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Bactericide vs. bacteriostatic

Products acting in fighting bacteria are called antimicrobial and generally divided between bactericide, bacteriostatic and bacteriolytic. Despite the similarity among the names, definitions are directly related to these biocides mechanism of action.

A product is classified as bactericide When it causes the death of bacteria (in numbers up to about 99.99%), through mechanisms such as irreversible inhibition of DNA replication. Already classified as bacteriostatic products are those that inhibit the growth of bacteria in the middle, requiring external activation to eliminate them (task of the immune system in the presence of infectious organisms in the human body).

The bacteriolytic, in turn, in addition to killing the active bacteria by preventing the formation of the cell wall, also eliminate the already dead cells through a natural process called cell lysis – or disruption of the bacterial cell. Penicillin, for example, is classified as a bacteriolytic antimicrobial. Antimicrobials can be produced naturally by bacteria or fungi or they can be completely synthetic.

Defining an agent as bacteriostatic or bactericidal is not such a trivial task. As the maxim says, the "poison is in the dose". At concentrations high enough, agents typically classified as bacteriostatic can be potent enough to kill most bacteria when they are well concentrated - and are therefore considered to be bactericides.

Similarly, antibacterial products can be applied in low concentrations and act by inhibiting bacterial growth, instead of annihilating them, characterizing the behavior of a bacteriostatic. Thus, it is extremely important to choose the correct antimicrobial in the right dose, in order to optimize the most of the bacteria elimination process.

Antimicrobials in Hospital Environment

The study of antimicrobial agents has mainly advances in medical and hospital area. It is common in this context to classify antibacterial products, bacteriostatic or bacteriolytic as antiseptics, antibiotics or disinfectants.

Antiseptics are products that can be used in human or animal bodies (skin, mucosa, etc.) and act in living tissue to prevent infection, sepsis, or putrefaction. Antibiotics, in turn, are antibiotics used in the treatment and prevention of bacterial infections selectively.

Both antibiotics and antiseptics may take bactericidal or bacteriostatic functions. Already Disinfectants are antimicrobial chemicals applied on objects and surfaces in order to destroy microorganisms living in these objects.

The application of disinfectants on surfaces of hospitals and clinics is very important to prevent the transport of bacteria and infectious agents from one source to patients vulnerable to this type of contamination. For greater understanding of the severity of these cross-contamination, data presented by WHO show that one million of the 234 million patients operated worldwide each year die from hospital infections.

Meanwhile, the share of 7 million patients have postoperative complication frames. (Pan American Healh Organization, 2010.) In Brazil, the numbers are even more frightening. About 14% of patients contract hospital infections and 62% of patients hospitalized in ICUs (Intensive Care Units) have some type of infection – most common in delivery units.

Among the methods used to eliminate bacteria in hospitals cite the use of antimicrobial products commonly known as the alcohol gel for the sterilization of hands (hydrated ethanol), bleach (sodium hypochlorite) and hydrogen peroxide for disinfection of floors and appliances.

No longer so popular, you can mention products containing active with disinfectants and antibacterial properties such as Triclosan (antibacterial broad spectrum of action), quaternary salts and biguanide. However, the action of these assets is immediate, requiring continuous treatment for cleansing and disinfection to ensure a cross-contamination-free hospital environment.

What is the alternative?

Alternatively, the line treated with antimicrobial active materials (commonly silver nanoparticles) is a tendency to be maintained to ensure antimicrobial activity on the surface of these materials permanently.

Material present in areas of common access hospitals as plastics (rails, switches, stretchers, door handles etc.), ceramic (floor, walls, sanitary facilities), equipment (instruments, beds, elevator buttons) and textiles (towels, clothing bed, uniform) may receive treatment with the antimicrobial silver nanoparticles and ensure permanent efficacy against a range of pathogenic bacteria causing infections.

The effect of nanosilver is effective even in low dosages – precisely because of the geometric characteristic on a nano scale, which exponentially increases the active surface area of ​​the additive. The mechanism of action is similar to that of a bactericidal compound: it attacks the surface of the bacterium's cell membrane, penetrating the intracellular environment and preventing both bacterial respiration and DNA replication. Finally, when present inside the bacteria, the metal ions responsible for the final microbicidal effect are generated.

Article written by Alfonso Alborghetti Londero and Revised by João Carlos Carrion

additive bactericide