MCB 100 Lecture 16

• Penicillium – species of rapidly growing molds with networks of multinucleated, septated hyphae that have many brancing conidiophores with chains of conidia sprouting from the ends. They make diverse metabolites.  

They come in different forms for different uses such as: 

•  penicillium camenberti, used to make camenbert and brie cheese 

•  P. chrysogenum (penicillin antibiotic)  

• Aspergillus are a species of rapidly growing aerobic molds with branching septate hyphae and characteristic conidia on the conidiophore. Over 60 species are medically relevant pathogens, most of these produce mycotoxins such as aflatoxin causes cirrhosis of liver 

• Aspergilus fumigatus and A. clavatus are major allergens, associated with allergic bronchial pulmonary aspergillosis sinus and respiratory disease 

• Candida species are diploid fungi that grow as both yeasts and filamentous (with hyphae) forms. The fungi undergo a reversible process of phenotypic switching, in which environmental regulation of genes and spontaneous gene switching (turningoff/on) generates different morphologies 

• C. albicans is part of normal microbiota, it is also the causal agent of the opportunistic oral (thrush) and genital (vaginitis) infections, or sometimes systemic infections candidiasis.  

• C. aurus is an emerging global health threat causing outbreaks of severe disease, it is multidrug resistant. It is also often mistaken/mididentified for C. albicans 

• Blastomyces species are dimorphic fungi that exist in soil as a filamentous forms with conidia (spores) that form directly on the wall of the hyphae (no fruiting body forms) 

• The spores are inhaled and then germinate at 37C into the yeast form in the lungs  

• Histoplasma species are thermally dimorphic fungi that grow as a brownish mycelium externally and as a yeast form at 37C 

• H. capsulatum is endemic in the Midwest where it is associated with dry, dusty soil and bird and bat droppings  

• Most of the infections have no clinical manifestations, when symptoms do occur, they are flu like  

• Pneumocystis species are yeast like fungi that have complex life cycles taking place entirely in the alveoli of the lung,  

• The trophozoite (feeding of vegetative stage) swells to become up to 8 sporozoites (precyst stage) which develop into a cyst.  

• When the cyst matures, it opens and releases the sporozoites, which enlarge, reproduce and mature into trophozoites. Transmission is person-to-person by air droplets 

• P. jiroveci causes lethal pneumonia, associated with immunocompromise and peoples with AIDS.  

• Coccidioides species are dimorphic with a unique life cycle.  

• Outside the body they exist  

• Trichophyton species are dimorphic fungi that exist in soil and moist environments as a filamentous form with conidia (spores) that form directly on the hyphae (no fruiting body forms) 

• Athlete’s foot and jock itch – usually infections start with the foot, but it can spread to other areas such as the groin, where is manifest as an itchy reddish rash