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Chen J, Li G, Shao Y, Cheng Z, Wan F, Wu D, Wei D, Liu P, Du F, Liu Y. Clinical, phenotypic characterization and genomic analysis of the mucoid Acinetobacter baumannii from a teaching hospital. Microb Pathog 2024; 196:106929. [PMID: 39270758 DOI: 10.1016/j.micpath.2024.106929] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2024] [Revised: 09/02/2024] [Accepted: 09/10/2024] [Indexed: 09/15/2024]
Abstract
BACKGROUND Acinetobacter baumannii (A. baumannii) has become a significant nosocomial pathogen globally over the past decade due to the increasing prevalence of antibiotic-resistant isolates. The formation of the mucoid phenotype is a crucial adaptive defense response to external pressure, but the clinical, phenotypic and genotypic characteristics and their relationship with sequence types (ST) and K locus (KL) types remain unclear. METHODS In this study, we screened a total of 736 A. baumannii isolates, from which we identified and characterized 13 mucoid isolates. The study explored the clinical characteristics of patients with mucoid isolates, investigated the mucoid phenotype, performed capsule observation, quantified capsule production, and assessed antimicrobial susceptibility. Subsequently, whole-genome sequencing (WGS) was used to analyze the sequence types (ST), loci for capsular polysaccharide (KL), antibiotic resistance genes, virulence genes, and core-genome single-nucleotide polymorphisms (SNPs). Additionally, the virulence of all mucoid strains was evaluated through serum resistance assay, biofilm-forming assay, and Galleria mellonella survival assay. RESULTS All mucoid A. baumannii isolates were found to be encapsulated and extremely drug-resistant. Among patients infected with these isolates, 92.3 % had pulmonary infections, and the 30-day mortality rate was 61.5 %. The analysis revealed that not all strains are highly virulent. Whole-genome sequencing (WGS) identified the sequence types as ST136, ST208, ST381, ST195, and ST281, and the capsular types as KL77, KL7, KL33, KL2, and KL3. The ST208 and KL7 isolates exhibited higher virulence and greater biofilm formation, with KL7 isolates also showing higher capsule production. Despite these differences, no significant variations in virulence genes were observed among the mucoid isolates, except for biofilm-associated and quorum-sensing genes. The highly virulent ST208/KL7 strains (AB276, AB313, and AB552) lacked biofilm-associated genes (csuA/BABCDE), indicating these genes do not directly cause differences in biofilm formation. CONCLUSION The mucoid A. baumannii isolates were extensively drug-resistant, and infections caused by these isolates could lead to higher mortality. However, not all strains had high virulence, with variations likely related to specific sequence types (ST) and K locus (KL) types.
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Affiliation(s)
- Jiao Chen
- School of Laboratory Medicine, Nanchang Medical College, PR China
| | - Guanghui Li
- School of Information Engineering, East China Jiaotong University, PR China
| | - Yanting Shao
- School of Laboratory Medicine, Nanchang Medical College, PR China
| | - Zhibin Cheng
- School of Laboratory Medicine, Nanchang Medical College, PR China
| | - Fen Wan
- School of Laboratory Medicine, Nanchang Medical College, PR China
| | - Danqin Wu
- Neurology ICU, The First Affiliated Hospital of Nanchang University, PR China
| | - Dandan Wei
- Department of Clinical Microbiology, The First Affiliated Hospital of Nanchang University, PR China; Clinical Laboratory, China-Japan Friendship JiangXi Hospital, PR China
| | - Peng Liu
- Department of Clinical Microbiology, The First Affiliated Hospital of Nanchang University, PR China
| | - Fangling Du
- Department of Clinical Microbiology, The First Affiliated Hospital of Nanchang University, PR China
| | - Yang Liu
- Department of Clinical Microbiology, The First Affiliated Hospital of Nanchang University, PR China; Clinical Laboratory, China-Japan Friendship JiangXi Hospital, PR China.
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Ji C, Guo W, Amir H. Experience of diagnosis and treatment of hard-to-heal wounds infected with Acinetobacter baumannii: a case study. J Wound Care 2024; 33:278-285. [PMID: 38573906 DOI: 10.12968/jowc.2024.33.4.278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/06/2024]
Abstract
OBJECTIVE To explore the efficacy of 0.01% hypochlorous acid (HOCl) in the treatment of hard-to-heal wounds infected by multidrug-resistant Acinetobacter baumannii. METHOD We report a case of hard-to-heal wounds on a patient's forearms that were infected by Acinetobacter baumannii. The wounds were treated with 0.01% HOCl. We reviewed the relevant literature and discussed the definition, epidemiology and pathogenesis of hard-to-heal wounds infected by Acinetobacter baumannii. We also explored the safety and efficacy of 0.01% HOCl for the treatment of hard-to-heal wounds infected with Acinetobacter baumannii. RESULTS After 3-4 weeks of treatment with 0.01% HOCl, the pain and pruritus of the wounds was gradually alleviated, the infection was controlled and the granulation tissue was fresh. The ulcers also shrank and the nutritional condition of the patient improved. In the fifth week, the skin of the patient's right thigh was grafted to repair the wounds, which then healed within 18 days. During the three years of follow-up, the patient had no relapse. CONCLUSION In our case, the 0.01% HOCl seemed to effectively inactivate the bacterial biological biofilm. This helped to promote wound healing, and was non-toxic to the tissues. We consider low-concentration HOCl to be safe and effective for the treatment of hard-to-heal wounds infected with Acinetobacter baumannii.
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Affiliation(s)
- Chaochao Ji
- The Second Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, Zhejiang Province, China
| | - Wenyong Guo
- Institute of Basic Clinical Medicine, China Academy of Chinese Medical Sciences, Beijing, China
| | - Hammad Amir
- The Second Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, Zhejiang Province, China
- Zhejiang Chinese Medical University, Hangzhou, Zhejiang Province, China
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Bjånes E, Koh T, Qayum T, Zurich R, McCabe S, Hampel K, Cartwright L, Nizet V. Exploring Roles of the Polysaccharide Capsule in Pathogenesis of Hypervirulent Acinetobacter baumannii Clinical Isolate Lac-4. Antibiotics (Basel) 2023; 13:10. [PMID: 38275320 PMCID: PMC10812722 DOI: 10.3390/antibiotics13010010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2023] [Revised: 12/15/2023] [Accepted: 12/18/2023] [Indexed: 01/27/2024] Open
Abstract
The frequently multidrug-resistant bacterial pathogen Acinetobacter baumannii is a leading cause of nosocomial infections, including ventilator-associated pneumonia, such that the World Health Organization and US Centers for Disease Control and Prevention have declared it a top priority candidate for novel drug development. Nearly all clinical A. baumannii strains express a thick surface polysaccharide capsule that protects against desiccation, host defenses, and disinfectants. In this study, we investigated the contribution of the polysaccharide capsule to virulence caused by the A. baumannii clinical isolate Ab Lac-4, which is rare in its ability to cause pneumonia and disseminated sepsis in healthy mice. We assessed the role of the capsule in wildtype Lac-4 (WT) by generating a premature stop codon in wza, which codes for the polysaccharide export protein. The wza# mutant was hypersensitive to killing by complement, whole blood, and healthy human neutrophils compared to WT and a revertant mutant (wza-Rev). Furthermore, the wza# mutant was highly attenuated in murine sepsis and unable to disseminate from the lungs during pneumonia. This study reinforces the capsule as a key contributor to Ab Lac-4 hypervirulence.
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Affiliation(s)
- Elisabet Bjånes
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Truman Koh
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Tariq Qayum
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Raymond Zurich
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Sinead McCabe
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Kegan Hampel
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Lisa Cartwright
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
| | - Victor Nizet
- Division of Host-Microbe Systems and Therapeutics, Department of Pediatrics, University of California San Diego, La Jolla, CA 92093, USA; (T.K.); (T.Q.); (R.Z.); (S.M.); (K.H.); (L.C.)
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093, USA
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Rakovitsky N, Lurie-Weinberger MN, Hameir A, Wulffhart L, Keren Paz A, Schwartz D, Carmeli Y. Phenotypic and Genomic Characterization of Nine String-Positive Carbapenem-Resistant Acinetobacter baumannii Isolates from Israel. Microbiol Spectr 2023; 11:e0300222. [PMID: 36719216 PMCID: PMC10100839 DOI: 10.1128/spectrum.03002-22] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2022] [Accepted: 01/09/2023] [Indexed: 02/01/2023] Open
Abstract
A positive "string test" indicates the ability of bacterial colonies grown on agar plates to form viscous strings of >5 mm when stretched. This phenotype is strongly associated with hypervirulence in Klebsiella pneumoniae but has never been described in carbapenem-resistant Acinetobacter baumannii (CRAB), an emerging human pathogen of high clinical significance. In this work, we screened 1,000 CRAB isolates, among which we identified and characterized 9 string-positive CRAB (stCRAB) isolates. Phenotypic and genotypic analyses revealed that the isolates were not phylogenetically related and possessed different antibiotic resistance and virulence profiles. Transmission electron microscopy (TEM) showed the presence of capsule in string-positive isolates. String-positive isolates were more motile but did not form more biofilm than non-string-positive isolates. They were less virulent in a murine thigh fitness model and a Galleria mellonella survival assay. In conclusion, here, we describe string-positive A. baumannii isolates and their phenotypic and molecular characteristics. We found that unlike K. pneumoniae, stCRAB isolates were not associated with increased virulence. IMPORTANCE Acinetobacter baumannii has been considered a major health care threat in recent years. Despite many efforts, the pathogenesis and molecular mechanism of A. baumannii virulence remain poorly understood. Moreover, the plasticity of its genome frequently gives rise to new and more virulent isolates. Our current study is of significant importance as it concerns a previously undescribed A. baumannii phenotype. The string-positive phenotype is strongly associated with increased fitness and virulence in other Gram-negative bacteria such as K. pneumoniae. Although no clear correlation with virulence or fitness was found in our 9 stCRAB isolates, this could have been due to the limited statistical power of our research. We suggest that this phenotype should be taken into consideration as due to its genome plasticity, the next change can give rise to string-positive and hypervirulent strains, as is known for K. pneumoniae. Additional future research is needed regarding its possible consequences.
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Affiliation(s)
- Nadya Rakovitsky
- National Institute for Antibiotic Resistance and Infection Control, Israel Ministry of Health, Tel Aviv, Israel
| | - Mor N. Lurie-Weinberger
- National Institute for Antibiotic Resistance and Infection Control, Israel Ministry of Health, Tel Aviv, Israel
| | - Amichay Hameir
- National Institute for Antibiotic Resistance and Infection Control, Israel Ministry of Health, Tel Aviv, Israel
| | - Liat Wulffhart
- National Institute for Antibiotic Resistance and Infection Control, Israel Ministry of Health, Tel Aviv, Israel
| | - Alona Keren Paz
- National Institute for Antibiotic Resistance and Infection Control, Israel Ministry of Health, Tel Aviv, Israel
| | - David Schwartz
- National Institute for Antibiotic Resistance and Infection Control, Israel Ministry of Health, Tel Aviv, Israel
| | - Yehuda Carmeli
- National Institute for Antibiotic Resistance and Infection Control, Israel Ministry of Health, Tel Aviv, Israel
- Sackler School of Medicine, Tel Aviv University, Tel Aviv, Israel
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Insights into mucoid Acinetobacter baumannii: A review of microbiological characteristics, virulence, and pathogenic mechanisms in a threatening nosocomial pathogen. Microbiol Res 2022; 261:127057. [DOI: 10.1016/j.micres.2022.127057] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2021] [Revised: 04/29/2022] [Accepted: 04/29/2022] [Indexed: 01/25/2023]
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Tickner J, Hawas S, Totsika M, Kenyon JJ. The Wzi outer membrane protein mediates assembly of a tight capsular polysaccharide layer on the Acinetobacter baumannii cell surface. Sci Rep 2021; 11:21741. [PMID: 34741090 PMCID: PMC8571296 DOI: 10.1038/s41598-021-01206-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Accepted: 10/19/2021] [Indexed: 11/30/2022] Open
Abstract
Identification of novel therapeutic targets is required for developing alternate strategies to treat infections caused by the extensively drug-resistant bacterial pathogen, Acinetobacter baumannii. As capsular polysaccharide (CPS) is a prime virulence determinant required for evasion of host immune defenses, understanding the pathways for synthesis and assembly of this discrete cell-surface barrier is important. In this study, we assess cell-bound and cell-free CPS material from A. baumannii AB5075 wildtype and transposon library mutants and demonstrate that the Wzi outer membrane protein is required for the proper assembly of the CPS layer on the cell surface. Loss of Wzi resulted in an estimated 4.4-fold reduction in cell-associated CPS with a reciprocal increase in CPS material shed in the extracellular surrounds. Transmission electron microscopy revealed a disrupted CPS layer with sparse patches of CPS on the external face of the outer membrane when Wzi function was lost. However, this genotype did not have a significant effect on biofilm formation. Genetic analysis demonstrated that the wzi gene is ubiquitous in the species, though the nucleotide sequences were surprisingly diverse. Though divergence was not concomitant with variation at the CPS biosynthesis K locus, an association between wzi type and the first sugar of the CPS representing the base of the structure most likely to interact with Wzi was observed.
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Affiliation(s)
- Jacob Tickner
- grid.1024.70000000089150953Centre of Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Australia
| | - Sophia Hawas
- grid.1024.70000000089150953Centre of Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Australia
| | - Makrina Totsika
- grid.1024.70000000089150953Centre of Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Australia
| | - Johanna J. Kenyon
- grid.1024.70000000089150953Centre of Immunology and Infection Control, School of Biomedical Sciences, Faculty of Health, Queensland University of Technology, Brisbane, Australia
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