Midterm III (Leiel) Different order Flashcards Preview

Y Microbiology - MT > Midterm III (Leiel) Different order > Flashcards

Flashcards in Midterm III (Leiel) Different order Deck (31):

What causes hydratidosis

Caused by the larval stage of Echinococcus granulosus


Classification of fungal diseases

Fungal allergies - "sick building syndrome", generally occur in individuals with other allergies

Mycotoxicosis - poisoning from exposure to mycotoxins, may result from ingestion of fungal-contaminated foods (generally an animal problem) or mushrooms

Superficial mycosis - infections limited to the outermost layers of the skin and hair

Cutaneous mycosis - infections that extend deeper into the epidermis, as well as invasive hair and nail diseases

Subcutaneous mycosis - infections involving the dermis, subcutaneous tissues, muscle and fascia

Systemic mycosis - infections that originate primarily in the lung but may spread to many organs

Opportunistic mycosis - infections in immunocompromised patients (e.g. candida in HIV)


Spreading of cryptosporidiosis

  • Cryptosporidium affects both animals and humans
  • Causes diarrhea upon ingestion of contaminated water
  • Resistant to chlorination (source of infection- swimming pools)
  • Ingested as round oocyte → contains 4 motile sporozoites (stage in the lifecycle of sporozoan organisms)


  • Transmitted oral-fecally as oocyte
  • Attached to the intestinal epithelial cells (mostly the jejunum)
  • Sexual forms develop to produce more oocytes → seen in the stool


List of the Cestodes and what are the intermediate hosts

  • Taenia saginata - cattle
  • Taenia solium - pig
  • Echinococcus granulosus - dog
  • Echinococcus multilocularis - rodents or other small mammals
  • Hymenolepis nana - arthropod
  • Diphyllobotrium latum - fish


Life cycle and disease of taenia solium

Life cycle:

  • In the muscle "cysticercus" ("bladder worm") of the infected animal (pig) →
  • human infected by eating the meat (4) →
  • small intestine larva maturation →
  • mature worm →
  • proglottids break off →
  • pass out with feces →
  • pig eats vegetation contaminated by eggs or gravid proglottids →
  • oncospheres hatch, penetrate intestinal wall, and circulate to musculature →
  • “cysticercus”

Taeniasis due to T. solium is usually characterized by mild and non-specific signs and symptoms; 6-8 weeks after ingestion of the cysticerci, abdominal pain, nausea, diarrhoea or constipation might arise and last until the tapeworm dies following treatment (otherwise it may live many years).


Diagnosis of malaria

RBC smears to reveal the different stages of the lifecycle (thin/thick blood film examination)

Fluorescent Ab to identify the species


Acanthamoeba and Naegleria source of infection and diseases

  • Both Naegleria and Acanthamoeba species are free-living amoeba
  • They live in fresh water and soil
  • They are resistant to chlorination
  • Infection occurs in summertime when people bath in freshwater lakes and swimming pools
  • Enters through the nasal mucosa → cribriform plate → meningioencephalitis


  • Sudden fulminant deadly infection in immunocompetent hosts
  • Severe infection that presents as fever, headache, stiff neck, nausea, vomiting


  • Granulomatous inection, usually in immunocompromised hosts
  • Can infect the cornea- amoebic keratitis (via contact lens) → blindness
  • Corneal lesions are painful and present as ulcers
  • Infection may be by wind-borne cysts, or from contact lenses
  • Solutions used to store, or wash, lenses can be contaminated


Define accidental intermediate host, examples


  • accidental host: a host in which the parasite cannot complete its life cycle.
  • IH: parasites either do not reproduce or do so asexually, but the parasite always develops to a new stage in this type of host.
  • e.g: humans in echinococcus granulosus, echinococcus multilocularis


Spread of Toxoplasma gondii

  • Ingestion of cyst in undercooked meat
  • Food contaminated with household cat feces
  • Transplacental and transfusion infections


Classification of fungi by morphology

  1. Mould: produces multicellular filamentous colonies which contains hyphae and mycelium. E.g aspergillus.
  2. Yeast: unicellular growth pattern that can be spherical\ellipsoidal. e.g: candida, cryptococcous
  3. Dimorphic: can grow either as yeast or as mould depending on temp. in body temp – yeast, cold temp –mould. E.g: Histoplasma capsulatum, blastomyces dermatitidis


Diagnosis of schistosomes

Identification of eggs in urinary sediment

Viable eggs contain a motile miracidium (a free-swimming ciliated larval stage in which a parasitic fluke passes from the egg to its first host, typically a snail)

Eggs can occasionally be found in feces



Species causing filariasis

  • Wuchereria bancrofti
  • Brugia malayi


Diagnosis of fungal disease

Staining properties:

  • False Gram positive
  • Can be stained by
    • methenamine-silver
    • periodic acid-Schiff stain (PAS)
    • methylene blue


  • Scrapings from the skin and the nails
  • Hairs plucked from involved areas
  • Microsporum-infected hairs fluorescent under Wood's light (365nm) in a darkened room


  • Wet mount
  • Simple staining (e.g. methylene blue)
  • Before native examination- 30% KOH for keratolysis (for keratinized tissues)

Biochemical reactions:

  • Sugar fermentation
  • Sugar assimilation test
  • Nitrate assimilation test

Serology: ELISA, latex agglutionation


Trichomonas vaginalis spreading and treatment

Transmitted by vaginal sexual contact; can survive for many hours at room temperature if kept damp, so the theoretical possibility of non-venereal transmission exists 

Occurs in female vagina and male urethra

Treatment: metronidazole, tinidazole


Define proglottid, scolex


  • The body is composed of successive segments called proglottids. The sum of the proglottids is called a strobila, which is thin, and resembles a strip of tape.
  • Besides the scolex, the rest of the body forms the strobila and consists of a chain of flattened proglottids
  • Gravid proglottids are lost from the end of the worm and are replaced by other that have matured as they pass down the strobila.
  • Each proglottid possesses a complete set of hermaphroditic sex organs and marginal genital openings
  • Eggs accumulate in the uterus of gravid proglottids and only enter the fecal stream when the proglottids are disrupted


  • The anterior end of a tapeworm, bearing suckers and hooks for attachment
  • The tapeworms maintain anchorage to the host small-gut mucosa by means of the scolex.
  • The structure is bearing a circlet of 4 suckers and usually a central rostellum with one or more circlets of minute hooks.


Factors that affect systemic mycosis.

  1. Diseases that causing immunosuppression – tumors, AIDS, steroid therapy, DM.
  2. Trauma – burns and stabbing injuries.
  3. Immunosuppresion therapy – irradiation, corticosteroids, broad spectrum antibiotics.
  4. Nosocomial infections
  5. Voluntarily risk: alcoholism, drug abuse, microbiologists.


Cultivation of fungi


  • The identification of dermatophyte species requires culture
  • Specimens are inoculated onto inhibitory mold agar or Sabouraud's agar plates containing cycloheximide (to prevent growth of environmental molds)  and chloramphenicol (to inhibit the growth of bacteria)

Species are identified on the basis of:

  • Colony morphology (growth rate, surface texture, and any pigmentation)
  • Microscopic morphology (macroconidia, microconidia)
  • Nutritional requirements

Sabouraud's agar:

  • Glycose, peptone, acidic pH
  • Morphologic characteristics of fungi are used for identification (room temp. and body temp. to see dimorphic nature)
  • Antibiotic (gentamycin, chloramphenicol) - inhibition of bacteria
  • Long time incubation (for negative result) - about 14 days


Classification of the protozoons

Traditionally classified on the basis of locomotion:

  • Flagellates (move by flagella)
  • Amoeboids (move by false feet)
  • Ciliates (move by cilia)
  • Sporozoas (non-motile)


Geohelminths  (nematodes)

Ascaris lumbricoides

Strongyloides stercoralis

Necatoe americanus

Trichuris trichiura


The vector of Chagas' disease and spreading way

Chagas' disease is transmitted by the American Trypanosome: Trypanosoma cruzi.

Hosted by rodents, opossums and armadillos → transmitted by reduviid bug (the kissing bug)

When the bug eats, it also defecates. Scratching the site of the bite causes the trypomastigotes to enter the host through the wound.

T.cruzi invades macrophages, lymph nodes and via the blood.


Host of D. latum and disease

2 intermediate hosts: freshwater crustaceans and freshwater fish

Most of D. latum infections are asymptomatic. Occasionally, people complain of epigastric pain, abdominal cramping, nausea, vomiting, and weight loss.

Low serum level of vitamin B12 because of the competition the worm and the host for dietary vitamin B12. 


Life cycle of malaria

  • Plasmodia undergoes sexual divisions in the anopheles mosquito

In the human body:

  • The mosquito releases a motile, spindle-shaped sporozoites into the blood stream
  • It invades the liver and starts the pre-erythrocyte cycle
  • The sporozoite forms a ball → trophozoite
  • Trophozoite undergoes nuclear division → 1000s of new nuclei are formed → a big mass of them is called schizont
  • Formation of membrane around the nuclei → merozoites → burst into the liver and blood stream → some will infect other liver cells (as the sporozoites did initially)→ a new cycle is starting → exo-erythrocyte cycle
  • Those merozoites that enter the blood stream, enter the RBC → starting the erythrocyte cycle
  • The merozoites form trophozoites- a ring-like shape where the nuclear material looks like a "diamond on the ring"
  • Nuclear division occurs again, forming schizont →merozoite → lysis of the RBC and release of the merozoites to the circulation
  • The last step initiate immune response- resulting in fever, chills and sweats
  • The merozoites continue the cycle
  • Some of them will change to female and male gametocytes → these are taken back by the mosquito
  • Plasmodium vivax & plasmodium ovale produce dormant form in the liver, called hypnozoites→ grows years after the first infection

In the mosquito:

  • The sexual cycle = sporogony
  • The gametocytes are sucked into the stomach → female and male gametocytes fuse
  • The DNA is mixed → oocyte is formed
  • Oocyte divides to spindle-shaped sporozoites →disseminate to the blood stream → reach the salivary glands → injected into humans, starting the human cycle


Toxocara canis

Life cycle:

  • Final host: cat, dog → gravid female vacates the eggs in the gut → with feces, the eggs get into the soil → maturation in the soil → larvae in humans → granulomatous infection (liver, brain)
  • The infection is acquired from ingestion of embryonated eggs released in the soil
  • After ingestion, the larvae begin somatic migration to the lungs, liver, eye, CNS


  • The clinical presentation depends on the number of larvae ingested and the degree of allergic response
  • 2 major syndromes have been identified:
    • Visceral Larva Migrans (VLM)- characterized by fever, malaise, leukocytosis with hypereosinophilia, hepatomegaly, cough, myalgias, high titers of isohaemagglutinins. Other manifestations: myocarditis, encephalitis and pneumonia
    • Ocular Larva Migrans (OLM)- characterized by retinal granulomas and uveitis → blindness


  • Western-blot analysis
  • Detection of antibodies by ELISA

Therapy: tiabendazole


Subcutaneous mycosis

  • Infections involving the dermis, subcutaneous tissues, muscle and fascia
  • Present in soil or on vegetation
  • Traumatic inoculation by contaminated material
  • In rare cases, they become systemic and produce life-threatening disease

Sporothrix schenckii:

  • A thermally dimorphic fungus that lives on vegetation: grass, trees, moss, rose bushes, and other horticultural plants
  • Initial lesion is usually on the extremities
  • Initial lesion develops as a granulomatous nodule that may progress to form necrotic lesion
  • Dissemination: bones, eyes, lungs
  • Treatment: local treatment- potassium iodide, itraconazole, fluconazole, amphotericin B


  • Chronic, localized infection of the skin and subcutaneous tissue of the limbs
  • Characterized by raised, crusted lesions
  • Slow development
  • Fungi are introduced to the skin by trauma
  • Over months, the primary lesion becomes verrucous and wart-like
  • Cauliflower-like nodules cover the area
  • Rarely elephantiasis may result from secondary infection and fibrosis of lymph channels


  • Mycetoma: local swelling and interconnecting. Containing granules which are microcolonies
  • Eumycetoma: mycetoma caused by a fungus, develop after traumatic inoculation with soil
  • Suppuration, abscess formation, granulomas
  • May spread to muscle and bone
  • Treatment: ketoconazole, itraconazole


Fasciola hepatica – intermediate and final host and disease

Intermediate host - snail

Final host - cattle, sheep

Symptoms vary depending on if the disease is chronic or acute.

  • During the acute phase the immature worms begin penetrating the gut, causing symptoms of fever, nausea, swollen liver, skin rashes and extreme abdominal pain.
  • The chronic phase occurs when the worms mature in the bile duct, and can cause symptoms of intermittent pain, jaundice and anemia.

The disease is called fascioloasis.


What are the risk factors in fungal diseases

  • Diseases causing immunosuppression: tumors, AIDS, steroid therapy, diabetes mellitus
  • Trauma: burn wounds- molds, stabbing injuries- subcutaneous mycosis
  • Iatrogenic mycosis: during the immunosuppression therapy (irradiation, corticosteroid therapy, administration of broad spectrum antibiotics, cytostatic therapy)
  • Nosocomial infections: fungi associated to plastic surfaces (catheters)
  • "voluntary risks": alcoholism, drug abusers, microbiologists, mycologists


Protozoon transmitted by snail


Fasciola hepatica

Paragonimus westermani*


Diseases caused by Entamoeba histolytica

Amoebic dysentery and liver abscesses

Mostly asymptomatic

Can invade the intestinal mucosa:

  • Abdominal pain, mucous and bloody diarrhea
  • If it penetrates the portal circulation- liver abscesses
  • Reaching the diaphragm- causing pulmonary abscesses → death


Diagnosis of Giardia lamblia

Examine the stool for cyst or trophozoite (a duodenal tube can also be used)

String test:

  • For this test, you swallow a gelatin capsule attached to a long string. The end of the string remains outside the mouth and is taped to your cheek. The capsule dissolves in the stomach and the string passes into the upper part of the small intestine (duodenum).

ELISA stool antigen


Which protozoon cannot form cysts

Trichomona vaginalis - no cysts, only trophozoite form


Spreading and causative agents of sleeping sickness

Causative agents: Trypanosoma brucei rhodesiense and gambiense


  • Congenital, blood-borne, and mechanical transmission have been reported
  • The main mode of transmission is through the bite of infected tsetse fly
  • During the blood meal, the tsetse fly takes up trypanosomes into its mid gut where they multiply
  • After about 2 weeks, they migrate to the salivary glands as epimastigotes
  • They finally develop into infective metacyclic forms