Molds Flashcards
4 main criteria in identifying molds?
1) growth rate in culture
2) presence of a yeast phase (is it dimorphic?)
3) Colonial and microscopic morphology (appearance) *** MOST IMPORTANT
4) biochemical tests
Labs without biological safety cabinets must do what?
NOT work on any mold, except those believed to be dermatophytes
Examination of the hyphae enables classification into three groups
1) septate UNPIGMENTED (HYALINE) ^ majority of important molds 2) deptate PIGMENTED (DEMATIACEOUS) ^ feature brown pigment 3) aseptate wide hyphae (NO SEPTATE) (MUCORALES) ^ lower fungi soemtimes called pin molds
1) Hyaline Molds
hyaline - means “like glass”- thats what they look like under microscope
Aspergillus
&
Penicillum
What is Aspergillus?
produce smokey gray/green colonies and are important causes of fulminant fungal infections in immunocompromised patients
- causes chronic sinusitisand aspergilloma - fungus ball of mold in immunocompromised patients
- ASPERGILLUS - all movet he same way at the same time **
How many species of Aspergillus?
4: fumigatus, niger, flavus, & terreus
Species of Aspergillus? (1)
1) fumigatus: has been incriminated in farmer’s lung
- also causes allergic bronchopulmonary aspergillosis in asthmatics and CF patients
looks purple
Species of Aspergillus? (2)
2) Niger - commonly causes otomycosis
- black, looks like a dandelion
Species of Aspergillus? (3)
3) Flavus - may infect immunocompromised patients and also infects peanuts, producing aflatoxin which is associated with liver carcinoma
- infect peanuts = legumes not actual peanuts
- looks like MEDUSA
Aspergillus FLAvus causes AFLAtoxin***
Species of Aspergillus? (4)
4) terreus
Penicillum
a rapidly growing greenish colony which you often see on moldy bread
- the source of penicillin: bacteria wouldnt grow close to the mold*
- there is one invasive species called Penicillum Marneffei
2) Dermatophytes Molds
- large group of fungi infects the skin, hard and nails and is commonly called tinea or ringworm because of its circular appearance
3 species of Dermatophytes
-dermatophytes are commonly associated with human infections - namely Trichophyton (cause superficial skin infections), Microsporum (cigar shaped body) and Epidermophyton (look like antlers)
What is a kerion?
A large mat of infection on the head
- large mat of fungi: huge circular scab
jock itch is caused by what?
trichophyton mentagrophytes
Athletes foot?
- standard - starts between final two toes on foot
- toe jam has anti-fungal in it and not as much as you go from big toe to smallest toe
= why it normally starts there
Tinea Pedis
is athletes foot - 2 types: between toes or ‘mocassin style’ = all over bottom of foot/entire sole of foot
unknown in people who wear shoes = you get it when you’re barefoot but then you put your shoes on and it grows in the moist dark environment of the shoe
Tinea Corpis (Ringworm)
- looks like a circle - thicker outer circle colour
3) Mucorales
- common in the environment (soil and decaying vegetation and cause MUCOMYOSIS - particularly in immunocompromised patients
Where does mucomycosis begin?
in the nose and paranasal sinuses and is one of the most rapidly spreading fungal infections
What are the 4 genera most frequently associated with human infections?
Mucor, Rhizopus, Absidia,and Cunninghamella
Fungal sinusitis?
in debilitated patients with nasogastric tubes
Diagnosis of superficial mold infections
clinical
Diagnosis of deep mold infections?
1) initial detection of hyphae in biopsy specimens
2) culture
3) aspergillus is a common contaminant: diagnosis mainly by biopsy and x-ray
