MEDICALLY IMPORTANT
FUNGI and ANTIFUNGAL
THERAPY
DR. BREIDA BOYLE
INTRODUCTION
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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
INTRODUCTION
MYCOSES
 MUCOSAL: limited to mucosae
 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
PATHOGENIC FUNGI
TRUE
PATHOGENS
OPPORTUNISTIC
PATHOGENS
TRUE PATHOGENS
Cutaneous infective agents
Subcutaneous infective agents
Epidermophyton species
Microsporum species
Trichophyton species
Actinomadura madurae
Cladosporium
Madurella grisea
Phialophora
Sporothrix schenckii
Systemic infective agents
Blastomyces dermatitidis
Coccidioides immitis
Histoplasma capsulatum
Paracoccidioides brasiliensis
OPPORTUNISTIC
PATHOGENS
Absidia corymbifera
Aspergillus fumigatus
Candida albicans
Crytococcus neoformans
Pneumocystis carinii
Rhizomucor pusillus
Rhizopus oryzae (R.arrhizus)
PATHOGENIC FUNGI
TRUE
PATHOGENS
OPPORTUNISTIC
PATHOGENS
CLASSIFICATION OF FUNGI
Depends on :
 Characteristic Structures
 Habitats
 Modes of Growth
 Modes of Reproduction
 Clinical Setting
 DNA Homology
Cell Wall and Membrane
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Composed mainly of chitin rather than
peptidoglycan (bacteria)-so unaffected by
antibiotics
 Cell Wall also has glucans and Mannans
 Chitin: consists of a polymer of Nacetylglucosamine
 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
Cell Membrane
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The imidazole antifungal drugs
( clotrimazole, ketoconazole, miconazole)
and the triazole antifungal agents
(fluconazole , itraconazole, voriconazole)
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
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
MODES OF FUNGAL
GROWTH
FILAMENTOUS
MOLDS
UNICELLULAR
YEASTS
However there are some dimorphic fungi ( they switch between these
Two forms depending on their environment)
Filamentous (mold-like) Fungi
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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
YEAST like FUNGI
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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
REPRODUCTION
SPORULATION
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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
ASEXUAL SPORULATION
(MITOSIS)
Colour of a particular fungus seen on bread, culture plate is due to the
Conidia, easly airborne and disseminated
SEXUAL SPORULATION
meiosis
Relatively rare compared to asexual sporulation, and spore shape often
Used as a method of identification
CUTANEOUS MYCOSES
-DERMATOPHYTOSES
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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
PATHOLOGY
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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
do not invade underlying non-keratinized
tissues
CLINICAL SIGNIFICANCE
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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
Tinea pedis(Athlete`s foot)
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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
Tinea corporis( Ringworm)
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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
Tinea capitis( scalp ringworm)
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Trichophyton and
Microsporum species
Depends on area
Small scaling patches to
involvement of entire
hair with hairloss
Microsporum infects
hair shafts , Wood`s
lamp
More common in
children due to medium
chain fatty acids(C8-120
in sebum
TINEA CRURIS/UNGUIUM
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Epidermophyton ,
Trichophyton rubrum,
simliar to ringworm but
thighs and genitalia
 Trichophyton rubrum,
nails thickened
discoloured and brittle ,
Onchomycosis
Treatment for months until
all of the infected nail
grows out and is
trimmed off
Tinea vesicolor
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Pityrasis vesicolor
 Due to Malassezia furfur or Pityosporium
orbiculare
 Treatment , ketoconazole, fluconazole ,
itraconazole
Diagnosis of Dermatophyte
Infection
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Nail clippings, skin scrapings, Hair /follicile
No role for swabs
Placed in sterile container preferably or between 2
slides
KOH will be added in the lab to dissolve tissue
material
Lactophenol blue stain to see if fungal hyphae seen
For full identification culture on selective media
required e.g addition of cycloheximide or
chloramphenicol, low ph 5.0
May Require 10-14 days for growth
Macroscopic and microscopic identification of
colonies
Fungal elements/hyphae
T.mentagrophytes
T.mentagrophytes
Treatment
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Samples to be sent for fungal staining and culture
 Infected skin may be treated with topical
application of antifungal agents
miconazole,nystatin and clotrimazole
 Refractory lesions oral griseofulvin and
itraconazole, terbinafine
 Infections of hair and nails usually require
systemic ( oral) therapy
SUBCUTANEOUS
MYCOSES( dermis, subc
tissues and Bone)
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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
Sporotrichosis
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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 species
Mycetoma
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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
SYSTEMIC MYCOSES
Systemic infective agents
Blastomyces dermatitidis
Coccidioides immitis
Histoplasma capsulatum
Paracoccidioides brasiliensis
Opportunistic fungal
Pathogens
Absidia corymbifera
Aspergillus fumigatus
Candida albicans
Crytococcus neoformans
Pneumocystis carinii
Rhizomucor pusillus
Rhizopus oryzae (R.arrhizus)
Eastern US
Males
Diagram of Systemic mycoses(dimorphic, yeast in infective tissue)
Clinical significance
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Simliar to Tuberculosis in that
asymptomatic 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
Coccidiodomycosis
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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
Histoplasmosis
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AIDS patients at particular risk
Treatment : Amphotericin
or Itraconazole
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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)
OPPORTUNISTIC
PATHOGENS
Absidia corymbifera
Aspergillus fumigatus
Candida albicans
Crytococcus neoformans
Pneumocystis carinii
Rhizomucor pusillus
Rhizopus oryzae (R.arrhizus)
OPPORTUNISTIC MYCOSES
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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
CANDIDIASIS(candidiosis)
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Candida albicans and other candida species
which are normal flora in the mouth, skin ,
vagina and intestines
 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
Risk Factors for Candida
Infection
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Cellular
Immunodeficiency
Antibiotic Use
Moisture area
Age
Hormonal Influence
General debility
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Interference with
Normal flora
Mechanical factors
Pregnancy
Oral Contraceptives
Diabetes mellitus
Administration of
corticosteroids
Vulvovaginal candidiasis
Treatment miconazole, clotrimazole topically or oral fluconazole
Or itraconazole
Candida wet preparation
Candida species-Gram stain
Candida culture-24 hours
Mucosal Candidiasis
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Pain, redness and sometimes a whitish
coating or discharge of the mucosa
 Oral candidiasis
 Nappy rash candidiasis
 Vaginal candidiasis
 Esophageal Candidiasis
 Chronic form
MUCOCUTANEOUS
CANDIDIASIS
Cellular deficiency results in chronic mucocutaneous candidasis
Oral Candidiasis
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Occurs in infants without any predisposing
factors
Usual predisposing factors
Seen in patients taking antibacterials
Pain, redness and sometimes a whitish coating
or discharge of the mucosa
Candida present in small numbers on the
mucosa and the problem arises when it
overgrows
Eosophageal Candidiasis
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Orophargneal candidiasis may progress to
eosophageal candidiasis
 Manifestataion of AIDS
 Also occurs in those who have predisposing
factors but are HIV-negative
 Treatment: fluconazole,itraconazole,
voriconazole or amphotericin
Vaginal Candidiasis
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May occur without any obvious predisposing
factors
May occur frequently
Treatment:
Creams and ointments: Clotrimazole 1% ,
Miconazole 2%
Tablets/Pessaries: Clotrimazole, Miconazole,
Terconazole, Nystatin
Oral Therapy: Fluconazole, Itraconazole
NAIL CANDIDIASIS
Paronychia
Oral therapy-fluconazole etc
DISSEMINATED
CANDIDIASIS
Treatment amphotericin or fluconazole
Severe candida Infections
May cause candidaemia,
opthalamitis, hepatosplenic
candidiasis,
Line infections, secondary
peritonitis and urinary tract
infections in
Hospitalised patients
As well as mucosal candidiasis
Of Note: candida may
contaminate sputum specimens
CRYTOCOCCOSIS
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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
CRYTOCOCCUS
NEOFORMANS
In Aids patients it is the second most common fungal infection
after candida , potentially the most serious
Treatment: Amphotericin and flucytosine for meningitis and if AIDS
Subsequent suppression with fluconazole
ASPERGILLOSIS
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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 outbreaks n hospitals with
construction work
Disease presentation depends on immunologic
status of patient
Disease caused by
Aspergillus
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Allergic Bronchopulmonary Aspergillosis
 Farmer`s lung
 Invasive Aspergillosis
 Aspergilloma
Aspergillus fumigatus
Disease caused by
Aspergillus
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Allergic Bronchopulmonary Aspergillosis:
in this condition the mould colonises the
mucosal surface of lower respiratory tract
but does not invade the mucosa. There is
intense hypersensitivity response to the
Aspergillus antigens> impairment of lung
function. Associated abnormal findings on
X-ray and asthma like symptoms
Farmer`s Lung
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Syndrome of shortness of breath typically
occuring several hours after exposure to
mouldy hay. Antibodies (IgG not IgE) form
a precipitate with aspergillus antigen in the
alveolar walls and an inflammatory cascade
is initiated
Allergic Aspergillosis
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Relatively rare, can arise from inhalation of
spores, without subsequent extensive spore
germination hyphal invasion
 The allergic reaction results in bronchial
constriction
 Diagnosis by immunoelectrophoresis
ASPERGILLOSIS
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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
ASPERGILLOMA
Diagnosis in the lab by staining and culture: characterisitic V-shaped
Hyphae, Septated and spore forming structures
Treatment Surgical removal of mass and amphotericin
Risk of massive haemoptysis
INVASIVE ASPERGILLOSIS
INFECTION
Often treated empirically, using risk assessment and
CT(spiral) to assist in diagnosis
Treatment Amphotericin( or voriconazole) and supportive therapy
NEJMED 2002 Aug 8:347(6);408-15
MUCORMYCOSIS
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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
abunance 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
MUCOR
MYCOSIS/RHIZOPUS
Rhinocerebral Mucormycosis
Infection begins in the nasal mucosa or sinuses and progresses to the
Orbits, the palate and the brain
Treatment: Surgical debridement of necrotic tissue , correction of
Underlying disorder and Amphotericin
RHIZOPUS from Skin
Scrapings
PNEUMOCYSTIS CARINII
PNEUMONIA (PCP)Now
known as PNEUMOCYSTIS
JIROVECI Frenkel 1999
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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
diseases of individuals with HIV-1 and usually
fatal if untreated
 It does not contain ergosterol and is extremely
difficult to culture (requires )cultured
PCP
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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
Pneumocystis carinii in Alveoli
Treatment: Combination sulfamethoxazole and trimethoprim,
Pentamine and additional agents may also be used
Can be used prophylaxically to prevent infection
Pneumocystis carinii
(jiroveci) pneumonia
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
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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
LABORATORY DIAGNOSIS
OF FUNGAL INFECTIONS
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Meningitis: Cerebrospinal fluid for
Lactophenol 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
LABORATORY DIAGNOSIS
FUNGAL INFECTIONS
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Types of tests carried out
Fungal Staining – Lactophenol blue staining or
wet prep using KOH to dissolve tissue material or
Calcofluor (fluorescence stain)
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
Molecular Methods not used on a routine basis
on samples(as yet)
MANAGEMENT OF FUNGAL
INFECTIONS
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Some such as superfical skin infections require
topical therapy only with cream e.g.miconazole
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. fluconazole i./v or amphotericin,
voriconazole
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
Antifungal Agents: Families
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Azoles
Imidazoles
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Triazoles
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Polyenes Macrolides
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Pyrimidines
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Lipopeptides
Allylamines
Benzofurans
Ref: Antifungal Drug Resistance. Clinical Infectious Diseases. 2003:36
(Suppl 1) s31-41.
Azoles

Azoles
Imidazoles Triazoles
 Causes Inhibition of Clansterol 14 α
demethylase, (an enzyme
required for the
synthesis of ergosterol)
by binding to
cytochrome P450
 Resistance may be
intrinsic or acquired
Voriconazole
Allyamines

Inhibits squalene
epoxidase, an enzyme
essential for synthesis
of ergosterol
 Drug acculmulates in
nails, skin and fat
 Very useful for nail
infections
Polyene Macrolides
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Amphotericin, nystatin
Antifungal activity by
binding to membrane
sterols such as ergosterol
and they increase
membrane permeability
and leads to cell death
Higher concentrations
inhibits Chitin synthase
Active against
Aspergillus spp, Candida
species ,Crytococccus
neoformans ,
Zygomycetes etc
Amphotericin

Numerous forms
 Pastilles, Parenteral forms: amphotericin B,
deoxycholate form, colloidal form, Liposomal
form
 Toxicity: Dose dependent reduction in GFR, by
direct vasoconstritive effect on afferent renal
arterioles, destruction of renal tubular cells and
basement membrane and loss of functioning
units
 Also nausea .vomiting, phlebitis and ACUTE
REACTION: fever,chills,tachyapnea
Pyrimidines
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Fluorine analogue of a
normal cell constituent
cytosine
Demination results in 5fluorouracil, to 5flurodeoxyuridylic acid
monophosphate, a noncompetitive inhibitor of
thymidylate synthetase
Used particularly in
crytococcal meningitis74% of serum levels
Benzofurans
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Griseofulvin
 Inhibits nucleic acid synthesis, macrotubule
formation and chitin formation
 Active against ringworm, not candidia or
tinea versicolor
Lipopeptides

Echinocandins, derivatives of pneumocandin
BO
 Inhibition of 1,3-ß- glucans in the fungal wall,
that is glucan synthase inhibitor
 Active candida, aspergillosis and pneumocystis
carinii in vitro
 Licensed for refractory candida( esophageal)
infections and invasive Aspergilllosis