gram_stainer
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Greetings,
I am an undergraduate advanced microbiology student and assist in our lower division micro course. The students have begun working in the lab, learning culturing and staining methods. My professor is perplexed regarding a matter, and frankly so am I - so I am hoping that perhaps someone on here can help us out...
I have two students who have apparently cultured and grown out motile, gram positive, beta hemolytic, aerobic rods. One student cultured the classroom doorknob, and one student cultured the hand pump on the soap dispenser from the restroom.
Can anyone give me any pointers on this? It doesn't look like contamination ...
Sorry - I'm new here, but this is a rather burning question at present, lol.
Thanks for any information - It will be much appreciated.
*Edit - I've actually got three students now who have these*
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| bactitech
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If they are hemolytic, motile rods, they are Bacillus sp. not anthracis. In clinical specimens that's all the farther we take the identification.
There are ways to speciate Bacillus, but you need specialized media. Bacillus sp. are from dirt. Looks like the doorknobs and hand dispensers need a cleaning :|
We have to further check out any NON-hemolytic gram positive rods to rule out B. anthracis. Motility will do that, but the motility of these rods is undulating, not darting, and sometimes it is difficult to see. If we are stumped, we send the organism off to the state labs for identification.
http://textbookofbacteriology.net/Bacillus.html
http://www.bt.cdc.gov/documents/PPTResponse/table...
The CDC site includes an ID table.
Have fun.
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Clinical Microbiology since 1974
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| Hazin477
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You said it was a "...grown out motile, gram positive, beta hemolytic, aerobic rods" that fits the profile of Listeria it is a non spore forming rod that has a tubling motility it is gram positive... as I understand it, it has a low virulence becuase it cuases enceph in neonates who lack Cell mediated Immunity... Hope this helps... I dont think its Baccilus becuase while the non-antrax bacillus is motile i dont think that its Beta Hemolytic
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| gram_stainer
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bactitech - Thank you very much for your response. We came to that conclusion after class was over. We are a small college, and I don't think we will be able to go any further on this. It actually looks like five students in all came up with the same thing - the growth is feathery on the blood agar ... Very interesting. When we did this last year, nothing like this came up, lol. Thanks again!
Hazin - Why do you believe it is Listeria? That wouldn't make much sense, would it? Listeria is a facultative anaerobe. Let me know your reasoning behind this .. Perhaps it will open up an interesting avenue of conversation, yes?
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| bactitech
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A doorknob would NOT grow Listeria. Take my word for it.
Yes, Listeria is a gram positive rod. I've only ever seen it in blood cultures and spinal fluid cultures. The colony is beta hemolytic, but it is small. It's a small rod - not large like a Bacillus. It is catalase positive. The colony morphology alone would rule out Listeria, as well as the site.
Check out that CDC chart, Hazin477. There are indeed hemolytic Bacillus sp. The colony is large at 24 hours on blood agar, and looks either like ground glass or produces hairy looking colonies, depending on the species. The colonies do not at all look like Listeria.
The two CSF's I've seen grow Listeria in my thirty years only produced a couple colonies on the plate each time. Every tech I've ever talked to that's seen or isolated Listeria always remembers it because it is so rare. It's an organism you always have to keep in the back of your head, because some day, when you least expect it, it will show up.
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Clinical Microbiology since 1974
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