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Difference between Staphylococcus and Micrococcus

Staphylococcus and Micrococcus both are Gram positive cocci (GPC).  Both of these cocci are non-motile, non-sporing and Catalase Positive.

Staphylococcus in Gram Stain

Both of these organisms are normal flora of skin and mucous membranes of man and animals. Member of the genus Staphylococcus are associated with clinical infections whereas that of Micrococcus are rarely involved in infection.

 

Some of the notable differences between Micrococcus and Staphylococcus are:

Characteristics /Tests Micrococcus Staphylococcus
Morphology Large Gram positive cocci, usually arranged in tetrads or in pairs. Gram positive cocci in clusters, sometimes in pairs and short chains.
Clinical Significance Usually considered contaminants of clinical specimen; rarely implicated as cause of infections.May cause opportunistic infection in an immunocompromised host. Bacteria of this genus are of primary clinical significance. S. aureus is a notorious pathogen. S. saprophyticus causes honeymoon cystitis.
Lysostaphin Sensitivity Test Not lysed with lysostaphin  (Resistant) Lysed with lysostaphin (Sensitive)
Furazolidone Sensitivity Test Resistant to antibiotic Furazolidone Susceptible to antibiotic Furazolidone
Bacitracin sensitivity test Susceptible to 0.04 U of Bacitracin Resistant to 0.04 U of Bacitracin
Microdase Test Microdase Positive Microdase Negative
Oxygen requirementsCarbohydrate Utilization They only grow aerobically (obligate aerobe)Utilize sugars oxidatively or not at all in the O/F test. Facultative anaerobic(can use either aerobic respiration and/or fermentation depending on the availability of oxygen, does not solely depend on aerobic respiration for growth).Fermentative

A.  Bacitracin Sensitivity

This test is used for the rapid identification of group A streptococci. It can be used to distinguish staphylococci (resistant) from micrococci (sensitive).

Method:

Result:

B. Lysostaphin Sensitivity

This test distinguishes staphylococci (sensitive) from micrococci (resistant).

Procedure and Result:

  1. Emulsify the test isolate in 2 ml phosphate buffered saline at pH 7.3 to concentration equivalent to McFarland’s opacity standard no. 1.
  2. Divide the suspension in to two portions. To one add a lysostaphin disc and shake vigorously. The other is the control.
  3. Incubate both portions in a water-bath at 37°C for 2 hour.
  4. Clearing of the test suspension relative to the control indicates sensitivity to lysostaphin.