Microbiology - questions asked

hihi.. sorry for the late reply. i didnt know the response was so overwhelming. hahaha..

please read on.... =)

to Jess

Question: does Salmonella appear black on all agar

No. it appear black only on XLD (Xylose lysine deoxycholate) plate.

Question: how does E.coli and Acinetobacter baumanii appears on the agar that differs from Salmonella

Both Salmonella and Acinebacter baumanii is non-lactose fermenter. Whereas E.coli is a lactose fermenter. Therefore Macconkey plate can be used to differentiate the lactose fermenter from the non-lactose fermenter. Inorder to differentiate the three different types of bacteria, perform biochemical test.

to Siewming

Question: what is Tip specimen

when patient with dextrose drip, central venous catheter, or any form of needle attaching to body, shows signs and symptoms of infection (eg. fever), blood FEME is usually done. when the blood FEME shows that there is bacteria growth or high amount of WBC present,

it means positive for infection. Hence it might be due to tip contamination, which is contamination of the needle or even the tubing. Thus, part of the tube is cut and send for comfirmation.

Question:is there a need to culture different type of stool on different type of agar plate.

Yes. different form of stool formed is due to different bacteria. Hence, with a standard protocol in the lab, different type of agar plate is used so to select and maximise the growth of the target bacteria.

to Jordan

Question: is it a must to streak on TSA plate then Macconkey plate for urine specimen.

Yes, Macconkey agar is a selective agar which may inhibit the growth of certain organism. thus if we streak on Macconkey agar first, we might transfer some of the nutrient in the Macconkey to the TSA plate which may inhibit the growth of certain organism. this may lead to inaccurate result as there might be more than 1 organism present.

to Jeremy

Question: what does XLD stands for and its uses in stool culture

XLD stands for Xylose Lysine Deoxycholate agar. Basically it is use to isolate Salmonella and Shigella.

Question: why does Hemophilus Influenza (HI) unable to grow on blood agar and is there any way to establish growth of HI on blood agar

HI does grow on blood agar only with the presence of Staphylococcus streak. this is bacause, Staphlococcus streak contains the X and V factor with enhance the growth of HI.

Question: what is the significance of detecting MRSA in people.

The only antibiotic that can treat MRSA is vancomycin. Given that vancomycin will damage the kidney function of neonates, it is very crucial.

to Lok Pui

Question: why do we need to do cell count for urine specimen

FEME is done to support the report. For instance if there is bacteria growth on the agar plate but there is no WBC observe under the microscope, it could be due to contamination of the agar plate. Hence urine FEME serves as a countercheck for the results.

Question: how to culture solidfy stool

Solid stool doe not undergo any dilution in broth. A stick is use to scrap abit of the stool, then it is smear on the agar plate.

Question: what kind of specimen is used for ear culture

For ear culture, ear swab is obtain.

(extra info: ear culture is done more commonly in newborn to screen for Group B Streptococcus that may be pass on from the mother.)

to Liyana

Question; how germ test is performed to confirm for Candida Albicans

In germ test, rich plasma is supplied. Only Candida Albicans is able to grow germ tube within 24 hours.

this is a picture of germ tubes of Candida Albicans

(adapted from http://en.wikipedia.org/wiki/Germ_tube)

to Janice

Question; do we use different plate for different form of stool

Yes, we do use different plate for different form of stool. (for more information, can refer to the post that i wrote)

Question: do we put ear specimen on cook meat

Nope. we only use CDC and Macconkey without salt agar plate.

Question; for Salmonella found on plate, how do we identify

we do a serotyping to confirm which group of Salmonella it belongs to. In this test, Salmonella Antisera is used. There is a total of 9 different group of Salmonella. In order to perform the serotyping, ensure that bacteria looks homogenous and no autolysis occurs. Next, one colony is treated with PO and PH, a bacteria antigen. PH is a test against flagella . Both PO and PH must be positive to ensure that the bacteria is a Salmonella species. Commercial reagent is then used to test for the group.

for those questions on the chat box, so sorry, i didnt realise there were questions over there. hence its not included in this post. will reply soon !! =)

bye bye..

JOCELYN =D