Here’s a concise and complete list of important bacteria by Gram reaction and shape — suitable for MBBS-level microbiology:
🟣 GRAM POSITIVE COCCI
(Purple on Gram stain, spherical)
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Staphylococcus
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S. aureus
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S. epidermidis
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S. saprophyticus
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Streptococcus
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S. pyogenes (Group A)
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S. agalactiae (Group B)
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S. pneumoniae
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Viridans streptococci (S. mutans, S. sanguis)
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Enterococcus faecalis (Group D)
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🟣 GRAM POSITIVE BACILLI
(Purple rods)
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Spore-forming (Aerobes & Anaerobes)
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Bacillus anthracis
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Bacillus cereus
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Clostridium tetani
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Clostridium botulinum
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Clostridium perfringens
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Clostridium difficile
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Non-spore-forming
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Corynebacterium diphtheriae
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Listeria monocytogenes
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Lactobacillus
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Actinomyces israelii (filamentous)
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Nocardia (partially acid-fast, branching)
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🔴 GRAM NEGATIVE COCCI
(Pink spherical bacteria)
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Neisseria meningitidis
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Neisseria gonorrhoeae
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Moraxella catarrhalis
🔴 GRAM NEGATIVE BACILLI
(Pink rods)
Enterobacteriaceae Family
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Escherichia coli
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Klebsiella pneumoniae
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Enterobacter cloacae
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Proteus mirabilis
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Salmonella typhi
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Shigella dysenteriae
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Yersinia pestis
Others
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Pseudomonas aeruginosa
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Vibrio cholerae
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Campylobacter jejuni
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Helicobacter pylori
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Haemophilus influenzae (coccobacillus)
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Bordetella pertussis (coccobacillus)
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Brucella species (coccobacillus)
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Francisella tularensis (coccobacillus)
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Legionella pneumophila
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Bacteroides fragilis (anaerobic)
🟣🔴 GRAM VARIABLE or COCCOBACILLI (Intermediate forms)
Coccobacilli = short rods / oval
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Haemophilus influenzae (Gram-negative)
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Bordetella pertussis (Gram-negative)
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Brucella (Gram-negative)
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Francisella tularensis (Gram-negative)
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Acinetobacter baumannii (Gram-negative)
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Gardnerella vaginalis (Gram-variable)
📘 Quick Summary Table
| Category | Shape | Gram +ve | Gram –ve |
|---|---|---|---|
| Cocci | Round | Staphylococcus, Streptococcus, Enterococcus | Neisseria, Moraxella |
| Bacilli | Rod | Bacillus, Clostridium, Corynebacterium, Listeria | E. coli, Salmonella, Klebsiella, Pseudomonas |
| Coccobacilli | Short rod/oval | — (rare) | Haemophilus, Bordetella, Brucella, Francisella |
Would you like me to make this into a mnemonic chart (for rapid recall before exams)?
Perfect 👍— here’s a complete and MBBS-level list of important biochemical tests used in bacteriology for identification and differentiation of organisms.
I’ll organize them by broad categories (for easier memorization + exam writing).
🧪 I. BASIC BIOCHEMICAL TESTS
| Test | Principle / Purpose | Positive Result Example |
|---|---|---|
| Catalase test | Detects enzyme catalase (breaks H₂O₂ → H₂O + O₂) | Staphylococcus (+), Streptococcus (–) |
| Coagulase test | Detects enzyme coagulase (clots plasma) | Staph. aureus (+) |
| Oxidase test | Detects cytochrome oxidase enzyme | Pseudomonas, Neisseria (+) |
| Indole test | Detects ability to produce indole from tryptophan | E. coli (+), Klebsiella (–) |
| Methyl Red (MR) test | Detects mixed acid fermentation | E. coli (+) |
| Voges-Proskauer (VP) test | Detects acetoin production | Enterobacter, Klebsiella (+) |
| Citrate utilization test | Detects ability to use citrate as carbon source | Klebsiella, Enterobacter (+) |
| Urease test | Detects urease enzyme (urea → ammonia + CO₂) | Proteus, Klebsiella (+) |
| Nitrate reduction test | Detects nitrate → nitrite reduction | Enterobacteriaceae (+) |
| TSI (Triple Sugar Iron) agar test | Detects sugar fermentation (glucose, lactose, sucrose) and H₂S/gas production | Salmonella → alkaline slant/acid butt + H₂S |
| KIA (Kligler Iron Agar) | Similar to TSI but without sucrose | Same interpretation as TSI |
| H₂S production test | Detects hydrogen sulfide gas | Salmonella, Proteus (+) |
| Motility test | Detects bacterial motility | E. coli (+), Klebsiella (–) |
🔬 II. ENZYME & SPECIAL DIFFERENTIATION TESTS
| Test | Use / Organism differentiation |
|---|---|
| DNase test | S. aureus (+) vs S. epidermidis (–) |
| PYR test | S. pyogenes (+) and Enterococcus (+) |
| Bile esculin hydrolysis | Enterococcus, Group D Strep (+) |
| Optochin sensitivity | S. pneumoniae sensitive; Viridans Strep resistant |
| Bacitracin sensitivity | S. pyogenes sensitive; S. agalactiae resistant |
| Novobiocin sensitivity | S. epidermidis sensitive; S. saprophyticus resistant |
| NaCl tolerance (6.5%) | Enterococcus grows; Group D non-enterococci do not |
| Lecithinase test | Clostridium perfringens (+) |
| Nagler’s reaction | For Clostridium perfringens α-toxin detection |
| Reverse CAMP test | Clostridium perfringens identification |
| CAMP test | S. agalactiae (+) |
| String test | Vibrio cholerae (positive - mucoid string forms with NaOH) |
| Oxidation–Fermentation (O-F) test | To differentiate oxidizers vs fermenters (Pseudomonas = oxidizer) |
💧 III. SUGAR FERMENTATION TESTS
Used to differentiate Enterobacteriaceae and others.
| Sugar | Fermentation detected by |
|---|---|
| Glucose | Acid/gas production |
| Lactose | E. coli (+), Salmonella (–) |
| Sucrose | Vibrio cholerae (+), V. parahaemolyticus (–) |
| Mannitol | S. aureus (+), S. epidermidis (–) |
| Maltose | N. meningitidis (+), N. gonorrhoeae (–) |
🧫 IV. OTHER IMPORTANT TESTS
| Test | Purpose / Use |
|---|---|
| CAMP & Reverse CAMP | Group B Strep and Clostridium perfringens |
| Hanging drop motility | Vibrio (darting), E. coli (motile), Klebsiella (non-motile) |
| Satellite test | Haemophilus influenzae (requires V factor from S. aureus) |
| X and V factor requirement | Haemophilus identification |
| Oxidation-Fermentation (Hugh–Leifson medium) | Differentiate Pseudomonas vs Enterobacteriaceae |
| Tellurite reduction | Corynebacterium diphtheriae (black colonies) |
| Eleck’s gel precipitation test | Detects diphtheria toxin (immunodiffusion) |
| Carbohydrate fermentation with gas | Detects gas formation in Enterobacteriaceae |
| Gelatin hydrolysis | Proteus, Clostridium (+) |
🧠 V. SUMMARY MNEMONIC (for Enterobacteriaceae)
“IMViC = Indole, Methyl Red, Voges–Proskauer, Citrate”
| Organism | Indole | MR | VP | Citrate |
|---|---|---|---|---|
| E. coli | + | + | – | – |
| Klebsiella | – | – | + | + |
| Enterobacter | – | – | + | + |
| Proteus vulgaris | + | + | – | + |
| Salmonella | – | + | – | + |
Would you like me to make a visual summary chart (table + color-coded groups) for quick pre-exam revision? It helps a lot for Micro practicals.
Excellent 👏 Sabyasachi!
Here’s the complete MBBS-level list of culture media — organized clearly by type and use so you can memorize + recall easily for both theory and practicals.
🧫 CULTURE MEDIA – COMPLETE MBBS LIST
🩸 I. BASIC TYPES OF MEDIA (By Function)
| Type | Purpose | Examples |
|---|---|---|
| 1. Basal / Simple media | Support growth of non-fastidious bacteria | Nutrient agar, Nutrient broth, Peptone water |
| 2. Enriched media | Basal medium + nutrients like blood/serum for fastidious organisms | Blood agar, Chocolate agar, Loeffler’s serum slope |
| 3. Enrichment media | Liquid media that favor growth of one organism while inhibiting others | Selenite F broth (Salmonella), Alkaline peptone water (Vibrio), Tetrathionate broth |
| 4. Selective media | Contain inhibitors to suppress unwanted flora | MacConkey agar, DCA, XLD, TCBS, Lowenstein–Jensen, Tellurite medium |
| 5. Differential / Indicator media | Show color change / visual difference between species | MacConkey (lactose fermenters pink), Blood agar (hemolysis types), CLED agar |
| 6. Transport media | Maintain viability during transport | Stuart’s, Amies, Cary-Blair medium |
| 7. Anaerobic media | For anaerobes (contain reducing agents) | Robertson’s Cooked Meat broth (RCM), Thioglycollate broth |
| 8. Specialized media | For special organisms | Lowenstein-Jensen (Mycobacterium), TCBS (Vibrio), BCYE (Legionella) |
| 9. Indicator media | Color indicators to detect biochemical reactions | MacConkey, EMB, TSI |
🧪 II. IMPORTANT CULTURE MEDIA BY ORGANISM
🦠 A. Gram-Positive Cocci
| Organism | Media |
|---|---|
| Staphylococcus aureus | Nutrient agar, Blood agar (β-hemolytic), Mannitol salt agar (selective + differential) |
| Streptococcus pyogenes | Blood agar (β-hemolysis), Enriched media |
| S. pneumoniae | Blood agar (α-hemolysis), Chocolate agar (better growth), Bile solubility test medium |
| Enterococcus | Blood agar, Bile esculin agar (hydrolysis test) |
🦠 B. Gram-Positive Bacilli
| Organism | Media |
|---|---|
| Corynebacterium diphtheriae | Loeffler’s serum slope, Tellurite blood agar, Potassium tellurite medium |
| Bacillus anthracis | Nutrient agar (Medusa head colonies), Blood agar |
| Clostridium species | Robertson’s Cooked Meat broth (anaerobic), Blood agar (anaerobic jar) |
| Listeria monocytogenes | Blood agar (narrow β-hemolysis) |
🦠 C. Gram-Negative Cocci
| Organism | Media |
|---|---|
| Neisseria gonorrhoeae | Chocolate agar with 5–10% CO₂, Thayer-Martin medium (selective) |
| Neisseria meningitidis | Blood agar, Chocolate agar |
| Moraxella catarrhalis | Nutrient agar, Blood agar |
🦠 D. Gram-Negative Bacilli
| Organism | Media |
|---|---|
| E. coli, Klebsiella, Enterobacter | MacConkey agar (pink LF), EMB agar (E. coli – metallic sheen) |
| Salmonella, Shigella | DCA, XLD agar, SS agar, Selenite F broth (enrichment) |
| Proteus | Nutrient agar (swarming), MacConkey (pale NLF) |
| Pseudomonas aeruginosa | Nutrient agar (green pigment), Cetrimide agar (selective) |
| Vibrio cholerae | Alkaline peptone water (enrichment), TCBS agar (selective – yellow colonies) |
| Haemophilus influenzae | Chocolate agar (needs X & V factors), Satellite phenomenon on Blood agar |
| Bordetella pertussis | Bordet-Gengou agar, Regan-Lowe charcoal agar |
| Brucella species | Blood agar, Castaneda’s biphasic medium |
| Legionella pneumophila | BCYE agar (Buffered Charcoal Yeast Extract) |
| Yersinia pestis | Blood agar, MacConkey (pale colonies), Bipolar staining on smears |
| Helicobacter pylori | Skirrow’s medium (microaerophilic) |
| Campylobacter jejuni | Campy-BAP (microaerophilic, 42°C) |
🧫 E. Anaerobes
| Organism | Media |
|---|---|
| Clostridium species | Robertson’s Cooked Meat broth, Blood agar under anaerobic jar |
| Bacteroides fragilis | Blood agar with kanamycin + vancomycin (anaerobic) |
| Peptostreptococcus | Anaerobic blood agar |
🧫 F. Acid-Fast Bacilli
| Organism | Media |
|---|---|
| Mycobacterium tuberculosis | Lowenstein–Jensen medium, Middlebrook 7H10/7H11 agar |
| M. leprae | Cannot be cultured in vitro (only in footpad of mice or armadillo) |
🧫 G. Spirochetes
| Organism | Media |
|---|---|
| Leptospira | Fletcher’s, Stuart’s, EMJH (Ellinghausen–McCullough–Johnson–Harris) medium |
| Treponema pallidum | Not cultivable in vitro |
| Borrelia burgdorferi | Kelly’s medium (BSK – Barbour-Stoenner-Kelly) |
🧫 H. Mycoplasma
| Organism | Media |
|---|---|
| Mycoplasma pneumoniae | PPLO (Pleuropneumonia-like organism) agar / broth containing cholesterol |
🧫 I. Fungi
| Organism | Media |
|---|---|
| Candida albicans, Dermatophytes | Sabouraud’s Dextrose Agar (SDA) |
| Cryptococcus neoformans | SDA + Niger seed (Bird seed) agar → brown colonies |
| Histoplasma, Aspergillus | SDA, Brain-Heart Infusion agar |
🧫 J. Viruses (for reference)
| Use | Media / System |
|---|---|
| Virus isolation | Tissue culture, chick embryo, animal inoculation (not agar media) |
⚗️ III. SPECIAL PURPOSE MEDIA (Quick Revision)
| Medium | Use |
|---|---|
| MacConkey agar | Gram-negative enteric bacilli, lactose fermentation |
| Blood agar | Hemolysis, fastidious organisms |
| Chocolate agar | Neisseria, Haemophilus |
| Lowenstein–Jensen | Mycobacterium tuberculosis |
| TCBS | Vibrio cholerae |
| DCA / XLD / SS agar | Salmonella, Shigella |
| Bordet–Gengou / Regan–Lowe | Bordetella pertussis |
| Tellurite agar | Corynebacterium diphtheriae |
| BCYE | Legionella pneumophila |
| Sabouraud’s agar | Fungi |
| PPLO agar | Mycoplasma |
| Cetrimide agar | Pseudomonas aeruginosa |
| Campy-BAP | Campylobacter jejuni |
| Skirrow’s medium | Helicobacter pylori |
| Fletcher’s medium | Leptospira |
| Bile esculin agar | Enterococcus |
| Thayer–Martin agar | Neisseria gonorrhoeae |
| Loeffler’s slope | C. diphtheriae (metachromatic granules) |
| Selenite F broth | Salmonella enrichment |
Would you like me to make this into a 2-page “Culture Media Chart” (color-coded, ready to print) for your exam revision file?
It helps a lot for the practical table viva.
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