Biochemical Test for Staphylococcus species
| taphylococcus Species | Biochemical Test | Reagents | Results |
|---|---|---|---|
| Staphylococcus aureus | Catalase Test | Hydrogen Peroxide | Positive: Bubbles observed |
| Coagulase Test | Rabbit Plasma | Positive: Clot formation | |
| Staphylococcus epidermidis | Catalase Test | Hydrogen Peroxide | Positive: Bubbles observed |
| Novobiocin Sensitivity | Novobiocin disk | Sensitive: Zone of inhibition | |
| Staphylococcus saprophyticus | Catalase Test | Hydrogen Peroxide | Positive: Bubbles observed |
| Novobiocin Sensitivity | Novobiocin disk | Resistant: No zone of inhibition | |
| Staphylococcus lugdunensis | Catalase Test | Hydrogen Peroxide | Positive: Bubbles observed |
| Novobiocin Sensitivity | Novobiocin disk | Variable: May show sensitivity or resistance | |
| Staphylococcus haemolyticus | Catalase Test | Hydrogen Peroxide | Positive: Bubbles observed |
| Novobiocin Sensitivity | Novobiocin disk | Resistant: No zone of inhibition | |
| Staphylococcus hominis | Catalase Test | Hydrogen Peroxide | Positive: Bubbles observed |
| Novobiocin Sensitivity | Novobiocin disk | Resistant: No zone of inhibition |
Differential diagnosis between different Staphylococci
| Biochemical Test | Staphylococcus aureus | Staphylococcus epidermidis | Staphylococcus saprophyticus |
|---|---|---|---|
| Gram Staining | Gram-positive cocci in clusters | Gram-positive cocci in clusters | Gram-positive cocci in clusters |
| Catalase Test | Positive | Positive | Positive |
| Coagulase Test | Positive | Negative | Negative |
| Mannitol Fermentation Test | Ferments mannitol | Does not ferment mannitol | Does not ferment mannitol |
| Novobiocin Sensitivity Test | Sensitive | Resistant | Resistant |
| Hemolysis on Blood Agar | Beta-hemolysis | Gamma-hemolysis | Gamma-hemolysis |
| DNAse Test | Positive | Negative | Negative |
| Tube Coagulase Test | Positive | Negative | Negative |
| Thermonuclease Test | Positive | Negative | Negative |
| Oxidase Test | Negative | Negative | Positive |
| Mannose Fermentation Test | Negative | Negative | Positive |
Biochemical Test for Streptococcus species
| Streptococci Group | Biochemical Test | Reagents | Results |
|---|---|---|---|
| Group A Streptococcus | Bacitracin Sensitivity | Bacitracin disk | Sensitive: Zone of inhibition |
| PYR Test | PYR Reagent | Positive: Development of red color | |
| Group B Streptococcus | CAMP Test | Staphylococcus aureus culture, blood agar plate | Positive: Enlargement of the zone of hemolysis at the intersection |
| of Group B Streptococcus and Staphylococcus aureus colonies | |||
| Hippurate Hydrolysis Test | Hippurate substrate | Positive: Development of a blue color | |
| Group D Streptococcus | Bile Esculin Test | Bile esculin agar, Ferric chloride | Positive: Blackening of the agar |
| Growth in 6.5% NaCl | NaCl broth | Positive: Growth in high salt concentration | |
| Viridans Streptococcus | Optochin Sensitivity | Optochin disk | Variable: Some species are sensitive (zone of inhibition), while others are resistant (no zone of inhibition) |
| Bile Solubility Test | Sodium deoxycholate solution | Positive: Complete lysis of the bile suspension | |
| Streptococcus pneumoniae | Optochin Sensitivity | Optochin disk | Sensitive: Zone of inhibition |
| Quellung Reaction | Specific antisera | Positive: Capsular swelling |
Differential Diagnosis of Streptococcus species
| Biochemical Test | Group A Streptococcus (Streptococcus pyogenes) | Group B Streptococcus (Streptococcus agalactiae) | Group C Streptococcus | Group D Streptococcus (Enterococcus faecalis) | Streptococcus pneumoniae | Viridans Group Streptococci |
|---|---|---|---|---|---|---|
| Gram Staining | Gram-positive cocci in chains | Gram-positive cocci in chains | Gram-positive cocci in chains | Gram-positive cocci in chains | Gram-positive lancet-shaped diplococci | Gram-positive cocci in chains |
| Catalase Test | Negative | Negative | Negative | Negative | Negative | Negative |
| Hemolysis on Blood Agar | Beta-hemolysis | Beta-hemolysis | Gamma-hemolysis | Gamma-hemolysis | Alpha-hemolysis | Variable (Alpha or gamma-hemolysis) |
| Bacitracin Sensitivity Test | Sensitive | Resistant | Resistant | Resistant | Resistant | Variable (Sensitive or resistant) |
| Hippurate Hydrolysis Test | Negative | Negative | Positive | Positive | Negative | Variable (Positive or negative) |
| CAMP Test | Negative | Negative | Positive | Negative | Negative | Variable (Positive or negative) |
| Esculin Hydrolysis Test | Negative | Positive | Negative | Negative | Negative | Variable (Positive or negative) |
| Optochin Sensitivity Test | Sensitive | Resistant | Resistant | Resistant | Sensitive | Variable (Sensitive or resistant) |
| Bile Solubility Test | Negative | Negative | Negative | Positive | Positive | Variable (Positive or negative) |
| PYR Test | Negative | Negative | Negative | Positive | Negative | Variable (Positive or negative) |
| Voges-Proskauer Test | Negative | Negative | Negative | Negative | Negative | Variable (Positive or negative) |
| Lancefield Serotyping | Group A antigen (Streptococcus pyogenes) | Group B antigen (Streptococcus agalactiae) | Group C antigen (Streptococcus equisimilis) | Not applicable | Not applicable | Not applicable |
Common Bacterial Pathogens and the biochemical test for identification
| Bacterial Pathogen | Biochemical Test | Typical Results |
|---|---|---|
| Escherichia coli | Indole Test | Positive: Development of a red color |
| Methyl Red Test | Positive: Stable red color after adding Methyl Red | |
| Voges-Proskauer Test | Negative: No color change or weak pink color | |
| Salmonella enterica | Citrate Utilization Test | Positive: Growth and color change in the medium |
| Urea Hydrolysis Test | Negative: No color change or yellow color | |
| Triple Sugar Iron (TSI) Agar Test | Acid slant/acid butt or alkaline slant/acid butt | |
| Staphylococcus aureus | Coagulase Test | Positive: Clot formation |
| Catalase Test | Positive: Bubbles observed | |
| Streptococcus pyogenes | Bacitracin Sensitivity | Sensitive: Zone of inhibition |
| PYR Test | Positive: Development of red color | |
| Pseudomonas aeruginosa | Oxidase Test | Positive: Development of a purple color |
| Nitrate Reduction Test | Positive: No color change after adding nitrate | |
| MacConkey Agar Test | Lactose non-fermenter (Colorless colonies) | |
| Klebsiella pneumoniae | Indole Test | Negative: No color change or yellow color |
| Citrate Utilization Test | Positive: Growth and color change in the medium | |
| Voges-Proskauer Test | Positive: Development of a red color | |
| Clostridium difficile | Lecithinase Test | Positive: Opalescence or white precipitate |
| Gram Stain | Gram-positive, spore-forming rods | |
| Neisseria gonorrhoeae | Oxidase Test | Positive: Development of a purple color |
| Glucose Fermentation Test | Positive: Acid production from glucose | |
| DNA Probe Test (NAAT) | Positive: Presence of specific DNA sequence | |
| Chlamydia trachomatis | Nucleic Acid Amplification Test (NAAT) | Positive: Amplification of Chlamydia DNA |
| Giemsa Stain | Identification of characteristic intracellular inclusions | |
| Cell Culture | Isolation and growth of Chlamydia organisms | |
| Haemophilus influenzae | X and V Factor Test | Positive: Growth with both X and V factors |
| Hemolysis Test | Non-hemolytic or gamma-hemolytic | |
| PCR for capsule typing | Positive: Amplification of specific capsule gene | |
| Legionella pneumophila | Legionella Urine Antigen Test | Positive: Detection of Legionella antigen in urine |
| Buffered Charcoal Yeast Extract (BCYE) Agar | Growth on BCYE agar | |
| Bordetella pertussis | Culture on Bordet-Gengou Agar | Isolation and growth of Bordetella pertussis |
| PCR for pertussis toxin gene | Positive: Amplification of pertussis toxin gene | |
| Mycobacterium tuberculosis | Acid-Fast Stain | Acid-fast bacilli seen under microscope |
| Culture on Lowenstein-Jensen or Middlebrook 7H10 agar | Growth on specific culture media | |
| Nucleic Acid Amplification Test (NAAT) | Positive: Amplification of M. tuberculosis DNA | |
| Vibrio cholerae | String Test | Positive: Formation of mucin-like stringy material |
| TCBS Agar Test | Yellow colonies on TCBS agar | |
| Serological Tests | Detection of specific cholera antigens | |
| Yersinia pestis | F1 Antigen Detection Test | Positive: Detection of F1 antigen |
| Bipolar Staining | Bipolar staining of bacteria under microscope | |
| PCR for Plasminogen Activator Gene | Positive: Amplification of plasminogen activator gene | |
| Enterococcus faecalis | Bile Esculin Test | Positive: Blackening of the agar |
| PYR Test | Positive: Development of red color | |
| Growth in 6.5% NaCl | Positive: Growth in high salt concentration | |
| Shigella spp. | Lysine Decarboxylase Test | Negative: No color change or yellow color |
| TSI Agar Test | Acid slant/acid butt or alkaline slant/acid butt | |
| PCR for Shiga Toxin Genes | Positive: Amplification of Shiga toxin genes | |
| Enterobacter aerogenes | Citrate Utilization Test | Positive: Growth and color change in the medium |
| Lactose Fermentation Test | Positive: Acid and gas production from lactose | |
| Stenotrophomonas maltophilia | Oxidase Test | Negative: No color change or weak pink color |
| Growth on MacConkey Agar | Non-lactose fermenter (Colorless colonies) | |
| Helicobacter pylori | Urease Test | Positive: Color change due to urease activity |
| Gram Stain | Gram-negative, curved or spiral-shaped rods | |
| PCR for specific H. pylori genes | Positive: Amplification of H. pylori genes | |
| Streptococcus pneumoniae | Optochin Sensitivity Test | Sensitive: Zone of inhibition |
| Quellung Reaction | Positive: Capsular swelling | |
| Bile Solubility Test | Positive: Complete lysis of the bile suspension | |
| Listeria monocytogenes | Catalase Test | Positive: Bubbles observed |
| Motility Test | Positive: Tumbling motility | |
| Christie-Atkins-Munch-Petersen (CAMP) Test | Positive: Enlargement of the zone of hemolysis | |
| Corynebacterium diphtheriae | Elek Test | Positive: Formation of a precipitin line |
| Tinsdale Agar Test | Black colonies on Tinsdale agar | |
| PCR for Diphtheria Toxin Gene | Positive: Amplification of diphtheria toxin gene | |
| Streptococcus agalactiae | CAMP Test | Positive: Enlargement of the zone of hemolysis |
| Hippurate Hydrolysis Test | Positive: Development of a blue color | |
| Growth in 6.5% NaCl | Positive: Growth in high salt concentration | |
| Proteus mirabilis | Indole Test | Positive: Development of a red color |
| Urease Test | Positive: Color change due to urease activity | |
| Swarming Motility Test | Positive: Spreading growth on agar surface | |
| Bacillus anthracis | Gamma Phage Lysis Test | Lysis of gamma phage-inoculated culture |
| Capsule Staining | Presence of a polypeptide capsule | |
| PCR for Protective Antigen Gene | Positive: Amplification of protective antigen gene | |
| Campylobacter jejuni | Oxidase Test | Positive: Development of a purple color |
| Hippurate Hydrolysis Test | Positive: Development of a purple color | |
| Growth at 42°C | Positive: Growth at elevated temperature | |
| Haemophilus ducreyi | PCR for H. ducreyi specific genes | Positive: Amplification of H. ducreyi genes |
| Culture on Chocolate Agar | Isolation and growth of H. ducreyi | |
| Gram Stain | Gram-negative, pleomorphic coccobacilli |