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Why Do We Use a 90 mm Petri Dish in Microbiology? Scientific, Practical & Regulatory Reasons

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Why Do We Use a 90 mm Petri Dish in Microbiology? Scientific, Practical & Regulatory Reasons Why Do We Use a 90 mm Petri Dish in Microbiology? Scientific, Practical & Regulatory Reasons In microbiology laboratories worldwide—from academic research labs to pharmaceutical GMP cleanrooms—the 90 mm Petri dish has become the undisputed standard for microbial cultivation, enumeration, and environmental monitoring. But have you ever asked: Why not 80 mm or 100 mm? Why do USP, EP, and PDA methods implicitly assume 90 mm plates? Is the 90 mm dish scientifically superior or just historical? This article answers those questions in depth, covering scientific reasoning, statistical reliability, practical workflow advantages, and global regulatory expectations . 1. What Is a Petri Dish? A Petri dish is a shallow, circular, transparent laboratory container traditionally made of glass or polystyrene plastic. It is designed to hold solid or semi-solid culture...
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Why Are Microbiology Results Reported as less than 1 CFU Instead of 0 CFU Even When No Colonies Are Observed?

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Why Are Microbiology Results Reported as “<1 CFU” Instead of 0 CFU? Why Are Microbiology Results Reported as “<1 CFU” Instead of 0 CFU Even When No Colonies Are Observed? Introduction In pharmaceutical, biotechnology, medical device, and sterile manufacturing environments, microbiological testing is a critical quality control function. One question that frequently arises during routine testing, audit discussions, and regulatory inspections is: “If no microbial colonies are observed on a plate, filter, or media, why is the result reported as <1 CFU instead of 0 CFU?” This question is deceptively simple but deeply rooted in microbiological science, analytical limitations, statistical probability, and global regulatory expectations . The answer lies at the intersection of: Detection limits of microbiological methods Sampling uncertainty Statistical interpretation of absence of evidence Regulatory philosophy under :contentReference[oaicite:2]{inde...
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Why Does Autoclave Tape Turn Black? | Working Principle, Chemistry & GMP Significance

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Why Does Autoclave Tape Turn Black? Working Principle, Chemistry & GMP Significance Why Does Autoclave Tape Turn Black? Working Principle, Chemistry, Practical Examples & GMP Significance 1. Introduction Autoclave tape , also known as sterilization indicator tape, is one of the most commonly used tools in microbiology, pharmaceutical, and healthcare laboratories. One simple question is frequently asked by students, analysts, auditors, and inspectors: Why does autoclave tape turn black, and what does it actually prove? Although the color change appears simple, the science, regulatory meaning, and GMP interpretation behind autoclave tape are often misunderstood. 2. What Is Autoclave Tape? Autoclave tape is a Class 1 chemical indicator used during steam sterilization processes to visually indicate exposure to specific sterilization conditions. Also called: Steam indicator tape Category: Chemical indicator (not biological) Primary function: Process ...
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