Antibiotic resistance and other consequences of treating medicines like candy

What is antibiotic resistance and where does it come from?

Antibiotic resistance is the ability of bacteria to survive despite the use of an antibiotic that previously worked. Resistance does not mean the body becomes immune to the drug, but that bacteria change or acquire defence mechanisms, so the antibiotic no longer kills them or stops their growth. Antibiotic resistance can result from genetic mutations in bacteria as well as the transfer of resistance genes between microorganisms, including across different species. Misuse also plays a major role: taking antibiotics without a clear indication, using too low a dose, stopping too early, taking breaks, or self-medicating, because these situations promote the selection of resistant bacteria. Overuse at the population level is also important: the more often antibiotics are used, the stronger the selective pressure driving resistance.

What does multidrug resistance mean?

Multidrug resistance is when bacteria are resistant to several different antibiotics at the same time, often from different classes. In practice, this means standard treatment stops working and the choice of effective antibiotics becomes limited, requiring targeted therapy. Multidrug resistance can result from multiple resistance mechanisms building up at once, such as bacterial enzymes that break down the drug, changes to the drug's target site, active pumping of the antibiotic out of the bacterial cell, or reduced drug entry. It can also be linked to biofilms, protective layers bacteria form on surfaces, which further block drug penetration and increase the risk of recurrent infection.

Which bacteria are resistant to antibiotics?

Antibiotic resistance can affect many bacterial species, including those responsible for hospital-acquired and community infections. Particularly problematic are bacteria that often cause severe infections and easily develop resistance, making treatment difficult or requiring last-resort antibiotics. Commonly discussed examples include methicillin-resistant strains of Staphylococcus aureus, certain intestinal bacteria that produce enzymes that inactivate beta-lactam antibiotics, and non-fermenting bacteria that can be resistant to many drug classes. It is worth remembering that resistance is not a fixed trait of an entire species. It applies to specific strains and populations, and its prevalence changes over time depending on region and clinical setting.

Why doesn't an antibiotic work?

An antibiotic may not work for several reasons, and the most common is that there was no indication for it, meaning the infection is not bacterial. Antibiotics do not treat viral infections, so in colds, flu, or many throat infections they won't lead to improvement. Another reason is antibiotic resistance, meaning the infection is caused by bacteria that are not susceptible to that drug. Sometimes the antibiotic is poorly matched to the infection site or the likely pathogen, and effective treatment requires switching the medication based on culture and susceptibility testing. Antibiotics can also be less effective if taken incorrectly, for example irregularly, at too low a dose, or for too short a time, because bacteria are not fully eliminated. Lack of improvement can also be due to complications, an abscess, a biofilm, or other coexisting conditions that change the course of infection and require additional measures beyond antibiotics alone.

Why aren't colds and viral infections treated with antibiotics?

Colds and most common viral infections are caused by viruses, and antibiotics work only against bacteria. An antibiotic does not kill a virus, so it does not shorten the duration of a cold or address its cause. Unnecessary antibiotic use increases the risk of side effects, can disrupt the natural bacterial flora, and promotes antibiotic resistance, both in the individual and across the population. Viral infections are usually managed with symptomatic treatment and support, and antibiotics are considered only if a bacterial superinfection develops, which should be assessed clinically. That is why distinguishing viral from bacterial infection and avoiding “just in case” antibiotics is so important, because it is one of the main drivers of rising resistance.