Let's Talk Micro

In this episode of Let's Talk Micro, we continue our gram-negative cocci series by focusing on what to do after the Gram stain. You've identified gram-negative cocci—now what?
We take a practical, bench-focused approach to working these organisms up, covering key culture media like blood agar, chocolate agar, and selective media such as Modified Thayer-Martin and Martin-Lewis. We also review collection and transport considerations, including JEMBEC and CO₂ requirements for Neisseria gonorrhoeae.
We then dive into commonly used tests, including ONPG for differentiating Neisseria lactamica and Neisseria meningitidis, the CTA test and its limitations, and the butyrate esterase test for identifying Moraxella catarrhalis.
This episode is all about building confidence at the bench—connecting what you see to what you do next.
 
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In this episode of Let's Talk Micro, we kick off a new series on gram-negative cocci by starting where it all begins—the Gram stain.
Seeing gram-negative diplococci on a smear can feel intimidating, especially when you're on the bench and need to make the right call. In this episode, we focus on how to approach that moment with confidence. We walk through the key organisms you'll encounter, including Neisseria, Moraxella, and Veillonella, and discuss how morphology, specimen source, and clinical context all come together to guide your thinking. We also revisit a correction from a previous episode regarding carbohydrate utilization in Neisseria species.
This episode is all about building a strong foundation—how to think before jumping to identification.
Stay tuned for the next episode, where we'll dive into the media and tests used to identify these organisms in the lab.
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The CLSI M100 gets updated every year—but what do those changes actually mean for the microbiology lab?
In this episode of Let's Talk Micro, Luis is joined by Dr. April Bobenchik to break down the latest updates in the CLSI M100 2026 (36th edition) and how they translate into real-world lab practice.
They walk through important breakpoint changes, including aztreonam–avibactam and updates for Acinetobacter, along with new additions like trimethoprim-sulfamethoxazole breakpoints for beta-hemolytic streptococci. Another notable update this year is the updated anaerobic antibiogram and how it can be used to help guide decisions in the lab. The conversation also touches on antimicrobial tiers, why some breakpoints are temporarily removed, and practical ways labs can approach implementing new updates.
If you work in clinical microbiology, this episode will help you stay current and confident with the latest M100 changes.
 
🔗 Resources
Access CLSI M100 for free: https://em100.edaptivedocs.net/Login.aspx
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Luis here with a quick update! We're taking a short break and will return the week of March 23rd. During this time, it's a great opportunity to explore the archive—Let's Talk Micro has over 200 episodes covering many topics in clinical microbiology. New episodes will be back soon. Thanks for listening and for being part of the Let's Talk Micro community.
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Wound cultures are some of the most complex specimens encountered in the clinical microbiology laboratory. Unlike more straightforward cultures, wound specimens often contain multiple organisms, making it challenging to determine which microbes are clinically significant and which represent colonization.
In this episode of Let's Talk Micro, Luis is joined by Dr. Christopher Doern and Dr. Alexandra Bryson to discuss the wound culture guidelines from the Clinical Microbiology Procedures Handbook (CMPH) and how they can help laboratorians navigate these challenging cultures.
Together, they explore practical approaches to interpreting polymicrobial wound cultures, deciding which organisms to work up, and balancing thorough reporting with antimicrobial stewardship. The discussion also covers specimen collection challenges, the role of Gram stains in evaluating specimen quality, guidance on working up common wound pathogens, and strategies to streamline laboratory workflows.
Whether you're a student, a new microbiology technologist, or an experienced laboratorian, this episode offers practical insights to help you confidently approach wound cultures and apply CMPH guidance at the bench.
 
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