Important Bacteria
Staphylococcus aureus: Coagulase +, catalase +, Gram + cocci in clusters. Causes: skin infections, pneumonia, endocarditis. Toxin: TSST-1.
Streptococcus pyogenes: Catalase -, bacitracin sensitive. Causes: pharyngitis, scarlet fever, rheumatic fever, glomerulonephritis.
Escherichia coli: Gram - rod, lactose fermenter. Causes: UTI (most common), gastroenteritis, neonatal meningitis.
Important Viruses
HIV: Retrovirus, RNA, reverse transcriptase. Targets CD4+ T cells. Progression to AIDS when CD4 < 200.
Hepatitis B: DNA virus, enveloped. Transmission: blood, sexual, perinatal. Chronic infection leads to cirrhosis and HCC.
Important Parasites
Plasmodium: Malaria. P. falciparum = most severe. P. vivax = relapsing malaria.
Entamoeba histolytica: Amoebic dysentery, liver abscess. Flask-shaped ulcers on histology.
Lab Diagnosis Methods
Gram staining, culture methods (aerobic/anaerobic), serology (ELISA, agglutination), PCR, antigen detection.
References & further reading
Every clinical claim in this article is anchored to a primary source. Click through to verify, and use the same habit in your revision.
Revision history
- 19 September 2026 — Initial publication
Frequently asked questions
What is the best microbiology textbook for exams?
Ananthanarayan and Panikers Textbook of Microbiology is the standard. Jawetz for medical microbiology. For parasitology: Chatterjeas Parasitology.
What microbiology topics are most important?
Bacterial pathogens (staph, strep, E. coli, Salmonella, H. pylori), viruses (HIV, Hepatitis, Herpes), parasites (Plasmodium, Entamoeba, Giardia), and clinical lab diagnosis methods.
How are microorganisms classified in UPSC CMS?
By Gram stain, morphology, culture requirements, disease caused, virulence factors, lab diagnosis, and treatment. Questions often combine 2-3 of these aspects in clinical vignettes.
Related reading
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