Bugs In The System Flashcards
Viruses
- obligate cell parasites
- DNA or RNA present NOT BOTH
Infection
most of the side effects are due to our own immune response
- by pathogenic microbes (bacteria, fungi and viruses)
- by an infestation Arthropods e.g. by parasitic worms
Tissue
- most interactions between microbes and tissue is via the epithelial tissue
Tissue preparation
- deliberately removes many microbes
- magnification is not sufficient to see microbes
Microbiomes
- our normal fauna of microbes
- have the metabolic power and effects at least equivalent to an organ like the liver
- differences in individual microbiomes are linked to health and diseases such as obesity, diabetes and psoriasis
The Gram Stain
GRAM POSITIVE - thick cell membrane obstructs the extraction of the stain (large amounts peptidoglycan) - BLUE
GRAM NEGATIVE - has an outer membrane (very little peptidoglycan) - PINK
- +vely charged crystal violet binds to -vely charged cell components
- iodine forms large molecular complexes with crystal violet
- acetone or methanol extract the complexes from the gram negative but not from the gram positive bacterial cell walls
- red dye is used to stain the unstained gram negative cells
Bacterial structure
- cocci (spheres)
- bacilli (rods)
- streptococci (spheres in lines)
- staphylococci (spheres in clusters)
- diplococci (pairs of spheres)
External - long flagella
- shorter fimbriae
- cell envelope
- capsule
Bacterial resistance
- bacterial can share genes in a way that is being selected for with our use of antibiotics
Acid Fast Stain
used for Mycobacteria such as TB and leprosy
- not visualised with the gram stain as they have a more complex cell wall
+ve AFB smear = infected patient
Bacterial Growth
- broth turbidity (lag, exponential and stationary phases of growth)
can happen in fluid filled cavities e.g. urinary tract - colonies - unrepresentative of normal life (grown from a single bacterial cell and provided with ideal conditions)
easy identification and counting - biofilms (main form in human body)
can happen around medical devices - why they have to be removed
Gram Positive
Staphylococcus aureus - MRSA
Streptococcus pyogenes - impetigo
Clostridium perfringens - food poisoning
Gram Negative
Escherichia coli - E. coli
Salmonella spp. - salmonella
Neisseria gonorrheae - gonorrheae
Infection
The establishment of a organism on or in a host associated with its multiplication and DAMAGE or DYSFUNCTION of the host specifically related to that of the organism or its products.
Prokaryotic microbes
bacteria
- no nuclear membrane or membrane bound organelles
- DNA & RNA present
