Paecilomyces variotii

Bainier, 1907

What isPaecilomyces variotii?

Paecilomyces variotiiis a wide-distributed mold that is readily found in composts and soils and a ubiquitous contaminant of foods and raw materials. It belongs to the genusPaecilomyces, most of which are important as soil fungi and insect pathogens.P. variotiiis one of only a few common food contaminants inPaecilomycesspecies. The genus was split from thePenicilliumgenus due to morphological differences in conidia and phialides (conidia-bearing structures) (1,2).

Paecilomyces variotiimorphology

Paecilomyces variotiihas rapidly growing colonies, colored consistently brown to greenish-brown. The colonies are flat, powdery to leathery, and funiculose (rope-like strands) or tufted surfaces.P. variotiicolonies are fast-growing and can mature within three days. The conidia-bearing structures consist of loosely branched and irregularly brush-like conidiophores with tapering phialides at the tips. Conidia are single-celled, hyaline, and positioned terminally in chains (Fig. 1)。

Paecilomyces variotii under the light microscope

Figure 1. Paecilomyces variotii under the light microscope (Photo source: Medmyco, Wikipedia).

The species is thermophilic and xerophilic.P. variotiicultures don’t grow below 5 °C (41°F) and can withstand temperatures above 80–100 °C (176–212 °F) only for a short while. Its optimum growing conditions lay between 35–40 °C (95–104°F). It requires 0.8 water substrate activity (aw=0.8) (1).

Paecilomyces variotiiecology

Paecilomyces variotii是高温,温度高的速度增长s 50–60 °C (122–140 °F) normally. It is also able to withstand short periods at boiling temperatures. This is why this species is a frequent contaminant of food products, especially beverages such as sauces and fruit juices – it can survive pasteurization or other heat-treatments (3).

Another reason why this species is a common contaminant is its resistance to sorbate, which is commonly used as a food preservative. It also is often associated with oily products, such as margarine, edible oils, bacon, coconut, peanut beans, and raw materials containing oil.P. variotiican also be isolated from non-food items such as compost, rubber, glue, urea-formaldehyde foam insulation, and creosote-treated wooden poles (1,3).

Paecilomyces variotiireproduction

Paecilomyces variotiiis a heterothallic species, meaning it can reproduce sexually and requires two types of strains (+) and (-) strains to combine to produce the sexual state.Byssochlamys spectabilisis the reported sexual state ofP. variotii.Because the ascospores of the sexual state are strongly heat-resistant, it is often that they are the reason for the spoilage of heat-treated food products (3).

Paecilomyces variotiias a human pathogen

Paecilomycesspp. were not viewed as a frequent causative agent of human diseases; however, they are now considered an emerging agent of opportunistic diseases.P. lilacinusandP. variotiiare implicated in sporadic reports of serious infections, including most organ systems, and this is especially true for immunocompromised individuals. These two species are morphologically very similar and can be distinguished only by growth rates and spore colors. Interestingly, molecular analyses have shown that these similar species are genetically close and belong to two different orders (2,4,5).

These fungi cause opportunistic mycoses type hyalohyphomycosis (infection caused by non-melanized molds, other thanAspergillusspp. orPenicilliumspp.).Paecilomycesare also of clinical interest because of their moderate resistance to antifungal agents. Most cases ofPeacilomycesmycoses are involved with immunocompromised patients and are usually cutaneous or catheter-related. However, there are records of infections connected with most organs in the human body. Reported ocularPeacilomycesinfections are mostly related to contaminations due to ocular surgeries or prolonged use of eye lenses. Peritonitis (inflammation of the abdomen lining) caused byPeacilomycesspp. is connected with continuous ambulatory peritoneal dialysis (2,4).P. variotiihas also been reported to cause sinusitis (inflammation of sinuses) and endophthalmitis (inflammatory condition of the intraocular cavities) (6,7). Wound infection in a transplant recipient and osteomyelitis (bone tissue inflammation) in a patient with the granulomatous disorder as a consequence ofP. variotiiinfection have also been reported (8).

BecauseP. variotiiis commonly found indoors in air samples and dust, carpets, and other textiles, and may be contributing to indoor allergies. It is considered a species characteristic for homes with water damage and is thusly listed in the Group 1 of theERMI(The Environmental Relative Moldiness Index) list of potentially hazardous fungi (11).P. variotiiproduces mycotoxin viriditoxin, which potentially has both myotoxic and hemorrhagic activities in animals. Furthermore, viriditoxin is toxic to insects and other microorganisms (9,10).

References

  1. Pitt JI, Hocking AD. Fungi and food spoilage. Vol. 519. Springer; 2009.
  2. Grossman, C. E. (2005).Paecilomyces: emerging fungal pathogen. Chest, 128(4), 425S.
  3. Houbraken J。,巴尔加,J。,Rico-Munoz, E,约翰逊,S., & Samson, R. A. (2008). Sexual reproduction as the cause of heat resistance in the food spoilage fungusByssochlamys spectabilis(anamorphPaecilomyces variotii)。应用与环境微生物学,74 (5),1613-1619.
  4. Houbraken, J., Verweij, P. E., Rijs, A. J., Borman, A. M., & Samson, R. A. (2010). Identification ofPaecilomyces variotiiin clinical samples and settings. Journal of Clinical Microbiology, 48(8), 2754-2761.
  5. Steiner, B., Aquino, V. R., Paz, A. A., Silla, L. M. D. R., Zavascki, A., & Goldani, L. Z. (2013).Paecilomyces variotiias an emergent pathogenic agent of pneumonia. Case reports in infectious diseases, 2013.
  6. Otčenášek, M., Jirousek, Z., Nožička, Z., & Mencl, K. (1984).Paecilomycosisof the Maxillary Sinus: Paecilomykose der Kieferhöhle. Mycoses, 27(5), 242-251.
  7. Lam, D. S., Koehler, A. P., Fan, D. S., Cheuk, W., Leung, A. T., & Ng, J. S. (1999). Endogenous fungal endophthalmitis caused byPaecilomyces variotii. Eye, 13(1), 113-116.
  8. Cohen-Abbo, A., & Edwards, K. M. (1995). Multifocal osteomyelitis caused byPaecilomyces variotiin a patient with chronic granulomatous disease. Infection, 23(1), 55-57.
  9. Fabiano, R. J., & Tu, A. T. (1981). Purification and biochemical study of viriditoxin, tissue damaging toxin, from prairie rattlesnake venom. Biochemistry, 20(1), 21-27.
  10. Green, P. E., Blaney, B. J., Moore, C. J., & Connole, M. D. (1989). Identification and preliminary evaluation of viriditoxin, a metabolite ofPaecilomyces variotias an insecticide for sheep blowfly,Lucilia cuprina(Wied.). General and Applied Entomology: The Journal of the Entomological Society of New South Wales, 21, 33-37.
  11. Vesper, S., McKinstry, C., Haugland, R., Wymer, L., Bradham, K., Ashley, P., … & Friedman, W. (2007). Development of an environmental relative moldiness index for US homes. Journal of Occupational and Environmental Medicine, 49(8), 829-833.
  12. Featured image photo, Characterization ofPaecilomyces variotiiandTalaromyces amestolkiaein Korea Based on the Morphological Characteristics and Multigene Phylogenetic Analyses – Scientific Figure onResearchGate.

Published:September 28, 2021Updated:October 25, 2021

Dusan Sadikovic

Written by:

Mycologist - MSc, PhD
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Fact checked by:

CPI, CMI, CMR
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Charles Leduc

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