A British study warns of a rise in antibiotic-resistant Shigella infections among men who have sex with men

The study is well done, with a good selection of data and the usual limitations of this type of study. For example, in cases where not all necessary patient data are available, the authors assume that if it is not noted that the person has traveled to a high-risk country, it means the person has not been in a high-risk country in the past 28 days; or, if gender is not specified, the person is female (which automatically places the sample in the group of non-men who have sex with men). This study highlights the need to adopt antibiotic treatment guidelines in our healthcare systems that take into account the complex dynamics of antimicrobial resistance. The term “bystander resistance” refers to situations in which an antibiotic is used to treat an infection caused by a specific bacterium, but the treatment has the side effect of selecting for resistance to that antibiotic in a different bacterium. In this case, treating a patient with a gonorrhea infection using azithromycin could promote the selection of azithromycin resistance in Shigella if the patient were also infected with this second bacterium. When the United Kingdom’s national treatment guidelines stopped recommending the use of this antibiotic to treat gonorrhea infections, the emergence of azithromycin resistance in Shigella slowed down. The spread of antimicrobial resistance is a highly complex phenomenon due to several factors. First, bacteria live in highly complex communities that foster intense interaction among them, as is the case in the human microbiome. Second, different bacteria exhibit varying susceptibility to the same antibiotic. This means that the dose adequate to eliminate one bacterial species may be insufficient to eliminate another, which can promote the emergence of antibiotic resistance in the latter. Third, human communities are also highly complex, and a wide variety of individual behaviors coexist within them. All these factors make it difficult to establish appropriate national guidelines for antibiotic use. As our knowledge of antimicrobial resistance grows, national guidelines must be updated to reflect these new advances and our increasingly precise understanding of this phenomenon.