Volume 37 Number 6 | December 2023
Ronald A. Hodge, MLS(ASCP), SM, ASCLS Today Volunteer Contributor
A 67-year-old male sinus cancer patient presented to the Emergency Department (ED) at Willis Knighton Medical Center with chest pain. Because the patient had a history of leukocytosis and immunosuppression, ceftriaxone and azithromycin, IV antibiotics were begun in the ED. Upon admission, Etoposide and Carboplatin, chemotherapy medications, along with vancomycin and meropenem IV antibiotics, were added to patient’s protocol. Two sets of blood culture were sent to the laboratory for culture based on the patient’s differential diagnosis in the ED.
After three days of incubation, one aerobic Bactec blood culture bottle reported positive. The gram stain showed large aseptate hyphae resembling a fungi. Since the infectious disease physician believed the organism was a possible contaminant, no further identification of the fungi was performed by our lab. However, if identification was performed, you would have seen rapidly growing hyphae that fill the agar surface, commonly known as “lid lifters.” The lactophenol blue would have shown very large hyphae that produce sexual spores (sporangiosphores) in sporangia. The most likely Zygomycete would be either be Rhizopus or Mucor. The sporangiophores are not branched and rhizoids (root like structures would appear nodal at the base of the sporangiophore with Rhizopus. Mucor’s sporangiophores are often branched, and no rhizoids are present.
Mycamine, an antifungal medication, was added to the patient’s plan of treatment. Two more sets of blood cultures were sent to the lab and reported as no growth after five days. The patient responded to treatment and was discharged.
Zygomycetes have a worldwide distribution and are commonly found on decaying vegetable matter or old bread (bread mold) or in soil. The organism is generally acquired by inhalation or ingestion of spores or through percutaneous routes, followed by subsequent development of infection. One of the most common presentations is the rhinocerebral form. Immunocompromised patients are at a great risk, particularly those who have uncontrolled diabetes mellitus and transplant patients who are undergoing prolonged corticosteroid, antibiotic, or cytotoxic therapy.1 Sites of infection usually are lung, nasal sinus, brain, eye, and mucous membrances.2
In the history of our laboratory, the fungi we have isolated in blood cultures are Candida sp., Aspergillus sp., Histoplasma capsulatum, Blastomyces dermatiditis, but rarely a Zygomycete. The patient’s history of sinus cancer and prolonged cytotoxic therapy set up the perfect scenario for a potential Zygomycete infection in the blood. Zygomycetes have a marked propensity for vascular invasion making it plausible to see it in a blood stream infection. If a sinus aspirate was ordered and collected, we could probably have identified the sinus cavities as the source of the systemic infection, as that is a more common infection site. This is the first time in my 40-year career that I have seen this fungus in a blood infection.
- Tille, P.M. (2017). Diagnostic Microbiology (14th ed., p.783). Elsevier.
- Larone, D. H. (2011). Medically Important Fungi (5th ed., p.37) ASM Press.
Ronald A. Hodge is a Clinical Laboratory Science Student Educator at Willis Knighton Medical Center in Shreveport, Louisiana.