The genus Paecilomyces may be distinguished from the closely related genus Penicillium by having long slender divergent phialides and colonies that are never typically green. Paecilomyces species are common environmental moulds and are seldom associated with human infection. However, the species, P. variotii and P. marquandii are emerging as causative agents of mycotic keratitis and of hyalohyphomycosis in the immunocompromised patient. Note: Paecilomyces lilacinus has been transferred to Purpureocillium lilacinum (Luangsa-ard et al. 2011).
Morphological Description: Colonies are fast growing, powdery or suede-like, gold, green-gold, yellow-brown, lilac or tan, but never green or blue-green as in Penicillium. Phialides are swollen at their bases, gradually tapering into a rather long and slender neck, and occur solitarily, in pairs, as verticils, and in penicillate heads. Long, dry chains of single-celled, hyaline to dark, smooth or rough, ovoid to fusoid conidia are produced in basipetal succession from the phialides.
Molecular Identification: Molecular phylogeny based on 18S rDNA sequences was done by Luangsa-ard et al. (2004); the genus is polyphyletic.
Key Features: Long slender divergent phialides and culture pigmentation.
References: Samson (1974), Domsch et al. (1980), McGinnis (1980), Onions et al. (1981), Rippon (1988), de Hoog et al. (2000, 2015).
Cultures of P. variotii and P. marquandii showing colony pigmentation.