Microbiology Cameron McCloskey Flashcards
Gram+ organisms stain…
Purple
Stain well due to thick peptidoglycan layer
Gram- organisms stain…
Pink
Thinner peptidoglycan layer doesn’t retain stain well
Endotoxin is produced by…
Grams -
Exotoxin is produced by…
A
Gram+ organisms and G-
Exported from the cell
Gram+ cocci in chains are?
A
Streptococciستريبتو كوسكاي
Gram+ cocci in clusters are?
A
Staphylococci ستافيلو كوكاي
Coagulate positive in clusters
The test to classify different Streptococci spp.? ستريبتو كوكاي
Haemolysis
Alpha (partial) - Strep. pneumoniae + viridans
Beta (complete) - Group A (pyogenes) and B Strep.
Gamma (none) - Enterococcus sp.
Examples of: Alpha-haemolytic Streptococci?
A
Strep. pneumoniae نومونيا + “viridans” group
Examples of: Non-haemolytic Streptococci?
A
Enterococcus sp. انترو كاكس
The test to distinguish Staphylococcus aureus from other Staph. spp.?
A
Coagulase test
+ve = Staph. aureus اوريس
-ve = other Staph. spp. and epidermidis (common skin commensals)
Opportunistic pathogen? ابرو تونيستك
Probably only cause infection in immunocompromised individuals
Virulence?
A
Degree of pathogenicity of an organism
Stages of viral replication?
-Attachment
-Entry - endocytosis
-Uncoating - viral nucleic acid released from capsid
-Nucleic acid and protein synthesis - host ribosomes used or polymerases
-Assembly = nucleic acid and proteins packed together
-Release =
Budding- Viruses released with envelope
derived from host cell membrane
Lysis- Virus accumulates until cell bursts,
kills cell
Virus detection?
PCR
Antigen detection
What do cytoxic T lymphocytes do in virus immunity?
A
Recognise proteins on cell surfaces as foreign and signals infected cell to commit suicide in order to prevent formation of new viruses
The 5 methods of spread of infection are…
A
Inhalation, Ingestion, Inoculation, mother to Infant, Intercourse
Viruses contain RNA or DNA, never both. True/False?
True
Size of their capsid (protein coat) limits space
Of both gram positive and negative which of the two has a larger periplasmic space?
A
Gram negative
(They have two different periplasmic spaces)
Which bacteria class has two membranes?
A
Gram negative
(Outer and plasma)
What exists on the outside of gram negative bacteria that confer antigenic properties?
A
Lipid polysaccharides (endotoxins)
Besides having antigenic properties, what other important characteristic do lipid polysaccharides possess?
A
They have bacterial toxin properties which cause damage to neighboring cells and evoke an inflammatory response
Why are gram positive bacteria more susceptible to antibiotics?
A
The outside peptidoglycan layer can act as a target for antibiotics such as penicillin
What happens when antibiotics bind to the peptidoglyan layer of gam positive bacteria?
A
The peptide cross links within peptidoglycan are broken down
What are flagella and fimbriae (pili)?
A
Extracellular proteinaceous extensions