Microbiology Case Study: A 14 Year Old Immunocompromised Male with Pneumonia

Case History

A 14 year old male with a history of selective IgG deficiency, asthma, and GE reflux s/p Nissen Fundoplication, presented to the pediatric pulmonary clinic with 2 weeks of cold like symptoms that progressed to a wet sounding cough productive of sputum and chest pain. 5 days prior he had seen his primary care physician who diagnosed him with pneumonia and started him on amoxicillin and 5 days of prednisone (60mg daily). He is using his albuterol nebulizer every 3 hours, and feels as though his asthma may be contributing to his symptoms but is not the main cause as he has not had a wet cough and chest heaviness and pain with previous asthma attacks. He has had low grade fevers for the past several days but denies chills, sweats, or hemoptysis.  Of note his immune deficiency is treated with IVIG and long term Bactrim which was recently stopped. Pediatric pulmonology elected not to restart the Bactrim but changed his antibiotic to Augmentin. The patient continued to have chest pain and coughing, so the decision was made to proceed with bronchoscopy

Laboratory Identification

Cultures from the BAL revealed a rapidly growing fungi with broad hyphae (5 to 15 micron diameter) that are irregularly branched, and have rare septations. These features, paired with the morphology of the sporangia are diagnostic for a Zycomycete; further identification was attempted however, rhizoids characteristic of Rhizopus, and branching characteristic of Mucor were not identified in this culture.

Discussion

Zygomycetes (Mucormycetes) are widely distributed in the environment in soil and vegetation and infection is through inhalation of spores. Typically, the spores are transported by the muco-cilliary escalader to the pharynx, are swallowed, and then are broken down by the GI tract. In immunocompromised patients, the spores can settle in the nasal turbinates and alveoli causing disease (1). The most common sites of infection are rhino-orbital-cerebral and pulmonary and typically occur in immunocompromised hosts and diabetics (2). The Zygomycetes are also known to invade blood vessels making tissue infarction and necrosis one of the hallmarks of the disease (3). These fungi grow rapidly and are often referred to as “lid lifters” when cultured. Because of this rapid growth, infection with Zygomycetes typically progress quickly and cause periorbital edema, proptosis, and blindness. Facial numbness can occur if there is infarction of sensory branches of the fifth cranial nerve. Infection can spread from the ethmoid sinus to the frontal lobe and result in obtundation. If infection spreads from the sphenoid sinuses to the adjacent cavernous sinus, it can result in cranial nerve palsies, thrombosis of the sinus, and involvement of the carotid artery (4). When the spores are inhaled into the lung, pneumonia with infarction and necrosis results. The infection can spread to contiguous structures, such as the mediastinum and heart, or disseminate hematogenously to other organs such as the GI tract, kidney, and brain (5). Infections are treated with a combination of antifungal drugs such as Amphotericin B, and aggressive surgical debridement. In some situations removal of the palate, nasal cartilage, and orbit are necessary for cure. In patients with pneumonia, often lobectomy is needed for cure (5).

The genera most commonly found in human infections are Rhizopus, Mucor, and Rhizomucor. Rhizopus organisms have an enzyme called ketone reductase, which allows them to thrive in high glucose, acidic conditions, such as in individuals with diabetic ketoacidosis. Rhizopus will have root like rhizoids and are typically located near the sporangiophores. The post-mature sporangiophores can undergo “umbrella like” collapse which is characteristic of Rhizopus. Mucor is more likely to have branching and is often identified when all other species are ruled out; they do not produce a rhizoid.
References

1. Ferguson BJ. Mucormycosis of the nose and paranasal sinuses. Otolaryngology Clinics of North America. 2000;33(2):349.
2. Kauffman CA, Malani AN. Zygomycosis: an emerging fungal infection with new options for management. Current Infectious Disease Reports. 2007;9(6):435.
3. Greenberg RN, Scott LJ, Vaughn HH, Ribes JA. Zygomycosis (mucormycosis): emerging clinical importance and new treatments. Current Opinions in Infectious Diseases. 2004;17(6):517.
4. Yohai RA, Bullock JD, Aziz AA, Markert RJ. Survival factors in rhino-orbital-cerebral mucormycosis. Survey of Ophthalmology. 1994;39(1):3.
5. Tedder M, Spratt JA, Anstadt MP, Hegde SS, Tedder SD, Lowe JE. Pulmonary mucormycosis: results of medical and surgical therapy. Annals of Thoracic Surgery. 1994;57(4):1044.

-Casey Rankins, DO, is a 1^st year Anatomic and Clinical Pathology resident at the University of Vermont Medical Center.

-Christi Wojewoda, MD, is the Director of Clinical Microbiology at the University of Vermont Medical Center and an Associate Professor at the University of Vermont.