Exam aid · Sciences

Microbiology & Vaccines

Stains, media, identification tests and Pakistan's routine immunisation schedule.

Tables to memorise

Cover the right-hand column and test yourself before checking.

Stain / medium	Use
Gram stain	Gram-positive purple; Gram-negative pink
Ziehl–Neelsen	Acid-fast bacilli (M. tuberculosis)
India ink	Cryptococcus capsule
Albert's stain	C. diphtheriae granules
MacConkey agar	Lactose fermenters (pink) vs non-fermenters
Blood agar	Haemolysis patterns
Chocolate agar	Haemophilus, Neisseria
Löwenstein–Jensen	M. tuberculosis (3–8 weeks)
TCBS	Vibrio cholerae (yellow colonies)
Sabouraud dextrose agar	Fungi

Test	Positive organism
Catalase	Staphylococci (not streptococci)
Coagulase	Staphylococcus aureus
Oxidase	Pseudomonas, Neisseria, Vibrio
Optochin / bile solubility	Streptococcus pneumoniae
Bacitracin sensitivity	Streptococcus pyogenes (group A)
Indole	Escherichia coli
Urease (rapid)	Proteus, H. pylori
Widal	Antibodies to Salmonella Typhi
GeneXpert MTB/RIF	TB DNA and rifampicin resistance

Age	Vaccines
Birth	BCG, OPV-0, Hepatitis B
6 weeks	OPV-1, Pentavalent-1, PCV-1, Rotavirus-1
10 weeks	OPV-2, Pentavalent-2, PCV-2, Rotavirus-2
14 weeks	OPV-3, Pentavalent-3, PCV-3, IPV-1
9 months	Measles–rubella (MR-1), typhoid conjugate vaccine, IPV-2
15 months	MR-2

Pentavalent = diphtheria, pertussis, tetanus, hepatitis B and Hib.
Live vaccines (BCG, OPV, MR, rotavirus) are avoided in severe immunosuppression.
Freezing damages aluminium-adjuvanted vaccines; check with the shake test.
A vaccine vial monitor shows heat exposure, not freezing.
IgG crosses the placenta; IgM is the first antibody in a primary response.

6–10–14: The three primary EPI visits for OPV, pentavalent and PCV are at 6, 10 and 14 weeks.

Attempt MCQs on these topics while the sheet is fresh. Anything you get wrong goes to your incorrect list for the next round.