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Penicillium marneffei

penicillium marneffei, penicillium marneffei infection
Penicillium species are usually regarded as unimportant in terms of causing human disease Penicillium marneffei, now called Talaromyces marneffei, discovered in 1956, is an exception This is the only known thermally dimorphic species of Penicillium, and it can cause a lethal systemic infection penicilliosis with fever and anaemia similar to disseminated cryptococcosis

Contents

  • 1 Epidemiology
  • 2 Clinical Presentation
  • 3 Laboratory diagnosis
  • 4 Treatment
  • 5 Research
    • 51 Genomics
    • 52 Sexual reproduction
  • 6 References
  • 7 Further reading

Epidemiology

There is a high incidence of penicilliosis in AIDS patients in SE Asia; 10% of patients in Hong Kong get penicillosis as an AIDS-related illness Cases of P marneffei human infections penicillosis have also been reported in HIV-positive patients in Australia, Europe, Japan, the UK and the US All the patients, except one, had visited Southeast Asia previously

Discovered in bamboo rats Rhizomys in Vietnam, it is associated with these rats and the tropical Southeast Asia area Penicillium marneffei is endemic in Burma Myanmar, Cambodia, Southern China, Indonesia, Laos, Malaysia, Thailand and Vietnam

Although both the immunocompetent and the immunocompromised can be infected, it is extremely rare to find systemic infections in HIV-negative patients

The incidence of P marneffei is increasing as HIV spreads throughout Asia An increase in global travel and migration means it will be of increased importance as an infection in AIDS sufferers

Penicillium marneffei has been found in bamboo rat faeces, liver, lungs and spleen It has been suggested that these animals are a reservoir for the fungus It is not clear whether the rats are affected by P marneffei or are merely asymptomatic carriers of the disease

One study of 550 AIDS patients showed that the incidence was higher during the rainy season, which is when the rats breed but also when conditions are more favorable for production of fungal spores conidia that can become airborne and be inhaled by susceptible individuals

Another study could not establish contact with bamboo rats as a risk factor, but exposure to the soil was the critical risk factor However, soil samples failed to yield much of the fungus

It is not known whether people get the disease by eating infected rats, or by inhaling fungi from their faeces

There is an example of an HIV-positive physician who was infected while attending a course on tropical microbiology He did not handle the organism, though students in the same laboratory did It is presumed he contracted the infection by inhaling aerosol containing P marneffei conidia This shows that airborne infections are possible

Clinical Presentation

Patients commonly present with symptoms and signs of infection of the reticuloendothelial system, including generalized lymphadenopathy, hepatomegaly, and splenomegaly The respiratory system is commonly involved as well; cough, fever, dyspnea, and chest pain may be present, reflecting the probable inhalational route of acquisition Approximately one-third of patients may also exhibit gastrointestinal symptoms, such as diarrhea

Laboratory diagnosis

The fact that Penicillium marneffei is thermally dimorphic is a relevant clue when trying to identify it However, it should be kept in mind that other human-pathogenic fungi are thermally dimorphic as well Cultures should be done from bone marrow, skin, blood and sputum samples

Plating samples out onto two Sabouraud agar plates, then incubating one at 30 °C and the other at 37 °C, should result in two different morphologies A mold-form will grow at 30 °C, and a yeast-form at 37 °C

Mycelial colonies will be visible on the 30 °C plate after two days Growth is initially fluffy and white and eventually turns green and granular after sporulation has occurred A soluble red pigment is produced, which diffuses into the agar, causing the reverse side of the plate to appear red or pink The periphery of the mold may appear orange-coloured, and radial sulcate folds will develop

Under the microscope, the mold phase will look like a typical Penicillium, with hyaline, septate and branched hyphae; the conidiophores are located both laterally and terminally Each conidiophore gives rise to three to five phialides, where chains of lemon-shaped conidia are formed

On the 37 °C plate, the colonies grow as yeasts These colonies can be cerebriform, convoluted, or smooth There is a decreased production in pigment, the colonies appearing cream/light-tan/light-pink in colour Microscopically, sausage-shaped cells are mixed with hyphae-like structures As the culture ages, segments begin to form The cells divide by binary fission, rather than budding The cells are not yeast cells, but rather arthroconidia Culturing isn't the only method of diagnosis A skin scraping can be prepared, and stained with Wright's stain Many intracellular and extracellular yeast cells with crosswalls are suggestive of P marneffei infection Smears from bone marrow aspirates may also be taken; this is regarded as the most sensitive method These samples can be stained with the Giemsa stain Histological examination can also be done on skin, bone marrow or lymph nodes

The patient's history also is a diagnostic help If they have traveled to Southeast Asia and are HIV-positive, then there is an increased risk of them having penicilliosis

Antigen testing of urine and serum, and PCR amplification of specific nucleotide sequences have been tried, with high sensitivity and specificity Rapid identification of penicilliosis is sought, as prompt treatment is critical Treatment should be provided as soon as penicilliosis is suspected

Treatment

2 weeks of amphotericin B, then 10 weeks of oral itraconazole

Research

Genomics

Sexual reproduction

P marneffei had been assumed to reproduce exclusively by asexual means based on the highly clonal population structure of this species However, studies by Henk et al 2012 revealed that the genes required for meiosis are present in P marneffei In addition, they obtained evidence for mating and genetic recombination in this species Henk et al concluded that P marneffei is sexually reproducing, but recombination in natural populations is most likely to occur across spatially and genetically limited distances resulting in a highly clonal population structure It appears that sex can be maintained in this species even though very little genetic variability is produced

References

  1. ^ Chan, JF; Lau, SK; Yuen, KY; Woo, PC "Talaromyces Penicillium marneffei infection in non-HIV-infected patients" Emerg Microbes Infect 5:e19 doi:101038/emi201618 PMC 4820671  PMID 26956447 
  2. ^ Lo Y, Tintelnot K, Lippert U, Hoppe T 2000 "Disseminated Penicillium marneffei infection in an African AIDS patient" Trans R Soc Trop Med Hyg 94 2:187 doi:101016/S0035-92030090271-2 PMID 10897365 
  3. ^ Capponi M, Segretain G, Sureau P 1956 "Pénicillose de Rhizomys sinensis" Bull Soc Pathol Exot 49 3:418–21 
  4. ^ Louthrenoo, W; Thamprasert, K; Sirisanthana, T Dec 1994 "Osteoarticular penicilliosis marneffei A report of eight cases and review of the literature" British journal of rheumatology 33 12:1145–50 doi:101093/rheumatology/33121145 PMID 8000744 
  5. ^ Duong, TA Jul 1996 "Infection due to Penicillium marneffei, an emerging pathogen:review of 155 reported cases" Clinical Infectious Diseases 23 1:125–30 doi:101093/clinids/231125 PMID 8816141 
  6. ^ Supparatpinyo, K; Khamwan, C; Baosoung, V; Nelson, KE; Sirisanthana, T Jul 9, 1994 "Disseminated Penicillium marneffei infection in southeast Asia" Lancet 344 8915:110–3 doi:101016/s0140-67369491287-4 PMID 7912350 
  7. ^ a b Henk DA, Shahar-Golan R, Devi KR, Boyce KJ, Zhan N, Fedorova ND, Nierman WC, Hsueh PR, Yuen KY, Sieu TP, Kinh NV, Wertheim H, Baker SG, Day JN, Vanittanakom N, Bignell EM, Andrianopoulos A, Fisher MC 2012 "Clonality despite sex:the evolution of host-associated sexual neighborhoods in the pathogenic fungus Penicillium marneffei" PLoS Pathog 8 10:e1002851 doi:101371/journalppat1002851 PMC 3464222  PMID 23055919 

Further reading

  • Vanittanakom N, Cooper CR Jr, Fisher MC, Sirisanthana T 2006 "Penicillium marneffei infection and recent advances in the epidemiology and molecular biology aspects" Clin Microbiol Rev 19 1:95–110 doi:101128/CMR19195-1102006 PMC 1360277  PMID 16418525 

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    Penicillium marneffei beatiful post thanks!

    29.10.2014


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