Evaluation of tigecycline activity in clinical isolates among Indian medical centers.

Background: Resistance to multiple antibiotics among Gram-positive cocci (GPC) and Gram negative bacilli (GNB) is high in India. Tigecycline, a glycylcycline antibiotic is a newer treatment option for emerging single or multidrug-resistant (MDR) GPC and GNB.

Material And Method: We evaluated the in vitro activity of tigecycline and compared it against other antimicrobials. Between 2005-2007, seven Indian medical centers from diverse geographic regions forwarded 727 isolates [Escherichia coli (166), Staphylococcus aureus (125), Klebsiella spp (120), Streptococcus pneumoniae (102), Enterococcus spp. (100), Pseudomonas aeruginosa (50), Acinetobacter spp. (50) and Enterobacter spp. (14)] from patients with blood stream (BSI), skin and soft tissue (SSTI) including surgical site, urinary tract and respiratory infections to our reference laboratory. Susceptibility to 11 antimicrobials besides tigecycline included: vancomycin, linezolid, teicoplanin, quinopristin-dalfopristin, daptomycin, amikacin, imipenem, levofloxacin, meropenem, and piperacillin/tazobactam was determined by agar dilution and Etest method.

Result: Tigecycline was active against all GPC (MIC 90 < 0.25 μg/ml), E. coli and Klebsiella spp. (MIC 90 ≤1 μg/ml). MDR Acinetobacter spp. showed lower susceptibility (70.6%) to tigecycline. Tigecycline MIC 90 values were not influenced by oxacillin resistance among S. aureus, S. pneumoniae, vancomycin resistance in Enterococci (VRE) and ESBL producing E. coli, Klebsiella spp. and Enterobacter spp. Increased resistance was seen to other antimicrobials among ESBL producing E. coli, Klebsiella spp., Metallo Beta Lactamase (MBL) producing P. aeruginosa and VRE.

Conclusion: Tigecycline is an alternative option for emerging multidrug-resistant (MDR) pathogens exhibiting promising spectrum/potency exceeding currently available agents seen in India.