1. MEDICALLY IMPORTANT FUNGI
DR. BREIDA BOYLE

2. INTRODUCTION
Fungi are a diverse group of sacrophytic and parasitic eukaryotic organisms
Kingdom: Mycota
Of 100,000 fungal species only 100 have pathogenic potential for humans, only a few account for clinically important infections
Mycoses : Human Fungal Diseases
Fungal spores may be important as human allergenic agents

3. INTRODUCTION MYCOSES CUTANEOUS: limited to the dermis
SUBCUTANEOUS : when infection penetrates significantly beneath the skin
SYSTEMIC : when the infection is deep within the body or disseminated to internal organs

4. PATHOGENIC FUNGI
TRUE
PATHOGENS
OPPORTUNISTIC
PATHOGENS

5. TRUE PATHOGENS Cutaneous infective agents
Subcutaneous infective agents
Actinomadura madurae
Cladosporium
Madurella grisea
Phialophora
Sporothrix schenckii
Epidermophyton species
Microsporum species
Trichophyton species
Systemic infective agents
Blastomyces dermatitidis
Coccidioides immitis
Histoplasma capsulatum
Paracoccidioides brasiliensis

6. OPPORTUNISTIC PATHOGENS
Absidia corymbifera
Aspergillus fumigatus
Candida albicans
Crytococcus neoformans
Pneumocystis carinii
Rhizomucor pusillus
Rhizopus oryzae (R.arrhizus)

7. CLASSIFICATION OF FUNGI
Depends on :
Characteristic Structures
Habitats
Modes of Growth
Modes of Reproduction

8. Cell Wall and Membrane
Composed mainly of chitin rather than peptidoglycan (bacteria)-so unaffected by antibiotics
Chitin: consists of a polymer of N-acetylglucosamine
Fungal Membrane contains ergosterol rather than cholesterol found in mammalian cells, use in antifungal agents such as amphotericin which binds to ergosterolpores that disrupts membrane function cell death

9. Cell Membrane
The imidazole antifungal drugs ( clotrimazole, ketoconazole, miconazole) and the triazole antifungal agents (fluconazole , itraconazole) interact with the C-14 α-demethylase to block demethylation of lansterol to ergosterol, vital component of cell membrane and disruption of it`s synthesis results in death

10. HABITAT
All fungi are heterotrophs ( their require some form of organic carbon for growth)
They depend on transport of soluble nutrients across their cell membrane
To do this they secrete degradative enzymes ( proteases etc) into their immediate environment, therefore they live on dead organic material
So Natural Habitat : is soil or water containing decaying organic matter

11. MODES OF FUNGAL GROWTH UNICELLULAR FILAMENTOUS YEASTS MOLDS
However there are some dimorphic fungi ( they switch between these
Two forms depending on their environment)

12. Filamentous (mold-like) Fungi
Thallus (vegetitive body) –mass of threads with many branches resembling cotton ball
Mass: mycelium
Threads: hyphae, tubular cells that in some fungi are divided into segments –septate whereas in other fungi the hyphae are uninterrupted by crosswalls-nonseptate
Grow by branching and tip elongation

13. YEAST like FUNGI
These fungi exist as populations of single , unconnected , spheroid cells, not unlike many bacteria, although they are sometimes 10 times larger than a typical bacterial cell
Yeasts reproduce by budding
Some fungal species particularly those that cause systemic infection exist as dimorphic fungi

14. REPRODUCTION

15. SPORULATION
The principle way in which fungi reproduce and spread within the environment
Fungal spores are metabolically dormant, protected cells, released by the mycelium in enormous numbers
Borne by the air or water to new sites , where they germinate and establish new colonies
Spores can be generate sexually or asexually

16. ASEXUAL SPORULATION (MITOSIS)
Colour of a particular fungus seen on bread, culture plate is due to the
Conidia, easly airborne and disseminated

17. SEXUAL SPORULATION meiosis
Relatively rare compared to asexual sporulation, and spore shape often
Used as a method of identification

18. CUTANEOUS MYCOSES -DERMATOPHYTOSES
EPIDEMIOLOGY
Three genera-Trichophyton, Epidermophyton, Microsporum
Anthropophilic-reside on the human skin
Zoophilic-reside on the skin of domestic and farm animals
Geophilic-reside in the soil
Transmission from humans or animals is by infected skin scales

19. PATHOLOGY Dermatophytes use keratin as a source of nutrition
Therefore they infect skin, hair, nails
All 3 organisms infect attack skin, Microsporum does not infect nails and Epidermophyton does not infect hair, they not invade underlying non-keratinized tissues

20. CLINICAL SIGNIFICANCE
DERMATOPHYTOSES
Characterized by itching,scaling skin patches that can become inflamed and weeping
Infection in different sites may be due to different organisms but is given one name

21. Tinea pedis(Athlete`s foot)
Common organisms are Trichophyton rubrum , Trichophyton mentagrophytes and Epidermophyton floccosum.
Initially between the toes spreads to nails, yellow and brittle
Secondary bacterial infection
Id Reaction

22. Tinea corporis( Ringworm)
Epidermophyton floccosum, Trichophyton, Microsporum
Advancing annular rings with scaly center
Periphery of ring area of active fungal growth, usually inflammed and vesiculated
Non-Hairy areas of trunks mostly

23. Tinea capitis( scalp ringworm)
Trichophyton and Microsporum
Depends on area
Small scaling patches to involvement of entire hair with hairloss
Microsporum infects hair shafts , Wood`s lamp

24. TINEA CRURIS/UNGUIUM
Epidermophyton , Trichophyton rubrum, simliar to ringworm but thighs and genitalia
Trichophyton rubrum, nails thickened discoloured and brittle
Treatment for months until all of the infected nail grows out and is trimmed off

25. Treatment Samples to be sent for fungal staining and culture
Infected skin may be treated with topical application of antifungal agents miconazole and clotrimazole
Refractory lesions oral griseofulvin and itraconazole, terbinafine
Infections of hair and nails usually require systemic ( oral) therapy

26. SUBCUTANEOUS MYCOSES( dermis, subc tissues and Bone)
Causative organisms reside in the soil and in decaying or live vegetation
Almost always acquired through traumatic lacerations or puncture wounds
Common among those who work with soil and vegetation and have little protective clothing
Not usually transmitted humans to humans
Usually confined to tropics and subtropics with exception of Sporotrichosis in USA

27. Sporotrichosis Sporothrix schenckii-dimorphic fungus
Granauloma ulcer at a puncture skin usually a thorn prick and may produce secondary lesions along draining lymphatics
In most disease is self-limiting may exist in chronic form
Treatment oral itraconazole
Chromomycosis : Phialophora or Cladosporium

28. Mycetoma Madurella grisea, Actinomadura madura
Localized abscess usually on the feet, that discharge pus serum and blood
Has coloured grains( compact hyphae) black, white, red or yellow depending on organism

29. Eastern US
Males
Diagram of Systemis mycoses(dimorphic, yeast in infective tissue)

30. Clinical significance
Simliar to Tb in that asymtomatic primary infection is seen whereas chronic pulmonary or disseminated infection rare
In the immunocompetent usually mild and self limiting
In the immunocompromised the same infections can be life threatening

31. Coccidiodomycosis Coccidioides immitis
Most in arid areas of south-western US
In the soil forms arthrospores
Spores airborne , germinate in the lungs and produce sphercules filled with many endospores- new spherule
In disseminated cases lesions in the bone or CNS -meningitis

32. Histoplasmosis Histoplasma capsulatum
In the soil conidia, germinate lungs into yeast-like cells
Becomes engulfed by macrophages and XX
Benign self-limiting or chronic, progressive , fatal
Disseminated disease only fungus intracellular RES parasitism
Area Ohio and Mississippi River area
DX: Culture or Exoantigen (immunodiffusion assay)
AIDS patients at particular risk
Treatment : Amphotericin
or Itraconazole

33. OPPORTUNISTIC PATHOGENS
Absidia corymbifera
Aspergillus fumigatus
Candida albicans
Crytococcus neoformans
Pneumocystis carinii
Rhizomucor pusillus
Rhizopus oryzae (R.arrhizus)

34. OPPORTUNISTIC MYCOSES
Those that affect the immunocompromised but are rare in normal individual
Organ transplantation, post chemotherapy for cancer, immunodeficient due to Aids and congenital immunodeficiency states
Candida species most commonly occurring fungal pathogen in the ICU setting

35. CANDIDIASIS(candidiosis)
Candida albicans and other candida species which are normal flora in the mouth, skin , vagina and intestines
C.albicans is dimorphic
May occur as a results of overgrowth as suppression of bacteria by antibiotics
Manifestations depend on the site e.g. oral candidiasis and vaginal candidiasis and disseminated candidiasis in cancer patients, post GI surgery and AB`s, systemic corticosteroids

36. CRYTOCOCCOSIS Crytococcus neoformans, found worldwide
Especially found in soil containing bird(esp. pigeons) droppings
Characteristic thick capsule that surrounds budding yeast cell –seen Indian Ink
Most common form is mild subclinical lung infection
In the immunocompromised often disseminates to the brain , meningitis often fatal
However half those with crytococcal meningitis have no obvious immune deficiency
bird

37. ASPERGILLOSIS
Several species of genus Aspergillus, mostly Aspergillus fumigatus
Worldwide distribution, ubiquitous
Filamentous molds, produce large numbers of conidiospores
Reside in soil, decomposing organic matter and dust, associated outbreks with construction work
Disease presentation depends on immunologic status of patient

38. ASPERGILLOSIS Acute Aspergillus infections
Most severe and often fatal form of aspergillosis is acute invasive infection of the lungdissemination to brain etc
Less severe form gives rise to a fungus ball( aspergilloma) , a mass of hyphal tissue that forms in lung cavities derived from prior disease

39. Allergic Aspergillosis
Relatively rare, can arise from inhalation of spores, without sussequent extensive spore germination hyphal invasion
The allergic reaction results in bronchial constriction
Diagnosis by immunoelectrophoresis

40. MUCORMYCOSIS
Most often caused by Rhizopus oryzae and less often by other members of the Mucorales such as Absidia corymbifera, Rhizopus pus
Ubiquitous in nature, spores found in great abdunance on rotting fruit and old bread
Usually restricted to those with underlying conditions such as burns, leukaemia or diabetus mellitus
The most common form of the disease can be fatal within a week-Rhino cerebral Mucormycosis

41. PNEUMOCYSTIS CARINII PNEUMONIA
Caused by a unicellular eukaryote, Pneumocystis carinii
Before the use of immunosuppressive agents and the onset of the AIDS epidemic , PCP was a rare disease
It is one of the most common opportunisitic diseasesof individuals treated with HIV-1 and usually fatal if untreated
It does not contain ergosterol and has not been cultured

42. PCP
Various cellular forms encysted group of dormant cells and vegetitive form –trophozoite
Ubiquitous
Activation of preexisting dormant cells in the lungs in immunodeficient persons
The encysted forms induce an inflammination of the alveoli-exudate which blocks gas exchange
Diagnosis by microscopic examination , by silver stain or fluorescence of bronchial washings or biopsy

43. LABORATORY IDENTIFICATION
Standard media –Sabouraud`s agar, potato dextrose agar, low ph 5.0 , inhibits bacterial growth but allows fungal colonies to form
Cultures can be started from spores or hyphae fragments
Specimens: blood, pus, CSF, sputum, tissue biopsies, skin scrapings , nail clippings
Identification by the morphology of conidia structures and carbonhydrate assimiliation tests

44. LABORATORY DIAGNOSIS OF FUNGAL INFECTION
Specimens
Depends on site of infection
Systemic: -Blood culture( really only useful for yeast-low sensitivity) or
- antigen testing e.g.crytococcal and histoplamsosis antigen
Pneumonia: Bronchoscopy washings or brushings for staining and fungal culture or bronchial biopsy

45. LABORATORY DIAGNOSIS OF FUNGAL INFECTIONS
Meningitis: Cerebrospinal fluid for methylene blue staining and indian ink and crytococcal antigen and fungal culture
If Skin infection require skin scrapings
If nail infection require nail clippings
Galactomannan antigen testing for aspergillus infection

46. LABORATORY DIAGNOSIS FUNGAL INFECTIONS
Types of tests carried out
Fungal Staining – methylene blue staining or wet prep using KOH to dissolve tissue material
Fungal culture on media that encourages fungal growth e.g. PDA
Antigen Testing i.e. to test for antigen present in the wall of fungus e.g crytococcal antigen, galactomannan used in serum and CSF samples
PCR not used on a routine basis on samples

47. MANAGEMENT OF FUNGAL INFECTIONS
Some such as superfical skin infections require topical therapy only with cream e.g.nystatin cream
Some require local therpy e.g. pessaries for vaginal candidasis
Some require oral therapy for skin and nail infections up to 1 year e.g. terbinafine
In the immunocompromised systemic therapy required e.g. , voriconazole,fluconazole i./v or amphotericin

48. MANAGEMENT OF FUNGAL INFECTIONS
Important to diagnose fungal infections early in the immunocompromised as there is a high mortality associated with infection
Empirical therapy often started in advance of laboratory diagnosis in these patients