Detection of microbial contamination in herbal products MCQs With Answer

Introduction

Detection of microbial contamination in herbal products is a crucial skill for M.Pharm students in the Herbal and Cosmetic Analysis course. Herbal materials and finished herbal preparations are susceptible to bacteria, yeasts, molds and specific pathogens due to raw material origin, incorrect drying, poor storage and processing conditions. This quiz set focuses on classical pharmacopeial tests (microbial limits, sterility, endotoxin), selective media and culture techniques, as well as modern rapid methods (PCR, ATP bioluminescence, MALDI-TOF), sampling, neutralization and interpretation of results. Understanding these concepts helps ensure safety, regulatory compliance and reliable quality control of herbal products.

Q1. Which pharmacopeial test is primarily used to quantify the total aerobic microbial load in a powdered herbal material?

• Membrane filtration followed by enrichment in selective broth
• Most Probable Number (MPN) test for coliforms
• Plate count on non-selective agar (total aerobic microbial count)
• Gram staining and microscopic enumeration

Correct Answer: Plate count on non-selective agar (total aerobic microbial count)

Q2. Which agar is most appropriate for the enumeration of yeasts and molds from herbal powders?

• Plate Count Agar (PCA)
• Potato Dextrose Agar (PDA) with antibiotics
• Violet Red Bile Glucose Agar (VRBG)
• Baird-Parker Agar

Correct Answer: Potato Dextrose Agar (PDA) with antibiotics

Q3. WHO guidelines commonly recommend that total aerobic microbial count (TAMC) in herbal materials should not exceed which of the following limits (CFU/g)?

• 10^2
• 10^4
• 10^5
• 10^7

Correct Answer: 10^5

Q4. Which organism is considered an objectionable organism in many pharmacopeial monographs and must be absent in 10 g of herbal material?

• Staphylococcus aureus
• Escherichia coli
• Salmonella spp.
• Bacillus subtilis

Correct Answer: Salmonella spp.

Q5. What is the preferred culture medium for selective isolation of Pseudomonas aeruginosa from herbal creams?

• Cetrimide agar
• Xylose Lysine Deoxycholate (XLD) agar
• Sabouraud Dextrose Agar
• MacConkey agar

Correct Answer: Cetrimide agar

Q6. When a herbal extract contains residual antimicrobial plant secondary metabolites that may suppress microbial growth during testing, which approach is recommended to obtain accurate counts?

• Use higher incubation temperature to overcome suppression
• Add neutralizing agents or perform sample dilution and use validated neutralizers
• Incubate for a shorter time to reduce stress
• Only use direct microscopy for enumeration

Correct Answer: Add neutralizing agents or perform sample dilution and use validated neutralizers

Q7. Which rapid molecular method allows sensitive detection and quantification of specific pathogenic DNA directly from a herbal sample?

• ATP bioluminescence
• Quantitative PCR (qPCR)
• Culturing on non-selective agar
• Gram staining

Correct Answer: Quantitative PCR (qPCR)

Q8. Membrane filtration is preferred over plate count when testing a liquid herbal preparation primarily because:

• It selectively grows only fungi
• It can concentrate low numbers of microorganisms from large volumes
• It prevents growth of Gram-negative bacteria
• It eliminates the need for sterile technique

Correct Answer: It can concentrate low numbers of microorganisms from large volumes

Q9. Which test is essential for sterile herbal products (e.g., sterile eye drops formulated from herbal extracts) to demonstrate absence of viable microorganisms?

• Microbial limits test (TAMC/TYMC)
• Sterility test (pharmacopoeial sterility testing)
• Yeast and mold count only
• Gram staining of the product

Correct Answer: Sterility test (pharmacopoeial sterility testing)

Q10. Which of the following is a common inhibitor encountered in DNA extraction from herbal matrices that can interfere with PCR detection of microbes?

• Peptone
• Polyphenols and polysaccharides
• Glucose
• Sodium chloride at low concentration

Correct Answer: Polyphenols and polysaccharides

Q11. What does ATP bioluminescence primarily measure when used for microbial monitoring of herbal product surfaces or process equipment?

• Only DNA from dead cells
• Overall biological ATP (indicative of viable organisms and organic residues)
• Endotoxin levels
• Colony forming units per gram

Correct Answer: Overall biological ATP (indicative of viable organisms and organic residues)

Q12. Which selective medium is commonly used for isolation and presumptive identification of Escherichia coli from herbal samples?

• Thiosulfate-citrate-bile salts-sucrose (TCBS) agar
• MacConkey agar or Eosin Methylene Blue (EMB) agar
• Mannitol Salt Agar
• Sabouraud Dextrose Agar

Correct Answer: MacConkey agar or Eosin Methylene Blue (EMB) agar

Q13. Which rapid identification technique provides proteomic fingerprinting for bacterial species isolated from herbal products?

• API biochemical strips
• MALDI-TOF mass spectrometry
• Gram staining
• qPCR targeting 16S rRNA

Correct Answer: MALDI-TOF mass spectrometry

Q14. In a microbial limits test, the term “CFU” stands for:

• Cell Formation Units
• Colony Forming Units
• Contamination Frequency Units
• Colony Fluorescence Units

Correct Answer: Colony Forming Units

Q15. Which of the following is the most appropriate initial enrichment broth for recovery of Salmonella from herbal samples before plating onto selective agar?

• Tryptic Soy Broth with polysorbate
• Selenite F or Rappaport-Vassiliadis enrichment broth
• Sabouraud Dextrose Broth
• Mannitol Egg Yolk Polymyxin (MYP) broth

Correct Answer: Selenite F or Rappaport-Vassiliadis enrichment broth

Q16. Which objectionable organism’s presence in herbal products signals potential fecal contamination and is often specifically tested for?

• Staphylococcus epidermidis
• Escherichia coli
• Bacillus cereus
• Candida albicans

Correct Answer: Escherichia coli

Q17. For endotoxin testing of water used in preparation of herbal injections, which assay is pharmacopeial and widely used?

• Gram staining
• Limulus Amebocyte Lysate (LAL) test
• Plate count on PCA
• ELISA for total protein

Correct Answer: Limulus Amebocyte Lysate (LAL) test

Q18. Which practice is important when preparing herbal sample dilutions for microbial enumeration to avoid carryover of antimicrobial compounds?

• Use organic solvents only
• Perform appropriate neutralization and validated serial dilutions
• Filter sterilize all herbal suspensions before testing
• Use high incubation temperatures to inactivate metabolites

Correct Answer: Perform appropriate neutralization and validated serial dilutions

Q19. Which organism is commonly associated with food-borne illness from herbal spices and may be specifically investigated during contamination assessment?

• Bacillus cereus
• Micrococcus luteus
• Lactobacillus acidophilus
• Penicillium chrysogenum

Correct Answer: Bacillus cereus

Q20. Which approach offers the fastest confirmation of a specific pathogen (e.g., Salmonella) directly from a herbal sample, reducing time compared with culture-based methods?

• Standard plate count using non-selective agar
• Enrichment culture followed by biochemical tests only
• Direct PCR or qPCR assays targeting pathogen-specific genes with validated extraction
• Gram staining and colony morphology observation

Correct Answer: Direct PCR or qPCR assays targeting pathogen-specific genes with validated extraction

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