0809-3 Aspergillus niger by sre20968

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									   CMPT Mycology Plus                                                                        September 2008

0809-3 Aspergillus niger                                            umns at maturity. The species is biseriate (vesicles pro-
                                                                    duces sterile cells known as metulae that support the co-
HISTORY This sample was sent as a simulated sputum sample.          nidiogenous phialides). Conidiophores are long (400-3000
CMPT QA: Pure growth of 4+ Aspergillus niger, viable for 37         µm), smooth, and hyaline, becoming darker at the apex
days.                                                               and terminating in a globose vesicle (30-75 µm in di-
Reference Laboratory: Growth of 4+ Aspergillus niger confirmed.
                                                                    ameter). Metulae and phialides cover the entire vesicle.
                                                                    Conidia are brown to black, very rough, globose, and
All laboratories that processed the sample correctly reported       measure up to 6 or 7µm diameter. Syncephalastrum ra-
the genus; identifications received and media noted by partici-     cemosum, generally considered a contaminant, may at
pants are shown in Table 1. Participants continue to perform        first resemble A. niger, but careful examination reveals
well as results received are similar to previous challenges with    tubular sporangia and the absence of phialides 2.
this fungus (critiques 0704-3 and 0609-3).
                                                                    Other Methods PCR-based identification systems could
                                                                    provide a powerful tool to control invasive fungal infec-
 Table 1. 0809-3 Aspergillus niger reports received and
                                                                    tions and to speed the application of effective treatment 5.
 media noted.
                                                                    CLINICAL SIGNIFICANCE 1, 6,7 Aspergillus species are
 Report received       No.    Media reported
                       labs
                                                                    ubiquitous organisms, which are spread by aerosolization of
                              SAB/CC/30oC, IMA/30oC, BHIB/          the spores. A. niger may be a laboratory contaminant,
 Aspergillus            8
                              CG/30oC, PDA/30oC; IMA / 30oC,        but it is perhaps more important to note that A. niger
 niger
                              BHI + chloramphenicol/30oC,           may also be a transient colonizer of the upper respira-
                              PDA/30oC; IMA /30oC, PDA;             tory tract of patients resulting in reporting clinically
                              IMA/25oC & 37oC, BHI, BHI/C ;         false positive cultures. Fungal culture of multiple (3 at
                              Littman/25oC, Mycosel/25oC, SAB-      least) serial sputum samples is recommended when-
                              HI/25oC; SAB/27oC, BHIB/27oC,         ever fungal infection is suspected 1. Host factors, clini-
                              IMA/27oC; IMA/29oC, BHI               cal signs and symptoms, and mycology results are
                              CGC/29oC, BHI-CG/29oC; PYE 30oC
                                                                    used to define true- from false-positive cultures 1.
 Aspergillus            1     SAB/30oC, BHI+chloramphenicol and
 species                      gentamicin/30oC                       Dependent upon the immunologic condition of the host
 Sample not normally
                                                                    pulmonary aspergillosis has been classified into four types.
                        1     n/a
 processed                                                          These include invasive pulmonary aspergillosis, semi-
                                                                    invasive pulmonary aspergillosis, pulmonary aspergilloma,
               Total    10
 Media key: SAB: Sabouraud dextrose agar; IMA: inhibitory mold
                                                                    and allergic bronchopulmonary aspergillosis. The rapidly
 agar; BHI: brain heart infusion; PDA: potato dextrose agar; PYE:   developing acute invasive pulmonary aspergillosis is found
 phytone ; CGC: chloramphenicol, gentamicin, cycloheximide          almost exclusively in immunosuppressed neutropenic and
                                                                    myelosuppressed patients. The diagnosis of invasive asper-
 IDENTIFICATION This information was included in cri-               gillosis relies on the histologic demonstration of fungal in-
 tique 0704-3; for a review of Aspergillus species please refer     vasion and the isolation of Aspergillus from normally sterile
 to the critique for CMPT Mycology Plus 0609-3.                     clinical samples. However, the culture yield of an Aspergillus
 When isolated on Sabouraud dextrose agar, aspergilli tend to       or another septate mold from infected tissue has been shown to
 reproduce in the asexual form, therefore isolates are usually      be generally low, ranging from 30% to 50% 6. A. niger is
 inoculated (at three points) on Czapek dox agar and potato         thought to be less likely than A. fumigatus to be associated
 dextrose agar and incubated at 25oC 1. Most species sporulate      with invasive disease due to some physiological, structural,
 within 7 days. Both macroscopic morphology, primarily              and acidophilic characteristics. The size of A. niger conidia
 based on colony pigmentation, and microscopic morphology           (up to 6 or 7µm) and the presence of strong interspore
 of the conidial head are required for identification. Mi-          bridges impairs its penetration into the lower respiratory
 croscopic mounts are best made using a cellotape flag or           tract. After inhalation, the spores are therefore easily cap-
 slide culture preparation mounted in lactophenol cotton blue.      tured and eliminated by the host mucociliary system. The
 A drop of alcohol is usually needed to detach the cellotape        ideal temperature for Aspergillus niger growth is around
 flag from the stick, and to act as a wetting agent.                30ºC, which makes germination difficult in the human body
                                                                    temperature (~37ºC). Another limiting condition for fungal
 Colony morphology 2-4 Colonies on potato dextrose agar             pathogenicity is the acidophilic nature of A. niger (ideal pH
 at 25°C are wooly initially white, quickly becoming black          4.5-4.8) 9.
 with conidial production. Reverse is white to pale yellow and
 growth may produce radial fissures in the agar.                     In chronic necrotizing pulmonary aspergillosis or semi-
                                                                    invasive pulmonary aspergillosis, the hosts have a produc-
 Microscopic morphology 2-4 Hyphae are septate and hya-             tive cough with positive sputum cultures for Aspergillus.
 line. Conidial heads are radiate initially, splitting into col-
                                                                                                               (Continued on page 2)

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CMPT Mycology Plus                                                                                  September 2008

The appearance of endobronchial black necrotic debris or a        REFERENCES
fungus ball or the finding of black acidic sputum or pleural      1. Verweij PE, Brandt ME. 2007. p. 1802-1838. Asper-
fluid suggests the presence of A niger and the destructive           gillus, Fusarium, and other opportunitistic monili-
by-product of its fermentation, oxalic acid 8. It is interest-       aceous fungi. In PR Murray et al. (ed.) Manual of
ing to consider the role of oxalic acid in this destructive and      Clinical Microbiology. Ch. 121. 9th ed. ASM Press.
invasive process. The association of oxalic acid as a fer-           Washington, DC.
mentation product of Aspergillus sp (most notably A niger)        2. Larone DH. 2002. p. 175 and 266. Medically Im-
was first reported in 1891 by Wehmer. Calcium oxalate                portant Fungi. 4th ed. ASM Press. Washington, DC.
crystals may signal A. niger infection even in the absence of     3. h t t p : / / w w w . m y c o l o g y . a d e l a i d e . e d u . a u /
identified fungal elements. Such was a case of A. niger in-          Fungal_Descriptions/Hyphomycetes_(hyaline)/
fection in which the presence of crystals on transbronchial          Aspergillus/niger.html
biopsy specimens was the only laboratory indication of            4. h t t p : / / w w w . d o c t o r f u n g u s . o r g / t h e f u n g i /
aspergillosis before fungal cultures became positive 10.             Aspergillus_niger.htm
Some aspergillomas follow a very benign course and either         5. Chise Sugita C, Makimura K, Uchida K, et al. 2004.
remain stable, increase in size, or spontaneously resolve            PCR identification system for the genus Aspergillus
without treatment. Under unusual circumstances, the behav-           and three major pathogenic species: Aspergillus
ior of an aspergilloma may change from a chronic, benign             fumigatus, Aspergillus flavus and Aspergillus niger.
lesion into an invasive, life-threatening infection; however,        Med Mycology. 42:5. p. 433 – 437.
cases from patients without a predisposing immune com-            6. Tarrand JJ, Lichterfeld M, Warraich I, et al.2003.
promise are rare.                                                    Diagnosis of invasive septate mold infections: a
                                                                     correlation of microbiological culture and histologic
ANTIFUNGAL SUSPECTIBILITY TESTING AND                                or cytologic examination. Am J Clin Pathol.
TREATMENT If Aspergillus species are isolated repeat-                119:854- 858.
edly and/or are considered clinically relevant, or if the pa-     7. Zaman SU, Sarma DP: 2007. Maxillary sinus myce-
tient is failing treatment, then identification to the species       toma due to Aspergillus niger. Internet J Otorhi-
level is required. Different species of Aspergillus vary in          nolaryngology. 6:1. http://www.ispub.com/ostia/
their susceptibility to antifungal agents, e.g., the species A.      index.php?xmlFilePath=journals/ijorl/vol6n1/
terreus is resistant to amphotericin B 1. CLSI has devel-            niger.xml#e2e2
oped a reference method for in vitro susceptibility testing of    8. Kimmerling EA, Fedrick JA, Tenholder MF. 1992.
conidium–forming molds for some antifungals 1, 11; how-              Invasive Aspergillus niger with fatal pulmonary
ever, no MIC breakpoints are available for any molds with            oxalosis in crhonic obstructive pulmonary disease.
any antifungal drug 1. The E test has been shown good                Chest. 101: 870-872. From URL: chestjournal.org
correlation with the CLSI reference method. Susceptibility           [downloaded November 6, 2008]
testing can be performed either in-house or by forwarding         9. Orzechowski Xavier M. 2008. Aspergillus niger caus-
to a reference laboratory1.                                          ing tracheobronchitis and invasive pulmonary asper-
Treatment may include lipid formulations of ampho-                   gillosis in a lung transplant recipient: case report. Re-
tericin B and itraconazole; other choices include vori-              vista da Sociedade Brasileira de Medicina Tropical
conazole, caspofungin, micafungin, anidulafungin, and                41:2. p. 200-201.
posaconazole 1. Prolonged treatment is likely necessary.          10. Murgu SD, Colt H. 2005. Bronchoscopic lung
A combination of itraconazole and amphotericin B was                  biopsy evidence of calcium oxalate crystals signals
used for two months to treat a 48-year old female lung                Aspergillus niger infection. Chest. Available at
transplant recipient when A. niger was recovered from                 URL http://meeting.chestjournal.org/cgi/content/
her lung biopsy, sputum, and bronchoalveolar lavage                   abstract/128/4/439S
samples. Although follow-up cultures were negative, A.            11. CLSI/NCCLS. 2002. Reference Method for Broth
niger invaded the lung parenchyma and the patient died                Dilution Antifungal Susceptibility Testing of Fila-
of invasive pulmonary aspergillosis 9.                                mentous Fungi. Approve standard. NCCLS docu-
                                                                      ment M38-A. NCCLS. Wayne, Pa.

                                                                  Suggested reading:
                                                                  Mycology Plus 0609-3 Simulated bronchial aspirate: A. fla-
                                                                  vus. http://www.cmpt.ca/pdf_mycology/0609_3_aflav.pdf
                                                                  Mycology Plus 0409-3 Simulated Blood isolate: A. flavus;
                                                                  Mycology Plus 0405-3 Simulated Skin: Aspergillus fumiga-
                                                                  tus




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