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.

Onychomycosis: pathogenesis, diagnosis, and management

Although not life-threatening, onychomycosis (a fungal infection of the nail, usually caused by a dermatophyte) constitutes an important public health problem because of its high prevalence (about 10% of the U.S. population) and associated morbidity. The disease can have certain negative consequences for patients, such as pain, and can potentially undermine work and social lives. This review discusses the etiology, classification, diagnosis, and treatment of onychomycosis. Four types of onychomycosis are recognized based on the site and pattern of fungal invasion. Dermatophyte fungi are the predominant pathogens, but yeasts (especially Candida albicans) and nondermatophyte molds may also be implicated. Accurate diagnosis requires direct microscopy and fungal culture. The differential diagnosis includes psoriasis, lichen planus, onychogryphosis, and nail trauma. Onychomycosis is more difficult to treat than most dermatophytoses because of the inherent slow growth of the nail. Older antifungal agents (ketoconazole and griseofulvin) are unsuitable for onychomycosis because of their relatively poor efficacy and potential adverse effects. Three recently developed antimycotic agents (fluconazole, itraconazole, and terbinafine) offer high cure rates and good safety profiles. In addition, the short treatment times (< 3 months) and intermittent dosing schedules are likely to enhance compliance and reduce the costs of therapy.

Histological and bacteriological evaluation of digital dermatitis in cattle, with special reference to spirochaetes and Campylobacter faecalis

Tissue samples from the feet of slaughtered cattle exhibiting different stages of digital dermatitis were sectioned and stained with haematoxylin and eosin and silver staining techniques. Three morphological variations of spirochaetes were observed, whereas control samples from feet which were macroscopically negative for digital dermatitis were also negative for spirochaetes. In an immunofluorescence test, Campylobacter faecalis was found to be abundant on superficial wound smears from the classical ulceration of digital dermatitis.

Comparison of diagnostic methods in the evaluation of onychomycosis

BACKGROUND

Onychomycosis is a common problem seen in clinical practice. Given the differential diagnosis of dystrophic nails, it is helpful to obtain a definitive diagnosis of dermatophyte infection before the initiation of antifungal therapy. Potassium hydroxide (KOH) preparation and fungal culture, which are typically used in the diagnosis of these infections, often yield false-negative results. Recent reports have suggested that nail plate biopsy using periodic acid-Schiff (PAS) (Bx/PAS) stain may be a very sensitive technique for the diagnosis of onychomycosis.

OBJECTIVE

The purpose of this study was to compare KOH preparation, culture, Bx/PAS stain, and calcofluor white (CW) stain in the diagnosis of onychomycosis and to determine their sensitivity and specificity.

METHODS

We evaluated 105 patients with suspected onychomycosis using 4 diagnostic methods: KOH preparation, culture, Bx/PAS, and CW stain. CW stain binds to cellulose and chitin, and fluoresces when exposed to UV radiation. It is a highly sensitive and specific technique for the detection of dermatophytes. To determine the clinical usefulness and performance characteristics of each test, CW was chosen as the gold standard for statistical analysis.

RESULTS

Of the patients, 93 had at least 1 of the 4 diagnostic methods positive for the presence of organisms. The following were calculated for each test: sensitivity; specificity; positive predictive value; and negative predictive value. The sensitivities of each of the techniques were as follows: KOH 80%; Bx/PAS 92%; and culture 59%. Both KOH and Bx/PAS methods were more sensitive than culture (P =.00002). Bx/PAS was also more sensitive than KOH (P =.03). The specificities were as follows: KOH 72%; Bx/PAS 72%; and culture 82%. The positive predictive value calculated for the different techniques were: KOH 88%; Bx/PAS 89.7%; and culture 90%. In terms of negative predictive value, the results were: KOH 58%; Bx/PAS 77%; and culture 43%.

CONCLUSION

Bx/PAS is the most sensitive method for the diagnosis of onychomycosis. It is also superior to the other methods in its negative predictive value. It is indicated if other methods are negative and clinical suspicion is high, and potentially is the single method of choice for the evaluation of onychomycosis.

Onychomycosis, tinea pedis and tinea manuum caused by non-dermatophytic filamentous fungi

Over 4000 cases of fungal nail, sole and palm infection recorded during a three-year study period were investigated to determine the prevalence and significance of etiologic agents other than dermatophytes and yeasts. Littman's oxgall agar, which permitted isolation of cycloheximide-sensitive species but restricted overgrowth by fast growing contaminants, was used to promote isolation of these disease agents. Non-dermatophytic filamentous fungi made up 2.3% of the confirmed etiologic agents obtained overall, and constituted 3.3% of the agents obtained from nail infections. The most common species were Scopulariopsis brevicaulis, Hendersonula toruloidea, and Aspergillus sydowii. Scytalidium hyalinum was recorded for the first time from Canada, and an instance of nail infection by Gymnascella dankaliensis was recorded. Only H. toruloidea and Sc. hyalinum caused palm and sole infections.

Prevalence and epidemiology of unsuspected onychomycosis in patients visiting dermatologists' offices in Ontario, Canada--a multicenter survey of 2001 patients

BACKGROUND

Questionnaire studies have been used to determine the prevalence of onychomycosis in the United Kingdom and Europe. One disadvantage of this methodology is that the patient self-diagnoses the onychomycosis. There have been very few large studies involving clinical examination of the nails of subjects, followed by mycological confirmation of the onychomycosis. We therefore determined the prevalence of onychomycosis in patients visiting dermatologists' offices in Ontario, Canada.

METHODS

In a prospective, multicenter study, the finger- and toenails of all new patients presenting to dermatologists' offices were examined by a board-certified dermatologist. If there was clinical suspicion of onychomycosis, then nail samples were obtained for mycological examination at a central laboratory. Patients referred specifically for the management of onychomycosis were excluded.

RESULTS

Toenails appeared abnormal in 455 (22.7%) of 2001 patients. Mycologically-confirmed pedal onychomycosis was present in 182 (9.1%) of the 2001 patients. The estimated value of the prevalence of onychomycosis in Ontario is 6.86% (95% confidence interval (CI): 5.8-8.0%), when corrected for age and sex of the general population using census data. Onychomycosis increased with age (P < 0.0001). The odds of males having onychomycosis was 84.3% greater than females of the same age (P = 0.0003). The distribution of organisms in the 141 patients with pedal onychomycosis who were culture positive was: dermatophytes 131 (92.9%), Candida species 4 (2.8%) and non-dermatophyte molds 6 (4.3%).

CONCLUSIONS

The prevalence of mycologically-confirmed toenail onychomycosis was 9.1%, with the estimated prevalence in Ontario being 6.86%. The majority of patients with abnormal-appearing nails were unaware they might have onychomycosis, that it is infectious and potentially treatable, suggesting that there is potential for increased public awareness and education.

Long-term effectiveness of treatment with terbinafine vs itraconazole in onychomycosis: a 5-year blinded prospective follow-up study

OBJECTIVE

To examine long-term cure and relapse rates after treatment with continuous terbinafine and intermittent itraconazole in onychomycosis.

DESIGN

Long-term prospective follow-up study.

SETTING

Three centers in Iceland.

SUBJECTS

The study population comprised 151 patients aged 18 to 75 years with a clinical and mycological diagnosis of dermatophyte toenail onychomycosis.

INTERVENTIONS

In a double-blind, double-dummy study, patients were randomized to receive either terbinafine (250 mg/d) for 12 or 16 weeks or itraconazole (400 mg/d) for 1 week in every 4 for 12 or 16 weeks (first intervention). Patients who did not achieve clinical cure at month 18 or experienced relapse or reinfection were offered an additional course of terbinafine (second intervention).

MAIN OUTCOME MEASURES

The primary efficacy criterion was mycological cure, defined as negative results on microscopy and culture at the end of follow-up and no requirement of second intervention treatment. Secondary efficacy criteria included clinical cure without second intervention treatment and mycological and clinical relapse rates.

RESULTS

Median duration of follow-up was 54 months. At the end of the study, mycological cure without second intervention treatment was found in 34 (46%) of the 74 terbinafine-treated subjects and 10 (13%) of the 77 itraconazole-treated subjects (P<.001). Mycological and clinical relapse rates were significantly higher in itraconazole vs terbinafine-treated patients (53% vs 23% and 48% vs 21%, respectively). Of the 72 patients who received subsequent terbinafine treatment, 63 (88%) achieved mycological cure and 55 (76%) achieved clinical cure.

CONCLUSION

In the treatment of onychomycosis, continuous terbinafine provided superior long-term mycological and clinical efficacy and lower rates of mycological and clinical relapse compared with intermittent itraconazole.

Relapses of onychomycosis after successful treatment with systemic antifungals: a three-year follow-up

BACKGROUND

Data about relapses of onychomycosis after treatment with the new systemic antifungals vary among the different studies, with figures ranging from 3 to 20% for terbinafine and from 21 to 27% for itraconazole, depending on the follow-up duration.

OBJECTIVE

To determine the prevalence of relapses of onychomycosis cured by terbinafine compared with that of onychomycosis cured by itraconazole.

METHODS

We followed up 47 patients whose toenail onychomycosis had been mycologically cured in an open randomized study comparing intermittent itraconazole treatment with continuous terbinafine treatment and intermittent terbinafine therapy. Patients were examined every 3 months for up to 3 years after the end of therapy. At each visit clinical and mycologic (direct microscopy and cultures) evaluations were performed.

RESULTS

Eight of the 36 patients (22.2%) who completed the study had a relapse of onychomycosis during the follow-up period, including 2 patients of the terbinafine 250 mg group, 2 patients of the terbinafine 500 mg group and 4 patients in the itraconazole 400 mg group. As the original infection, the relapse was caused in all cases by Trichophyton rubrum.

CONCLUSIONS

This study shows that 22.2% of patients with onychomycosis successfully treated with systemic antifungals experienced a relapse. The relapse rate increased from 8. 3% at month 12 to 19.4% at month 24 and to 22.2% at month 36. Relapses were more common in patients treated with pulse itraconazole (4/11) than in patients treated with continuous (2/12) or intermittent (2/13) terbinafine. Statistical analysis did not reveal any significant difference between relapse rates in the three groups.

Mycology of nail disorders

Cases of onychomycosis represent up to 30% of diagnosed superficial fungal infections and are caused by three groups of fungi: dermatophytes, yeasts, and nondermatophytic molds. The majority of toenail infections are caused by dermatophytes; Trichophyton rubrum is isolated with the greatest frequency. In infections of fingernails, Candida species can be isolated as frequently as the dermatophytes. Of the molds, Scytalidium species can infect both fingernails and toenails, as well as adjacent skin, and represent 3% of the nail infections in a temperate country such as the United Kingdom but a much higher proportion in tropical countries. Other molds such as Scopulariopsis, Acremonium, and Aspergillus species can infect damaged nails. The isolation of a dermatophyte is always considered indicative of infection, but the presence of other molds, which may be aerial contaminants, must be interpreted with care.

Onychomycosis: a critical study of techniques and criteria for confirming the etiologic significance of nondermatophytes

Nondermatophytic filamentous fungi (NDF) other than Scytalidium species are variously said to cause between 0 and 50% of all toenail onychomycoses, though most estimates are in the 2-5% range. Due to the difficulty of obtaining 'gold standard' control data for comparison, the accuracy of many laboratory evaluation processes used to deal with potential NDF onychomycoses has never been rigorously measured, thus allowing use of differing interpretations of the significance of cultures. To allow valid comparison of these procedures and interpretations, a large series of patients who declined treatment were sampled on multiple occasions from all apparently onychomycotic toenails until adequate certainty had been attained that all etiologic agents had been isolated and, where necessary, confirmed as etiologic via consistent repeated isolation. This information was used to evaluate results that had been obtained in the initial direct microscopy and culture studies for the same patient population, as such results are strongly relied on in routine diagnosis. Direct microscopy (KOH) was found to be 73.8% sensitive for dermatophytes and 67.2% sensitive for proven etiologic NDF (difference not significant). Culture of the initial specimen coincidentally had a sensitivity of 74.6% for both fungal groups. KOH and culture in tandem were 83.9% sensitive for indicating fungal etiology based on the first specimen. Different evaluative frameworks currently used to interpret NDF isolations were contrasted. The 'classic' evaluation procedure, in which all NDF considered etiologic must be isolated from at least two successive nail specimens, at least one of which must be microscopic positive for compatible fungal filaments, had a sensitivity of 59.5% but a specificity of 100% for true NDF infections and mixed NDF/dermatophyte infections. The most widely used 'simple association' evaluation criterion, in which NDF outgrowth is considered etiologic whenever direct microscopy is positive for fungal elements and no dermatophyte grows out from the initial specimen, had a sensitivity of 53.6% and a specificity of 70.3% for NDF infections. A frequently criticized, but in some quarters still advocated, variant of the simple association criterion considers NDF outgrowth to be significant whenever the corresponding specimen is positive for fungal filaments in direct microscopy; application of this criterion yielded a sensitivity of 60.7% for true infections but a specificity of only 42%. With the aid of two standard notes soliciting repeat specimens, the classic criterion was able to attain 92.7% accuracy in recognizing all NDF etiologic agents and 100% accuracy in disregarding all contaminants from initial specimens that were positive in direct microscopy and yielded a filamentous fungus in initial culture. Even in exhaustive longitudinal study, only 20.2% of NDF infections were found to be associated with a concurrent dermatophytosis. In auxiliary studies, some nails remained NDF-infected after dermatophytes had been successfully eliminated by therapy.

A new classification of onychomycosis

This new classification of onychomycosis is a development of previous schemes and depends on the recognition of different clinical patterns of nail plate involvement associated with fungal infection as well as histopathology. The main types are distal and lateral subungual onychomycosis, superficial onychomycosis, proximal subungual onychomycosis, endonyx onychomycosis and total dystrophic onychomycosis. In addition, patients may show different combinations of these patterns. The identification of clinical patterns of disease may be useful in defining differences in clinical behaviour, treatment response and associated disease.

Onychomycosis in Denmark: prevalence of fungal nail infection in general practice

The study was initiated in order to get knowledge of the frequency of onychomycosis in patients visiting general practitioners in Denmark. A study design was using a display showing photos of abnormal nails including fungal infection, a clinical examination and a questionnaire. The practitioners obtained nail material. Direct microscopy and culture as well as histopathology, were carried out blindly in two different mycological laboratories. A number of 8546 patients were seen during the 6 months of the study, 5755 (67.3%) took part in the investigation. Clinical abnormal nails were observed in 948 (16.5%) patients, 52% males and 48% females, aged 18-92, mean 55 years old. Onychomycosis caused by dermatophytes were found in 238 (4.1%) and by Candida albicans in 45 (0.8%). Trichosporon cutaneum and Scopulariopsis brevicaulis were isolated each in 15 cases as single cultures. Onychomycosis, was typically seen in toenails as the distal-lateral type in males more than 40 years old. Predisposing factors were familiar dermatophytosis (22%), trauma (16.9%), diabetes mellitus (6.7%) and peripheral circulatory insufficiency (5.9%).

Effect of onychomycosis on quality of life

BACKGROUND

Onychomycosis impairs normal nail functions, causes considerable pain, interferes with daily activities, and has negative psychosocial effects.

OBJECTIVE

Our purpose was to determine patients' perception of onychomycosis on the quality of life.

METHODS

A total of 258 patients with confirmed onychomycosis were surveyed by telephone at three centers. Responses to a standardized quality-of-life questionnaire were analyzed for patient demographics, physical and functional impact, psychosocial impact, and economic impact.

RESULTS

Highest positive responses were nail-trimming problems (76%), embarrassment (74%), pain (48%), nail pressure (40%), and discomfort wearing shoes (38%). Ability to pick up small objects was impaired in 41% of subjects with fingernail involvement. More than 58 onychomycosis-related sick days and 468 medical visits (1.8 per subject) were reported during a 6-month period.

CONCLUSION

Onychomycosis has significant social, psychologic, health, and occupational effects. Relevance of quality-of-life issues to overall health, earning potential, and social functioning should prompt reconsideration of the value of aggressive treatment of and financial coverage for onychomycosis.

Toenail onychomycosis: current and future treatment options

Onychomycosis is a common disease affecting as much as 8% of the general population. Treatment of onychomycosis is challenging, complicated by low cure rates and relatively high relapse rates. This paper reviews the efficacy of current oral, topical, and surgical treatment options. Currently, the treatment of choice for toenail onychomycosis is oral terbinafine because of its high efficacy, low relapse rates, and cost-effectiveness. Oral itraconazole or fluconazole could be considered for infections caused by Candida. Topical therapies may be a useful adjunct to these systemic therapies, but are less effective when used alone. More research is needed to determine the best measures for preventing reinfection.

Onychomycosis and other superficial fungal infections of the foot in the elderly: a pan-European survey

BACKGROUND

The escalating ageing population in the western world has led to an increased incidence of superficial fungal infections. The most common infections include onychomycosis, tinea pedis and tinea cruris. With the increasing life expectancy, the prevalence of onychomycosis and other superficial fungal infections is likely to increase further without adequate prevention and treatment.

OBJECTIVE

To study the prevalence of foot mycoses in Europe.

METHOD

The Achilles project represents a survey of 90,085 subjects from 16 European countries.

RESULTS

Approximately half of the total screened population had evidence of fungal foot infection, with tinea pedis and onychomycosis affecting one quarter of these individuals. Advancing age showed an unfavourable effect on the prevalence of these infections.

CONCLUSION

As the number of aged people in developed countries continues to increase, skin diseases will constitute a greater pharmaco-economic concern of worldwide healthcare. Better recognition by clinicians and patients of mycotic foot disease will help prevent direct morbidity and further complications.

[Causative agents of onychomycosis--a retrospective study]

BACKGROUND

Dermatophytes, yeasts and moulds all are potential causative agents of onychomycosis. The aim of this study was to determine the percentage of cases of onychomycoses caused by each group. In addition, the responsible genus and species was identified for each nail infection.

PATIENTS AND METHODS

In a retrospective study performed at the Department of Dermatology of the Leipzig University, 5,077 nail samples from 4,177 patients--2,240 women and 1,937 men--with a variety of nail changes--not just onychomycosis--were investigated. 75% were toenails, 23% fingernails, and 2% from both sites.

RESULTS

Both microscopic and/or cultural detection of fungi (dermatophytes, yeasts and moulds) were successful in 54% of samples. Causative fungal agents were: 68% dermatophytes, 29% yeast, and 3% moulds. The most frequently detected dermatophyte species were T. rubrum (91%), and T. mentagrophytes (7.7%). Among yeasts, C. parapsilosis (42%) was most common,followed by C. guilliermondii (20.1%), C. albicans (14.2%), and Trichosporon spp. (10%). Scopulariopsis brevicaularis (43%) was the most frequent mould. The percentage of mixed fungal infections was 22%.

CONCLUSIONS

Dermatophytes, in particular T.rubrum, but also T. mentagrophytes, are the most frequently isolated causative agents in onychomycosis. In addition, yeasts may be isolated relatively frequently, while moulds are uncommon.

Fusarium spp. as agents of onychomycosis in immunocompetent hosts

BACKGROUND

Fusarium spp. are nondermatophyte filamentous fungi, frequently reported as an etiologic agent of opportunistic infections in humans; however, their involvement in the etiology of cutaneous lesions is still debatable, especially in immunocompetent patients, where they are often considered as contaminant fungi.

OBJECTIVE

The aims of this study were to report the high prevalence of onychomycosis by Fusarium spp. in immunocompetent patients in the region of Maringá, Paraná, Brazil, to establish clinical and laboratory criteria for this genus as a causal agent of onychomycosis, and to determine the susceptibility profile to the systemic antifungal drugs most frequently used in Brazil (itraconazole, ketoconazole, terbinafine, and amphotericin B).

METHODS

The fungi were isolated and identified through the classical method, and sensitivity tests were carried out according to the National Committee for Clinical Laboratory Standards (NCCLS) M38-A protocol.

RESULTS

Of the 360 confirmed cases of onychomycosis, 27 (7.5%) were attributed to the genus Fusarium, and F. oxysporum was the most commonly isolated species. Nail lesions with paronychia and pain, combined with direct suggestive microscopy and a high concentration of microorganisms, were predictive of onychomycosis by Fusarium spp. The minimum inhibitory concentration was high for itraconazole, ketoconazole, and terbinafine, but low for amphotericin B.

CONCLUSIONS

It is recommended that more attention should be given to the interpretation and identification of species of the Fusarium genus in superficial clinical samples. This fungus may be considered as an agent of onychomycosis, even in immunocompetent individuals, by identifying criteria that separate situations of clinical significance from those of simple contamination.

Itraconazole therapy is effective for pedal onychomycosis caused by some nondermatophyte molds and in mixed infection with dermatophytes and molds: a multicenter study with 36 patients

BACKGROUND

Onychomycosis of the toenail caused by nondermatophyte molds alone or in combination with dermatophytes is difficult to eradicate with standard antifungal therapy.

OBJECTIVE

Our purpose was to determine the effectiveness of itraconazole in the treatment of toenail onychomycosis caused by molds alone or in combination with dermatophytes.

METHODS

We treated 36 patients with this drug given as continuous dosing (100 or 200 mg/ day) for 6 to 20 weeks or as a 1-week pulse dosing (200 mg twice daily for 1 week per month) for two to four pulses.

RESULTS

Patients with toenail onychomycosis with the following organisms were treated: Aspergillus spp. (eight patients), Fusarium spp. (four patients), Scopulariopsis brevicaulis (23 patients), and Alternaria spp. (one patient). Nineteen patients had onychomycosis with a mixed origin. At follow-up, 12 months after therapy was initiated, clinical and mycologic cure was achieved in 15 of 17 patients (88%) with onychomycosis caused by a single mold. In patients with mixed infection, a clinical cure was obtained in 16 of 19 patients (84%) and a mycologic cure in 13 of 19 patients (68%).

CONCLUSION

Itraconazole appears to be effective and safe for the treatment of toenail onychomycosis caused by some nondermatophyte molds alone or in combination with dermatophytes.