT-PCR that showed significant down-regulation of tested virulence genes. The down-regulation ranged from 43 to 64.05% for SarA, 36.85-64.75% for AgrA, 50-63.2% for hla, 38.55-60.35% for FnbA, 46.75-61.05% for IcaA, 27.55-64% for SigB and 51.05-72.8% for CrtM. In conclusion, diclofenac can be used in combination with antibiotics as anti-virulence agent against MDR-MRSA which will enhance the ability of immune system to eradicate infection.

Occurrence of Bacillus cereus in instant cereal products and their hygienic properties

From July 1992 to June 1993, 155 instant cereal products were purchased from 24-hour stores, supermarkets and grocery stores in Taipei area and examined for Bacillus cereus, coliform bacteria, Escherichia coli and aerobic plate count. The results showed that B. cereus was found on 32% of instant cereal products examined. The isolation rates of B. cereus in regular instant cereal and cereal mix were 26% and 38%, respectively. Count range of B. cereus in all positive samples was 3 - 93 MPN/g. Aerobic plate counts of these two categories ranged between 5 - 2.3 × 104 CFU/g and 5 - 4.2 × 103 CFU /g, respectively. Among all samples, only one cereal mix sample was illegally contaminated with E. coli , while 8 samples contained coliform bacteria. Coliform was isolated from 2 of 74 (2.7%) regular instant cereal products, but isolated from 6 of 81 (7.4%) cereal mix products, except those of only one cereal mix were beyond sanitary standard. All of 44 B. cereus isolates had strong hemolysin activity, but only 4 isolates were capable of producing diarrheagenic enterotoxin.

Comparative Analysis of Putative Virulence-Associated Factors of Microsporum canis Isolates from Human and Animal Patients.

Microsporum canis is a zoophilic dermatophyte and the most common fungus isolated from dogs and cats worldwide. To invade skin, this pathogen uses different enzymes, which may be associated with virulence, that contribute to the fungal pathogenicity. The aim of this study is to compare the expression of enzymes that may be associated with virulence, and thermotolerance of M. canis strains isolated from dogs, cats, and humans. The in vitro expression of the enzymes keratinase, catalase, urease, hemolysin, and aspartic protease was evaluated in 52M. canis strains recently isolated from 14 human patients, 12 dogs, 15 symptomatic, and 11 asymptomatic cats. In addition, thermotolerance was assessed by comparative analysis of fungal growth at 25°C and 35°C. Keratinase activity was low in 34 and moderate in 18 strains. Aspartic-protease activity was low in 7, moderate in 33, and high in 12 strains. Hemolysin activity was low in 44 and moderate in 8 strains. All strains were classified as low producers of catalase. All but three strains produced urease in vitro, with a broad range of activity. The strains presented in vitro growth at the two studied temperatures were classified as presenting low (36.5%), medium (44.3%), or high (19.2%) thermotolerance. There was no statistically significant difference in the new putative virulence-associated factors studied among the different hosts, which suggests that they may have a similar role on human, cat, and dog infection. Also, no difference was observed between strains isolated from symptomatic and asymptomatic cats. This suggests that these factors have a limited impact on the fate of feline dermatophytosis caused by M. canis.

Purification and Characterization of Alpha Toxin Clostridium perfringens Type A

Clostridium perfringens is a toxin-producing anaerobe with the ability to cause multiple diseases in humans and animals. One of the toxins produced by all strains of this bacterium is an alpha toxin (phospholipase C). This study aimed to purify and characterize alpha-toxin. C. perfringens type A was grown in an optimized medium, the culture supernatant was separated, and ammonium sulfate precipitated protein was subjected to ion exchange and gel filtration chromatography methods. The purification steps were monitored by SDS-PAGE and hemolysin activity for each sample and performed by the hemolysin assay method. The purified alpha-toxin appeared in a single band in 43 KDa. The enzymatic efficiency yield was about 88% with a specific activity of 69170 and 654 fold of purification. According to the results, alpha-toxin is Zn and Mg metal-enzyme dependent on the temperature and pH optimum of 40 °C and 6, respectively. The enzyme Km and Vmax values of 3.8 mg/ml and 0.19 were calculated as the enzyme in the presence of lecithin. The partially purified alpha toxin with specific characters can be used for different applications such as antibody production and determination of the anti-toxin rate in animal serum.