Upload
belinda-dickerson
View
215
Download
0
Tags:
Embed Size (px)
Citation preview
Introduction to Mycology
Nov. 30, 2015
Bob Slinger, MD, Division of Infectious Disease, CHEO
Objectives231 Recognize the morphological characteristics
of yeasts and filamentous fungal pathogens
232 Recognize the clinical classification, common etiology and impact of human mycoses including superficial, cutaneous, sub‐cutaneous and disseminated infections.
233 Discuss the available treatment options and mechanisms of action of anti‐fungal agents including amphotericin B, the azoles, and echinocandins.
Fungi: eukaryotic= nuclear membrane
Rigid cell wall
Fungal Morphology 12 basic morphological forms: yeasts and
filaments (hyphae)
Yeasts- unicellular, round to oval, reproduce by budding
Hyphae: multi-cellular, groups of hyphae called molds (produce infectious round or oval spores called conidia, these are not yeast)
Dimorphism: fungus can exhibit either the yeast form or the filamentous form (e.g. histoplasmosis)
Hyphae Conidia (Spores) Yeasts
http://www.atsu.edu/faculty/chamberlain/Website/Lects/Fungi.htm
HyphaeIntracellular yeasts.
Who is at risk for Fungal Infections? Some fungi able to affect healthy persons Those with impaired innate immunity: eg change in
Normal bacterial flora caused by antibiotic therapyThose with impaired cellular immunity due to
diseases or medications eg neutropenia caused by leukemia or chemotherapy
for cancerThose with impaired cell mediated immunity eg due
to steroid use ( asthmatics receiving inhaled steroids) or due to diseases that affect T cells eg HIV
Classification of Fungal InfectionsAnatomically, based
on depth of invasionsuperficial cutaneous subcutaneous systemic
Host FactorsCalled
opportunistic/
non-opportunistic= Healthy host vs
non-healthy host)
Superficial Mycosesinfections limited to the
outermost layers of the skin and hair
no invasion of deeper tissues, so no inflammation and no symptoms
E.g Tinea versicolor: Malassezia species
hypopigmented macules, “spaghetti and meatballs" appearance of organism in skin scrapings
Hyphae and conidia
Case: Child with multiple pink circular lesions, itchy, scaly borders, lives on farm, no tick bites
What is diagnosis?A) Lyme disease B) BlastomycosisC) Ring wormD) Candidiasis
Cutaneous Mycoses: Dermatophytesextend deeper into epidermis, or into hair
and nailscellular immune responses may occurinflammation and symptoms (itching,
burning) caused by diseases are referred to as ringworm
identified by appearance +/- microscopic exam and culture
Tinea unguium
Tinea pedis (Athlete’s foot)
What is diagnosis? A) CoccidioidomycosisB) AspergillosisC) Tinea manusD) Sporotrichosis
Fungal culture from biospy of skin nodule: Sporotrichosis
Conidiophores and conidia of the fungus Sporothrix schenckii
http://pathmicro.med.sc.edu/mycology/mycology-6.htm
Subcutaneous Fungal Infectionse.g. Sporotrichosisinvolve the dermis, subcutaneous tissues,
muscle and fascia most infections are chronic initiated after organism is implanted in skin
by trauma spread by lymphatic systemdifficult to treat, surgical excision e.g. Sporotrichosis: Sporothrix schenckii,
from plant thorns, nodules and ulcers along lymphatics at site of inoculation
.
What is diagnosis?A) BartonellosisB) HistoplasmosisC) Anaplasmosis D) Blastomycosis
Systemic Fungal InfectionBlastomyces dermatitidis: Manitoba,
Northern Ontariousually lung, rare cases of localised skin or
bone lesions
Systemic Fungal Infection agents are inherently virulent, able to
evade host defencesprimary focus of infection is the lung secondary infection may occur
elsewhere in the bodyBlasto, histo, coccidioidomycosis are
top 3May also referred to as “dimorphic” or
“geographic” fungi
Systemic: Dimorphic
Grow as hyphae in environment, but as yeast in humans
Pathogenicity: ability to survive and multiply within phagocytic cells
e.g. Blastomycosis, histoplasmosisHistoplasmosis: bird or bat droppings and soil
central Canada, St. Lawrence valleylocalised lung disease in most patientsdisseminated disease may occur in
immunosuppressed patients
Case: Patient with Leukemia A 4 year old boy with
leukemia develops prolonged fever and neutropenia
Later complains of difficulty eating, and then blurring of vision
Physical exam shows pharynx on right
CT scan of abdomen and photo of fundus are abnormal
CT of abdomen showing multiple lesions. Endoscopic view on right. N Engl J Med 2007; 356:e4January 25, 2007DOI: 10.1056/NEJMicm040112
Fundus ExamWhat fungal
infection do you suspect?
A) AspergillosisB) BlastomycosisC) CandidiasisD) Leptospirosis
Opportunistic Infections: CandidaCandida infections occur
with physiological normal flora disruptions e.g. vaginal candidiasis
as a result of antibiotic therapy disrupting normal flora e.g. Pharyngeal Thrush
in neutropenic patients – disseminated candidiasis
Opportunistic InfectionsCan be yeasts ( Candida) or hyphae (molds)infections in patients with immune
deficiencies, or impaired host defences HIV Alteration of normal flora Diabetes mellitus Immunosuppressive therapy Malignancy Newborns/infants
Satellite lesions
Opportunistic Molds: Aspergillusubiquitous in environment, particularly
spreads during building renovationsinvasive disease in patients with neutropenia,
post-transplant patientsother manifestations: allergic (Allergic
Bronchopulmonary Aspergillosis)www.aspergillus.man.ac.uk
Aspergillosis: AngioinvasionHyphae in blood vessel wall, leads to
infarction
Opportunistic Molds: Mucormycosis,similar to Aspergillus, leads to severe disease in neutropenic patients
Antifungal AgentsAmphotericin B, Lipid Amphotericins
bind to ergosterol in the cell membrane, causing leakage
Azoles : block ergosterol synthesis e.g. fluconazole, voriconazole, posaconazole
Echinocandins (e.g. caspofungin): block glucan synthesis in cell wall
Echinocandins Azoles and Amphotericin
Lab Diagnosis of Fungal InfectionsSpecify on requisition when fungal cultures
required; put down names of suspected agents if possible
Lab will look for fungal elements hyphae and yeast Bacterial gram stain will show yeast (Candida) as
wellCulture on special media (some will grow on
media used for bacteria e.g. candida)Antigen and antibody tests in some cases: send
out to Provincial Lab or to USA for special tests ( can discuss these with Infectious Diseases )
Fungal Infection: Treatment and PreventionSanford Guide to Antimicrobial Therapy -
recommended for treatment informationPrevention:
antifungal medications given to some high risk patients e.g. some leukemia and transplant patients on fluconazole
infection control measures used in hospital to prevent aspergillus inhalation, masks to prevent high risk environmental exposure
Thank you