Question 1: Salmonella is a type of bacteria that causes food poisoning in humans. It infects the intestinal tract, leading to symptoms such as diarrhoea, fever, and abdominal cramps. Understanding its growth and infection mechanisms helps in controlling its spread.

Answer: Salmonella is a bacteria causing food poisoning, infects the intestines, leading to symptoms like diarrhoea and cramps.

Question 1: Define 'pathogen' and explain its relevance to Salmonella.

Answer: A pathogen is a microorganism that causes disease; Salmonella is a bacterial pathogen responsible for food poisoning.

Question 2: Describe the primary mode of transmission of Salmonella to humans.

Answer: Salmonella is primarily transmitted through contaminated food or water, especially raw or undercooked poultry and eggs.

Question 3: Explain why boiling food is an effective method to kill Salmonella bacteria.

Answer: Boiling food at 100°C destroys bacteria like Salmonella by denaturing their proteins and disrupting cell functions.

Question 1: If a sample contains 1,000 Salmonella bacteria and each bacterium divides every 30 minutes, how many bacteria will there be after 3 hours? Use the formula: N = N₀ × 2^(t / d), where N₀ = initial number, t = time in hours, d = doubling time in hours.

Answer: N = 1000 × 2^(3 / 0.5) = 1000 × 2^6 = 1000 × 64 = 64,000 bacteria.

Question 2: A contaminated water sample has a Salmonella concentration of 150 bacteria per millilitre. If a person drinks 250 ml of this water, how many bacteria are ingested? Express your answer in scientific notation.

Answer: Ingested bacteria = 150 bacteria/ml × 250 ml = 37,500 bacteria = 3.75 × 10^4 bacteria.

Question 1: Describe a safe procedure to isolate Salmonella bacteria from a contaminated food sample in the laboratory.

Answer: Use sterile techniques, wear protective gear, homogenise the sample, perform serial dilutions, plate on selective agar, and incubate at 37°C while following safety protocols.

Question 2: Identify two variables that need to be controlled during an experiment testing the effect of temperature on Salmonella growth.

Answer: Variables include the initial bacterial concentration and the incubation time.

Question 3: State two safety precautions that must be followed when handling Salmonella cultures.

Answer: Wear gloves and lab coats; sterilise all equipment after use.

Question 1: A study reports that after 8 hours of incubation at 37°C, Salmonella populations increased from 10^3 to 8 × 10^6 bacteria. Calculate the approximate doubling time of Salmonella under these conditions.

Answer: Number of doublings = log2 (8 × 10^6 / 10^3) = log2 (8 × 10^3) ≈ 12.98. Doubling time = 8 hours / 12.98 ≈ 0.616 hours or approximately 37 minutes.

Question 2: In a batch of poultry meat, Salmonella was detected at a concentration of 2 × 10^4 bacteria per gram. After applying a sanitation process, the bacteria count was reduced to 5 × 10^2 per gram. Calculate the log reduction achieved.

Answer: Log reduction = log10 (2 × 10^4) – log10 (5 × 10^2) = (4.30) – (2.70) = 1.60.

Question 1: Explain how understanding bacterial growth rates can inform public health policies regarding food safety regulations for poultry products.

Answer: Knowing growth rates helps set safe storage times and temperatures, determine appropriate cooking durations, and establish surveillance protocols to prevent outbreaks.

Question 2: Describe how new technology, such as rapid DNA sequencing, can improve detection and control of Salmonella outbreaks in the food industry.

Answer: Rapid DNA sequencing allows for quick identification of Salmonella strains, tracking sources of contamination, and implementing targeted control measures to prevent widespread outbreaks.