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Fundamentals of Pathology > W12 Infectious agents > Flashcards

W12 Infectious agents Flashcards

(62 cards)

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1
Q

5 Kingdom system

A 
Protista
Plantae
Animalia
Fungi
Monera
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2
Q

Three Domain System

A

Multiple Kingdoms

Modern DNA analysis

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3
Q

Distinctive biological characteristics

A 
All organisms are cells
	not viruses!
Membranes
Cellular and genome organisation
Single cells
Multiple stages –life cycles
Multicellular - parasites
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4
Q

Prokaryotic

A

No nucleus
No mitochondria
Mainly circular DNA
e.g. bacteria

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5
Q

Eukaryotic

A

Chromosome

Nucleus

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6
Q

Identification essential to understand:

A 
Biology and microbiology 
Evolution and phylogenetics
Pathogenesis of infectious diseases
Life cycles
Accurate diagnosis 
Effective treatment
Public health control of infectious diseases
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7
Q

Criteria: (Systems of Classification of Pathogenic Organisms)

A

Structural and functional and metabolic observations

Molecular and genetic and genome analysis

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8
Q

Sub-species classification:

A

Differentiate pathogenic and non-pathogenic strains

- different disease patterns and clinical outcomes

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9
Q

Linnaean Classification - Hierarchical

A

Domain - Eubacteria

Kingdom - Procaryote

Phylum - Gram +ve

Class - Actinobacteridae

Order - Actinomyceteales

Family - Mycobacteriaceae

Genus - Mycobacterium

Species - Mycobacterium tuberculosis

Strain - Beijing W1

Isolate - Mr Bloggs (12/02/2004)

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10
Q

Visualisation of Microbes - Viruses

A

Can be seen with
electron microscope
x100,000

20 – 300nm

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11
Q

Viruses - size

A

20nm - 300nm

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12
Q

Viruses - structure

A

DNA or RNA genome
- linear, segmented, single or double stranded genome size 9Kb- 300Kb

  • protein nucleocapsid - individual capsomeres Helical, cubic or complex arrangement

No cytoplasm

Enveloped or non-enveloped
- may have components derived from host cell

obligate intracellular organism

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13
Q

Virus life cycle

A 
Recognition
Attachment
Penetration
Fusion
Uncoating
Transcription
Protein synthesis
Replication
Envelopment
Budding and release
Lysis and release
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14
Q

Common viral infections in the UK - Community

A

Upper respiratory tract infection - rhinovirus, influenza, RSV

Gastroenteritis e.g.
Norovirus (SRSV), adenovirus, rotavirus

Rashes e.g. varicella zoster virus (chickenpox), measles

Meningitis e.g. enterovirus

Hepatitis virus e.g. HepB

Human Papilloma virus (HPV) - genital warts

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15
Q

Common viral infections in the UK - Healthcare-associated Infection (Hospital Acquired)

A

Norovirus, flu

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16
Q

adenovirus

A

Non-enveloped

DNA virus

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17
Q

What virus causes muco-cutaneous lesions ?

A

Human Herpes simplex Type 1

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18
Q

Herpes viruses

A

Icosahedral nucleocapsid

Envelope

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19
Q

Influenza virus

e.g. H3N2

A

Surface Haemagglutinin

Enveloped
pleomorphic
Segmented RNA genome
Mutation and recombination
Epidemics and pandemics
Vaccine component H and N
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20
Q

Bacteria - size

A

1/1000th of a mm

0.5 μm to 3 μm

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21
Q

Bacteria - structure

A

Prokaryotic

Haploid DNA, circular genome

no nucleus

usually have rigid cell wall outside cytoplasmic membrane

no mitochondria

Binary fission

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22
Q

Visualisation of Bacteria

A

Unstained at x400

Motile bacteria with flagella move rapidly
Non-motile bacteria also move “on the spot”
i.e. Brownian motion

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23
Q

Gram Staining Bacteria

A

All purple = iodine + crystal violet

G+ purple = alcohol

G- colourless = alcohol

G+ purple = safranin

G- red = safranin

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24
Q

Morphology

A

cocci, rod/bacilli, coccobacilli, spirochetes

  • atypicals e.g. mycoplasma (no cell wall), chlamydia (biphasic)
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25
Gram stain
positive or negative, acid fast, variable
26
Growth requirements
aerobic vs anaerobic
27
Biochemical reactions
e.g. lactose fermenting or non-fermenting
28
Serotype groups
e.g. Streptococcus group A or B; meningococcus B or C
29
Antibiotic resistance
e.g. MSSA or MRSA
30
Other classification criteria for bacteria
rRNA sequencing Genome sequencing MLST or RFLP typing – genetic variation typing methods
31
The presence of beta-hemolytic colonies indicates
indicates the possibility of Streptococcus pyogenes infection
32
Selective Atmosphere - anaerobic culture
eg. Clostridium tetani, Clostridium botulinum, Clostridium difficile GRAM POSITIVE SPORE FORMING ANAEROBIC ROD/BACILLUS SHAPED Clostridium perfringens on Blood agar Grown in ANAEROBIC atmosphere
33
Haemophilus influenzae
Genome = 1.83Million bases (Mb) First genome of a free-living organism sequenced was that of HI - 1995 The genome encodes more than 1700 proteins + 70 RNA molecules Functions of ~ 50% of proteins were determined by comparison w/other species
34
Fungi - Mycoses size
over 2 μm
35
Fungi - Mycoses structure
Eukaryotic Haploid or diploid DNA Single or multiple nuclei Rigid chitinous cell wall outside cytoplasm Single or multicellular
36
Single or multicellular e.g.
- yeast (spheroid single cells budding and division) or - Filamentous form/moulds. – hyphae (e.g. Aspergillus spp) multinucleate branching hyphae forming mycelium Classification is complex and is based on morphology (growth form), mode of reproduction (sexual or asexual) and disease caused: 70,0000species ~300 human pathogens
37
Superficial mycoses
Skin, nail hair and mucous membranes (dermatophytes) or thrush (Candida albicans)
38
Cutaneous mycoses
e.g. Tanea – aka ringworm
39
Systemic mycoses
e.g Histoplasmosis | Histoplasma capsulatum
40
Dimorphic
microconidia and hyphae, | yeast like and spores
41
Oral Candidiasis / Candidosis
most common oral fungal infection carriage rates 20% - 75% without any symptoms. Usually Candida albicans
42
Yeast
normal constituent of the digestive and vaginal tracts Generally no problems in healthy people Opportunistic pathogens
43
Cryptococcus neoformans
Fungal yeast like form – encapsulated – large capsule
44
Pneumocystis carinii (now jiroveci)
Previously classified as a protozoan PCP in AIDS Single cells (amoeboid) forms cysts containing spores
45
Athletes foot - Tinea pedis
Dermatophytes | multiple septate branching hyphae on microscopy
46
Ringworm (Dermatophytosis)
40 types of fungi can cause ringworm. DO NOT confuse with pinworm, round worm
47
Tinea unguium
of the nails is termed onychomycosis
48
Protozoa
``` Single cells 5 to 300 μm Single or multiple nuclei Haploid DNA. Morphology varies throughout life cycle` May have flagella ```
49
complex life cycles
Trophozoites, cysts and other morphotypes
50
Giardia lamblia
Trophozoite stage | Cyst stage
51
Protozoa - structures
e.g Plasmodium falciparum (malaria) Uninfected erythrocytes Schizont Trophozoites (ring forms)
52
Entamoeba histolytica
50 Million people infected Liver abscess + diarrhoea Faecal cyst
53
Trichomonas vaginalis
Common STI | trophozoite
54
Trypanosoma brucei
Trypanosomaa spp – vector tetse fly or reduviid bug (Chagas disease; Sleeping sickness) Blood stage
55
Helminths
These are multicellular parasitic worms Different morphology and sizes at different life cycle stages They can be microscopic or visible to the eye Multicellular
56
3 Groups of parasites
Cestodes are tapeworms e.g. Taenia saginata, the beef tapeworm; Trematodes are flatworms or flukes and include Schistosoma haematobium the cause of bilharzia or schistosomiasis filarial worm Onchocerca volvulus – River Blindness Nematodes which are roundworms e.g. Ascaris lumbricoides
57
River Blindness- Oncocerciasis
microfilariae migrate to eyes
58
Schistosomiasis
microfilariae
59
Helminths- Cestode
Tape worm -Taenia saginata Egg shed in faeces (human) Cysts in muscle (beef) ``` Adult tapeworm (human) 2 – 4 metres long 700- 1000 segments ```
60
Helminths- Trematoda
Schistosoma haematobium Egg shed in urine (human) (via snails) Metacercaria in water (burrow into skin) Adult fluke in human
61
Helminths - nematodes
Ascaris lumbricoides Egg shed in faeces Adult worm
62
Enterobious virmicularis
a nematode – common in UK children threadworm or pinworm Asymmetical shape (50 uM) Sticky tape mount to pinworm eggs

Fundamentals of Pathology (23 decks)

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