Antibiotic Effect of Tigecycline on Gram Negative Bacilli

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

All the samples received in the Microbiology laboratory were processed according to standard protocols. Once identified, they were subjected to antibiotic susceptibility testing by disk diffusion method on Mueller Hinton agar. We evaluated the in vitro activity of tigecycline and compared it against other antimicrobials. Among 356 isolates, [Escherichia coli (126), Klebsiella spp (61), Pseudomonas aeruginosa (133), Acinetobacter spp. (23) and Proteus (13)] from patients with, skin and soft tissue (SSTI) including surgical site, urinary tract and respiratory infections were isolated in our laboratory, Department of Microbiology, Mandya Institute of Medical Sciences, Mandya. Susceptibility to antimicrobials besides tigecycline included amikacin, imipenem, levofloxacin, meropenem, and piperacillin/tazobactam was determined by disk diffusion method.

Tigecycline was active against all E. coli and Klebsiella spp by disc diffusion method. MDR Acinetobacter spp. showed lower susceptibility (70.6%) to tigecycline and Pseudomonas spp and Proteus spp showed high resistance. Increased resistance was seen to other antimicrobials among Extended Spectrum Beta Lactamases(ESBL) producing E. coli, Klebsiella spp., Metallo Beta Lactamase (MBL) producing P. aeruginosa.

Tigecycline shows high potency against Gram-negative bacilli belonging to family Enterobacteriaceae in whom multi-drug resistant strains have emerged as important nosocomial pathogens. Tigecycline is highly active against Enterobacteriaceae, regardless of the presence or absence of ESBLs, >99% of all of the tested strains were inhibited. In the present study we found that tigecycline had good activity against tested E.coli and Klebsiella spp.

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