microbiology

3. • Penicillium species are usually observed as unimportant species in causing
human disease.
• But Penicillium marneffie is a rising pathogenic fungus that can fatal
systemic mycosis in patients infected with:
• Human Immunodeficiency Virus (HIV).
• It can also cause a dangerous Systemic Infection (Penicilliosis) with Fever
and Anemia similar to Disseminated Cryptococcosis.
• The molarity rate of Penicillium marneffie patients has been extremely
high.

4. • In tropical
Asia,
especially :
• P.Marneffei
infection is
endemic.
Thailand
Northeaste
rn India
Vietnam,
and
Taiwan
China,
Hong
Kong

5. P.marneffie was first isolated from the hepatic
lesions of a bamboo rat (Rhizomys sinensis) in
1956.
The bamboo rat die spontaneously from the
reticuloendothelial mycosis.
The fungus was named Penicillium marneffie,
in honor of Hubert Merneffe, who was the
director of Pasteur Institute of Indochina. Hubert Merneffe

6. • After the infection discovery in wild rodents’ two cases of human infections
were reported.
• Human penicilliosis marneffei was first described as a laboratory-acquired
infection.
• When researcher g. Segretain accidentally pricked his own finger with a
needle filled with P. Marneffei that was being used to inoculate hamsters.
• He developed a small nodule at the site of inoculation followed, by axillary
lymphadenopathy.
• This accidental infection was cured by intensive treatment with oral NY statin
for 30 days.
• In 1973, the group of researchers including DiSalvo reported the first natural
human infection of P. marneffei from a patient living in North Carolina
(DiSalvo 1973).

8. 1. P. marneffie was classified in the section Asymmetrical,
subsection Divaricata, in the classification of Raper and
Thoms, which is equivalent to Pitt’s subgenus Furcatum.
2. Pitt later assigned P.marneffie to the subgenus Biverticillium.
This classification was confirmed by Frisvad and Filtenbog on the
basis of similar physiology and secondary metabolites profiles.
3. A polygenetic analysis of P.marneffie, as assed by the
nucleotide sequences of nuclear and mitochondrial rRNA gene
regions, demonstrated that P.marneffie is closely related to the
species of the Penicillium subgenus Biverticillium and sexual
Talaromyces species with asexual biverticillate Penicillium
states.

9. • Soil exposure, often during the rainy season.
• Transmission of P.Marneffie can occur from rodents to human or rodents
and humans are confected from common environmental sources.
• The main route of infection is thought to be through inhalation of conidia
into the lungs, where it can then disseminate via a hematogenous route to
other body locations, especially the liver.

10. VIRULENT FACTOR:
• The special feature of P.marneffie
compared to other penicillia is its
thermal dimorphism.
• This capability to grow as mycelium
at 25 degrees C colonies can be
cultured which are filamentous in
form.
• And as a yeast 37 degrees C is this
organism main virulence factor
expressed as oval shaped unicellular
yeast cells.
LENGTH:
• 4 to 8 micrometer in diameter.

11. The distinctive central transverse septum, by the process of fission, is special
to P.marneffie. Also budding and cysts forms are absent.
In P.marneffie infection. Fungal cell types can be categorized into one of
two groups; those that show polarized apical growth and those that exhibit
isotropic growth.
Dimorphic switching requires fungal cells to undergo changes in polarized
growth in response to environmental stimuli and during cell differentiation.
Temperature is below 25 degrees Celsius, the fungus growth is as
multinucleate mycelia with the formation of septate, and branched hyphae.
25-37 degrees Celsius temperature shift activates the arthroconidiation
programme, where cell and nuclear division become coupled, double septa
are deposited between hyphal cells and cell separation occurs along the
septal plane to free signal yeast cells.

12. • P.marneffie is believed to be haploid, with at least
six large chromosomes.
• The genome size of P.marneffie has been estimated
to be in the range of 17.8 to 26.2 Mb.
• The completed mitochondrial genome shows that it
is circular, contains 35,438 nucleotides, and has a
GC content of 24%.
• The mitochondrial genome of P.marneffie is more
closely related to those of molds than those of yeast.
Genome Structure

13. • Thermal means ‘heat’ and dimorphism means ‘two forms’.
• This character is observed in fungi (dimorphic fungi), which exist as yeast at
37oC and below this temperature it exists as mycelium form i-e; at 250C.
• Penicillium species are usually observed as insignificant in terms of causing
human disease.
• Penicillium marneffei is an exception. This is the only known thermally
dimorphic species of Penicillium which can cause a fatal systemic infection
(penicilliosis) with fever and anemia.

15. • Effect of temperature.
• Effect of enzymes.

16. • Since, Penicillium marneffei is a dimorphic specie, so its life cycle as
yeast-like form and mycelial form is different i-e; in yeast-like form it
reproduces by binary fission and in mycelial form reproduces by
sporulation.
1. Life cycle as yeast.
2. Life cycle as mycelial form.

17. • Life cycle as yeast.

18. • Life cycle as mycelium.

19. • Plating samples out onto two Sabouraud agar plates, then incubate one
at 30 °C and the then other at 37 °C, results in two dissimilar
morphologies. A mold-form grows at 30 °C, and a yeast-form at
37 °C.
• Mycelial colonies will be observable on the 30 °C plate after two days.
Growth is initially downy 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-colored, and radial sulcate folds will develop.
• On the 37 °C plate, the colonies grow as yeasts. These colonies are
smooth. There is a reduced production in color, the colonies appearing
cream/light-tan/light-pink in color. Microscopically, sausage-shaped
cells are mixed with hyphae-like structures. As the culture ages,
segments begin to form.

21. 1. Inhalation of spores.
2. Engulfment by macrophages.
 Superoxide dismutases (SODs) like zinc superoxide dismutase
‘soda.
3. conversion from mycelium to yeast form
GTPase.
heat-shock proteins.

22. • Inhalation of spores.

23. • Engulfment by macrophages
Since, the P.marneffie is a facultative intracellular pathogen, it survives in the phagosome
and replicates as yeast cells here. In order to protect itself from the enzymes of phagosomes
and host defense mechanism, the Superoxide dismutases (SODs) like zinc superoxide
dismutase ‘sodA’ is released which converts superoxide radicals into hydrogen peroxide and
oxygen molecules.

24. • Conversion from mycelium to yeast form
Gtpase:
Regulates the cell membrane transport and mitotic processes in fungi
which facilitate in yeast like growth.
Heat shock proteins:
Under stressful conditions such as heat shock, ph shift or hypoxia,
increased expression of hsps protect the cell by stabilizing unfolded
proteins, giving the cell time to repair or re-synthesize damaged proteins

25. • The disease caused by it is called penicilliosis marneffein.
• characterized by fever, anemia, weight loss, lymphadenopathy,
hepatosplenomegaly, respiratory signs, and skin lesions.
• less significant medically.
• related to south Asian countries.

26. • VECTOR
in internal organs of the R. sinensis (shown below) and Rhizomys
pruinous senex
• HOSTS
Humans and rodents

27. • Living in South Asian countries
• No definite path known
• inhalation or ingestion of spores
• Travelling to South Asian countries
• Contact with people living in South Asian countries
• With weak or immunocompromised persons (HIV or AIDs patients)

28. • AMPHOTERICIN B
can be -static or –cidal
binds to sterols (ergosterol,) in the cell membrane of the fungi and creates a
transmembrane channel, and the membrane undergoes slight change in its permeability
and leakage of intracellular components occurs.
ultimately cell death
• ITRACONAZOL
Traconazole interacts with 14-α demethylase, a cytochrome P-450 enzyme necessary to
convert lanosterol to ergosterol.
inhibition of its synthesis results in increased cellular permeability causing leakage of
cellular contents.
may also inhibit endogenous respiration, interact with membrane phospholipids, inhibit
the transformation of yeasts to mycelial forms, inhibit purine uptake, and impair
triglyceride and/or phospholipid biosynthesis

29. • Melanin is found in diverse species and have been implicated in
virulence in human fungal pathogens.
• P.marneffie conidia and yeast cells produce melanin o melanin-like
compound in vivo.
• P.marneffie also produce and secrete brick-red diffusible water
soluble pigment, during growth at temperature below 30 degrees
Celsius.
• The unique pigment production by this fungus may help to better
understand certain biological aspects of this pathogenic fungus.
• It generally diffuse in commonly used media like Sabouraud
dextrose agar and malt extract agar, and does not produce pigment
in observable amounts when the fungus is cultured at temperature
higher than 30 degrees Celsius

30. • P.marneffei is the only Penicillium having thermal dimorphism characteristic,
• due to this characteristic it can act as pathogen in animal cells and human.
• It contain enzymes which cause pathogenicity when survive in human body at
temperature is 37 degree C.
• The infection is spread widely in form of Penicilliosis in East Asian countries due to
occurrence of HIV.
• The patients who are infected with Penicilliosis should be treated with great care
proper treatment and diagnosis are not quickly managed so it is necessary to manage a
frequent administration for proper diagnosis so people treated as soon as possible
• and epidemiology is unknown.
• The researches highlighted the mode of transmission the infection spread by soil and
rats or conidia.
• It is necessary more researches are done in order to control this infection.