Purpose: Tigecycline, a glycylcycline antibiotic is a promising option for the treatment of single or multidrug-resistant pathogens. The aim of the study was to evaluate the in-vitro Tigecycline susceptibility of various pathogens from clinical samples received at tertiary care hospitals in South India. 

Methods: The analysis of specimens from patients admitted was carried out in this retrospective cross-sectional study. The identification and antimicrobial susceptibility testing were performed by semi-automated Vitek 2 systems and Kirby Bauer method. The pattern of data analysis was done by descriptive statistics.

Results: Among 2,574 isolates, 812 isolates were gram-positive pathogens and 1762 isolates were gram-negative pathogens. Resistance to Tigecycline was more common among gram-negative pathogens (18.62%) in comparison to the gram-positive pathogens (0.49%). Among 740 Extended Spectrum Beta Lactamases (ESBL) producers such as Klebsiella species & E. coli, 629 isolates were susceptible, and 93 isolates were resistant to the tigecycline. All the Methicillin Resistant Staphylococcus aureus (MRSA) isolates were susceptible to tigecycline. Tigecycline was found to be highly effective in vitro for elimination of infections caused by both gram-positive and gram-negative pathogens.

Conclusion: Multidrug-resistant (MDR) pathogens like Acinetobacter species and Klebsiella species are highly susceptible to Tigecycline, and it remains one of the key drugs in monotherapy & combination therapy. All MRSA were sensitive to tigeclycline. The use of combination therapy becomes crucial to prevent the development of Pan Drug resistance.

The comprehensive data which includes 2,574 clinically significant isolates were retrieved from Laboratory Information System and microbiology records from the KMC hospital.

Study participants: The data of all samples received at Kasturba Medical College microbiology department were collected for a period of one year except for urine specimens as urinary concentration of tigecycline is poor.

The positive cultures were identified and antibiotic susceptibility testing was done for tigecycline by Vitek 2 compact system and Kirby-Bauer Disk Diffusion method as per the manufacturer's & FDA-approved guidelines respectively and interpreted as sensitive & resistant. EUCAST criteria were used for interpretation of MIC which ranged from 0.06 to 64 and Disk diffusion with 15 μg (Hi-Media). As per these criteria, MIC of tigecycline for Enterobacteriaciae < 2ug/ml is sensitive, and > 8ug/ml was considered resistant. By the Disk Diffusion method, the isolates with >19mm & < 14mm of zone diameter were considered as susceptible and resistant, respectively. All the Staphylococcus aureus isolates were screened for Methicillin resistance using the cefoxitin disk method or by Vitek 2 compact system and gram-negative Enterobacterales were screened for ESBL production using ceftazidime & ceftazidime clavulunic acid or Vitek 2 compact systems.

Sample collection

A convenient non-random sampling method was followed to collect data on specimens received at the microbiology laboratory of Kasturba Medical College, Mangalore.

Statistical analysis

All the data was entered into an Excel sheet and analyzed using IBM SPSS version 25. The continuous and categorical variables have been represented as mean ± standard deviation and frequency percentages respectively.

Microsoft Excel