Microbiological Profile and Antimicrobial Susceptibility Patterns of Non-fermenting Gram-Negative Bacilli Isolated From Clinical Specimens in a Tertiary Care Hospital: A Prospective Study

BackgroundNon-fermenting Gram-negative bacilli (NFGNB), including Pseudomonas aeruginosa, Acinetobacter baumannii, Burkholderia cepacia complex, and Stenotrophomonas maltophilia, are important healthcareassociated pathogens with variable antimicrobial susceptibility patterns.This study assessed the microbiological profile and antimicrobial susceptibility patterns of NFGNB isolated from clinical specimens at a tertiary-care hospital in Gujarat, India. MethodsThis prospective, observational, laboratory-based study was conducted at the Central Microbiology Laboratory of Dhiraj Hospital, Vadodara, from April 1 to September 30, 2023.Clinical specimens from inpatients and outpatients were processed, and organism identification and antimicrobial susceptibility testing (AST) were performed using the VITEK 2 system (bioMérieux, Inc., Marcy-l'Étoile, France).The study documentation indicated interpretation according to the Clinical and Laboratory Standards Institute (CLSI) M100, 33rd edition (2023); however, the historical breakpoint implementation could not be independently verified. ResultsOf 278 initially identified laboratory records, 56 (20.14%) were excluded, leaving 222 clinical specimens for analysis.These specimens yielded 227 target NFGNB isolates, including five polymicrobial specimens containing both P. aeruginosa and A. baumannii.Among the 222 specimens, 109 (49.10%) yielded monomicrobial P. aeruginosa, 73 (32.88%) yielded monomicrobial A. baumannii, 20 (9.01%) yielded B. cepacia complex, and 15 (6.76%) yielded S. maltophilia.Including the co-isolates, the species-specific denominators for antimicrobial susceptibility analysis were 114 for P. aeruginosa and 78 for A. baumannii.Pus or wound swabs were the most common specimen type (37.39%).Among specimens with documented departmental information, intensive care units accounted for 77.85%.P. aeruginosa showed the highest recorded susceptibility to amikacin (50.00%), cefepime (46.49%), and cefoperazone-sulbactam and meropenem (45.61% each).A. baumannii showed the highest recorded susceptibility to minocycline (35.90%) and trimethoprim-sulfamethoxazole (24.36%), while susceptibility to imipenem and meropenem was 10.26% for each.B. cepacia complex showed the highest recorded susceptibility to meropenem (75.00%), whereas S. maltophilia showed the highest recorded susceptibility to minocycline (86.67%).Conclusion P. aeruginosa and A. baumannii were the predominant NFGNB in this study, with low recorded susceptibility to several tested antimicrobial agents.These findings provide institution-specific surveillance data that may inform local antimicrobial stewardship and infection-control initiatives.The results should be interpreted cautiously because historical breakpoint implementation could not be independently verified and should not be used alone to guide empirical treatment.