Design and comparison of a hybrid to a traditional in-person point-of-care ultrasound course.

BACKGROUND: Traditional introductory point-of-care ultrasound (POCUS) courses are resource intensive, typically requiring 2-3 days at a remote site, consisting of lectures and hands-on components. Social distancing requirements resulting from the COVID-19 pandemic led us to create a novel hybrid course curriculum consisting of virtual and in-person components. METHODS: Faculty, chief residents, fellows and advanced practice providers (APPs) in the Department of Medicine were invited to participate in the hybrid curriculum. The course structure included 4 modules of recorded lectures, quizzes, online image interpretation sessions, online case discussions, and hands-on sessions at the bedside of course participant's patients. The components of the course were delivered over approximately 8 months. Those participants who completed a minimum of 3 modules over the year were invited for final assessments. Results from the hybrid curriculum cohort were compared to the year-end data from a prior traditional in-person cohort. RESULTS: Participant knowledge scores were not different between traditional (n = 19) and hybrid (n = 24) groups (81% and 84%, respectively, P = 0.9). There was no change in POCUS skills as measured by the hands-on test from both groups at end-of-course (76% and 76%, respectively, P = 0.93). Confidence ratings were similar across groups from 2.73 traditional to 3.0 hybrid (out of possible 4, P = 0.46). Participants rated the course highly, with an average overall rating of 4.6 out 5. CONCLUSIONS: A hybrid virtual and in-person POCUS course was highly rated and as successful as a traditional course in improving learner knowledge, hands-on skill and confidence at 8 months after course initiation. These results support expanding virtual elements of POCUS educational curricula.

Treatment of Leptomeningeal Carcinomatosis in a Patient With Metastatic Cholangiocarcinoma.

A 49-year-old woman with cholangiocarcinoma metastatic to the lungs presented with new-onset unrelenting headaches. A lumbar puncture revealed malignant cells consistent with leptomeningeal metastasis from her cholangiocarcinoma. Magnetic resonance imaging (MRI) of the brain revealed leptomeningeal enhancement. An intrathecal (IT) catheter was placed and IT chemotherapy was initiated with methotrexate. Her case is notable for the rarity of cholangiocarcinoma spread to the leptomeninges, the use of IT chemotherapy with cytologic and potentially symptomatic response, and a possible survival benefit in comparison to previously reported cases of leptomeningeal carcinomatosis secondary to cholangiocarcinoma.

An innate immune system cell is a major determinant of species-related susceptibility differences to fungal pneumonia.

Rats and mice are considered resistant and susceptible hosts, respectively, for experimental cryptococcosis. For both species, alveolar macrophages (AM) are central components of the host response to pulmonary Cryptococcus neoformans infection. We explored the role of AM in three strains of mice and three strains of rats during cryptococcal infection by comparing the outcome of infection after macrophage depletion using liposomal clodronate. AM depletion was associated with enhancement and amelioration of disease in rats and mice, respectively, as measured by lung fungal burden. The apparent protective role for AM in rats correlated with enhanced anti-cryptococcal activity as measured by phagocytic activity, oxidative burst, lysozyme secretion, and ability to limit intracellular growth of C. neoformans. Furthermore, rat AM were more resistant to lysis in association with intracellular infection. In summary, differences in AM function in rats and mice suggest an explanation for the species differences in susceptibility to C. neoformans based on the inherent efficacy of a central effector cell of the innate immune system.

Melanization of Cryptococcus neoformans affects lung inflammatory responses during cryptococcal infection.

The production of melanin pigments is associated with virulence for many microbes. Melanin is believed to contribute to microbial virulence by protecting microbial cells from oxidative attack during infection. However, there is also evidence from various systems that melanins have immunomodulatory properties, which conceivably could contribute to virulence by altering immune responses. To investigate the effect of melanin on the immune response, we compared the murine pulmonary responses to infection with melanized and nonmelanized Cryptococcus neoformans cells. Infection with melanized cells resulted in a greater fungal burden during the early stages of infection and was associated with higher levels of interleukin-4 and MCP-1 and greater numbers of infiltrating leukocytes. Infection with laccase-positive (melanotic) C. neoformans cells also elicited higher MCP-1 levels and more infiltrating leukocytes than did infection with laccase-negative cells. Melanization interfered with phagocytosis in vivo for encapsulated C. neoformans but not for nonencapsulated cells. The results provide strong evidence that cryptococcal melanization can influence the immune response to infection and suggest that immunomodulation is an additional mechanism by which the pigment contributes to virulence.

The pathogenesis of fatal outcome in murine pulmonary aspergillosis depends on the neutrophil depletion strategy.

Aspergillus fumigatus causes invasive disease in severely immunocompromised hosts but is readily cleared when host innate defenses are intact. Animal models for evaluation of therapeutic strategies to combat invasive aspergillosis that closely mimic human disease are desirable. We determined optimal dosing regimens for neutrophil depletion and evaluated the course of infection following aerosol infection in mice by determining survival, organ fungal burden, and histopathology in mice in which neutropenia was induced by three methods, administration of granulocyte-depleting monoclonal antibody RB6-8C5 (MAb RB6), administration of cyclophosphamide, and administration of both agents. Administration of either individual agent resulted in a requirement for relatively high conidial inocula to achieve 100% mortality in both BALB/c and C57BL/6 mice, although the infection appeared to be somewhat more lethal in C57BL/6 mice. Death following induction of neutropenia with MAb RB6 occurred when a relatively low fungal burden was present in the lung and may have been related to the inflammatory response associated with neutrophil recovery. In contrast, administration of both agents reduced the lethal inoculum in each mouse strain by approximately 1 log(10), and C57BL/6 mice that received both agents had a higher fungal burden and less inflammation in the lung at the time of death than BALB/c mice or mice of either strain that received MAb RB6 alone. Our data suggest that the relationship among fungal burden, inflammation, and death is complex and can be influenced by the immunosuppression regimen, the mouse strain, and the inoculum.

Experimental murine cryptococcal infection results in contamination of bedding with Cryptococcus neoformans.

Cryptococcus neoformans is a fungal pathogen that survives in diverse environments. To determine whether cages of mice infected with C. neoformans posed an infection risk to animal caregivers, we investigated whether the fungus could be isolated from the bedding or stool of mice infected by intratracheal (i.t.), intravenous (i.v.), or intraperitoneal (i.p.) routes. The bedding of mice infected i.t. was contaminated with C. neoformans. In contrast, no contamination of bedding with C. neoformans was detected in cages of mice infected i.v. or i.p. C. neoformans was not isolated from murine feces. The C. neoformans strain recovered from bedding material was indistinguishable from the infecting strain by biochemical and molecular techniques. This result suggests that precautions may be warranted when disposing bedding from cages that housed mice with pulmonary C. neoformans infection.

Neutropenia alters lung cytokine production in mice and reduces their susceptibility to pulmonary cryptococcosis.

Neutrophils are generally considered to contribute to host defense through their potent microbicidal activity. However, there is accumulating evidence that neutrophils also have an important regulatory role in establishing the balance of Th1 and Th2 responses. This study investigated the role of neutrophils in defense against pulmonary Cryptococcus neoformans infection using neutrophil-depleted BALB/c mice generated by administering mAb RB6-8C5. Neutropenic mice with pulmonary infection survived significantly longer than control mice, but there was no difference between groups infected intravenously. On day 1 of infection, neutropenic mice had significantly smaller fungal burdens than control mice. On day 7, neutropenic mice had significantly higher lung concentrations of IL-10, TNF-alpha, IL-4, and IL-12 than control mice, but there was no difference in IFN-gamma and MCP-1 levels. Neutrophils influenced the outcome of cryptococcal infection in mice through mechanisms that did not involve a reduction in early fungal burden. The absence of neutrophils in lung tissue during the initial stages of infection appeared to alter the inflammatory response in a manner that was subsequently beneficial to the host. Higher levels of Th1- and Th2-associated cytokines in neutropenic mice could have simultaneously promoted a strong cellular response while reducing inflammatory damage to the lung. Our results support the emerging concept that neutrophils play an important function in modulating the development of the immune response.

Antibody-mediated protection in murine Cryptococcus neoformans infection is associated with pleotrophic effects on cytokine and leukocyte responses.

Cryptococcus neoformans, an encapsulated yeast, is a common cause of life-threatening meningoencephalitis in immunosuppressed patients. We previously observed that administration of a monoclonal antibody (MAb) to the capsular polysaccharide to mice with pulmonary infection prolonged survival and enhanced granulomatous inflammation without reducing lung CFU. To understand the mechanism of MAb action, we studied leukocyte recruitment and cytokine profiles in lungs of A/JCr mice. B lymphocytes were the predominant cell type in lung infiltrates, comprising 15 to 30% of the leukocytes. Despite alterations in histological appearance, fluorescence-activated cell sorter analysis revealed no significant difference in total numbers of lung leukocytes in MAb-treated mice and controls. Differences in the immune response to C. neoformans between MAb-treated mice and controls included (i) an increase in the percentage of granulocytes among lung leukocytes on day 14, (ii) higher macrophage surface expression of CD86 on day 28, (iii) larger amounts of IL-10 in lung homogenates at day 7, (iv) a trend toward smaller amounts of gamma interferon mRNA and protein on day 7, and (v) a smaller increase in the levels of interleukin-4 mRNA and protein on day 7. Hence, the immune responses to C. neoformans infection in the presence and absence of specific antibody were qualitatively similar, and antibody administration was associated with several subtle quantitative differences in immune response parameters that could translate into enhanced survival. MAb may function partly by down-regulating the inflammatory response and reducing host damage. Our findings demonstrate unexpected complexity in the interaction between specific MAb and other components of the host immune response.