Pathogenic Fungi

Question 1

Fungi

Answer 1

– Fungi can be single-celled yeasts or hyphae-forming
mold.
▪ hyphae eventually intertwine to form visible
masses called mycelia.

Question 2

Dimorphic

Answer 2

Some pathogenic fungi are dimorphic, meaning they
can be either molds or yeasts (Candida albicans for
example)
▪ typically dictated by environmental factors, such
as temperature and moisture level.

Question 3

No. of fungal species that cause disease

Answer 3

50

Question 4

Mechanisms in which fungi can cause disease

Answer 4

– inappropriate immune responses
▪ produce potent allergens, triggering asthma attacks or other hypersensitivity reactions e.g. aspergillus, cladosporium and penicillium.
– mycotoxins (e.g.. Aflatoxins, Ergot Alkaloids made by Claviceps sp.)
– infections (mycoses)
▪ superficial
▪ subcutaneous
▪ systemic

Question 5

Superficial mycoses

Answer 5

Caused by dermatophytes
▪ Fungi that colonize the hair, skin, or nails and infect only the
surface layers

Question 6

E.Superficial mycoses

Answer 6

Trichophyton cause infections of the feet (athlete’s
foot) and other moist skin surfaces and are quite common

Question 7

Subcutaneous mycoses

Answer 7

Fungi colonize deeper layers of skin
-Tend to be more serious than superficial fungal infections

Question 8

E. Subcutaneous

Answer 8

▪ Sporothrix
▪ Fonsecaea
▪ Cladosporium

Question 9

Systemic mycoses

Answer 9

Fungal growth in internal organs of the body

Question 10

E. Systemic mycoses

Answer 10

histoplasmosis caused by Histoplasma capsulatum
cryptococcosis caused by Cryptococcus neoformans

Question 11

Pre-desposing conditions for fungal infections

Answer 11

Systemic:
-Impaired immune system (AIDS) or taking immunosuppressive drugs
All fungal infections:
-Pregnancy and very young and old individuals as they all have a weakened immune response
-Antibiotis- Disrupt the normal microbiota which leads to fungal overgrowth

Question 12

E. antibiotics causing fungal infection

Answer 12

Mucosal
vaginal yeast (Candida) infections are common with
antibiotic use.

Question 13

Fungal infections of alveoli

Answer 13

-histoplasmosis, H. capsulatum microconidia
found in soil, and guano (bird or bat droppings) are inhaled and
reach the alveoli.
-In alveoli, they are digested by macrophages and survive inside the phagolysosome
-They are thermally dimorphic and transform into yeat that then grows and multiplies within the phagolysosome
-The macrophages then travel in lymph and spread disease to different organs and this spread is associated with immune disfunction

Question 14

Fungal infection that causes pneumonia

Answer 14

Cryptococcus neoformans
-Causes pneumonia or meningitis or encephalitis in immunocompromised and AIDS patients

Question 15

Entamoeba histolytica description

Answer 15

-a pathogenic protist transmitted to humans primarily through contaminated water and sometimes food
-anaerboic and produces resistant cysts
-causes thousands of deaths
-responsible for diarrhea and dysentry or could be asymptomatic

Question 16

Entamoeba histolytica disease effects

Answer 16

▪ intestinal inflammation, fever, and the passage of intestinal blood and mucus, which often leads to anemia.
▪ It may become invasive; cells can invade the liver and occasionally the lungs and brain
▪ can be treated with amoebicidal drugs (e.g
nitroimidazole

Question 17

Entamoeba histolytica infection mechanism

Answer 17

• Infection begins by ingestion of cysts
  -These germinate in large intestine into active trophozites which multiplly by division within intestinal crypts
  -Many conditions can alter dynamic and lead to virulence:
• Trophoziites migrate through intestinal mucus and bind to epithelial cells and release proteases, lipases, and pore-forming cytolysins which kill epithelial cells
  *Parasite engulfs dead cells and releases nutrients which results in intestinal ulcers and bloody diarrhoea
  *Invasive strains migrate through ulcerated intestinal tissue into blood where the trophozites invade lung, skin, liver or brain

Question 18

Asymptomatic carriers of E.histolytica vs individuals with dysentry

Answer 18

Asymptomatic shed high numbers of cysts while dysnety individuals dont

Question 19

Naegleria fowleri

Answer 19

Known as brain eating amoeba
– A free-living amoeba found in soil and water runoff; exists in a trophozoite, flagellated and cyst form.
– Infections usually result from swimming in warm, soil contaminated natural water sources (e.g., hot springs or
lakes)
-Causes primary amebic meningoenceohalitis

Question 20

how is primary amebic meningoencephalitis caused

Answer 20

– Enters the human body through the nose and travels along olfactory axons to the brain and feeds on astrocytes and neurons causing extensive hemorrhage and brain damage.
-drug treatment is effective only with early diagnosis

Question 21

Giardia intestinalis

Answer 21

– flagellated anaerobic parasite
– produces highly resistant cysts (resistant to chlorination)
▪ cause of giardiasis, a common waterborne disease

Question 22

Giardiasis symptoms + infectious mechanism

Answer 22

– explosive, foul-smelling diarrhea, intestinal
cramps, nausea, weight loss, and malaise
– many individuals exhibit no symptoms and can act as carriers
- Does not lyse cells but feeds on mucus and prevents nutrient absorbtion in small intestine and damage to intestinal microvilli

Question 23

Sexually transmitted infections (STIs)

Answer 23

– Also called sexually transmitted diseases (STDs)
– Caused by a variety of bacteria, viruses, protists, and even fungi
– Pathogens are generally only found in body fluids from the genitourinary tract that are exchanged during sexual activity

Question 24

Gonorrhea and syphillis trend

Answer 24

Upward trend for both disease and immergence of multi drug resistant N.gonorrhea strains

Question 25

• Gonorrhea + mechanism of infection

Answer 25

– caused by Neisseria gonorrhoeae
– In 2016, the WHO estimated that there were 86.9 among 100? adults 15–49 years of age
- N. Gonorrhoeae is a fastidious organism that only grows well within the host, using a variety of highly evolved mechanisms for attachment, immune evasion and iron uptake

Question 26

Gonorrhea symptoms in females

Answer 26

– symptoms in females
▪ characterized by a mild vaginitis that often goes unnoticed
▪ untreated gonorrhea can lead to pelvic inflammatory disease (an infection of the fallopian tubes, uterus, ovaries, which can lead to chronic pain, infertility, ectopic pregnancies and other complications

Question 27

Gonorrhea – symptoms in males

Answer 27

▪ characterized by a painful infection of the urethral canal

Question 28

Gonorrhea pathogenesis

Answer 28

-caused by the release of bacterial cell wall
fragments which are toxic to epithelial cells and activate immune cells.
-Immune activation causes tissue damage and scarring.

Question 29

Syphilis

Answer 29

– caused by Treponema pallidum
– often transmitted at the same time as gonorrhea
– can be transmitted to the fetus during pregnancy (congenital syphilis)
– three stages: primary, secondary, and tertiary
– penicillin highly effective for primary and secondary stages.
– Before the advent of antibiotics, in the 1940’s syphilis was incurable.

Question 30

Past Syphillis treatment

Answer 30

Paul Ehrlich and Sahachiro Hata discovered arsenic based compound called Arsephenamine which was marketed as Salvarsan
- first example of drug with a specific therepeutic effect to be created based off theoretical considerations
- Most widely prescribed drug and most effective in treating syphillis until penicillin was developed in 1940

Question 31

Primary syphilis

Answer 31

-appears 10 to 90 days after exposure to the infection
-comprises a painless, indurated ulcer (chancre) at the site of inoculation with
the T. pallidum.
-These lesions resolve without treatment in 3-6 weeks.
-Regional lymph node swelling is common and consists of rubbery lymph nodes.

Question 32

Secondary syphilis

Answer 32

-appears 2 to 8 weeks after the disappearance of the chancre
-has multiple systemic manifestations including rashes and flu-like symptoms.
- Individuals are highly contagious at this point.
-Untreated primary or secondary syphilis is followed by an early latent phase
(one year or less later on) or late latent phase (over one year) and is characterized by positive serologic tests but negative clinical manifestations.

Question 33

Tertiary syphilis

Answer 33

-late symptomatic syphilis that can manifest months or years after the initial infection
-cardiovascular syphilis, neurosyphilis, or
gummatous syphilis (infiltration of any organ and its subsequent destruction).

Question 34

Chlamydia trachomatis

Answer 34

-Total infection significantly outnumber gonorrhea making it most prevelant STI in world
-Often asymptomatic but causes pelvic inflammatory syndrome in women
-Obligate intracellular parasites that form elementary bodies and reticulate bodies

Question 35

Types of chlamydia infections

Answer 35

– nongonococcal urethritis (NGU)
– lymphogranuloma venereum (LGV)

Question 36

Trichomonas vaginalis

Answer 36

-Eu parasite
– flagellated anaerobic parasite, which feeds on leukocytes and bacteria within the vagina
– has hydrogenosomes in place of mitochondria
– transmitted person-to-person by sexual intercourse
– can survive on moist surfaces like and can be transmitted by toilet seats, sauna benches and towels
-Infects over 100 million people anually

Question 37

T. Vaginalis in males

Answer 37

– asymptomatic in males, although it can cause prostatitis and urethritis

Question 38

T.Vaginalis in females

Answer 38

– vaginal discharge, itching, and burning in women

Question 39

T. Vaginalis treatment

Answer 39

antiprotozoal drug metronidazole used in treatment

Question 40

Pathogenicity of T.vaginalis

Answer 40

-Virulence factors that facilitate adhesion to vaginal epithelial cells: AP65, AP51, AP33 and AP23
-Cysteine proteases facilitate both adhesion and damage ECM which leads to inflammation, intense itching and thick white or green discharge
-Inflammation can increase susceptibility to HIV-1 infection
-Also effects pregnancy by causing complications like preterm delivery, low birth weight and increased feotal mortality