Lab 5: Antibiotic Resistance 1 Flashcards
What is the purpose of using APT-azide-CaCO3 plates in LAB enrichment?
To selectively grow lactic acid bacteria by inhibiting aerobic bacteria and visualizing acid production through zones of clearing
What causes the zones of clearing around LAB colonies on the APT-azide-CaCO3 plates?
LAB ferment dextrose and produce lactic acid, which dissolves the calcium carbonate in the medium
Which bacterium involved in tooth decay behaves similarly to LAB on APT-azide-CaCO3 plates?
Streptococcus mutans
How does S. Mutans cause tooth decay?
By producing lactic acid that dissolves tooth enamel and dentin, similar to how LAB dissolve CaCO3 on plates
What is antibiotic resistance?
The ability of bacteria to survive exposure to antibiotics that would normally kill them
How does antibiotic resistance typically arise in bacteria?
Through horizontal gene transfer of pre-existing resistance genes in the environment
What role do livestock and hospitals play in antibiotic resistance?
They provide environments where pathogens and resistant bacteria can interact and exchange resistance genes
What is the function of oxytetracycline (oxytet) in the experiment?
It inhibits bacterial protein synthesis by binding to the 30S ribosomal subunit
What method is used to quantify bacteria in the swab samples?
The viable plate count method using serial dilutions and colony counting
Why are serial dilutions used before plating samples?
To reduce bacterial concentration so that colonies are countable (30-300 colonies per plate)
What is the purpose of gram standing selected colonies?
To confirm whether the bacteria are gram positive which is typical for LAB
