INTRODUCTION: Invasive Aspergillosis in critically ill patients in medical intensive care units (MICU) is a well recognized entity. Association with contaminated air handling systems has been reported in the past, although the epidemiological data is sparse. We report two cases of invasive pulmonary aspergillosis in critically ill patients associated with mold contamination of air handling ducts and reversal of air flow in negative pressure isolation room in MICU.
CASE PRESENTATION: Index case: A 61-year-old female with history of Chronic Obstructive Pulmonary Disease (COPD) was admitted with two week history of cough and dyspnea. At presentation, patient was found to be hypotensive, hypoxic, and in acute renal failure. The CXR revealed bilateral diffuse infiltrates suggestive of pneumonia. The patient was intubated for respiratory failure, started on broad spectrum antibiotics and methylprednisolone. The influenza A-PCR was positive for H1N1. The initial blood and tracheal aspirate cultures were negative. Hospital course was complicated by development of Acute Respiratory Distress Syndrome (ARDS), Atrial fibrillation with rapid ventricular rate (RVR), and pulmonary embolism. The patient remained hemodynamically unstable requiring vasopressor and ventilator support. On day 14, the patient developed fever of 105° F and elevated WBC of 40,000 with a differential of 36% neutrophils, 5% lymphocytes, and 12% bands. Repeat blood cultures and Clostridium difficile toxin assay were negative. Echocardiogram showed no vegetation or thrombosis. The patient underwent bronchoscopy which revealed multiple raised whitish lesions surrounded by rim of brownish discoloration in the left main stem bronchus. The endobronchial forceps biopsy of lesions was performed and pathological diagnosis of invasive aspergillosis was made. The patient was started on Micafungin and Amphotericin B. Voriconazole was not administered as the patient had Atrial fibrillation with RVR responding to Amiodarone only. Despite broad-spectrum antibiotics and anti-fungal therapy, the patient died of cardiopulmonary arrest on 17th day of hospitalization. An autopsy was not performed. Case #2: A 58-year-old male with history of Hepatitis C, alcohol abuse and COPD presented with septic shock. Course of hospitalization was complicated with severe hypoxemia and development of ARDS. Tracheal aspirate grew Aspergillosis spp. Lung biopsy was not performed due to severe hypoxemia. Patient was treated with Voriconazole and Amphotericin. Patient died after being hospitalized for 12 days.
DISCUSSION: Aspergillus species are ubiquitous molds that produce numerous spores, 2-4 µm in diameter. Despite routine inhalation of these spores, Aspergillus spp remain an uncommon cause of disease, except in individuals at particular risk for invasive disease. Given the ubiquitous nature of Aspergillus spores in the external environment, numerous reservoirs have been identified in hospitals. Contaminated central air handling systems can become breeding grounds for mold. Lutz (2003) reports an outbreak of invasive Aspergillus infection in post-surgical patients due to a contaminated air-handling system in an operating theater, reportedly with 3-1000-fold increased concentrations of ≥ 3 µm particles. In our cases, both patients were admitted to the same negative pressure isolation room. Despite aggressive medical therapy, their conditions continued to deteriorate, and subsequently diagnosis of aspergillosis was made. Cluster of cases involving Aspergillus spp within a span of 4 weeks in MICU lead to an investigation. As a surrogate for Aspergillus spp infestation particle counts were performed using Zephon Bio pump. A visual inspection of air ducts using digital photographs was also consistent with mold infestation. Spore trap samples revealed significant increase in >0.3 µm particles approximately 2 million and for particles ≥1 µm 41,000 particles.
CONCLUSIONS: Aspergillus species can cause infrequent but serious nosocomial infection in MICU, and our cases point towards a possible association with contaminated air handling ducts, which warrants further studies. Introduction of comprehensive air quality guidelines in critical areas such as ICU may prevent outbreaks.
Reference #1 Lutz BD, Jin J, Rinaldi M, Wickes B. Outbreak of Invasive Aspergillus Infection in Surgical Patients, Associated with a Contaminated Air-Handling System. CID. 2003:37.
Reference #2 Srinivasan A, Beck C, Buckley T, GehA. The ability of hospital ventilation systems to filter Aspergillus and other fungi following a building implosion. Infection Control Hosp Epidermiol. 2002 Sep;23(9):520-4.
DISCLOSURE: The following authors have nothing to disclose: Mitra Sahebazamani, Edmundo Rubio, Umar Sofi
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