Investigation of a carbapenem-resistant Acinetobacter baumanniioutbreak in the surgical unit of a cardiac care center in Karachi, Pakistan

Abstract

Carbapenem-resistant Acinetobacter baumannii(CRAB) poses a significant threat in cardiac surgical units due to its ability to survive on surfaces, intrinsic multidrug resistance, and association with high morbidity and mortality. Between June 15 and June 30, 2025, a tertiary cardiac care center in Karachi, Pakistan, identified an unusual cluster of CRAB infections among post-operative cardiac surgery patients, prompting a systematic outbreak investigation. A  multidisciplinary outbreak response team conducted an investigation on July 1 and July 2, 2025. Cases were defined as patients developing laboratory-confirmed CRAB infections with onset ≥48  h after hospital admission and within 30 days of cardiac surgery. Active case finding included medical record review and surveillance cultures. Direct observations assessed hand hygiene compliance, personal protective equipment (PPE) use, and environmental cleaning using standardized checklists. Environmental surveillance cultures were obtained from high-touch surfaces in operating rooms (ORs) and intensive care units. Fingerprint cultures from 10 healthcare workers (five from each setting) were screened for CRAB colonization. Seven patients developed CRAB infections: four ventilator-associated pneumonias (VAPs), two central line-associated bloodstream infections (CLABSIs), and one surgical site infection. The median age was 67 years (range 58–74), and the male-to-female ratio was 6:1. Four patients (57.1%) died, of whom two had VAP and two had CLABSI. All isolates demonstrated identical resistance profiles, including resistance to carbapenems, β -lactams, fluoroquinolones, aminoglycosides, and trimethoprim–sulfamethoxazole, with susceptibility to tigecycline and minocycline. Environmental cultures were negative. Fingerprint cultures identified CRAB colonization on one OR technician’s hands, with a susceptibility profile matching patient isolates. Observational audits revealed suboptimal hand hygiene, inadequate environmental cleaning between procedures, and inadequate compliance with PPE protocols. Our investigation revealed healthcare worker hand colonization and lapses in infection control practices as the primary drivers of CRAB transmission and underscored the critical need for sustained, resource-appropriate infection control interventions and continuous vigilance to prevent multidrug-resistant organism outbreaks in similar healthcare environments.

Keywords

Outbreak investigation / Healthcare-associated infections / Infection control / Operating room hygiene / Carbapenem-resistant Acinetobacter baumannii

Acknowledgments

None.

Funding

None.

Conflict of interest

The authors declare that they have no competing interests.

Author contributions

Conceptualization: Moiz Ahmed Khan, Ahson Memon, Khudabaksh Shaikh
Data curation: Victor Basheer, Margaret Palous, Wajid Ali Khan, Nassim Sheraz
Formal analysis: Moiz Ahmed Khan, Victor Basheer, Margaret Palous
Investigation: Victor Basheer, Margaret Palous Methodology: Moiz Ahmed Khan
Project administration: Moiz Ahmed Khan, Ahson Memon, Khudabaksh Shaikh, Abeer Salim Habib, Sohail Abrar Khan
Supervision: Moiz Ahmed Khan, Arsalan Ilyas
Validation: Moiz Ahmed Khan, Victor Basheer, Margaret Palous
Visualization: Moiz Ahmed Khan
Writing–original draft: Moiz Ahmed Khan
Writing–review & editing: Moiz Ahmed Khan, Abeer Salim Habib

Ethics approval and consent to participate

Ethical approval was not required for this outbreak investigation as it constituted routine public health surveillance activities conducted by the institutional Department of Infection Control for immediate outbreak response and infection control purposes. The investigation was conducted in accordance with standard infection control protocols and institutional guidelines. All patient data were handled confidentially and in compliance with institutional policies for outbreak investigation and reporting.

Consent for publication

Written informed consent for publication was not obtained from individual patients, as this investigation constituted a public health surveillance activity conducted for immediate outbreak control and infection prevention purposes. All data presented have been rigorously de-identified and aggregated to ensure complete patient anonymity, with no personal identifiers, protected health information, or identifiable clinical details included in the manuscript.This approach is in accordance with established ethical guidelines for public health practice and outbreak reporting, where the imperative for timely dissemination of findings to protect public health outweighs the requirement for individual consent, provided confidentiality is strictly maintained. The investigation was performed under the authority of the institutional Department of Infection Control and adhered to internal protocols for outbreak management and data reporting.

Availability of data

All data generated during the course of this project are included in the published article.

Further disclosure

The complete findings of this outbreak investigation were presented in full at the Medical Microbiology and Infectious Diseases Society of Pakistan scientific session during the 46th Annual Conference of the Pakistan Association of Pathologists. This manuscript has not been previously published, nor has it been uploaded to any preprint server.

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