SPECIMEN COLLECTION AND TRANSPORT

Respiratory specimens from the deep portions of the lung, such as bronchoalveolar lavage fluid (BALF), are best for detection of P. jiroveci. A sputum specimen sub mitted for direct examination should be an induced sputum obtained by a trained respiratory therapist; otherwise, the rate of false-negative results may be unacceptably high.

SPECIMEN PROCESSING

See the following section for specific details for specimen processing required for different test methods.

DIRECT DETECTION METHODS

 Stains

 The diagnosis of P. jiroveci pneumonia currently is based on the clinical presentation, radiographic studies, and direct and/or pathologic examination of bronchoalveolar lavage fluid or biopsy material. The flexible-walled trophozoites are the predominant form of the organism, but these are difficult to visualize. They are somewhat discernible in Giemsa-stained material, but their pleomorphic appearance makes this form of the organism difficult to identify. A firm-walled cystic form also exists, although the cysts are outnumbered by the trophozoites 10 to 1. Cysts are more easily recognized than trophozoites and may be definitively identified using a variety of stains, such as calcofluor white, methenamine silver, and immunofluorescent staining (Figure 1). The cysts are spherical to concave, uniform in size (4 to 7 μm in diameter), do not bud, and contain distinctive intracystic bodies.

Fig1. Cystic forms of Pneumocystis jiroveci (arrows) stain  well with methenamine silver and hematoxylin and eosin stain  (×500).

A comparison of the four most common staining methods used for P. jiroveci (i.e., Giemsa, immunofluorescent, calcofluor white, and methenamine silver) has demonstrated that immunofluorescent staining (Meri fluor Pneumocystis; Meridian Bioscience, Cincinnati, Ohio), calcofluor white staining (Fungifluor; Poly sciences, Warington, Pennsylvania), and methenamine silver staining (GMS and DiffQuick; Baxter Scientific, McGraw Park, Illinois) likely represent the best balance between sensitivity and specificity and have the best overall positive and negative predictive values. The immunofluorescent method showed greater sensitivity than the other three but a smaller negative predictive value. Therefore, if this method is used as a screening tool for pneumocystis, a confirmatory method should be performed because of the high number of false-positive results.

Antigen-Protein

 Commercial kits use monoclonal antibodies directed against P. jiroveci to stain both the cysts and the trophozoites. These tests are a highly sensitive microscopic method of detection, but they are expensive. Also, because they use nonspecific staining, which may be thought to represent the pleomorphic trophozoite forms, the specificity of this assay may be limited.

Nucleic Acid Amplification

A variety of nucleic acid amplification assays for P. jiroveci have been developed, including, most recently, real-time polymerase chain reaction (PCR) methods. These methods are making their way from the research setting into the clinical molecular microbiology laboratory, but commercial kits are not yet available.

Cultivation

P. jiroveci is very difficult to cultivate outside the lung; therefore, routine culture methods are not performed.

Approach to Identification

 See Direct Detection Methods.

Serodiagnosis

Serology is not useful for the diagnosis of pneumocystosis.

اخر الاخبار

اخبار العتبة العباسية المقدسة

قسم التطوير يقيم دورة عن أخلاقيات المهنة للمنتسبين الجدد

تتضمن زيارة المراقد المقدسة في كربلاء.. معهد القرآن الكريم النسوي ينظم سفرة دينية لطالباته

المجمع العلمي يحتفي بذكرى ولادة الإمامين الباقر والهادي (عليهما السلام)

قسم الشؤون الفكرية يطلق فعاليات الأسبوع الثالث من برنامج البذرة الصالحة

المزيد

الآخبار الصحية

ثورة طبية.. الذكاء الاصطناعي يكشف سرطان الكلى في وقت قياسي

لتعزيز الطاقة والتغلب على التعب.. عليك بـ7 طرق بسيطة

لتحسين الهضم والتحكم في الشهية.. ما أفضل وقت لتناول التمر؟

خبراء يكشفون تأثير الاستحمام في الظلام على جودة النوم !

المزيد

الآخبار التكنلوجية

إزالة ثاني أكسيد الكربون من الغلاف الجوي.. ما دور المحيطات والبحار؟

نظائر الهيليوم مقياس لاكتشاف رواسب الذهب.. كيف ذلك؟

الصين تطلق أول ناقلة نفط خام ذكية في العالم تعمل بالميثانول

الزمن على المريخ أسرع من الأرض.. دراسة علمية تكشف الفوارق

المزيد

مواضيع ذات صلة

Conventional Yeast identification methods

Commercially available yeast identification systems

Approach to identification of the Yeasts

Specimen collection, transport, and processing of The Yeasts

Cryptococcus neoformans: pathogenesis and spectrum of disease

Candida albicans: pathogenesis and spectrum of disease

General characteristics of the Yeasts

Pathogenesis and spectrum of disease of Pneumocystis jiroveci

General Characteristics of Pneumocystis jiroveci

Approach to Identification of Systemic Mycoses

Pathogenesis and spectrum of disease of Systemic Mycoses

Epidemiology of Systemic Mycoses