Background: Non-fermenting gram-negative bacilli (NFGNB) once considered as contaminants have emerged as major cause of life threatening nosocomial infections and are frequently associated with multidrug resistance. Pseudomonas aeruginosa and Acinetobacter baumannii are among the most clinically important NFGNB implicated in healthcare-associated infections.
Objectives: To isolate and identify NFGNB from clinical samples and to compare conventional phenotypic method with automated VITEK-2 system for their identification and antimicrobial susceptibility testing.
Methodology: A cross-sectional study was conducted over six months (May–October 2025) in the Department of Microbiology, Vinayaka Mission's Kirupananda Variyar Medical College, Salem. A total of 1138 clinical samples were processed using microscopy, culture and standard biochemical tests. Presumptive NFGNB isolates were further identified using conventional techniques and confirmed by VITEK-2 automated system. Antimicrobial susceptibility testing was performed by Kirby-Bauer disc diffusion and compared with VITEK 2 AST results.
Results: Out of 1138 samples, 147 (12.9%) isolates were identified as NFGNB. Pseudomonas aeruginosa was the predominant isolate 108 (73.5%) followed by 13 isolates of Acinetobacter baumannii and 26 Stenotrophomonas maltophilia isolates. Multidrug resistance was predominantly observed in Acinetobacter baumannii followed by Stenotrophomonas maltophilia and Pseudomonas aeruginosa. The turnaround time for identification and AST was significantly shorter with VITEK-2 (8-18 hours) compared to conventional methods (48-72 hours).
Conclusion: VITEK-2 provides rapid and accurate identification of NFGNB, enabling timely antimicrobial therapy and strengthening antimicrobial stewardship. The predominance of Pseudomonas aeruginosa and high MDR rates among Acinetobacter baumannii highlight the need for continuous surveillance and strict infection control measures.
Keywords: Non fermenting gram negative bacilli (NFGNB), VITEK-2, Multidrug resistance (MDR), Antimicrobial susceptibility testing.
How to cite this article: Nalina C, Sureshkumar M, Comparative Evaluation of Conventional phenotypic Methods and VITEK 2 automated system for Identification and Antimicrobial Susceptibility testing of Non fermenting gram negative bacilli. Int J Drug Deliv Technol. 2026;16(5s): 239-246; DOI: 10.25258/ijddt.16.5s.29
Source of support: Nil
Conflict of interest: None