Rapid detection of antibiotic-resistant bacteria
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PORTABLE FLUORESCENCE READER DEVICE
view moreCREDIT: ARNAB DUTTA
A paper-based platform developed by researchers at the Indian Institute of Science (IISc) and Jawaharlal Nehru Centre for Advanced Scientific Research (JNCASR) could help quickly detect the presence of antibiotic-resistant, disease-causing bacteria.
One of mankind's greatest challenges has been the rise of disease-causing bacteria that are resistant to antibiotics. Their emergence has been fuelled by the misuse and overuse of antibiotics.
A handful of such bacteria – including E. coli and Staphylococcus aureus – have caused over a million deaths, and these numbers are projected to rise in the coming years, according to the World Health Organisation. Timely diagnosis can improve the efficiency of treatment.
“Generally, the doctor diagnoses the patient and gives them medicines. The patient then takes it for 2-3 days before realising that the medicine is not working and goes back to the doctor. Even diagnosing that the bacteria is antibiotic-resistant from blood or urine tests takes time. We wanted to reduce that time-to-diagnosis,” says Uday Maitra, Professor at the Department of Organic Chemistry, IISc.
In a paper published in ACS Sensors, Maitra’s lab and collaborators have addressed this challenge. They have developed a rapid diagnosis protocol that uses a luminescent paper-based platform to detect the presence of antibiotic-resistant bacteria.
There are different ways by which a bacterium becomes resistant to antibiotics. In one, the bacterium evolves, and can recognise and eject the medicine out of its cell. In another, the bacterium produces an enzyme called β-lactamase, which hydrolyses the β-lactam ring – a key structural component of common antibiotics like penicillin and carbapenem – rendering the medication ineffective.
The approach developed by the IISc and JNCASR team involves incorporating biphenyl-4-carboxylic acid (BCA) within a supramolecular hydrogel matrix containing terbium cholate (TbCh). This hydrogel normally emits green fluorescence when UV light is shined on it.
"In the lab, we synthesised an enzyme-substrate by tethering BCA to the cyclic [β-lactam] ring that is a part of the antibiotic. When you mix this with TbCh hydrogel, there is no green emission as the sensitiser is ‘masked,’” explains Arnab Dutta, PhD student in the Department of Organic Chemistry, IISc, and lead author of the paper. “In the presence of β-lactamase enzyme, the gel will produce green emission. β-lactamase enzyme in the bacteria is the one that cuts open the drug, destroys, and unmasks the sensitiser BCA. So, the presence of β-lactamase is signalled by green emission.” The luminescence signals the presence of antibiotic-resistant bacteria, and the intensity of the luminescence indicates the bacterial load. For non-resistant bacteria, the green intensity was found to be extremely low, making it easier to distinguish them from resistant bacteria.
The next step was to find a way to make the technology inexpensive. Currently used diagnostics instruments are costly, which drives up the price for testing.
The team collaborated with a Tamil Nadu-based company called Adiuvo Diagnostics to design a customised, portable and miniature imaging device, named Illuminate Fluorescence Reader. Infusing the hydrogel in a sheet of paper as the medium reduced the cost significantly. The instrument is fitted with different LEDs that shine UV radiation as required. Green fluorescence from the enzyme is captured by a built-in camera, and a dedicated software app measures the intensity, which can help quantify the bacterial load.
The team from IISc tied up with Jayanta Haldar’s research group from JNCASR to check their approach on urine samples. “We used samples from healthy volunteers and added pathogenic bacteria to mimic Urinary Tract Infections. It successfully produced the outcome within two hours,” explains Maitra.
As the next step, the researchers plan to tie up with hospitals to test this technology with samples from patients.
Schematic depicting the detection/differentiation of antibiotic-resistance bacteria
CREDIT
Arnab Dutta
JOURNAL
ACS Sensors
ARTICLE TITLE
Augmenting Antimicrobial Resistance Surveillance: Rapid Detection of β-Lactamase-Expressing Drug-Resistant Bacteria through Sensitized Luminescence on a Paper-Supported Hydrogel Arnab Dutta, Sudip Mukherjee, Jayanta Haldar, and Uday Maitra*
Superbug killer: New synthetic molecule highly effective against drug-resistant bacteria
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OVERVIEW AND CLOSE-UP OF CRESOMYCIN BOUND TO THE BACTERIAL RIBOSOME OF THERMUS THERMOPHILUS.
view moreCREDIT: YURY POLIKANOV/UNIVERSITY OF ILLINOIS CHICAGO
A new antibiotic created by Harvard researchers overcomes antimicrobial resistance mechanisms that have rendered many modern drugs ineffective and are driving a global public health crisis.
A team led by Andrew Myers, Amory Houghton Professor of Chemistry and Chemical Biology, reports in Science that their synthetic compound, cresomycin, kills many strains of drug-resistant bacteria, including Staphylococcus aureus and Pseudomonas aeruginosa.
“While we don’t yet know whether cresomycin and drugs like it are safe and effective in humans, our results show significantly improved inhibitory activity against a long list of pathogenic bacterial strains that kill more than a million people every year, compared with clinically approved antibiotics,” Myers said.
The new molecule demonstrates an improved ability to bind to bacterial ribosomes, which are biomolecular machines that control protein synthesis. Disrupting ribosomal function is a hallmark of many existing antibiotics, but some bacteria have evolved shielding mechanisms that prevent legacy drugs from working.
Cresomycin is one of several promising compounds that Myers’ team has developed, with the goal of helping win the war against superbugs. They’ll continue advancing these compounds through preclinical profiling studies, supported by a $1.2 million grant from Combating Antibiotic-Resistant Bacteria Biopharmaceutical Accelerator (CARB-X). A Boston University-based global nonprofit partnership, CARB-X is dedicated to supporting early-stage antibacterial research and development.
The Harvard team’s new molecule draws inspiration from the chemical structures of lincosamides, a class of antibiotics that includes the commonly prescribed clindamycin. Like many antibiotics, clindamycin is made via semisynthesis, in which complex products isolated from nature are modified directly for drug applications. The new Harvard compound, however, is fully synthetic and features chemical modifications that cannot be accessed through existing means.
“The bacterial ribosome is nature’s preferred target for antibacterial agents, and these agents are the source of inspiration for our program,” said co-author Ben Tresco, a Kenneth C. Griffin Graduate School of Arts and Sciences student. “By leveraging the power of organic synthesis, we are limited almost only by our imagination when designing new antibiotics.”
Bacteria can develop resistance to ribosome-targeting antibiotic drugs by expressing genes that produce enzymes called ribosomal RNA methyltransferases. These enzymes box out the drug components that are designed to latch onto and disrupt the ribosome, ultimately blocking the drug’s activity.
To get around this problem, Myers and team engineered their compound into a rigidified shape that closely resembles its binding target, giving it a stronger grip on the ribosome. The researchers call their drug “pre-organized” for ribosomal binding because it doesn’t need to expend as much energy conforming to its target as existing drugs must do.
The researchers arrived at cresomycin using what they call component-based synthesis, a method pioneered by the Myers lab that involves building large molecular components of equal complexity and bringing them together at late stages – like pre-building sections of a complicated LEGO set before assembling them. This modular, completely synthetic system allows them to make and test not just one, but hundreds of target molecules, greatly speeding up the drug discovery process.
The stakes are clear. “Antibiotics form the foundation on which modern medicine is built,” said co-author and graduate student Kelvin Wu. “Without antibiotics, many cutting-edge medical procedures like surgeries, cancer treatments, and organ transplants, cannot be done.”
Myers’ component-based synthesis research received early support from Harvard’s Blavatnik Biomedical Accelerator, part of the Office of Technology Development, which awarded funding to Myers’ lab in 2013 to enable testing of drug compounds. The Office of Technology Development protected the Myers Research Group’s innovations and, along with the Blavatnik Biomedical Accelerator, will support the research team for the duration of the CARB-X agreement. The newly awarded CARB-X funding allows the researchers to continue profiling and optimizing drug leads.
“Funding and other support from groups like the Blavatnik Biomedical Accelerator and CARB-X are essential for the discovery and development of new antibiotics,” said Curtis Keith, the Harvard accelerator’s chief scientific officer. “These innovations from the Myers Research Group have the potential to yield new drugs that will one day meet a global health need.”
The published work was supported by the National Institutes of Health and the National Science Foundation.
JOURNAL
Science
METHOD OF RESEARCH
Experimental study
SUBJECT OF RESEARCH
Cells
ARTICLE TITLE
An antibiotic preorganized for ribosomal binding overcomes antimicrobial resistance
ARTICLE PUBLICATION DATE
16-Feb-2024
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