Journal of Medical Microbiology and Infectious Diseases

en Identification, Antibiogram, and Phenotypic Detection of β-Lactamase-Mediated Resistance in Non-Fermenting Gram-Negative Bacilli (NFGNB) from a Tertiary Care Hospital in Mysore Anti-microbial agents, resistance and treatment protocols Anti-microbial agents, resistance and treatment protocols Original article Original article <div style="text-align: justify;">Introduction: Non-fermenting Gram-negative bacilli (NFGNB) are emerging healthcare-associated pathogens whose rapidly escalating antimicrobial resistance poses substantial therapeutic challenges. This study aimed to determine the prevalence and antimicrobial resistance patterns of NFGNB and to detect β-lactamase-mediated resistance mechanisms (extended-spectrum β-lactamase [ESBL], metallo-β-lactamase [MBL], and AmpC) in a tertiary care hospital in Mysore, Karnataka, India. Methods: In this prospective two-month study, NFGNB were isolated from various clinical specimens (blood, pus, urine, synovial fluid, suction catheter tips, and endotracheal aspirates). Blood specimens were inoculated into brain–heart infusion broth and subcultured onto blood agar and MacConkey agar; all other specimens were plated directly and incubated aerobically at 37 °C for 16–18 h. Bacterial identification and antimicrobial susceptibility testing were performed using the BD Phoenix M50 system. Phenotypic detection of ESBL, MBL, and AmpC was carried out using combined disc-based methods, as the Clinical and Laboratory Standards Institute (CLSI) does not provide standardized confirmatory tests for these mechanisms in non-fermenters. Results: Of 3,000 clinical specimens, 50 yielded NFGNB (prevalence, 1.7%), with 64% originating from ICUs (95% CI: 49.2–77.1%). The predominant species were Pseudomonas putida (18%), Pseudomonas aeruginosa (16%), and Acinetobacter baumannii (16%). P. putida exhibited 100% resistance to ceftazidime, cefepime, ciprofloxacin, levofloxacin, piperacillin–tazobactam, tetracycline, and cefotaxime, while amikacin and gentamicin retained activity against 77.8% and 88.9% of isolates, respectively. P. aeruginosa showed high resistance to ceftazidime and cefepime (87.5% each) and to piperacillin–tazobactam and levofloxacin (75% each). A. baumannii was uniformly susceptible to colistin but resistant to most other agents. Phenotypic analysis revealed ESBL production in 28%, MBL production in 34%, and presumptive AmpC production in 92% of isolates, of which 60.9% were confirmed. Multiple β-lactamase types co-occurred in several isolates. Conclusion: The high prevalence of multidrug-resistant NFGNB, particularly extensively drug-resistant P. putida and carbapenem-resistant Acinetobacter species, underscores the urgent need for strengthened local antimicrobial resistance surveillance, timely identification, and continuous monitoring of resistance trends to guide targeted therapy and improve patient outcomes.</div>   Non-fermenting Gram-negative bacilli, Antimicrobial resistance, ESBL, MBL, AmpC, β-Lactamase, Healthcare-associated infection 159 167 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-528-3&slc_lang=en&sid=1 Swetha M 0009-0009-4422-4720 No Department of Microbiology, Mysore Medical College and Research Institute, Mysore, Karnataka, India Sherin Martin 0009-0003-5244-5124 No Department of Microbiology, Mysore Medical College and Research Institute, Mysore, Karnataka, India Beebi Ameena ameenabeebi27@gmail.com 0009-0009-2869-2559 Yes Department of Microbiology, Mysore Medical College and Research Institute, Mysore, Karnataka, India Amrutha Kumari B 0009-0000-5332-1308 No Department of Microbiology, Mysore Medical College and Research Institute, Mysore, Karnataka, India Priyadharshini Radhakrishnan 0009-0003-1076-8996 No Department of Microbiology, Mysore Medical College and Research Institute, Mysore, Karnataka, India