Monday, November 21, 2022

How To Test For Antibiotic Resistance

What You Can Do

New Test Detects Antibiotic Resistance in Minutes

To help fight antibiotic resistance and protect yourself against infection:

  • Don’t take antibiotics unless you’re certain you need them. An estimated 30% of the millions of prescriptions written each year are not needed. Always ask your doctor if antibiotics will really help. For illnesses caused by viruses — common colds, bronchitis, and many ear and sinus infections — they won’t.
  • Finish your pills. Take your entire prescription exactly as directed. Do it even if you start feeling better. If you stop before the infection is completely wiped out, those bacteria are more likely to become drug-resistant.
  • Get vaccinated. Immunizations can protect you against some diseases that are treated with antibiotics. They include tetanus and whooping cough.
  • Stay safe in the hospital. Antibiotic-resistant bacteria are commonly found in hospitals. Make sure your caregivers wash their hands properly. Also, ask how to keep surgical wounds free of infection.

Definition Of Germs & Antimicrobials

Antimicrobial resistance does not mean our body is resistant to antibiotics or antifungals. It means the bacteria or fungi causing the infection are resistant to the antibiotic or antifungal treatment.

  • Germs are microbesvery small living organisms including bacteria, fungi, parasites, and viruses.
  • Most germs are harmless and even helpful to people, but some can cause infections. Harmful germs are called pathogens.
  • Antimicrobials is a term used to describe drugs that treat many types of infections by killing or slowing the growth of pathogens causing the infection. The content on this webpage does not include resistance to antivirals or antiparasitics.
  • Bacteria cause infections such as strep throat, foodborne illnesses, and other serious infections. Antibiotics treat bacterial infections.
  • Fungi cause infections like athletes foot, yeast infections, and other serious infections. Antifungals treat fungal infections.
  • People sometimes use antibiotic and antimicrobial interchangeably.

Patients should always be promptly treated with antibiotics when the drugs are needed for infections and to treat .

Optical Or Microscopic Methods

Choi et al. have developed a rapid antimicrobial susceptibility testing system, dRAST. It can determine the AR from a positive blood culture bottle in 6 h . The sample is mixed with agarose and inoculated into a well of a plastic microchip. Addition of cultivation medium forms a liquid bridge between the growth chamber and the satellite well, which contains the antibiotic agent. Using microscopic detection of bacterial colony formation in agarose, the total time-to-result was only 6 h with a wide range of bacterial concentrations. The tested clinical isolates included 16 Gram-negative species and seven Gram-positive species, and the dRAST system agreed with a standard microdilution test with an accuracy rate of 91.11% .

Matsumoto et al. described a microfluidic channel method for rapid AST for P. aeruginosa by automated microscopic detection of cell number and cell morphology . Their Drug Susceptibility Testing Microfluidic device consisted of five sets of four microfluidic channels and allowed simultaneous microscopic observation. Susceptibilities to the antibiotics were evaluated by the differences in cell number and shape between drug-treated and control cells. Hundred and one clinically isolated strains of P. aeruginosa tested with DSTM correlated strongly with the results obtained using the conventional microbroth dilution method . This system waits for applicability testing with other organisms.

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Nucleic Acid Amplification Technology In Ast

The first generation âmolecular testsâ such as restriction fragment length polymorphism, pulsed-field electrophoresis, multiple locus tandem repeat analysis, multi-locus sequence typing and virulence genotyping were suitable rather for typing and outbreak investigation than for AST. Since these technologies require a high amount of purified nucleic acid, they do not allow rapid diagnostics. However, hybridization-based approaches and molecular beacon systems have persisted and are creatively combined with NAAT technologies.

Why Is Antibiotic Sensitivity Testing Done

Antibiotic resistance

âAntibiotic sensitivity testing is often done when you have an infection that may be resistant to antibiotics. This means that antibiotics are less effective or don’t affect certain bacteria. This makes it more difficult to treat bacterial infections and illnesses.

Here are some infections that may be antibiotic-resistant or are difficult to treat: â

  • Salmonella typhi or typhoid fever
  • Clostridioides difficile or C. diff

There are almost 3 million antibiotic-resistant infections every year. More than 35,000 people die from these infections.â

Antibiotic sensitivity testing can help find suitable treatments for these antibiotic-resistant infections and prevent further complications.

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Normal And Critical Findings

For disk diffusion, measuring the zone of inhibition is done by using a dedicated caliper. Correctly measure the diameter by the edges of the inhibition zone. For MIC panels, reading each set of wells for an antibiotic drug is done. MIC determination is by either a clear or slight whiteness on the well. Reporting the results of the inhibition zones and MIC breakpoints is made using either the terms susceptible or resistant based on the set cut-off range for zone diameter in the nearest whole millimeter and microgram per milliliter, respectively. The Clinical Laboratory Standards Institute and the European Committee on Antimicrobial Susceptibility Testing developed expert-approved guidelines on breakpoints for reporting results of these methods .

Selection Of Drugs For Routine Testing

The laboratory must test and report the antimicrobial agents that are most appropriate for the organism isolated, for the site of the infection, and the institution’s formulary . The CLSI provides tables that list the antimicrobial agents appropriate for testing members of the Enterobacteriaceae, Pseudomonas, and other gram-negative glucose nonfermenters, staphylococci, enterococci, streptococci, Haemophilus species, etc. . The listings include recommendations for agents that are important to test routinely, and those that may be tested or reported selectively based on the institution’s formulary.

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Antimicrobial Resistance Laboratory Network

  • CDCs AR Lab Network provides nationwide lab capacity to rapidly detect antimicrobial resistance in humans related to health care, food, community, and the environment, and inform local responses to prevent spread and protect people
  • It includes labs in 50 states, several cities, and Puerto Rico, including seven regional labs and the National Tuberculosis Molecular Surveillance Center
  • Labs test patient samples to detect germs, including Acinetobacter, Candida, Salmonella, Neisseria gonorrhea, and more
  • Learn more: CDCs AR Lab Network website

How Is It Used

New test detects antibiotic resistance in minutes

Susceptibility testing is used to determine which antimicrobials will inhibit the growth of the bacteria or fungi causing a specific infection. The results from this test will help a healthcare practitioner determine which drugs are likely to be most effective in treating a person’s infection.

Some types of infections may require testing because the bacteria or fungi isolated from an infection site are known to have unpredictable susceptibility to the drugs usually used to treat them. Some examples include staphylococci and Pseudomonas aeruginosa.

Sometimes there may be more than one type of pathogen isolated from an infected site, such as a wound infection. Susceptibility testing may be used to determine which antibiotic or antibiotic combinations will be most effective in treating all the different types of bacteria causing the infection.

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Future Technologies Under Commercialization

Mass spectrometry is likely to become tightly integrated into other AST technologies, especially in the diagnostics of septicaemia. In the MALDI-TOF Direct-On-Target Microdroplet Growth Assay , sample droplets are spotted directly onto disposable MS-target plates, incubated for 3â4 h and then analyzed with MS . Screening panels for ESBL and AmpC β-lactamases of enterobacteria are already available . The fast progress in microfluidics, biosensor technologies, isothermal amplification-based NAAT, and immunodetection has recently provided several potent systems which may eventually change the paradigms of AST.

Gradientech’s QuickMIC system combines microfluidics with automated time-lapse photomicrography to follow growth inhibition along a linear drug gradient. It measures the greyscale intensity changes in the images caused by the formation of microcolonies and provides AST in 2â5 h . The system is currently seeking CE-IVD marking and FDA approval for AST in blood samples.

Q-Linea ASTar® applies time-lapse microscopy to fully automated monitoring of blood cultures as well as preparation and monitoring of bacterial isolates. It processes 12 samples at a time and 50 samples a day, delivering true MIC values for up to 48 antibiotics within 6 h. The system does not perform ID, but it can be connected to any ID system. Clinical trials will start in 2020.

Glossary Of Terms Related To Antibiotic Resistance

CDC works with federal, state, and local partners to reduce antibiotic resistance and protect the publics health. This work includes investigating outbreaks caused by resistant bacteria, identifying new antibiotic resistance threats, and recommending ways to help prevent illnesses and outbreaks caused by resistant bacteria.

The National Antimicrobial Resistance Monitoring System assists in outbreak investigations by testing bacteria from sick people, animals, and retail meats for antibiotic resistance. When paired with information collected during interviews with sick people about what they ate or were exposed to before becoming ill, resistance data can provide investigators with clues about the source of outbreaks.

This glossary defines some key terms related to antibiotic resistance that CDC uses to describe multistate outbreak investigations.

Antibiotic: A drug that kills or stops the growth of bacteria. Antibiotics are a type of antimicrobial. Penicillin and ciprofloxacin are examples of antibiotics.

Antibiotic resistance: Antimicrobial resistance of bacteria.

Antibiotic resistance testing : Laboratory testing performed on bacteria to find out if they are resistant to one or more antibiotics.

Antimicrobial: A substance, such as an antibiotic, that kills or stops the growth of microbes, including bacteria, fungi, or viruses. Antimicrobials are grouped according to the microbes they act against . Also referred to as drugs.

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What Novel Diagnostic Strategies And Approaches Can Be Implemented To Identify Antimicrobial Drug Resistance What Parameters Need To Be Considered When Developing Phenotypic And Genotypic Tests For The Rapid And Accurate Detection Of Antimicrobial Resistance And When Selecting Useful Therapeutic Agents

There are several novel strategies that can be implemented. It is well established that outpatient visits for respiratory infections are the setting in which the most unnecessary antimicrobials are prescribed. Near-patient testing to rule out bacterial infection or confirm viral aetiology may be a simple approach to reducing the unnecessary use of antimicrobials.

In the setting of serious bacterial infection, rapid phenotypic methods are needed. The ideal method would provide definitive results directly from the clinical specimen within 58 h of specimen collection with these performance characteristics, the second dose of antibiotics administered could be directed therapy.

Although phenotypic methods to detect both resistance and susceptibility to antibiotics are desired, conventional growth-based systems are slow, and attempts to increase the doubling time of microorganisms have resulted in very limited success. Thus, there is a need to focus on the development of new methods to detect this growth with improved sensitivity, an example of which could be measuring metabolic end products as a surrogate for microbial growth. In addition, methods that measure the host response to therapy are desired. For many infections, the optimal duration of antibiotic treatment is not known, but measuring the host response could be an effective tool to establish an appropriate end point to antimicrobial therapy.

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J.O’G.

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When Is It Ordered

Staphylococcus aureus

Susceptibility testing is usually ordered at the same time as a culture of a potentially infected site, such as a wound, urine, or blood culture. However, the test will usually only be performed when the culture is positive for one or more pathogens. The test may also be ordered when an infection does not respond to treatment to see if the pathogen has developed resistance and to determine which antimicrobial drug would be more effective in treating the infection.

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Are There Other Ways Of Testing For Resistance

Sometimes molecular methods are used to look for changes in a microbe’s genetic material that enables it to grow in the presence of certain antimicrobial drugs. For instance, methicillin-resistant Staphylcoccus aureus contain the mecA gene that confers resistance to the antibiotics methicillin, oxacillin, nafcillin, and dicloxacillin. Detection of the mecA gene using a molecular based test allows the rapid detection of MRSA prior to culturing the bacteria. Someone carrying this microbe in their nasal passages can be isolated from other patients in the hospital so that the resistant staph are not transmitted to others.

What Is An Antibiotic Sensitivity Test

Antibiotics are medicines used to fight bacterial infections. There are different types of antibiotics. Each type is only effective against certain bacteria. An antibiotic sensitivity test can help find out which antibiotic will be most effective in treating your infection.

The test can also be helpful in finding a treatment for antibiotic-resistant infections. Antibiotic resistance happens when standard antibiotics become less effective or ineffective against certain bacteria. Antibiotic resistance can turn once easily treatable diseases into serious, even life-threatening illnesses.

Other names: antibiotic susceptibility test, sensitivity testing, antimicrobial susceptibility test

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Emergence Of Antimicrobial Resistance And The Rationale For Performing Susceptibility Testing

The performance of antimicrobial susceptibility testing by the clinical microbiology laboratory is important to confirm susceptibility to chosen empirical antimicrobial agents, or to detect resistance in individual bacterial isolates. Empirical therapy continues to be effective for some bacterial pathogens because resistance mechanisms have not been observed e.g., continued penicillin susceptibility of Streptococcus pyogenes . Susceptibility testing of individual isolates is important with species that may possess acquired resistance mechanisms .

The Fight Against Amr

Tests for Rapid Detection of Antibiotic Resistant Bacteria – ICAAC 2014

The last class of antibiotics to be successfully introduced as a treatment was adapted in 1987, and antibiotic drugs can take ten years or more to develop. Pharmaceutical companies rarely gravitate toward this class of research due to the associated expense and risk, but the lack of new antibiotics is a growing problem.

But tests to try and ascertain the antibiotic resistance of an infection arent the only option left in the fight against AMR. Several companies are focused on developing novel biotheraputics which could destroy even the most resilient bacterial infections.

Australian biotech firm Recce, for example, is working on developing a synthetic broad-spectrum antibiotic that uses a hydrophobic reaction to bind to the outer membrane of an infectious bacterium. This weakens the cell wall and causes internal pressure inside the bacterium to build, eventually causing it to explode. The bodys natural immune system can then clear away the remaining debris.

Bacteriophages are another option viruses that can infect and kill off bacteria, while leaving healthy cells unharmed. Bacteriophages were first discovered in 1915 and began to be commercialised in 1940, but interest in these therapies waned following the introduction of antibiotics.

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Innovative Tools Take Aim At Antibiotic

Maha Farhat spent months in 2007 tending to patients at a hospital in Durban, South Africa. Many were infected with HIV. But the infection that preyed on the then-medical-residents mind, and her patients, was caused not by a virus, but by a bacterium: Mycobacterium tuberculosis, the pathogen that causes tuberculosis. In particular, she was concerned about strains that are resistant to common antibiotics.

Although immunocompromised individuals are especially susceptible to tuberculosis, the infection isnt unique to people with HIV: M. tuberculosis claimed 1.4 million lives worldwide in 2019, 208,000 of whom had HIV. Tuberculosis was briefly superseded by COVID-19, but its still the top infectious-disease killer globally, says Farhat, now a physician and bioinformatician at Harvard University in Boston, Massachusetts. Drug-resistant forms of tuberculosis are a major contributor to the problem.

Farhat and other researchers are turning to tools such as atomic force microscopy, genomics and machine learning to create point-of-care diagnostic tests that they hope will provide results in minutes, minimizing the use of incorrect or unnecessary prescriptions. An increase in rapidity is the most important advance needed, says clinical microbiologist Evgeny Idelevich at the University Medical Center Greifswald in Germany.

What Is Sensitivity Analysis

Sensitivity analysis, also called susceptibility testing, helps your doctor find the most effective antibiotic to kill an infecting microorganism. Infecting microorganisms are organisms such as bacteria or fungi that invade your body and cause an infection.

A sensitivity analysis is a test that determines the sensitivity of bacteria to an antibiotic. It also determines the ability of the drug to kill the bacteria.

The results from the test can help your doctor determine which drugs are likely to be most effective in treating your infection.

Doctors use sensitivity testing to determine the right antibiotic treatment for an infection and to monitor changes in bacterial resistance to antibiotics. Both are key to your care.

Many bacteria are resistant to common antibiotics. This means that the drug cant kill the bacteria. Sensitivity analysis is a useful tool to help quickly determine if bacteria are resistant to certain drugs.

Examples of antibiotic-resistant infections include:

Sensitivity analysis may be ordered if your infection doesnt respond to treatment.

This can help your doctor to see if the bacteria thats causing your infection has developed resistance. Your doctor can then determine which drug would be more effective in treating the infection.

Samples may be taken from:

  • inside the cervix
  • a pus-containing wound

Rare risks of taking a blood sample include:

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Can You Prevent Antibiotic Resistance

These steps may lower your risk of developing antibiotic resistance:

  • Only take antibiotics prescribed for you. Dont take someone elses medicine.
  • Follow your healthcare providers advice to treat your symptoms without antibiotics. Dont pressure your provider for an unnecessary prescription.
  • Set a reminder on your phone so you dont miss a dose. If you do forget to take your medicine, ask your provider what to do.
  • Take all of the medicine as prescribed, even if you feel better. If you stop an antibiotic too soon, bacteria can start to grow again, and they may develop resistance.
  • Wash your hands regularly. Good hygiene lowers your risk of getting a bacterial infection.

A note from Cleveland Clinic

Bacteria that develop antibiotic resistance dont respond to standard treatments. The result can be a bacterial infection thats difficult to treat. Antibiotic resistance is a worldwide health problem. To help prevent drug resistance, healthcare providers prescribe antibiotics only when needed. Overuse and misuse of antibiotics are top contributors to antibiotic resistance. Be sure to follow your providers instructions. Take antibiotics only when necessary and exactly as prescribed.

Last reviewed by a Cleveland Clinic medical professional on 06/23/2021.

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