October 04, 2021: Pharmaceutical Interview Questions and Answers

#MicrobialConcentrationByOpticalDensity #CommonSourcesOfPyrogens #MethodUsedToTestPyrogen

1. Explain the method of measurement of microbial concentration in suspension by optical density?

A spectrophotometer method is used to measures turbidity of inoculum suspension. When light passes through a suspension of microorganisms, light gets scattered and the amount of scatter is an indication of the concentration present in the suspension.

While doing the estimation using this method, a calibration curve needs to be constructed using series of the known concentration. Based on the calibration curve, unknown concentration can be easily identified.

2. What are the common sources of pyrogens?

Non-bacterial source:

● Antigens

● Poly nucleotides

● Steroids

● Adjuvants

● Viruses

● Fungi

Bacterial source:

● Streptococcal toxins

● Staphylococcal enterotoxins

● Mycobacterial cell wall components

● Bacterial cell wall – lipopolysaccharides (endotoxins)

3. What are the method used to test pyrogens and endotoxins?

● Rabbit pyrogen test

● Limulus Amoebocyte Lysate (LAL) testing for bacterial endotoxin