Coniochaeta hoffmannii

Coniochaeta hoffmannii was originally described by J.F.H.van Beyma in 1939 as Margarinomyces hoffmannii.[6] The genus Lecythophora, originally described by John Axel Nannfeldt in 1934, was reintroduced by Konrad Walter Gams and Michael R. McGinnis to accommodate this species in 1983.[7] In 2013, Lecythophora was recombined with Coniochaeta, with all species transferred to the latter genus.[1]

As a former member of the genus Lecythophora, it was considered to be poorly differentiated morphologically.[9] Coniochaeta hoffmannii colonies range in colour from a pale salmon to a pallid orange, with degenerate strains presenting a creamy white colour.[10] Colonies are also flat, smooth and moist.[11] Collarettes are distinct,[10] yet unpigmented, while conidia are also hyaline, smooth, and thin-walled.[11] The production of slimy, orange- to salmon-colored colonies on short adelophialides (phialides lacking a basal septum) with cylindrical collarettes can be quite distinct, with ventricose phialide formations less frequent. Narrow and hyaline, hyphae, through the use of small collarettes,[11] produce conidia directly upon them laterally, directly upon the vegetative hyphae.[9] Alternatively, flask-shaped lateral cells, which are practically cylindrical, can serve as the medium through which conidia are produced; they are sometimes found to be arranged in densely packed groups.[11] Conidia are slightly curved, appearing broadly ellipsoidal to cylindrical to bean-shaped;[9] measurements vary from 3.5–7.0 µm in length by 1.0–2.5 µm in width,[10] to 3.0–3.5 µm by 1.5–2.5 µm.[11]

Intolerant to benomyl,[13] C. hoffmannii is capable of proteolytic activity (hydrolysis, in particular), with proteolytic enzymes detected in cultures of C. hoffmannii with various media, including Loeffler blood serum, and skim milk and Litmus milk.[14] Coniochaeta hoffmannii is also quite wikt:thermotolerant, easily growing at 30 and 35 °C, with two out of four isolates (both environmental) growing at 40 °C.[14]

Despite being one of only two species of medical interest within the genus Coniochaeta,[11] Coniochaeta hoffmannii is rarely encountered as a pathogen primarily due to its related taxa. It is one of the more predominant species of its genus concerning the number of clinical cases reporting infection, having been associated with cases of subcutaneous infections, keratitis, sinusitis, and peritonitis.[9] Coniochaeta hoffmannii rarely causes disease, but when it does, it is only seen in immunocompromised patients, thus marking it as an opportunistic fungal pathogen.[4] Other identifying factors for opportunistic pathogens like this include an association with other underlying diseases capable of compromising the host's immune system, an association with new therapeutic modalities, and cases of invasive fungal sinusitis with no determinable predisposing factors. While great advances in medical technology have decreased previously high rates of morbidity and mortality, the amount and variation of opportunistic pathogens has also increased.[15]

Coniochaeta hoffmannii has been inculpated in human phaeohyphomycosis, leading to the aforementioned abscesses, sinusitis, and mastoiditis, to name a few.[16] It has also been implicated as a food contaminant, which could explain how people or animals interact with it in their respective environments.[17]

Coniochaeta hoffmannii has proven to be resistant to multiple antifungal agents, including amphotericin B, flucytosine, ketoconazole, and fluconazole.[4] Because of this, precautions have been taken, such as antifungal susceptibility testing, in order to circumvent such drawbacks. Through this method, polyhexamethylene biguanide (PHMB) has been identified and utilized in conjunction with invasive surgical procedures to successfully treat one of the only cases of infection at the hands of this fungus. This method of treatment is employed in order to safeguard against fungal infection even in an immunocompetent host.[15]