Nav: Home

Antibiotics legitimately available in over-counter throat medications could contribute to increased antibiotic resistance

April 11, 2019

New research presented at this year's European Congress of Clinical Microbiology & Infectious Diseases (ECCMID) in Amsterdam, Netherlands (13-16 April) shows that the inappropriate of use of antibiotics legitimately available in over-the-counter (OTC) throat medications could be contributing to antibiotic resistance, thereby going against World Health Organisation (WHO) goals.

Certain OTC products aimed at treating sore throats contain topical antibiotics, and medications of this type 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 School of Pharmacy and Pharmaceutical Sciences at Cardiff University, UK and aimed to understand the development of bacterial resistance to four different topical antibiotics (gramicidin, neomycin, bacitracin and tyrothricin) commonly used in some OTC sore throat medicines.

The team examined four species of bacteria in which antibiotic resistance is a widespread and significant 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. The researchers also looked into cross-resistance, where bacteria exposed to one antibiotic can become less susceptible to a different antibiotic to which they may not have previously been exposed.

The researchers wanted to check whether the in-use concentrations of antibiotics in OTC medicines was above 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 the in-use concentrations of neomycin, bacitracin and tyrothricin were all above the MIC, confirming that these products were effective at preventing bacterial growth. No MIC could be determined for gramicidin, indicating that none of the concentrations tested were able to prevent growth of those two species of bacteria. For S. pyogenes and H. influenza MIC values for all the tested antibiotics were below in-use concentrations in OTC throat medicines, with H. influenza being unable to grow in any of the antibiotics and concentrations tested, and S. pyogenes only exhibiting growth in very weak concentrations (5% and 1% of those found in medicines) of neomycin.

When S. aureus was exposed to bacitracin, it eventually showed growth after 144 hours at higher concentrations, and a culture grown in a lower concentration of the drug was discovered to have decreased susceptibility to gentamicin, fusidic acid, and ciprofloxacin, 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. In addition, exposure to both standard and diluted concentrations of bacitracin was associated with clinical cross-resistance to other antibiotics," says Shephard. "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."

"This was an interesting study that showed once again the potential of bacteria to adapt to chemotherapeutic antibiotics highlighting the need for a prudent and perhaps controlled use of antibiotics in practice,"adds co-author Jean-Yves Maillard, Professor of Pharmaceutical Microbiology, School of Pharmacy and Pharmaceutical Sciences, Cardiff University, UK.

To date, the authors say that only products containing the antibiotic fusafungine have been removed. A wide range of other OTC products containing antimicrobials remain available across Europe (see notes to editor below).
-end-


European Society of Clinical Microbiology and Infectious Diseases

Related Bacteria Articles:

Conducting shell for bacteria
Under anaerobic conditions, certain bacteria can produce electricity. This behavior can be exploited in microbial fuel cells, with a special focus on wastewater treatment schemes.
Controlling bacteria's necessary evil
Until now, scientists have only had a murky understanding of how these relationships arise.
Bacteria take a deadly risk to survive
Bacteria need mutations -- changes in their DNA code -- to survive under difficult circumstances.
How bacteria hunt other bacteria
A bacterial species that hunts other bacteria has attracted interest as a potential antibiotic, but exactly how this predator tracks down its prey has not been clear.
Chlamydia: How bacteria take over control
To survive in human cells, chlamydiae have a lot of tricks in store.
Stress may protect -- at least in bacteria
Antibiotics harm bacteria and stress them. Trimethoprim, an antibiotic, inhibits the growth of the bacterium Escherichia coli and induces a stress response.
'Pulling' bacteria out of blood
Magnets instead of antibiotics could provide a possible new treatment method for blood infection.
New findings detail how beneficial bacteria in the nose suppress pathogenic bacteria
Staphylococcus aureus is a common colonizer of the human body.
Understanding your bacteria
New insight into bacterial cell division could lead to advancements in the fight against harmful bacteria.
Bacteria are individualists
Cells respond differently to lack of nutrients.

Related Bacteria Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Anthropomorphic
Do animals grieve? Do they have language or consciousness? For a long time, scientists resisted the urge to look for human qualities in animals. This hour, TED speakers explore how that is changing. Guests include biological anthropologist Barbara King, dolphin researcher Denise Herzing, primatologist Frans de Waal, and ecologist Carl Safina.
Now Playing: Science for the People

#SB2 2019 Science Birthday Minisode: Mary Golda Ross
Our second annual Science Birthday is here, and this year we celebrate the wonderful Mary Golda Ross, born 9 August 1908. She died in 2008 at age 99, but left a lasting mark on the science of rocketry and space exploration as an early woman in engineering, and one of the first Native Americans in engineering. Join Rachelle and Bethany for this very special birthday minisode celebrating Mary and her achievements. Thanks to our Patreons who make this show possible! Read more about Mary G. Ross: Interview with Mary Ross on Lash Publications International, by Laurel Sheppard Meet Mary Golda...