MMI 445 > Yeasts > Flashcards

Yeasts Flashcards

(52 cards)

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1
Q

Yeast

A

any unicellular fungus with an oval or elliptical shape that reproduces via budding or fission

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2
Q

In human infections wheredoes the yeast typically come from?

A

frm our endogenous flora

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3
Q

What are some relavent pathogenic yeasts?

A

Candida spp (big one)
Cryptococcus spp (big one)
Malassezia spp
Trichosporon spp

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4
Q

What are common yeast contaminants?

A

Rhodoturla spp
Saccharomyces spp

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5
Q

What fungal pathogens are in the critical priority group?

A

Cryptococcus neoformans
Candida auris
Candida albicans
Aspergillus fumigatus

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6
Q

What fungal pathogens are in the high priority group?

A

Nakaseomyces glabrata
Eumycetoma caustive agents
Fusarium spp
Candida parapsilosis
Histoplasma spp
Mucorales
Candida tropicalis

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7
Q

Are yeast acctually gram positive?

A

No, it des not have peptodoglycan

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8
Q

Blastoconidium

A

Conidium formed by budding along hyphae, psudohyphae, or single cells

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9
Q

Budding

A

Proccess of asexual reproduction by yeast and yeast-like fungi

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10
Q

Chlamydospore

A

thick walled conidium frmed within the hyphal structure

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11
Q

Canidium

A

an asexua spore produced on a conidophore of certain fungi

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12
Q

Pseudophyphae

A

chain of budding yeast that when elongated, resemble true hyphae

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13
Q

Septate

A

septation formed by cross-walls

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14
Q

A 28 year old female comes to the ED with a “gnarly fever”.
In the ED, she is febrile to 38.4, tachycardic and hypotensive,
but still mentating well enough to curse at everyone. The
patient is a known IVDU with multiple past cases of
bacteremia. She is admitted and put on vancomycin,
meropenem, and fluconazole while awaiting blood culture
results. 2/2 sets become positive with a small, oval yeast. No
pseudohyphae are present in the Gram stain of the broth.
What are your recommendations?

A. No identification or susceptibility testing is warranted
because fluconazole broadly covers yeast
B. The isolate may not be covered by the agents and
identification and susceptibility testing is warranted
C. Candida in a blood culture of a person with a catheter is
typically a contaminant and therefore no identification and
susceptibility is necessary
D. The isolate is likely to be C. albicans and almost all are
fluconazole susceptible, therefore identification and
susceptibility testing will only be performed per physician
request

A

B

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15
Q

Candida

A
  • > 150 species identified
  • <20 species cause human disease
  • C. albicans is the most common and most studied species responsible for 40-70% of invasive candidiasis
  • treatable (important to recognize and treat the infection ASAP)
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16
Q

What are some species of Candida that cause human disease?

A

C. albicans
C. dubliniensis
C. tropicalis
C. glabrata
C. krusei
C. parapsilosis
C. lusitaniae
C. gullermondii

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17
Q

Where does Candiada colonize in humans?

A

Everywhere (found in the mouth, vagina, anus, skin and in the urine)

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18
Q

Candidiasis

A
  • source of infection is the patient (colonizes skin, GI tract, mouth, vaginal tract)
  • most common fungal opportunist (causes >7-% of invasive fungal infections in hospitalized paitents)
  • risk factors: broad spectrum antibiotics, use of central venous cathedars, immunosuppresive agents, implantable devices, IVDU
  • Complications include endocarditis, endophthalmitis, osteomyelitis, meningitis (rare)
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19
Q

How does Candida go from colonizing the body naturally to causing infection?

A
  1. Increase of moisture, warmth and nutrients along with the imbalance of your natural flora (this can be due to infancy, antibiotics, pregnancy, or GI disease) can lead to an increase of Candida on your body
  2. thei increase of Candida along with epithelial damage (caused by trauma to the epithelium or physilogical changes such as hormones, old age, diabetes, HIV or cancer) can lead to superfical Candidiasis
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20
Q

What are the different presentations of Superficial Candidiasis

A
  • mucocutaneus: thrush, genitourinary infection
  • Cutaneous, Onychomycosis, Keratitis
  • GI candidiasis
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21
Q

Oropharyngeal Candidiasis (OPC)

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A
  • C. albicans is the most common cause
  • diagnosis by clinical examination is most common
  • Risks: 80-90% of HIV paitents, antibiotic/steroid users
  • Manifestations: Thrush (white psudomembranous plauque, erythematous lesions in mouth) and red, inflamed lesions in the mouth
22
Q

Cutaneous Candidiasis

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A

Diper Rahs resulting from colonization and mositure

23
Q

Onycomycosis

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A

occupational disease (dishwashers, bartenders, fruit pickers)
Induced by exposure coupled with moisture and skin breakdown

24
Q

Candida Vulvovaginitis

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A
  • Candida isolated from the genital tract of 20-50% of asymptomatic woman
  • risk factors for colonization: diabetes, corticosteroids, antibiotics, oral contraceptives
  • Vaginitis most common in woman with diabetes, immune deficency (HIV), antibiotic use, pregnancy
  • Most commonly cuased by C. albicans
25
Ho does Canidiasis go from superficial to deep tissue infection?
1. Superfical Candidiasis can cause epithelial trauma (burn or I ulcer) or there may be direct access required for the pitent such as indwelling cathedar, surgery, or hyperalimentatin (feeding through a line) which can lead to heavy Candidemia 2. Medication the paitent takes (such as immunosuppression or corticosteroids) may impair defenses of the body against pathogenic yeast which may lead to light candidemia along with superficial candidiasis 3. this heavy candidemia or light candidemia paired with impired defenses can lead to systemic candidiasis + sequelae
26
What are the different presentations of Systemic Candidiasis
Endocarditis, meningitis, osteomyelitis, endophthalmitis, bloodstream infection, UTI
27
Candida fungemia (candidemia)
- portal of entry is usually GI tract or vascular catheter (fungal biofilm) - signs and symptoms are fever, low blood pressure, skin leisons, visual changes, abscesses - diagnosis: blood culture, culture of tissue biopsy - most paitents with candidemia should have an eye exam to rule out fungal eye infection - all positive blood cultures require treatment (lines must be removed, mortality rates increase with delayed treatment)
28
How is Candida spp identified?
- direct exam (budding yeast with or without pseudohyphae, purple by gram stain, and 3-6uM in diameter - culture (grow well on non-specilized agar, selective agar is used for non-sterile specimens; colony morphology is smooth, wrickled, creamy colonies and there is starring of C. albicans and C. dubliniensis; can use chromogenic agar and primary identification mthods include biochemical and MALDI-TOF MS)
29
Candida auris
- emerging multi-drug resistant yeast that is highly transmissable\- case and transmission have increased i he US since 2019 - 85% resistant to azole, 33% resistant to amphotericin B and 1% resistant to echinocandins - Pan resistant and echinocandin resistant isolates have been recovered in the US - Echinocandin-resistant isolates are increaseing - Prompt identification of indivisuals infected or colonized with C. auris is critical to iniciate infection control measures and prevent spread
30
Epidemiology of C. auris
worldwide (South Asia Clade I, East Asia Clade II, South AFrica Clade II, and South America Clade IV)- these are the different linages and they are found past these 4 areas of the world aswell
31
C. auris in Canada
- 2012-2024: 63 total cases reported to NML - 2/3 reported recent healthcare outside of Canada - 74% of cases were fluconazole resistant - 1/3 cases were multidrug resistant - No echinocandin resistance reported - all 4 clades have been reported
32
Case Study: - 38-year-old HIV-positive male with a CD4 count of 80. The patient had a 1-week history of progressively worsening headache, photophobia, lethargy and fevers to 38.5C. On morning of admission, he became confused, disoriented and ataxic, having fallen 3 times. - Vital signs were within normal limits. Chest X-ray and head CT scan normal. - LP performed. CSF revealed 32 WBC/uL, glucose 22mg/dL, protein 89mg/dL. - Serum and CSF tests for the presence of a specific antigen were positive. What is it?
Cryptococcus
33
Cryptococcus
- yeats, round, typcially non-budding with a thick capsule - worldwide distrabution - most common species of non- Candida yeast isolated from clinical specimens - major species C. neoformans and C. grattii
34
Cryptococcus neoformans
- found worldwide - found in soil, on decaying wood, bird droppings - HIV or other immunocomprimised (transplant/cancer) populations are most at risk - not contagious - signifigant morbidity/mortality in resource poor setting
35
Cryptococcus gattii
- Found in sub tropical areas (Australia and Papua New Guinea in particular)-more limited distrabution - Since 1999, found to cause human and animal infections on Vancouver Island and Pacific Northwest - Found in soil and in association with certain tree types - become infected when C. gattii becomes inhaled and enters lungs of the host and the small size of the yeast/spores allows them to become lodged deep in lung tissue - Immunocompetent and immunocomprimised patients - not contagious - rare compared to C. neoformans infection
36
Cryptococcosis
- primary pulmonary infection after inhalation of yeasts (asymtomatic carriage or invasive pulmonary cryptococcosis) - pneumonia, meningitis, or disseminated disease (skin) possible - risk factors fo disease: HIV/AIDs, hematological malignancy, steroids
37
Cryptococcus meningitis
- immunocomprimised patients - acute onset with very rapid deterioration - presents with fever, headache, and nausea - untreated crytococcal meningitis has 100% mortality within first 2 weeks of hospitalization - mortality rate in treated cryptococcal meningitis remains about 10-20% - 220 000 cases of crytococcal meningitis worldwide/year
38
C. gattii outbreak in Pacific Northwest
- between 1999-2007, 218 C. gattii cases ith an average of 24.2 cases/year - mainland BC: 5.8 cases/million, Vancouver Island: 25.1 cases/million - 19 deaths from C. gattii documented (8.7% fatlity rate) - cases have been documented in the Pacific Northwest since 2004 and continue to occur
39
Cryptococcus Diagnosis
1. Direct Microscopy: gram stain, India Ink, Calcoflour (CSF, skin nodule aspirate, lung biopsy) 2. Culture and Identification (CSF, tissue, blood) 3. Histopathology 4. Cryptococcal antigen (serum, CSF)
40
Gram Stain
yeast cells stain Gram pos while capsule stain gram neg
41
India Ink
- negative stain - yeast is seen in a dark background surrounded by a clear "halo" - considered a traditional method, antigen testing of CSF is much more sensitive - not used in North America pretty much anymore
42
Cryptococcus Capsule
- composed of high molecular weight polysaccharide- glucuronoxylomannan (GXM- 90%) - excludes ink - avoids immun system (protects from phagocytosis and barrier for complment) - mutants defective in capsule biosynthesis are avirulent
43
Describe C. neoformans before and after entry into lungs?
Before: in high glucose or salt conditions C. neoformans becomes weakly encapsulated. These are very small and this is necissary for the organism to get into the alveolar spces in the lungs After: once in the lungs the organism can become rehydrated and acquire the thick polysaccharide capsule
44
C. neoformans (urea, birdseed agar, caffeic acid, and CGB tests)
Urea: + Birdseed Agar: + Caffeic Acid:+ CGB: -
45
C. gattii (urea, birdseed agar, caffeic acid, and CGB tests)
Urea: + Birdseed Agar: + Caffeic Acid: + CGB: +
46
Other Cryptococcus sp. (urea, birdseed agar, caffeic acid, and CGB tests)
Urea: + Birdseed Agar: - Caffeic Acid: - CGB: -
47
What is similar between all cultures of Cryptococcus spp?
their morphology is indistinguishable
48
Melanin
- deposited in inner cell wall - protects fungal cell from respiratory burst of human phagocytes - mutants that cannot produce melanin have reduced virulence
49
Histopathology of Cryptococcus
- consistently round cells - variable size: 5-25um - narrow based budding cells ( not always apparent) - capsule apparent
50
Cryptococcal Antigen Test
- Performed on serum and CSF - Capsular polysaccharide is detected by reacting with antibodies specific for antigen - sensitive and specific - use is 2-fold: diagnosis and following response to treatment
51
Rhodoturula
- grows in the shower - common contaminent - has been associated with severe infections (meningitis, keratitis, endocarditis) in immunosuppressed patients with central venous catheders
52
Saccharomyces
- common contaminant - used in winemaking, baking, and brewing - fungemia becoming more common in paitents receiving probiotics for prophylaxis or treatment of antibiotic associated diarrhea - nosicomial spread has benn documented
MMI 445
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