Rahul Harikumar Lathakumari

Carbapenem resistance in Gram-negative bacteria poses a critical global health challenge, particularly in the context of bloodstream infections (BSIs) where treatment options are severely limited and diagnostic delays can be fatal. Existing methods for detecting carbapenem resistant organisms (CROs) often lack the speed, sensitivity, and specificity required for timely clinical intervention, and currently, no validated approach exists for direct detection from blood samples. In this study, we introduce a novel diagnostic strategy utilizing bovine serum albumin-stabilized gold nanoclusters (BSA-AuNCs), which exhibit a strong fluorescence emission and average size of 2.9 nm. This method enabled rapid detection of carbapenem resistance among 400 Gram-negative clinical isolates, with 97 confirmed resistant by both phenotypic and genotypic analyses. Real-time PCR revealed NDM and VIM as the most common resistance genes, followed by OXA-48, IMP, and KPC. The BSA-AuNC assay detected as few as 10 CFU/mL in cultured isolates within 1.5 h, achieving 100% positive and negative predictive values. Remarkably, when applied directly to centrifuged blood samples, the assay maintained a high sensitivity of 95.8% with a detection limit of 1000 CFU/mL in under 2 h, outperforming the Carba NP test, which showed only 85.56% sensitivity. These findings highlight the potential of BSA-AuNCs as a rapid, sensitive, and culture-independent tool for early identification of carbapenem-resistant organisms in BSIs, offering critical support for timely and effective clinical decision-making.

Background: Carbapenem-resistant Gram-negative bacteria (CR-GNB) pose a serious global health threat, especially in low- and middle-income countries. Local surveillance is crucial for informing antimicrobial stewardship and infection control strategies. This study aimed to evaluate the prevalence, demographic distribution, and temporal fluctuations of carbapenem resistance among key Gram-negative pathogens in a South Indian tertiary care center over a two-year period.Methods: A retrospective study was conducted on 8,359 non-duplicate Gram-negative isolates obtained from clinical specimens between July 2022 and July 2024. Organisms were identified, and antimicrobial susceptibility was determined using the VITEK^® 2 Compact system (BioMérieux). Resistance to imipenem (IPM) and meropenem (MEM) was assessed. Data were stratified by age, sex, ward type, specimen source, and quarterly distribution. A subset of resistant isolates underwent molecular screening for carbapenemase genes using real time PCR.Results: Carbapenem resistance was observed in 24% (2007) of Gram-negative isolates. Acinetobacter baumannii (48.0%) and Klebsiella pneumoniae (38.6%) accounted for the majority of resistant cases. Resistance was significantly higher in males (64.3%) and in patients aged 61–80 years (p < 0.001). Surgical wards showed greater resistance rates compared to medical departments. A peak in resistance was identified during January–March 2023, particularly for A. baumannii (76.3%). IPM-MEM resistance discrepancies were found in Citrobacter and Proteus species. Gene profiling of resistant strains revealed the predominance of bla_NDM, bla_VIM in all organism.Conclusion: The findings reveal a high and fluctuating burden of carbapenem resistance, especially in elderly males and surgical settings. Continuous surveillance and targeted interventions are vital to curbing the spread of CR-GNB in high-risk healthcare environments.

Proteus mirabilis, an opportunistic pathogen frequently implicated in urinary and wound infections, has shown increasing multidrug resistance, posing significant therapeutic challenges. The study aims to investigate the prevalence and distribution of β-lactam resistance in P. mirabilis clinical isolates through the genotypic detection of the bla_KPC-2 and bla_NDM-1 genes. This study analyzed 100 clinical isolates of P. mirabilis obtained from various clinical specimens over a period of 10 months. Isolates were identified through standard microbiological techniques, including Gram staining, culture characteristics, and biochemical profiling. The majority of isolates (46 %) were recovered from patients aged 61–75 years, with a male predominance (65 %). Pus samples accounted for the highest number of isolates (59 %), predominantly associated with diabetic foot ulcers, cellulitis, and gangrene. Antimicrobial susceptibility testing using Vitek (bioMérieux) showed that 33.31 % of isolates were resistant to commonly used antibiotics, with the highest resistance noted against ciprofloxacin (58 %), ceftazidime (50 %), and cotrimoxazole (49 %). However, piperacillin-tazobactam (96 %), Fosfomycin (94 %), and ertapenem (87 %) remained largely effective. Multidrug resistance was observed in 83 % of isolates, with 18 % showing resistance to six antibiotic classes. Molecular characterization showed that 19 % of isolates harbored the bla_NDM-1 gene, 8 % carried bla_KPC-2, and 4 % co-harbored both, indicating carbapenemase production. These findings underscore the urgent need for continuous surveillance, strict infection control measures, and prudent antibiotic use to curb the emergence and spread of resistant P. mirabilis strains in clinical settings.