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18 Cards in this Set

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SIM
S stands for sulfur ; I stands for indole ( an intermediate metabolite in the break down of sugar formed only by certain bacteria) and M stands for motility. This is a tube of agar.
Here we have three tests in one tube.
MOTILITY When the tube is inoculated with the loop a thin unseen trail remains in the agar where the “bugs” are - if they are motile the will move away from the site of inoculation to seek more food and the agar will become uniformly hazy( + for motility ); if they are not motile they will not be able to migrate from the site of inoculation and growth and turbidity will only at that site looking like a root hair or the trail a swimmer makes underwater after jumping from the high board(- for motility).
indole test
if done one adds a dropperful of chloroform + a dropperful of Kovac’s reagent. If indole is present the chloroform layer turns cherry red; if not it remains colorless.
Sulfur Test
SULFUR The sulfur test is important because only a few bugs do it - narrowing down your suspects. Some bugs use S instead of H to capture H2 in the metabolism of sugar producing H2S rather than H2O. H2S is the smell of ‘rotten eggs’. To spare your noses the manufacture adds iron to the tube:

Fe + H2S à FeS (black )
Therefore if there is any blackening of the tube it is positive for sulfur.
Urea Broth
3 ml. of yellow broth containing urea (a natural waste product of urine ). Some “bugs” eat it; some don’t -it’s another clue in the profile of our unknown organism.
O
NH2 - C - NH2 -----------à NH3 + CO2 + NH3
urea urease

We get by hydrolysis one CO2 which is acid and 2 NH3+ which are basic( NH3+ is ammonia). Hence the broth will be basic or alkaline. This is why standing urine begins to smell like ammonia. It is the action of certain bacteria having a meal and producing NH3+ as a waste product. Ammonia in the urea tube will cause the color to change from yellow à red. This is an important test since not many organisms that you can be tested on for your unknown do this. It immediately narrows the suspects to a few,for instance Proteus vulgaris.
Simmon’s Citrate
This is an agar slant. The tube is filled with liquid agar while it is hot and allowed to cool and then solidify with the tube held or placed at an angle thereby creating an inclined slope called the ‘slant’. The bottom of the tube is called the ‘butt’. The surface of the slant serves as sort of a mini agar plate for the growth of more air loving organisms and the butt serves for anaerobic growth. To inoculate a slant rug the slant with a loopful of inoculum and stab the loop all the way down into the butt. It is important to leave the cap on this tube loose for the reaction to take place. The agar in the control is moss green. If citrate is utilized by the bug there wil be a pH change and the agar will turn ‘Prussian blue’(cobalt blue)-a + reaction.








TSIA - Triple Sugar Iron Agar Slant
A TSIA tube has the same three sugars that the purple broth tube has only all in one tube. It also contains iron and therefore tests for H2S as did the SIM tube earlier. In essence it is a backup test and is really a combo of the purple broth + the Sulfur portin of SIM And should be interpreted in the same manner. Since this is agar,not broth we will detect gas production by looking for froth on the slant area, cracks in the agar and/or a space under the butt where the gas accumulated and literally pushed the agar off the bottom of the tube.

Litmus Milk
This is a liquid made of milk + the pH indicator litmus which is pink à red in acid and blue in base. The neutral control is sort of an opaque lavender solution. If the bugs eat or breakdown the milk acid is produced (turning the tube pink). The acid in turn precipitates the protein rennin in milk and it goes to the bottom of the tube as ‘curd.’ Some bugs produce alkali and it goes blue (this is rare). Occasionally there is a clear brownish ring at the top of the tube - this is peptonization and is just a further breakdown of the protein by acid( Pseudomonas sp. Sometimes does this). Typically the common reaction of the bugs we will use will be acid(pink) and curd.



AGAR PLATES

These are round plastic (petri) dishes filled with a layer of agar. There are many different types. We will use the following for our unknown.

Plain Tryptic-Soy Agar Plate(TSA) - Light translucent straw colored agar. Neither differential nor selective grows most anything as white to gray colonies. Its main purpose is to easily detect pigment produced by certain organisms, e.g. Pseudomonas (green) and Serratia (red). Other than that it has no great significance.

Plain Blood Plate - This is a bright blood red opaque plate. It is technically referred to as a Tryptic- Soy Agar plate with 5% Sheep Red Blood Cells. Do not confuse this plate with the TSA plate above. A plain blood plate is simply TSA agar to which Sheep Red Blood has been added. TSA alone is like gelatin; if I add tomato juice to it I now have ‘tomato aspic’ which is not the same thing as the plain gelatin.
This plate is differential; not selective.
It is differential because of the blood. Most bugs love blood as a food. However, some like it more than others and others don’t like it at all.
If a bug really loves blood he break it down completely leaving a clear transparent ring around the colony = Beta hemolysis.
If a bug is “so-so’ on eating blood he will only partially break it down leaving a greenish opaque ring around the colony = alpha hemolysis. The greenish color is due to biliverdin an intermediate breakdown
Product of blood that you will remember from A&P. This is what gives some bruises a greenish discoloration as they heal.
If the bug does not like blood he will not break it down(although he can live on other nutrients in the media sort of like the guest who survives on chips at the fish fest rather than eat fish which he does not like.
Here as you might expect there is no hemolysis; no zone of any kind of blood breakdown around the colony and ironically we refer to this as gamma hemolysis (or no hemolysis).
**Clinical implication -- beta hemolytic strep is bad and is treated aggressively with antibiotics because if he bugs like blood that much then they will find their way into the heart and blood vessels doing great harm. Alpha strep is part of the normal flora of the throat and is not treated; in fact a negative throat culture is alpha strep. It can be dangerous in post rheumatic fever patients and that is why penicillin is prescribed for those patients prior to any dental work.

Columbia CNA Blood Plate -- This is simply a plain blood plate that has (in addition to being differential) been made selective by the addition of two antibiotics, namely: Colistin and Nalidixic Acid. Hence the name CNA. These drugs inhibit the growth of gram - organisms so that the CNA blood plate selects only for the growth of gram + bugs. All the info about blood as a differential agent is the same. However, watch out for the fact that Pseudomonas aeruginosa would give you beta hemolysis on a plain blood plate, but not on a Columbia CNA blood plate. Why? Pseudomonas is gram - and cannot grow on CNA. If it can’t grow, it can’t eat the blood nor yield hemolysis.

Mac Conkey’s Plate -- This is a light transparent lavender plate. It is differential and selective.


It is selective because it contains crystal violet and bile salts which kill gram + bugs. Therefore, it selects for the growth of only gram - ones.
It is differential because it contains lactose. Bugs that utilize lactose form brightly colored colonies ( pink ,purple, purple with a green metallic sheen ,black ). Those that don’t use lactose form colorless colonies.
**Clinical implication - Salmonella & Shigella (both bad bugs )are non lactose fermentors vs. most normal intestinal flora which are in general lactose fermentors.

EMB (Eosin Methylene Blue ) - This is a dark brassy transparent purple plate. It is both differential & selective. The dyes which give the plate its name inhibit gram + bugs and so like MacConkey’s it grows only gram negatives. It is slightly more selective than MacConkey’s, yet it is differential in exactly the same way.






Mannitol Salt Agar - This is a transparent light pink plate that is both differential and selective.. It contains 6.5-7% NaCl which inhibits the growth of all other organisms except Staphylococcus . Therefore any growth on this plate is Staph. If that Staph does not use mannitol (a sugar alcohol) then the plate will remain pink. This is typical of Stap epidermidis. If the Staph uses the mannitol acid will be made, the pH will go down and the plate turns yellow. This is typical of Staph aureus.



OTHER MEDIA OF CLINICAL IMPORTANCE


Chocolate Agar -- Brown opaque plate. It is a blood plate that has been heated to break open the RBCs and release the heme. It is used for fastidious organisms that don’t grow well on regular blood, e.g. Neisseria gonorrhea, Neisseria meningitidis, Haemophilus influenzae b.

Thayer - Martin Agar - a selective chocolate agar for detection of G.C. (gonococcus ).

Lowenstein - Jensen Media - an oversized slant filled with an agar mage with glycerol and potato extract. It is a light mint green in color and is used or the growth of Mycobacteria such as T.B. The growth of T.B. takes 2-4 weeks and the growth which looks like stucco is termed ‘rough & buff’. Middlebrook media is also used for T.B.

Sabouraud Agar - used for fungal isolation


There are three other important tests: 1 Catalase test: certain organisms possess the enzyme catalase which can break H2O2 >>> H2O +O2. The test is easy to perform--take some of the culture and place it into a little H2O2 in a test tube the presence of bubbles indicates a + test, i.e. the organism has catalase; no bubbles = a - test. Staph and Listeria are +, while Strep and Leuconostoc are -. 2 Oxidase test: smear a litlle culture on specially prepared cards bought commercially --if the organism is oxidase + a purple color appears on the card. Two important organisms are +, Pseudomonas and Neisseria. 3. Coagulase test; some microbes produce this blood clooting enzyme add a .5cc of culture to .5 cc of citrated rabbit serum and observe after overnight incubation at 37 C. If the cc is solid then the organism is coagulase +, if it remains liquid it is -. Coagulase + organisms are more pathogenic. Staph is the usual microbe[Nursing implication: you will see these terms in patients charts eg Staph aureus coagulase + or -]
Course Documents






Course Documents


This is an agar slant. The tube is filled with liquid agar while it is hot and allowed to cool and then solidify with the tube held or placed at an angle thereby creating an inclined slope called the ‘slant’. The bottom of the tube is called the ‘butt’. The surface of the slant serves as sort of a mini agar plate for the growth of more air loving organisms and the butt serves for anaerobic growth. To inoculate a slant rug the slant with a loopful of inoculum and stab the loop all the way down into the butt. It is important to leave the cap on this tube loose for the reaction to take place. The agar in the control is moss green. If citrate is utilized by the bug there wil be a pH change and the agar will turn ‘Prussian blue’(cobalt blue)-a + reaction.








TSIA - Triple Sugar Iron Agar Slant
A TSIA tube has the same three sugars that the purple broth tube has only all in one tube. It also contains iron and therefore tests for H2S as did the SIM tube earlier. In essence it is a backup test and is really a combo of the purple broth + the Sulfur portin of SIM And should be interpreted in the same manner. Since this is agar,not broth we will detect gas production by looking for froth on the slant area, cracks in the agar and/or a space under the butt where the gas accumulated and literally pushed the agar off the bottom of the tube.

Litmus Milk
This is a liquid made of milk + the pH indicator litmus which is pink à red in acid and blue in base. The neutral control is sort of an opaque lavender solution. If the bugs eat or breakdown the milk acid is produced (turning the tube pink). The acid in turn precipitates the protein rennin in milk and it goes to the bottom of the tube as ‘curd.’ Some bugs produce alkali and it goes blue (this is rare). Occasionally there is a clear brownish ring at the top of the tube - this is peptonization and is just a further breakdown of the protein by acid( Pseudomonas sp. Sometimes does this). Typically the common reaction of the bugs we will use will be acid(pink) and curd.



AGAR PLATES

These are round plastic (petri) dishes filled with a layer of agar. There are many different types. We will use the following for our unknown.

Plain Tryptic-Soy Agar Plate(TSA) - Light translucent straw colored agar. Neither differential nor selective grows most anything as white to gray colonies. Its main purpose is to easily detect pigment produced by certain organisms, e.g. Pseudomonas (green) and Serratia (red). Other than that it has no great significance.

Plain Blood Plate - This is a bright blood red opaque plate. It is technically referred to as a Tryptic- Soy Agar plate with 5% Sheep Red Blood Cells. Do not confuse this plate with the TSA plate above. A plain blood plate is simply TSA agar to which Sheep Red Blood has been added. TSA alone is like gelatin; if I add tomato juice to it I now have ‘tomato aspic’ which is not the same thing as the plain gelatin.
This plate is differential; not selective.
It is differential because of the blood. Most bugs love blood as a food. However, some like it more than others and others don’t like it at all.
If a bug really loves blood he break it down completely leaving a clear transparent ring around the colony = Beta hemolysis.
If a bug is “so-so’ on eating blood he will only partially break it down leaving a greenish opaque ring around the colony = alpha hemolysis. The greenish color is due to biliverdin an intermediate breakdown
Product of blood that you will remember from A&P. This is what gives some bruises a greenish discoloration as they heal.
If the bug does not like blood he will not break it down(although he can live on other nutrients in the media sort of like the guest who survives on chips at the fish fest rather than eat fish which he does not like.
Here as you might expect there is no hemolysis; no zone of any kind of blood breakdown around the colony and ironically we refer to this as gamma hemolysis (or no hemolysis).
**Clinical implication -- beta hemolytic strep is bad and is treated aggressively with antibiotics because if he bugs like blood that much then they will find their way into the heart and blood vessels doing great harm. Alpha strep is part of the normal flora of the throat and is not treated; in fact a negative throat culture is alpha strep. It can be dangerous in post rheumatic fever patients and that is why penicillin is prescribed for those patients prior to any dental work.

Columbia CNA Blood Plate -- This is simply a plain blood plate that has (in addition to being differential) been made selective by the addition of two antibiotics, namely: Colistin and Nalidixic Acid. Hence the name CNA. These drugs inhibit the growth of gram - organisms so that the CNA blood plate selects only for the growth of gram + bugs. All the info about blood as a differential agent is the same. However, watch out for the fact that Pseudomonas aeruginosa would give you beta hemolysis on a plain blood plate, but not on a Columbia CNA blood plate. Why? Pseudomonas is gram - and cannot grow on CNA. If it can’t grow, it can’t eat the blood nor yield hemolysis.

Mac Conkey’s Plate -- This is a light transparent lavender plate. It is differential and selective.


It is selective because it contains crystal violet and bile salts which kill gram + bugs. Therefore, it selects for the growth of only gram - ones.
It is differential because it contains lactose. Bugs that utilize lactose form brightly colored colonies ( pink ,purple, purple with a green metallic sheen ,black ). Those that don’t use lactose form colorless colonies.
**Clinical implication - Salmonella & Shigella (both bad bugs )are non lactose fermentors vs. most normal intestinal flora which are in general lactose fermentors.

EMB (Eosin Methylene Blue ) - This is a dark brassy transparent purple plate. It is both differential & selective. The dyes which give the plate its name inhibit gram + bugs and so like MacConkey’s it grows only gram negatives. It is slightly more selective than MacConkey’s, yet it is differential in exactly the same way.






Mannitol Salt Agar - This is a transparent light pink plate that is both differential and selective.. It contains 6.5-7% NaCl which inhibits the growth of all other organisms except Staphylococcus . Therefore any growth on this plate is Staph. If that Staph does not use mannitol (a sugar alcohol) then the plate will remain pink. This is typical of Stap epidermidis. If the Staph uses the mannitol acid will be made, the pH will go down and the plate turns yellow. This is typical of Staph aureus.



OTHER MEDIA OF CLINICAL IMPORTANCE


Chocolate Agar -- Brown opaque plate. It is a blood plate that has been heated to break open the RBCs and release the heme. It is used for fastidious organisms that don’t grow well on regular blood, e.g. Neisseria gonorrhea, Neisseria meningitidis, Haemophilus influenzae b.

Thayer - Martin Agar - a selective chocolate agar for detection of G.C. (gonococcus ).

Lowenstein - Jensen Media - an oversized slant filled with an agar mage with glycerol and potato extract. It is a light mint green in color and is used or the growth of Mycobacteria such as T.B. The growth of T.B. takes 2-4 weeks and the growth which looks like stucco is termed ‘rough & buff’. Middlebrook media is also used for T.B.

Sabouraud Agar - used for fungal isolation


There are three other important tests: 1 Catalase test: certain organisms possess the enzyme catalase which can break H2O2 >>> H2O +O2. The test is easy to perform--take some of the culture and place it into a little H2O2 in a test tube the presence of bubbles indicates a + test, i.e. the organism has catalase; no bubbles = a - test. Staph and Listeria are +, while Strep and Leuconostoc are -. 2 Oxidase test: smear a litlle culture on specially prepared cards bought commercially --if the organism is oxidase + a purple color appears on the card. Two important organisms are +, Pseudomonas and Neisseria. 3. Coagulase test; some microbes produce this blood clooting enzyme add a .5cc of culture to .5 cc of citrated rabbit serum and observe after overnight incubation at 37 C. If the cc is solid then the organism is coagulase +, if it remains liquid it is -. Coagulase + organisms are more pathogenic. Staph is the usual microbe[Nursing implication: you will see these terms in patients charts eg Staph aureus coagulase + or -]
Course Documents






Course Documents



This is an agar slant. The tube is filled with liquid agar while it is hot and allowed to cool and then solidify with the tube held or placed at an angle thereby creating an inclined slope called the ‘slant’. The bottom of the tube is called the ‘butt’. The surface of the slant serves as sort of a mini agar plate for the growth of more air loving organisms and the butt serves for anaerobic growth. To inoculate a slant rug the slant with a loopful of inoculum and stab the loop all the way down into the butt. It is important to leave the cap on this tube loose for the reaction to take place. The agar in the control is moss green. If citrate is utilized by the bug there wil be a pH change and the agar will turn ‘Prussian blue’(cobalt blue)-a + reaction.








TSIA - Triple Sugar Iron Agar Slant
A TSIA tube has the same three sugars that the purple broth tube has only all in one tube. It also contains iron and therefore tests for H2S as did the SIM tube earlier. In essence it is a backup test and is really a combo of the purple broth + the Sulfur portin of SIM And should be interpreted in the same manner. Since this is agar,not broth we will detect gas production by looking for froth on the slant area, cracks in the agar and/or a space under the butt where the gas accumulated and literally pushed the agar off the bottom of the tube.

Litmus Milk
This is a liquid made of milk + the pH indicator litmus which is pink à red in acid and blue in base. The neutral control is sort of an opaque lavender solution. If the bugs eat or breakdown the milk acid is produced (turning the tube pink). The acid in turn precipitates the protein rennin in milk and it goes to the bottom of the tube as ‘curd.’ Some bugs produce alkali and it goes blue (this is rare). Occasionally there is a clear brownish ring at the top of the tube - this is peptonization and is just a further breakdown of the protein by acid( Pseudomonas sp. Sometimes does this). Typically the common reaction of the bugs we will use will be acid(pink) and curd.



AGAR PLATES

These are round plastic (petri) dishes filled with a layer of agar. There are many different types. We will use the following for our unknown.

Plain Tryptic-Soy Agar Plate(TSA) - Light translucent straw colored agar. Neither differential nor selective grows most anything as white to gray colonies. Its main purpose is to easily detect pigment produced by certain organisms, e.g. Pseudomonas (green) and Serratia (red). Other than that it has no great significance.

Plain Blood Plate - This is a bright blood red opaque plate. It is technically referred to as a Tryptic- Soy Agar plate with 5% Sheep Red Blood Cells. Do not confuse this plate with the TSA plate above. A plain blood plate is simply TSA agar to which Sheep Red Blood has been added. TSA alone is like gelatin; if I add tomato juice to it I now have ‘tomato aspic’ which is not the same thing as the plain gelatin.
This plate is differential; not selective.
It is differential because of the blood. Most bugs love blood as a food. However, some like it more than others and others don’t like it at all.
If a bug really loves blood he break it down completely leaving a clear transparent ring around the colony = Beta hemolysis.
If a bug is “so-so’ on eating blood he will only partially break it down leaving a greenish opaque ring around the colony = alpha hemolysis. The greenish color is due to biliverdin an intermediate breakdown
Product of blood that you will remember from A&P. This is what gives some bruises a greenish discoloration as they heal.
If the bug does not like blood he will not break it down(although he can live on other nutrients in the media sort of like the guest who survives on chips at the fish fest rather than eat fish which he does not like.
Here as you might expect there is no hemolysis; no zone of any kind of blood breakdown around the colony and ironically we refer to this as gamma hemolysis (or no hemolysis).
**Clinical implication -- beta hemolytic strep is bad and is treated aggressively with antibiotics because if he bugs like blood that much then they will find their way into the heart and blood vessels doing great harm. Alpha strep is part of the normal flora of the throat and is not treated; in fact a negative throat culture is alpha strep. It can be dangerous in post rheumatic fever patients and that is why penicillin is prescribed for those patients prior to any dental work.

Columbia CNA Blood Plate -- This is simply a plain blood plate that has (in addition to being differential) been made selective by the addition of two antibiotics, namely: Colistin and Nalidixic Acid. Hence the name CNA. These drugs inhibit the growth of gram - organisms so that the CNA blood plate selects only for the growth of gram + bugs. All the info about blood as a differential agent is the same. However, watch out for the fact that Pseudomonas aeruginosa would give you beta hemolysis on a plain blood plate, but not on a Columbia CNA blood plate. Why? Pseudomonas is gram - and cannot grow on CNA. If it can’t grow, it can’t eat the blood nor yield hemolysis.

Mac Conkey’s Plate -- This is a light transparent lavender plate. It is differential and selective.


It is selective because it contains crystal violet and bile salts which kill gram + bugs. Therefore, it selects for the growth of only gram - ones.
It is differential because it contains lactose. Bugs that utilize lactose form brightly colored colonies ( pink ,purple, purple with a green metallic sheen ,black ). Those that don’t use lactose form colorless colonies.
**Clinical implication - Salmonella & Shigella (both bad bugs )are non lactose fermentors vs. most normal intestinal flora which are in general lactose fermentors.

EMB (Eosin Methylene Blue ) - This is a dark brassy transparent purple plate. It is both differential & selective. The dyes which give the plate its name inhibit gram + bugs and so like MacConkey’s it grows only gram negatives. It is slightly more selective than MacConkey’s, yet it is differential in exactly the same way.






Mannitol Salt Agar - This is a transparent light pink plate that is both differential and selective.. It contains 6.5-7% NaCl which inhibits the growth of all other organisms except Staphylococcus . Therefore any growth on this plate is Staph. If that Staph does not use mannitol (a sugar alcohol) then the plate will remain pink. This is typical of Stap epidermidis. If the Staph uses the mannitol acid will be made, the pH will go down and the plate turns yellow. This is typical of Staph aureus.



OTHER MEDIA OF CLINICAL IMPORTANCE


Chocolate Agar -- Brown opaque plate. It is a blood plate that has been heated to break open the RBCs and release the heme. It is used for fastidious organisms that don’t grow well on regular blood, e.g. Neisseria gonorrhea, Neisseria meningitidis, Haemophilus influenzae b.

Thayer - Martin Agar - a selective chocolate agar for detection of G.C. (gonococcus ).

Lowenstein - Jensen Media - an oversized slant filled with an agar mage with glycerol and potato extract. It is a light mint green in color and is used or the growth of Mycobacteria such as T.B. The growth of T.B. takes 2-4 weeks and the growth which looks like stucco is termed ‘rough & buff’. Middlebrook media is also used for T.B.

Sabouraud Agar - used for fungal isolation


There are three other important tests: 1 Catalase test: certain organisms possess the enzyme catalase which can break H2O2 >>> H2O +O2. The test is easy to perform--take some of the culture and place it into a little H2O2 in a test tube the presence of bubbles indicates a + test, i.e. the organism has catalase; no bubbles = a - test. Staph and Listeria are +, while Strep and Leuconostoc are -. 2 Oxidase test: smear a litlle culture on specially prepared cards bought commercially --if the organism is oxidase + a purple color appears on the card. Two important organisms are +, Pseudomonas and Neisseria. 3. Coagulase test; some microbes produce this blood clooting enzyme add a .5cc of culture to .5 cc of citrated rabbit serum and observe after overnight incubation at 37 C. If the cc is solid then the organism is coagulase +, if it remains liquid it is -. Coagulase + organisms are more pathogenic. Staph is the usual microbe[Nursing implication: you will see these terms in patients charts eg Staph aureus coagulase + or -]
Course Documents






Course Documents






This is an agar slant. The tube is filled with liquid agar while it is hot and allowed to cool and then solidify with the tube held or placed at an angle thereby creating an inclined slope called the ‘slant’. The bottom of the tube is called the ‘butt’. The surface of the slant serves as sort of a mini agar plate for the growth of more air loving organisms and the butt serves for anaerobic growth. To inoculate a slant rug the slant with a loopful of inoculum and stab the loop all the way down into the butt. It is important to leave the cap on this tube loose for the reaction to take place. The agar in the control is moss green. If citrate is utilized by the bug there wil be a pH change and the agar will turn ‘Prussian blue’(cobalt blue)-a + reaction.
Litmus Milk
This is a liquid made of milk + the pH indicator litmus which is pink à red in acid and blue in base. The neutral control is sort of an opaque lavender solution. If the bugs eat or breakdown the milk acid is produced (turning the tube pink). The acid in turn precipitates the protein rennin in milk and it goes to the bottom of the tube as ‘curd.’ Some bugs produce alkali and it goes blue (this is rare). Occasionally there is a clear brownish ring at the top of the tube - this is peptonization and is just a further breakdown of the protein by acid( Pseudomonas sp. Sometimes does this). Typically the common reaction of the bugs we will use will be acid(pink) and curd.
AGAR PLATES
These are round plastic (petri) dishes filled with a layer of agar. There are many different types. We will use the following for our unknown.
Plain Tryptic-Soy Agar Plate(TSA)
Light translucent straw colored agar. Neither differential nor selective grows most anything as white to gray colonies. Its main purpose is to easily detect pigment produced by certain organisms, e.g. Pseudomonas (green) and Serratia (red). Other than that it has no great significance
Plain Blood Plate
This is a bright blood red opaque plate. It is technically referred to as a Tryptic- Soy Agar plate with 5% Sheep Red Blood Cells. Do not confuse this plate with the TSA plate above. A plain blood plate is simply TSA agar to which Sheep Red Blood has been added. TSA alone is like gelatin; if I add tomato juice to it I now have ‘tomato aspic’ which is not the same thing as the plain gelatin.
This plate is differential; not selective.
It is differential because of the blood. Most bugs love blood as a food. However, some like it more than others and others don’t like it at all.
If a bug really loves blood he break it down completely leaving a clear transparent ring around the colony = Beta hemolysis.
If a bug is “so-so’ on eating blood he will only partially break it down leaving a greenish opaque ring around the colony = alpha hemolysis. The greenish color is due to biliverdin an intermediate breakdown
What gives you greenish bruises?
Product of blood that you will remember from A&P. This is what gives some bruises a greenish discoloration as they heal.
If the bug does not like blood he will not break it down(although he can live on other nutrients in the media sort of like the guest who survives on chips at the fish fest rather than eat fish which he does not like.
What happens if no hemolysis
**Clinical implication -- beta hemolytic strep is bad and is treated aggressively with antibiotics because if he bugs like blood that much then they will find their way into the heart and blood vessels doing great harm. Alpha strep is part of the normal flora of the throat and is not treated; in fact a negative throat culture is alpha strep. It can be dangerous in post rheumatic fever patients and that is why penicillin is prescribed for those patients prior to any dental work
Columbia CNA Blood Plate
This is simply a plain blood plate that has (in addition to being differential) been made selective by the addition of two antibiotics, namely: Colistin and Nalidixic Acid. Hence the name CNA. These drugs inhibit the growth of gram - organisms so that the CNA blood plate selects only for the growth of gram + bugs. All the info about blood as a differential agent is the same. However, watch out for the fact that Pseudomonas aeruginosa would give you beta hemolysis on a plain blood plate, but not on a Columbia CNA blood plate. Why? Pseudomonas is gram - and cannot grow on CNA. If it can’t grow, it can’t eat the blood nor yield hemolysis.

Mac Conkey’s Plate -- This is a light transparent lavender plate. It is differential and selective.
EMB (Eosin Methylene Blue )
This is a dark brassy transparent purple plate. It is both differential & selective. The dyes which give the plate its name inhibit gram + bugs and so like MacConkey’s it grows only gram negatives. It is slightly more selective than MacConkey’s, yet it is differential in exactly the same way.
Mannitol Salt Agar
This is a transparent light pink plate that is both differential and selective.. It contains 6.5-7% NaCl which inhibits the growth of all other organisms except Staphylococcus . Therefore any growth on this plate is Staph. If that Staph does not use mannitol (a sugar alcohol) then the plate will remain pink. This is typical of Stap epidermidis. If the Staph uses the mannitol acid will be made, the pH will go down and the plate turns yellow. This is typical of Staph aureus.
Thayer - Martin Agar
a selective chocolate agar for detection of G.C. (gonococcus ).
Chocolate Agar --
Brown opaque plate. It is a blood plate that has been heated to break open the RBCs and release the heme. It is used for fastidious organisms that don’t grow well on regular blood, e.g. Neisseria gonorrhea, Neisseria meningitidis, Haemophilus influenzae b.
Lowenstein - Jensen Media
an oversized slant filled with an agar mage with glycerol and potato extract. It is a light mint green in color and is used or the growth of Mycobacteria such as T.B. The growth of T.B. takes 2-4 weeks and the growth which looks like stucco is termed ‘rough & buff’. Middlebrook media is also used for T.B.
Sabouraud Agar
used for fungal isolation