Novel Domain V mutation in cfr-positive clinical Staphylococcus haemolyticus isolates causing linezolid resistance in Egyptian ICU patients

Linezolid resistance has become a focal point worldwide, particularly as linezolid stands as one of the last resort antibiotics against multiple-drug resistant bacterial strains. Despite its critical importance, the situation in Egypt remains relatively unexplored. As various linezolid resistance mechanisms have been identified in staphylococci, our investigation aims to uncover the molecular characteristics of staphylococci showing reduced susceptibility to Linezolid at Kasr-El-Eini Teaching Hospital. Thirty isolates were investigated in this study. The selected samples, identified by Vitek 2 system and confirmed by 16S rRNA, were examined by disc diffusion method. Of the 30 isolates, two were confirmed as linezolid resistant and screened for the presence of cfr gene and mutations in the Domain V of the 23S rRNA gene. Both of the studied strains, identified as Staphylococcus haemolyticus, SZ-2 and SZ-7 harbored two point mutations G2576T and G2602T in the Domain V of the 23S rRNA gene. A novel G2694C mutation reported for the first time was detected in strain SZ-7. The presence of cfr gene was confirmed in both isolates. Linezolid-resistant Staphylococcus haemolyticus had emerged in ICU patients with prior antibiotic exposure. The exact role of the novel G2694C mutation in linezolid resistance needs further investigations. The study underscores the importance of proper surveillance of cfr-carrying strains in the healthcare settings in Egypt.