Antibiotics legitimately available in over-the-counter medications may help increase resistance

A new study presented this year at the European Congress on Clinical Microbiology and Infectious Diseases (ECCMID) in Amsterdam, the Netherlands (April 13-16) shows that the inappropriate use of antibiotics legitimately available in Over the counter throat medications could be contributing to antibiotic resistance, thus defeating the goals of the World Health Organization (WHO).

Some over-the-counter products for treating sore throat contain topical antibiotics, and such drugs are widely available around the world, including in the UK and many other European countries. This study, commissioned by Adrian Shephard, of Reckitt Benckiser Healthcare Ltd, was conducted by researchers from the Faculty of Pharmacy and Pharmaceutical Sciences of Cardiff University, UK. and tyrothricin) commonly used in some over-the-counter medications for sore throats.

The team looked at four species of bacteria for which antibiotic resistance is a widespread and important problem. Staphylococcus aureus, Acinetobacter baumannii, Streptococcus pyogenes and Haemophilus influenza. Cultures of each species were exposed to decreasing concentrations of antibiotics for 24 hours at human body temperature (37 ° C), and surviving bacteria were subcultured and tested for antibiotic sensitivity. The researchers also studied cross-resistance, in which bacteria exposed to an antibiotic may become less sensitive to another antibiotic to which they may not have been exposed before.

The researchers wanted to check whether antibiotic concentrations being used in over-the-counter medications were greater than the minimum inhibitory concentration (MIC); the lowest concentration of a drug that is still able to prevent bacterial growth. They found that for S. aureus and A. baumannii On-going concentrations of neomycin, bacitracin and tyrothricin were all greater than the MIC, confirming that these products were effective in preventing bacterial growth. No MIC could be determined for gramicidin, indicating that none of the concentrations tested were able to prevent the growth of these two species of bacteria. For S. pyogenes and H. influenza The MIC values ​​for all antibiotics tested were lower than the concentrations used in over-the-counter throat drugs, with H. influenza be unable to grow in any of the antibiotics and concentrations tested, and S. pyogenes showing only growth at very low concentrations (5% and 1% of those found in drugs) of neomycin.

When S. aureus was exposed to bacitracin, it finally showed growth after 144 hours at higher concentrations, and a culture grown at a lower concentration of the drug had reduced susceptibility to gentamicin, fusidic acid and ciprofloxacin, indicating that he had developed cross-resistance.

"We were concerned that some of the over-the-counter antibiotics used in sore throat preparations were not concentrated enough to prevent the growth of common human pathogens and allowed these pathogens to In addition, exposure to both standard and diluted concentrations of bacitracin was badociated with clinical cross-resistance to other antibiotics, "Shephard says. "Our work raises doubts about the continued availability of these over-the-counter antibiotics for the treatment of sore throats, especially given the predominantly viral nature of the disease."

"This was an interesting study that once again showed the potential for adaptation of bacteria to chemotherapeutic antibiotics, highlighting the need for careful and possibly controlled use of antibiotics." in practice, "adds co-author Jean-Yves Maillard, professor of pharmaceutical microbiology, at the school. Pharmacy and Pharmaceutical Sciences, Cardiff University, UK.

To date, the authors say that only products containing the fusafungine antibiotic have been removed. A wide range of other over-the-counter products containing antimicrobials remains available throughout Europe (see note to editors below).

Provided by
European Society of Clinical Microbiology and Infectious Diseases