To Study the Incidence, Risk Factors, Antibiotic Susceptibility, Resistant Mechanism and Treatment Outcome in Critically Ill Patients with Carbapenem Resistant Acinetobacter Baumanii (CRAB) Infection in a Tertiery Care Setup: A Prospective Observatio

INTRODUCTION: Carbapenem-resistant Acinetobacter baumannii (CRAB) remains one of the most important public health challenges of 21st century. CRAB infections are a leading cause of death attributable to antimicrobial resistance globally(1). Antibiotic resistance in CRAB is mediated through complex mechanisms that include intrinsic and acquired β-lactamases, upregulation of efflux pumps, decreased outer membrane permeability (altered porin channels) and antibiotic target site modifications(2–4). Pneumonia is the primary manifestation of CRAB. MATERIALS AND METHODS: We performed a prospective observational study in which adult patients with culture proven CRAB infections were included. Epidemiological data was recorded and clinical and laboratory data was analyzed to study incidence, risk factors, complications and mortality in patients with CRAB infection. Microbiological data was analyzed to observe susceptibility pattern and resistance mechanism of CRAB isolates. The study intends to provide an experience of the burden of CRAB infections and efficacy of antibiotic combinations in a tertiary care ICU setup in India. RESULTS: Among 2151 consecutive admissions between December 2023 to November 2024, incidence of culture-proven CRAB infection was found to be 14.75 per 1000 (n=35) in our ICU. Mortality in these patients was significantly high (80%) compared to overall mortality in patients admitted in MICU who did not have CRAB infection (19.07%). Average age of study population was 62.28±16.12 years. Higher age was found to be a significant predictor of mortality. Patients predominantly presented with respiratory symptoms (60%). 54.29% of patients were hypertensive and 45.7% patients were diabetic. Pre-existing Diabetes was significantly related to mortality. 62.86% patients had prior exposure to broad spectrum antibiotics in the preceding 3 months. 91.43% patients required invasive mechanical ventilation and 68.57% had refractory shock requiring vasopressors. Mean duration of ventilator support prior to culture positivity was 6.53±4.92 days. Patients predominantly had lung infection (pneumonia). CRAB was isolated from endotracheal samples in 68.57% and from broncho-alveolar lavage (BAL) samples in 17.14%. CRAB was isolated from blood in 5.71% patients. Xpert CARBA-R was done in 45.71% patients and showed NDM as the resistant mechanism. 100% of isolates had intermediate sensitivity to Colistin and Polymyxin B. 22.86% isolates were sensitive to Minocycline and 16.13% isolates were sensitive to Doxycycline. Mean duration of ventilatory support post culture positivity was 11.29±7.74 days. Complications included shock in 54.29%, encephalopathy in 68.57% and need for renal replacement therapy in 34.29%. Combination antibiotic therapy was used in all patients comprising Polymyxin, high dose Sulbactam, and Carbapenem(5,6). In our study, 80% patients received Polymyxin based antibiotic therapy. Best outcome in our study was seen with combination of Polymyxin B, high dose Sulbactam and Meropenem with a mortality of 57.14%. We could not establish clear superiority of any particular combination. CONCLUSION: Our study provides data regarding carbapenem resistant Acinetobacter baumanii and underlines the challenges faced by intensivists treating highly resistant CRAB infection in a developing country. High incidence of resistance to existing antibiotics poses a grave threat and warrants research and development of newer antibiotics to tackle the menace.