Microbial Infections

Question 1

What are viruses?

Answer 1

• Not cells in their own right
• Obligate parasites
• Contain RNA or DNA as genetic material
• Replicate using host-cell nuclear synthetic machinery
• Show host specificity
• But insect almost all other life forms, inducing bacteria
• Divide by budding out of hot cell, or cytolysis
• Various routes of infection
• Faceal-oral, airborne, insect vectors, blood borne

Question 2

Describe bacteria

Answer 2

• have no internal membranes: photosynthetic bacteria are an exception, eukaryotes have internal membranes that define organelles including nucleus, ER, mitochondria
• have a single copy of a chromosome (haploid): eukaryotes can be haploid or diploid
• cytoskeleton is poorly defined.
• eukaryotic cells have well developed cytoskeleton
• cell wall contains peptidoglycan
• determines shape (rod, coccus, spirochaete)
• basis of Gram stain
• divide by binary fission

Question 3

What is shigella?

Answer 3

an invasive pathogen
Shigella
species: infectious dose 10-100 bacteria, faecal oral transmission

Question 4

What is Neisseria Meningistis?

Answer 4

Neisseria Meningitis: commensal to pathogen

• Community acquired, multiple serogroups
• Rapid progression
• Septic shock
• Severe inflammatory response

Question 5

What is hospital acquired infection?

Answer 5

• Clostridium difficile
• Methicillin Resistant
• Staphylococcus aureus

Question 6

Describe TB

Answer 6

•New drugs to combat anti-microbial resistance and shorten treatment
•Better vaccines for adult population in high burden countries
•Better tools for early diagnosis
a) Conventional chest X-ray, with active pulmonary TB cavity right upper lobe (arrow)
b) High-resolution PET-CT scan using 18F-fluorodeoxyglucose (FDG) of thoracic cavity of person with bilateral TB. Orange depicts FDG uptake

Question 7

Describe mycobacterium leprae

Answer 7

Myobacterium leprae - leprosy 
•Chronic infection of the skin & nerves
•Transmitted by nasal discharges
•Low infectivity (cf. M. tuberculosis)
•Incubation period about 5 years

Question 8

Describe Fungi

Answer 8

• Eukaryotic
• cause cutaneous, mucosal and/or systemic mycoses
• occur as yeasts, filaments or both
• yeasts bud or divide; filaments (hyphae) which have cross walls or septa
• Candida albicans

Question 9

Describe protozoa

Answer 9

-Unicellular eukaryotic organisms
-include intestinal, blood and tissue parasites
-replicate in the host by binary fission or by formation of trophozoites inside a cell
asexual reproduction
-many have a complicated life cycle involving two hosts
-Infection is acquired by ingestion or through a vector
eg insect or invertebrate vector
-Malaria and Leishmaniasis

Question 10

Describe plasmodium species

Answer 10

Malaria:

• infection is acquired via a mosquito vector
• blood and tissue parasites
• formation of trophozoites inside a cell
• Sickle-cell and β-thalassaemia

Question 11

What is leishmania species?

Answer 11

Leishmaniasis:

• infection is acquired via a sandfly vector
• blood and tissue parasites
• formation of trophozoites inside a cell

Question 12

What is helminths?

Answer 12

• Metazoa with eukaryotic cells
• Multi-cellular; visible to the naked eye
• Life cycles outside the human host
• Roundworms e.g. Ascaris
• Flatworms (flukes)
• Tapeworms