Tag: Pseudomonas aeruginosa

Chemists Discover Alarming Resistance of P. Aeruginosa to Common Cleaners

Photo by Matilda Wormwood

A new study reveals widespread resistance of a major bacterial pathogen to the active ingredients in cleaning agents commonly used in hospitals and homes. The American Chemical Society Infectious Diseases published the research led by chemists at Emory University. It demonstrates the surprising level of resistance to cleaning agents of multidrug-resistant Pseudomonas aeruginosa, a pathogen of particular concern in hospital settings.

The study also identifies biocides that are highly effective against P. aeruginosa, including a novel compound developed at Emory in collaboration with Villanova University. The researchers describe how these biocides work differently than most disinfectants currently in use.

“We hope our findings can help guide hospitals to reconsider protocols for the sanitation of patient rooms and other facilities,” says William Wuest, Emory professor of chemistry and a senior author of the study. “We also hope that our findings of a new mechanism of action against these bacterial strains may help in the design of future disinfectant products.”

First authors of the study are Christian Sanchez (who did the work as an Emory PhD student in chemistry and, following graduation, joined the faculty at Samford University) and German Vargas-Cuebas, an Emory PhD candidate in microbiology through Laney Graduate School.

“Resistance of pathogens to cleaning agents is an area that’s often overlooked,” Vargas-Cuebas says, “but it’s an important area of study, especially with the rise in antibiotic-resistant pathogens worldwide.”

Kevin Minbiole, professor of chemistry at Villanova, is co-senior author of the paper.

Workhorse disinfectants losing steam

Quaternary ammonium compounds, or QACs, are active ingredients commonly seen in household and hospital cleaners, including some disinfectant sprays and liquids, antibacterial sanitizing wipes and soaps.

“There are a handful of QACs that have been the workhorse disinfectants for around 100 years, on the frontline of most homes and hospitals,” Wuest says. “Very little has been done to modify their structures because they have long worked so well against many common bacteria, viruses, molds and fungi and they’re so simple and cheap to make.”

The Wuest lab is a leader in studies of QACs and other disinfecting agents. One issue Wuest and his colleagues have identified is that some bacterial strains are developing resistance to QACs. That trend could cause serious problems for sanitation in hospitals.

A pathogen of critical priority

More than 2.8 million antimicrobial-resistant infections occur in the United States each year, leading to more than 35,000 deaths, according to the Centers for Disease Control and Prevention (CDC).

The CDC names multidrug-resistant P. aeruginosa as one of seven pathogens causing infections that increased in the United States during the COVID-19 pandemic and remain above prepandemic levels.

Worldwide, P. aeruginosa causes more than 500,000 deaths annually and has been named a pathogen of critical priority by the World Health Organization.

P. aeruginosa is commonly found in the environment, including in soil and freshwater. Reservoirs in hospital settings can include drains, taps, sinks and equipment washers.

While the bacterium generally does not affect healthy people it can cause infections in individuals with cystic fibrosis and those who are immunocompromised, such as patients with burns, cancer and many other serious conditions. Patients with invasive devices such as catheters are also at risk due to the ability of P. aeruginosa to form biofilms on the surfaces of these devices.

P. aeruginosa, like other gram-negative bacteria, is enclosed in a second, fatty outer membrane that acts as a protective capsule, making it more difficult to kill.

How QACs kill

QACs have a nitrogen atom at the center of four carbon chains. In simplest terms, the positively charged head of the nitrogen center is drawn to the negatively charged phosphates of the fatty acids encasing P. aeruginosa and many other bacteria and viruses. The heads of the carbon chains act like spearpoints, stabbing into both protective fatty membranes and inner cellular membranes and causing pathogens to disintegrate.

The researchers tested 20 different drug-resistant strains of P. aeruginosa collected from hospitals around the world by the Walter Reed National Military Medical Center as part of the Multidrug-Resistant Organism Repository and Surveillance Network.

The results showed that all 20 strains were at least partially resistant to QACs — the common active ingredient in most front-line cleaning agents — and 80% of the strains were fully resistant to QACs.

“This mechanism has worked for 100 years essentially by slicing into the outer and inner membranes of a pathogen and destroying them,” Wuest says. “We were surprised to see the level at which that appears to no longer be the case.”

Improper use of cleaning agents may be one factor leading to resistance, Wuest theorizes.

“QACs don’t immediately kill,” he explains. “After application, it’s important to wait four or five minutes before wiping these cleaning agents away. It’s also important to use the right concentration. If used inappropriately, some bacteria can survive, which can lead to them developing resistance.”

Greater use of cleaning agents during the COVID-19 pandemic may have given P. aeruginosa and some other hard-to-kill pathogens more opportunities to develop resistance, he adds.

A new method that ‘works surprisingly well’

For the current paper, the researchers also tested the resistance of the panel of multidrug-resistant P. aeruginosa strains against a new quaternary phosphonium compound, or QPC, developed in the Wuest and Minbiole labs. The results showed that the compound was highly effective at killing all 20 of the resistant P. aeruginosa strains.

“It works surprisingly well even at a low concentration,” Vargas-Cuebas says.

The researchers demonstrated that their novel QPC works not by piercing the protective outer capsule of a P. aeruginosa bacterium but by diffusing through this outer membrane and then selectively attacking the inner cellular membrane.

“It’s counterintuitive,” Wuest remarks. “You would think that the approach of conventional biocides, to take out both membranes, would be a more effective way to kill P. aeruginosa. Why does passively diffusing through the outer membrane and focusing on attacking the inner membrane make our QPC compound more effective? We don’t know yet. It’s like a magic trick.”

They showed that this same mechanism underlies the effectiveness of two commercial antiseptics: octenidine, more commonly used in Europe as a hospital antiseptic, and chlorhexidine, a common ingredient in mouthwashes.

Wuest and colleagues plan to continue research into how this newly identified mechanism may work against an array of pathogens and how that might translate into new biocides and more effective cleaning protocols in hospitals and other settings.

“Our work is paving the way for much-needed innovations in disinfectant research,” Wuest says.

Source: Emory University

Peptides May Solve the Sticky Problem of Bacterial Biofilms

This image shows an intricate colony of Pseudomonas aeruginosa. The bacteria have self-organised into a sticky, mat-like colony called a biofilm, which allows them to cooperate with each other, adapt to changes in their environment, and ensure their survival.
Credit: Scott Chimileski and Roberto Kolter, Harvard Medical School, Boston

Researchers have developed peptides that can help combat bacteria growing in biofilms, which occur in up to 80% of human infections. Their results, published in Nature Chemical Biology, may offer a way to tackle antimicrobial-resistant infections. 

Treating infections becomes significantly more challenging when biofilms are present, as they not only reduce the effectiveness of antibiotics but also give rise to several medical complications. These complications include infections following joint replacements, prosthetic devices, as well as contamination in catheters and other medical equipment. The lack of specific treatments makes the management and treatment of biofilms exceptionally difficult.

The team of researchers, led by Dr Clarissa Melo Czekster and Dr Christopher Harding from the School of Biology at St Andrews, in collaboration with researchers at University of Dundee, developed antimicrobial peptides that can target the harmful bacteria growing in biofilms.

The team determined how a key enzyme (PaAP) in biofilms work and developed a revolutionary new strategy to inhibit the protein. Their inhibitor is potent and targets cells from the human pathogen Pseudomonas aeruginosa in biofilms. P. aeruginosa, a WHO pathogen of concern, causes chronic infections in patients with cystic fibrosis and other conditions, which means a biofilm inhibitor is urgently needed.

Dr Czekster and the team are currently working in collaboration with the University of St Andrews Technology Transfer Centre and industry partner Locate Bio, a biomedicine spinout of the University of Nottingham, to commercialise the technology. The Locate Bio team are trialling the peptides to see how they work with the company’s Programmed Drug Release technology to develop new orthobiologic solutions and products. The Technology Transfer Centre has filed a UK priority patent application.

Dr Czekster said: “Our research reveals how designed inhibitors can target a key enzyme in bacterial virulence, offering molecular insights applicable to aminopeptidases in diverse organisms.

“This remarkable new research presents an innovative strategy to target bacterial biofilms and pave the way for better treatment of bacterial infection.”

Source: University of St. Andrews

Pseudomonas Aeruginosa Locks out Immune Cells

Pseudomonas
Scanning Electron Micrograph of Pseudomonas aeruginosa. Credit: CDC/Janice Carr

Pseudomonas aeruginosa bacteria are a common menace in hospital wards, causing life-threatening infections, and are often resistant to antibiotics. Researchers have discovered a mechanism that likely contributes to the severity of P. aeruginosa infections, which could also be a target for future treatments. The results were recently appeared in the journal EMBO Reports.

Many bacterial species use sugar-binding molecules called lectins to attach to and invade host cells. Lectins can also influence the immune response to bacterial infections. However, these functions have hardly been researched so far. A research consortium led by Prof Dr Winfried Römer at the University of Freiburg and Prof Dr Christopher G. Mueller at the CNRS/University of Strasbourg has investigated the effect of the lectin LecB from P. aeruginosa on the immune system. It found that isolated LecB can render immune cells ineffective: The cells are then no longer able to migrate through the body and trigger an immune response. The administration of a substance directed against LecB prevented this effect and led to the immune cells being able to move unhindered again.

LecB blockades immune cells

As soon as they perceive an infection, cells of the innate immune system migrate to a nearby lymph node, where they activate T and B cells, triggering a targeted immune response. LecB, according to the current study, prevents this migration. “We assume that LecB not only acts on the immune cells themselves in this process, but also has an unexpected effect on the cells lining the inside of the blood and lymph vessels,” Römer explains. “When LecB binds to these cells, it triggers extensive changes in them.” Indeed, the researchers observed that important structural molecules were relocated to the interior of the cells and degraded. At the same time, the cell skeleton became more rigid. “The cell layer thus becomes an impenetrable barrier for the immune cells,” Römer said.

An effective agent against LecB

Can this effect be prevented? To find out, the researchers tested a specific LecB inhibitor that resembles the sugar building blocks to which LecB otherwise binds. “The inhibitor prevented the changes in the cells, and T-cell activation was possible again,” Mueller said. The inhibitor was developed by Prof Dr Alexander Titz, who conducts research at the Helmholtz Institute for Pharmaceutical Research Saarland and Saarland University.

Further studies are needed to determine how clinically relevant the inhibition of the immune system by LecB is to the spread of P. aeruginosa infection and whether the LecB inhibitor has potential for therapeutic application. “The current results provide further evidence that lectins are a useful target for the development of new therapies, especially for antibiotic-resistant pathogens such as P. aeruginosa,” the authors conclude.

Source: University of Freiburg

Turning M. Pneumoniae into ‘Living Medicine’

Pseudomonas
Scanning Electron Micrograph of Pseudomonas aeruginosa. Credit: CDC/Janice Carr

Using a modified version of the bacterium Mycoplasma pneumoniae, researchers have designed the first ‘living medicine’ to treat lung infections. Their method is reported in the journal Nature Biotechnology. The treatment targets Pseudomonas aeruginosa, a common source of hospital-acquired infections and which is naturally multi-drug resistant.

Researchers removed the M. pneumoniae‘s ability to cause disease and repurposing it to attack P. aeruginosa instead. The modified bacterium is used in combination with low doses of antibiotics that would otherwise not work on their own.

Researchers tested the efficacy of the treatment in mice, finding that it significantly reduced lung infections. The ‘living medicine’ doubled mouse survival rate compared to not using any treatment. Administering a single, high dose of the treatment showed no signs of toxicity in the lungs. Once the treatment had finished its course, the innate immune system cleared the modified bacteria in a period of four days.

P. aeruginosa infections are difficult to treat because the bacteria lives in communities that form biofilms. Biofilms can attach themselves to various surfaces in the body, forming impenetrable structures that escape the reach of antibiotics.

P. aeruginosa biofilms can grow on the surface of endotracheal tubes used by critically-ill patients who require mechanical ventilators to breathe. This causes ventilator-associated pneumonia (VAP), a condition affecting 9–27% of patients who require intubation. The incidence exceeds 50% for patients intubated because of severe COVID. VAP can extend the duration in intensive care unit for up to 13 days and kills 9–13% of patients.

The authors of the study engineered M. pneumoniae to dissolve biofilms by equipping it with the ability to produce various molecules including pyocins, toxins naturally produced by bacteria to kill or inhibit the growth of Pseudomonas bacterial strains. To test its efficacy, they collected P. aeruginosa biofilms from the endotracheal tubes of patients in intensive care units. They found the treatment penetrated the barrier and successfully dissolved the biofilms.

“We have developed a battering ram that lays siege to antibiotic-resistant bacteria. The treatment punches holes in their cell walls, providing crucial entry points for antibiotics to invade and clear infections at their source. We believe this is a promising new strategy to address the leading cause of mortality in hospitals,” says Dr María Lluch, co-corresponding author of the study.

With the aim of using the ‘living medicine’ to treat VAP, the researchers will carry out further tests before reaching the clinical trial phase. The treatment is expected to be administered using a nebuliser.

M. pneumoniae is one of the smallest known species of bacteria. Dr Luis Serrano first had the idea to modify the bacteria and use it as a ‘living medicine’ two decades ago. Dr Serrano is a specialist in synthetic biology, a field that involves repurposing organisms and engineering them to have new, useful abilities. With just 684 genes and no cell wall, the relative simplicity of M. pneumoniae makes it ideal for engineering biology for specific applications.

One of the advantages of using M. pneumoniae to treat respiratory diseases is that it is naturally adapted to lung tissue. After administering the modified bacterium, it travels straight to the source of a respiratory infection, where it sets up shop like a temporary factory and produces a variety of therapeutic molecules.

By showing that M. pneumoniae can tackle infections in the lung, the study opens the door for researchers creating new strains of the bacteria to tackle other types of respiratory diseases such as lung cancer or asthma. “The bacterium can be modified with a variety of different payloads – whether these are cytokines, nanobodies or defensins. The aim is to diversify the modified bacterium’s arsenal and unlock its full potential in treating a variety of complex diseases,” says ICREA Research Professor Dr. Luis Serrano.

In addition to designing the ‘living medicine’, Dr. Serrano’s research team are also using their expertise in synthetic biology to design new proteins that can be delivered by M. pneumoniae. The team are using these proteins to target inflammation caused by P. aeruginosa infections.

Though inflammation is the body’s natural response to an infection, excessive or prolonged inflammation can damage lung tissue. The inflammatory response is orchestrated by the immune system, which release mediator proteins such as cytokines. One type of cytokine, IL-10, has well-known anti-inflammatory properties and is of growing therapeutic interest.

Dr Serrano’s research group used protein-design software to engineer new versions of IL-10 purposefully optimised to treat inflammation. The cytokines were designed to be created more efficiently and to have higher affinity, meaning less cytokines are needed to have the same effect.

The researchers engineered strains of M. pneumoniae that expressed the new cytokines and tested its efficacy in the lungs of mice with acute P. aeruginosa infections. They found that engineered versions of IL-10 were significantly more effective at reducing inflammation compared to the wild type IL-10 cytokine.

According to Dr Ariadna Montero Blay, co-corresponding author of that study, “live biotherapeutics such as M. pneumoniae provide ideal vehicles to help overcome the traditional limitations of cytokines and unlock their huge potential in treating a variety of human diseases. Engineering cytokines as therapeutic molecules was critical to tackle inflammation. Other lung diseases such as asthma or pulmonary fibrosis could also stand to benefit from this approach.”

Source: Center for Genomic Regulation

Community-acquired Antimicrobial Resistant UTIs can be More Deadly

Pseudomonas
Scanning Electron Micrograph of Pseudomonas aeruginosa. Credit: CDC/Janice Carr.

A study from Australia’s scientific organisation CSIRO has revealed that antimicrobial resistant (AMR) bacteria in urinary tract infections are more lethal, especially Enterobacteriaceae. The findings are published online in Open Forum Infectious Diseases.

Antimicrobial resistance (AMR) bacteria can be passed between humans: through hospital transmission and community transmission. While hospital acquired resistance is well researched, there are few studies focusing on the burden of community transmission.

To address this, the study analysed data from 21 268 patients across 134 Queensland hospitals who acquired their infections in the community. The researchers found that patients were almost two and a half (2.43) times more likely to die from community acquired drug-resistant UTIs caused by Pseudomonas aeruginosa and more than three (3.28) times more likely to die from community acquired drug-resistant blood stream infections caused by Enterobacteriaceae than those with drug-sensitive infections. The high prevalence of UTIs make them a major contributor to antibiotic use, said CSIRO research scientist, Dr Teresa Wozniak.

“Our study found patients who contracted drug-resistant UTIs in the community were more than twice as likely to die from the infection in hospital than those without resistant bacteria,” Dr Wozniak said. “Without effective antibiotics, many standard medical procedures and life-saving surgeries will becoming increasingly life-threatening. “Tracking the burden of drug-resistant infections in the community is critical to understanding how far antimicrobial resistance is spreading and how best to mitigate it.”

The study’s findings will provide further guidance for managing AMR in the community, such as developing AMR stewardship programs that draw on data from the population being treated.

CEO of CSIRO’s Australian e-Health Research Centre, Dr David Hansen, said the magnitude of the AMR problem needs to be understood to mitigate it. “Tracking community resistance is difficult because it involves not just one pathogen or disease but multiple strains of bacteria,” Dr Hansen said. “Until now we haven’t been using the best data to support decision making in our fight against AMR. Data on community acquired resistance is an important contribution to solving the puzzle. “Digital health has an important role in using big data sets to describe patterns of disease and drive important population health outcomes.”

Source: CSIRO

An Unexpected Ally: Pathogen Enhances Antifungal Drug

Scanning Electron Micrograph of Pseudomonas aeruginosa.
Credit: CDC/Janice Carr

While pathogens usually work against drug treatments, sometimes, they can actually strengthen them, according to a new University of Maine study published in the journal Infection and Immunity.

Polymicrobial infections, which are a combination of bacteria, viruses, fungi and parasites, are challenging to treat because it is not well understood how pathogens interact during infection and how these interactions affect the drugs treating them.

In a study published in Infection and Immunity, University of Maine researchers examined two common pathogens that often occur at similar sites, particularly in cystic fibrosis and mechanically ventilated patients: Candida albicans and Pseudomonas aeruginosa.

Candida is the fourth most common hospital-acquired pathogen, and many antifungal agents only slow it rather than kill it outright. Meanwhile, P. aeruginosa infects 90% of all adult cystic fibrosis patients. Combined, C. albicans and P. aeruginosa cause more serious disease in cystic fibrosis and ventilated patients.

The researchers investigated the effectiveness of the antifungal drug fluconazole in vitro and then during infection of the zebrafish with both pathogens. Fluconazole slows fungal growth, but Candida can become tolerant to the drug and not only survive, but also evolve tolerance that leads to therapy failure and, potentially, death.

The results showed that P. aeruginosa in fact works with fluconazole to eliminate drug tolerance and clear the C. albicans infection in the culture and the zebrafish.

“Polymicrobial infections are challenging to treat not only because of the lack of understanding of how invading microorganisms interact but also because we don’t know how these interactions affect treatment efficacy. Our work demonstrates that polymicrobial interactions can indeed affect treatment efficacy and, most importantly, it highlights the importance of nutrient availability in the environment -; such as iron in our study -; and how it modulates treatment efficacy,” explained Siham Hattab, lead author of the study.

What’s more, the bacteria also enhance the drug’s ability against a second pathogenic Candida species that tends to be more resistant to the drug.

The increased effectiveness of the drug suggests to the researchers that there is still much more to learn about how current drugs work when targeting these dangerous and complex polymicrobial infections.

Senior study author, Robert Wheeler, associate professor of microbiology said: “We are really excited to have revealed that sometimes drugs against fungal infection can work even better in a more ‘real-world’ situation than in the test tube. There is still a lot to learn about how pathogens interact during infection, and it will be interesting to see how the bacteria manage to work with the drugs to target Candida.”

Source: University of Maine