Revised list of suspected microorganisms:
1. S. aureus
2. S. pyrogenes
3. Clostridium perfringens
4. Clostridium botulinum
5. Pseudomonas aeruginosa
6. S. faecalis (enterococcus)
7.Proteus mirabilis
| Microorganism | Key characteristics | Lab diagnosis |
| S. aureus | Produce coagulase enzyme | Coagulase positive (agglutination) |
| Produce catalase | Catalase positive [Frothing when react with H2O2 ] | |
| Ferments mannitol | Yellow colonies on mannitol salt agar | |
| Lyses rbc | B haemolysis on BA | |
| B lactamase | B lactam resistant. Sensitivity to naficin, methicillin, vancomycin | |
|
| Gram positive (purple) cocci, “grape-like” | |
| S. pyogenes | Lyses rbc | B haemolysis on BA |
| Does not produce catalase | Catalase negative | |
|
| Bacitracin sensitive | |
|
| Hippurate and cAMP negative | |
|
| Gram positive cocci in chains | |
| C. perfringens | Double zone of haemolysis | B haemolysis on BA |
| Alpha lecithinase | Lecithinase positive on egg yolk agar | |
|
| Gram positive, large pink rods | |
|
| Proteolysis on CM (meat turn black) | |
| C. botulinum | Motile | Swarming effect on agar |
| Lipase positive |
| |
| Lecithinase and protease neg | Meat at the bottom of CM remain brown | |
|
| Gram positive, oval and subterminal spores, bacilli | |
| P. aeruginosa | Non fermentative | Pink colonies on macconkey agar |
| Oxidase positive |
| |
| Pyocyanin pigment | Blue on pseudomonas agar P | |
| Pyoverdin pigment | Fluorescein on Pseudomonas agar F | |
| Utilizes citrate | Citrate + (green to blue on citrate agar slant) | |
|
| Urease+/- | |
| Unable to hydrolyse and deaminate tryptophan | Indole - | |
| Does not utilize carbohydrates | TSI- | |
| S. faecalis | Non haemolytic | Gamma haemolysis on BA |
| Tolerant to 6.5% NaCl | Growth on mannitol salt agar | |
| Resistant to bile |
| |
| Hydrolyses esculin | Blackening of esculin agar | |
| Does not produce B lactamase | B lactam sensitive | |
|
| Gram positive cocci in chains | |
| P. mirabilis | Unable to metabolise lactose | Pink colonies on MAC |
| Distinct ordor |
| |
| Utilises urea and citrate | Citrate + | |
| H2S production | Black precipitate on TSI | |
| Unable to hydrolyse and deaminate tryptophan | Indole - | |
|
| Nitrogen reductase - | |
| Mixed acid fermentation | Methyl red + | |
| Unable to ferment glucose | Voges- Proskauer - | |
| Produce catalase | Catalase + | |
|
| Oxidase - | |
|
| Phenylalanine deaminase + |
Yeng Ting
Tg 02
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