INFECTION AND IMMUNITY

This coursework is based initially on the case study below, and then includes additional aspects of food-borne disease and gastrointestinal pathogens.

Throughout, your answers must be based on cited evidence/literature. Where required, answers will need to contain microbiological details of infectious disease, including microbiological, cellular and molecular details of interactions between bacteria and host.

Where appropriate, answer lengths are based on single line spaced Times New Roman 12pt font, e.g. [½ page]. Please use this font size. Answers should be concise and precise, containing sufficient detail to ensure clarity. Remember that this item is the coursework for this module (50% of the module mark. See Module Guide for information. As a guide this assessment should require 24h-48h of student effort). Where required answers must be presented in the format given (e.g. hand-drawn graph, Excel graph, with all workings etc as stipulated).

Literature in addition to the module textbook will need to be consulted. Referencing: details of all reference sources must be correctly presented throughout the answer texts and at the end – and remember that you must not plagiarise. Do not copy word-for-word or quote from sources, but write using your own words.

Case study

A 35-year-old man had been feeling unwell for a few days with non-specific aches and pains in his joints and a slight headache. The following day he felt considerably worse, with severe colicky abdominal pain and he developed bloody diarrhoea, going to the lavatory 10 times in the day and persisting overnight. He then went to the accident and emergency department at hospital where he was admitted. Because he was dehydrated he was given intravenous rehydration and blood and faeces samples were sent for culture. Infection with Campylobacter jejuni was suspected as his history revealed that he had consumed a chicken mayonnaise sandwich which he thought was “a bit odd”. Some weeks later he began to develop weakness in his feet, which gradually spread to his legs and after more days the paralysis affected his leg muscles. With treatment, these symptoms gradually resolved.

Questions:

(Remember to use 12pt Times New Roman font, single line spaced)

1. What was the likely source of infection in this case study? What are the common sources of Campylobacter jejuni infection that lead to human infection? 1 mark [2-4 sentences]

2. Is disease produced by Campylobacter classified as a “food infection” or “food intoxication”? Explain your reasoning, including definitions of these terms. 2 marks [½ page]

3. Campylobacter spp and Salmonella spp (including a variety of serotypes) are relatively common in the UK. Using Public Health England data (you must use these to plot your own single graph in EXCEL™), compare the number of cases of these pathogens over 10 YEARS UP TO 2012. Summarise and discuss your comparisons as a series of succinct bullet points.

3 marks [Up to ⅔ page, including graph]

4. Give an account of Campylobacter pathogenesis and virulence factors, and use this knowledge to explain the initial symptoms of gastroenteritis disease (as described in the case study).

4 marks [1 page]

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5. Discuss long term consequences of Campylobacteriosis, particularly relating this to relevant symptoms described in the case study. 2 marks [½ page]

6. Briefly explain the routine laboratory techniques and tests (microscopy, bacterial culture – media and conditions and biochemical tests) used to isolate and identify Campylobacter. This section should contain descriptions and explanations of methods. 3 marks [½ page]

7. For each of the options below, state whether each statement is true or false and provide brief explanations/descriptions for every alternative to verify your true/false answers. (Marks will only be given if there are explanations).

C.jejuni can be typed:

(a) based on lipopolysaccharides

(b) using the Widal reaction.

(c) according to Lancefield’s grouping

(d) using ‘phage typing.

4 marks [A sentence or two for each statement]

8. Based on published literature, discuss two examples of types of ELISAs used in Campylobacter research/typing/identification, including whether they are direct or indirect ELISAs. 2 marks [½ page]

9. Several loci have been targeted for PCR-based identification of Campylobacter. Based on research literature, name these, describe what each encodes and discuss some applications of such molecular analysis in the identification of C.jejuni.

5 marks [1 page]

1. What antibiotic treatment may have been given to the patient in the case study? Briefly consider concerns about antibiotic resistance.

3 marks [½ page]

As part of the follow-up laboratory investigation it was decided to determine the heat sensitivity of Campylobacter by incubating bacteria at specific temperatures and performing viable counts by plating out suspensions onto blood agar.

Viable count results are given in Table 1 below:

(a) Process these Campylobacter data, and plot an appropriate graph to calculate the Decimal Reduction Times (D-values) for the three concentrations of disinfectant against the Campylobacter. The graph MUST BE HAND-DRAWN, plotted on standard graph paper, of sufficient size, with clear data points, AND lines showing how the D-values were determined must be clearly shown on the graph. YOU MUST SCAN in your hand-drawn graph into your WORD™ answer. You must show ALL your data processing clearly and logically, including how D-values were determined. [You will need to find out how to plot an appropriate graph and calculate the Decimal Reduction Times (D-values) for the three temperatures.]

6 marks

(b) Are these D-values consistent with published data? Comment and justify your answer.

2 marks [Short paragraph]

(c) Using the counts in the table, what percentages of the original suspension had been killed after 4min at 40°C and 50°C? Show all your calculations. 2 marks

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2. The administration of prophylactic antibiotics or probiotics to animals (including poultry) is an approach designed to reduce problems with bacterial pathogens but also for other reasons. Discuss scientifically the rationale and effectiveness of both of these two and implications for human health.

3 marks [⅔ page]

As well as a bacterial cause of human gastroenteritis it was also suggested, in this case, that rotavirus infection may have also been a possibility.

3. According to WHO protocols, in the laboratory, how would a faecal specimen be processed and stored prior to the actual testing for rotaviruses?

2 marks [⅓ page]

4. Examination of poultry in the flock that supplied the factory showed that some birds harboured rotavirus. Discuss the significance of this for human infection.

2 marks [up to ⅓ page]

References. Remember to use academically credible information sources. Reference your work throughout the text and list fully and correctly ALL the references you used to complete this work. They must be presented in the Coventry University Harvard format. Use the link from

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