PoD - Medical Microbiology Flashcards
1
Q
what are the two types of cells?
A
- prokaryotes (no nucleus present - bacteria)
- eukaryotes (nucleus, more complex cell wall)
2
Q
what are the main microbial causes of infection?
A
- bacteria (prokaryotic) - round, spiral or rod shaped single celled organism
- viruses (unclassified) - a unique, acellular, metabolically inert organism that replicate within living cells
- fungi (eukaryotic) - saprophytic and parasitic spore-producing eukaryotic typically filamentous organisms; including moulds, yeasts
- parasites (eukaryotic) - an organism living within another organism
- prions (unclassified) - protein that resides on the surface of brain cells. Becomes pathogenic via mutation or an infected tissue - accumulation causes disease
3
Q
what types of specimens are taken?
A
- sterile sites - brain, CSF (if micro-organism is detected = medically significant)
- non-sterile sites - skin, intestine, stomach
4
Q
where are common specimens for bacterial cultures?
A
- urine - UTI
- sputum - respiratory TI
- throat - tonsillitis
- swabs - wound
- faeces - bacterial diarrhoea
- blood culture - septicaemia
- CSF - meningitis
- aspirate of pus - abscess
5
Q
what are common healthcare associated infections?
A
- Staphylococcus aureus and clostridium difficile
- MRSA, VRE are multi-drug resistant organisms
6
Q
what are the common characteristics of bacterium?
A
- capsule, cell wall, cytoplasmic/inner/plasma membrane, cytoplasm, ribosomes, singe chromosome, flagellum, fibriae
7
Q
differences between gram positive/negative bacteria
A
- gram +ve bacteria have plasma membrane, periplasmic space and thick peptidoglycan layer
- gram -ve bacteria have plasma membrane, periplasmic space, thin peptidoglycan layer and thick outer membrane (thick LPS layer)
- gram +ve = stained purple
gram -ve = stained pink/red
8
Q
what is on the cell surface of bacteria?
A
- penicillin binding proteins (PBP) cross links
- peptidoglycan (contribute to strength and shape of bacterium)
- lipopolysaccharide (over-expression of LPS can illicit strong immune response
9
Q
how are spores formed?
A
- mainly formed by gram +ve bacteria
- bacteria divide symmetrically and rapidly
- spores form to resist environmental stresses, however when environment returns to favourable conditions, the bacteria will continue to divide
10
Q
what is a plasmid?
A
- plasma has extrachromosomal information
- plasmids participate in process of conjugation (joins 2 bacterium)
- conjugation allows exchange of ‘genetic’ information - spread of antibiotic resistant genes
11
Q
what is a bacteriophage?
A
- virus that can eat up bacteria
- end plate binds to bacterium and tail fibres hold the virus in place
- inserts viral DNA into the bacterium and takes over bacterium DNA machinery
- viral DNA is produced, lots of phages are synthesised and burst out of the bacterium
12
Q
what is a virus?
A
- non-cellular, genetic element that cannot replicate independently of a living (host) cell
13
Q
what is a virion?
A
- a virion is required for transmission from one host cell to another - wrapped in a capsid
- the capsid is the infective form
- once the capsid binds to the target cell, the virion uncoats, shredding the lipid envelope and eventually the protein capsid
- there is replication of genomic nucleic acid (via mRNA synthesis)
- newly synthesised nucleic acid can go on to create viral proteins or more visions
14
Q
how are viruses transmitted?
A
- blood, sexual, faecal-oral, airborne, close contact, zoonotic
- host range - some viruses may only infect humans but others infect other animals
- could be transmission of a novel virus to humans or co-infection of human and animal/bird strains in one organism may lead to recombination –> generation of new strain.
15
Q
what is viral latency?
A
- following primary infection, some viruses lie dormant in the cell
- the full viral genome is retained in the host cell, but expression is restricted
- no viral particles are produced
- however, reactivation or viral replication can occur and cause disease
