PATHOGENS Flashcards
Pathogens
Pathogens are anything that can cause a disease or trigger an immune response (inflammatory reaction).
Inflammation
Inflammation – a biological response to harmful stimuli. Includes:
- A vascular response – vasodilatation and permeability to allow fluids migrate into the tissue.
- Cellular response – 𝑅𝐵𝐶 come to the site of the pathogen and fight it.
Sings of inflammation in a tissue:
- Redness – due to vasodilatation (the presence of more 𝑅𝐵𝐶 causes the site to be redder).
- Heat – due to vasodilatation (the presence of more 𝑅𝐵𝐶 increases the heat in the area).
- Swelling – due to vasodilatation permeability more fluids can pass and accumulate.
- Pain.
- Loss of function (of the cell tissue)
Types of organism pathogens:
- Bacteria.
- Viruses.
- Fungi.
- Parasites
Bacteria
Unicellular prokaryotic organism found in every habitat on Earth. They can be both harmful and beneficial.
Bacteria structure
- bacteria do not have membrane bond organelles.
- bacteria have circular 𝐷𝑁𝐴 in a nucleoid region.
- Some bacteria may have plasmids (small circular 𝐷𝑁𝐴 segments in their cytoplasm).
- Some bacteria may have additional structures:
- Flagella – helps in movements.
- Fimbriae – helps in movements and tearing or
sticking to tissues.
- Pili – allows plasmid exchange. - bacteria have cell wall; it is composed of:
- Phospholipid bilayer.
- Peptidoglycan layer. - Some bacteria may have capsule – allows bacteria to stick to tissues.
- Some bacteria may form endospores – method that let bacteria be durable and survive in any place under any conditions. This happens by the stopping of all the bacteria’s metabolic processes.
Bacterial Replication
Bacteria are reproduced by binary fission. It is a form of asexual reproduction producing two identical
clone-daughter cells. In this process there is no genetic variability (therefore, no incensement in genetic
variability).
Bacteria can increase genetic variability by:
- Conjugation (bacterial mating) – transfer of plasmids between bacteria through pili.
- Transformation – incorporation of 𝐷𝑁𝐴 from the environment.
- Transduction – a transfer of 𝐷𝑁𝐴 between bacteria by viruses called bacteriophages.
Classification of bacteria:
- Shape of the bacteria.
2.Gram stain – a technique used to differentiate bacteria base on the structural difference in their cell wall (presence of peptidoglycan).
Classification of bacteria by Shape
- Cocci – circle shaped.
- Rods/bacilli – rod shaped.
- Spirilla – spiral shaped
Classification of bacteria by Gram
- Gram positive (𝐺 +) pained blue – has two layers in the cell wall:
- Phospholipid bilayer.
- Think peptidoglycan layer.
- Gram negative (𝐺 −) painted red – has three layers in the cell wall:
- Phospholipid bilayer.
- Thin peptidoglycan layer.
- Lipopolysaccharide.
Gram Positive
Gram positive bacteria have a thick layer of peptidoglycan in their cell wall. Peptidoglycan absorbs the crystal violet staining, making it appear blue under the microscope. Gram positive are more receptive to
antibiotics then gram negative, due to their expose peptidoglycan layer (gram negative have more
membrane layer).
Examples of Gram Positive
- Streptococcus (𝐺 + 𝐶𝑜𝑐𝑐𝑖 ) – can cause tonsillitis and meningitis that can lead to:
- Endocarditis – valve inflammation.
- Glomerulonephritis – kidney inflammation. - Staphylococcus (𝐺 + 𝐶𝑜𝑐𝑐𝑖 ) – can cause folliculitis and osteomyelitis that can lead to:
- Toxic sock syndrome (𝑇𝑆𝑆) – characterized by
fever, muscle aches and low blood pressure.
- Methicillin resistant staphylococcus aureus (𝑀𝑅𝑆𝐴)
–> hospital germ (resistant to most antibiotics)
Gram Negative
Gram negative bacteria have a cell wall with thin layer of peptidoglycan covered by additional outer
membrane. Peptidoglycan layer is sandwiched between two membranes and can’t absorb the crystal violet stain, thus painted red under the microscope.
Examples of Gram negative
- Salmonella – causes severe food poisoning, and can come from raw eggs or chickens.
- Escherichia coli (𝐺 − 𝑅𝑜𝑑) – commonly found in the lower intestine and are usually harmless.
Pathogenic stains can cause serious food poisoning, gastro enteritis(𝐺𝐸) and urinary truck infection (𝑈𝑇𝐼). - Yersinia pastis (𝐺 − 𝑐𝑜𝑐𝑐𝑖𝑏𝑎𝑠𝑖𝑙𝑖) – caused the black plague.
