Question 1: Define Salmonella and describe how it infects humans.

Answer: Salmonella is a genus of bacteria that causes food poisoning. It infects humans primarily through contaminated food or water, entering the digestive system and multiplying, leading to symptoms like diarrhoea, fever, and abdominal cramps.

Question 2: Explain the mechanism by which Salmonella bacteria cause illness in the human gastrointestinal tract.

Answer: Salmonella bacteria invade the epithelial cells lining the intestines by attaching to the cell surface and inducing endocytosis. They then multiply within the cells, producing toxins that damage the intestinal lining. This results in inflammation, increased secretion of fluids, and symptoms such as diarrhoea and abdominal cramps.

Question 3: What is the primary mode of transmission of Salmonella?

Answer: The primary mode of transmission is through ingestion of contaminated food or water, especially raw or undercooked poultry, eggs, or unpasteurised dairy products.

Question 1: If a community experiences 150 cases of Salmonella in a month with a population of 30,000, calculate the incidence rate per 100,000 people.

Answer: Incidence rate = (Number of new cases / Population) x 100,000 = (150 / 30,000) x 100,000 = 500 cases per 100,000 people.

Question 2: A Salmonella outbreak results in 75 cases over 2 weeks. If the average duration of infection is 7 days per person, estimate the total number of person-days of infection during this outbreak.

Answer: Total person-days = Number of cases x Duration in days = 75 x 7 = 525 person-days.

Question 1: Describe a safe method to study Salmonella bacteria in a laboratory setting, including safety precautions to prevent infection.

Answer: A safe method involves working in a biosafety level 2 laboratory, wearing appropriate personal protective equipment (PPE) such as gloves and lab coats, sterilising equipment, and properly disposing of contaminated materials. Handwashing after handling bacteria and avoiding eating or drinking in the lab are essential safety precautions.

Question 1: In a survey of 200 food samples, 12 were found to be contaminated with Salmonella. Calculate the percentage of contaminated samples and interpret what this indicates about food safety in the surveyed area.

Answer: Percentage contaminated = (12 / 200) x 100 = 6%. This indicates a moderate level of contamination, suggesting the need for improved food hygiene practices to prevent outbreaks.

Question 2: A study reports that after implementing stricter hygiene measures, Salmonella cases decreased from 120 to 45 in a 3-month period within the same community. Calculate the percentage reduction in cases.

Answer: Percentage reduction = ((120 - 45) / 120) x 100 = (75 / 120) x 100 = 62.5% reduction.

Question 1: Explain how public health measures can reduce the spread of Salmonella. Include examples of strategies used to prevent infection.

Answer: Public health measures such as enforcing strict food hygiene standards, educating the public about safe food handling, ensuring proper cooking temperatures, and promoting handwashing can significantly reduce Salmonella transmission. Regular inspections of food outlets, vaccination programs where applicable, and rapid response to outbreaks are also vital in controlling the spread of infection.

Question 1: Discuss how advancements in food technology, such as pasteurisation and refrigeration, help prevent Salmonella infections in the food industry.

Answer: Pasteurisation involves heating food to a temperature that kills Salmonella bacteria, while refrigeration slows bacterial growth. These technologies enhance food safety by reducing the risk of infection from contaminated products, protecting public health, and maintaining consumer confidence.