Microbial contamination in herbal products and its evaluation MCQs With Answer

Introduction: Microbial contamination in herbal products and its evaluation is a focused MCQ collection designed for M.Pharm students studying Advanced Pharmacognosy-II (MPG 202T). This set emphasizes practical and regulatory aspects of microbiological quality in herbal raw materials, extracts, semi-solid and liquid formulations. Questions cover sources of contamination, sampling and sample preparation, classical and rapid microbial enumeration methods, interpretation of TAMC/TYMC, detection of specified pathogens, endotoxin testing, preservative efficacy, mycotoxin concerns, and preventive strategies including GACP and GMP. The quiz aims to reinforce critical thinking for laboratory practice, quality control decision-making and compliance with pharmacopeial and WHO guidelines applicable to herbal medicines.

Q1. Which of the following is the most common initial source of microbial contamination in freshly harvested herbal raw materials?

• Manufacturing equipment in the processing plant
• Soil and phyllosphere microorganisms present on plant surfaces
• Packaging materials used after drying
• Preservatives added during extraction

Correct Answer: Soil and phyllosphere microorganisms present on plant surfaces

Q2. What does TAMC stand for in microbial quality testing of herbal products?

• Total Aerobic Microbial Count
• Total Anaerobic Microbial Count
• Total Antibiotic Microbial Count
• Total Aseptic Microbial Count

Correct Answer: Total Aerobic Microbial Count

Q3. According to WHO guidelines commonly applied to herbal medicines, the recommended maximum limit for Total Aerobic Microbial Count (TAMC) per gram for oral herbal products is generally:

• Not more than 10^2 CFU/g
• Not more than 10^3 CFU/g
• Not more than 10^5 CFU/g
• Not more than 10^7 CFU/g

Correct Answer: Not more than 10^5 CFU/g

Q4. Which incubation conditions are standard for enumerating yeast and molds (TYMC) in herbal products?

• Incubate on Tryptic Soy Agar at 35–37°C for 24 hours
• Incubate on Sabouraud Dextrose Agar at 20–25°C for 5–7 days
• Incubate on MacConkey Agar at 42°C for 48 hours
• Incubate on Blood Agar at 30–32°C for 2 days

Correct Answer: Incubate on Sabouraud Dextrose Agar at 20–25°C for 5–7 days

Q5. Which organism must typically be absent in 10 g of herbal medicinal product according to pharmacopeial/WHO requirements?

• Bacillus subtilis
• Salmonella spp.
• Lactobacillus spp.
• Micrococcus luteus

Correct Answer: Salmonella spp.

Q6. Which neutralizer is commonly included in microbiological diluents/media to inactivate residual chlorine disinfectant?

• Polymyxin B
• Sodium thiosulfate
• Lecithin
• Tween 80

Correct Answer: Sodium thiosulfate

Q7. The membrane filtration technique is preferred over pour/plate methods when:

• Products are highly colored but have low viscosity
• Preservatives in the sample may suppress colonies and volumes >1 mL are required
• Samples are solid powders that cannot be suspended
• Very high microbial counts (>10^9 CFU/g) are expected

Correct Answer: Preservatives in the sample may suppress colonies and volumes >1 mL are required

Q8. Endotoxin testing for herbal parenteral products is performed using:

• Plate count on Nutrient Agar
• Limulus Amebocyte Lysate (LAL) assay
• Sabouraud Dextrose Agar incubation
• Gram staining

Correct Answer: Limulus Amebocyte Lysate (LAL) assay

Q9. Which preservative efficacy test is commonly referenced for topical herbal formulations to evaluate antimicrobial preservation?

• USP <71> Sterility Test
• USP <51> Antimicrobial Effectiveness Test (Preservative Efficacy Test)
• WHO High-Risk Contamination Challenge
• Pharmacopeial Endotoxin Limit Test

Correct Answer: USP <51> Antimicrobial Effectiveness Test (Preservative Efficacy Test)

Q10. Which of the following water activity (aw) values is most likely to prevent growth of most bacteria and molds in dried herbal products?

• aw > 0.95
• aw ≈ 0.85
• aw < 0.70
• aw = 1.00

Correct Answer: aw < 0.70

Q11. For detection of Escherichia coli in herbal products, which selective/differential medium is most appropriate?

• SDA (Sabouraud Dextrose Agar)
• MacConkey Agar
• Tryptic Soy Agar
• Cetrimide Agar

Correct Answer: MacConkey Agar

Q12. Which mycotoxin is of greatest regulatory concern in many herbal products due to carcinogenicity and is commonly screened by HPLC or ELISA?

• Patulin
• Aflatoxin B1
• Ochratoxin A
• Deoxynivalenol

Correct Answer: Aflatoxin B1

Q13. A rapid method to detect viable bacteria that uses ATP bioluminescence primarily measures:

• Cell wall components unique to bacteria
• Total adenosine triphosphate (ATP) as an indicator of viable biomass
• RNA sequences of pathogens
• Endotoxin units in a sample

Correct Answer: Total adenosine triphosphate (ATP) as an indicator of viable biomass

Q14. Which procedure is essential before performing a microbiological assay on an herbal extract to avoid over- or underestimation of microbial counts?

• Direct plating without dilution
• Neutralization of antimicrobial components and proper serial dilution
• Heating the sample to 80°C for 10 minutes to kill microbes
• Filtering through 0.22 µm membrane to remove microbes

Correct Answer: Neutralization of antimicrobial components and proper serial dilution

Q15. Which of the following indicators is most appropriate to assess contamination by Pseudomonas aeruginosa in aqueous herbal formulations?

• Presence of lactose-fermenting colonies on MacConkey Agar
• Growth on Cetrimide agar selective for Pseudomonas
• Production of black colonies on Bismuth Sulfite Agar
• Yellow pigment on Mannitol Salt Agar

Correct Answer: Growth on Cetrimide agar selective for Pseudomonas

Q16. Good Agricultural and Collection Practices (GACP) reduce microbial contamination primarily by:

• Adding preservatives during cultivation
• Optimizing harvest time, drying, and preventing soil contact
• Sterilizing plant material with gamma radiation in the field
• Using antibiotics on crops to kill bacteria

Correct Answer: Optimizing harvest time, drying, and preventing soil contact

Q17. In a herbal product microbial risk assessment, the term “bioburden” refers to:

• The number of endotoxin units per mL
• The total viable microorganisms present on or in a product before sterilization
• The count of only pathogenic bacteria detected
• The concentration of preservatives in the formulation

Correct Answer: The total viable microorganisms present on or in a product before sterilization

Q18. Which of the following analytical approaches is best suited for rapid screening of multiple herbal samples for microbial contaminants in a quality control laboratory?

• Conventional plate count only
• Automated rapid systems (e.g., ATP bioluminescence, flow cytometry, or PCR-based assays)
• Visual inspection for mold
• Gram stain of undiluted sample

Correct Answer: Automated rapid systems (e.g., ATP bioluminescence, flow cytometry, or PCR-based assays)

Q19. When interpreting microbial limit test results for herbal powders, an observed colony count that is confluent on the first dilution plate generally indicates:

• Acceptable microbial load within limits
• That further serial dilutions are required to obtain countable plates
• Sterility of the sample
• Presence of only fungal contaminants

Correct Answer: That further serial dilutions are required to obtain countable plates

Q20. Which corrective action is most appropriate if a batch of herbal topical product fails preservative efficacy testing?

• Release the batch because microbial limits are secondary for topicals
• Reduce incubation times in micro testing to meet criteria
• Investigate formulation, re-evaluate preservative system, consider reformulation, and perform root cause analysis
• Dilute the batch with sterile water to lower counts

Correct Answer: Investigate formulation, re-evaluate preservative system, consider reformulation, and perform root cause analysis

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