MIcrobiology Exam 2 - Parasitology and Mycology

Question 1

Parasite definition

Answer 1

an organism living in or on another and benefiting at the expense of the other (technically includes all flora found in and on us

• generally reserved for eukaryotic organisms
• includes broad range of animals

Question 2

parasites examples

Answer 2

malaria
giardiasis
ascariasis
toxocariasis
head lice
acanthamoeba

Question 3

malaria - what it means, bug involved and what carries (transmits) it

Answer 3

“bad air”
blood parasites of the protozoan genus Plasmodium
Anopheles mosquito

Question 4

what species infect humans with malaria?

Answer 4

4 of them:
P. falciparum
P. vivax
P. ovale
P. malariae
*don't have to list these from memory, but should be able to recognize for exam

Question 5

which malaria-infecting species is predominant in endemic regions?

Answer 5

P. falciparum

Question 6

malaria epidemiology and transmission

Answer 6

epidemiology:
350-500 mill infections/yr w/ high rate of mortality (about 1 mill deaths annually, mostly young children)
transmitted by the Anopheles mosquito (vector)
geographic distribution correlates to vector (mostly tropical areas)

Question 7

1st stage of malaria

Answer 7

human liver stage (exo-erythrocytic cycle, is OUTSIDE the blood)
sporozoites from mosquito infect liver cell -> mature into schizonts (many more progeny are made) ->schizont ruptures and releases merozoites -> they enter the next stage

Question 8

2nd stage of malaria

Answer 8

human blood stage (erythrocytic cycle)
undergo asexual replication in erythrocytes and infect RBC’s -> immature trophozoite (ring stage) -> either goes back into schizont stage w/ rupture OR matures and -> becomes gametocytes

Question 9

3rd stage of malaria

Answer 9

mosquito stages
gametocytes (male=micro, female=macro) ingested by Anopheles mosquito during a blood meal -> sporogonic cycle (parasites multiply) -> micros penetrate macros, generate a zygote -> zygotes become motile and elongated -> invade the midgut wall of mosquito and develop into oocysts -> oocysts grow, rupture, release sporozoites -> they go to mosquito’s salivary glands -> mosquito bites human

Question 10

how many hosts does the parasite life cycle involve?

Answer 10

2 (human and mosquito)

Question 11

malaria clinical findings

Answer 11

uncomplicated:
-fever, chills, sweats, headache, nausea, vomiting, myalgia, weakness
-can get involvement of spleen, kidneys, lungs, NS
severe (particularly P. falciparum):
-cerbral malaria, severe anemia, hemoglobinuria, pulmonary edema or ARDS, reduced platelets, cardio collapse and shock
-relapses seen w/ P. vivax or P. ovale (will get dormant pop.’s called “hypnozoites, which can then lead to a relapse)

Question 12

dx and tx for malaria

Answer 12

dx: microscopy (look for schizonts in culture)
tx: variety of compounds
-> chloroquine and quinine (blocks heme detoxification)
• Resistance levels are high
– Vaccine development currently unsuccessful

Question 13

giardiasis - what is it and where found

Answer 13

Protozoan flagellate Giardia intestinalis (the one that infects humans)
• Worldwide distribution, common in United States

Question 14

giardiasis transmission

Answer 14

contaminated water, food or hands/fomites with infective cysts (trophozoites are also passed in stool but do not survive the environment)

Question 15

giardiasis clinical findings

Answer 15

– Incubation 1 to 14 days
– Self limiting infection typically 1 to 3 weeks
– Diarrhea, abdominal pain, bloating, nausea, vomiting
• Can become chronic

Question 16

dx and tx for giardiasis

Answer 16

Diagnosed by microscopy
• Cysts or trophozoites in feces
– Treated with metronidazole and tinidazole

Question 17

toxocara - what is it and where found

Answer 17

Nematode Toxocara canis or T. cati
– Dog or cat roundworm
• Worldwide distribution

Question 18

toxocara transmission

Answer 18

we get exposed to infected animal’s feces in environment, gets into us, but parasite gets “lost” in our body b/c not in its home

Question 19

toxocara clinical findings

Answer 19

Many asymptomatic infections with +ve serology
– Visceral larval migrans (VLM)
• Mostly preschool children
• Larva invade liver, heart, lungs, brain, muscle
• Fever, anorexia, weight loss, cough, wheezing, rashes, hepatosplenomegaly, hypereosinophilia
• Death (rare) due to heart/lung/neurological involvement
– Ocular larval migrans
• Opthalmological lesions and damage to eye
• Risk of misdiagnosis as retinoblastoma

Question 20

toxocara dx and tx

Answer 20

Diagnoses by history, symptoms and antibodies

– Treatment with albendazole (targets microtubules) and anti-inflammatories

Question 21

ascariasis - what and where found

Answer 21

Nematode Ascarislumbricoides
• Worldwide distribution
– Most common helminthic infection
– Rural areas of southeastern United States

Question 22

ascariasis transmission

Answer 22

feces, hand to mouth, poor personal hygiene

-can migrate viscerally to the lungs; you cough them up and then swallow them -> back down the intestinal tract (yuck).

Question 23

ascariasis clinical findings

Answer 23

Usually no acute symptoms
– High body burden can cause abdominal pain due to obstruction
– Migrating adults can block biliary track or be expelled orally
– Can develop pulmonary symptoms during larval migration (Loeffler’s syndrome)

Question 24

ascariasis dx and tx

Answer 24

– Diagnoses by microscopy of stool

– Effective drug treatment (ex. albendazole)

Question 25

head lice - what and where

Answer 25

• Pediculosis • Pediculus humanus capitis – a human ectoparasite found everywhere?

Question 26

lice transmission

Answer 26

Some transmission via fomites

Question 27

lice clinical findings

Answer 27

Majority of infestation are asymptomatic – Symptoms include “tickling feeling of something moving in the hair”, itching (an allergic reaction to louse saliva), and irritability • Secondary bacterial infection can be a complication

Question 28

fungi types

Answer 28

Molds, yeast and fleshy fungi | • 150 species are pathogenic to humans

Question 29

fungi structure

Answer 29

Similar to other eukaryotes – Nuclei, mitochondria, 80S ribosome, etc.Thick cell walls comprised of *glucans or chitin* (know that) – Unlike bacterial bacterial peptidoglycan • Membranes contain ergosterol and zymosterol – Unlike us (we have cholesterol)

Question 30

fungi reproduction

Answer 30

Reproduce by asexual budding or sexual spores | • Play an important role in turnover of nutrients in the environment

Question 31

yeast - what and reproduction

Answer 31

Unicellular fungi – larger than most bacteria • Reproduce primarily by budding – fungi imperfecti

Question 32

medically relevant species of fungi

Answer 32

– Exogenous - Cryptococcus neoformans, Aspergillus – Endogenous - Candida

Question 33

candida - what

Answer 33

Normal flora of the oral cavity, gut, vagina and occasionally the skin – Candida albicans, C. glabrata, and others • Yeast phase referred to as blastospores – Single, oval buds - 5µm • Can form elongated filaments – pseudohyphae

Question 34

candida control and defense

Answer 34

Generally, Candida exists as a normal component of the oral flora BUT can become an opportunistic pathogen • Kept in check by … – Physical barriers, saliva, microbial competition and phagocytosis – sIgA can restrict surface adhesion

Question 35

when candida goes bad, what can happen?

Answer 35

Vulvovaginal candidiasis (VVC) – “yeast infection” – Overgrowth in response to hormonal changes, pH change, change in normal flora – Itching/burning sensation – Readily diagnosed with microscopy • Invasive candidiasis – Candidemia and disseminated infection – *Neonates, surgical patients, immunosuppressed – Fever and chills that are unresponsive to antibiotics – *(systemic) involvement of kidney, liver, bone, muscle, joints, spleen or eyes – *Death due to organ failure in 50% of untreated cases – Diagnosed by microscopy In the oral cavity you get a superficial mycoses • Oropharyngeal candidiasis (OPC) – proliferation triggering inflammation – ex. white pseudomembrane on buccal mucosa • Pseudomembranous candidiasis – Thrush – No penetration of epithelium – Easily wiped off revealing raw, inflamed tissue underneath

Question 36

factors predisposing to pseudomembranous candidiasis (thrush)

Answer 36

``` chronic local irritants ill-fitting appliances inadequate care of appliances disturbed oral ecology or marked changes in the oral microbial flora by antibiotics, corticosteroids, xerostomia dietary factors immunological and endocrine disorders (e.g. diabetes mellitus) malignant and chronic diseases (can be an indicator of a more severe systemic infection - want to find out the cause) severe blood dyscrasias radiation to the head and neck abnormal nutrition age (very young or very old) hospitalization oral epithelial dysplasia heavy smoking ```

Question 37

agar used to culture candidiasis

Answer 37

Sabouraud agar | **this has been on boards

Question 38

other types of candida and associated lesions

Answer 38

``` Oral mucosa – Erythematous candidiasis – Hyperplastic candidiasis (these 2 are a little different, he didn't know how) • Associated lesions – Denture stomatitis – Median rhomboid glossitis (one of many causes?) – Angular cheilitis ```

Question 39

tx for candidiasis

Answer 39

``` • Polyenes – ex. Nystatin, Amphotericin B – Binds ergosterols in membrane causing leakage • Azoles – ex. Fluconazole, Miconazole – Inhibits ergosterol synthesis – **resistance high in C. glabrata** -> KNOW • Echinocandin B – Interferes with glucan synthesis (targets glucan of cell walls instead of sterols) ```

Question 40

cryptococcosis - what, transmission, epidemiology

Answer 40

Cryptococcus neoformans – Normal flora in birds (pigeons) -> NOT normal for us (is exogenous pathogen) – Transmitted by inhalation Epidemiology: - High mortality (12% in US, 75-90% in Africa)

Question 41

cryptococcosis symptoms

Answer 41

Symptoms similar to pneumonia | – Can lead to fungaemia, meningoencephalitis

Question 42

cryptococcosis tx

Answer 42

Treated with fluconazole and amphotericin

Question 43

aspergillosis - what

Answer 43

Aspergillusspp. (A. fumigatus, A. flavus, etc.) | – Found in soil, plants, decaying organic matter

Question 44

aspergillosis types with symptoms

Answer 44

Allergic bronchopulmonary aspergillosis (ABPA) – Wheezing/coughing • Aspergilloma (fungus ball) in lung or other organs • Invasive aspergillosis – Fever, chest pain, cough, shortness of breath – Dissemination throughout organs, including brain – Treated with voriconazole (cytochrome target)

Question 45

dermatophytes - what

Answer 45

Tinea or ringworm • Caused by many species of fungi – Trichophyton rubrum, T. tonsurans – Microsporum canus

Question 46

dermatophytes transmission

Answer 46

Spread by contact

Question 47

dermatophytes types

Answer 47

``` Appears as infections on the skin, hair, or nails – Tinea barbae – beard – Tinea corporis – body – Tinea pedis – feet (athelete’s foot) – Tinea cruris – groin (jock itch) – Tinea capitis – scalp ```

Question 48

dermatophytes clinical findings

Answer 48

Symptoms: – Appear 4-14 days post-exposure – Itchy, red, raised, scaly patches that may blister and ooze – Sharply-defined edges, often redder than adjacent tissue, and may be “ring-like” – Balding patches in hair – Thick, discolored and perhaps crumbly nails

Question 49

dx and tx

Answer 49

Diagnosed by KOH test, biopsy and culture • Treated with topicals (miconazole, clotrimazole, etc.) or systemically (ketoconazole) • Controlled with good hygiene

Question 50

In what stage of malaria do you see clinical manifestations of the disease?

Answer 50

The blood stage

Question 51

What are the 2 kinds of larva in toxocariasis?

Answer 51

Visceral larval migrans (affects liver, lungs, heart, brain, muscles) - death in rare cases Ocular larval migrans (lesions/damage to eye, often misdiagnosed as retinoblastoma)

Question 52

Most common helminthic infection

Answer 52

Ascariasis

Question 53

What is albendazole effective at treating?

Answer 53

Infections due to "wormy" stuff; i.e. Toxocariasis and Ascariasis

Question 54

Other oral types of candidiasis besides pseudomembranous

Answer 54

"Eh" (b/c Jardine didn't know much about) Erythmatous candidiasis Hyperplastic candidiasis

Question 55

In what yeast is resistance to azoles (drugs) high?

Answer 55

C. glabrata