A university student presents to their GP with irregular, pale patches on the upper chest and back. The GP observes multiple hypopigmented lesions (see image above) and collects a skin scraping for further testing.

i) What is the name of the disease affecting this patient? (1 mark)

ii) Which fungal organism is responsible for this condition? (1 mark)

You are tasked with characterising a novel virus linked to a disease outbreak. When co-cultured with host cells in vitro, the virus is continuously released from infected cells over a prolonged period without causing cell death. Is the virus likely to be naked or enveloped? Briefly justify your response. (1-2 sentences) (2 marks)

The human is an intermediate host for P. falciparum. Explain why P. falciparum does not sexually reproduce in human hosts despite the presence of both male and female gametocytes in human blood. (2-3 sentences) (2 marks)

A pregnant woman is exposed to cat faeces contaminated with Toxoplasma gondii. After ingestion, this protozoan invades host cells and multiplies within them. T. gondii depends on intracellular replication to complete its life cycle. Using the definitions provided in lecture four, would you classify T. gondii as a eukaryotic pathogen or a eukaryotic parasite? Briefly justify your response. (1–2 sentences) (2 marks)

Researchers develop a mutant strain of HIV for use in laboratory studies. The mutant virus can infect host cells and reverse transcribe its single stranded RNA genome, however the resulting dsDNA is not integrated into the host genome. Which viral enzyme is likely defective in the mutant virus? Briefly justify your response. (1-2 sentences) (2 marks)

A toxin produced by a gram positive bacterium is shown to non-specifically activate a large percentage of T cells by bridging MHC class II molecules and T cell receptors.

What type of toxin is this and what are the key immunological consequence of its activity? (1-2 sentences) (2 marks)

Researchers investigating Enterocidens muris, a novel mouse pathogen, observed that it invades intestinal epithelial cells by injecting effector proteins through a type III secretion system.

What mechanism does E. muris use to invade intestinal epithelial cells (zipper or trigger)? Briefly describe the mechanism in your response. (1-2 sentences) (2 marks)

Stenotrophomonas maltophilia is a bacterium that rarely causes disease in healthy individuals but can cause pneumonia or bloodstream infections in people undergoing chemotherapy.

Would you classify this bacterium as a primary or opportunistic pathogen? Briefly justify your response. (1-2 sentences) (2 marks)

A scientist is investigating an outbreak of a novel respiratory disease and consistently detects the same virus in nasal and throat samples collected from affected individuals. Unfortunately, Koch’s postulates could not be fulfilled, and the scientist was unable to determine if the virus was the causative agent of the respiratory disease.

Select one of Koch’s postulates and explain why it could not be fulfilled in this scenario. (2-3 sentences) (2 marks)

A healthy adult develops gastroenteritis after eating undercooked eggs at a restaurant. Analysis of a stool sample confirmed infection with Salmonella enterica, a pathogen not normally present in the human gut microbiota.

Would you classify S. enterica as an endogenous, exogenous and/or opportunistic pathogen? Briefly justify your response. (1-2 sentences) (2 marks)