Haemolytic activities of Trichophyton species

Population differentiation, antifungal susceptibility, and host range of Trichophyton mentagrophytes isolates causing recalcitrant infections in humans and animals

The major problems in determining the causative factors of the high prevalence of dermatophytoses include the lack of a well-standardized antifungal susceptibility testing method, the low consistency of in vitro and clinical minimal inhibitory concentration values, the high genomic diversity of the population, and the unclear mechanism of pathogenicity. These factors are of particular importance when the disease is recalcitrant and relapses. Herein, we identified and characterized Trichophyton mentagrophytes isolates obtained from therapy-resistant cases in humans and animals. We used genomic diversity analysis of 17 human and 27 animal clinical isolates with the MP-PCR technique, determined their phenotypic enzymatic activity and host range, and performed antifungal susceptibility testing to currently available antifungal drugs from various chemical groups. Genomic diversity values of 35.3% and 33.3% were obtained for clinical isolates from humans and animals, respectively, yet without any relationship to the host species or antifungal drug to which resistance in therapy was revealed. The highest activity of keratinase enzymes was recorded for fox, guinea pig, and human hairs. These hosts can be considered as the main species in the host range of these isolates. A phenyl morpholine derivative, i.e. amorolfine, exhibited superior activity against strains obtained from both humans and animals with the lowest MIC₅₀. Interestingly, high compliance of terbinafine in vitro resistance with clinical problems in the treatment with this substance was shown as well. The high resistance of dermatophytes to drugs is the main cause of the recalcitrance of the infection, whereas the other features of the fungus are less important.

Partial characteristics of hemolytic factors secreted from airborne Aspergillus and Penicillium, and an enhancement of hemolysis by Aspergillus micronesiensis CAMP-like factor via Staphylococcus aureus-sphingomyelinase

One of the advantages for initial survival of inhaled fungal spores in the respiratory tract is the ability for iron acquisition via hemolytic factor-production. To examine the ability of indoor Aspergillus and Penicillium affecting hemolysis, the secreted factors during the growth of thirteen strains from eight species were characterized in vitro for their hemolytic activity (HA) and CAMP-like reaction. The hemolytic index of HA on human blood agar of Aspergillus micronesiensis, Aspergillus wentii, Aspergillus westerdijkiae, Penicillium citrinum, Penicillium copticola, Penicillium paxilli, Penicillium steckii, and Penicillium sumatrense were 1.72 ± 0.34, 1.61 ± 0.41, 1.69 ± 0.16, 1.58 ± 0.46, 3.10 ± 0.51, 1.22 ± 0.19, 2.55 ± 0.22, and 1.90 ± 0.14, respectively. The secreted factors of an Aspergillus wentii showed high HA when grown in undernourished broth at 25°C at an exponential phase and were heat sensitive. Its secreted proteins have an estimated relative molecular weight over 50 kDa. Whereas, the factors of Penicillium steckii were secreted in a similar condition at a late exponential phase but showed low HA and heat tolerance. In a CAMP-like test with sheep blood, the synergistic hemolytic reactions between most tested mold strains and Staphylococcus aureus were identified. Moreover, the enhancement of α-hemolysis of Staphylococcus aureus could occur through the interaction of Staphylococcus aureus-sphingomyelinase and CAMP-like factors secreted from Aspergillus micronesiensis. Further studies on the characterization of purified hemolytic- and CAMP-like-factors secreted from Aspergillus wentii and Aspergillus micronesiensis may lead to more understanding of their involvement of hemolysis and cytolysis for fungal survival prior to pathogenesis.

Secreted Hydrolytic and Haemolytic Activities of Malassezia Clinical Strains

Malassezia yeasts are opportunistic pathogens associated with a number of skin diseases in animals and humans. The free fatty acids released through these organisms' lipase and phospholipase activities trigger inflammation in the host; thus, these lipase and phospholipase activities are widely recognised as some of the most important factors in Malassezia pathogenesis. In this study, we sought to investigate and examine the relationship between these secreted hydrolytic activities and haemolytic activity in newly isolated Malassezia clinical strains. This characterisation was expected to elucidate pathogenicity of this fungus. We isolated 35 clinical strains of Malassezia spp.; the most frequently isolated species were M. sympodialis and M. furfur. Next, we analysed the hydrolytic activities of all of these clinical isolates; all of these strains (except for one M. dermatis isolate) showed detectable lipase and phospholipase activities against 4-nitrophenyl palmitate and L-α-phosphatidylcholine, dipalmitoyl, respectively. Most of the M. globosa isolates showed higher lipase activities than isolates of other Malassezia species. In terms of phospholipase activity, no significant difference was observed among species of Malassezia, although one isolate of M. globosa showed considerably higher phospholipase activity than the others. All tested strains also exhibited haemolytic activity, both as determined using 5% (v/v) sheep blood agar (halo assay) and by quantitative assay. Although all tested strains showed detectable haemolytic activity, we did not observe an apparent correlation between the secreted lipase and phospholipase activities and haemolytic activity. We infer that the haemolytic activities of Malassezia spp. are mediated by non-enzymatic factor(s) that are present in the secreted samples.

The host range of dermatophytes, it is at all possible? Phenotypic evaluation of the keratinolytic activity of Trichophyton verrucosum clinical isolates

Dermatophytes are fungi that have an ability to invade keratinised structures. Enzymes secreted by dermatophytes can underlie fungal survival on the host and development of infection. It is possible that the range of activity of keratinases from various dermatophytes is limited to specific species of animals and groups of people. The aim of this study was to carry out phenotypic analysis of the degree of keratinolytic activity of Trichophyton verrucosum strains using hairs of humans and various animal species as substrates. Our results indicated that the activity of keratinases is substrate-induced. The host range of T. verrucosum can be defined as wide. The highest activity of keratinases was recorded in media containing keratin from cow (Bos taurus) and sheep (Ovis aries) hairs in comparison with that from other tested species. The production of keratin-degrading enzymes is a function of time, with the peak of their activity occurring on day 15 of incubation. The role of keratin-degrading enzymes in the pathogenesis of dermatophytosis is becoming increasingly clearer. Given the conceptual understanding that keratin breakdown may require more than just one enzyme, the use of phenotypic methods is an optimal approach to in vitro study of the decomposition of species-specific keratin.

Enzymatic and Non-Enzymatic Virulence Activities of Dermatophytes on Solid Media

INTRODUCTION

Dermatophytes are keratinophilic fungi causing superficial cutaneous infections that account 20-25% of the global population. As per literature search, there is a dearth in the study on virulence factors of dermatophytes from the Indian sub-continent and moreover the association of the virulence factors and the host tissue in vitro helps in understanding the host-pathogen interaction.

AIM

To analyse the enzymatic and non-enzymatic virulence activities of dermatophytes on solid media.

MATERIALS AND METHODS

A total of 11 isolates, three standard American Type Culture Collection (ATCC) strains- Trichophyton rubrum- 28188, Trichophyton mentagrophytes- 9533, Trichophyton tonsurans- 28942, one CBS KNAW Fungal Biodiversity Centre strain- Arthroderma grubyi- 243.66, five clinical isolates- T. rubrum, T. mentagrophytes, Trichophyton rubrum var. raubitschekii, Trichophyton interdigitale, Epidermophyton floccosum, and two laboratory isolates - Microsporum gypseum and Microsporum canis were screened for the production of virulence enzymes such as phospholipase, lipase, protease, gelatinase and non-enzyme virulence factors (haemolytic activity) of dermatophytes. The clinical isolates were identified from a tertiary care hospital, Chennai. These dermatophytes were tested upon specific substrates on solid media such as egg yolk, tween 80, bovine serum albumin, gelatin powder and sheep blood respectively.

RESULTS

The virulence activity of phospholipase, lipase, protease and gelatinase was observed from all the dermatophyte species. T. rubrum, T. rubrum ATCC strain, T. rubrum var. raubitschekii, T. mentagrophytes, T. mentagrophytes ATCC strain, T. interdigitale and A. grubyi CBS strain produced complete haemolysis, whereas other dermatophytes showed no haemolytic activity.

CONCLUSION

Phospholipase, lipase, protease and gelatinase act as enzymatic virulence marker and the T. rubrum complex, T. mentagrophytes complex and A. grubyi showed complete haemolysis and hence they may also act as a non-enzymatic virulence marker for dermatophytes.

Proteolytic activity and cooperative hemolytic effect of dermatophytes with different species of bacteria

BACKGROUND AND PURPOSE

Globally, dermatophytes are the most common filamentous group of fungi causing cutaneous mycoses. Dermatophytes were shown to secrete a multitude of enzymes that play a role in their pathogenesis. There is limited data on co-hemolytic (CAMP-like) effect of different bacterial species on dermatophyte species. In this study, we sought to the evaluate exoenzyme activity and co-hemolytic effect of four bacteria on clinical dermatophytes isolated from patients in Shiraz, Iran.

MATERIALS AND METHODS

A total of 84 clinical dermatophyte species were isolated from patients suffering dermatophytosis and identified by conventional methods. Hemolytic activity was evaluated with Columbia 5% sheep blood agar. Proteolytic activity was determined by plate clearance assay method, using gelatin 8% agar. CAMP-like factor was evaluated with four bacteria, namely, S. areus, S.saprophyticus, S.pyogenes, and S.agalactiae. Fisher's exact test was run for statistical analysis.

RESULTS

T. mentagrophytes was the most predominant agent (27 [32.1%]) followed by T. verrucosum(20 [23.8%]), T. tonsurans (10 [11.9%]), Microsporum canis (7 [8.3%]), T. rubrum (6 [7.1%]), E. floccosum (6 [7.1%]), M. gypseum (5 [6%]), and T. violaceum (3[3.6%]). The most common clinical area of dermatophytosis was the skin. All the isolates expressed the zone of incomplete alpha hemolysis. All the isolates had CAMP- positive reaction with S. aureus and the other bacteria were CAMP-negative. All the isolates expressed proteolytic activity and no significant differences were noted among diverse genera of dermatophytes and severities of proteolytic activity.

CONCLUSION

This study indicated that hemolysin and proteolytic enzymes potentially play a role in dermatophyte pathogenesis and S. aureus could be considered as a main bacterium for creation of co-hemolytic effect in association with dermatophyte species.

Virulence markers of opportunistic black yeast in Exophiala

The black yeast genus Exophiala is known to cause a wide variety of diseases in severely ill individuals but can also affect immunocompetent individuals. Virulence markers and other physiological parameters were tested in eight clinical and 218 environmental strains, with a specific focus on human-dominated habitats for the latter. Urease and catalase were consistently present in all samples; four strains expressed proteinase and three strains expressed DNase, whereas none of the strains showed phospholipase, haemolysis, or co-haemolysis activities. Biofilm formation was identified in 30 (13.8%) of the environmental isolates, particularly in strains from dishwashers, and was noted in only two (25%) of the clinical strains. These results indicate that virulence factors are inconsistently present in the investigated Exophiala species, suggesting opportunism rather than pathogenicity.

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.

Fungal hemolysins

Hemolysins are a class of proteins defined by their ability to lyse red cells but have been described to exhibit pleiotropic functions. These proteins have been extensively studied in bacteria and more recently in fungi. Within the last decade, a number of studies have characterized fungal hemolysins and revealed a fascinating yet diverse group of proteins. The purpose of this review is to provide a synopsis of the known fungal hemolysins with an emphasis on those belonging to the aegerolysin protein family. New insight and perspective into fungal hemolysins in biotechnology and health are additionally presented.

Isolation and characterization of a haemolysin from Trichophyton mentagrophytes

Haemolytic activities of Trichophyton (T.) mentagrophytes were detected and characterized by qualitative and quantitative assays. On Columbia agar supplemented with blood from horses, cattle or sheep, T. mentagrophytes expressed a strong zone of complete haemolysis. No haemolytic activities could be detected in the closely related T. verrucosum var. ochraceum. The same results were obtained after cultivation of the fungi on sterile cellulose acetate filters placed on the surface on Columbia blood agar. After removal of the filter, complete haemolysis was detected below the colony of T. mentagrophytes. A soluble haemolysin from culture supernatant of this strain was isolated and partially purified. Specific haemolytic activity per mg protein was enriched 2.6-fold in filtrate F(1), a fraction obtained as filtrate after filtration through 3kDa cut-off membranes. The partially purified haemolysin was neither affected by proteinase K treatment, nor by high and low temperatures, suggesting that it represents a small peptide haemolysin. Accordingly, in a commercial enzymatic activity test only the crude culture filtrate, but none of the subsequent purification fractions showed reactivity. Evaluation of the specificity of the haemolysin using erythrocytes from different mammalian species revealed that sensitivity was highest to those of equines, followed by erythrocytes from sheep, cattle, swine, dogs and humans. None of the erythrocytes was lysed by filtrate F(1) from T. verrucosum var. ochraceum. Furthermore, different eukaryotic cell lines from different species were tested in their sensitivity to cytolytic activities of the haemolysin, but no membrane damage could be detected.

Deep dermatophytosis caused by Trichophyton rubrum: report of two cases

Two patients presenting with subcutaneous nodules, plaques, papules and ulceration caused by Trichophyton rubrum are described in this report. The first case was a 46-year-old woman referred with erythema and desquamation over her trunk, hands and feet for 30 years, progressing to nodules and ulceration over her trunk, arms and scalp for the last 2 years. The second case was a 34-year-old man who presented with a 2-year-history of itchy, erythema and desquamation over the trunk, progressing to papules, nodules and cyst around his ear, on the neck and scalp for 1 year. The diagnoses were suspected after direct microscopical examinations of the discharge materials, which revealed the presence of hyaline hyphae. The histological examinations showed granulomatous inflammatory infiltrates with fungal elements in the dermis including epithelioid cells, giant cells, lymphocytes and eosinophils, and the periodic acid-Schiff stain showed hypha within the granulomas. Cultures of puncture materials, skin biopsies and nails confirmed the diagnosis identifying T. rubrum. Antifungal therapies with itraconazole were successful in both patients, the lesions were completely clear with atrophic scars after 3 months. Side effects were not noticed during the medication. We discuss the clinical types of granulomatous cutaneous lesions caused by dermatophyte infections and evaluate the therapeutic effect of itraconazole.

Invasive dermatophytosis with lymph node involvement in an immunocompetent patient

A 23-year-old man presented with annular and arcuate, hyperpigmented, itchy, scaly plaques over the trunk and lower extremities for 5 years progressing to verrucous papules and nodules for the last 1.5 years. He also had nontender, inguinal and axillary lymphadenopathy. Skin and lymph node biopsies showed granulomatous inflammation and special stains demonstrated long septate hyphae. Tissue cultures grew Trichophyton verrucosum. The patient was treated with itraconazole 100 mg twice daily for 8 months, resulting in complete clearance of the lesions.

Dermatophytes can trigger cooperative (CAMP-like) haemolytic reactions

BACKGROUND

Dermatophytes usually grow on skin that is also colonized by bacteria. Therefore, a possible interaction between dermatophytes and bacteria is of potential relevance for the pathogenesis of skin infections. Cell membranes contribute substantially to epidermal barrier function. Erythrocyte haemolysis is a model commonly used to study membrane-damaging effects of microbial factors. Cooperative (CAMP-like) haemolytic reactions are known from distinct bacteria, but not from dermatophytes and bacteria.

OBJECTIVES

To investigate CAMP-like reactions of dermatophytes.

METHODS

Species of dermatophytes representing the genera Microsporum, Trichophyton and Epidermophyton, erythrocytes from sheep, horse and cattle, cultures of Staphylococcus aureus, S. intermedius, Listeria ivanovii, S. hyicus and S. epidermidis, and cell-free supernatants of bacterial cultures were used to search for cooperative haemolytic effects in in vitro agar diffusion assays.

RESULTS

A cooperative (CAMP-like) haemolytic reaction was identified for all dermatophytes tested. Using erythrocytes from sheep and cattle, pretreated with a sphingomyelinase from S. aureus, S. intermedius or L. ivanovii, the fungi induced a distinct zone of complete haemolysis on solid media and in a diffusion test. No CAMP reaction could be detected using S. hyicus or S. epidermidis as a first-step agent or with equine erythrocytes. The lytic reaction of the CAMP-cohaemolysin derived from dermatophytes was always separate from the zone of complete haemolysis, indicating two different cytolytic factors.

CONCLUSIONS

Our results show, for the first time, that in principle a CAMP-like effect can occur with dermatophtyes. This is a new observation of potential relevance for the pathogenesis of skin infections. The membrane-damaging factors released by dermatophytes should be further analysed.