Microbes & Infection Summary
Day 1
Introduction to medical microbiology;
Medical microbiology:
• Deals with the interaction of microorganisms and their human host
– Commensals > microbiome
– Pathogens > infectious diseases
SARS-CoV-2 causing COVID-19;
• Emerged in Nov 2019 in China
• Bats most probable origin > zoonosis
• By March 2021:
– ~ 120 million confirmed cases
– ~ 1.6 million deaths
Impact of infectious diseases in history: Plague, Smallpox, Spanish Flu.
,Top 10 global causes of deaths, 2016:
Total infectious diseases; 6 million > tuberculosis, diarhoeal diseases, lower respiratory infections.
In high income countries; relatively minor role. In low income countries; different situation; 5
infectious diseases in the top 10 of death.
Development of infectious diseases mortality;
Especially in low-income and lower-middle income countries; significant decrease in infectious
diseases.
,4 groups of pathogens (that cause infectious diseases):
-Viruses
-Bacteria
-Fungi
-Parasites; protozoa/worms
Viruses:
Size 18-750 nm, most < 200 nm
Structure DNA or RNA genome enclosed by protein shell +/- lipid membrane
Lifestyle ‘obligate cellular parasites’
Pathogenesis Direct damage by virus, immune reaction
Treatment Much improved in recent years but still limited
Prevention Vaccines, hygiene
Bacteria:
Fungi:
Size Usually 3-5 µm but can be larger
, Structure Eukaryotes; unicellular (yeast) or multicellular-filamentous
(molds)
Lifestyle Replicate by budding, fission and/or via spores
Pathogenesis Often opportunistic infections; immunopathology
Treatment Possible but difficult due to toxicity
Prevention Hygiene, good health
Parasites:
Size Highly variable: tiny protozoa (5 -10 µm) to large tapeworms (1 m)
Structure Eukaryotes; unicellular (protozoa) or multicellular (eg. worms)
Lifestyle Complex and highly variable
Pathogenesis Complex and highly variable; very high prevalence (2.5 billion infected)
Treatment Possible but difficult due to toxicity
Prevention Hygiene, prophylaxis (malaria)
Pathogen <> Disease
Day 1
Introduction to medical microbiology;
Medical microbiology:
• Deals with the interaction of microorganisms and their human host
– Commensals > microbiome
– Pathogens > infectious diseases
SARS-CoV-2 causing COVID-19;
• Emerged in Nov 2019 in China
• Bats most probable origin > zoonosis
• By March 2021:
– ~ 120 million confirmed cases
– ~ 1.6 million deaths
Impact of infectious diseases in history: Plague, Smallpox, Spanish Flu.
,Top 10 global causes of deaths, 2016:
Total infectious diseases; 6 million > tuberculosis, diarhoeal diseases, lower respiratory infections.
In high income countries; relatively minor role. In low income countries; different situation; 5
infectious diseases in the top 10 of death.
Development of infectious diseases mortality;
Especially in low-income and lower-middle income countries; significant decrease in infectious
diseases.
,4 groups of pathogens (that cause infectious diseases):
-Viruses
-Bacteria
-Fungi
-Parasites; protozoa/worms
Viruses:
Size 18-750 nm, most < 200 nm
Structure DNA or RNA genome enclosed by protein shell +/- lipid membrane
Lifestyle ‘obligate cellular parasites’
Pathogenesis Direct damage by virus, immune reaction
Treatment Much improved in recent years but still limited
Prevention Vaccines, hygiene
Bacteria:
Fungi:
Size Usually 3-5 µm but can be larger
, Structure Eukaryotes; unicellular (yeast) or multicellular-filamentous
(molds)
Lifestyle Replicate by budding, fission and/or via spores
Pathogenesis Often opportunistic infections; immunopathology
Treatment Possible but difficult due to toxicity
Prevention Hygiene, good health
Parasites:
Size Highly variable: tiny protozoa (5 -10 µm) to large tapeworms (1 m)
Structure Eukaryotes; unicellular (protozoa) or multicellular (eg. worms)
Lifestyle Complex and highly variable
Pathogenesis Complex and highly variable; very high prevalence (2.5 billion infected)
Treatment Possible but difficult due to toxicity
Prevention Hygiene, prophylaxis (malaria)
Pathogen <> Disease
