The Gut Microbiome as a Major Regulator of the Gut-Skin Axis

The adult intestine hosts a myriad of diverse bacterial species that reside mostly in the lower gut maintaining a symbiosis with the human habitat. In the current review, we describe the neoteric advancement in our comprehension of how the gut microbiota communicates with the skin as one of the main regulators in the gut-skin axis. We attempted to explore how this potential link affects skin differentiation and keratinization, its influence on modulating the cutaneous immune response in various diseases, and finally how to take advantage of this communication in the control of different skin conditions.

In vitro antifungal activity of ME1111, a new topical agent for onychomycosis, against clinical isolates of dermatophytes

The treatment of onychomycosis has improved considerably over the past several decades following the introduction of the oral antifungals terbinafine and itraconazole. However, these oral agents suffer from certain disadvantages, including drug interactions and potential liver toxicity. Thus, there is a need for new topical agents that are effective against onychomycosis. ME1111 is a novel selective inhibitor of succinate dehydrogenase (complex II) of dermatophyte species, whose small molecular weight enhances its ability to penetrate the nail plate. In this study, we determined the antifungal activity of ME1111 against dermatophyte strains, most of which are known to cause nail infections, as measured by the MIC (n = 400) and the minimum fungicidal concentration (MFC) (n = 300). Additionally, we examined the potential for resistance development in dermatophytes (n = 4) following repeated exposure to ME1111. Our data show that the MIC90 of ME1111 against dermatophyte strains was 0.25 μg/ml, which was equivalent to that of the comparators amorolfine and ciclopirox (0.25 and 0.5 μg/ml, respectively). ME1111 was fungicidal at clinically achievable concentrations against dermatophytes, and its MFC90s against Trichophyton rubrum and Trichophyton mentagrophytes were 8 μg/ml, comparable to those of ciclopirox. Furthermore, ME1111, as well as ciclopirox, did not induce resistance in 4 dermatophytes tested. Our studies show that ME1111 possesses potent antifungal activity and suggest that it has low potential for the development of resistance in dermatophytes.

Role of oral candidiasis in TB and HIV co-infection: AIDS Clinical Trial Group Protocol A5253

OBJECTIVE

To evaluate the association between oral candidiasis and tuberculosis (TB) in human immunodeficiency virus (HIV) infected individuals in sub-Saharan Africa, and to investigate oral candidiasis as a potential tool for TB case finding.

METHODS

Protocol A5253 was a cross-sectional study designed to improve the diagnosis of pulmonary TB in HIV-infected adults in high TB prevalence countries. Participants received an oral examination to detect oral candidiasis. We estimated the association between TB disease and oral candidiasis using logistic regression, and sensitivity, specificity and predictive values.

RESULTS

Of 454 participants with TB culture results enrolled in African sites, the median age was 33 years, 71% were female and the median CD4 count was 257 cells/mm(3). Fifty-four (12%) had TB disease; the prevalence of oral candidiasis was significantly higher among TB cases (35%) than among non-TB cases (16%, P < 0.001). The odds of having TB was 2.4 times higher among those with oral candidiasis when controlling for CD4 count and antifungals (95%CI 1.2-4.7, P = 0.01). The sensitivity of oral candidiasis as a predictor of TB was 35% (95%CI 22-48) and the specificity 85% (95%CI 81-88).

CONCLUSION

We found a strong association between oral candidiasis and TB disease, independent of CD4 count, suggesting that in resource-limited settings, oral candidiasis may provide clinical evidence for increased risk of TB and contribute to TB case finding.

Optimization of an infected shoe model for the evaluation of an ultraviolet shoe sanitizer device

BACKGROUND

Onychomycosis and tinea pedis (athlete's foot) are infections of the nails and skin caused by pathogenic fungi collectively known as dermatophytes. These infections are difficult to treat, and patients often relapse; it is thought that a patient's footwear becomes infected with these fungal organisms and, thus, is an important reservoir for reinfection. Therefore, it is important to find an effective means for killing the dermatophytes that may have colonized the inner surface of the shoes of patients with superficial fungal infections. In this study, we developed an in vitro model for culturing dermatophytes in footwear and used this model to evaluate the effectiveness of a commercial ultraviolet shoe sanitizer in eradicating the fungal elements residing in shoes.

METHODS

Leather and athletic shoes (24 pairs) were inoculated with either Trichophyton rubrum or Trichophyton mentagrophytes (10(7) colony-forming units/mL) strains and were placed at 35°C for 4 to 5 days. Next, we compared the ability of swabbing versus scraping to collect microorganisms from infected shoes. Following the optimized method, shoes were infected and were irradiated with one to three cycles of radiation. The inner surfaces of the shoes were swabbed or scraped, and the specimens were cultured for dermatophyte colony-forming units.

RESULTS

Leather and canvas shoes were infected to the same extent. Moreover, scraping with a scalpel was overall more effective than was swabbing with a cotton-tipped applicator in recovering viable fungal elements. Irradiation of shoes with one, two, or three cycles resulted in reduction of fungal colonization to the same extent.

CONCLUSIONS

The developed infected shoe model is useful for assessing the effectiveness of ultraviolet shoe sanitizers. Also, ultraviolet treatment of shoes with a commercial ultraviolet C sanitizing device was effective in reducing the fungal burden in shoes. These findings have implications regarding breaking foot infection cycles.

Repeated exposure of Candida spp. to miconazole demonstrates no development of resistance

Oropharyngeal candidiasis (OPC) is a common infection among the immuno-compromised population. Treatments include both systemic azoles, most commonly fluconazole (FLU), and topical agents such as miconazole (MICON). However, resistance to FLU has been reported with a greater frequency. The aim of this study was to determine the potential for development of resistance following repeated exposure of Candida spp. to MICON. Two clinical isolates each of Candida albicans, C. glabrata, and C. tropicalis were tested. Fifteen passages of each strain were performed in concentrations of MICON at 0.5 minimum inhibitory concentration (MIC), 1 MIC, 2 MIC and 4 MIC, with MIC determinations performed on growth obtained following each passage. There was no increase in the MIC of four of the six strains following fifteen passages in MICON. One C. albicans strain demonstrated a four-five dilution increase in MICON MIC at all concentrations and one C. glabrata strain showed a fivefold MICON MIC increase when exposed to 4 MIC. Although an increase in MIC was noted in these two isolates, the MICON MIC was still very low (0.5 μg ml(-1)). In general, there was no increase in MIC demonstrated by repeated exposure to MICON in this study.

Antifungal activity of miconazole against recent Candida strains

Miconazole (MICON) has long been used for the topical treatment of mucosal candidiasis. However, the preponderance of MICON susceptibility data was generated before standard methodology was established, and prior to the emergence of fluconazole (FLU)-resistant strains. The objective of this study was to determine the antifungal activity of MICON and comparators against recent clinical isolates of Candida spp. using standard Clinical and Laboratory Standards Institute methodology. One hundred and fifty isolates, consisting of 25 strains each of Candida albicans, C. krusei, C. glabrata, C. tropicalis, C. parapsilosis and C. dubliniensis, were tested. Of these, twenty-two strains were known to be FLU-resistant. Minimum inhibitory concentrations (MICs) were determined for MICON, amphotericin B (AM), caspofungin (CAS), clotrimazole (CLOT), FLU, itraconazole (ITRA), nystatin (NYS) and voriconazole (VOR). MICON demonstrated potent inhibitory activity against all of the strains tested. The MIC(90) for MICON was 0.12 microg ml(-1) against FLU-susceptible strains, which was comparable to that of AM, CAS, CLOT, ITRA and VOR. The MICON MIC(90) against FLU-resistant strains was 0.5 microg ml(-1), which was 12-fold lower than the FLU MIC(90). Our study showed that MICON possesses potent activity against all of the Candida isolates tested, including those with known FLU resistance. This indicates that recent clinical isolates remain susceptible to this antifungal and that MICON could be used as first-line treatment for oropharyngeal candidiasis.

Comparison of the in vitro activity of terbinafine and lanoconazole against dermatophytes

The objective of this study was to compare the antifungal activity of terbinafine (TERB) with that of lanoconazole (LAN). Test isolates, which were clinical isolates of Japanese origin, included 10 strains each of Trichophyton rubrum, T. mentagrophytes and Epidermophyton floccosum. The minimum inhibitory concentration (MIC) of TERB and LAN against each dermatophyte isolate was determined according to the Clinical and Laboratory Standards Institute microbroth methodology, M38-A2. Minimum fungicidal concentrations were determined by subculturing the contents of each visibly clear well from the MIC assay for colony count. All LAN MICs were <or=0.008 microg ml(-1), while the TERB range was 0.008-0.03 microg ml(-1). Moreover, by standard definition, LAN was fungistatic against most strains, whereas TERB was fungicidal. Both LAN and TERB demonstrated potent antifungal activity against dermatophytes; however, the lack of fungicidal activity by LAN needs to be evaluated in terms of potential clinical efficacy.

Voriconazole susceptibilities of dermatophyte isolates obtained from a worldwide tinea capitis clinical trial

In this study, the voriconazole susceptibilities of dermatophyte isolates obtained from a worldwide tinea capitis trial were compared to their susceptibilities to fluconazole and griseofulvin. The MIC ranges of voriconazole, fluconazole, and griseofulvin, were 0.002 to 0.06 microg/ml, 0.25 to 32 microg/ml, and 0.125 to 2.0 microg/ml, respectively.

Determination of MICs of aminocandin for Candida spp. and filamentous fungi

Candida and Aspergillus spp., as well as other filamentous molds, have increasingly been reported as the causes of severe invasive fungal infections. We evaluated the new echinocandin aminocandin (AMN) for its antifungal activities against a range of fungal pathogens by determination of the MICs for the organisms. The MICs of the comparator drugs amphotericin B, caspofungin, micafungin, and voriconazole were also determined. The MICs of AMN for 25 strains each of non-Candida albicans Candida spp. (including Candida parapsilosis, Candida krusei, Candida guilliermondii, and Candida tropicalis), Aspergillus fumigatus, Scedosporium spp., Fusarium spp., and zygomycetes (including Absidia, Mucor, and Rhizopus spp.) were determined by using the Clinical and Laboratory Standards Institute M27-A2 and M38-A methodologies for yeasts and filamentous molds, respectively. The MIC ranges of AMN for all yeasts were similar (0.03 to 4.0 microg/ml), while the MIC ranges of AMN for filamentous fungi were species specific. AMN demonstrated potent antifungal activity against A. fumigatus, limited activity against Scedosporium spp., and no activity against zygomycetes or Fusarium spp. Our data showed that AMN demonstrated potent antifungal activities against all of the yeasts and Aspergillus isolates tested, suggesting that AMN could be an important addition to our arsenal of antifungals for the treatment of invasive fungal disease.

Synergistic antimicrobial activity by combining an allylamine with benzoyl peroxide with expanded coverage against yeast and bacterial species

BACKGROUND

Dermatophyte infections can be polymicrobial. Topical antifungal therapies offer limited coverage of yeasts and Gram-positive and Gram-negative bacteria. Moreover, the increased usage of these topical antimicrobial agents has resulted in the development of resistant cases. Benzoyl peroxide (BP), used in concert with antimicrobial agents containing an accessible tertiary amine, has previously been shown to increase radical activity and biological effect.

OBJECTIVES

To determine the applicability of using the tertiary amine terbinafine in concert with BP in dermatophyte and mixed skin infections by means of in vitro testing.

METHODS

In this preliminary in vitro study, the effect of BP, alone and in combination with terbinafine, was tested against Candida albicans, Pseudomonas aeruginosa and Staphylococcus aureus isolates following a checkerboard modification of the National Committee for Clinical Laboratory Standards M27-A2 and M7-A6. The individual minimum inhibitory concentrations of terbinafine, BP, and the combination, were determined against each isolate.

RESULTS

The combination of BP with terbinafine led to additive activities against the majority of Candida albicans isolates tested and additionally expanded the bacterial coverage of terbinafine.

CONCLUSIONS

The combination of antifungal agents bearing a tertiary amine with BP may have benefit in polymicrobial infections, given its wider antimicrobial coverage. Further appreciation of this mechanism of catalysis of BP radical formation by certain antimicrobials and other tertiary amine-containing compounds may lead to the discovery of improved treatments for several dermatological conditions.

Tinea capitis in Cleveland: survey of elementary school students

BACKGROUND

Tinea capitis, a fungal infection of the scalp, is of increasing public health importance, and Trichophyton tonsurans has become the primary causative agent in North America.

OBJECTIVES

To determine the prevalence of dermatophyte-positive scalp cultures among elementary schoolchildren in Cleveland, Ohio, describe predisposing factors, and measure the antifungal susceptibility of isolates collected.

OBSERVATIONS

A total of 937 children from 8 Cleveland elementary schools were cultured for the presence of dermatophytes; 122 children (13%), all of whom were African American, had dermatophyte-positive cultures of the scalp. Sixty percent of cases were asymptomatic, indicating a carrier state. Race, scaling, and the use of anti-dandruff shampoo were associated with increased likelihood of infection. T tonsurans was the only organism isolated (except 1 Microsporum canis isolate). All isolates were susceptible to fluconazole, griseofulvin, itraconazole, and terbinafine.

CONCLUSIONS

T tonsurans was the predominant dermatophyte isolated. Further multicenter studies are needed to confirm the predominance of dermatophyte-positive scalp cultures among African American children and to determine modifiable and preventable risk factors.

Clinical Trichophyton rubrum strain exhibiting primary resistance to terbinafine

The in vitro antifungal susceptibilities of six clinical Trichophyton rubrum isolates obtained sequentially from a single onychomycosis patient who failed oral terbinafine therapy (250 mg/day for 24 weeks) were determined by broth microdilution and macrodilution methodologies. Strain relatedness was examined by random amplified polymorphic DNA (RAPD) analyses. Data obtained from both broth micro- and macrodilution assays were in agreement and revealed that the six clinical isolates had greatly reduced susceptibilities to terbinafine. The MICs of terbinafine for these strains were >4 microg/ml, whereas they were <0.0002 microg/ml for the susceptible reference strains. Consistent with these findings, the minimum fungicidal concentrations (MFCs) of terbinafine for all six strains were >128 microg/ml, whereas they were 0.0002 microg/ml for the reference strain. The MIC of terbinafine for the baseline strain (cultured at the initial screening visit and before therapy was started) was already 4,000-fold higher than normal, suggesting that this is a case of primary resistance to terbinafine. The results obtained by the broth macrodilution procedure revealed that the terbinafine MICs and MFCs for sequential isolates apparently increased during the course of therapy. RAPD analyses did not reveal any differences between the isolates. The terbinafine-resistant isolates exhibited normal susceptibilities to clinically available antimycotics including itraconazole, fluconazole, and griseofulvin. However, these isolates were fully cross resistant to several other known squalene epoxidase inhibitors, including naftifine, butenafine, tolnaftate, and tolciclate, suggesting a target-specific mechanism of resistance. This is the first confirmed report of terbinafine resistance in dermatophytes.

A large-scale North American study of fungal isolates from nails: the frequency of onychomycosis, fungal distribution, and antifungal susceptibility patterns

BACKGROUND

Onychomycosis, a fungal infection of the nail bed, is responsible for up to 50% of nail disorders. Although several surveys have been conducted in different parts of the world, there have been no multicenter epidemiologic surveys of onychomycosis in North America.

OBJECTIVE

A 12-center study was undertaken to (1) determine the frequency of onychomycosis, (2) identify organisms recovered from the nails, and (3) determine the antifungal susceptibility of isolates.

METHODS

A total of 1832 subjects participated in this study and completed a comprehensive questionnaire, and nail clippings were collected for potassium hydroxide examination and culturing.

RESULTS

The frequency of onychomycosis, as defined by the presence of septate hyphae on direct microscopy and/or the recovery of a dermatophyte, was found to be 13.8%. In general, the dermatophyte isolates were susceptible to the antifungals tested.

CONCLUSION

Because of the limited number of large-scale studies, the baseline incidence is not firmly established. However, the higher frequency of onychomycosis in this study may confirm the suspected increase in incidence of disease in North America.

Antifungal susceptibilities and genetic relatedness of serial Trichophyton rubrum isolates from patients with onychomycosis of the toenail

Onychomycosis is a common fungal disease infecting up to 20% of the population over age 40. The major causative agent of onychomycosis is Trichophyton rubrum. Uncontrolled infection may eventually lead to penetration of the newly forming nail plate. In spite of the encouraging cure rate with recent antifungal agents such as the allylamines (terbinafine) and azoles (itraconazole and fluconazole) some patients inevitably fail therapy. In this investigation, a group of patients from a multi-center study designed to assess the efficacy of terbinafine with known cases of onychomycosis were selected for evaluation. Nail samples from this patient group were colonized with T. rubrum throughout the terbinafine therapy. Antifungal susceptibility testing was performed on these T. rubrum isolates to detect change in MIC values. Strain relatedness was examined using random amplified polymorphic DNA (RAPD) technique. Our results revealed failure of patients to clear T. rubrum is not related to the development of resistance to the drug. While species determination was possible, we were not able to identify differences that would indicate reinfection with a new strain. Analysis of patient demographic data revealed that 70% of patients were over 45 years old, 56.6% were previously treated with antifungals, 60% came from family history with onychomycosis and 13% were diabetic. In conclusion, our data indicate that patients' failure to clear onychomycosis was not associated with resistant development. Failure of terbinafine therapy may be dependent on host-related factors.

Antifungal susceptibility testing of dermatophytes: establishing a medium for inducing conidial growth and evaluation of susceptibility of clinical isolates

A standardized reference method for dermatophyte in vitro susceptibility testing is lacking. In a previous study, Norris et al. (H. A. Norris, B. E. Elewski, and M. A. Ghannoum, J. Am. Acad. Dermatol. 40(6, part 2):S9-S13) established the optimal medium and other growth variables. However, the earlier study did not address two issues: (i) selection of an optimal medium for conidial formation by dermatophytes and (ii) validation of the method with a large number of dermatophytes. The present study addresses these two points. To select which agar medium best supported conidial growth, representative isolates of dermatophytes were grown on different agars. Preliminary experiments showed that only oatmeal cereal agar supported the production of conidia by Trichophyton rubrum. We tested the abilities of 251 T. rubrum isolates to form conidia using three different cereal agars and potato dextrose agar. Overall, oatmeal cereal and rice agar media were comparable in their abilities to support T. rubrum conidial growth. Next, we used the oatmeal cereal agar for conidial formation along with the optimal conditions for dermatophyte susceptibility testing proposed by Norris et al. and determined the antifungal susceptibilities of 217 dermatophytes to fluconazole, griseofulvin, itraconazole, and terbinafine. Relative to the other agents tested, terbinafine possessed the highest antifungal activity against all of the dermatophytes. The mean +/- standard error of the mean MICs of fluconazole, itraconazole, terbinafine, and griseofulvin were 2.07 +/- 0.29, 0.13 +/- 0.01, 0.002 +/- 0.0003, and 0.71 +/- 0.05 microgram/ml, respectively. This study is the first step in the identification of optimal conditions that could be used for the standardization of the antifungal susceptibility testing method for dermatophytes. Inter- and intralaboratory agreement as well as clinical correlations need to be established.