5.3
Méthodes physiques de contrôle microbien : rayonnement et filtration
Le rayonnement et la filtration sont des outils essentiels de contrôle microbien, agissant selon des mécanismes distincts. Le rayonnement élimine les…
Les radiations tuent ou inhibent la croissance des micro-organismes.
Les armoires de sécurité utilisent des rayons UV non ionisants, qui endommagent l’ADN et désinfectent les surfaces, l’air et l’eau, mais leur pénétration limitée les empêche de désinfecter les articles en vrac comme les conserves.
Les rayonnements ionisants, tels que les rayons X et les rayons gamma, pénètrent profondément, détruisant les endospores, stérilisant les antibiotiques, les fournitures hospitalières et les aliments.
Le plasma froid, le quatrième état de la matière qui émet des rayons UV, est devenu un puissant agent antimicrobien utilisé pour stériliser les dispositifs médicaux et conserver les aliments.
La filtration élimine la plupart des microbes et est utilisée pour stériliser les liquides et les gaz sensibles à la chaleur.
Les filtres à membrane avec des pores de 0,2 μm, fabriqués à partir d’esters de cellulose ou de polymères plastiques, éliminent la plupart des microbes et stérilisent les milieux de culture, les vaccins et les antibiotiques.
Les filtres en profondeur, tels que les filtres HEPA utilisés dans les enceintes de sécurité, les salles d’opération et les unités de brûlage, piègent 99,97 % des particules, y compris les virus, dans leur matrice poreuse.
De même, les masques N95 bloquent 95 % des particules en suspension dans l’air au-dessus de 0,3 μm.
View the full transcript and gain access to JoVE Core videos
Q1: How does UV radiation kill microorganisms in safety cabinets?
UV radiation, a non-ionizing radiation type, is absorbed by microbial DNA, causing defects that kill or inhibit microorganisms. Safety cabinets use UV radiation to disinfect surfaces, air, and water effectively. However, UV radiation has limited penetration depth, making it unsuitable for sterilizing bulk items like canned foods.
Q2: What is the difference between ionizing and non-ionizing radiation for microbial control?
Non-ionizing UV radiation damages DNA but cannot penetrate thick layers, limiting its use to surfaces and air. Ionizing radiation, such as X-rays and gamma rays, penetrates deeply and destroys all microbes, including highly resistant endospores. This makes ionizing radiation ideal for sterilizing vaccines, antibiotics, hospital supplies, and food products.
Q3: Why is filtration preferred for sterilizing heat-sensitive liquids and antibiotics?
Filtration is a chemical-free method that removes microorganisms without applying heat or chemicals, making it ideal for heat-sensitive materials. Membrane filters with 0.2 μm pores, made of cellulose esters or plastic polymers, effectively remove most microbes from culture media, vaccines, and antibiotics while preserving their integrity.
Q4: How do HEPA filters and N95 masks protect against airborne microbes?
HEPA filters trap 99.97% of particles, including viruses, within their porous matrix through adsorption, making them critical for sterile environments in operating rooms and burn units. N95 masks block 95% of airborne particles larger than 0.3 μm, providing essential personal protection against microbial threats in healthcare and daily settings.
Q5: What is cold plasma and how does it sterilize medical devices?
Cold plasma is the fourth state of matter that emits UV rays and exhibits remarkable antimicrobial properties. It is increasingly used for sterilizing medical devices and preserving food, offering a versatile and effective solution for microbial control that complements traditional radiation and filtration methods.
Q6: Why can't UV radiation sterilize canned foods while gamma rays can?
UV radiation has limited penetration depth and cannot pass through thick layers or opaque materials like metal cans. Gamma rays, an ionizing radiation type with wavelengths shorter than 1 nm, penetrate deeply into objects and destroy all microbes, including endospores, making them effective for sterilizing packaged food products.
Q7: What pore size do membrane filters use to remove most microorganisms?
Membrane filters use pore sizes as small as 0.2 μm to effectively remove most microorganisms from liquids and gases. These filters, made from cellulose esters or plastic polymers, are widely used for sterilizing culture media, vaccines, and antibiotics, providing reliable microbial removal without damaging heat-sensitive materials.