Tigecycline Resistance among Clinical Isolates of Staphylococcus aureus from North-east India

Objective: The current study investigated the resistance against cycline group of antibiotic among clinical isolates of Staphylococcus aureus and molecular characterization with special reference to phenotypic screening of Tigecycline resistance. Methods: 197 coagulase producing Staphylococcus spp. were collected from private diagnostic laboratories and Silchar Medical College and Hospital, India. Phenotypic screening was done with cycline groups of antimicrobials and genotypically characterized by PCR, targeting coa gene. Detection of tetK , tetM , tetO and tetX genes was performed by PCR. Antibiogram profiling was performed and clonality was also determined. Results: 127 coagulase positive S. aureus were phenotypically screened with cycline group of antibiotics in which prominent resistant type showed highest non-susceptibility against Tigecycline 53.5% (n=68) while lowest against minocycline 20.5% (n=26). Multiplex PCR assay showed that tet(K) gene to be the most common cycline group of antimicrobial resistance determinant in S. aureus , followed by tet(M) gene. Multiple genes were also observed. However, resistant gene tet(O) was not reported. Antibiotic susceptibility testing and MIC for therapeutic purpose showed highest susceptibility rate against linezolid. DNA fingerprinting experimented with PFGE had shown seven pulsotypes. Conclusion: Resistance to cycline group of antibiotics with special reference to Tigecycline is not frequently reported from India. Thus, this study is of clinical interest in terms of selection of proper antimicrobial chemotherapy and also using Tigecycline for phenotypic screening of cycline group of antibiotic resistance in Staphylococcus aureus .