Perhaps an increase in the use of QAC during a pandemic increased antimicrobial resistance to both QACs themselves and antibiotics to treat infections. However, a new study offers an alternative set of chemicals known as quaternary phosphonium compounds (QPCs) that have a phosphorus atom where the nitrogen centers of QACs will be located (ACS Infect. Dis. 2022, DOI: 10.1021 / acsinfecdis.1c00611). Research shows that QPCs are more effective than commercial QACs against a wide range of pathogens.
“QACs have been around for 85 years with a disappointing amount of innovation since then,” he says Kevin Minbioleprofessor of chemistry at Vilanova University and one of the authors of the study.
QPCs consist of cationic phosphonium heads and a hydrocarbon tail. Cationic heads are attracted to the negative charge of the bacterial membrane by moving the tails to the distance of impact to pierce the membrane, thereby disrupting the integrity of the microbes.
Minbiole and his colleagues synthesized 59 different QPCs, varying the tail groups and the number of cationic heads on each molecule. The researchers then tested the chemicals with the best water solubility to see if they could kill six strains of bacteria, including methicillin-resistant ones. Staphylococcus aureus (MRSA) and Escherichia coli.
Overall, bisQPC – QPC with two phosphonium heads – were the most effective. One in particular, known as P6P-10.10, performed well against all six strains of bacteria and was 64 times more lethal against some strains compared to commercially available QACs. It is believed that two cationic heads are better than one because they increase the adhesion of QPC to bacteria. But William WustA chemist from Emory University who worked with Minbiole on the study says the team still doesn’t know why two heads are better than three or four.
To test whether bacteria could develop resistance to QPC, researchers administered small doses of chemicals over 30 days to see if bacteria could figure out how to resist QPC doses that were once lethal. Could not, which pleasantly surprised the researchers. However, that doesn’t mean bacteria don’t end up avoiding QPC, Wust says.
“The activity of compounds against individual bacteria seems promising,” he says Catherine Richter, a biomedical researcher from the University of Adelaide who was not involved in the study. However, the study did not examine biofilms, which are communities of bacteria that interact with each other and live in a mucous matrix created by themselves. Because these structures are one of the most resistant means of protecting bacteria from antimicrobials, they “have serious effects on tolerance and the development of resistance, and therefore QPCs should also be studied against biofilms”.
https://cen.acs.org/biological-chemistry/infectious-disease/Quat-disinfectants-swap-nitrogen-phosphorus/100/i7?utm_source=LatestNews&utm_medium=LatestNews&utm_campaign=CENRSS Quat Disinfectants Replacing Nitrogen with Phosphorus May Stop Antimicrobial Resistance