Comparison of the efficacy of different blood medium in determining the hemolytic activity of Candida species

Exploring phenotypic and genotypic diversity among methicillin-resistant, vancomycin-resistant, and sensitive Staphylococcus aureus

BACKGROUND

Methicillin-Resistant Staphylococcus aureus (MRSA) is a global concern owing to the increasing prevalence of multidrug-resistant (MDR) strains. Vancomycin has been the primary treatment for MRSA; however, Vancomycin-resistant strains are being increasingly reported worldwide. Therefore, comparative studies are essential to support antimicrobial stewardship and improving clinical management. Ultimately, the findings from this study are expected to inform treatment strategies and guide public health interventions effectively.

MATERIAL AND METHODS

This study investigated the prevalence, antimicrobial resistance, and virulence characteristics of Vancomycin-sensitive S. aureus (VSSA) and Vancomycin-resistant S. aureus (VRSA) within MRSA strains. By employing a combination of phenotypic methods, such as antimicrobial susceptibility testing, and genotypic techniques, including molecular typing and identification of virulence genes, we obtained comprehensive insights into VRSA and VSSA profiles.

RESULTS

Of 250 clinical samples, 62 (24.8%) were S. aureus and 27 (43.5%) were identified as MRSA. All MRSA isolates exhibited MDR patterns. Most MRSA strains were VSSA (20/27, 74.1%), while 7 (25.9%) were VRSA. The VRSA isolates showed more antimicrobial resistance than VSSA isolates; however, the VRSA isolates had less virulence than VSSA isolates. Linezolid was the most effective treatment, with a 3.7% resistance rate. A higher percentage of biofilm-producing MRSA (96.3%) was confirmed by both phenotypic and genotypic methods. All isolates, except one VRSA, showed multi-virulence patterns (harbored more than 3 virulence genes). High diversity and low clonality (D-value = 0.99) were found in both VSSA and VRSA. Based on our correlation findings, the emergence of vancomycin resistance could modify the association between antimicrobial resistance and virulence, potentially affecting the pathogenic profile of these strains. The study also revealed complex interactions among host factors (including age and gender), sample origin, antimicrobial resistance, biofilm production, and virulence genes.

CONCLUSION

This study highlights the alarming spread of MRSA and VRSA, which show significant resistance and virulence.

Proven anti-virulence therapies in combating methicillin- and vancomycin-resistant Staphylococcus aureus infections

Introduction

Despite years of efforts to develop new antibiotics for eradicating multidrug-resistant (MDR) and multi-virulent Methicillin-Resistant Staphylococcus aureus (MRSA) and Vancomycin-Resistant Staphylococcus aureus (VRSA) infections, treatment failures and poor prognoses in most cases have been common. Therefore, there is an urgent need for new therapeutic approaches targeting virulence arrays. Our aim is to discover new anti-virulence therapies targeting MRSA and VRSA virulence arrays.

Methodology

We employed phenotypic, molecular docking, and genetic studies to screen for anti-virulence activities among selected promising compounds: Coumarin, Simvastatin, and Ibuprofen.

Results

We found that nearly all detected MRSA and VRSA strains exhibited MDR and multi-virulent profiles. The molecular docking results aligned with the phenotypic and genetic assessments of virulence production. Biofilm and hemolysin productions were inhibited, and all virulence genes were downregulated upon treatment with sub-minimum inhibitory concentration (sub-MIC) of these promising compounds. Ibuprofen was the most active compound, exhibiting the highest inhibition and downregulation of virulence gene products. Moreover, in vivo and histopathological studies confirmed these results. Interestingly, we observed a significant decrease in wound area and improvements in re-epithelialization and tissue organization in the Ibuprofen and antimicrobial treated group compared with the group treated with antimicrobial alone. These findings support the idea that a combination of Ibuprofen and antimicrobial drugs may offer a promising new therapy for MRSA and VRSA infections.

Conclusion

We hope that our findings can be implemented in clinical practice to assist physicians in making the most suitable treatment decisions.

Mechanism of Candida pathogenesis: revisiting the vital drivers

Candida is the most implicated fungal pathogen in the clinical setting. Several factors play important roles in the pathogenesis of Candida spp. Multiple transcriptional circuits, morphological and phenotypic switching, biofilm formation, tissue damaging extracellular hydrolytic enzymes, metabolic flexibility, genome plasticity, adaptation to environmental pH fluctuation, robust nutrient acquisition system, adherence and invasions (mediated by adhesins and invasins), heat shock proteins (HSPs), cytolytic proteins, escape from phagocytosis, evasion from host immune system, synergistic coaggregation with resident microbiota, resistance to antifungal agents, and the ability to efficiently respond to multiple stresses are some of the major pathogenic determinants of Candida species. The existence of multiple connections, in addition to the interactions and associations among all of these factors, are distinctive features that play important roles in the establishment of Candida infections. This review describes all the underlying factors and mechanisms involved in Candida pathogenesis by evaluating pathogenic determinants of Candida species. It reinforces the already available pool of data on the pathogenesis of Candida species by providing a clear and simplified understanding of the most important factors implicated in the pathogenesis of Candida species. The Candida pathogenesis network, an illustration linking all the major determinants of Candida pathogenesis, is also presented. Taken together, they will further improve our current understanding of how these factors modulate virulence and consequent infection(s). Development of new antifungal drugs and better therapeutic approaches to candidiasis can be achieved in the near future with continuing progress in the understanding of the mechanisms of Candida pathogenesis.

Comparative Analysis of Virulence Factors of Homozygous and Heterozygous Strains of Candida albicans Vaginal Isolates

Although the epidemiology of pathogenic Candida species is changing due to invasive diseases, Candida albicans has become the common cause of human infections worldwide. Candida albicans is a diploid yeast with a mostly clonal mode of reproduction and without known complete sexual cycle. This species has two heterozygous and homozygous strains at hyphal wall protein 1 gene locus (hwp1). Little is known about virulence factors of these strains. The aim of this study was to evaluate the exoenzyme activity of heterozygous and homozygous C. albicans strains. A total of 60 stock Candida albicans species isolates, which consisted of 30 homozygous and 30 heterozygous strains, were used for exoenzyme activities. We used egg yolk agar, Sabouraud blood agar, and bovine serum albumin agar for evaluation of phospholipase, hemolysin, and proteinase activity, respectively. Homozygous strains of Candida albicans had more phospholipase and proteinase activity than heterozygous strains. However, there were no significant statistical differences between the two strains in the severity of exoenzymes production. Beta hemolysin activity was seen in 100% and 96.7% of the homozygous and heterozygous strains, respectively. The results of this study indicated that both of the strains exhibited exoenzyme activities in different ranges. There were no significant statistical differences in virulence factors between the homozygous and heterozygous strains.

How much do we know about hemolytic capability of pathogenic Candida species?

Hemolytic factor production by pathogenic Candida species is considered an important attribute in promoting survival within the mammal host through the ability to assimilate iron from the hemoglobin-heme group. Hemolytic capability has been evaluated for Candida species based on hemolysis zones on plate assay, analysis of hemolytic activity in liquid culture medium, and hemolysis from cell-free culture broth. The production of hemolytic factor is variable among Candida species, where C. parapsilosis is the less hemolytic species. In general, no intraspecies differences in beta-hemolytic activities are found among isolates belonging to C. albicans, C. glabrata, C. krusei, C. tropicalis, and C. parapsilosis. The production of hemolytic factor by Candida species is affected by several factors such as glucose supplementation in the culture medium, blood source, presence of erythrocytes and hemoglobin, and presence of electrolytes. On the basis of existing achievements, more researches are still needed in order to extend our knowledge about the biochemical nature of hemolytic molecules produced by distinct Candida species, the mechanism of hemolysis, and the molecular basis of the hemolytic factor expression.

Hemolytic capability and expression of a putative haem oxygenase-encoding gene by blood isolates of Candida tropicalis are influenced by iron deprivation and the presence of hemoglobin and erythrocytes

Although hemolytic activity is known to be a putative virulence factor contributing to candidal pathogenesis, its production by Candida tropicalis, a species closely related to Candida albicans, is poor understood. The present study was undertaken to evaluate the hemolytic activity and the expression level of a putative haem oxygenase encoding gene by blood isolates of C. tropicalis following growth in iron deprivation, and in the presence of hemoglobin and erythrocytes. The lowest values of hemolytic activity were observed in cell-free culture supernatants of isolates growing in iron-restricted medium (RPMI medium and RPMI medium supplemented with iron chelator bathophenanthrolindisulphonic acid). Hemolysis was increased in the presence of either hemoglobin or erythrocytes. Reverse transcriptase PCR analysis showed that the putative haem oxygenase encoding gene (CtHMX1), potentially related with iron uptake, was up-regulated (p < 0.001) following growth in iron deprivation and in the presence of hemoglobin; CtHMX1 was repressed in the presence of human erythrocytes (p < 0.001). Our data suggest that hemoglobin had positive effect in the production of hemolytic factor and gene expression related to iron uptake in C. tropicalis.

Changes in the hemolytic activity of Candida species by common electrolytes

Background

Hemolysins are crucial virulence factors which help pathogens to survive and persist in the host. This study investigated whether common electrolytes will affect the hemolysins of Candida species. The hemolysins from 25 Candida isolates were investigated using a plate specially designed for Candida species in the presence of three electrolytes, CaCl₂, NaCl and KCl, at different concentrations. The hemolytic activity was determined after 48 h and the hemolytic index was calculated.

Results

All three electrolytes caused a decrease in the hemolytic activity. Significant differences existed between varying concentrations of NaCl, while no significant differences existed for the CaCl₂ and KCl groups. Additionally, the peripheral hemolytic index was highly correlated with the hemolytic index (r = 0.656, p < 0.001).

Conclusions

Our findings indicate that electrolytes reduce hemolysis by Candida species and a correlation exists between the peripheral hemolytic index and the translucent hemolytic index.

Hemolytic activity of dermatophytes species isolated from clinical specimens

Hemolytic activity was recently reported for several pathogenic fungal species, such as Aspergillus, Candida, Trichophyton, Penicillium and Fusarium. Based on a number of mechanistic and characterization studies, several fungal hemolysins have been proposed as virulence factors. Hemolysins lyse red blood cells resulting in the release of iron, an important growth factor for microbes especially during infection. The requirement of iron in fungal growth is necessary for metabolic processes and as a catalyst for various biochemical processes. Expression of a hemolytic protein with capabilities to lyse red blood cells has also been suggested to provide a survival strategy for fungi during opportunistic infections. The aims of this study were to investigate the hemolytic activities of dermatophytes species isolated from patients with dermatophytosis. Hair, skin and nail samples of patients were examined with direct microscopy using potassium hydroxide and cultivated on Mycobiotic agar and Sabouraud's dextrose agar. To determine hemolytic activities of dermatophytes species, they were subcultured on Columbia Agar with 5% sheep blood and incubated for 7-14 days at 25°C in aerobic conditions. Media which displayed hemolysis were further incubated for 1-5 days at 37°C to increase hemolytic activity. In this study, 66 dermatophytes strains were isolated from clinical specimens and were identified by six different species: 43 (65.1%) Trichophyton rubrum, 7 (10.7%) Trichophyton mentagrophytes, 5 (7.6%) Microsporum canis, 5 (7.6%) Trichophyton tonsurans, 4 (6.0%) Epidermophyton floccosum and 2 (3.0%) Trichophyton violaceum. Twenty-one T. rubrum strains showed incomplete (alpha) hemolysis and nine T. rubrum strains showed complete (beta) hemolysis, whereas hemolysis was absent in 13 T. rubrum strains. Four T. mentagrophytes strains showed complete hemolysis and three T. tonsurans strains showed incomplete hemolysis. However, M. canis, E. floccosum and T. violaceum species had no hemolytic activity. Hemolytic activity is pronounced in dermatophytes and may play an important role as a virulence factor. Hemolysins produced may play an important role in the balance between the host's cellular immunity and the ability of the fungus to diminish the immune response.

Hemolytic factor production by clinical isolates of Candida species

Most cases of fungal bloodstream infections (BIs) are attributed to Candida albicans; however, non-Candida albicans Candida species have recently been identified as common pathogens. Although hemolytic factor is known to be putative virulence factor contributing to pathogenicity in Candida species, its production is poorly evaluated. The present study was undertaken to analyze the production of hemolytic factor by C. albicans (10), C. tropicalis (13), and C. parapsilosis (8) isolates associated with BIs. Data of hemolysis zones on plate assay revealed that the majority of C. albicans isolates produced mild hemolytic activity whereas the majority of C. tropicalis produced strong activity. None of the tested C. parapsilosis isolates exhibited hemolysis on plate assay. We also evaluated the hemolytic activity in the cell-free broth. There were no significant differences (P > 0.05) in the secreted hemolytic activity among intra-species isolates. Different levels of secreted hemolytic factor were observed for Candida species, where C. tropicalis exhibited the highest production of hemolytic factor (P < 0.05) followed by C. albicans and C. parapsilosis. Inhibition of hemolysis (up to 89.12 %) from culture supernatant, following incubation with the lectin Concanavalin A (Con A), was observed for all three Candida species. This finding suggests that the secreted hemolytic factor of C. tropicalis and C. parapsilosis may be a mannoprotein, similar to that described for C. albicans.

Phospholipase, esterase and hemolytic activities of Candida spp. isolated from onychomycosis and oral lichen planus lesions

OBJECTIVE OF THE STUDY

Candidiasis is an opportunistic fungal infection caused by many species of Candida that affects different sites of the body. Secretion of exoenzymes plays an important role in virulence and pathogenesis. The aim of this study was to evaluate the potential role of phospholipase, esterase and hemolytic activity of Candida species isolated from onychomycosis and oral lichen planus patients in candidiasis.

METHODS

A total of 84 Candida isolates including 24 C. albicans and 46 C. parapsilosis from onychomycosis, and 14 C. albicans from oral lichen planus patients were 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. Statistical analyses were performed using the Fischer exact test.

RESULTS

C. parapsilosis isolates had the least exoenzyme activity among the isolates (P≤0.001). C. albicans isolates from lichen planus showed less exoenzyme activity in comparison to the onychomycosis isolates. Only 16.08% of C. parapsilosis isolates had phospholipase activity. This difference between C. albicans and C. parapsilosis was statistically significant (P≤0.001). All of the C. albicans isolates from onychomycosis patients had beta hemolysin activity. There was more hemolytic activity in the C. albicans isolates when compared with C. parapsilosis and between C. albicans isolates, no significant difference was seen. All of the C. albicans isolates produced esterase enzyme on day three and no significant differences were seen between the two groups of C. albicans for esterase activity. Two strains of C. albicans had no phospholipase or esterase activity.

CONCLUSION

This study showed that most of the isolates tested had different enzymatic patterns and C. parapsilosis strains had less phospholipase activity.

Production of haemolytic factor by clinical isolates of Candida tropicalis

Although haemolytic factor is known to be a putative virulence factor contributing to pathogenicity in Candida species, its production by Candida tropicalis is poorly understood. In this study, we analysed the culture conditions under which C. tropicalis can display haemolytic factor on plate assay and the secretion of haemolytic factor in liquid medium by clinical isolates obtained from different specimens. All the tested isolates exhibited an internal translucent ring, resembling beta-haemolysis, surrounding by a peripheral greenish-grey halo on sheep blood agar medium. Similar haemolytic pattern was observed on human blood enriched medium. Furthermore, incubation either under normal atmosphere or under increased CO(2) had no effect on haemolysis. Overall, no differences were observed on beta-haemolytic activities (P > 0.05) among tested isolates of C. tropicalis. In glucose-limited medium (RPMI 1640 with 0.2% glucose), none of the isolates induced haemolysis on red blood cells. Similarly to found on plate assays, there were no significant differences (P > 0.05) in the activity of secreted haemolytic factor in liquid medium among C. tropicalis isolates. However, after growth, the number of yeast cells varied among isolates revealing different efficiencies of haemolytic factor production. Haemolytic activity was neither inhibited by heat treatment (100 °C) nor by the addition of pepstatin A. The obtained results extend our knowledge about haemolytic factor production by Candida species.

Haemolytic and proteinase activities in clinical isolates of Candida parapsilosis and Candida tropicalis with reference to the isolation anatomic site

The aim of this study was to determine in vitro haemolytic and protease activities of Candida parapsilosis and Candida tropicalis isolates, obtained from anatomically distinct sites. Analysis of haemolytic activity of C. parapsilosis and C. tropicalis isolates obtained from the same anatomic site revealed that C. tropicalis isolates from blood had statistically higher activity (P < 0.05) than C. parapsilosis. On comparison of haemolytic activities of Candida isolates obtained from different anatomic sites, C. parapsilosis isolates from tracheal secretion were found to have higher activity than blood isolates. Protease activity was detected in the majority of the isolates analysed. Analysis of proteinase activity of C. parapsilosis and C. tropicalis isolates obtained from the same anatomic site revealed that C. parapsilosis isolates from tracheal secretion had statistically higher activity than C. tropicalis isolates. On comparison of proteinase activities of Candida isolates obtained from different anatomic sites, C. parapsilosis isolates from tracheal secretion were found to have higher activity than blood and superficial lesions isolates. Furthermore, C. tropicalis isolates from superficial lesions had higher activity than tracheal secretion isolates. Our results show the potential of C. parapsilosis and C. tropicalis isolates, obtained from distinct anatomic sites, to produce haemolytic factor and proteinases. Anatomic sites of isolation seem to be correlated with these activities, particularly for C. parapsilosis isolates.