Transcript 14 Fungi and Protozoa

Fungi and Protozoa
Nestor T. Hilvano, M.D., M.P.H.
Images Copyright by Bauman, Robert. 2009. Microbiology, With
Diseases by Taxonomy, 3rd edition, Pearson Benjamin Cummings
Learning Objectives
You should be able to:
1. State the mode of transmission for mycoses.
2. Identify the laboratory techniques used to distinguish
pathogenic fungi.
3. Discuss briefly the clinical manifestations of common
systemic fungal infections and its causative agents.
4. Describe pityriasis caused by Malassezia furfur.
5. Identify several emerging fungal pathogens seen
among AIDS patients.
6. Compare and contrast protozoan infections caused by
Giardia, Amoeba, Trypanosoma, Trichomonas,
Plasmodium, and Toxoplasma.
7. Compare and contrast the three most common
roundworm infections of humans.
Mycoses
• Mycology – study of fungi
• Mycoses – fungal infection classified as
superficial, cutaneous, subcutaneous, or
systemic infections
• Generally spread via inhalation, trauma,
or ingestion; also by contact (candida &
pneumocystis)
• Most are dimorphic - below 30˚C
(mycelia composed of hyphae); at 37˚C
(as yeast)
• Diagnosis – sabouraud dextrose agar culture;
KOH preparation; GMS (Gomori methenamine
silver) stain; direct immunofluorescent probes
• Rx – antifungal agents (amphotericin B; toxic);
alternative drugs (ketoconazole, itraconazole,
fluconazole)
Common Fungal Diseases
A. Pathogenic systemic fungi
• Blastomycosis – Blastomyces dermatitidis
• Coccidiomycosis – Coccidioides immitis
• Histoplasmosis – Histoplasma capsulatum
B. Opportunistic systemic fungi
• Aspergillosis – Aspergillus fumigatus,
Aspergullus flavus
• Candidiasis – Candida albicans
• Cryptococcosis – Cryptococcus neoformans
• Pneumocystosis – Pneumocystis carinii
C. Superficial, Cutaneous, and Subcutaneous
fungi – by contact or environmental exposure
Blastomycosis
• Blastomycosis dermatitidis
• Prevalent in Mississippi –
Ohio river basin
• 9X more common in male
• Inhaled dust →lung →blood
→skin and bones
• Pulmonary blastomycosis –
most common
• Granuloma (cutaneous
blastomycosis 60-70%)
• Osteoarticular blastomycosis
(30%)
• Spores convert to yeast forms
Coccidioidomycosis
• Valley fever (San Joaquin Valley
Fever)
• Coccidioides immitis
• Prevalent in Southwestern US
• Inhaled in lungs→ spores
germinate into spherule
(parasitic form) →enlarges and
generate more spores
• 60% - no or mild symptoms
• Fever, chest pain, rash, and
pneumonia
• Subcutaneous lesion (granular
material)
• Dx – identification of spherules
in KOH; culture
Histoplasmosis
• Most common fungal pathogen
in humans
• Histoplasma capsulatum
• Prevalent in Ohio- Mississippi
valley
• Inhaled from bird droppings
• usually asymptomatic and
resolve (95%)
• Chronic pulmonary
histoplasmosis, chronic
cutaneous histoplasmosis,
systemic or ocular
histoplasmosis (5%)
- Granuloma in lung
(resembles TB)
* Spiny spores of H. capsulatum
Aspergillosis
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•
•
•
Aspergillus flavus
Inhalation of spores
aflatoxin→ liver CA
Cause pulmonary
diseases (noninvasive;
manifest as allergy or
asthma)
• In immunocompromised
(IV drugs users, AIDS)
- non-pulmonary (cutaneous)
- systemic (often fatal)
• Raised red papules and necrotic
Candidiasis
• Candida albicans
• Infection from superficial to
systemic
- superficial→ deep invasion (low
immunity)→ blood stream
(catheter, surgery, etc.)
- oral thrush
- perianal in infants
• Dx - clusters of yeast and
pseudohyphae
• Rx – antifungal drugs; reestablish
normal flora
Cryptococosis
• Crptococcus neoformans
• Worldwide
• Affects
immunocompromised
• Capsule; india ink as
negative stain
• From inhaled spores or birds
droppings
• Lung infection (self-limiting
to chronic pneumonia)
• Meningitis (most common
clinical form)
• Rx – amphotericin B
Pneumocystosis
• Pneumocystis jiroveci (P.
carinii)
• Common opportunistic in
AIDS
• Inhalation of droplets
• Form cysts in lungs
(pneumonia)
• Fever, dyspnea, hypoxia,
sometimes cough
• Dx - shadow on Chest X ray
• Rx – trimethoprim and
Sulfanilamide
Malassezia Infections
• Malassezia furfur – normal
inhabitant of skin; various
superficial infections
• Pityriasis (tinea versicolor) –
depigmentation or
hyperpigmentation
• Folliculitis, seborrheic dermatitis,
and dandruffs
• Dx – UV illumination (pale
green); KOH (budding yeast and
hyphae)
• Rx – ketoconazole shampoos or
topical zinc pyrithione, selenium
sulfide, or propylene glycol
Protozoa
• Amoebiasis – Entamoeba histolytica
• Trypanosomiasis – African sleeping
sickness (T. gambiense, T. brucei);
Chaga ‘s disease (T. cruzi)
• Giardiasis – Giardia lamblia
• Trichomoniasis – Trichomonas vaginalis
• Malaria – Plasmodium vivax, P.
falciparum, P. malariae
• Toxoplasmosis – Toxoplasma gondii
Amoebiasis
• Entamoeba histolytica – phagocytic;
cysts with 4 nuclei; trophozoites with
pseudopodia
• MOT - Fecal contamination containing
cysts; travellers, refugees, immigrants
• Mild to severe diarrhea; amebic
dysentery (bloody diarrhea)
• Form abscess in liver, spleen, lung,
kidney, meninges, or brain.
• Dx – identification of cyst or trophozoites
in stool or intestinal biopsy
• Rx – antiamoebic drugs (metronidazole)
• Prev – discontinue use of human waste
as fertilizer; effective water Rx; good
personal hygiene
Trypanosomiasis
• Flagellates
• African sleeping sickness –
T. gambiense, T. rhodesiense,
T. brucei
• MOT – bite from tsetse fly
(trypanosoma reproduce in gut and
migrate to salivary gland) → to lymph
•
•
•
•
•
and blood (parasitemia)
Acute febrile attack
Episodic fever with lymphadenitis
DIC
Progressive brain dysfunction; fatal
Rx – early Rx is effective
* Glossina
Chaga’s Disease
• Trypanosoma cruzi
• MOT – bite from blood sucking kissing bug (kiss
people on lips while asleep)→ lymph and blood →
multiplies in tissues (pseudocysts)
• Fever, lymphadenitis
• Acute form – unnoticed
• Chronic form – up to 20 yrs. Later; myocarditis,
meningitis, chronic heart disease (5% mortality)
Giardiasis
• Giardia intestinalis (G. lamblia) –
with many flagella; looks like a
“head with face”
• One of most common waterborne gastroenteritis in US
• Cysts form in duodenum, shed in
feces→ mild indigestion for
days/weeks → diarrhea →
chronic giardiasis (bloating,
nausea, vomiting, malabsorption,
weight loss)
• Rx – metronidazole
Trichomoniasis
• Trichomonas vaginalis –
3-4 flagella; trophozoites, no cyst form
• Common sexually transmitted
parasitic infection
• Both sexes – burning, itching sensation of genitalia,
some discharge
• Vaginitis in women
• Urethritis or cystitis in men, but often asymptomatic
(ping-pong disease)
• Dx – identify trophozoites in vaginal and urethral
secretions
• Rx – metronidazole
• Prev – abstinence, monogamy, condoms
Toxoplasmosis
• Toxplasma gondii
• Wild/ domestic mammals and birds
– major reservoirs
• Cat – definitive hosts
(protozoan reproduce sexually)
• Human infected by ingesting
undercooked meat with parasites;
ingestion or inhalation with
contaminated soil; can cross
placental to fetus
• Fever to pneumonia, CNS damage, blindness
• Pregnant women – stillbirth, jaundice, pneumonia, myocarditis,
encephalitis; death
• Lymphadenitis in healthy person
• Prev – thoroughly cooking meat; avoid contact with contaminated soil
Malaria
• Plasmodium vivax (clinical relapse),
P. falciparum (most deadly), P. malariae
• Vector – Anopheles mosquitoes
• Life cycle has 3 stages
1. exoerythrocytic – sporozoites (infective stage to human) travel to
liver, then rupture to release merozoites (pathogenic to human)
2. erythrocytic – merozoites infect RBC; become trophozoites and
undergo schizogony to produce merozoites, some develop to
gametocytes
3. sporogonic – mosquitoe ingest gametocytes (infective stage to
mosquito), develop into gametes, become oocyst, divides into
sporozoites, completing the cycle.
• RBC lyse to release merozoites and waste → shaking chills, high
fever (104˚F), sweating
• Rx – chloroquine, pyrimethamine with sulfadoxine
• Prev – prophylactic quinine for travel to endemic places; vector
control; personal protection
Helminthic parasites (Worms)
1. Cestodes (tapeworms)
a) Taenia saginata (beef
tapeworm)
b) Taenia solium (pork tapeworm)
2. Trematodes (flukes)
a) blood flukes – Schistosoma
(schistosomiasis)
b) liver flukes – Fasciola (liver
atrophy and cirrhosis)
3. Nematodes (round worms)
a) Ascaris lumbricoides
– ascariasis (worldwide;
longest/largest)
b) Enterobius vermicularis
- pinworm (most common in US)
c) Wuchereria bancrofti
- filaria (South America, Caribbean,
Trophics)
Filariasis
• Wuchereria bancrofti –
threadlike (filarial) nematode
• Infect the lymphatic system
and subcutaneous tissues
• Transmitted by
mosquitoes (culex, aedes, and
anopheles)- ingest microfilariae
from infected host, then develop into larvae in gut and
migrate to salivary glands, passed to human and develops
into adults
• Asymptomatics for yrs.
• Elephantiasis (tissue enlarge and harden)
• Dx – identify microfilariae
or immunoassays
• Rx – diethylcarbamazine citrate
• Prev – avoidance of mosquitoes
Homework
1. Identify the fungal agent and most common clinical
manifestation/s (lesion/s) of the following: candidiasis,
aspergillosis, cryptococcosis, blastomycosis,
coccidiodomycosis, tinea versicolor; and histoplasmosis.
2. What fungal infection is commonly associated with AIDS
(HIV)?
3. Compare and contrast amoebiasis and giardiasis.
4. Identify the risk factors and preventative measures for
Trichomonas vaginalis infection.
5. Describes the types of helminthic worms.
6. Discuss African sleeping sickness and Chaga’s disease.
7. Discuss malarial infection as to manner of transmission,
clinical manifestations, and preventions.