bactitech
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Topics: 25
Posts: 494
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Just a comment: I've seen many questions in this micro forum that seem like they're from back in the 70's. The question about EMB agar is one of them. On one of my micro lists, there was a recent discussion as to whether labs still used EMB. Only one out of at least 8-10 labs used it for primary plating instead of MacConkey. The one that did said they did because his boss (apparently an oldie like me) had used it for years (probably passed down from someone who trained in the 60's or before) and they felt comfortable with it. MacConkey is a much easier medium to use.
Is there anyone out there as a moderator who can comment on all the oldy moldy questions? There is so much that's NEW in micro, and the students who will be residents in just two years are going to be amazed at what they see in the real micro world when they get there.
What is your main source for these questions you post? Perhaps someone needs to check the latest microbiology "bible" which is the ASM Manual. I realize that doctors learn microbiology on a different level than we techs do, as they will never actually be reading out plates. It is a good idea, however, to keep up with some of the newer stuff out there.
Molecular testing is rapidly replacing culture for Chlamydia and GC in most large laboratories. Some really large labs are doing molecular testing on Staph. aureus isolates to check for MRSA. Also, many big centers do various PCR tests for various pathogens. I really don't know that much about all this stuff, except I know that it's coming and it's out there. There is much talk on the micro lists about setting up molecular testing. We just had an audioconference that went over basic reactions of common pathogens that can be done rapidly so that reports can be gotten out more quickly. One of the drawbacks of micro is that you're dealing with living organisms that can't be rushed. In chemistry you can plug some serum in an instrument and get a numerical result off the machine fairly quickly. In micro, the specimen must be planted, incubated, read out, possibly be subcultured, ID and sensis set up, more corroborative testing endured, etc. before a final answer is spit out. Because time is money and money is time, there are pushes in micro labs to streamline this chain of events as much as possible. The problem is that microbes are tricky; they don't always behave like you want them to behave. Molecular testing will totally change micro in the next 20-30 years, I predict. It's extremely expensive to start up, with reagents being outrageously priced. Also, the techs that are trained to do this stuff (I am NOT one of them) are hard to come by, as it is a new field.
Our lab recently started offering Enterovirus PCR testing on CSF. We are the only ones in the area offering this testing, and have reduced TAT for this test from one week (to a reference lab) to 24 hours locally. There are many other PCR tests being developed for critical CSF testing but they're not always available locally. Do you guys learn about this type of stuff, or are you stuck learning about EMB sheen when no one uses EMB any more?
Molecular testing is starting to be utilized to detect Group B streptococcus in pregnant women. We have used a special broth to isolate Group B strep for a long time, but this process can take 2-3 days. This new testing can be performed within a few hours, but not too many labs are doing it yet. As you know, or should know, Group B strep can cause meningitis in the neonate that is quite devastating to the newborn. Pregnant women that receive prenatal care are always tested for this during their last trimester with a vag/rectal swab. Our place has been talking about this new testing, but haven't instituted it yet.
Routine O&P examinations for patients who have not left the country should really have Giardia antigens performed first, as this is the most common parasitic isolate in the US. A good travel history MUST be obtained from the patient if an O&P is ordered and the lab notified by comment on the requisition if the patient has been out of the country, and to what country the patient has visited. Has Giardia antigen testing been discussed at all in any of your classes or references?
I see stool cultures ordered for O&P without a culture request when the stool is clearly diarrheic, mucoid, and bloody. A bloody stool can indicate Campylobacter, Shigella, E. coli 0157:H7 or Salmonella (more likely Shigella or EC 0157). Why do doctors order O&P's without cultures in these instances???? We had a stool the other night that was positive for WBC's and no culture was ever ordered. Don't you guys want to KNOW?
I'm just off on a rant here, as you can tell. My main wish is that, when faced with microbiological dilemma out in "the field" of patient care that you know both the past and the present of microbiology. I realize that these sometimes silly questions will come up on your tests, and that you have to know them. Microbiology is a fascinating and rapidly expanding field. Don't be afraid to ask questions of your ID doc mentors or your local friendly laboratory technologists. 
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Clinical Microbiology since 1974
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