M20- Fungi- candida Flashcards
Describe fungi.
- Eukaryotes (nucleus, organelles, etc)
- Ubiquitous (saprophytic or parasitic)
- > 200 pathogenic species
what characteristics vary in fungi?
– propagation may be sexual or asexual (meiosis/mitosis)
– unicellular or filamentous vegetative structures
– Budding, binary fission etc
– surrounded by a chitin cell wall
what does not work on eukaryotes?
antibodies
what are the 4 genres of fungi responsible for 90% of deaths?
- Candida
- Crytpococcus
- Apergillus
- Pneumocystis
what are common fungi conditions?
- Athletes foot
- Ringworm
- Vulvovaginal candidiasis
- Aspergillosis
what are two forms of fungi?
- dimorphic
- polymorphic
what is yeast?
single oval cells often reproduce by budding
what is mould?
multicellular and composed of tubules or filaments called hyphae
What is the name for a mass of hyphae?
mycelium
what is carriage rate of candida?
35%
what is the commonest fungi found in the mouth?
Candida species
What is the reservoir for candida?
dorsal of the tongue
what are two main species of candida?
- C. albicans
- C. glabrata
how is Candida albicans found?
spherical or oval budding yeast :
- single cells or blastospores
- Pseudohyphae and true hyphae
what does Candida albicans form round?
thick-walled resting structures
-chlamydospores
where does Candida albicans colonise?
- Mouth
- GI tract
- Skin
- Female genital tract
what is pseudohyphae?
nuclei separated and small perforation in cell walls
what is true hyphae?
no cross wall and is more susceptible to fragmentation
what are the types of superficial candidosis (pseudomembranous candidiasis PMC)?
Mucosal infection (thrush) Other skin infections: -Interigo (pustules that rupture ) -Nappy rash -originating from GI tract -Paronychia -infection of nails -HIV infection - Candida infection frequent
what are superficial candida infections?
effect mainly the skin and epithelial surfaces
what are mucocutaneous candida infections?
involve both the skin and the underlying mucosa
Describe chronic mucocutaneous candidosis?
• Rare, but difficult to treat
• Persistent infection of mouth &/or mucosal
surfaces
• Skin and mucosa are involved
• Usually a consequence of damaged host immune system or metabolism
• CMC sometimes seen with T-cell deficiency
• Systemic antifungal therapy required
what are systemic or deep infections?
occur in major organs following Candidaemia (i.e blood infection)
what happens if systemic or deep infections go untreated?
Untreated disseminated disease is fatal
what is the initial infection of systemic candidosis?
– Lower respiratory tract &/or urinary tract
– Candidaemia, (Candida in the blood)
– fungi migrate;
• endocardium, meninges, bones, kidneys or eyes
what are risk factors of systemic candidosis?
– seriously ill patients
– heart surgery, long term immunosuppression or drug therapy
what are the causes of erythematous candidiasis?
• Denture Wearing – Most common • Prolonged Drug Therapy – Antibiotics – Topical steroids • Persistent PMC – Underlying problem • AIDS Patients
what is identification of Candida species aided by?
chromogenic media
-chemicals in broth produce different coloured colonies for different species
Discuss the presentation of erythematous and denture related candidosis.
red swollen inflamed mucosae
-usually limited to area of an upper denture
Describe the cause of erythematous and antibiotic sore mouth.
– Suppression of normal oral bacterial flora
– overgrowth by C.albicans
– usually broad spectrum
antibiotics
– especially tetracycline and consequent mucosa of tongue and cheeks becomes thin, inflamed and atrophic
what is the treatment for Erythematous & Denture related candidosis?
– topical antifungal agents,
– cleaning denture
– removing denture at night
what is angular cheilitis?
Erythema and fissures in the angulum oris
– Overgrowth of C. albicans at the angle of the mouth
where is angular cheilitis usually seen in?
– denture wearers,
– vitamin deficiencies
• iron and vitamin B12
when can superinfection occur (angular cheilitis)?
Superinfection with S.aureus other species may also occur
how is angular cheilitis treated?
– antifungal agent
– resolving underlying problem
Describe chronic hyper plastic candidosis (candidal leukoplakia)
• Individual lesions • White patches cannot be rubbed off • Red/white speckled patches can occur • Surface parakertainized & hyperplastic • 5-11% can become malignant • C. albicans role not clear
what are the risk factors of chronic hyper plastic candidosis?
– Smoking,
– folic acid or Iron deficiency
what are the risk factors of candidal leukoplakia?
- Denture Hygiene (Trauma, chronic irritation)
- Medications
- Immunosuppression
- Xerostomia
- Endocrine disfunction
- Moisture/Poor hygiene
- Smoking (co-factor)
- Blood Diseases
Describe the adherence virulence factor of C. albicans.
– Hyphal-form more adhesive (acrylic)
– Hydrophobic surface
– Specific Adhesins
– Fibrillar mannoprotein
Describe the host defences/damage.
-Proteinases (SAPs)
– Phospholipase
– Concentrated at Hyphal tip
what is the change in shape of yeast to pseudohyphae to hyphae linked to?
disease process
Name 2 common anti fungal agents.
Polyenes - bind ergosterol in membrane
Azoles - interfere with ergosterol production
what anti fungal agent has anticandidal activity ?
Chlorohexidine
what is the role of polyenes (anti fungal agent)?
integration into cell membrane.
Example: Nystatin
what is the role of azoles (anti fungal agents)?
interruption of sterol biosynthesis ( cell and mitochondria membranes)
Example: Miconazole and fluconazole
Describe the action of Nystatin (polyenes).
- Effective against all Candida species
- Resistance rare
- Binds to ergosterol in fungal lipid membrane – makes membrane leaky
- Topic application only
what is miconazole an inhibitor of?
ergosterol formation
how is miconazole used systemically?
– Miconazoletaken absorbed by GI tract – Fluconazolesecretedin saliva – C.albicans – Candidaspeciesoften resistant
When are patients resistant to miconazole?
long term HIV therapy
what anti fungal resistance is most common?
azoles
Give example of azole resistance.
- Candida glabrata (azalea resistance mechanism)
- Candida krusei (intrinsic resistance to azoles)
- Candida auris (intrinsic resistnace)
