General microbiology: bacterial morphology, staining, culture media
Microbiology · MBBS
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Study notes
A sputum smear shows red rods on blue — acid-fast bacilli, TB suspected. Ziehl-Neelsen staining exploits mycobacteria's waxy wall — carbol fuchsin resists acid-alcohol decolorization, so TB bacilli stay red against blue background. One smear takes minutes and diagnoses infectious TB — the reason DOTS programs screen millions this way. Culture (LJ medium, 6–8 weeks) or GeneXpert (hours, plus rifampicin resistance) confirms. The red rod is public health's most important color.
Related topics
- General microbiology: sterilization and disinfection, biomedical waste
- Bacteriology: gram-positive cocci — staphylococci, streptococci
- Bacteriology: gram-negative cocci, gram-positive bacilli
- Bacteriology: enterobacteriaceae — E. coli, salmonella, shigella, vibrio
- Bacteriology: mycobacteria — tuberculosis, leprosy
- Bacteriology: spirochetes, rickettsiae, chlamydiae, mycoplasma