Characterisation of pellicle-forming ability in clinical carbapenem-resistant Acinetobacter baumannii

Author:

Ng Heng Kang1,Puah Suat Moi1,Teh Cindy Shuan Ju2,Idris Nuryana2,Chua Kek Heng1

Affiliation:

1. Department of Biomedical Science, Faculty of Medicine, Universiti Malaya, Kuala Lumpur, Malaysia

2. Department of Medical Microbiology, Faculty of Medicine, Universiti Malaya, Kuala Lumpur, Malaysia

Abstract

Background Acinetobacter baumannii was reported to have resistance towards carbapenems and the ability to form an air-liquid biofilm (pellicle) which contributes to their virulence. The GacSA two-component system has been previously shown to play a role in pellicle formation. Therefore, this study aims to detect the presence of gacA and gacS genes in carbapenem-resistant Acinetobacter baumannii (CRAB) isolates recovered from patients in intensive care units and to investigate their pellicle forming ability. Methods The gacS and gacA genes were screened in 96 clinical CRAB isolates using PCR assay. Pellicle formation assay was performed in Mueller Hinton medium and Luria Bertani medium using borosilicate glass tubes and polypropylene plastic tubes. The biomass of the pellicle was quantitated using the crystal violet staining assay. The selected isolates were further assessed for their motility using semi-solid agar and monitored in real-time using real-time cell analyser (RTCA). Results All 96 clinical CRAB isolates carried the gacS and gacA genes, however, only four isolates (AB21, AB34, AB69 and AB97) displayed the ability of pellicle-formation phenotypically. These four pellicle-forming isolates produced robust pellicles in Mueller Hinton medium with better performance in borosilicate glass tubes in which biomass with OD570 ranging from 1.984 ± 0.383 to 2.272 ± 0.376 was recorded. The decrease in cell index starting from 13 hours obtained from the impedance-based RTCA showed that pellicle-forming isolates had entered the growth stage of pellicle development. Conclusion These four pellicle-forming clinical CRAB isolates could be potentially more virulent, therefore further investigation is warranted to provide insights into their pathogenic mechanisms.

Funder

Fundamental Research Grant Scheme from the Malaysian Ministry of Higher Education

Publisher

PeerJ

Subject

General Agricultural and Biological Sciences,General Biochemistry, Genetics and Molecular Biology,General Medicine,General Neuroscience

Reference47 articles.

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4. A simple static biofilm assay for Acinetobacter baumannii;Biswas;Methods in Molecular Biology,2019

5. Novel genes required for surface-associated motility in Acinetobacter baumannii;Blaschke;Current Microbiology,2021

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