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Updated: Jul 4, 2025
Rapid and Specific Detection of Acinetobacter baumannii Infections Using a Recombinase Polymerase Amplification/Cas12a-based System
Published on: April 25, 2025
Outbreak caused by pandrug-resistant blaOXA-69/blaOXA-23/blaGES harboring Acinetobacter baumannii ST2 in an intensive
Anis Raddaoui1,2, Aymen Mabrouk1,2, Yosra Chebbi1,2
11Laboratory Ward, National Bone Marrow Transplant Center, 1006 Tunis, Tunisia.
Abstract:
Acinetobacter baumannii has emerged as a main nosocomial pathogen exhibiting high rates of resistance to clinically relevant antibiotics. Six pandrug-resistant A. baumannii (PDR-A. baumannii) were recovered from three patients in a Tunisian Intensive Care Unit (ICU) between 10th and 16th of May 2018 resulting in one fatal case and raising the possibility of an outbreak. On 18th of May environmental screening of ICU surfaces was carried out. On 22nd of May a fourth patient was infected with PDR-A. baumannii and died. A second investigation was carried out for environmental screening and PDR-A. baumannii was isolated from the respirator. Antimicrobial susceptibility testing was performed according to EUCAST (2019) guidelines. MIC of colistin was determined by broth microdilution method. PCR was used to detect 14 beta-lactamases/carbapenemases and mcr (mcr-1 to mcr-5) genes. The genetic relatedness of PDR-A. baumannii isolates was determined by PFGE and MLST. Seven PDR-A. baumannii isolates were recovered from four patients, one MDR strain from wash basin, a PDR strain from hand sanitizer bottle and another PDR strain from respirator. All PDR-A. baumannii (n = 9) harbored blaOXA-69 gene and none carried mcr. Moreover, seven carried blaGES and blaOXA-23 genes. PFGE identified four pulsotypes (A, B, C, and D) with the pulsotype A gathering seven PDR-A. baumannii isolates: six from three patients and one from hygiene sample. MLST revealed that all PDR-A. baumannii isolates of pulsotype A belonged to the pandemic clone ST2. Systematic screening of MDR and PDR-A. baumannii is highly recommended to limit dissemination of such strains in ICUs.
Insights
Pandrug-resistant Acinetobacter baumannii (PDR-A. baumannii) outbreaks in an ICU highlight the need for systematic screening. Environmental contamination, including respirators, played a role in PDR-A. baumannii dissemination.
Area of Science:
- Infectious Diseases
- Microbiology
- Public Health
Background:
- Acinetobacter baumannii is a significant nosocomial pathogen with increasing antibiotic resistance.
- Pandrug-resistant A. baumannii (PDR-A. baumannii) poses a severe threat in healthcare settings, particularly Intensive Care Units (ICUs).
- An outbreak of PDR-A. baumannii in a Tunisian ICU resulted in patient mortality and necessitated urgent investigation.
Purpose of the Study:
- To investigate the source and spread of a PDR-A. baumannii outbreak in a Tunisian ICU.
- To characterize the antimicrobial resistance mechanisms and genetic relatedness of the PDR-A. baumannii isolates.
- To assess the role of environmental contamination in the dissemination of PDR-A. baumannii.
Main Methods:
- Isolation and identification of A. baumannii from patients and ICU environmental surfaces.
- Antimicrobial susceptibility testing (EUCAST guidelines) and Minimum Inhibitory Concentration (MIC) determination for colistin.
- Polymerase Chain Reaction (PCR) for beta-lactamase/carbapenemase and mcr genes detection.
- Pulsed-field gel electrophoresis (PFGE) and Multilocus Sequence Typing (MLST) for genetic relatedness analysis.
Main Results:
- Nine PDR-A. baumannii isolates were recovered from four patients and environmental samples (wash basin, hand sanitizer, respirator).
- All PDR-A. baumannii isolates harbored the blaOXA-69 gene; seven also carried blaGES and blaOXA-23 genes. No mcr genes were detected.
- PFGE identified four pulsotypes, with Pulsotype A (ST2 clone) encompassing seven PDR-A. baumannii isolates from patients and environmental sources.
- The outbreak was linked to the pandemic clone ST2, with environmental contamination, including a respirator, contributing to spread.
Conclusions:
- Environmental contamination, particularly with devices like respirators, can facilitate the spread of PDR-A. baumannii in ICUs.
- The blaOXA-69, blaGES, and blaOXA-23 genes are prevalent in the investigated PDR-A. baumannii strains.
- Systematic screening for multidrug-resistant (MDR) and PDR-A. baumannii is crucial to control dissemination in healthcare settings.
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