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.

Background Methicillin-resistant Staphylococcus aureus (MRSA) is a widely recognized multidrug-resistant bacteria presenting a major therapeutic challenge to clinicians. Staphylococcus aureus possesses a number of pathogenicity factors that attribute to the severity of infections. This study was undertaken to investigate the common virulence genes in clinical isolates of Staphylococcus aureus, determine their antimicrobial susceptibility profile, and to characterize the staphylococcal cassette chromosome mec (SCCmec) types among MRSA in a tertiary care center. Materials and Methods A total of 133 clinical isolates were included in this study. Susceptibility to various antibiotics was determined by disc diffusion method. Methicillin resistance was screened using cefoxitin disc; mecA and mecC genes were detected using polymerase chain reaction (PCR). PCR was done to detect 12 virulence factors such as hla, hlb, fnbA, fnbB, sea, seb, sec, icaA, clfA, tst, pvl, and eta. SCCmec typing was done by multiplex PCR. Results Of the 133 clinical isolates, 54 (40.6%) were MRSA. The most common virulence gene detected was hlb (61.6%), hla (39%), and fnbA (37%). SCCmec type I was the most predominant. Mortality rate of 6.7% was observed among patients with staphylococcal infections. Univariate analysis of mortality associated virulence genes did not reveal any significant association between virulence genes and mortality. Conclusion The distribution of virulence genes is similar in both MRSA and methicillin-sensitive Staphylococcus aureus. MRSA belongs to the SCCmec types I to IV. Possession of multiple virulence factors and multidrug resistance profile makes Staphylococcus aureus a formidable pathogen in clinical settings.