Question

TYPE YOUR ANSWER

An unknown microbe with below result tests is identified Staphylococcus. ( to get to genus level). BASED ON RESULTS:

Discuss the degree of confidence you have regarding your identification (were there any tests that were challenging to interpret / what additional tests would confirm your identification/ Do all the characteristics of your microbe align with your observations?

EMB TEST	ACID & FERMENTATION WEAK
PEA	G+/ STAPHYLOCOCCUS
CATALASE	( +) HAVING CATALYST ENZYME
OXIDASE	(-)NO HAVING CYTOCHROME C OXIDASE
PHENOL RED	ACIDIC/ NO GAS PRODUCED
BREWER JAR	AEROBIC
MR/VP TEST	(-)(-) NO FERMENTATION /YELLOW COLLOR
NITRATE TEST	PARTIAL RED (+)
M.I.O	YELLOW - MOTILITY& ORNIHITIN ARE (-)
PEPTON IRON AGAR	(+) H2S PRODUCED

PHENYLALANINE TEST	YELLO COLOR(-)
STARCH	(-) NO PRODUCE AMYLASE ENZYME
SIMMONS CITRATE AGAR	(-) GREEN COLOR
UREASE TEST	YELLOW/ DON'T PRODUCE UREASE ENZYME
GELATINE TEST	LIQUID (+)
MANNITOL SALT AGAR	(+)/ SALT TOLERANT & A LITTLE FERMENTATION
MACcONKEY AGAR	G+/ NO GROWTH
BLOOD AGAR	BETA
KIRBY BAUER	SENSITIVE TO PENICILLIN (P10)

Answer 1

Additional tests for identification of Staphylococcus are as follows;

1. Gram staining - Since Staphylococcus is a gram positive strain, clear clusters can be visualised on the plate.

2. Blood agar with antibiotic - Confers antibiotic resistance.

Ex: Vancomycin, Novobiocin, Methicillin, Bacitracin

3. High salt tolerance test - Confers by pH change visualised in the form of color change. Positive for Mannose, Trehalose and negative for Raffinose.

4. Coagulase & Catalase test - Staphylococcus gives positive results. The coagulase test differentiates strains of Staphylococcus aureus from other coagulase-negative species.

5. It is an oxidative fermentative strain.

6. Enzymatic Reactions - Positive for enzymes like Arginine Dehydrolase, Hyalurodinase and negative for enzyme Ornithine Decarboxylase.

7. Milk agar - Milk protein casein is catalysed by the proteases secreted by Staphylococcus

8. Screening method for Staphylococcus aureus, to detect Bovine mastitis.

Characteristics:

1. Non spore forming bacteria.

2. Facultatively anaerobic.

3. Toxic in nature (especially food poisoning).

4. Protein A is a staphylococcal surface protein bound to peptidoglycan pentaglycine bridges.

5. Presence of Leukocidal toxins

6. Susceptibility to lysostaphin and lysozyme

7. Formation of grape like clusters

8. Contributes potential virulence.