Basic biology of pathogens Flashcards
(82 cards)
1
Q
In what environment will you find Blastomyces?
A
Moist soil
Decomposing wood + leaves
2
Q
In what environment will you find Coccidioides?
A
Dust
Dry soil.
3
Q
In what environment will you find Histoplasma?
A
Soil with bird/bat droppings
4
Q
Where do body lice live?
A
In clothes
(They just come to your body to feed, then go back and hide in seams)
5
Q
Describe the microscopic morphology of: Blastomyces
A
Mould phase: (25-30C)
- Lollipops + double thick “broad based” buds.
- Septate hyaline hyphae with unbranched short or long conidiophores @ 90degrees
- “Lollipop” (round/pear) unicellular conidia at apex, emerging directly from the hyphae.
Yeast phase: (37C in tissue or on enriched agar)
- Thick-walled.
- Broad-based budding.
- Often see pairs since buds remain attached until same size as parent cell.
6
Q
Describe the microscopic morphology of: Coccidioides
A
Mould form: (in environment)
- Septate, branched hyphae.
- Thick-walled, barrel-shaped arthroconidia that alternate with empty (“disjunctor”) cells.
Yeast form: (in tissues/body fluids)
- Large, round, thick-walled spherules which contain endospores
7
Q
Describe the microscopic morphology of: Histoplasma
A
Mould form: (environment)
Young:
- Septate hyphae bearing round/pear smooth microconidia on short branches or right on the sides of the hyphae.
Mature (after several weeks):
- Large, thick-walled, round macroconidia: tuberculate, knobby, with short cylindrical projections.
Yeast form: (tissues, culture 35C)
- Narrow-based budding yeast.
- Thick/double wall appearance.
8
Q
How many cells make up a single protozoan?
A
One
9
Q
How does Blastomyces exposure lead to infection & disease?
A
- Spores (from mould form) are inhaled from damp soil with decomposing matter.
(OR may be inoculated into the skin). - Warmer temperature -> changes into yeast form.
- Yeast remains colonized in lungs.
- Yeast may disseminate in the bloodstream to other parts of the body.
10
Q
How does Clostridium tetani cause disease?
A
Bacteria grow locally, releases tetanospasmin toxin
11
Q
How does Coccidioides exposure lead to infection & disease?
A
- Spores (from the mould form) are inhaled.
- Temperature change -> change to spherules.
- Spherules divide (internally) until they are filled with endospores.
- Spherule ruptures ->
- releases endospores ->
- disseminate into the surrounding tissue.
- Endospores develop into new spherules + repeat this cycle.
12
Q
What are the virulence factors for Enterococcus spp.?
A
Few:
- adhesins
- cytolysins
- proteases
- (antibiotic resistance)
But very susceptible to phagocytosis
13
Q
Virulence factors of S. pyogenes?
A
M protein: a virulence determinant!
- adherance to host cells
- inhibits phagocytosis
- antigenic, but mimics human tissues, so immune response can cross react with human tissues, causing rheumatic fever, rheumatic heart disease, glomerulonephritis.
Capsule:
- inhibits phagocytosis
- made from hyaluronic acid
- indistinguishable from mammalian hyaluronic acid
- a poor immunogen
Fimbriae/pili, Lipoteichoic acid, F protein :
- for attachment to host cells
- fibrils support M protein, other proteins
14
Q
Virulence factors of Streptococcus agalactiae?
A
Capsule = major virulence factor
- inhibits phagocytosis
15
Q
How does Histoplasma exposure lead to infection & disease?
A
- Spores (from the mould form) are inhaled.
- Warmer temperature ->yeast form.
- Yeast are phagocytosed by immune cells
- ->regional LNs.
- Yeast survive inside the immune cells and travel in the blood to other parts of the body.
16
Q
Describe the pathophysiology of LTBI activation ->active pulmonary TB disease
A
- Granuloma bursts
- Releases bacteria
- Causes hemoptysis
- Bacteria replicate further in the lungs.
17
Q
What are the purposes of protozoan cysts?
A
- To protect them against a harsh/unstable environment (for days/weeks).
- For morphogenesis/nuclear division (i.e. the formation of their structures).
- For transmission to a new host
18
Q
Which protozoa live in human blood/tissues?
A
- Plasmodium
- Leishmania
- Toxoplasma
- Babesia
- Trypanosoma
19
Q
Which are the free-living protozoa?
A
- Acanthamoeba
- Balamuthia
- Naegleria
20
Q
Which of these intestinal protozoa are pathogenic?
- Entamoeba histolytica
- Entamoeba dispar
- Entamoeba coli
- Entamoeba polecki
- Endolimax nana
- Iodamoeba buetschlii
- Dientamoeba fragilis
A
- Entamoeba histolytica
- Dientamoeba fragilis
21
Q
Which protozoa can live in/infect the human GI tract?
A
- Entamoeba
- Giardia
- Blastocystis
- Neobalantidium
- Microsporidians
- Coccidians
22
Q
Which protozoa live in the human GU tract?
A
- Trichomonas
23
Q
What are the virulence factors of S.pneumoniae?
A
Symptoms mainly from host’s immune response
Virulence factors mostly protect against immune response
-
Polysaccharide capsule:
- prevents phagocytosis
-
secretory IgA protease
- breaks down IgA, so no adhesion of bacteria to mucin
- prevents muco-ciliary clearance
24
Q
Describe the infection process of M.tuberculosis to the establishment of a latent infection.
A
- Transmitted through respiratory droplets –> inhaled into the URT.
- MTB phagocytosed by lung macrophages, but MTB blocks fusion with lysosomes.
- MTB persists + replicates within macrophages.
- Infected macrophages try to kill MTB by producing IFN-gamma (to kill intracellular pathogens), and recruit backup (other immune cells) to the area wit by releasing other cytokines.
- Incoming cells wall off the area by forming a large granuloma around the site of infection.
- Eventually, cells inside the granuloma die –>caseating lesion.
25
What are some virulence factors for **VGS**?
(very few)
No capsule (no Lancefield antigens)
* **Biofilms**
* adherance to endocardium, tooth enamel
* resist immune defences, antibiotics
26
How is *S. agalactiae* prevented?
* Screening mothers for colonization @ 35-37 weeks pregnancy
* abx given to colonized moms & moms at risk (preterm birth, fever, previous GBS)
* ensures protective levels of antibiotics in neonates
27
What are the member genera of the aerobic actinomycetes?
Suborder Corynebacterineae:
* *Nocardia*
* *Gordonia*
* *Rhodococcus*
* *Tsukamurella*
* *Dietzia*
* *Williamsia*
* *Segniliparus*
* (*Corynebacterium* & *Mycobacterium* are also in this suborder, but not consider aerobic actinomycetes)
Suborder Streptosporangineae:
* *Nocardiopsis*
* *Actinomadura*
28
What are the pathogenic **species** of *Coccidioides* and the differences between them?
***C. immitis***
* California (San Joaquin Valley).
***C. posadasii***
* More widespread.
* Endemic throughout the Americas.
29
What are the pathogenic **species** of *Histoplasma* and the differences between them?
* H. capsulatum* var. ***capsulatum***
* North + South America
* H. capsulatum* var. ***duboisii***
* Africa
30
What are the three kinds of **lice** that infect humans?
1. Pubic ~ (*Pthirus pubis)*.
2. Body ~ (*Pediculus humanus corporis*).
3. Hair/head ~ (*Pediculus humanus capitis*)
31
What are the 5 asexual types of moulds?
1. Hyaline
2. Dematiaceous
3. Dimorphic
4. Mucormycetes
5. Dermatophytes
32
Name 6 blood/tissue endoparasites:
1. Naegleria
2. Toxoplasma
3. Trypanosoma
4. Leishmania
5. Plasmodium
6. Babesia
33
What are the 3 mechanisms of **motility** for **protozoa**?
Give an example genus for each type.
1. **Pseudopods**
E.g. *Entamoeba*
2. **Flagella**
E.g. *Giardia*, *Trichomonas*
3. **Cilia**
E.g. *Neobalantidium*
34
What are some reservoirs of *Aeromonas hydrophila*?
Fresh & salt water
35
How is *Aeromonas hydrophila* transmitted?
Traumatic wounds in fresh water
36
Reservoir of *Bartonella henselae*?
Cats mouths (commensal)
37
How is *Bartonella henselae* transmitted?
* Cat scratches,
* bites,
* feces contact
38
What is the *Babesia* **vector**?
Tick
39
How is *Candida albicans* transmitted?
Direct human-to human contact
40
How is *Entamoeba histolytica* transmitted?
* Fecal-oral
* Oral-anal
41
How is *Francisella tularensis* transmitted?
Animal and tick bites, scratches.
In Tasmania by possums
42
Reservoir for *S. pyogenes*?
Upper Respiratory Tract
43
How is *S. pyogenes* transmitted?
* Respiratory droplets.
* Skin
44
Reservoir of *S. agalactiae*?
* lower GI tract
* GU tract
Commensal in 30% of healthy women of childbearing age
45
How is *Haemophilus influenzae* transmitted?
Respiratory secretions
46
How are *Leishmania tropica, L. braziliensis,* and *L. donovani* transmitted?
* Bite of an infected female **sandfly** (*Phlebotomus*)
* Direct contact with infected lesion
47
How is *Mycobacterium leprae* transmitted?
Nasal secretions
48
Reservoirs for *Mycobacterium marinarum*?
Fresh & salt **water**
49
How is *Mycobacterium marinarum* transmitted?
Trauma in contaminated water, esp. cleaning aquariums
50
Reservoirs of *Mycobacterium ulcerans*?
* koalas
* possums
51
How is *Malassezia furfur* transmitted?
Direct/indirect contact with infected skin
52
How are *Wuchereria bancrofti* & *Brugia malayi* transmitted?
Various ***Anopheles*** species (mosquitoes)
53
How is *Neisseria gonorrhoeae* transmitted?
Sexually transmitted
54
How is *Neisseria meningitidis* transmitted?
Respiratory secretions
55
Reservoirs for *Pasteurella multocida*
* dogs
* cats
* rabbits (normal mouth flora)
56
How is *Pasteurella multocida* transmitted?
Bites or scratches
57
What is the *Plasmodium* **vector**?
Female ***Anopheles*** mosquitoes.
58
Reservoirs of *Rickettsia* & *Orientia*
wild animals (many)
59
How are *Rickettsia* & *Orientia* transmitted?
Arthropods (ticks, mites, lice, fleas)
60
Reservoir for *Streptococcus pneumoniae*?
Upper respiratory tract
61
How is *Sarcoptes scabiei* transmitted?
* Direct contact
* Contact with infected clothing
* Sexual contact
62
How are *Trypansoma brucei gambiense* and *T. brucei rhodesiense* transmitted?
Both are spread by the **tsetse fly**
63
How is *Trypanosoma cruzi* transmitted?
**Reduviids**, so called kissing bugs.
While biting, the bug defecates into the wound allowing transmission of *T. cruzi.*
Spread is aided by scratching the irritated site of the bite.
64
How is *Treponema pallidum* transmitted?
Sexually transmitted
65
How is *M.tuberculosis* transmitted?
**Respiratory droplets** (e.g. coughing, sneezing)
--\>inhaled into the URT.
66
What are the main *Toxoplasma* **vectors**?
* **Cats**
* Pigs
* sheep
* water
* fruit
67
Reservoirs of *Vibrio vulnificus*?
Salt water
68
How is *Vibrio vulnificus* transmitted?
Exposure of wound to seawater
69
Treatment of *C.difficile*?
discontinue implicated antibiotic
multiple abx courses required: spores not killed
Fecal transplant
70
Treatment of Clostridium perfringens
rapid aggressive debridement
high dose penicillin
71
Treatment of Clostridium tetani?
- debridement
- abx: only prevents growth, toxin still active
- tetanus immunoglobulin
72
How is *Enterococcus* spp. treated?
Combo therapy often,
e.g. gentamicin + a penicillin.
73
How is *S. pyogenes* treated?
**Penicillin**
* all strains susceptible
**Erythromycin** if allergic
Prompt treatment of pharyngitis avoids rheumatic fever etc.
74
What is the best **treatment** for body louse infection?
* Improve hygiene
* Get rid of clothes (better than boiling/ironing)
75
What is the best treatment for hair/head **louse** infection?
* Shampoos with permethrin
* Ivermectin
* Mechanical removal with fine-toothed comb
76
How is *Streptococcus pneumoniae* treated?
IV **penicillins**
* (very effective in most cases)
Use cephalosporin if hypersensitive to penicillins
77
What is the first-line treatment for active TB disease?
‘RIPE’:
* Rifampin
* Isoniazid
* Pyrazinamide
* Ethambutol
78
What do the H.influenzae serotypes differ in?
How many are there?
Which are more predominant in North America? {}
Capsule polysaccharides
6 serotypes (a-f)
79
What do the *N.meningitidis* serogroups differ in?
How many are there?
Which are more predominant here in North America?
Capsular types.
13 identified, 6 can cause epidemics (A, B, C, W, X, Y)
B \> C \> others in USA.
Increase in serogroup W in Canada since 2010 due to vaccine escape.
80
How many ***S.pneumoniae* serotypes** exist?
~90 capsular serotypes (#s 1-48 w sub-types)
Vaccines cover the 13-23 most common
81
What do the different ***S.pneumoniae* serotypes** reflect?
Capsular structure.
(No capsule = no disease.)
82
What is the **motile** form of a protozoan called?
A trophozoite
