Invitro Activity of Tigecycline Against Gram Positive and Gram Negative Isolates
in a Tertiary Care Hospital
Uma Sekar, MBBS, DCP, MD,
Professor and Head, Department of Microbiology
Director ,Sri Ramachandra Laboratory services
Sri Ramachandra Medical College and Research Institute
Sri Ramachandra University, Porur,
Phone: +91 98408 37632
Background: Resistance to multiple anti-microbial agents among gram positive and gram negative pathogens is high worldwide. Tigecycline, a glycylcycline antibiotic is a promising advancement in the treatment of infections caused by multidrug resistant organisms.
Objectives: To evaluate the invitro activity of tigecycline against a spectrum of Gram positive and Gram negative pathogens Materials and Methods: A total of 195 non -repetitive, clinically significant isolates obtained from various clinical specimens from hospitalised patients were included in the study. The organisms isolated include methicillin resistant Staphylococcus aureus (MRSA) (n=40), Enterococcus fecalis (n=15), Streptococcus pneumoniae (n=10), Extended Spectrum Beta Lactamase (ESBL) producing Escherichia coli(n=40), ESBL producing Klebsiella pneumoniae (n=40), ESBL producing Enterobacter spp (n=15), Serratia marcesens (n=5), Acinetobacter baumannii (n=25) and Haemophilus influenzae (n=5). Minimum inhibitory concentrations (MIC) were determined for various classes of anti-microbial agents including tigecycline using broth microdilution methodology as defined by the Clinical laboratory Standards Institute (CLSI) using Microscan panels. Interpretation of the anti-microbial susceptibility testing was done as per CLSI criteria. For tigecycline, interpretative criteria was as per the United States Food and Drug Administration breakpoints. MRSA and ESBL screening were performed in accordance with CLSI guidelines.
Results: Tigecycline exhibited good activity against all the isolates tested in the study. The three most active agents in vitro against MRSA and Enterococcus fecalis isolates in this study were tigecycline, vancomycin and linezolid with 100 % susceptibility. In the case of ESBL producing Enterobacteriaceae, meropenem and tigecycline were the most active agents. Tigecycline was the most effective anti-microbial agent against the multidrug resistant Acinetobacter baumannii including the meropenem resistant isolates.
Conclusion: Tigecycline is an alternative option for the treatment of multi-drug resistant pathogens causing complicated skin and soft tissue and intra-abdominal infections.