Infection and Immunity

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:

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 …” 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]

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]

10.  What antibiotic treatment may have been given to the patient in the case study?
Briefly consider concerns about antibiotic resistance.
3 marks [½ page]

11.
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:

Table 1. The effect of temperature on Campylobacter jejuni

(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

12. 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 […” 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.
13.  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 […“ page]

14.  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 …“ page]