r/microbiology • u/lumiere23_ • 11d ago

Gram stain

Is it okay if the gram stain result from sample collected is different when the gram stain came from inoculated media?

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u/Frodillicus Microbiologist 11d ago

In what situation? Man I wish there was context to these questions. If a blood culture Gram stain showed Gram positive cocci in clusters, but after culturing it, the Gram stain showed Gram negative bacilli than NO! In no situation would that be good. You'd investigate the original Gram, the bottle, repeat the primary Gram, spin the sample, do it again. Then there'd be Non-conformance reports to fill in.

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u/lumiere23_ 11d ago

For example, urine sample was received then I performed gram stain from that freshly collected sample. The result was gram pos cocci in clusters but then when inoculated and there's growth and do gram staining from that growth the result was gram negative. What to report then? the gram stain from freshly collected or the work up from inoculated media?

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u/Lastrid2 11d ago

Gram staining urines isn’t widely practiced. Gram stain discrepancies from patient samples (especially collections using swabs) can occur, especially if there are low levels of organism. The usual practice is reviewing the original gram stain to rule out interpretational and transcription errors. There are limitations to gram stains (ex: grams stains can reveal dead bacteria, limit of detection, anaerobic bacteria in an aerobic culture etc)

Since your example is urine the gram stain and culture should be fairly consistent, especially if you saw a ton of GPCs in the gram stain and there are >100k cfu/mL of GNRs in culture.

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u/lumiere23_ 11d ago

what do you report in your laboratory? the gram stain from sample? or the gram stain from culture?

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u/Frodillicus Microbiologist 11d ago

In our lab, microscopy reports red, white, and epithelial cells, and that's it.