diagnostic and typing methods

Question 1

bacterial detection methods

Answer 1

microbiological culture
- on suitable agar medium
- isolate bacteria
- identify by characterisation of enzyme activities and sugar fermentation tests

molecular biological
- DNA probes
- polymerise chain reaction

Question 2

What are DNA probes?

Answer 2

segments of DNA that have been labelled with chemiluminescent, fluorescent or radioactive agents

Question 3

types of DNA probes

Answer 3

whole genomic
cloned gene
oligonucleotide

Question 4

Microbiological culture advantages

Answer 4

yields bacterial isolates for future testing and study
e.g.g antibiotic sensitivities

Question 5

microbiological culture disadvantages

Answer 5

• requires viable cells
• insensitive
• only small numbers of samples can be analysed at once
• inconclusive results
• labour intensive

Question 6

PCR advantages

Answer 6

highly specific
sensitive
can be used to directly detect bacteria specimens

Question 7

DNA probes and PCR - advantages

Answer 7

less time consuming than culture methods
very sensitive
can directly detect bacterial DNA within clinical samples
do not require viable cells, samples do not have to be analysed immediately
can detect uncultivable species

Question 8

disadvantages of DNA probes and PCR

Answer 8

may detect dead cells
detects only pre-selected species