Bacteria Flashcards
What is the purpose of flagellum?
Aid motility of the bacterium
Do bacteria have a nucleus?
No they contain a single chromosome. And sometimes extra DNA within a plasmid.
What is the function of Fimbriae?
Aids attachment and adherence to other cells.
What colour do gram positive bacteria stain?
Purple.
What colour do gram negative bacteria stain?
Pink
What shape is cocci?
Spherical
What shape is bacilli?
Rod shaped
What is the function of the capsule?
Virulence factor - aids the bacterial survival in the host by preventing phagocytosis.
What is the name given to a bacteria with a single flagella?
Monotrichous
What is the name given to multiple flagella that originate from one point on a bacteria?
Lophotrichous
What is the name given to bacteria that have a flagellum coming out from either side of it?
Amphitrichous
What name is given to bacteria that have flagellum all over it?
Peritrichous
What are spores?
Highly resistive, dormant structures produced by bacteria that allow it to survive in extreme conditions. Common in gram positive bacteria.
What are Plasmids?
Extra chromosomal entities out with the chromosome itself.
How do bacteria replicate?
Binary fission, producing identical progeny.
How do bacteria achieve genetic variation?
Spontaneous mutation and the transfer of DNA.
What is conjugation?
Sex between 2 bacteria using a pilus to transfer a plasmid from one to the other.
What is transduction?
The process of phage DNA integrating with the DNA of the bacteria. Tail and endplate provide grip throughout this process.
What signs and symptoms characterise clinical infection?
Inflammation Pain Pyrexia (increase in temp) Tachycardia Rigors Increased white cell count Increased C reactive protein.
What is a pathogen?
An organism which can cause disease.
What is a commensal?
An organism which is part of normal flora e.g E.coli in gut.
What is pathogenicity?
The capacity of a micro-organism to cause an infection.. It requires infectivity and virulence.
What is infectivity?
Ability to become established.
What is virulence?
Ability to cause harmful effects once established.
How to pathogens become established within a host?
Attachment - e.g E.coli attach by P-fimbriae and receptors on uroepithelial cells.
Acid resistance - Helicobacter pylori uses urease (ammonia from urea)
What are some virulence factors?
Genetically determined microbial components:
Invasiveness
Toxin production
Evasion of immune system
How are Exotoxins released?
Released extracellularly by the micro-organism
What are Enterotoxins?
Special form of exotoxins that work on the GI tract.
What is an Endotoxin?
Structurally part of a gram negative cell wall.
Give an example of an exotoxin?
Tetanus released by Clostridium tetani. The toxin binds to nerve synapses and inhibits the release of inhibitory neurotransmitters.
Give an example of an enterotoxin?
Cholera released by vibrio cholerae. Toxin increases CAMP levels. Inhibits uptake of Na+ and Cl- ions
Stimulates secretion of Cl- and HCO3- ions
Passive (massive) outflow of H2O
Causes death by dehydration
What are superantigens?
Exotoxins of Strep pyogenes and Staph aureus.
Able to stimulate the division of T cells in the absence of specific antigen. Results in overwhelming cytokine production which causes toxic shock.
How do endotoxins affect the body?
Induces severe uncontrolled host response:
Cytokine production
Fever, rigors, hypotension, tachycardia, collapse
Present in E.coli and other gram negative bacteria. Lipid A is the nasty part.
Give some examples of bacteria that are considered critical threat to humans?
Acinetobacter baumannii
Pseudomonas aeruginosa
Enterobacteriaceae
Give some examples of bacteria that are considered high risk to humans?
Enterococcus faecium Staphylococcus aureus Helicobacter pylori Campylobacter Salmonella Neisseria gonorrhoeae
Give some examples of bacteria that are considered medium risk to humans?
Streptococcus pneumoniae
Haemophilus influenzae
Shigella
What are some common gram positive bacteria?
Staphylococci and Streptococci and Enterococci (chains)
E.g Staph . aureus
Strep . pneumoniae
What is staph. aureus commonly resistant to?
Penicillin due to production of penicillinase.
Give some characteristics of coagulase-negative staphylococci?
Mainly skin commensals
Form biofilms and may be significant pathogens in the presence of foreign bodies/prostheses e.g. prosthetic heart valves etc or immunocompromised e.g. neonates
Give some examples of Streptococci sub species?
α- haemolytic (par@al haemolysis) - turn blood agar green e.g strep. pneumoniae
• β-haemolytic (complete haemolysis) - turn blood agar clear e.gFurther identified by carbohydrate surface antigens
• Non haemolytic - group A e.g Streptococcus pyogenes
group B e.g Streptococcus agalactiae
Name some examples of gram positive bacilli?
Clostridium difficile
Clostridium perfringens
Clostridium tetani
What are some characteristics of Clostridium difficile?
Difficult to culture
Important cause of diarrhoea, associated with toxin production, potentially fatal
Increased risk with antibiotic use.
Spreads via spores.
