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Biomedical subjects

R C Summerbell

Publications and source records attributed to R C Summerbell.

At least 55 records · Page 3Linked to original sources
PubMed1998

Prevalence and epidemiology of toenail onychomycosis in diabetic subjects: a multicentre survey.

The number of individuals diagnosed with diabetes mellitus is increasing. The diabetic may present with complications involving all systems of the body. While onychomycosis is often observed in diabetics, there have been no large studies on the prevalence of the condition in this patient group. We examined the prevalence of onychomycosis in diabetics attending diabetes and dermatology clinics in London, Ontario, Canada and Boston, MA, U.S.A. Diabetic subjects seen in dermatology offices were for unrelated dermatoses; those referred specifically for the management of onychomycosis were excluded from the sample. A total of 550 diabetic subjects was evaluated (283 males and 267 females), age 56.1 +/- 0.7 years (mean +/- SEM). Patients with type I diabetes constituted 34% of the sample. The racial origin was: 531 Caucasians, 17 Asians, one African-American and one American-Indian. Abnormal-appearing nails and mycological evidence of onychomycosis (mostly due to dermatophytes) were present in 253 (46%) and 144 (26%), respectively, of 550 subjects. The development of onychomycosis was significantly correlated with age (P < 0.0001) and male gender (P < 0.0001). Males were 2.99 times more likely to have onychomycosis compared with females (95% confidence interval, CI 1.94-4 61). After controlling for age and sex, the risk odds ratio for diabetic subjects to have toenail onychomycosis was 2.77 times compared with normal individuals (95% CI 2.15-3.57). After controlling for age and sex, a stepwise logistic regression demonstrated that significant predictors for onychomycosis included a family history of onychomycosis (P = 0.0001), concurrent intake of immunosuppressive therapy (P = 0.035) and peripheral vascular disease (P = 0.023). Toenail onychomycosis was present in 26% of the sample and is projected to affect approximately one-third of subjects with diabetes. Predisposing factors include increasing age, male gender, family history of onychomycosis, concurrent intake of immunosuppressive agents and peripheral vascular disease.

Adolescent↗
PubMed1998

First isolation of Trichophyton fischeri in the United States.

A 49-year-old male with Pneumocystis carinii pneumonia was seen at Bellevue Hospital in New York, N.Y. Sputum samples yielded cultures of Candida lusitaniae, Mycobacterium avium, and a filamentous fungus, Trichophyton fischeri. T. fischeri is a nonpathogenic fungus which resembles the dermatophyte Trichophyton rubrum. This is the first record of the species from U.S. sources. This case exemplifies the ecological differences between T. fischeri and T. rubrum and illustrates how correct identification of the former species can minimize diagnostic confusion. The two species are distinguished from each other by the type of growth on Casamino Acids-erythritol-albumin agar and by micromorphological differences.

AIDS-Related Opportunistic Infections↗
PubMed1998

An overview of topical antifungal therapy in dermatomycoses. A North American perspective.

Dermatophytes cause fungal infections of keratinised tissues, e.g. skin, hair and nails. The organisms belong to 3 genera, Trichophyton, Epidermophyton and Microsporum. Dermatophytes may be grouped into 3 categories based on host preference and natural habitat. Anthropophilic species predominantly infect humans, geophilic species are soil based and may infect both humans and animals, zoophilic species generally infect non-human mammals. It is important to confirm mycologically the clinical diagnosis of onychomycosis and other tinea infections prior to commencing therapy. The identity of the fungal organism may provide guidance about the appropriateness of a given topical antifungal agent. Special techniques may be required to obtain the best yield of fungal organisms from a given site, especially the scalp and nails. It is also important to realise the limitations of certain diagnostic aids e.g., Wood's light examination is positive in tinea capitis due to M. canis and M. audouinii (ectothrix organisms); however, Wood's light examination is negative in T. tonsurans (endothrix organism). Similarly, it is important to be aware that cicloheximide in culture medium will inhibit growth of non-dermatophytes. Appropriate media are therefore required to evaluate the growth of some significant non-dermatophyte moulds. For tinea infections other than tinea capitis and tinea unguium, topical antifungals may be considered. For effective therapy of tinea capitis an oral antifungal is generally necessary. Similarly, oral antifungals are the therapy of choice, especially if onychomycosis is moderate to severe. Furthermore, where the tinea infection involves a large area, in an immunocompromised host or if infection is recurrent with poor response to topical agents, then oral antifungal therapy may be necessary. Topical antifungal agents may be broadly divided into specific and nonspecific agents. The former group includes the polyenes, azoles, allylamines, amorolfine, ciclopirox and butenafine. Generally the topical agent is available as a cream, sometimes for use intravaginally. Less commonly, the formulation may be in the form of a powder, lacquer, spray, gel or solution. Many of these agents have a broad spectrum of activity, being effective against dermatophytes, yeasts and Malassezia furfur. For the treatment of tinea corporis, tinea cruris tinea versicolor and cutaneous candidosis, once or twice daily application may be required, the most common duration of therapy being 2 to 4 weeks. For tinea pedis the most common treatment duration is 4 to 6 weeks.

Administration, Topical↗
PubMed1998

Increased incidence of Trichophyton tonsurans tinea capitis in Ontario, Canada between 1985 and 1996.

In Canada, since the 1990s, Trichophyton tonsurans has emerged as the main cause of tinea capitis. Prior to this the more common agents were T. verrucosum, Microsporum canis and M. audouinii. Over the past few years the incidence of T. tonsurans has increased such that in 1985 and 1996 the cases of mycologically confirmed tinea capitis due to T. tonsurans were 9% and 76%, respectively. The epidemic of T. tonsurans has reduced the role of Wood's lamp in diagnosis of tinea capitis. The age distribution of tinea capitis due to T. tonsurans closely matches that of mycologically confirmed tinea capitis, being most common in children under 14 years of age. There is no significant sex difference in children who develop T. tonsurans tinea capitis; however, subjects are significantly more likely to live in urban than rural areas. This should provide guidance regarding where to concentrate health resources and deliver patient/parent education to combat this epidemic of tinea capitis.

Adolescent↗
PubMed1998

Importance of Candida species other than Candida albicans as opportunistic pathogens.

Candida species other than C. albicans have become a significant cause of infection in humans. Several of the more commonly isolated of these species are less susceptible to commonly used azole antifungal drugs, a factor that poses significant difficulties for effective treatment. The modern mycology laboratory has an important role to play in several aspects relating to these organisms, including therapy, detection, identification and epidemiological analysis. The application of molecular techniques and phylogenetic analysis has led to the identification of a new species of Candida associated with mucosal candidiasis in HIV-infected individuals named Candida dubliniensis, the clinical significance of which is currently under investigation. Molecular techniques are also being applied to the analysis of determinants involved in pathogenicity of species such as Candida glabratta. These approaches should lead to a better understanding of these organisms and there ability to cause disease and should also provide more effective treatment.

AIDS-Related Opportunistic Infections↗
PubMed1998

Dermatophytes and host defence in cutaneous mycoses.

Dermatophytosis is the infection of keratinized tissues such as hair, nails and the stratum corneum of the skin by dermatophyte fungi. These fungi are onygenalean anamorphs and anamorphic species belonging to the genera Trichophyton, Microsporum and Epidermophyton. An important characteristic of the dermatophytes as parasites is their restriction to the dead keratinized tissues, except in rare cases where the patient is immunosuppressed. In contrast to many fungi, including normally non-pathogenic species, which can invade systemically in severely immunocompromised (e.g. neutropenic) patients, dermatophytes appear to be unable to cause systemic infection in this population. Thus, these fungi appear to have an unique interaction with the immune system. A better understanding of this interaction will contribute significantly to our knowledge of mammalian host defences.

Arthrodermataceae↗
PubMed1997

Itraconazole pulse therapy is effective in the treatment of tinea capitis in children: an open multicentre study.

In an open multicentre study we have demonstrated that itraconazole pulse therapy, 5 mg/kg per day, is effective and safe in the management of tinea capitis in 10 children (seven boys, three girls, mean age: 6.6 years, age range 4-11 years). The causative organisms were Trichophyton tonsurans (six cases), T. violaceum (two cases), T. soudanense (one case) and Microsporum gypseum (one case). Each pulse of drug therapy lasted 1 week with 2 weeks off between consecutive pulses. One, two and three pulses produced complete, clinical and mycological, cure in one, six and three patients, respectively. The children tolerated the treatment well and there were no clinical or laboratory adverse effects. This 1-week pulse therapy regimen resulted in a high degree of compliance. The preliminary results of this study are promising and need to be evaluated in a larger sample of patients.

Administration, Oral↗
PubMed1997

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.

Adolescent↗
PubMed1997

Invasive Nattrassia mangiferae infections: case report, literature review, and therapeutic and taxonomic appraisal.

We report on a case of subcutaneous infection of the arm caused by the coelomycetous fungus Nattrassia mangiferae (formerly Hendersonula toruloidea) in a steroid-dependent diabetic man with chronic obstructive lung disease. The man was a resident of Arizona, where the fungus is known to be endemic on Eucalyptus camaldulensis and on citrus trees. Diagnosis of fungal infection was made by observation of narrow hyphal filaments by histopathology of biopsy specimens and isolation of a fast-growing black mold which demonstrated hyphae and arthroconidia of varying widths typical of the Scytalidium synanamorph (S. dimidiatum). The formation of pycnidia, which at maturity expressed conidia with a central median dark band, allowed for the confirmation of the isolate as N. mangiferae. Remission of the lesions occurred following intravenous therapy with amphotericin B, followed by topical clotrimazole treatment. We use this patient's case report as an opportunity to review the literature on cases of deep infection caused by Scytalidium species, to evaluate the antifungal susceptibilities of a spectrum of Scytalidium isolates, and to review the taxonomy of Scytalidium species isolated from human infections.

Aged↗
PubMed1997

Epidemiology and ecology of onychomycosis.

The epidemiology and ecology of onychomycosis are complex and little understood. Most is known about tinea unguium, dermatophytic nail infection, and its causative agents. This is often categorised according to the precise locus on the nail of the infection. The principal infectious propagules are thought to be the arthroconidia or chlamydospores which form within the solid substratum of invaded nail tissue. The process of infecting new hosts appears to be facilitated by abrasion, moistening and scratching. The role of the non-dermatophyte yeast Candida as an agent of onychomycosis per se may have been overestimated. The range of interactions between dermatophytes and non-dermatophytes in nails is complex and poorly understood. There may be at least six distinct ecological categories of non-dermatophyte isolations from nails. It would be of clinical interest to know which species found in mixed infections were never able to advance beyond 'secondary colonisation', as they would not require specific treatment.

Adult↗
PubMed1997

A higher prevalence of onychomycosis in psoriatics compared with non-psoriatics: a multicentre study.

There is some controversy about the prevalence of onychomycosis in patients with psoriasis compared to non-psoriatics. We therefore measured the prevalence of toenail onychomycosis in psoriatics and non-psoriatics attending dermatologists' offices. None of the patients had a referring diagnosis of onychomycosis. The prevalence of pedal onychomycosis in psoriatics (n = 561) was 13%. The odds of patients with psoriasis having onychomycosis was 56% greater than non-psoriatics of the same age and sex (P = 0.02). In the psoriatics, when the toenails were clinically abnormal, the prevalence of onychomycosis was 27%. The odds of developing onychomycosis increased with age (P < 0.0001) and the odds of men developing onychomycosis was 2.5 times that of women (P = 0.0001). The duration of psoriasis did not significantly affect the odds of developing onychomycosis. The fungal organisms recovered from psoriasis subjects with onychomycosis were similar to those in the normal population with onychomycosis (P = 0.58).

Female↗
PubMed1997

Cutaneous mycoses in chameleons caused by the Chrysosporium anamorph of Nannizziopsis vriesii (Apinis) Currah.

A dermatophyte-like fungus was isolated from skin biopsies of three different species of captive chameleon in which fungal elements had been observed by histologic examination. An adult Parson's chameleon (Chamaeleo parsonii) presented with vesicles that became crusty brown lesions on the limbs and body. Skin biopsies revealed fungal hyphae in the affected epidermis and underlying dermis. The lesions regressed fully after oral administration of itraconazole. An adult jewel chameleon (Chamaeleo lateralis) from the same private collection presented with localized black skin lesions and died while being treated with itraconazole. A pulmonary granuloma was also present in this chameleon at autopsy. Cultures obtained from skin and lung lesions yielded the same fungus. A third isolate was obtained from a skin biopsy of a Jackson's chameleon (Chamaeleo jacksoni) with deep ulcerative cutaneous lesions located at the base of the tail. The fungus, in all three cases, has been identified as the Chrysosporium anamorph of Nannizziopsis vriesii, a poorly known ascomycetous species recorded previously from the skin of a lizard and from soil, on the basis of its keratinolytic activity, resistance to cycloheximide, strongly restricted growth at 37 degrees C, formation of clavate or pyriform single-celled or two-celled aleurioconidia, and alternate and fission arthroconidia.

Administration, Oral↗
PubMed1995

Application of the API YeastIdent system in determining the enzymatic profiles of Nocardia asteroides isolates.

Glucose represses production of ammonium in many clinical isolates of Nocardia asteroides growing on bromcresolpurple casein glucose agar. Strains exhibiting this property are designated as group A, while group B represents isolates showing a high degree of proteolytic activity and a resulting rapid increase in pH. Twenty isolates of N. asteroides were characterized as group A or B. Enzymatic profiles obtained using the API YeastIdent system showed significant enzymatic variation between 12 group B and 8 group A isolates. Proteolytic enzymes which most varied in activity between groups were glycine aminopeptidase, histidine aminopeptidase and leucyl glycine aminopeptidase. As some of the N. asteroides isolates were isolated from asymptomatic patients, it is of interest to consider the possibility of one group being of low virulence while the other is more strongly associated with infection.

Bacterial Typing Techniques↗
PubMed1995

The dermatophytes.

The etiologic agents of the dermatophytoses (ringworm) are classified in three anamorphic (asexual or imperfect) genera, Epidermophyton, Microsporum, and Trichophyton. Species capable of reproducing sexually belong in the teleomorphic genus, Arthroderma, of the Ascomycota. On the basis of primary habitat association, they may be grouped as geophilic (soil associated), zoophilic, and anthropophilic. Adaptation to growth on humans by most geophilic species resulted in diminished loss of sporulation, sexuality, and other soil-associated characteristics. The dermatophytes have the ability to invade keratinized tissue (skin, hair, and nails) but are usually restricted to the nonliving cornified layer of the epidermis because of their inability to penetrate viable tissue of an immunocompetent host. However, invasion does elicit a host response ranging from mild to severe. Acid proteinases, elastase, keratinases, and other proteinases reportedly act as virulence factors. The development of cell-mediated immunity correlated with delayed hypersensitivity and an inflammatory response is associated with clinical cure, whereas the lack of or a defective cell-mediated immunity predisposes the host to chronic or recurrent dermatophyte infection. Chronic dermatophytosis is mostly caused by Trichophyton rubrum, and there is some evidence that mannan produced by this fungus suppresses or diminishes the inflammatory response. Since dermatophytes cause a communicable disease, modes of transmission and control are discussed as well as a survey of recent trends in therapy. Collection of specimens, culture media, and tests for identification are also presented. Genetic studies have led to an understanding of incompatibility mechanisms, pleomorphism and variation, resistance to griseofulvin, and virulence. Molecular biology has contributed to our knowledge of the taxonomy and phylogenetic relationships of dermatophytes.

Antigens, Fungal↗
PubMed1994

Fungal sternal wound infection due to Curvularia lunata in a neonate with congenital heart disease: case report and review.

We describe a neonate with congenital heart disease in whom a sternal wound infection caused by the filamentous fungus Curvularia lunata developed following cardiac surgery. Despite their widespread distribution in the environment, Curvularia species rarely cause human infection. We also review the 43 cases of curvularia infection previously reported in the English-language literature; only four of these cases occurred in children. A wide spectrum of infections--including keratitis, cutaneous infections, sinusitis, allergic bronchopulmonary disease, pneumonia, chronic ambulatory peritoneal dialysis-related infections, endocarditis and disseminated infections--have been described. Curvularia is a pathogen that can cause disease in both immunocompetent and immunocompromised hosts, although more severe and disseminated disease occurs in patients with defective immune function. Surgery alone usually is successful for treating locally invasive disease, although a combination of medical and surgical therapy is necessary for treating disseminated infections.

Fatal Outcome↗
PubMed1993

The benomyl test as a fundamental diagnostic method for medical mycology.

The fungicide benomyl has long been known to differentially affect major taxonomic groups of fungi. In the present study 163 species or aggregates of closely similar species of medically important fungi and actinomycetes, as well as species commonly isolated as clinical contaminants, were tested to determine their reactions to three concentrations of benomyl. Fungi of basidiomycetous, endomycetous, and microascaceous affinities were highly resistant, including all common yeasts and Geotrichum, Pseudallescheria, Scedosporium, and Scopulariopsis species. Also resistant were fungi of pleosporalean affinities with poroconidial anamorphs, such as Alternaria, Bipolaris, Curvularia, and Exserohilum species. Most other fungi of ascomycetous affinity were moderately to strongly susceptible. Such fungi included dermatophytes; Coccidioides, Blastomyces, and Histoplasma species; Sporothrix schenckii; medically important aspergilli; and "black yeasts." Benomyl testing aided in the provisional identification of nonsporulating mycelia, including common basidiomycetous isolates obtained as contaminants as well as nonsporulating Aspergillus fumigatus from pulmonary sources.

Actinomycetales↗