Overuse of disinfectants is putting us at risk of illness


Some babies may be the first cases of a local disease when they are born. The newborn in the story was born not long ago in Portugal. His mother gave birth to him naturally in the toilet at home. There was no one else around at the time. When the mother turned around to ask for help, she found that the baby had been submerged in water for 2 minutes. The baby was quickly rushed to a local hospital and diagnosed with premature sepsis.

This is the first case of sepsis caused by Acinetobacter baumannii infection in the hospital. During hospitalization, the infant thus developed severe and persistent thrombocytopenia and neutropenia. Fortunately, he was infected with wild Acinetobacter baumannii and was sensitive to many drugs, so the treatment was effective quickly. Doctors believe that the poor birth environment may have caused the baby's infection.

However, Acinetobacter baumannii infections can also be particularly severe. According to a 2021 study, some strains of Acinetobacter baumannii in hospital settings have developed resistance to a variety of antibiotics, including most available antibiotics, such as penicillins, cephalosporins, and carbapenems Antibiotics and more.

Acinetobacter baumannii is an opportunistic pathogen that primarily infects immunocompromised individuals with wounds, including infants, the elderly, and injured adults. Invasive surgery, the emergence of drug resistance, and the increase in immunocompromised hosts have gradually made Acinetobacter baumannii a pathogen that is difficult to eliminate in medical settings, especially ICUs. Studies have shown that in hospital settings, Acinetobacter baumannii infection can lead to a three-fold increase in patient mortality. This pathogenic bacteria can cause a variety of infections, such as pneumonia, urinary tract infections, meningitis, bacteremia, or gastrointestinal infections.

At this time, if we bring the perspective of this type of bacteria, we will have a completely different feeling: among the corpses of countless companions, the bacteria achieved "bloodline awakening" before dying and became indestructible. It destroyed the medical achievements that human scientists had painstakingly obtained for more than 100 years and found the ability to thrive in harsh environments.

However, in reality, we stand on the opposite side of this powerful pathogenic bacteria. So far, scientists have discovered various resistance mechanisms of this bacteria. For example, they reduce the permeability of the cell membrane, making it impossible for some antibiotics to enter and thus become ineffective. They also actively remove antibiotics that enter the body. For other antibiotics, they change the target of antibiotic action in the body, or directly produce hydrolases to destroy the antibiotic. It can be said that multi-drug resistant Acinetobacter baumannii is like setting a suitable "trap" for each antibiotic.

What impressed scientists was an important ability of this bacterium: genetic plasticity—it can achieve rapid genetic mutations and gene rearrangements, and integrate exogenous mobile genetic elements, such as drug resistance genes passed to it by other bacteria.

The more we face such dangerous pathogenic bacteria, the more cautious we need to be. In a recent study published in Nature Microbiology, scientists from Macquarie University in Australia found that many widely used disinfectants (or bactericides) may lead to multi-drug resistance The emergence and spread of sexually transmitted bacteria. This type of bacteria is generally resistant to multiple drugs and is difficult to treat.

We often use disinfectants to make our home environment, clothes, etc. cleaner. The cleaning products we use frequently contain more or less disinfectants. For example, the commonly used disinfectant in toothpaste and soap is triclosan, which is a broad-spectrum antibacterial agent. Triclosan will enter bacteria and prevent bacteria from synthesizing fatty acids by inhibiting a key enzyme, enoyl reductase (FabI), leading to their death. Some disinfectants commonly used for wound disinfection usually contain chlorhexidine or benzalkonium chloride. They are both cationic surfactants that can increase the permeability of bacterial cell membranes and allow the substances inside the bacteria to flow out, causing their death.

In addition, silver ion antibacterial agent is also a broad-spectrum antibacterial agent. It is also widely used in life and causes almost no harm to humans and animals. Many airlines use silver water filters, and swimming pool water is purified with disinfectant containing silver ions. In addition, silver ion antibacterial agents are also used to make antibacterial materials. After entering the bacteria, these silver ions will interact with the sulfhydryl groups in the cysteine residues on the protein, causing the protein to become inactive. In addition, such disinfectants disrupt iron homeostasis within bacteria, causing bacterial death.

In daily life, the concentrations of disinfectants we use are several orders of magnitude higher than their minimum germicidal concentration (MIC). And antiseptic products often contain a variety of disinfectants that kill bacteria in different ways. This prevents bacteria from developing drug resistance. In addition, some disinfectants without specific targets can also avoid the emergence of bacterial resistance. Some disinfectants interact with the phospholipid membrane of bacteria and promote bacterial lysis.

In such cases, the disinfectant can be very effective, but a lower concentration of disinfectant is likely to remain in the environment after disinfection. New research finds that this may lead to the emergence of drug resistance in new bacteria entering this environment. In other words, residual disinfectants from daily use can help bacteria become more resistant to antibiotics.

In the new study, scientists focused on 10 important disinfectants in clinical and daily use and studied how they affect the resistance of Acinetobacter baumannii. Most of these disinfectants are surfactants, which cause increased permeability of cell membranes and cell lysis.

They found that most disinfectants no longer have a bactericidal effect at concentrations well below their MIC, but can dissipate the potential on the bacterial cell membrane without affecting the permeability of the bacterial cell membrane. In addition to triclosan and 100% ethanol, many disinfectants have this effect. For example, when the concentration of silver nitrate is 1/32 of its MIC, it can still affect the cell membrane of bacteria, causing the outflow of protons within the bacteria.

In fact, the ion concentration gradient on both sides of the bacterial cell membrane is the energy source for many transmembrane proton-coupled pumps to transport substances. This change will significantly affect the transport ability of the bacterial cell membrane. Some antibiotics, such as aminoglycoside antibiotics (gentamicin), need these pumps to enter the bacteria. The researchers tested a strain of Acinetobacter baumannii that was susceptible to gentamicin and found that a variety of disinfectants, including benzalkonium chloride, chlorhexidine, CTAB (cetyltrimethylammonium bromide) and poly Vitone-iodine, will increase the survival rate of this bacteria in gentamicin. It can be seen that very low concentrations of disinfectants can inhibit the bactericidal effect of some antibiotics by affecting the potential on the bacterial cell membrane.

If the antibiotics in the experiment are replaced with amikacin, ciprofloxacin or tigecycline, benzalkonium chloride and chlorhexidine will significantly increase the survival rate of bacteria. However, if both the disinfectant and antibiotic act on the bacterial cell membrane, the bactericidal effect of the antibiotic will become better, for example, the disinfectant is used in combination with colistin and imipenem. Overall, the researchers found that some disinfectants that affect the membrane potential of pathogenic bacteria can promote resistance to various antibiotics that target their interior.

What is not optimistic is that some studies have shown that bacteria have been able to produce a variety of drug efflux pumps, resulting in resistance to disinfectants. Although the resistance is low, with this resistance ability, bacteria are more resistant to disinfectants. It is possible to become resistant to multiple antibiotics. Scientists have discovered that some bacteria are resistant to disinfectants. For example, some Acinetobacter baumannii resist the bactericidal effect of triclosan through multi-drug resistance efflux pumps (MDR efflux pumps) or altered enzyme FabI.

In addition, intermittent antibiotic exposure can also cause bacteria to evolve resistance faster and even more diverse resistances. Researchers mentioned: We usually ignore residual disinfectants, but those disinfectants that are difficult to remove from the environment, especially chlorhexidine, benzalkonium chloride, etc., may be more likely to induce antibiotic resistance in bacteria.