National Institute of Allergy and Infectious Diseases / CDC
Non-antibiotic containing over-the-counter (OTC) treatments should be considered for the symptomatic management of sore throat to help protect against Antimicrobial resistance (AMR), researchers have recommended.
Researchers from the School of Pharmacy and Pharmaceutical Sciences at Cardiff University carried out a study to understand the development of bacterial resistance to locally delivered antibiotics (gramicidin, neomycin, bacitracin and tyrothricin) commonly used in OTC sore throat medicines, and to measure possible emerging cross-resistance to different classes of antibiotics.
They examined four species of bacteria in which Antibiotic resistance is considered a widespread problem: Staphylococcus aureus; Acinetobacter baumannii; Streptococcus pyogenes; and Haemophilus influenza.
Cultures of each species were exposed to decreasing concentrations of antibiotic for 24 hours at human body temperature (37°C), and surviving bacteria were sub-cultured and tested for antibiotic susceptibility.
H. influenza was unable to grow in any of the antibiotics and concentrations tested, but the researchers were able to demonstrate decreasing susceptibility to several antibiotics in the other three pathogens.
For example, S. aureus was able to grow in the presence of gramicidin and bacitracin after 24 hours and 144 hours, respectively, at concentrations that were the same, or higher, than those found in commercially available OTC medicines. In addition, S. aureus grown in the presence of bacitracin also decreased its susceptibility to other antibiotics, including gentamicin, indicating that it had developed cross-resistance.
“We were concerned to find that some of the OTC antibiotics used in sore throat preparations were not sufficiently concentrated to prevent growth of common human pathogens and are enabling these pathogens to develop resistance,” said Adrian Shephard from Reckitt Benckiser Healthcare Ltd, who commissioned the study.
”Our work raises doubt about the continued OTC availability of these antibiotics for the treatment of sore throats, especially considering the primarily viral nature of the condition.”
The researchers, who will present at the 2019 European Congress of Clinical Microbiology & Infectious Diseases in Amsterdam on 13–16 April 2019, said that given the global drive to tackle AMR and to minimise the overuse and misuse of antibiotics, the findings raise doubt about the validity of continued use of topical OTC antibiotics for primarily viral and self-limiting sore throat and that non-antibiotic containing treatments should be considered instead.
