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Patients with recurrent Escherichia coli bacteremia can harbor strains with mutations that promote multidrug antibiotic resistance:

Certain patients with gram-negative bacterial bloodstream infections (GNB-BSIs) are well-known to experience recurrent bacteremia after receiving antimicrobial therapy — but is this phenomenon due to microbial factors? Researchers have analyzed isolates from patients with relapsed GNB-BSIs in which the initial and subsequent strains were nearly identical genetically.

Paired bacteremic isolates of E. coli, Klebsiella species, Serratia marcescens, and Pseudomonas aeruginosa were identified for a detailed analysis of the E. coli strains. Time-kill studies found that 4 of the 11 recurrent isolates had a higher number of bacterial colony-forming units persisting through 24 hours of exposure to meropenem. The recurrent strain with the greatest number of persisting cells had a loss-of-function mutation in the ptsI gene (involved in the phosphoenolpyruvate phosphotransferase system and shown in vitro to be important to the effects of bactericidal antibiotics). Challenging mice with the initial and ptsI mutant recurrent strains in a bacteremia model showed that both variants were equally virulent, but the recurrent strain was 10-fold less susceptible to treatment with ertapenem.

This work affirms the clinical importance of persister bacterial strains in relapsing infections while also confirming the role of bacterial metabolic pathways in the development of antibiotic resistance. The results also raise the question of whether more-prolonged antibiotic therapy might be appropriate in individuals who develop recurrent E. coli bacteremia without an obvious host-related explanation.

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Highly reducing or oxidizing photocatalysts are a fundamental challenge in photochemistry. Only a few transition metal complexes with Earth-abundant metal ions have so far advanced to excited state oxidants, including chromium, iron, and cobalt. All these photocatalysts require high energy light for excitation and their oxidizing power has not yet been fully exploited. Furthermore, precious and hence expensive metals are the decisive ingredients in most cases.

A team of researchers headed by Professor Katja Heinze of Johannes Gutenberg University Mainz (JGU) has now developed a new molecular system based on the element manganese. Manganese, as opposed to , is the third most abundant metal after iron and titanium and hence widely available and very cheap. The study is published in the journal Nature Chemistry.

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The researchers applied the higher resonant radio frequency, which prompted any normal, “hot” fermions in the liquid to ring in response. The researchers then could zero in on the resonating fermions and track them over time to create “movies” that revealed heat’s pure motion — a sloshing back and forth, similar to sound waves.

“For the first time, we can take pictures of this substance as we cool it through the critical temperature of superfluidity, and directly see how it transitions from being a normal fluid, where heat equilibrates boringly, to a superfluid where heat sloshes back and forth,” Zwierlein says.

The experiments mark the first time scientists have been able to image second sound directly and the pure motion of heat in a superfluid quantum gas. The researchers plan to extend their work to map heat’s behavior more precisely in other ultracold gases. Then, they say their findings can be scaled up to predict how heat flows in other strongly interacting materials, such as high-temperature superconductors and neutron stars.

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