Pseudomonas species may appear strikingly filamentous in tissue sections: an important consideration for surgical pathologists and a reminder of the utility of modified silver impregnation methods.

Although tissue culture is the gold standard for diagnosing infection, histologic examination of surgically resected tissue can be a critical component in the diagnosis of tissue infection. The goal of this brief report is to alert surgical pathologists that Pseudomonas species can appear strikingly filamentous histologically and may somewhat mimic the appearance of filamentous bacteria, such Actinomyces or Nocardia, or thin fungal hyphae. A secondary aim is to raise awareness that Pseudomonas can sometimes only be identified histologically through the use of a modified silver impregnation method (Steiner stain). Five cases of filamentous Pseudomonas were encountered in three different surgical pathology subspecialities (ophthalmic pathology, cardiovascular pathology, and dermatopathology) over a 1-year period. All cases were of formalin-fixed, paraffin-embedded tissue, stained using hematoxylin & eosin (H&E) and multiple histochemical stains. Four cases grew Pseudomonas aeruginosa in culture and, in the fifth case, a nonaeruginosa species was detected using polymerase chain reaction-based methods. The markedly filamentous-appearing Pseudomonas organisms were identified in five different tissue sites: vascular graft, enucleation (whole eye) specimen, scleral biopsy, soft-tissue excision, and skin punch biopsy. In one of the five cases the organisms were seen on H&E, and in only two of the five were the organisms seen on Brown-Hopps stain. In all five cases, the organisms were identified on Steiner stain. It is therefore important to recognize that Pseudomonas can appear markedly filamentous, Pseudomonas or other bacterial infection is suspected, the surgical pathologist would be advised to employ the Steiner stain to most consistently detect the organisms.

Marked factor V activity elevation in severe COVID-19 is associated with venous thromboembolism.

Coagulopathy causes morbidity and mortality in patients with coronavirus disease 2019 (COVID-19) due to severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection. Yet, the mechanisms are unclear and biomarkers are limited. Early in the pandemic, we observed markedly elevated factor V activity in a patient with COVID-19, which led us to measure factor V, VIII, and X activity in a cohort of 102 consecutive inpatients with COVID-19. Contemporaneous SARS-CoV-2-negative controls (n = 17) and historical pre-pandemic controls (n = 260-478) were also analyzed. This cohort represents severe COVID-19 with high rates of ventilator use (92%), line clots (47%), deep vein thrombosis or pulmonary embolism (DVT/PE) (23%), and mortality (22%). Factor V activity was significantly elevated in COVID-19 (median 150 IU/dL, range 34-248 IU/dL) compared to contemporaneous controls (median 105 IU/dL, range 22-161 IU/dL) (P < .001)-the strongest association with COVID-19 of any parameter studied, including factor VIII, fibrinogen, and D-dimer. Patients with COVID-19 and factor V activity >150 IU/dL exhibited significantly higher rates of DVT/PE (16/49, 33%) compared to those with factor V activity ≤150 IU/dL (7/53, 13%) (P = .03). Within this severe COVID-19 cohort, factor V activity associated with SARS-CoV-2 load in a sex-dependent manner. Subsequent decreases in factor V were linked to progression toward DIC and mortality. Together, these data reveal marked perturbations of factor V activity in severe COVID-19, provide links to SARS-CoV-2 disease biology and clinical outcomes, and nominate a candidate biomarker to investigate for guiding anticoagulation therapy in COVID-19.

Laboratory Diagnosis for SARS-CoV-2 Infection.

The optimal diagnostic test for SARS-CoV-2 infection should be selected based on a patient's clinical syndrome and presentation in relation to symptom onset. Molecular testing, most often reverse-transcriptase polymerase chain reaction, offers the highest sensitivity and specificity during acute infection, whereas antigen testing can also be useful for acute diagnosis when rapid turnaround of results is necessary or if molecular testing is unavailable. Serologic testing is often reserved for identifying individuals with prior or late COVID-19 infection.

Nocardiosis diagnosed on bronchoalveolar lavage: Role of cytopathology.

Nocardia are gram-positive, filamentous bacteria that have the potential to cause serious disease, particularly in immunocompromised patients. Nocardia may cause a complex clinical picture, with radiologic features that can mimic other infectious organisms or malignancy. The organisms are not easily identified on cytologic examination given their weak staining with routine preparations and because they may be obscured by the associated inflammatory exudate. However, recognition of subtle features and a high index of suspicion in the appropriate clinical setting can lead to the appropriate triaging of material for ancillary stains and confirmatory microbiology tests. We herein present three cases of nocardiosis diagnosed on bronchoalveolar lavage in order to discuss the clinical presentation and cytomorphologic features with emphasis on the role of cytopathologists in facilitating timely diagnosis and helping direct appropriate management.