W6- Lecture 29- Causes of infections Flashcards by Alexandros Kizas

what is the size of a virus compared to cellular organisms and bacteria ?

Smaller than cellular organisms

1/100th size of bacteria

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name the components that form a virus

3 major components: genetic material- either DNA or RNA;
protein coat;
lipid envelope which is derived from the host cell.

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describe viral replication (in simple terms)

Viruses contain genetic material but no organelles

they rely on their host organelles/ systems to reproduce

They use surface protein(s) to bind to a cell, insert their genetic material into it

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describe the structure of a bacteria

Unicellular organisms
Cell membrane
Cell wall
No nucleus
Genetic material is DNA but not bounded by a membrane(plasmids)
Reproduce asexually
Some move using flagella and attach via fimbriae

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what do these three terms indicate about a bacterium’s shape?

coccus/cocci
bacillium/bacilli
spirilum/spirilli

coccus/cocci- round

bacillium/bacilli- rod shaped

spirillum/spirilli- spiral

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what is the difference between gram positive and negative bacteria cell walls?

gram-positive= one cell membrane one cell wall
one wall made of peptidoglycan

gram-negative=one cell membrane two cell walls
one wall made of peptidoglycan
second wall made of lipopolysaccharides + proteins

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which type of bacteria gram positive and negative is the immune system more to ?
and why ?

gram negative

because of the lipopolysaccharides + proteins can cause more serious disease

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how do we write bacteria names ?

genus then species
Capital letter for the Genus, lower case for species
(always in italics if possible if not then underline )

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describe the structure of fungi

Kingdom of their own
Eukaryotes
Cell membrane, cell wall, nucleus and cytoplasmic structures
Reproduce sexually and asexually

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name three types of fungi which are likely to cause disease

Yeasts - likely to cause disease

Moulds

Diamorphic fungi (can switch between types

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name three mild infections caused by fungal infections

thrush,
athletes foot,
ringworm

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name the three classes of parasites

with examples

Ectoparasites
live outside body
Fleas
Ticks
Endoparasites
Iive inside body
Worms
Epiparasites
a parasite which lives on another parasite
Malaria (mosquito)

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what are the two general classes of parasites

+example

Unicellular organisms- Protozoa

Worms- Helminths

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descibr the parasitic disease called giardia

+ life cycle

Cause bloody diarrhoea

Caught from drinking infected water

May be seen in stool under a light microsope

Cyst form aids survival + spread

Some protozoa have life stages alternating between proliferative stages and dormant cysts.
As cysts, protozoa can survive harsh conditions, such as exposure to extreme temperatures and harmful chemicals, or long periods without access to nutrients, water, or oxygen, in addition enabling a parasite to survive outside of the host, and therefore allowing transmission from one host to another.
Protozoa can reproduce by binary fission or multiple fission. Some protozoa reproduce sexually, some asexually, while some use a combination. An individual protozoon is hermaphroditic.

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describe malaria

where it comes from
what cells it infects

One of the biggest killers worldwide

Reproduce in female anopheles mosquito

Infect human red blood cells

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how many different types of malarial parasite?

which is most severe
why might treatment now might be a problem

Falciparum- most severe 
Resistance to treatment is now a problem in many areas
chloroquine sensitive malaria 
chloroquine resistant malaria 
multi-resistant malaria

name three types of worms + structure

Cestodes (tapeworms)
Segmented, flat

Trematodes (flukes)
Unsegmented, flat

Nematodes (round worms)
Cylindrical, have digestive tract with lips, teeth and anus

where can you get Cestodes (aka tapeworms) from ?

+ impacts

Tapeworms
Fish, pork, beef tapeworms

Malabsorption
Malnutrition in chronic disease
Cysts in muscle or brain

what can Nematodes

(aka Round worms) form ?

Diarhoea / malabsorption

E.g. Elephantiasis

name 5 types of Trematodes/flukes

Lung flukes
Liver flukes
Pancreatic flukes
Intestinal flukes
Blood flukes- Schistosoma (2nd most socioeconomically devastating parasiticdisease)

describe the life cycle of a blood fluke/Schistosoma

+ causes of infection

Flukes have part of their life cycle in fresh-water snails and enter the body by penetrating the skin whilst the host is swimming.
The adult worms migrate to veins- some species to veins of ureter and bladder and others to the mesenteric veins, where the female lives inside a groove on the male.
The worms live there and lay eggs for the rest of the host’s life. Once produced, the eggs penetrate the vascular endothelium, enter the bladder or gut lumen, and are excreted in urine or stool.
The clinical disease is commonly found in children who play in the water, and is devastating socioeconomically. Symptoms are diarrhoea, fever, abdominal pain, hepatosplenomegaly or cystitis, urethritis and eventually bladder cancer.
1- fresh water snails
2- flukes penetrate skin
3- migrate to veins + Diarrhoea, fever and abdominal pain

describe prions
size 
nucleic acid ?
how it causes disease 
how to destroy

Smallest infective agents known
lack nucleic acids (not a living organism )
Proteins fold abnormally and accumulate, mainly in neural tissue
They are very difficult to destroy
Concerns over cleaning surgical instruments
extremely heat resistant

name 5 prion diseases

+ describe

CJD- fatal, degenerative neurological disease
Affects 1 in a million people each year
Transmitted through contaminated human growth hormone, surgical instruments and corneal grafts
Variant CJD- typically occurs in young adults
BSE- occurs in cattle
Scrapie- occurs in sheep
Kuru- similar to vCJD,
occurred in Papua New Guinea in 1950s
thought to be spread by cannibalism

describe growth requirements for micro-organisms (bacteria )

Every living organism requires nutrients to meet their energy needs and for the synthesis of their building blocks

Nutrient provide the necessary elements such as carbon, hydrogen, oxygen and nitrogen (CHON)

Microbes are very successful in obtaining nutrients from variety of sources. This helps them inhabit all possible environments

Growth and reproduction require synthesising new molecules.

Energy is needed to build those molecules.

name and describe the two pathways of metabolism

Catabolic pathways Break down molecules to produce energy. (larger substrates, smaller products) Anabolic pathways Use energy to combine small molecules into macromolecules (energy+ source of elements especially carbon)

what are the primary nutritional groups

source of energy source of electron donor source of elements (carbon)

name two examples of each primary nutritional group

source of energy Phototrophs: uses sunlight energy to produce its energy (photophosphorylation) Chemotrophs: extract energy from chemical bonds mainly by oxidation of electron donor compounds. ``` source of the electron donor Organic compounds (organotrophs) e.g. Sugar, fat...etc Inorganic molecules: (lithotrophs) e.g. Ferrous iron to ferric iron Amonia nitrite ``` source of elements (carbon) Autotrophs: produce complex organic compunds from simple inorganic ones Heterotrophs: consume organic molecules as a source of carbon.

``` what does the prefix in terms of energy mean auto- hetero- photo- chemo- ```

auto- using carbon dioxide hetero- using organic compounds photo- using light chemo- using chemical compounds such as hydrogen, sulfur and nitrogen

using the relevant prefixes(auto- hetero-photo-chemo-) describe ; humans plants nitrifying bacteria

humans- Chemoheterotrophs plants- Photoautotrophs nitrifying bacteria- Chemoautotrophs

name 6 physical requirements for growth

``` Temperature Water PH Osmolarity Oxygen Pressure Light Physical space availability ```

why is temperature important for growth

Temperature affect protein structure and fluidity of the cytoplasm and the cytoplasmic membrane. Minimum growth temperature: lowest temperature that a given organism can carry out its metabolic activities Maximum growth temperature Optimum growth temperature: temperature at which metabolic activity is at its peak and thus growth rate is the highest.

what optimum temperature would you expect pathogenic bacteria to be?

same as human cells- approx 37C

describe why water is important for bacteria growth

Essential for life Virtually all bacteria requires ‘wet’ habitat. As drying kills most bacteria Water activity (Aw): the vapour pressure of a sample divided by that of pure water at the same temperature. Bacteria usually require at least Aw= 0.8 (G-ve requires higher 0.97), and fungi at least 0.7 (water Aw= 1). Low Aw reflects high concentrations of solutes (hypertonic solution). Bacterial growth correlate to Aw more accurately than to absolute water content

decribe the PH effect on bacteria growth

PH effect: High or low PH inhibit microbial growth except for few! Acidic conditions are body defense mechanism e.g. stomach and vagina (via fermentation by normal flora) Acidophiles can tolerate acidic conditions. Some are obligate acidophiles Alkalinophile lives in alkaline media like soil and alkaline water (e.g. Vibrio cholerae). In both, intracellular PH is near normal

describe the Classification of Organisms Based on O2 Requirements

Obligate aerobes: requires O2 for energy production (respiration) Anaerobes : do not use O2 for energy production Facultative Anaerobes: can survive with or without O2 Microaerophiles: can tolerate oxygen levels from 2-10% (limited ability to detoxify hydrogen peroxide and superoxide radicals) Aerotolerant: Anaerobes but have some enzymes that detoxify oxygen’s poisonous forms.

describe the defence systems of the body against microbes

``` Skin Mucus membranes Stomach acid Commensal microflora Immune system Innate Learnt Behaviour (e.g. good hygiene practices) ```