Pathogen Cheat Sheet
Clostridium Difficle
Clostridium difficile causes antibiotic associated diarrhoea
It is resistant to all antibiotics except metronidazole, vancomycin and fidaxomicin
It is an anaerobic spore former
Life cycle
o C. difficle spores ingested by patients
o Germination of spore in gut
o Asymptomatic carriage
o Alteration of gut flora
o Toxin release in diarrhoea
o Vegetative spores in faeces
o Environment contamination with spores
o Transmission through hands
Rickettsia
Life cycle
o Adult nymphs produce eggs
o Product larvae
o An infected human is a dead end host
MRSA
MRSA is a commensal bacteria found on the skin and nose
It is resistant to antibiotics and can cause septicaemia
Vibrio Cholerae
Gram negative curved rod
Toxin alters sodium pump in intestinal cells
Waterborne bacteria
Cholera outbreak of 1854
, o John Snows suspicion of water contamination
o Lead to development of germ theory
o Sickness correlated with broad street pump
E. Coli
Incubation period is 3-8 days
Causes bloody diarrhoea and abdominal cramps
Diagnosis by bacterium in faeces
o Can also be diagnosed by DNA fingerprinting and PFGE
Protozoa
Protozoa are unicellular microscopic eukaryotes
They are non-photosynthetic and mostly motile
They are heterotrophic meaning they
o Obtain energy from organic carbon
o Obtain carbon from organic carbon
They eat other unicellular organisms
Life cycle
o Trophozoites inside of hosts and undergo encystation into cysts outside of host
o These undergo excystation back into trophozoites
Protozoa are classified into
o Amoeba
Move by pseudopods
o Flagellates
Move by flagella
o Ciliates
Move by cilia
o Sporozoan
Actin-Myosin motor
Malaria
, Sporozoan Plasmodium spp.
Transmitted by anopheles mosquito
There are 5 species that cause malaria
o p. falciparum
o p. vivax
o p. ovale
o p. malariae
o p. knowlesi
Life cycle
o Mosquito injects sporozoites which travel to the liver
o These turn into merozoites
o They either turn into microgametocytes and macrogametocytes and go back into the
mosquito
o Or turn into trophozoites then schizont to produce more merozoites
Sporozoites bind with heparin sulphate proteoglycans of hepatocytes via circumsporozoite
protein
o They enter hepatocytes and schizogonic proliferation begins
Merozoites cause erythrocyte invasion by
o Parasite attaches to RBC via thrombospondin released adhesive protein
o Merozoites moves via gliding motility to re-orientate contact between rhoptry and
RBC
Plasmodium has an asexual blood stage
o Maurer’s clefts form and cause trophogony
o Schizogony turns them from immature to mature
o Merozoites and released and cause RBC invasion
Plasmodium secretes proteins into RBC cytosol which cause knob formation
o PfTRiC
o PfEMP
o MC
To avoid clearance from the spleen, infected RBCs bind with endothelial cells
o This causes platelet mediated clumping of infected erythrocytes
o Rosseting of infected and non-infected RBCs
Clostridium Difficle
Clostridium difficile causes antibiotic associated diarrhoea
It is resistant to all antibiotics except metronidazole, vancomycin and fidaxomicin
It is an anaerobic spore former
Life cycle
o C. difficle spores ingested by patients
o Germination of spore in gut
o Asymptomatic carriage
o Alteration of gut flora
o Toxin release in diarrhoea
o Vegetative spores in faeces
o Environment contamination with spores
o Transmission through hands
Rickettsia
Life cycle
o Adult nymphs produce eggs
o Product larvae
o An infected human is a dead end host
MRSA
MRSA is a commensal bacteria found on the skin and nose
It is resistant to antibiotics and can cause septicaemia
Vibrio Cholerae
Gram negative curved rod
Toxin alters sodium pump in intestinal cells
Waterborne bacteria
Cholera outbreak of 1854
, o John Snows suspicion of water contamination
o Lead to development of germ theory
o Sickness correlated with broad street pump
E. Coli
Incubation period is 3-8 days
Causes bloody diarrhoea and abdominal cramps
Diagnosis by bacterium in faeces
o Can also be diagnosed by DNA fingerprinting and PFGE
Protozoa
Protozoa are unicellular microscopic eukaryotes
They are non-photosynthetic and mostly motile
They are heterotrophic meaning they
o Obtain energy from organic carbon
o Obtain carbon from organic carbon
They eat other unicellular organisms
Life cycle
o Trophozoites inside of hosts and undergo encystation into cysts outside of host
o These undergo excystation back into trophozoites
Protozoa are classified into
o Amoeba
Move by pseudopods
o Flagellates
Move by flagella
o Ciliates
Move by cilia
o Sporozoan
Actin-Myosin motor
Malaria
, Sporozoan Plasmodium spp.
Transmitted by anopheles mosquito
There are 5 species that cause malaria
o p. falciparum
o p. vivax
o p. ovale
o p. malariae
o p. knowlesi
Life cycle
o Mosquito injects sporozoites which travel to the liver
o These turn into merozoites
o They either turn into microgametocytes and macrogametocytes and go back into the
mosquito
o Or turn into trophozoites then schizont to produce more merozoites
Sporozoites bind with heparin sulphate proteoglycans of hepatocytes via circumsporozoite
protein
o They enter hepatocytes and schizogonic proliferation begins
Merozoites cause erythrocyte invasion by
o Parasite attaches to RBC via thrombospondin released adhesive protein
o Merozoites moves via gliding motility to re-orientate contact between rhoptry and
RBC
Plasmodium has an asexual blood stage
o Maurer’s clefts form and cause trophogony
o Schizogony turns them from immature to mature
o Merozoites and released and cause RBC invasion
Plasmodium secretes proteins into RBC cytosol which cause knob formation
o PfTRiC
o PfEMP
o MC
To avoid clearance from the spleen, infected RBCs bind with endothelial cells
o This causes platelet mediated clumping of infected erythrocytes
o Rosseting of infected and non-infected RBCs
