28 organisms.
One method.
You are not revising all of microbiology today. You are revising the 28 organisms that belong to immunology — the exact list is below — and you are doing each one the same way. That method is WRWRT.
Every other column in SystemWise Micro answers which bug infects this organ. Immunology answers which bug gets in when this defect exists. The organism is half the answer; the defect that let it in is the other half, and that is the half the exam is testing. So every organism below carries its defect. Learn them as pairs or you have learnt nothing.
If you have only ever used First Aid, you can revise every organism on this page from First Aid and the FA Guide alone. The list below is still your list; only the source changes. You will not fail for skipping Sketchy.
But if you have the time, invest in Sketchy — or whichever video resource is named against each organism. The whole point of a named resource is that somebody already worked out which one teaches that organism best, so you do not spend an evening sampling three of them. Sketchy is a memory palace; First Aid is a reference. If you can afford the hours, use both.
PART ONEThe WRWRT method
Five steps, in order, for every organism. The order is the whole point: each step only works because of the one before it.
Watch
1x speed. Full attention. No notes. Notes split your attention, and your brain cannot process the visual story and write at the same time. Just watch.
Why: the sketch is a memory palace. You are walking through a building, not collecting facts.
Recall
Close the video. Look away. Walk the whole story through chronologically, in your head — and say the defect out loud with it. Organism and defect, together, every time.
Why: this is the only step that builds retrieval. If it feels easy, you are recognising, not recalling.
Watch again
1.5x or 1.75x, and only the parts you could not recall — not the whole video again. Fill the gaps, then move on.
Why: rewatching what you already knew feels productive and teaches you nothing. Your failed recall just told you where to spend the time.
Read the PDF
Open the Sketchy Micro PDF for those organisms. Read it once.
Why: the exam asks in words, not pictures. This converts the image into sentences you can retrieve under a question stem.
Test
Finish with the FA Guide MCQs for those exact organisms — not the whole of Micro, just what you covered.
Why: if you cannot answer them, you watched — you did not learn. This is the only step that tells you the truth about the previous four.
The goal is not to master immunology microbiology today. It is to finish these 28 and move on. The learning happens when you meet them in a UWorld vignette weeks from now and the defect comes straight back with the organism.
PART TWOThe 28 immunology organisms
The entire immunology column of the SystemWise Micro chart, split the same way as every other column — and every organism carries the defect that let it in.
Bacteria · 14
Antibody defects & asplenia — encapsulated
- 01 Streptococcus pneumoniae — the classic: sepsis, meningitis, otitis
- 02 Haemophilus influenzae type B — no capsular antibody, no protection
- 03 Neisseria meningitidis — encapsulated — sepsis and meningitis
- 04 Klebsiella pneumoniae — encapsulated
- 05 Streptococcus agalactiae — Group B — encapsulated
- 06 Salmonella — encapsulated; osteomyelitis in sickle cell
- 07 Pseudomonas aeruginosa — encapsulated
Complement defects — C5–C9 / MAC
- 08 Neisseria meningitidis — recurrent meningococcaemia — the defining clue
- 09 Neisseria gonorrhoeae — disseminated gonococcal infection
Phagocyte defects — CGD, LAD, Chédiak-Higashi
- 10 Staphylococcus aureus — catalase-positive — abscesses, poor pus
- 11 Burkholderia cepacia — catalase-positive
- 12 Serratia marcescens — catalase-positive
- 13 Nocardia — catalase-positive
T-cell defects
- 14 Mycobacterium avium complex — disseminated when CD4 is very low
Viruses · 6
T-cell defects — DiGeorge, SCID, HIV
- 15 Cytomegalovirus (CMV) — retinitis, colitis, pneumonitis
- 16 Epstein–Barr virus (EBV) — lymphoproliferative disease
- 17 Varicella-zoster virus (VZV) — disseminated, not dermatomal
- 18 Herpes simplex virus (HSV) — severe, persistent, recurrent
Severe T-cell defects
- 19 JC virus — progressive multifocal leukoencephalopathy
Antibody defects
- 20 Enteroviruses — echovirus, poliovirus — chronic meningoencephalitis in Bruton's
Parasites · 3
T-cell defects
- 21 Toxoplasma gondii — ring-enhancing brain lesions
- 22 Cryptosporidium — chronic watery diarrhoea
IgA deficiency
- 23 Giardia lamblia — no secretory IgA on the gut surface
Fungi · 5
T-cell defects
- 24 Candida albicans — thrush, oesophagitis — mucocutaneous
- 25 Pneumocystis jirovecii — pneumonia below CD4 200
- 26 Cryptococcus neoformans — meningitis
Phagocyte defects — CGD
- 27 Aspergillus — invasive
- 28 Candida albicans — catalase-positive — invasive here, not mucosal
Neisseria meningitidis appears under both antibody defects and complement defects. Candida appears as mucocutaneous in T-cell defects and invasive in CGD. These are not duplicates — the organism is the same and the reason is different, and the reason is what the question turns on. Learn both readings.
PART THREEOne organism, worked through
WRWRT applied to the first organism on the list, in full, so you know exactly what each step looks like before you do it 27 more times.
Streptococcus pneumoniae
Watch the S. pneumoniae sketch, once, at 1x
Phone away. You are watching a story, and you will be asked to retell it in about four minutes.
Close it and retell the story out loud — then add the defect
You should be able to say, without looking
Gram stain and shape · that the capsule is the whole story · which defects lose capsular antibody — Bruton's, CVID, asplenia · why a splenectomised patient needs the vaccine · the three presentations it causes
Rewatch only the gaps
1.75x. Ninety seconds, not nine minutes. Then stop.
Read the S. pneumoniae pages of the Sketchy Micro PDF
Once, properly. Highlight only what you failed to recall a moment ago — those highlights are a precise map of where your memory breaks.
Do the FA Guide MCQs for S. pneumoniae
This organism only. Getting one wrong here costs two minutes and fixes the gap permanently; the same gap on test day costs you the mark.
That is one organism. Work down the list and immunology micro is finished. Do not go back to the chart. Do not start another system's organisms. Close this and move to your immunology First Aid reading.
Go to Immunology in the FA Guide Open the FA Guide → Microbiology The full SystemWise chart The SystemWise chart, searchable Back to my schedule