Antibiotics are amazingly effective drugs, which have saved tens of millions of lives since their discovery in the mid-20th century. Over the last seven decades, many millions of metric tons of antibiotics have been used in both clinical and veterinary practice.
This has contributed to the emergence and spread of bacteria that are no longer affected by the antimicrobial action of antibiotics. Infections caused by these antibiotic-resistant bacteria are exceedingly difficult to treat and can be life-threatening, particularly in individuals with a weakened immune system.
The spread of antibiotic resistant bacteria can also endanger routine surgical interventions, such as caesarean sections and hip replacements. The number of deaths caused by drug-resistant bacteria is likely to increase sharply over the next few decades, particularly in low- and middle-income countries. Some scientists are warning that the world is at the cusp of entering a post-antibiotic era, in which, due to the spread of resistance, antibiotics will be entirely ineffective.
While these future scenarios are bleak, it is not beyond our control to turn back the tide on antibiotic resistance. One way in which we can minimise the use of antibiotics, or the impact of resistance, is by implementing new approaches to minimise the risk of patients becoming infected in the first place.
One of the most controversial interventions to prevent infections in critically ill patients is termed ‘Selective Decontamination of the Digestive tract’ (SDD). During SDD, Intensive Therapy Unit (ITU) patients are treated with a mix of three different antibiotics that are administered to the throat and the gut. The aim of SDD is to minimise the carriage of potential pathogens in the gut, while not affecting the harmless bacteria. Large trials have recently shown that SDD improves patient outcome during ITU hospitalisation. However, SDD is currently not widely implemented due to concerns that the indiscriminate use of antibiotics during SDD will select for antibiotic resistant bacteria.
A recent study led by the University of Birmingham, working with collaborators in the Netherlands and Finland, has compared the bacteria that live in the gut (or the ‘gut microbiome’) of patients treated with SDD with the gut microbiome of healthy individuals. The study showed that the gut microbiome of ITU patients rapidly changes after admittance to the ITU, presumably due to the patients’ critical illness combined with the use of SDD. Levels of the important ‘hospital bug’ Escherichia coli remained low during SDD and this is the likely explanation as to why ITU patients treated with SDD are less likely to have infections with this bacterium. Notably, only limited effects on resistance were observed, presumably because the use of three different antibiotics kills bacteria before they have the chance to develop resistance.
This study will not be the final word on SDD, but it may allay some fears concerning its effect on antibiotic resistance. SDD has been proven to save patients’ lives during ITU hospitalisation, and we will need to have a discussion on whether the benefits of SDD outweigh its risks.
Willem Van Schaik, Professor in Microbiology and Infection
College of Medical and Dental Sciences, University of Birmingham