Quorum Sensing - Bacteria - Evolution - Anti-quorum Sensing Medical Treatments

Anti-quorum Sensing Medical Treatments

Today, about 70% of the bacteria that cause infections are resistant to at least one of the drugs most commonly used for treatment. Some organisms are resistant to all approved antibiotics and can be treated only with experimental and potentially toxic drugs. A substantial increase in resistance of bacteria that cause community-acquired infections has also been documented, especially in the staphylococci and pneumococci, which are prevalent causes of disease and mortality. In a recent study, 25% of bacterial pneumonia cases were shown to be resistant to penicillin, and an additional 25% of cases were resistant to more than one antibiotic.

The current state of antibiotic affairs is due to the manner in which existing antibiotics work. All current antibiotics aim to kill the individual bacteria in one manner or another (by inhibiting synthesis of new bacteria, usually). This environmental pressure activates the evolutionary mechanisms that select for resistant strains. In other words, bacteria that are not resistant to the antibiotic are killed off, leaving the resistant organisms to multiply unchecked without competition. This is why resistant strains spread so rapidly and occur so frequently.

Recent research into quorum sensing systems has produced compounds that can disrupt the bacteria's ability to communicate, thereby disabling or diminishing the bacteria's ability to become pathogenic. Therefore, the body is not compromised by cell damage, inflammation, toxicity, or other detrimental effects of the bacteria. This gives the body time to eradicate the bacteria naturally through normal immune system functions.

The advantage of the anti-quorum sensing approach to controlling infection is that there are few evolutionary forces that select for resistance—there is little in the process that would create resistant strains. Since the compounds kill none of the bacteria, any resistant mutations must compete with living, non-resistant individuals. In other words, there is no survival advantage to the resistant mutations, and natural selection does not come into play. Resistant strains will be unlikely to occur.

Next to the potential antimicrobial functionality, quorum-sensing molecules, especially the peptides, are investigated for their use in other therapeutic domains as well, including immunology and oncology. This hypothesis is based on (1) the recent evidence of prokaryote–eukaryote signalling by the use of quorum-sensing signalling molecules, (2) the apoptotic phenomenon seen in bacteria, (3) the clear similarities between the bacterial quorum-sensing mechanisms and the metastatic process tumor cells initiate, (4) the multiple receptor targeting and (5) the possibility of pharmacologic manipulation of peptides, resulting in increased receptor targeting.