BIOCHEMICAL TESTING

• What does TSI stand for in biochemical testing?


  Triple Sugar Iron
• What is the initial step in the identification of Enterobacteriaceae?


  Using TSI (Triple Sugar Iron) test
• What are the main components of TSI medium?


  • Protein source
  • Carbohydrates (CHO)
  • pH indicator (Phenol Red)
  • H2S indicator (Sodium thiosulfate)
• What color indicates lactose fermentation in TSI?


  Yellow
• What does a red/pink color indicate in TSI results?

  No fermentation of sugars
• What does H2S production indicate in TSI testing?


  Blackening of the medium
• What are the typical organisms tested with TSI?


  • Escherichia coli (E. coli)
  • Salmonella
  • Shigella
  • Pseudomonas
  • Alcaligenes
• What does LIA stand for in biochemical testing?


  Lysine Iron Agar
• What can LIA be used to determine about an organism?

  Whether it can deaminate lysine, decarboxylate lysine, and produce H2S
• What are the main components of LIA medium?

  • Small amount of protein
  • Glucose
  • Lysine
  • pH indicator (Bromcresol purple)
  • H2S indicator (Ferric Ammonium citrate)
• What color indicates lysine decarboxylation in LIA?


  Purple
• What does a yellow color indicate in LIA results?

  Fermentation of glucose
• What does K/K indicate in LIA results?


  Alkaline reaction with no H2S production
• What does K/A indicate in LIA results?


  Alkaline slant with acid butt and H2S production
• What are the typical organisms tested with LIA?


  • Salmonella
  • Shigella
  • Morganella
• What does a purple color indicate in LIA results?


  Decarboxylation of lysine
• How do the reactions of TSI and LIA differ in terms of H2S production?


  TSI can show H2S production through Ferrous Sulfate, while LIA uses Ferric Ammonium citrate.
• What is the significance of the color changes in TSI and LIA tests?

  They indicate the fermentation and metabolic capabilities of the organism
• What are the key reactions observed in TSI and LIA tests?

  • TSI: Yellow indicates fermentation, red indicates no fermentation, black indicates H2S production
  • LIA: Purple indicates decarboxylation, yellow indicates fermentation, K/K indicates alkaline reaction
• At what temperature should CSF specimens be stored?


  37°C
• What is the storage temperature for urine, stool, swab, viral specimens, sputum, and foreign devices such as catheters?


  4°C
• At what temperature should serum for serology be stored?


  • 20°C
• What is the storage temperature for tissue or specimens intended for long-term storage?


  • 70°C
• What are the biosafety levels and their corresponding risk categories?

  • BSL-1: Low Risk Microbes
  • BSL-2: Moderate Risk Microbes
  • BSL-3: High Risk Microbes
  • BSL-4: Highest Risk Microbes
• What is the primary characteristic of Biosafety Level 1 (BSL-1)?


  Suitable for work involving well-characterized agents not known to cause disease in healthy adults.
• Give an example of an agent classified under Biosafety Level 1.


  Bacillus subtilis
• What is the primary characteristic of Biosafety Level 2 (BSL-2)?


  Suitable for work involving agents of moderate potential hazard to personnel and the environment.
• Name an example of an agent classified under Biosafety Level 2.


  Hepatitis B virus
• What is the primary characteristic of Biosafety Level 3 (BSL-3)?


  Suitable for work with infectious agents that may cause serious or potentially lethal disease via inhalation.
• Provide an example of an agent classified under Biosafety Level 3.

  Mycobacterium tuberculosis
• What is the primary characteristic of Biosafety Level 4 (BSL-4)?


  Suitable for work with dangerous and exotic agents that pose a high individual risk of aerosol transmitted infections.
• Name an example of an agent classified under Biosafety Level 4.

  Ebola Zaire virus
• How do the biosafety levels differ in terms of risk to laboratory personnel?

  BSL-1 has minimal risk, while BSL-4 poses a high individual risk of aerosol transmitted infections.
• TSI is Butt/Slant which means Stab and Streak
• Carbohydrate composition of TSI

  • 10 Lactose
  • 10 Sucrose
  • 1 glucose
• pH indicator of TSI


  Phenol Red
• In phenol red, Y signifies 


  Acid
• In phenol red, R signifies


  Alkaline
• H2S indicator of TSI


  Ferrous Sulfate
• Sulfur compound of H2S came from


  Sodium thiosulfate