Sunday, October 19, 2008

Week 17 SIP

Hi

This week its my turn to post a blogging post of my experience in my lab. For this week I am attached to my company’s satellite lab. A satellite lab is like an assistant towards the main lab handling samples collected from clinics. However a satellite lab is limited in terms of the number of test that can be done. This is due to a much smaller space to place adequate number of machines. Some machines that is used is also different from the main lab.

However I will be posting about a test, which I did in microbiology department, which I was posted into about 3 weeks ago. It is a routine test to detect the presence of gram-positive Staphylococcus aureus. Staphylococcus aureus is one of the most frequently encountered pathogens in clinical specimens. The rapid distinction between this species to other less virulent Staphylococci is very crucial and vital for an appropriate patient management. The test for the detection of free coagulase production permits the identification of staphylococcus aureus. The test reagent used is PASTOREX STAPH-PLUS to perform the coagulase test.

PASTOREX STAPH-PLUS is a rapid slide agglutination test for the simultaneous detection of the fibrinogen affinity, protein A and the capsular polysaccharides of Staphylococcus aureus.

The principle of PASTOREX STAPH-PLUS test reagent was designed to allow simultaneous detection of the following 3 components:

1 Fibrinogen affinity factor, also referred to as bound coagulase or “clumping factor”
2Protein A, which possesses an affinity for the crystallisable fragment(Fc) of gamma immunoglobumins (IgG).
3 Capsular polysaccharides of Staphylococcus aureus.

PASTOREX STAPH-PLUS reagent is made of latex particles sensitized by fibrinogen and IgG as well as specific monoclonal antibodies raised against capsular polysaccharides of Staphylococcus aureus. The combination of fibrinogen, IgG and anti-capsular monoclonal antibodies in the same reagent allows the recognition of highly encapsulated strains of Staphylococcus aureus as well as poorly encapsulated strains. For highly encapsulated strains, anti-capsular polysaccharides antibodies agglutinate the bacteria. For strains that have lost their polysaccharide capsule, the bacteria are agglutinated by fibrinogen and IgG.

Steps and procedures involved.
1 Place a drop of PASTOREX STAPH-PLUS
2 Inoculate a pure strain of bacteria colony from an agar plate and placed onto a clean glass slide.
3 Mix the reagent and the bacteria colony well
4 Observe for any agglutination. If there is agglutination, it means the bacteria colony is gram-positive Staphylococcus aureus.

Ivan Ng
TG01

10 comments:

tg01 group 2 said...

Hi Ivan

What must you do before using the PASTOREX STAPH-PLUS to distinquish gram-positive Staphylococcus aureus?

How do you prepare?

Thank you
Ernest
0606330i
week 17

MadTechs said...

Hi Ivan

I am highly interested in your post where you mentioned that there are strains of Staphylococcus aureus that are either highly encapsulated or poorly encapsulated.

Here's two questions:

1) Since they belong to the same strain, why is it that there is a difference in their encapsulation ratio?

2) What is the condition(s) where you would likely find highly and/or poorly encapsulated strains of Staphylococcus?

Many thanks
Quan Jun
TG02

PS: Do something about your tag-box, I don't know which joker wrote some offensive stuffs on it. You better remove it fast.

tg01 group 2 said...

Hi Ivan,

1) What agar plate does S. aurues grow on?

2)where do you place your a drop of PASTOREX STAPH-PLUS on? Glass slide?

3)If there is no agglutination, the species of S. aureus is gram-negative? Is it less virulent than the gram-positive one?

4)Why is detection of the fibrinogen affinity, protein A and the capsular polysaccharides of Staphylococcus aureus important? Are they the virulence factors of S. aureus?

5)Will there be any chance of false-positive result occurring?

Thankz!

Han Yang
TG01

De Incredibles said...

Hi Ivan,

How would the appearance of
1) agglutination of fibrinogen and IgG and
2) anti-capsular polysaccharides antibodies
look like?

Jean Leong TG02

hellomedtech said...

wow the test sounds really interesting. is this a common test done in a microbiology lab?? as in, every day will you receive samples that need to be carried out under this test?

Nurathirah
0606561I

tg01 group 2 said...

Hi ernest,

firstly u have to culture a swab of sample on to an appropriate culure agar plate(normally blood agar). then the next day inoculate a small colony of bacteria on to a glass slide and perform gram staining. pink means gram negative den purple/violet means gram positive. at the same time we can observe under the microscope for the morphology of the bacteria distinguishing between bacilli and coccus.den we will do the PASTOREX STAPH-PLUS coagulation test.

Ivan
0605070B
TG01

tg01 group 2 said...

Hi quan jun

bacteria strains have different species and mutations over time. furthermore bacteria that is found from different parts of the body will vary in terms of species. thus there is a certain degree of difference in the encapsulation ratio. lastly there is no specific area where we can find weak or highly ncapsulated strains of Staphylococcus. moreover PASTOREX STAPH-PLUS only identifies gram-positive Staphylococcus aureus. it doesnt distinguish the highly and weakly ncapsulated strains of Staphylococcus.

Ivan
0605070B
TG01

tg01 group 2 said...

Hi Jean Leong

In actual fact PASTOREX STAPH-PLUS doesnt act on fibrinogen and IgG and anti-capsular polysaccharides antibodies separately... its the overall reaction that makes an agglutination being visually observed. On the glass slide, thick white patches of agglutination will be observed if the bacteria colony is gram-positive Staphylococcus aureus.

Ivan
0605070B
TG01

tg01 group 2 said...

Hi Nurathirah

Yeah it is a routine test in microbiology, where by every bacteria colony that is identified as gram positive under gram staining. and classified as coccus under microscope, the lab tech will perform this test to determine if the bacteria colony is Staphylococcus aureus.

Ivan
0605070B
TG01

tg01 group 2 said...

Hi Han Yang,

We usually use sheep blood nutrient agar to culture the Staphylococcus aureus. Yeah, we will place a drop of PASTOREX STAPH-PLUS onto a glass slide. If there is no aggultination, it means that the bacteria colony does not come from Staphylococcus aureus family. No aggultination doesnt means gram negative, because we will do gram staining procedures 1st to identify the gram-staining identity den we do this test. after this test if there is no agglutination, we will do other test to further find out the identiy of the bacteria.

PASTOREX STAPH-PLUS is a chemical reagent used to react with specifically fibrinogen affinity, protein A and the capsular polysaccharides of Staphylococcus aureus. this is a special trait that only Staphylococcus aureus. it is not the virulent factor of the bacteria.

Every test has its own limitations. false positive results might occur if u take a bacteria colony which is not pure.

Ivan
0605070B
TG01