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The WHO categorizes antibiotics in an attempt to combat antibiotic resistance

Ranking antibiotics to address bacterial drug resistance.)

On Tuesday, the World Health Organization (WHO) released the largest revision to the antibiotic section of the Essential Medicine List (EML) in over 40 years. A panel of international antibiotic experts have categorized antibiotics into three distinct groups – ACCESS, WATCH, and RESERVE – with each category having a specific set of guidelines as to their recommended use. The new EML includes 39 antibiotics that treat 21 common infections, and if the recommendations are found to be useful, this list will be broadened in the future to include other drugs and infections.

Two members from the McMaster University Michael G. DeGroote Institute for Infectious Disease Research (IIDR), Dr. Mark Loeb and Dr. Dominik Mertz, were on the expert panel and provided key opinions on this subject.

“Something we did in this meeting that hadn’t been done before was take a syndrome based approach,” said Dr. Mertz, an associate professor in the department of Medicine at McMaster University, “we looked at the most common infections and figured out the most reasonable choice of antibiotic to treat those pathogens.”

Dr. Mark Loeb, a professor in the department of Pathology and Molecular medicine adds, “We developed it by systematically reviewing the literature and guidelines to come up with a list that was then further vetted by an expert committee. This list provides prescribers with a reasonable choice of antibiotics based on the best evidence and helps to reduce antibiotics that may lead to resistance.”

The WHO recommends that drugs in the group 1 “ACCESS” category are to be widely available and affordable at all times, as they are used to treat various common infections. This group includes familiar antibiotics such as amoxicillin and penicillin, used to treat infections such as pneumonia.

Antibiotics in the group 2 “WATCH” category are classes of drugs which tend to have a higher resistance-developing potential, and are therefore only recommended to treat a specific, limited number of infections. An example of a drug from this category is ciprofloxacin, often used to treat upper respiratory tract infections (bacterial sinusitis) or other infections such as strep throat. Additionally the WHO recommends that the use of drugs in this category be “dramatically reduced” to avoid further instances of resistance.

The third and final category is the “RESERVE” antibiotics – considered “last resort” options. Antibiotics in this group – including colistin and some cephalosporins – are to be accessible but only used to treat highly specific patients and settings, and only when all alternatives have failed. This would include cases of life-threatening infections due to multidrug resistant pathogens.

When asked about the biggest challenge creating this list, Dr. Mertz replied, “The challenge was that for many infections there are multiple types of antibiotics that can be used. Therefore our goal was to identify the least problematic antibiotic that was the most effective in this situation to recommend.”

“It preserves antibiotics that should really be used selectively, and I think it’s an important list,” said Dr. Loeb. These changes aim to ensure that antibiotics are available when required, and that the right antibiotics are prescribed for the right infections. The hope is that this list will enhance treatment outcomes and reduce the instances of drug-resistant bacteria.

The “WHO model list of essential medicines” was launched in 1977, and many countries around the world have adopted the concept of essential medicines and have developed lists of their own, using the EML as a guide.