A team of researchers from the Carlos III Health Institute (ISCIII) has published a study the results of which confirm that resistance to the antibiotic erythromycin has increased significantly in recent years in the treatment of infections caused by Staphylococcus aureus . Examples include pneumonia, conjunctivitis, gastrointestinal disease, meningitis, and sepsis.
The article, published in the journal Frontiers in Microbiology, provides new findings to explain this increase in resistance. This cause of resistance affects the effectiveness of erythromycin in treating infections caused by streptococci. Staphylococcus aureus is associated not only with the consumption of erythromycin but also with any antibiotic belonging to the macrolide, lincosamide, or streptogramin families. Antimicrobial resistance, caused by overdosing or incorrectly taking medications such as antibiotics, is one of the major problems in treating infections.
This work was led by the ISCIII National Center for Microbiology (CNM). Jesús Oteo, Head of the Antibiotic Resistance Reference Laboratory at CNM-ISCIII, highlighted the collaborative nature of the work, which was carried out in collaboration with the ISCIII Network Center for Biomedical Research (CIBER) and involved 6 groups from the field of infectious diseases (CIBERINFEC) and one in the field of respiratory diseases (CIBERES).
The research was carried out within the context of the Precision Medicine on Antimicrobial Resistance (MEPRAM) project, which is funded through ISCIII’s Call for Precision and Personalized Medicine and has a budget of more than £4 million over the next three years.
The Spanish EARS-Net network group, consisting of 47 hospitals associated with the European Center for Disease Prevention and Control (ECDC) and the Spanish Agency for Medicines and Healthcare Products (AEMPS), is also involved in this work. National Antimicrobial Resistance Program (PRAN). Oteo noted that this multidisciplinary approach “is the only way possible” if we want to successfully fight multidrug-resistant bacteria.
Genes associated with drug resistance found
In this work, a significant increase in resistance to erythromycin was observed, which was associated with increased consumption of this antibiotic. The study supports the hypothesis that an erythromycin-resistant “Staphylococcus aureus” clade, known as ST398 MSSA, is involved in this trend. In the field of microbiology, the term “clade” refers to a group of microorganisms that, in an evolutionary and phylogenetic context, share a common ancestor that defines the characteristics of their descendants.
Oteo explained that the significant increase in resistance to this antibiotic, one of the most commonly used to treat respiratory infections, appears to be directly linked to increased consumption of macrolide antibiotics at the community level. Molecular analysis by genome sequencing showed that this increase was due to the dispersion of the aforementioned clade ST398, which carries a gene called ermT that causes resistance to erythromycin.
In this work, antibiotic susceptibility data were obtained for more than 36,000 Salmonella strains. S. aureus was isolated from blood samples of patients in 47 hospitals in Spain between 2004 and 2020, and 137 geographically and temporally representative strains were sequenced for subsequent genome analysis. Antibiotic consumption data were obtained from the Spanish Agency for Medicines and Health Products (2008–2020).
In this sense, the World Health Organization (WHO) considers “S. aureus resistance to methicillin (MRSA) to be the main indicator of multidrug resistance in this species and the most relevant for the search for therapeutic alternatives” One reason is because resistance to antibiotics has become one of the major threats in the fight against infection.
ISCIII researchers note “the importance of having a molecular surveillance system for methicillin-resistant ‘Staphylococcus aureus’ that can identify the emergence of new subpopulations in clinical settings and their correlation with changes in antibiotic susceptibility patterns” .
Finally, he added that more genome sequencing studies are needed to improve the identification of these particularly resistant subpopulations of bacteria in clinical settings and how they relate to changes in antibiotic susceptibility patterns.