A 38-year-old man with human immunodeficiency virus (HIV) and a CD4+ count of 100 cells/µL is admitted to the ICU with respiratory failure from the medical ward. He reports 1 week of progressive dyspnea on exertion and chills. He had been treated with vancomycin and meropenem since his arrival to the ED 1 day ago. He is intubated and mechanically ventilated on volume controlassist control, tidal volume 6 mL/kg ideal body weight, respiratory rate 18/min, FiO2 0.7, and PEEP 8 cm H2O. His initial vital signs are:
Initial laboratory data are remarkable for a (1,3)-beta-d-glucan >200 pg/mL and LDH 100 U/L. On day 1 of his ICU stay, a bronchoscopy with bronchoalveolar lavage is performed and the Pneumocystis examination is negative.
Which of the following can result in an elevated 1-3 beta-d-glucan blood test in this patient?
Correct Answer: A
The (1,3)-beta-d-glucan test is a common, commercially available assay that detects a polysaccharide element of fungal cell walls that is found in most fungi. Notable exceptions to this are cryptococci, zygomycetes (eg mucormycoses), and Blastomyces dermatitidis, which either completely lack this element or produce it at minimal levels (answer B, answer C, and answer E are incorrect). This test, therefore, cannot be used to rule out infection with these fungal organisms. Notably, beta-lactam antibiotics may react with this assay and produce false-positive results (answer A is correct; answer D is incorrect). The (1,3)-beta-d-glucan has been studied as a noninvasive diagnostic test for pneumocystis pneumonia and has good sensitivity in patients with HIV. However, bronchoalveolar lavage remains the gold standard of the diagnosis of pneumocystis pneumonia.
A 58-year-old man with idiopathic pulmonary fibrosis is admitted to the ICU with an acute exacerbation of interstitial lung disease. He reports 4 days of worsening dyspnea and dry cough, without fevers, chills, night sweats, or other associated symptoms. His examination is notable for diffuse crackles throughout inspiration. He reports that he is originally from India and moved to the United States 20 years ago, where he has lived since. He is placed on high-flow nasal cannula with FiO2 0.5 and flow of 40 L/min. Methylprednisolone 50 mg daily is administered, along with vancomycin, ceftriaxone, and azithromycin. A chest CT reveals basilar predominant honeycombing with new superimposed multifocal ground glass opacities, along with new scattered right upper and middle lobe centrilobular nodules compared with CT scan 1 year prior. A sputum culture is obtained and sent for bacterial, fungal, and mycobacterial cultures along with acid-fast bacilli (AFB) stain. The sputum is found to have 2+ AFB. A nucleic acid amplification test (NAAT) for tuberculosis (TB) is negative. A repeat sputum sample is collected and again results with 2+ AFB and negative TB NAAT with no presence of NAAT inhibitors detected by the laboratory.
What is the best next step and interpretation of this finding?
Correct Answer: C
This patient presents with worsening hypoxemia in the setting of structural lung disease and has new findings of ground glass opacities and centrilobular nodules. Sputum testing reveals AFB with a negative NAAT for tuberculosis on repeated specimens. Latent tuberculosis infection should not result in AFB smear positive sputum (answer D is incorrect). NAAT has high sensitivity and specificity for tuberculosis in AFB smear positive sputum samples. Less than 5% of NAAT testing is falsely negative on AFB smear positive samples because of the presence of nucleic acid amplification inhibitors. If the presence of these inhibitors is excluded, repeat AFB smear positive and NAAT negative samples suggest a nontuberculous mycobacterium (NTM) infection (answer C is correct; answer E is incorrect). NTM infection occurs most commonly in patients with structural lung disease and is a chronic, indolent infection. Prior BCG vaccination may cause a reaction to tuberculin skin testing resulting in a false-positive result; it does not affect the performance of TB PCR (answer A is incorrect). Interferon gamma release assays are testing modalities for latent tuberculosis infection and cannot rule in or out active tuberculosis disease (answer B is incorrect).
A 75-year-old woman is admitted to the ICU after coronary artery bypass graft complicated by cardiogenic shock. She is improving on ICU day 4, and her ventilator settings are pressure support 10 cm H2O, PEEP 8 cm H2O, and FiO2 0.4. She is noted later that day to have increased frequency of thick secretions requiring suctioning through her endotracheal tube and develops a new fever at 39°C. Over the course of the evening, she experiences frequent oxygen desaturation, requiring an increase in her FiO2 to 0.6. A chest radiograph reveals a new opacity in the right lower lung field, and she is started on vancomycin and levofloxacin. Sputum culture grows Acinetobacter baumannii after 48 hours without other organisms identified over the next 24 hours.
What is the BEST next step in her management?
Correct Answer: B
This patient is presenting with VAP, as indicated by the development of fevers, increased sputum production, radiographic infiltrate, and worsening respiratory status after 4 days of mechanical ventilation. Common organisms in VAP include methicillin-resistant S. aureus, P. aeruginosa, and other gram-negative bacilli including Acinetobacter species. Although empiric coverage for Acinetobacter is not necessary unless there is a high degree of suspicion based on past infections, the isolation of this organism in sputum culture warrants appropriate antibiotic coverage. The treatments of choice for Acinetobacter species are either a carbepenem or ampicillin/sulbactam, with further treatment guided by antimicrobial susceptibility testing and local antibiogram data (answer B is correct; answers A, C, and D are incorrect). Ongoing empiric coverage for other organisms is not necessary in VAP once cultures have resulted (answer E is incorrect).
A 75-year-old man with hypertension, mild Alzheimer disease marked by occasional short-term memory difficulties, and a past history of squamous cell carcinoma of the tongue with prior surgical resection and radiation to the neck presents from his assisted living facility with productive cough and shortness of breath. The assisted living facility staff reports that he is routinely noted to be coughing while eating meals, and his dyspnea and cough began while eating yesterday. His medications include hydrochlorothiazide and amlodipine. In the ED, his vital signs are:
A CT scan of his chest reveals patchy bibasilar ground glass opacities and tree-in-bud opacities. Supplemental oxygen is provided via a venturi mask at FiO2 0.5 and admitted to the ICU.
Which of the following is most accurate concerning this patient’s pneumonia?
Correct Answer: D
This patient presents with dyspnea, hypoxemia, and cough, with a reported history of coughing while eating, suggestive of aspiration. His chest imaging is notable for inflammatory changes in a gravity-dependent distribution, along with tree-in-bud opacities, all supportive of aspiration pneumonitis versus pneumonia. He also has a prior history of surgery and radiation to his tongue and neck, which likely resulted in oropharyngeal dysphagia. HCAP is no longer a distinct category of pneumonia, and he should therefore be treated as a CAP, given the absence of specific risk factors for resistant organisms (answer A is incorrect). Additionally, his presentation is not characteristic of an anaerobic pneumonia, which is often more indolent and occurs in patients with specific risk factors, and so he does not require anaerobic coverage as part of his initial empiric regimen (answer D is incorrect). Although advanced dementia may be a risk factor for aspiration, this patient has very mild symptoms of dementia (answer C is incorrect). Although feeding tubes allow for more effective nutrition in patients with dysphagia, they do not reduce the risk of aspiration pneumonia (answer B is incorrect).
A 54-year-old woman develops fevers and cough on the final day of her vacation on a cruise ship in the Caribbean. She returns to her home in Florida, and over the following 3 days, she has continued fevers, productive cough, and new dyspnea on exertion. She presents to the ED and her vitals at that time are:
Her chest radiograph demonstrates multifocal patchy opacities and increased interstitial markings throughout all lung fields. Ceftriaxone and azithromycin are administered, along with 2 L of lactated ringers solution intravenously and her urinary Legionella antigen subsequently returns positive. She is admitted to the ICU on highflow nasal cannula at FiO2 0.7 and flow 50 L per minute.
Which of the following statements is most accurate regarding Legionella pneumonia?
Legionella infection of the lungs results from exposure to aerosolized Legionella species that reside in water sources. The most recognized sites of outbreaks have been cruise ships, hotels, resorts, and healthcare facilities where large water storage and heating systems are present. The most common causative agent is Legionella pneumophila serogroup 1, which is also the only species reliably detected by urinary antigen testing (answer A is incorrect). Serogroup 1 may account for nearly 85% of cases by some estimates, and urine-antigen testing is estimated to have a sensitivity of at least 70%. Legionella culture is technically challenging for a number of reasons: at least half of the patients with legionella have no sputum production, culture requires specific agar (buffered charcoal yeast extract), the bacteria can be slow growing (5+ days), and the sensitivity is highly dependent on the technical skill of the diagnostic laboratory. For this reason, Legionella culture is generally insensitive, with a sensitivity that is estimated to range from 20% to 80% (answers C and D are incorrect). The identification of Legionella on sputum culture is 100% specific for Legionella infection. Legionella is more prevalent among patients with severe CAP than in nonhospitalized patients with pneumonia and accounts for an even greater proportion of pneumonia in patients requiring ICU admission; no other atypical pathogen commonly causes severe CAP requiring ICU admission (answer E is incorrect).
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