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#causality #has-images #statistics
For example, if we remove the 𝐴 → 𝐵 to get Figure 3.5, then 𝐴 → 𝐶 ← 𝐵 is an immorality
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#causality #statistics
In contrast, the non-strict causal edges assumption would allow for some parents to not be causes of their children. It would just assume that children are not causes of their parents. This allows us to draw graphs with extra edges to make fewer assumptions, just like we would in Bayesian networks, where more edges means fewer independence assumptions. Causal graphs are sometimes drawn with this kind of non-minimal meaning, but the vast majority of the time, when someone draws a causal graph, they mean that parents are causes of their children.
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#causality #statistics
As we discussed in Section 4.2, the graph for the interventional distribution 𝑃(𝑌 | do(𝑡)) is the same as the graph for the observational distribution 𝑃(𝑌, 𝑇, 𝑋) , but with the incoming edges to 𝑇 removed. For example, if we take the graph from Figure 4.5 and intervene on 𝑇 , then we get the manipulated graph in Figure 4.6. In this manipulated graph, there cannot be any backdoor paths because no edges are going into the backdoor of 𝑇 . Therefore, all of the association that flows from 𝑇 to 𝑌 in the manipulated graph is purely causal.
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Flashcard 7074625752332

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#causality #has-images #statistics


Question
However, we do have conditional [...] in the data. This is because, when we condition on 𝑋 , there is no longer any non-causal association between 𝑇 and 𝑌 . The non-causal association is now “blocked” at 𝑋 by conditioning on 𝑋 . We illustrate this blocking in Figure 2.4 by shading 𝑋 to indicate it is conditioned on and by showing the red dashed arc being blocked there
Answer
exchangeability

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However, we do have conditional exchangeability in the data. This is because, when we condition on 𝑋 , there is no longer any non-causal association between 𝑇 and 𝑌 . The non-causal association is now “blocked” at 𝑋 by conditioning o

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Flashcard 7074628373772

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#causality #has-images #statistics


Question
For example, if we remove the [...] to get Figure 3.5, then 𝐴 → 𝐶 ← 𝐵 is an immorality
Answer
𝐴 → 𝐵

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#causality #statistics
In contrast, the non-strict causal edges assumption would allow for some parents to not be causes of their children. It would just assume that children are not causes of their parents. This allows us to draw graphs with extra edges to make fewer assumptions, just like we would in Bayesian networks, where more edges means fewer independence assumptions.
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In contrast, the non-strict causal edges assumption would allow for some parents to not be causes of their children. It would just assume that children are not causes of their parents. This allows us to draw graphs with extra edges to make fewer assumptions, just like we would in Bayesian networks, where more edges means fewer independence assumptions. Causal graphs are sometimes drawn with this kind of non-minimal meaning, but the vast majority of the time, when someone draws a causal graph, they mean that parents are causes of their

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Flashcard 7074632830220

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#causality #statistics
Question
Probabilistic graphical models are [...] models while causal graphical models are causal models.
Answer
statistical

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Probabilistic graphical models are statistical models while causal graphical models are causal models.

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#causality #statistics
It might seem like consistency is obviously true, but that is not always the case. For example, if the treatment specification is simply “get a dog” or “don’t get a dog,” this can be too coarse to yield consistency. It might be that if I were to get a puppy, I would observe 𝑌 = 1 (happiness) because I needed an energetic friend, but if I were to get an old, low-energy dog, I would observe 𝑌 = 0 (unhappiness).
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Flashcard 7074636762380

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#causality #statistics
Question
Definition 3.2 (What is a cause?) A variable 𝑋 is said to be a cause of a variable 𝑌 if 𝑌 can change in response to [...] in 𝑋
Answer
changes

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Definition 3.2 (What is a cause?) A variable 𝑋 is said to be a cause of a variable 𝑌 if 𝑌 can change in response to changes in 𝑋

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Flashcard 7074638597388

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#causality #statistics
Question
When we say “[...]” in this book, we are referring to the process of moving from a causal estimand to an equivalent statistical estimand
Answer
identification

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When we say “identification” in this book, we are referring to the process of moving from a causal estimand to an equivalent statistical estimand

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Flashcard 7074640432396

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#causality #statistics
Question
A [...] is a collection of nodes (also called “vertices”) and edges that connect the nodes.
Answer
graph

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A graph is a collection of nodes (also called “vertices”) and edges that connect the nodes.

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Flashcard 7074642267404

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#causality #statistics
Question

Assumption 3.3 (([...how strong?]) Causal Edges Assumption)

In a directed graph, every parent is a direct cause of all its children

Answer
Strict

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Assumption 3.3 ((Strict) Causal Edges Assumption) In a directed graph, every parent is a direct cause of all its children

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#causality #statistics
If there is a directed path that starts at node 𝑋 and ends at node 𝑌 , then 𝑋 is an ancestor of 𝑌
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#causality #statistics
If there is a directed path that starts at node 𝑋 and ends at node 𝑌 , 𝑌 is a descendant of 𝑋
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If there is a directed path that starts at node 𝑋 and ends at node 𝑌 , then 𝑋 is an ancestor of 𝑌 , and 𝑌 is a descendant of 𝑋

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Flashcard 7074648034572

Tags
#causality #statistics
Question
If there is a [...] path that starts at node 𝑋 and ends at node 𝑌 , then 𝑋 is an ancestor of 𝑌 , and 𝑌 is a descendant of 𝑋
Answer
directed

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If there is a directed path that starts at node 𝑋 and ends at node 𝑌 , then 𝑋 is an ancestor of 𝑌 , and 𝑌 is a descendant of 𝑋

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#causality #statistics
The causal graph for interventional distributions is simply the same graph that was used for the observational joint distribution, but with all of the edges to the intervened node(s) removed.
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The causal graph for interventional distributions is simply the same graph that was used for the observational joint distribution, but with all of the edges to the intervened node(s) removed. This is because the probability for the intervened factor has been set to 1, so we can just ignore that factor (this is the focus of the next section). Another way to see that the inter

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#causality #statistics
Association flows along all unblocked paths. In causal graphs, causation flows along directed paths.
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Association flows along all unblocked paths. In causal graphs, causation flows along directed paths. Recall from Section 1.3.2 that not only is association not causation, but causation is a sub-category of association. That’s why association and causation both flow along directed paths

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#causality #statistics
As we discussed in Section 4.2, the graph for the interventional distribution 𝑃(𝑌 | do(𝑡)) is the same as the graph for the observational distribution 𝑃(𝑌, 𝑇, 𝑋) , but with the incoming edges to 𝑇 removed.
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Flashcard 7074656947468

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#causality #statistics
Question

Definition 3.4 ([...]) Two (sets of) nodes 𝑋 and 𝑌 are d-separated by a set of nodes 𝑍 if all of the paths between (any node in) 𝑋 and (any node in) 𝑌 are blocked by 𝑍

Source: Pearl (1988), Probabilistic Reasoning in Intelligent Systems: Networks of Plausible Inference

Answer
d-separation

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Definition 3.4 (d-separation) Two (sets of) nodes 𝑋 and 𝑌 are d-separated by a set of nodes 𝑍 if all of the paths between (any node in) 𝑋 and (any node in) 𝑌 are blocked by 𝑍 Source: Pearl (1988), Probabilistic Rea

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Flashcard 7074659306764

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#causality #has-images #statistics


Question
This non-causal association flows along the [...] path
Answer
𝑇 ← 𝑋 → 𝑌

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Flashcard 7074661141772

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#causality #statistics
Question
The Positivity-[...] Tradeoff
Answer
Unconfoundedness

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The Positivity-Unconfoundedness Tradeoff

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Flashcard 7074662976780

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#causality #statistics
Question
The main reason for moving from exchangeability (Assumption 2.1) to conditional exchangeability (Assumption 2.2) was that it seemed like a more realistic assumption. However, we often cannot know for certain if conditional exchangeability holds. There may be some [...] confounders that are not part of 𝑋 , meaning conditional exchangeability is violated. Fortunately, that is not a problem in randomized experiments
Answer
unobserved

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nditional exchangeability (Assumption 2.2) was that it seemed like a more realistic assumption. However, we often cannot know for certain if conditional exchangeability holds. There may be some <span>unobserved confounders that are not part of 𝑋 , meaning conditional exchangeability is violated. Fortunately, that is not a problem in randomized experiments <span>

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Flashcard 7074664811788

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#causality #statistics
Question
More generally, the potential outcome 𝑌(𝑡) denotes what your outcome would be, if you were to take treatment [...]
Answer
𝑡

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More generally, the potential outcome 𝑌(𝑡) denotes what your outcome would be, if you were to take treatment 𝑡

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Flashcard 7074666908940

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Question
We do not have exchangeability in the data because 𝑋 is a [...] of 𝑇 and 𝑌
Answer
common cause

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We do not have exchangeability in the data because 𝑋 is a common cause of 𝑇 and 𝑌

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Article 7074675559692

实验诊断
#Diagnosis

常见的重要的血象指标和正常值 PLT 100-300*10^9/L 血小板计数 WBC 4-10*10^9/L 白细胞计数RBC 3.5-5.5*10^12/L 红细胞计数NEUT 1.2-6.8*10^9/L 中性粒细胞计数HGB 120-160g/L 血红蛋白浓度 网织红细胞是什么,正常值以及在疾病诊断中的意义? 未成熟红细胞,反映骨髓红系造血,正常值0.5%-2% 新生儿2%-6% 正常骨髓象 https://www.yixue.com/正常骨髓象 溶血性贫血的原因、表现和鉴别诊断 破坏大于代偿。 贫血、黄疸、脾大。血红蛋白尿强烈提示(但不是溶血就一定有,比如脾导致的) 鉴别原位性mds伴有网织红细胞增加 外周血细胞的分类 红白(有无粒)板 肾功能检查 检查肾功能采用什么体液,以及常用指标? 血清和尿。 肌酐、胱抑素C、二氧化碳结合力,β2微球蛋白、尿酸、尿素。 肾小球滤过率是什么,一般通过清除率来近似,清除率是什么? 单位时间内(min)经肾小球滤过的血浆量(ml) XXX清除率指的是针对某种几乎不被人体吸收(如菊粉)且经单一(肾小球)排泄的物质,单位时间内被全部清除的血浆量。 血中可以判定肾小球功能的几个指标和特点? 肌酐Cr(晚至1/3,特异)、胱抑素C(敏感,特异,最)、尿素BUN(较早)、尿酸UA(很早)、两种微球蛋白(敏感) 敏感的指标适合已确诊可损害肾功能的全身疾病患者 远近肾小管的功能 近端重吸收、远端稀释、集合浓缩 判断肾小管功能的几个指标及特点 尿比密(浓缩稀释实验,昼夜),尿渗量血渗量(浓缩稀释),尿β2(重吸收) 血浆二氧化碳结合力是干嘛的 判断肾脏平衡酸碱功能



Flashcard 7074677656844

Tags
#Diagnosis
Question
[default - edit me]
Answer
PLT 100-300*10^9/L 血小板计数 WBC 4-10*10^9/L 白细胞计数RBC 3.5-5.5*10^12/L 红细胞计数NEUT 1.2-6.8*10^9/L 中性粒细胞计数HGB 120-160g/L 血红蛋白浓度

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实验诊断
常见的重要的血象指标和正常值 PLT 100-300*10^9/L 血小板计数 WBC 4-10*10^9/L 白细胞计数RBC 3.5-5.5*10^12/L 红细胞计数NEUT 1.2-6.8*10^9/L 中性粒细胞计数HGB 120-160g/L 血红蛋白浓度 网织红细胞是什么,正常值以及在疾病诊断中的意义? 未成熟红细胞,反映骨髓红系造血,正常值0.5%-2% 新生儿2%-6% 正常骨髓象 https://www.yixue.com/正常骨髓象 溶血性贫血的原因、表现和鉴别诊断 破坏大于代偿。 贫血、黄疸、脾大。血红蛋白尿强烈提示(但不是溶血就一定有,比如脾导致的) 鉴别原位性mds伴有网织红细胞增加 外周血细胞的分类 红







Flashcard 7074679229708

Tags
#Diagnosis
Question
常见的重要的血象指标和正常值
Answer
[default - edit me]

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实验诊断
常见的重要的血象指标和正常值 PLT 100-300*10^9/L 血小板计数 WBC 4-10*10^9/L 白细胞计数RBC 3.5-5.5*10^12/L 红细胞计数NEUT 1.2-6.8*10^9/L 中性粒细胞计数HGB 120-160g/L 血红蛋白浓度 网织红细胞是什么,正常值以及在疾病诊断中的意义? 未成熟红细胞,反映骨髓红系造血,正常值0.5%-2% 新生儿2%-6% 正常骨髓







#Cryptococcus
The life cycles of both C. neoformans and C. gattii involve two distinct forms: asexual and sexual
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#Cryptococcus
The haploid (occasionally diploid in nature), unicellular yeasts are the primary forms recovered from environmental sources and human infections.
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#Cryptococcus
The asexual or yeast forms represent the primary structures seen in host tissue and recovered from cultures during clinical disease.
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#Cryptococcus
The 1- to 2-micron basidiospores, with their size and shape, have been hypothesized to be the infectious propagules. 19
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#Cryptococcus
In the 1980s, an interesting epidemiologic observation was made and confirmed by others that in most areas of the world, more than 95% of environmental and clinical C. neoformans isolates appear to contain only the alpha mating locus. 22
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#Cryptococcus
Furthermore, in certain areas within Botswana, environmental and clinical isolates do have similar numbers of both mating types, 14 so that simple exposure may be cause for the mating-type bias
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#Cryptococcus
genus Cryptococcus comprises 19 species, loosely characterized as a variety of encapsulated yeasts.
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#Cryptococcus
Therefore any human infection with a cryptococcal species other than C. neoformans or C. gattii needs rigorous histopathology and cultural proof of invasive disease.
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#Cryptococcus
For several decades, C. neoformans strains had been grouped into two varieties that included five serotypes based on their capsular structure. C. neoformans var. neoformans and C. neoformans var. grubii included strains with serotypes A, D, and AD, and C. gattii contained strains with serotypes B and C. The serotype classification (A–D) describes antigenic differences in the structure of the polysaccharide capsule; these differences are detected by antibodies from rabbit sera 29 or by specific monoclonal antibodies. 30,31
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#Cryptococcus
The stable taxonomic classification of these varieties and serotypes has now evolved through new genomic analyses, and several new changes have been proposed. 32
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#Cryptococcus
However, at present, for clinicians the standard serotype classification used for half a century and the split into two varieties, var. neoformans and var. grubii, and two species, C. neoformans and C. gattii, still remain useful nomenclature for describing the clinical strain differences in epidemiology, pathogenesis, and clinical features
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#Cryptococcus
The anamorph (yeast or asexual stage) dominates clinical discussion of this encapsulated yeast. On the other hand, the teleomorph, with its more complex structure and its genome sequences, places this fungus within the basidiomycete family, and its teleomorph genus name is Filobasidiella.
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#Cryptococcus
Thus the teleomorph of serotypes A and D strains is called Filobasidiella neoformans and the teleomorph of serotypes B and C strains is designated Filobasidiella bacillispora; however, these teleomorphic names are not used in clinical practice
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#Cryptococcus
On most routine laboratory agar media, colonies of C. neoformans and C. gattii appear within 48 to 72 hours after plating a specimen
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#Cryptococcus
Some selective fungal media containing cycloheximide inhibit the growth of this yeast and thus should not be used.
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#Cryptococcus
For blood cultures, the lysis- centrifugation method works well for isolating Cryptococcus but is no longer necessary because automated blood culture methods can reliably detect cryptococcemia, which is commonly observed in severely immunosuppressed patients such as patients with acquired immuno- deficiency syndrome (AIDS) and disseminated disease. 35
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#Cryptococcus
However, cryptococcemia rarely produces symptoms of hypotension or septic shock
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#Cryptococcus
On agar plates, the yeast colony grows as a white-to-cream–colored, opaque colony several millimeters in diameter. The colonies typically become mucoid with prolonged incubation, reflecting increased polysac- charide capsule formation.
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#Cryptococcus
Colonies occasionally develop sectors that differ in pigmentation or exhibit morphologic changes (e.g., smooth or wrinkled). In fact, C. neoformans has been shown to possess the ability to produce a morphologic switching colony phenotype, which explains the variety of colony shapes in some strains and emphasizes the plasticity of the cryptococcal genome. 36,37
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#Cryptococcus
The optimal environmental growth temperature for the majority of C. neoformans strains is between 30° and 35°C, with a maximum tolerated temperature for most strains at 40°C.
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#Cryptococcus
C. neoformans and C. gattii strains generally grow well at 37°C, with doubling generation times of 3 to 6 hours, and this high-temperature growth characteristic is a primary virulence phenotype that separates them from other cryptococcal species that generally do not either grow or survive well at mammalian body temperatures and thus are rarely found to be human pathogens
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#Cryptococcus
First, placing the yeast into an India ink preparation for microscopy may reveal the encapsulation of the yeast. The capsule is generally better seen in direct clinical specimens from the host and may not be as apparent in wet mounts made from in vitro cultures. This finding occurs because capsule production is induced by certain environmental cues, such as elevated carbon dioxide concentrations, serum, urea, or limited iron conditions. In fact, the mammalian host environment provides an ideal environment for capsule production
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#Cryptococcus
Second, a rapid urease test is positive for most Cryptococcus species. Cryptococcus species, unlike Candida species, possess urease, an enzyme that hydrolyzes urea to ammonia and increases the ambient pH. A positive urease test can be detected in the laboratory within minutes. 42 Several nonpathogenic yeasts can produce abundant urease, and Trichosporon species may be weakly urease positive
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#Cryptococcus
Third, C. neoformans is one of the few yeast species that possesses prominent activity of laccase, 43 an enzyme that allows the conversion of diphenolic compounds into melanin. Detection of this unique biologic characteristic is possible with media containing niger seed (birdseed), caffeic acid, or dopamine. Yeast colonies that turn brown to black on these special agars are identified as melanin positive.
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#Cryptococcus
Microscopically, most clinical isolates appear as spherical, narrow-based, budding, encapsulated yeast cells in both tissue and culture
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#Cryptococcus
Short hyphal or pseudohyphal structures may exist in vivo, or under certain stress conditions in vitro, but these structures are rarely observed unless certain in vitro nutrient conditions for mating or haploid fruiting are met.
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#Cryptococcus
The yeast cells vary in size from 5 to 10 microns in diameter, and they exhibit single or multiple buds. Because the buds are readily detached from their parental cells, the majority of yeast cells in both tissue and culture lack buds.
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#Cryptococcus
In tissue, Cryptococcus has the ability to produce large (titan) cells of 50 to 100 μm, which possess features such as aneuploidy and large antiphagocytic capsules that promote their survival. 44
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#Cryptococcus
There are three methods for identifying the four serotypes.
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#Cryptococcus
Third, analysis of DNA base composition is extremely accurate. Comparison of sequenced genomes of these serotypes shows an approximately 6% to 8% overall difference in nucleotide sequences between serotype A and D strains and an even greater difference between these strains and serotype B and C strains. 13
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#Cryptococcus
Along with genome sequencing, MALDI-TOF mass spectrometry has also become a precise and facile method for distinguishing cryptococcal strains in the laboratory. 41
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#Cryptococcus
C. neoformans and C. gattii are saprobes in nature. 49
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#Cryptococcus
C. neoformans was first described in fruits, but after years of investigation it is clear that it also has an environmental niche or habitat associated with certain trees and rotting wood. A second consistent finding is that C. neoformans has frequently been isolated from soil contaminated by guano from birds. 50,51
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#Cryptococcus
On the other hand, C. gattii clearly has an environmental association with trees, from eucalyptus to a variety of coniferous trees, but not bird guano. 52
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#Cryptococcus
However, the soils most enriched in C. neoformans are those that are frequented by birds, especially pigeons, turkeys, and chickens. Guano from other birds, such as canaries and parrots, has also yielded the yeast
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#Cryptococcus
Occasionally, birds develop disease that involves C. neoformans, but this is relatively unusual
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#Cryptococcus
The resistance of birds to disease may result from their very high body temperature, which is not conducive to growth of C. neoformans, and possibly even their innate protective immunity.
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#Cryptococcus
Furthermore, there appears to be a certain geographic limitation to the occurrence of infections with this variety. With this knowledge base, investigators were initially able to culture C. gattii from vegetation around and associated with the river red gum trees (Eucalyptus camaldulensis) and forest red gum trees (Eucalyptus tereticornis) in Australia. 53
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#Cryptococcus
However, despite the association of these trees with C. gattii, the outbreak of cryptococcosis on Vancouver Island, British Columbia, revealed that other trees such as firs, maples, and oaks may also be an ecologic niche for specific strains of C. gattii. 54
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#Cryptococcus
It is proposed that these new geographic locations and specific envi- ronmental niches for C. gattii could be due to recent climate changes. 52
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#Cryptococcus
C. neoformans is not generally considered to be a routine constituent of the human microbiota
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#Cryptococcus
When C. neoformans is isolated from nonsterile clinical specimens, the clinician must examine the patient for evidence of disease and analyze risk factors for the potential development of disease before planning further management strategies.
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#Cryptococcus
Research has shown that patients with cryptococcosis have delayed hypersensitivity to cryptococcal antigens, 59 and the prevalence of positive skin test reactions in pigeon fanciers and laboratory workers engaged in research activities with this yeast has been reported to be high. 60 Unfortunately, there is no established skin test for routine clinical use in patients with cryptococcosis today, and this reduces our ability to assess the magnitude of this infection
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#Cryptococcus
The vast majority of patients with symptomatic disseminated cryp- tococcosis have a clearly identified underlying immunocompromised condition (Table 262.1). The most common underlying conditions worldwide include AIDS, prolonged treatment with corticosteroids, organ transplantation, advanced malignancy, diabetes, and sarcoidosis
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#Cryptococcus
In fact, occurrence of cryptococcosis may identify an underlying idiopathic CD4 lymphocytopenia 64 or the development of certain autoantibod- ies, or be associated with the use of the specific immune-modifying monoclonal antibodies, such as alemtuzumab, infliximab, etanercept, and adalimumab. 65,66
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#Cryptococcus
Finally, it has been estimated that approximately 20% of patients who have cryptococcosis without HIV infection have no apparent underlying disease or risk factor. 67 The genetic susceptibility to cryptococcal disease has been clearly determined in murine models but needs more studies in humans.
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#Cryptococcus
However, most adults possess specific antibodies to C. neoformans antigens; for instance, in New York City, most children acquire antibodies to cryptococcal antigens before the age of 10 years. 61,62 These observations suggest that there are frequent asymptomatic infections.
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[unknown IMAGE 7075511012620]
Cryptococcose
#Cryptococcus #has-images
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#Cryptococcus
The best estimates for rates of cryptococcosis in the United States in the pre-AIDS era predicted an overall incidence of 0.8 case per 1 million persons per year. In 1992, during the peak of the AIDS epidemic in the United States, the rate reached almost 5 cases of cryptococcosis per 100,000 persons per year in several large cities.
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#Cryptococcus
In the AIDS population in developed countries, it now generally represents an infection that identifies a disadvantaged patient or an untreated and undiagnosed HIV infection. Thus cryptococcosis in patients with AIDS identifies a group as having or wanting less access to medical care, or both. 76
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#Cryptococcus
In fact, the risk of cryptococcosis appears higher for African-born individuals even when they move to industri- alized nations. 82
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#Cryptococcus
In many African medical centers, cryptococcosis represents the most common cause of culture-proven meningitis, even surpassing Neisseria meningitidis and Streptococcus pneumoniae meningitis. 81
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#Cryptococcus
Increasing cases of cryptococcosis have consistently followed the pattern of HIV infections, and in countries such as Thailand, blood cultures done before widely available ART frequently contained this yeast. However, with increased availability of ART in sub-Saharan Africa and Asia, the magnitude of these observations has changed. 83
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#Cryptococcus
Cryptococcosis has a measurable rate of infection in two other major risk groups: cancer patients and recipients of solid-organ transplants.
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#Cryptococcus
Since the 1950s, it has been known that patients with lymphoproliferative disorders and certain hematologic malignancies, such as chronic lym- phocytic leukemia, were at higher risk than the general population for cryptococcosis. 95–98
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#Cryptococcus
On the other hand, checkpoint inhibitors to programmed cell death protein-1 for cancer treatment may actually be preventive with their actions against cryptococcosis. 101
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#Cryptococcus
A retrospective analysis of case reports from a single large cancer center from 1989 to 1999 reported that the incidence of cryptococcosis was 18 cases per 100,000 admissions, and the occurrence is predicted to increase with further frequent use of cell-mediated immune inhibitors, such as alemtuzumab, ibrutinib, and fludarabine, in the management of certain malignancies. 99,100
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#Cryptococcus
In one cohort, cryptococcosis occurred in 2.8% of all solid-organ transplant recipients. 102 Kidney and liver transplant recipients appear to have the highest risk for cryptococcosis. 102–104
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#Cryptococcus
In contrast, in bone marrow transplant recipi- ents, who have a high incidence of fungal infections, cryptococcosis is not common. 105
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#Cryptococcus
Sarcoidosis, with or without corticosteroid therapy, predisposes to cryptococcosis and can be a diagnostic dilemma. The lung, skin, bone, and CNS lesions of the two diseases overlap clinically and by histopathol- ogy. Despite uncertain pathophysiology, diabetes as an underlying disease or cofactor is frequently mentioned in those patients without HIV or transplant recipient risk factors in most reviews
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#Cryptococcus
Cryptococcosis can occur before puberty, but even in children with several known risk factors the incidence is uncommon, and in an area of high HIV prevalence only 2% of cryptococcosis cases were in children. 111
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#Cryptococcus
In adults, idiopathic CD4 + T-cell lymphocytopenia may be identified by the development of disseminated cryptococcosis, and paradoxically this underlying condition with cryptococcosis actually may have a good prognosis for treatment outcome. 64,114
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#Cryptococcus
There is general agreement that most cryptococcal infections are acquired primarily by inhalation of infectious propagules, but there are occasional cases of direct traumatic inoculation through contaminated environmental projectiles or laboratory/clinical accidents such as needle- sticks. 117,118
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#Cryptococcus
It is hypothesized that either dehydrated, poorly encapsulated yeast cells or basidiospores (< 5 μm) are needed as infectious propagules for alveolar deposition in the lungs. 19
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#Cryptococcus
Studies at sites with contaminated soils or trees have found that the surrounding air contains the correct size of propagules for airway infection. 119–121
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#Cryptococcus
Although associations between infection and environmental exposure have been reported for many of the classic dimorphic fungi, this association is rare for C. neoformans.
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#Cryptococcus
Human-to-human transmission of cryptococcosis has not been reported except in cases of contaminated transplant tissue. 51,106,107
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#Cryptococcus
Many species of animals, including dogs and cats, can develop cryptococ- cosis, 127–129 but there is infrequent evidence of zoonotic transmission between them and humans. In one case, C. neoformans isolated from the cage of a pet cockatoo was molecularly linked with the strain that caused infection in a transplant recipient who was exposed to the cage. 130 Also, several cryptococcal cases have been linked to intense bird exposures, 131 and even a possible nosocomial outbreak of cryptococcosis in an intensive care unit has been reported. 132
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