Question

How might the ability to perform hemolysis benefit a hemolytic organism in its' natural environment? Imagine that you have a culture containing a single bacterial species. This culture may be one of several possible species. Describe a scenario where you use Mannitol Salt agar, Blood Agar, and EMB plates to identify the unknown bacterial species. That is, how would you use these plates to help you identify it?

Answer 1

Answer )

Hemolytic organism such as hemolytic bacteria are those which are able to produce the protein called hemolysin which leads to destruction of red blood cell and degradation of hemoglobin. In general term the hemolysis is majorily important for the hemolytic organism because the release of content from hemolysis specifically iron is used as nutrient source by these hemolytic pathogen. In other cases such as malaria babeiosis which is cause by Plasmodium and Babesia respectively replicate within RBC and rupture of RBC is essential for release of daughter parasite for completion of life cycle that is reinfection.

Answer )

Mannitol salt agar(MSA) :

It is used to identify the bacteria with having genus Staphylococcus. Mannitol salt agar conissit of high amount of salt concentration that is sodium cholride 7.5%. This high salt concentration allow the growth of only those bacteria which are highly tolerate to saline such as genus Staphylococcus. ALong with sodium chloride the mannitol salt agar also consist of sugar Mannitol which is fermented by bacteria producing acid. tThis acid then change the colour of phenol red into yellow which is present in MSA into yellow indicating the identification of  one of the clinical Staphylococcus known as Staphyloccocus aureus , while those bacteria which do not able to ferment mannitol then MSA remain red and these bacteria could be mark as non clinical Staphylococcus bacteria such as Staphyloccus epidermis.

Blood agar plates

It is used for the identification of fastidious and hemolytic bacteria. Blood agar plates media consist of generally tryptic soya agar along with 5% sheep blood. Bacteria which are hemolytic capability will able to produce protein called hemolysin. This hemolysin destruct the RBC present within the blood agar plate lead to clear zone indicating the presence of hemolytic bacteria and this is known as beta hemolysis as in case of Streptococcus aglalactiae. The other  cases is partial hemolysis that partial breakdown of RBC indicated by greenish colour and is known as alpha hemolysis as in case of Streptococcus dysgalactiae.

EOSIN METHYLENE BLUE AGAR (EMB)

It is used for the selection of gram negative bacteria and identification of lactose and non lactose fermenting enteric Bacilli. A s the name suggest it consisn of eosin and methylene blue . Methylene blue does not allow the growth of gram positive bacteria. The eosin methylene blue agar consist of lactose and sucrose.Both the dye that is eosin and methylene blue is an indicator of pH. The bacteria which ferment lactose producing acid leads to change in colour of colonies. the high lacotose fermenting bacteria indicated through deep purple colonies with green metallic sheen as in case of E. coli while low lactose fermenting bacteria are will be in brown pinkish in colour as in case of Klebsiella pneumoniae . Those which are non ferment will appear translucent within the plate example Pseudomonas aeruginosa.