Retrospective cohort study assesses Acinetobacter baumannii prevalence and resistance in ventilator-associated infections.

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Frontiers in Medicine Published April 16, 2026 Medically reviewed April 25, 2026 DOI ↗ By Dr. Amelia Tan, PhD · Internal Medicine & Chronic Disease

Key Takeaway

Note high meropenem resistance (66.4%) in ventilator-associated Acinetobacter baumannii isolates from this South Indian ICU cohort.

This retrospective observational cohort study examined 3,540 non-duplicate clinical isolates obtained from patients in a tertiary-care intensive care unit in South India. The primary focus was on the prevalence and antimicrobial resistance of Acinetobacter baumannii isolated from endotracheal aspirates, a surrogate marker for ventilator-associated infections. Demographic associations and antimicrobial susceptibility patterns were also assessed as secondary outcomes.

The analysis revealed that 20.2% of all isolates were multidrug-resistant (MDR). Resistance rates were particularly high for meropenem (66.4%), imipenem (62.6%), ciprofloxacin (71.8%), and trimethoprim–sulfamethoxazole (53.1%). Isolates were more frequent in males (74%) and patients aged ≥30 years. Among tested agents, amikacin demonstrated the highest discriminatory performance with an AUC of 0.63, though overall discriminatory performance of all tested agents was modest.

Safety data, including adverse events, discontinuations, and tolerability, were not reported. The study acknowledges limitations regarding the modest discriminatory performance of all tested agents. Because this is an observational study, association versus causation is not explicitly distinguished, and in vitro activity does not equate to clinical outcomes. These findings support the use of ICU-specific susceptibility data from endotracheal aspirates to guide empirical therapy and highlight the need for targeted stewardship interventions in high-burden critical care units.

Study Details

Study typeCohort

EvidenceLevel 3

PublishedApr 2026

View Original Abstract ↓

BackgroundMultidrug-resistant (MDR) Acinetobacter baumannii is a major cause of ventilator-associated infections in intensive care units (ICUs), where empirical therapy is often initiated without up-to-date antimicrobial resistance (AMR) surveillance data. This study assessed the prevalence, demographic associations, and antimicrobial susceptibility patterns of MDR A. baumannii isolated from endotracheal (ET) aspirates in a tertiary-care hospital in southern India.MethodsIn this single-center retrospective observational study, 3,540 non-duplicate clinical isolates collected between 2019 and 2025 were analyzed. Bacterial identification and antimicrobial susceptibility testing were performed using the Vitek 2 Compact automated system and the Kirby–Bauer disc diffusion method, with results interpreted in accordance with Clinical and Laboratory Standards Institute (CLSI) performance standards. Receiver operating characteristic (ROC) curve analysis was used to evaluate the discriminatory performance of the commonly used antibiotics, with the results expressed as the area under curve (AUC).ResultsMDR A. baumannii accounted for 20.2% of all isolates, with the highest prevalence among neurosurgical ICU patients (22.1%). Isolates were more frequent in males (74%) and in patients aged ≥30 years. Resistance was highest for carbapenems (meropenem, 66.4%; imipenem, 62.6%), ciprofloxacin (71.8%), and trimethoprim–sulfamethoxazole (53.1%). Amikacin showed the greatest relative activity and the highest AUC (0.63), but overall discriminatory performance of all tested agents was modest.ConclusionMDR Acinetobacter baumannii is highly prevalent in intensive care units in this setting and shows extensive resistance to carbapenems, fluoroquinolones, and other commonly used agents. Although amikacin demonstrated comparatively better in vitro activity and the highest AUC, its modest discriminatory performance indicates limited reliability as monotherapy. These findings support the use of ICU-specific susceptibility data from endotracheal aspirates to guide empirical therapy and highlight the need for targeted stewardship interventions in high-burden critical care units.