Detection of a Novel G2603T Mutation in cfr Harboring Linezolid-Resistant Staphylococcus haemolyticus: First Report from India

Abstract

Background Staphylococcus haemolyticus has emerged as an important multidrug-resistant nosocomial pathogen. Linezolid is useful in the treatment of severe infections caused by methicillin-resistant Staphylococci. Resistance to linezolid in Staphylococci is due to one or more of the following mechanisms: acquisition of the cfr (chloramphenicol florfenicol resistance) gene, mutation in the central loop of domain V of the 23S rRNA, and mutation in the rplC and rplD genes. This study was carried out to detect and characterize resistance to linezolid among the clinical isolates of Staphylococcus haemolyticus. Materials and Methods The study included 84 clinical isolates of Staphylococcus haemolyticus. Susceptibility to various antibiotics was determined by disc diffusion method. Minimum inhibitory concentration (MIC) was determined by agar dilution method for linezolid. Methicillin resistance was screened using oxacillin and cefoxitin disc. Polymerase chain reaction was done to detect mecA, cfr and mutations in the V domain of the 23S rRNA gene. Results Resistance to linezolid was exhibited by 3 of the 84 study isolates with MIC more than 128 µg/mL. The cfr gene was detected in all the three isolates. The G2603T mutation was observed in the domain V of the 23S rRNA among two isolates, whereas one isolate lacked any mutation. Conclusion The emergence and spread of linezolid-resistant Staphylococcus haemolyticus isolates carrying G2603T mutation in the domain V of the 23S rRNA and harboring the cfr gene pose a threat in clinical practice.

Multiple mechanisms of linezolid resistance in Staphylococcus haemolyticus detected by whole-genome sequencing

“…Hence, in later reports, the reference genome of S. haemolyticus itself was used [23, 24]. In the present study, the complete genome sequence of S.…”

“…However, this may not yield accurate results, as the 23S rRNA sequences are species-specific. Hence, in later reports, the reference genome of S. haemolyticus itself was used [23,24]. In the present study, the complete genome sequence of S. haemolyticus JCSC1435 was used as the reference sequence for 23S rRNA mutational analysis.…”

“…haemolyticus isolates. However, it should be noted that mutations in ribosomal proteins were not tested in their study [23]. Another study by Maarouf et al from Egypt reported the presence of three LRSH isolates among 232 staphylococcal isolates using disc diffusion and broth micro-dilution methods.…”