Sterilization and disinfection

Sterilization is the method that aims to eliminate all microorganisms, pathogenic and not (the bomb H is an excellent sterilant) while disinfection aims to eliminate pathogenic or potentially microbes, which is feared or presumed the presence in a substrate or environment, therefore the most suitable disinfectant will be chosen based on the pathogen our goal, at cost, the use that must be made of the objects to be disinfected.

Sterilization

Heat: heat is perhaps the best method of sterilization as it is effective against everything (I believe that even the pantegane die at 200 °), it is easily accessible and the required action times are reasonably short. Heat is used in two ways
– Dry heat: hot air (up to 200 °), bright flame (incineration, flanging of surfaces). Given the poor penetration of hot air and the possibility of “sanctuaries” higher temperatures and longer times are used compared to damp heat. However, even the spores of heat-resistant bacteria (which do not care, but are the things that more tenaciously resist heat) are eliminated in half an hour at 180 degrees. Maybe for a ML or an ED with plastic parts it’s not the best …
-Warm moisture: otherwise known as autoclave. Considering that the water boils at 100 °, the easiest way to raise this temperature is to increase the pressure, and this is what happens in an autoclave (but also in a pressure cooker). Usually, temperatures of around 120 ° for 10 minutes, at most 134 ° and two atmospheres in the case of very large coals in capacious autoclaves (the time and temperatures are lower because the wet heat penetrates better and reaches all the microscopic holes) . There are all types of autoclaves, in continuous cycle, single wall, double etc. Costs, at a glance, from a thousand euros to go up. Even here for a razor, maybe we are not …

Infrared rays: in stoves with normal or vacuum pressure, great penetration power, rather short action times. I do not know anything else about it, but I think it is used little in general

UV rays: at 2500 angstroms there is the highest sterilizing power, a very rapid action for degradation of the nucleic acids of the animals, but limited penetration of the exposed surfaces. They are used for the sterilization of large rooms, cabins etc … Low costs (I remember my former barber who put the irons in a “sterix” UV ray case was written on the cover)

Gamma rays: products from the cobalt 60 source are very effective against the monsters launched by Veg … sorry against the microbes. Joking aside, these methods are used to sterilize consumables (syringes, sutures) already sealed, and that for obvious reasons can not end up in the autoclave

Ethylene oxide: for all materials that would be altered by high temperatures and which must be thoroughly sterilized (such as catheters, transsophageal ultrasound probes, etc.). It is supplied in steel cylinders and becomes gaseous already at 10 °. It has an extreme penetration capacity and nothing resists it, however after use the instrumentation must be well ventilated to favor the removal of the residual gas as it can cause serious complications, even up to major bleeding (some materials must stay 15 days to “rest” after treatment)

Plasma gas: this is used against meganoids. Seriously, it is the expensive hydrogen peroxide subjected to fierce magnetic fields in order to obtain its weak and widespread ionization (better known as plasma status) and therefore free radicals. It is a very expensive method, but without disadvantages, it does not alter the materials and it is not dangerous for the operators dealing with these machines (there is no need of “rest” to remove the gas).

Disinfection

Physical and chemical agents are known. Physicists are very little used except in the home (the classic boiling for 5 minutes, which, taking place at lower temperatures of the autoclave and for shorter times, is here considered a disinfectant and not a sterilizing method).

Chemical disinfectants or biocides

In the past, substances such as strong acids or strong bases were used, which today find little use and only in certain rustic environments. Limited use also have some mercurial compounds or based on silver salts. Those that are most frequently brought up in dance belong to the following families:

Halogens: very diverse family, includes compounds based on chlorine, iodine, bromine. Chlorine is used either as a gas, or as an organic or inorganic compound (bioxides, chloramines, hypochlorites). A prime example is the amuchin based on sodium hypochlorite. Chlorine has an excellent disinfecting power against bacteria and viruses, with a marked propensity for the former, against which it is effective at low concentrations and very short times. The time for viruses is slightly longer. Some chloramines are sold as tablets for water purification. Gaseous chlorine is used for the disinfection of water. Chlorine exerts its action as it turns into hypochlorous acid in water.
Instead iodine is able to act already at the molecular stage. Its most common use is in the form of iodine tincture (an alcoholic solution) or Lugol’s liquid (iodine and potassium iodide in water), only in these cases there can be irritating action on the wounds, as well as dye on the skin . To reduce these effects, synthetic detergents are used conjugated with iodine to form substances called iodophores that if dispersed in the environment through atomizing devices allow the disinfection even in the presence of individuals without causing damage or discomfort.
The main limit to the effectiveness of such compounds based on chlorine or iodine is their effectiveness only against protein materials, microbes that do not owe their pathogenic action to surface proteins (for example the spores are not affected) resist.

Alcohols: ethyl and isopropyl alcohol is used, very effective against vegetative microorganisms, less against viruses. The effectiveness of pure alcohols is almost zero, while the maximum is in dilutions with water around 60%. 70% alcohol is used for the disinfection of skin and thermometers.

Aldehydes: in the past it was used formic aldehyde or formaldehyde, in gaseous form, to disinfect large environments. A prolonged aeration was necessary before reusing the rooms due to the irritating action. Today aldehydes are used in soapy solutions, such as lysoform, for floor cleaning. There are no notes on the relative effectiveness of the mirorganisms, but unless you want to dip your razor in Lysoform I do not mean it’s a lack.

Phenols: phenol was the first disinfectant used in surgical practice, now abandoned. We use compounds of phenic acid with the addition of alkalis or soaps, or the creoles or halogenated phenols with different elements in order to improve their efficacy on specific pathogens (exaclorophene effective against pathogenic streptococci). Therefore it is not possible to talk about the activity of the phenols as it varies greatly in the various compounds.

Synthetic detergents: they are considered non-ionic, anionic, cationic and amphoteric. The anionics and the non-ionic ones have little disinfecting power but strong foaming and disinfecting power (they are used in the production of detergents).
The cationics are represented by the quaternary ammonium compounds (Barbicide), and have strong power against the Gram + bacteria, reduced against Gram-, poor and variable against viruses, zero against tubercle bacilli and spores. They have the interesting feature of attaching themselves to the surfaces and forming a disinfectant film that remains even after treatment. Another advantage is that it is odorless and tasteless. The presence of organic substances or soaps can interfere with their bactericidal action.
Amphoters have excellent cleaning power and disinfectant power limited to Gram + and Gram- bacteria, they are ineffective against viruses, spores and fungi.

Chlorhexidine: excellent against Gram + bacteria, Gram-but useless against spores (and I think, but I’m not sure, against viruses). It is used in the disinfection of hands and wounds considering that protein compounds do not alter its effectiveness.

Hydrogen peroxide: this compound was not included among the topics covered in hygiene, so I had to do side-by-side research, which however had poor results. However it is an excellent disinfectant effective on many bacteria (except those with catalase) and on the spores of C. tetani. It is also effective on many viruses (although more precise I do not know at the moment). A characteristic that can reduce its usefulness is the need to conserve it in a suitable way (under penalty of the loss of excess hydrogen and the transformation into nothing of water) and the possibility of interactions with amino acids and enzymes that can reduce its effectiveness.