Resistance of gram-negative and gram-positive pathogens to omadacycline: a systematic review.

INTRODUCTION

Omadacycline is a semisynthetic aminomethylcycline, tetracycline-type antibiotic, approved by the Food and Drug Administration (FDA) for treating patients with acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP). This study aimed to assess the in vitro activity of omadacycline against Gram-positive and Gram-negative bacteria.

METHODS

This systematic review was done according to the "Preferred Reporting Items for Systematic Reviews and Meta-Analyses" (PRISMA) guidelines. A search was conducted across five databases (Google Scholar, Web of Science, Embase, Scopus, and PubMed) to identify relevant articles from their inception to October 2025. The data were interpreted in accordance with the FDA omadacycline resistance breakpoints for ABSSSI and CABP.

RESULTS

In total, 31 relevant studies were included. The resistance of methicillin-resistant (MRSA) and methicillin-susceptible (MSSA) Staphylococcus aureus isolates to omadacycline was 0-13% and 0.3-0.7%, respectively. The resistance of Enterococcus faecalis, Streptococcus pneumoniae, and Streptococcus pyogenes isolates was 0%-2.2%, 0%-0.8%, and 0%-0.2%, respectively. Regarding Gram-negative bacteria, the resistance of Hemophilus influenzae isolates to omadacycline was 0%-0.2%, of Enterobacter cloacae 0.3%-25.8%, and of Klebsiella pneumoniae 0%-100%.

CONCLUSION

Omadacycline demonstrated good in vitro activity against S. pneumoniae, H. influenzae, S. aureus (both MSSA and MRSA), and E. faecalis. The activity against E. cloacae was also considerable. However, the drug demonstrated limited activity against K. pneumoniae.