Evolution-proof inhibitors of public good cooperation: a screening strategy inspired by social evolution theory

Interference with public good cooperation provides a promising novel antimicrobial strategy since social evolution theory predicts that resistant mutants will be counter-selected if they share the public benefits of their resistance with sensitive cells in the population. Although this hypothesis is supported by a limited number of pioneering studies, an extensive body of more fundamental work on social evolution describes a multitude of mechanisms and conditions that can stabilize public behaviour, thus potentially allowing resistant mutants to thrive. In this paper we theorize on how these different mechanisms can influence the evolution of resistance against public good inhibitors. Based hereon, we propose an innovative 5-step screening strategy to identify novel evolution-proof public good inhibitors, which involves a systematic evaluation of the exploitability of public goods under the most relevant experimental conditions, as well as a careful assessment of the most optimal way to interfere with their action. Overall, this opinion paper is aimed to contribute to long-term solutions to fight bacterial infections.

Metabolic reprogramming of Pseudomonas aeruginosa by phage-based quorum sensing modulation

The Pseudomonas quinolone signal (PQS) is a multifunctional quorum sensing molecule of key importance to P. aeruginosa. Here, we report that the lytic Pseudomonas bacterial virus LUZ19 targets this population density-dependent signaling system by expressing quorum sensing targeting protein (Qst) early during infection. We demonstrate that Qst interacts with PqsD, a key host quinolone signal biosynthesis pathway enzyme, resulting in decreased levels of PQS and its precursor 2-heptyl-4(1H)-quinolone. The lack of a functional PqsD enzyme impairs LUZ19 infection but is restored by external supplementation of 2-heptyl-4(1H)-quinolone, suggesting that LUZ19 exploits the PQS system for successful infection. We establish a broad functional interaction network of Qst, which includes enzymes of cofactor biosynthesis pathways (CoaC/ThiD) and a non-ribosomal peptide synthetase pathway (PA1217). Qst therefore represents an exquisite example of intricate reprogramming of the bacterium by a phage, which may be further exploited as tool to combat antibiotic resistant bacterial pathogens.

Inhibiting bacterial cooperation is an evolutionarily robust anti-biofilm strategy

Bacteria commonly form dense biofilms encased in extracellular polymeric substances (EPS). Biofilms are often extremely tolerant to antimicrobials but their reliance on shared EPS may also be a weakness as social evolution theory predicts that inhibiting shared traits can select against resistance. Here we show that EPS of Salmonella biofilms is a cooperative trait whose benefit is shared among cells, and that EPS inhibition reduces both cell attachment and antimicrobial tolerance. We then compare an EPS inhibitor to conventional antimicrobials in an evolutionary experiment. While resistance against conventional antimicrobials rapidly evolves, we see no evolution of resistance to EPS inhibition. We further show that a resistant strain is outcompeted by a susceptible strain under EPS inhibitor treatment, explaining why resistance does not evolve. Our work suggests that targeting cooperative traits is a viable solution to the problem of antimicrobial resistance.

Bacterial biofilms rely on shared extracellular polymeric substances (EPS) and are often highly tolerant to antibiotics. Here, the authors show in in vitro experiments that Salmonella does not evolve resistance to EPS inhibition because such strains are outcompeted by a susceptible strain under inhibitor treatment.

Electrical injuries to peripheral nerves

As people come frequently into contact with electrical power sources, electrical injuries to peripheral nerves are commonly seen. The authors first review the parameters determining the severity and distribution of electrical injury to nerve tissue. These include tissue resistance, tissue susceptibility, current pathway, type of current, current density, duration and size of electrical contact. Subsequently, the pathophysiology of electrical injuries to nerve tissue is reviewed. Such injuries can be the result of thermal damage, vascular impairment, histological or electrophysiological changes in peripheral nerves, or direct mechanical trauma. Each of these types of injuries causes, specific lesions. As these lesions, especially delayed peripheral neurologic injury, can cause medico-legal problems, it is important to emphasize that electroneuromyography must be performed as early as possible.

Electromyography of the external anal sphincter muscle during urodynamic testing in children with meningomyelocele

In this study the correlation between the electromyographic examination of the external sphincter muscle and the urodynamic findings in patients with meningomyelocele was evaluated. Urodynamic testing, consisting of cystometry with bladder, urethral and abdominal pressure monitoring was performed with simultaneous electromyography of the external and sphincter muscle in 61 children, 29 boys and 32 girls, divided in groups according to age and to the level of lesion. Normal urodynamic studies were always correlated with normal external sphincter electromyography. In all patients with a high lesion and in 79% of all others detrusor hyperactivity was correlated with pathological sphincter electromyography. The clinical neurological level of the lesion was not correlated with the function of the detrusor-sphincter mechanism. In 29% of the patients examined with needle electromyography detrusor-sphincter dyssynergia was found, which is less than in most other published studies. And although dyssynergia is a risk factor for renal deterioration, the authors conclude that its effect on the ureter is less important than in subjects with normal perineal musculature, since 80% of the examined patients with meningomyelocele showed pathological sphincter electromyography. These findings thus show a significant correlation between electromyography of the external sphincter muscle and the urodynamic findings in meningomyelocele patients, and clearly demonstrate the importance of urodynamic testing with simultaneous external sphincter electromyography, in order to improve both diagnostic accuracy and reliability of follow-up and treatment.

Condensing osteitis of the clavicle. Report of two cases and review of the literature

Condensing osteitis of the clavicle, better defined as aseptic enlarging osteosclerosis of the clavicle, is a rare and benign idiopathic lesion. It is probably of degenerative or mechanical origin, and is most commonly seen in middle-aged women as a tender swelling over the medial one-third of the clavicle. Although the clinical features may be confusing and nonspecific, the typical radiographic and histopathological findings will mostly lead to a correct diagnosis of this disorder. The differential diagnosis is quite extensive. Most difficult to differentiate are: avascular necrosis of the medial clavicular epiphysis, sternoclavicular orsteoarthritis, low-grade chronic osteomyelitis, sternocostoclavicular hyperostosis and Tietze's syndrome. The authors recommend a thorough physical examination and technical tests, not only in subjects with pain of the clavicle but also in those with shoulder pain only, especially in women who are in their fourth decade. Treatment with analgesic and anti-inflammatory medications may be variably effective. In refractory cases excisions of the medial one-third of the clavicle may be indicated to offer better relief of symptoms as well as to exclude malignancy.