Tag: antibiotic resistance

Categories : AntibioticsTags :

Study Reveals Global Patterns of Antibiotic Resistance

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Proportion of third-generation cephalosporin resistance in Klebsiella pneumoniae, for blood infections, 2019 (data from ATLAS, Pfizer). Credit: Institut Pasteur, Eve Rahbé

To understand the main determinants behind worldwide antibiotic resistance dynamics, scientists developed a statistical model based on the ATLAS antimicrobial resistance surveillance database, the model revealed significant differences in trends and associated factors depending on bacterial species and resistance to certain antibiotics. For example, in some bacteria, resistance was strongly affected by global sales for those corresponding antibiotics, while national sales had minimal impact for most. The results of the study were published in the journal The Lancet Planetary Health.

For example, countries with high quality health systems were associated with low levels of antibiotic resistance among all the gram-negative bacteria investigated, while high temperatures were associated with high levels of antibiotic resistance in Enterobacteriaceae. Surprisingly, national antibiotic consumption levels were not correlated with resistance for the majority of the bacteria tested. The results suggest that antibiotic resistance control measures need to be adapted to the local context and to targeted bacteria-antibiotic combinations.

Antibiotic resistance (ABR) is currently one of the most urgent threats to global health. It is a natural phenomenon, but improper use of antibiotics is contributing to it by selecting resistance and complicating bacterial infection-control strategies. Worldwide surveillance of antibiotic resistance, especially under the aegis of WHO has been set up, and several databases have been created to record ABR worldwide, with the long-term aim of improving understanding of the causes to help tackle the phenomenon. Antibiotic resistance varies considerably depending on the bacterial species, but a recent Lancet study estimated that in 2019, 1.27 million deaths worldwide were attributable globally to ABR and ABR was associated with 4.95 million deaths.

To identify the main factors associated with worldwide antibiotic resistance dynamics, a multidisciplinary research team at the Institut Pasteur developed a statistical model and analysed antibiotic resistance data from the ATLAS database, which contains data collected since 2004 in more than 60 countries on every continent. The scientists analysed the data by testing a large number of determinants to reveal the main factors of antibiotic resistance and understand how they relate to the dynamics observed worldwide.

“Research teams study how antibiotic resistance emerges in a bacterium in a Petri dish or in an individual, but we are currently lacking a population-level, global overview that can be used to investigate links between resistance and specific factors like national health system quality for different species of pathogenic bacteria. To understand the dynamics of antibiotic resistance, it needs to be studied at every level. That is what this study sets out to do,” explains Eve Rahbé, PhD research student and first author of the study.

The first stage of the study was to select relevant factors that could influence antibiotic resistance dynamics. “Although some biological factors are known, it was also important for us to investigate hypotheses associated with socioeconomic and climate factors,” continues the scientist. A total of eleven independent factors were selected, including health system quality (based on the Global Health Security index), antibiotic consumption and national wealth (GDP per capita), as well as data on travel and climate variables. Statistical models were then developed to study potential associations between the ATLAS data and the selected factors.

The analysis of global data for the period 2006-2019 initially revealed an increase in resistance to carbapenems for several species, although global trends were stable for other resistances. The study also demonstrated that the dynamics and factors associated with antibiotic resistance depend on bacteria-antibiotic combinations. Surprisingly, however, national antibiotic consumption was not significantly associated with resistance for the majority of bacteria tested (except for quinolone consumption for fluoroquinolone-resistant Escherichia coli and Pseudomonas aeruginosa and carbapenem consumption for carbapenem-resistant Acinetobacter baumannii).

Conversely, high health system quality was associated with low levels of antibiotic resistance in all the gram-negative bacteria tested. High temperatures were associated with high levels of antibiotic resistance, but only for Enterobacteriaceae (Escherichia coli and Klebsiella pneumoniae).

“This study reveals the wide range of factors leading to antibiotic resistance among different pathogenic bacteria at global level, and the need to adapt resistance control approaches to the local context (country, transmission context) and the specific bacteria-antibiotic combination,” concludes Philippe Glaser, Head of the Institut Pasteur’s Ecology and Evolution of Antibiotic Resistance Unit and co-last author of the study.

Source: Institut Pasteur

Categories : Antibiotics HospitalsTags :

‘Nothing Compares’ to Antibiotic Resistance Discovered in War-torn Ukraine

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Photo by Vony Razom 🇺🇦 on Unsplash

Researchers assisting microbiologists in Ukraine have found an extremely high level of bacterial resistance among the war-wounded patients treated in hospitals. The study, recently published in The Lancet Infectious Diseases, found resistance in many hospital-acquired infections stemming from damaged and overwhelmed healthcare infrastructure, with many samples resistant to the last-resort antibiotic colistin.

“I am quite thick-skinned and have witnessed numerous situations involving patients and bacteria. However, I must admit that I have never encountered bacteria as resistant as this before,” says Kristian Riesbeck, professor of Clinical Bacteriology at Lund University in Sweden.

There was never any doubt about helping out when Dr Oleksandr Nazarchuk, a microbiologist at a university in Vinnytsia, Ukraine, got in touch, says Kristian Riesbeck. Help was needed in Ukraine to assess the extent of antibiotic resistance in bacteria among severely injured patients in hospital.

In addition to all the human suffering caused by the war in Ukraine, another battle is being fought — an invisible war against resistant bacteria. This became evident when Kristian Riesbeck and his research colleagues analysed patient samples from seriously wounded patients, many of whom had burn injuries, in Ukraine. The patients had acquired infections while in hospital, primarily due to the overwhelmed wards and destroyed infrastructure.

Samples were collected from a total of 141 war victims, 133 adults who sustained injures during the war and eight infants diagnosed with pneumonia. These patients were admitted to three different hospitals in Ukraine, where they received emergency surgeries and intensive care to address their conditions.

“We observed that several the Gram-negative bacteria exhibited resistance to broad-spectrum antimicrobial agents, including newly developed enzyme-inhibiting antibiotics that are not yet available in the market. Moreover, nearly ten per cent of the samples contained bacteria that demonstrated resistance even to our ‘last-resort’ antibiotic, colistin. While we have encountered similar cases in India and China before, nothing compares to the extent of resistance observed in this study. As much as six per cent of all the samples contained bacteria resistant to every antibiotic we tested,” says Kristian Riesbeck.

He emphasizes that this clearly highlights the challenges posed by resistant bacteria in times of war. In particular, Kristian Riesbeck expresses concern regarding the resistance displayed by Klebsiella pneumoniae bacteria, as they have the potential to cause illness in individuals with a healthy and well-functioning immune system.

“This makes me very worried. It’s rare to encounter Klebsiella with such high levels of resistance, and it was not what we anticipated. While isolated cases have been documented in China, the magnitude of this situation surpasses anything we have seen before. While many countries are providing military aid and resources to Ukraine, it is equally crucial to assist them in addressing this ongoing situation. There is an evident risk of further spread of resistant bacteria, and this threatens the entire European region,” remarks Kristian Riesbeck.

Source: Lund University

Categories : AntibioticsTags :

Drug Slows Down Development of Antibiotic Resistance

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Methicillin resistant Staphylococcus aureus (MRSA) – Credit: CDC

As reported in the journal Science Advances, researchers at Baylor College of Medicine have come across a drug that, in laboratory cultures and animal models, significantly slows the development of antibiotic resistance in bacteira. The drug, called dequalinium chloride (DEQ), is a proof-of-concept for evolution-slowing drugs.

In this study, corresponding author Dr Susan M. Rosenberg and her colleagues looked for drugs that could prevent or slow down E. coli bacteria from developing resistance to two antibiotics when exposed to a third antibiotic, ciprofloxacin (cipro), the second most prescribed antibiotic in the US and one associated with high bacterial resistance rates.

The resistance is caused by new gene mutations that occur in the bacteria during infection. The drug DEQ reduces the speed at which new mutations are formed in bacteria, the team finds.

Previous work from the Rosenberg lab had shown that bacterial cultures in the lab exposed to cipro turn up mutation rate. They found a mutational “program” that is switched on by bacterial stress responses. Stress responses are genetic programs that instruct cells to increase production of protective molecules during stress, including stress from low concentrations of cipro. Low concentrations occur at the beginning and end of antibiotic therapies and if doses are missed.

The same stress responses also increase the ability to make genetic mutations, the Rosenberg group, then many other labs, have shown. Some of the mutations can confer resistance to cipro, while other mutations can allow resistance to antibiotics not yet encountered. Mutation-generating processes that are turned on by stress responses are called stress-induced mutation mechanisms.

Bacteria with antibiotic resistance mutations can then sustain an infection in the presence of cipro. This study is the first to show that in animal infections treated with cipro, the bacteria activate a known stress-induced genetic mutational process. Cipro resistance occurs mostly by the bacteria developing new mutations, both clinically and in the laboratory, rather than by acquiring genes that confer antibiotic resistance from other bacteria.

Looking to prevent the development of antibiotic resistance, the researchers screened 1120 drugs approved for human use for their ability to dial down the master bacterial stress response, which they showed counters the emergence of resistance mutations. In addition, and counterintuitively, they wanted “stealth” drugs that would not slow bacterial proliferation, which would confer a growth advantage to any bacterial mutants that resist the mutation-slowing drug itself. That is, drugs that are not antibiotics themselves.

“We found that DEQ fulfilled both requirements. Given together with cipro, DEQ reduced the development of mutations that confer antibiotic resistance, both in laboratory cultures and in animal models of infection, and bacteria did not develop resistance to DEQ,” said first author Yin Zhai, a postdoctoral associate in the Rosenberg lab. “In addition, we achieved this mutation-slowing effect at low DEQ concentrations, which is promising for patients. Future clinical trials are needed to evaluate the ability of DEQ to decelerate bacterial antibiotic resistance in patients.”

Source: Baylor College of Medicine

Categories : Antibiotics PaediatricsTags :

Antibiotic-resistant Bugs Claim Over 200 000 Infants Globally per Year, Finds Major Study

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Photo by Christian Bowen on Unsplash

By Adele Baleta for Spotlight

“The death of a child affects us all. Witnessing the loss of a newborn baby who has sepsis is terribly traumatic, especially so when antibiotics used to treat the child are ineffective,” says neonatologist Professor Sithembiso Velaphi.

“It’s very heavy for a mother to carry her baby, give birth, watch as her newborn gets seriously sick from infection, suffers while being pricked with drips and pumped with drugs to try and save the child – only for her to leave the hospital empty handed. It’s painful,” says Velaphi, who is the head of Paediatrics at Chris Hani Baragwanath Academic Hospital in Johannesburg.

Professor Sithembiso Velaphi, head of Paediatrics at Chris Hani Baragwanath Academic Hospital in Johannesburg. PHOTO: Kim Cloete for GARDP

Nurses and doctors feel sad and crushed too when they cannot save a newborn’s life because of antibiotic resistance to bacterial infections. “We need to prioritise the development of antibiotics to treat these babies. For us, success is seeing a baby get better and going home,” he says.

Velaphi was speaking to Spotlight about a landmark global observational study published in the journal  Plos Medicine (June 8) which found that many neonates (within 60 days of birth) get life-threatening bloodstream infections, or sepsis, and are dying because the antibiotics used to treat them are not effective. This is the first global overview to assess the extent of the problem. Spotlight last year reported on interim findings from the same study.

The study, called NeoOBS, led by the Global Antibiotic Research and Development Partnership (GARDP) recruited more than 3 200 babies in 19 hospitals in 11 countries – South Africa, Kenya, Uganda, Thailand, Vietnam, India, Greece, Italy, Bangladesh, Brazil, and China.

The researchers reported great variability in mortality rates of babies with sepsis across the 19 hospitals, ranging from 1% to 27.3%.

Sepsis affects up to 3 million babies a year globally. Importantly, the study’s 80 authors estimate that 214 000 newborns die every year from sepsis that has become antibiotic resistant, and this is mostly in low- to middle-income countries (LMIC). Many survivors suffer from neurodevelopmental problems. Treatment options have become increasingly limited as about 40% of infections are reported to be resistant to standard antibiotic treatments.

Many infections acquired in hospital

Almost 60% of infection-related deaths were due to infections acquired at the 19 hospitals under review. Klebsiella pneumoniae was the most common pathogen isolated.

Of the 40 antibiotics approved for use in adults since 2000, only four have included dosing information for neonates in their labelling. Currently, 43 adult antibiotic clinical trials are recruiting patients, compared to only six trials recruiting neonates, researchers say.

New antibiotic treatments are urgently needed, especially in LMICs where almost 1 in 5 babies with sepsis died. Premature babies are particularly vulnerable to infections because of their immature immune systems.

More than 200 different antibiotic combinations were used by hospitals included in the NeoOBS study, with repeated switching of antibiotics due to high resistance to treatments. This showed a pattern of limited use of the World Health Organization’s recommended first-line treatment.

Many doctors have had to opt for last-line antibiotics such as carbapenems because of the high degree of antibiotic resistance in their units or because they were the only treatment available.

Outlining various challenges, Velaphi says the risk of infections is very high in hospital settings where there is often a shortage of nurses, beds, and space between patients making it difficult to stop the spread of infection.  Chris Hani Baragwanath has an 18-bed Intensive Care Unit (ICU) that is almost always full and when the situation is desperate there is a spillover of patients into the high-care area. The pressure on the facility is huge and the influx of people from other countries has made it even more challenging, he says.

“There is a major problem of infection control, specifically related to high-risk babies – sick babies with complications who need interventions such as drips and even surgery. This increases the chances of infection. “More than 70% of all deaths ascribed to prematurity at the hospital were due to hospital-acquired multi-drug resistant infections,” he says.

The NeoSep 1 trial

The authors say the NeoOBS study has yielded “a wealth of high-quality data” needed to design trials for much-needed and appropriate treatments for sepsis in babies. Encouragingly, and building on from the observational study the first global hospital-based neonatal sepsis trial called NeoSep 1 is underway in Kenya and South Africa. Chris Hani Baragwanath is taking part in the trial together with Tygerberg Hospital in Cape Town and KEMRI, Kilifi County Hospital in Kenya. It’s planned that the trial will be expanded to other countries and regions in 2024 with the aim of recruiting 3 000 newborns.

A Personalised Randomised Controlled Trial (PRACTical) design will be used. According to GARDP and partners the design is a new way of comparing antibiotic treatments for neonatal sepsis. In addition, doctors can choose treatment regimens that are likely to work well for newborns in their specific hospital settings.

Researchers say the development pipeline for new antibiotic treatments is limited and the lack of a universal, effective standard of care creates huge challenges in conducting research to tackle neonatal sepsis. The PRACTical design has been specifically developed to address these challenges in important public health emergencies such as neonatal sepsis. (You can read more about how this type of trial works in the Lancet.)

The trial will compare the safety and efficacy of three new combinations of older antibiotics (fosfomycin-amikacin, flomoxef-amikacin, and flomoxef-fosfomycin) against the current standard of care. It will also assess and validate the doses of two antibiotics (fosfomycin and flomoxef) for use in newborns. The trial will also evaluate new combinations of generic antibiotics.

“We are hoping the trial will provide robust evidence that the antibiotic combinations are safe and effective and that this will lead to a change in both WHO and local treatment guidelines,” says Christina Obiero, Principal Investigator for the NeoSep1 trial for KEMRI at Kilifi County Hospital in a statement.

Severity and recovery scores

Principal Investigator for the NeoSep1 trial at Tygerberg Hospital, Professor Adrie Bekker tells Spotlight, “We have so few antibiotics that work effectively against these very sick babies. And even for those that we have, we are still not 100% sure how to dose these drugs to get accurate concentrations in the blood and to also make sure that the outcomes in these babies are as good as can be. This trial will help give us confidence that we are delivering more effective treatment.”

Bekker who is also Professor in the Division of Neonatology, Department of Paediatrics and Child Health at Stellenbosch University says a positive outcome of the NeoOBS study is the development of two important tools which can be used in ICUs globally.

The first is the NeoSep Severity Score which is a compilation of common symptoms and signs that can occur in a baby with clinical sepsis. The second is the NeoSep Recovery Score, which will assist clinicians in deciding if they can stop antibiotics earlier.

The tools are expected to help prevent the often excessive and inappropriate use of antibiotics for over too long a period, which compounds the problem of antibiotic resistance globally.

Diagnosis in older age groups, children, and adults, is generally easier.

“It’s sometimes difficult for a clinician to know whether a baby actually has neonatal sepsis because it can present very subtly and not always with the same symptoms,” Bekker explains.

The blood culture is the gold standard for diagnosing neonatal sepsis, but Bekker says only around 10% of blood cultures will grow an organism even if the baby has sepsis, making it very difficult to get a diagnosis. “And because it’s such an aggressive disease and a baby can die very quickly from it, clinicians tend to rather over-treat than under-treat. That is correct but, just as important as it is to start antibiotics quickly, it’s important to stop them if they are not necessary. The NeoSeps Severity score will help doctors identify babies that are at very high risk from sepsis and those that would need treatment immediately.

Velaphi says a major challenge is the time it takes for an outcome of the blood culture and the general protocol is to start antibiotics immediately. Waiting between 24 to 48 hours can be too late for a child who may have sepsis and could die. On the other hand, antibiotics may be given to children who do not have sepsis and this adds to the frequency of antibiotic resistance. “So, you are damned if you do and you are damned if you don’t.”

He says we need new diagnostic tests that are reliable and that have a high degree of sensitivity and specificity. “We need antibiotics that work to reduce mortality,” he adds.

Republished from Spotlight under a Creative Commons NoDerivatives 4.0 Licence.

Source: Spotlight

Categories : Antibiotics GeneticsTags :

Scientists Discover New Antibiotic Resistance Genes in Common Bacteria

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Photo by CDC on Unsplash

Genes that make bacteria resistant to antibiotics are much more widespread in our environment than was previously realised. A new study published in Microbiome shows that bacteria in almost all environments carry resistance genes, with a risk of them spreading and aggravating the problem of bacterial infections that are untreatable with antibiotics.

“We have identified new resistance genes in places where they have remained undetected until now. These genes can constitute an overlooked threat to human health,” says Erik Kristiansson, a professor in the Department of Mathematical Sciences.

According to the World Health Organisation (WHO), antibiotic resistance is one of the greatest threats to global health. When bacteria become resistant to antibiotics, it becomes difficult or impossible to treat illnesses such as pneumonia, wound infections, tuberculosis and urinary tract infections. According to the UN Interagency Coordination Group on Antimicrobial Resistance (IACG) 700,000 people die each year from infections caused by antibiotic-resistant bacteria.

Looking for resistance genes in new environments

The genes that make bacteria resistant have long been studied, but the focus has traditionally been on identifying those resistance genes that are already prevalent in pathogenic bacteria. Instead, in the new study from Sweden, researchers have looked at large quantities of DNA sequences from bacteria to analyse new forms of resistance genes in order to understand how common they are. They have traced the genes in thousands of different bacterial samples from different environments, in and on people, in the soil and from sewage treatment plants. The study analysed 630 billion DNA sequences in total.

“The data requires a great deal of processing before information can be obtained. We have used metagenomics, a methodology, that allows vast quantities of data to be analysed,” says Juan Inda Díaz, a doctoral student in the Department of Mathematical Sciences, and the article’s lead author.

The study showed that the new antibiotic resistance genes are present in bacteria in almost all environments. This also includes human microbiomes and, more alarmingly, pathogenic bacteria, which can lead to more infections that are difficult to treat. The researchers found that resistance genes in bacteria that live on and in humans and in the environment were ten times more abundant than those previously known. And of the resistance genes found in bacteria in the human microbiome, 75% were not previously known at all.

The researchers stress the need for more knowledge about the problem of antibiotic resistance.

“Prior to this study, there was no knowledge whatsoever about the incidence of these new resistance genes. Antibiotic resistance is a complex problem, and our study shows that we need to enhance our understanding of the development of resistance in bacteria and of the resistance genes that could constitute a threat in the future,” says Kristiansson.

Preventing bacterial outbreaks in healthcare

The research team is currently working on integrating the new data into the international EMBARK project (Establishing a Monitoring Baseline for Antibiotic Resistance in Key environments). The project is coordinated by Johan Bengtsson-Palme, an assistant professor in the Department of Life Sciences at Chalmers, and aims to take samples from sources such as wastewater, soil and animals to get an idea of the way in which antibiotic resistance is spreading between humans and the environment.

“It is essential for new forms of resistance genes to be taken into account in risk assessments relating to antibiotic resistance. Using the techniques we have developed enables us to monitor these new resistance genes in the environment, in the hope that we can detect them in pathogenic bacteria before they are able to cause outbreaks in a healthcare setting,” says Bengtsson-Palme.

The method used by the researchers is called metagenomics, and is not new, but so far has not been used to analyse new types of antibiotic resistance genes in such large quantities. Metagenomics is a method of studying the metagenome, which is the complete gene set of all different organisms in a given sample or within a given environment. Using the method, it is also possible to study microorganisms that cannot be grown in a lab.

Source: Chalmers Institute of Technology

Categories : Antibiotics Healthcare Politics and RegulationsTags :

SA one of Many Countries Failing to Combat Antimicrobial Resistance, International Review Finds

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Methicillin resistant Staphylococcus aureus (MRSA) bacteria, the bane of hospital infection control strategies. Image by CDC on Unsplash.

Governments around the world must do more to tackle the growing threat of antimicrobial-resistant infections, new research suggests – with South Africa falling quite short in the rankings.

The review, published in The Lancet Infectious Diseases, assessed national action plans developed by more than 100 countries to tackle the threat from antimicrobial resistance (AMR). It comprehensively graded international AMR efforts and national action plans and generate comparable quantitative results across countries and regions.

National action plans focus on designing policies to curb AMR and devising tools to implement the policies – but they do not adequately factor in monitoring and evaluation.

The new research, carried out by experts at the universities of Leeds, Edinburgh and Hamburg, is the first large-scale analysis of these plans. They were designed after encouragement from the World Health Organisation, which has declared AMR one of the top 10 public health threats facing humanity.

Lead author Jay Patel, undergraduate dental student in the University of Leeds’ School of Dentistry, said: “Our analysis showed that countries were highly focused on designing AMR policies, and thinking about what tools would be required to implement those, but they generally did not consider how they would monitor and evaluate the impact of those efforts.

“This suggests that the international response may be inadequate to meet the scale and severity of AMR. This is particularly concerning in low and middle-income countries, where action plan activities often lack sustainable funding – relying instead on funds from foreign donors and philanthropies.

“The available evidence also suggests that simply developing a national action plan may not necessarily mean a country is more prepared to respond to the threat of AMR.

“Our study shows that the global response to AMR, and preparedness for the predicted challenges of AMR, require improvement in all locations around the world.”

The research team says governments across the world must strengthen their responses to AMR.

In 2017, the World Health Organization encouraged member states to develop national action plans stipulating how countries would tackle AMR. More than 100 countries have produced action plans, with several being implemented – but there had been no global analysis of the contents of these plans.

The 114 action plans, which were created in 2020-21, were evaluated against 54 elements, such as education, stewardship, and accountability, and each awarded a score out of 100. A mean score out of 100 for each country’s plan was then taken from these results.

The findings

At 43 points for AMR governance, South Africa falls far short of the top score of 85, and rather closer to the lowest score of 29. Reproduced from The Lancet. Figure 2b, Patel et al., 2023. (Open Access)

Norway’s response was the highest scoring with 85, followed by the USA with 84 and the UK with 83. The lowest scoring countries were Ukraine and Sierra Leone with 29 points each, and Barbados and Micronesia with 28 points. With 43 points, South Africa trailed behind Brazil, Namibia, Rwanda and Egypt – and received 0 for research and development as well as the effectiveness of its monitoring and evaluation.

The study found that across all plans, there was a greater focus on policy design and implementation tools, but efforts to monitor and evaluate activities are generally poorly-considered.

Of all areas evaluated, accountability and feedback mechanisms were the joint-lowest scoring, followed by education.

Training and professional education across human health, veterinary, and agricultural sectors were insufficient in many countries, with several lacking a sustainable workforce strategy to deliver antimicrobial stewardship policies.

Countries scored well on participation, demonstrating a shared awareness that AMR can only be successfully addressed through engagement with multiple sectors spanning human, animal and environmental health. Infection prevention and control was frequently recognised as a critical objective.

Source: University of Leeds

Categories : Antibiotics New Compounds and TreatmentsTags :

Scientists Use Modified Peptides to Create New Class of Antibiotics

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Photo by CDC on Unsplash

New antibiotics are urgently needed to tackle resistant bacteria. Researchers at the University of Zurich and the company Spexis have now modified the chemical structure of naturally occurring peptides to develop antimicrobial molecules that bind to novel targets in the bacteria’s metabolism.

In a study recently published in Science Advances, chemist Oliver Zerbe, head of the NMR facilities at the University of Zurich now discusses the development of a highly effective class of antibiotics that fight Gram-negative bacteria in a novel way.

The WHO classifies this group of bacteria as extremely dangerous. The group, whose resistance is particularly high due to their double cell membrane, includes carbapenem-resistant enterobacteria, for example.

Natural peptide chemically optimised

The starting point for the researchers’ study was a naturally occurring peptide called thanatin, which insects use to fend off infections. Thanatin disrupts an important lipopolysaccharide transport bridge between the outer and inner membrane of Gram-negative bacteria, as revealed a few years ago in a study by now retired UZH professor John Robinson. As a result, these metabolites build up inside the cells, and the bacteria perish. However, thanatin isn’t suitable for use as an antibiotic drug, among other things due to its low effectiveness and because bacteria quickly become resistant to it.

The researchers therefore modified the chemical structure of thanatin to enhance the peptide’s characteristics. “To do this, structural analyses were essential,” says Zerbe. His team synthetically assembled the various components of the bacterial transport bridge and then used nuclear magnetic resonance (NMR) to visualize where and how thanatin binds to and disrupts the transport bridge. Using this information, researchers from Spexis AG planned the chemical modifications that were necessary to boost the peptide’s antibacterial effects. Further mutations were made to increase the molecule’s stability, among other things.

Effective, safe and immune to resistance

The synthetic peptides were then tested in mice with bacterial infections – and yielded outstanding results. “The novel antibiotics proved very effective, especially for treating lung infections,” says Zerbe. “They are also highly effective against carbapenem-resistant enterobacteria, where most other antibiotics fail.” In addition, the newly developed peptides aren’t toxic or harmful to the kidneys, and they also proved stable in the blood over a longer period – all of which are properties that are required for gaining approval as a drug. However, further preclinical studies are needed before the first tests in humans can begin.

When choosing the most promising peptides for their study, the researchers made sure that they would also be effective against bacteria that have already developed resistance to thanatin. “We’re confident this will significantly slow down the development of antibacterial resistance,” says Zerbe. “We now have the prospect of a new class of antibiotics becoming available that is also effective against resistant bacteria.”

Source: University of Zurich

Categories : Antibiotics Diseases, Syndromes and ConditionsTags :

Cholera Mutations Reveals Secrets of Antimicrobial Resistance

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Scanning electron microscope image of Vibrio cholerae bacteria, which infect the digestive system.
Zeiss DSM 962 SEM
T.J. Kirn, M.J. Lafferty, C.M.P Sandoe and R.K. Taylor, 2000, “Delineation of pilin domains required for bacterial association into microcolonies and intestinal colonization”, Molecular Microbiology, Vol. 35(4):896-910
Copyright: Darthmouth College Electron Microscope Facility / These images are in the public domain

The natural ability of bacteria to adapt to various environmental stimuli can also make them resistant to drugs that would kill or slow their growth. In an article published in PLoS Genetics, microbiologist Dr Salvador Almagro-Moreno uncovers the evolutionary origins of antimicrobial resistance (AMR) in bacteria. His studies on the cholera-causing bacterium Vibrio cholerae show that mutations in a bacterial membrane protein, OmpU, are linked to developing antimicrobial resistance.

These findings provide insight into deciphering what conditions must occur for infectious agents to become resistant.

Dr Almagro-Moreno studied genetic variants of a protein found in bacterial membranes called OmpU. Using computational and molecular approaches, his team found that several OmpU mutations in the cholera bacteria led to resistance to numerous antimicrobial agents. This resistance included antimicrobial peptides that act as defences in the human gut. The researchers found that other OmpU variants did not provide these properties, making the protein an ideal system for deciphering the specific processes that occur to make some bacteria resistant to antimicrobials.

By comparing resistant and antibiotic sensitive variants, the researchers were able to identify specific parts of OmpU associated with the emergence of antibiotic resistance. They also discovered that the genetic material encoding these variants, along with associated traits, can be passed between bacterial cells, increasing therisk of spreading AMR in populations under antibiotic pressure.

By understanding how mutations occur, researchers can better understand and develop therapeutics to combat resistant infections. Dr Almagro-Moreno is also looking at environmental factors such as pollution and warming of the oceans, as possible causes of resistant bacteria. “We are studying the genetic diversity of environmental populations, including coastal Florida isolates, to develop a new approach to understanding how antimicrobial resistance evolves,” he explained.

Understanding the bacteria that causes cholera, an acute diarrhoeal illness linked to infected water and foods, has global implications. The disease sickens up to 4 million people worldwide and severe cases can cause death within hours.

Source: University of Central Florida

Categories : Antibiotics Diseases, Syndromes and ConditionsTags :

Antibiotic Regimen may be Ineffective in TB Meningitis

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Tuberculosis bacteria
Tuberculosis bacteria. Credit: CDC

Research in animal models published in Nature Communications shows that an approved antibiotic regimen for multidrug-resistant (MDR) tuberculosis (TB) may not work for TB meningitis. Limited human studies also provide evidence that a new combination of drugs is needed to develop effective treatments for TB meningitis due to MDR strains.

In the study from Johns Hopkins Children’s Center, the investigators showed that the Food and Drug Administration (FDA)-approved regimen of three antibiotics – bedaquiline, pretomanid and linezolid (BPaL) – used for treating TB of the lungs due to MDR strains, is not effective in treating TB meningitis because bedaquiline and linezolid struggle to cross the blood-brain barrier.

Tuberculosis, caused by the bacteria Mycobacterium tuberculosis, is a global public health threat. About 1%–2% of TB cases progress into TB meningitis, the worst form of TB, which leads to an infection in the brain that causes increased fluid and inflammation.

“Most treatments for TB meningitis are based on studies of treatments for pulmonary TB, so we don’t have good treatment options for TB meningitis,” explains Sanjay Jain, M.D., senior author of the study and director of the Johns Hopkins Medicine Center for Infection and Inflammation Imaging Research.

In 2019, the FDA approved the BPaL regimen to treat MDR strains of TB, specifically those that lead to pulmonary TB. However, there are limited data on how well these antibiotics cross the blood-brain barrier.

In an effort to learn more, the research team synthesised a chemically identical and imageable version of the antibiotic pretomanid. They conducted experiments in mouse and rabbit models of TB meningitis using positron emission tomography (PET) imaging to noninvasively measure pretomanid penetration into the central nervous system as well as using direct drug measurements in mouse brains. In both models, researchers say PET imaging demonstrated excellent penetration of pretomanid into the brain or the central nervous system. However, the pretomanid levels in the cerebrospinal fluid (CSF) that bathes the brain were many times lower than in the brains of mice.

“When we have measured drug concentrations in the spinal fluid, we have found that many times they have no relation to what’s happening in the brain,” says Elizabeth Tucker, MD, a study first author and an assistant professor of anaesthesiology and critical care medicine. “This finding will change how we interpret data from clinical trials and, ultimately, treat infections in the brain.”

Next, researchers measured the efficacy of the BPaL regimen compared with the standard TB treatment for drug-susceptible strains, a combination of the antibiotics rifampin, isoniazid and pyrazinamide. Results showed that the antibacterial effect in the brain using the BPaL regimen in the mouse model was about 50 times lower than the standard TB regimen after six weeks of treatment, likely due to restricted penetration of bedaquiline and linezolid into the brain. The bottom line, says Jain, is that the “regimen that we think works really well for MDR-TB in the lung does not work in the brain.”

In another experiment involving healthy participants, three male and three female aged 20–53 years, first-in-human PET imaging was used to show pretomanid distribution to major organs, according to researchers.

Similar to the work with mice, this study revealed high penetration of pretomanid into the brain or central nervous system with CSF levels lower than those seen in the brain. “Our findings suggest pretomanid-based regimens, in combination with other antibiotics active against MDR strains with high brain penetration, should be tested for treating MDR-TB meningitis,” says study author Xueyi Chen, MD, a paediatric infectious diseases fellow, who is now studying combinations of such therapies.

Limitations included the small quantities of the imageable version of pretomanid per subject (micrograms) used. However, current evidence suggests that studies with small quantities of a drug are a reliable predictor of the drug biodistribution.

Source: Johns Hopkins Medicine

Categories : Diseases, Syndromes and Conditions New Compounds and TreatmentsTags :

Turning M. Pneumoniae into ‘Living Medicine’

On By ModernMedia
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