الخلاصـة: بغية تحديد السن الذي تقع فيه الإصابة بالوُبَيْغاء المدوَّرة Pityrosporum orbiculare ومعرفة مدى انتشارها على البشرة الطبيعية للأطفال العراقيين الأصحاء، قمنا بإجراء مسح على 110 من الأطفال الأصحاء في بغداد، مـمَّن يتمتعون ببشرة سويَّة من الناحية السريرية، وذلك خلال الفترة من نيسان/إبريل إلى تشرين الأول/أكتوبر 1998. وقمنا باستفراد جرثومة الوُبَيْغاء المدوَّرة وذلك على مستنبت يحتوي على الببتون والغلوكوز والخميرة، كما يحتوي على الكلورامفنيكول والسيكلوهيكسيميد، وتكسوه طبقة من زيت الزيتون. وقد عُثِرَ على هذه الجرثومة على جذع 77.5% من الأطفال الذين تتراوح أعمارهم بين 10-14 عاماً، و27.5% من الأطفال ما بين 5-9 أعوام، و6.6% من الأطفال الذين هم أقل من خمسة أعوام.

ABSTRACT: To determine the age incidence and prevalence of Pityrosporum orbiculare on the normal skin of healthy Iraqi children, we carried out a survey of clinically normal skin of 110 healthy children in Baghdad during April 1998–October 1998. We isolated P. orbiculare on a peptone–glucose–yeast extract medium containing chloramphenicol and cycloheximide, and overlaid with olive oil. The organism was present on the trunk in 77.5% of children 10–14 years, 27.5% of children 5–9 years, and 6.6% of children < 5 years.

Prévalence de Pityrosporum orbiculare sur la peau normale d’enfants iraquiens

RÉSUMÉ: Afin de déterminer l’incidence selon l’âge et la prévalence de Pityrosporum orbiculare sur la peau normale d’enfants iraquiens en bonne santé, nous avons réalisé une étude de la peau cliniquement normale de 110 enfants en bonne santé à Bagdad d’avril à octobre 1998 . Nous avons isolé P. orbiculare dans un milieu peptone-glucose-extrait de levure contenant du chloramphénicol et de la cycloheximide, et enrichi en lipides (huile d’olive). Le micro-organisme était présent sur le tronc chez 77,5 % des enfants âgés de 10-14 ans, chez 27,5 % des enfants âgés de 5-9 ans et chez 6,6 % des enfants de moins de 5 ans. .

¹Department of Dermatology, College of Medicine, University of Baghdad, Baghdad, Iraq.
²Department of Community Medicine, Saddam Medical College, Saddam University, Baghdad, Iraq (Correspondence to W. A. Al-Kubaisy: waqar_abd@yahoo.com). ³Department of Community Medicine, College of Medicine, Al-Mustansiriyah University, Baghdad, Iraq. Received: 13/09/01; accepted: 07/04/04

 

Introduction

Pityrosporum orbiculare was the name given by Gordon to the spherical lipophilic yeast which he cultured from the lesions of pityriasis versicolor [1]. Malassezia furfur has been recorded as the causative organism of pityriasis versicolor. The yeast phase of this organism is classified as P. orbiculare [2,3].

P. orbiculare can be isolated not only from pityriasis versicolor scales, but also from normal skin. Roberts found P. orbiculare to be present on the trunk in more than 92% of the participants in his study [4]. Faergemann and Bernarder cultured P. orbiculare from the back in 90% of healthy individuals in a study done in Sweden [5]. Also, Sharquie, Al-Rubyae and Al-Rawi cultured P. orbiculare from the back in 92% of healthy Iraqis in a Baghdad study [6].

Several studies have been conducted to detect the age incidence of this yeast. In a survey of children, from newborn to age 15 years, P. orbiculare was not cultured from normal-looking skin on the back before the age of 5 years, but was found in 10% of 5-year-old children, 23% of 10-year-old children and 93% of 15-year-old children [7]. In Caracas, P. orbiculare was present in 45% of children 8–10 years old and in 70% of children 13–15 years old [8]. It was subsequently suggested that colonization of normal skin with P. orbiculare begins with the increase in sebum excretion in pre-puberty and puberty [7,8].

Therefore, we conducted this study to identify the age incidence of this yeast on the skin of healthy Iraqi children.

Methods

The study was conducted at the Department of Dermatology, Baghdad Teaching Hospital from April 1998 to October 1998.

We studied 110 normal children. They were all living in Baghdad. Ages ranged from 1 to 14 years. All were healthy children with normal looking skin. And all the skin at the sample sites was clinically normal and had not been affected in the past as far as their parents could recall. Any child on systemic therapy with steroids or antibiotics was excluded as well as those treated with topical applications.

We used peptone–glucose–yeast extract medium containing peptone, 10 g/L, Bacto-agar, 18 g/L, glucose, 40 g/L and yeast extract, 0.1 g/L. The pH was adjusted to 5–6. After autoclave sterilization, chloramphenicol 50 mg/L, gentamycin 100 mg/L and cycloheximide 0.5 g/L were added to the medium.

From each child, skin scrapings were taken from the back in the interscapular region. Scrapings were taken using a fresh, sterile scalpel blade for each site sampled. The specimens were transferred directly to the culture plate and distributed evenly over the entire surface of the plate. Cultures were incubated at 37 °C. Seven days later, the cultures were examined macroscopically and microscopically; if no growth had occurred at that time, they were retained and checked 14 days later.

P. orbiculare was recorded as positive only if thick-walled, spherical budding forms were seen. The presence of clusters was also noted.

Results

The prevalence of P. orbiculare increased with age: 6.7% of samples from children < 5 years, 27.5% of those from children 5–9 years and 77.5% of those from children 10–14 years were positive (Table 1).

On the medium, P. orbiculare grew in a confluent manner with a slight tendency to solitary colonies, white to cream in colour (Figure 1). Microscopically, clusters of round, budding cells were seen (Figure 2).

Discussion

Interestingly, this is the first time P. orbiculare has been isolated from the skin of healthy children under 5 years old—2 of the positive cultures were from 4-year-old children. In contrast, Faergemann and Fredriksson did not detect the organism in children < 5 years old [7].

In agreement with the results of other studies we found that the prevalence of P. orbiculare increased with increasing age [7,8].

Our results indicate that P. orbiculare (the causative agent of pityriasis versicolor) is part of the normal skin flora in Iraqi children and colonization starts during the period when the sebaceous glands become active. This explains why it is difficult to eradicate this infection and at the same time indicates that excessive washing and sterilization of the clothes of people suffering from the condition is not necessary.

Our study was the first in which P. orbiculare was detected on the skin of healthy children in our country. We conclude that P. orbiculare can be detected on the normal skin of healthy children, and is even found in some children < 5 years old. This could possibly be attributed to early activation of sebaceous glands in addition to other factors, but further studies would be needed to determine this.

References

1. Gordon MA. The lipophilic microflora of the skin. In vitro culture of Pityrosporum orbiculare. Mycologia, 1951, 43:524–35.

2. Odom RB, James WD, Berger TG. Diseases resulting from fungi and yeasts. In: Odom RB, James WD, Berger TG, eds. Andrews’ diseases of the skin, 9th ed. Philadelphia, WB Saunders Company, 2000:358–416.

3. Faergemann J. Pityrosporum species as a cause of allergy and infection. Allergy, 1999, 54(5):413–9.

4. Roberts SO. Pityrosporum orbiculare: incidence and distribution on clinically normal skin. British journal of dermatology, 1969, 8(4)1:264–9.

5. Faergemann J, Bernander S. Tinea versicolor and Pityrosporum orbiculare: a mycological investigation. Sabouraudia, 1979, 17(3):171–9.

6. Sharquie KA, Al-Rubyae MG, Al-Rawi JR. Prevalence of Pityrosporum orbiculare on normal skin of Iraqi healthy people. Iraqi journal of community medicine, 2001, 14(1):11–3.

7. Faergemann J, Fredriksson T. Age incidence of Pityrosporum orbiculare on human skin. Acta dermato-venereologica, 1980, 60(6):531–3.

8. Borelli D. Epidemiology, ecology and treatment of pityriasis versicolor in Latin America (Venezuela). In: Oral therapy in dermatomycoses: a step forward: proceedings of a symposium, Frankfurt, February 1985. Oxford, Medicine Publishing Foundation, 1985:111–7.