Acquired mucoid phenotype of Acinetobacter baumannii: Impact for the molecular characteristics and virulence

Shan, Wulin; Zhang, Huanhuan; Kan, Jinsong; Yin, Meiling; Zhang, Jiayun; Wan, Lingling; Chang, Renliang; Li, Ming

doi:10.1016/j.micres.2021.126702

Cited by 12 publications

(7 citation statements)

References 30 publications

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“…The virulence in G. mellonella model varied for the tested clinical isolates and the reference strains and while a constitutive mucoid phenotype does not correlate with a higher virulence, we confirm using modern clinical isolates that low capsule production impedes virulence in A. baumannii . These observations do not confirm the results of Shan et al, (Shan et al, 2021) who concluded that the mucoid A. baumannii isolates were more hypervirulent than the nonmucoid strains. This discrepancy may point towards multifactorial background of hypervirulence and the tested conditions used.…”

Section: Discussioncontrasting

confidence: 97%

What are the reference strains of Acinetobacter baumannii referring to?

Philippe

Valček

Whiteway

et al. 2022

Preprint

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We assembled the whole genome sequence (WGS) of a collection of 43 non-redundant modern clinical isolates and four broadly used reference strains of Acinetobacter baumannii. Comparison of these isolates and their WGS confirmed the high heterogeneity in capsule loci, sequence types, the presence of virulence and antibiotic resistance genes. However, a significant portion of clinical isolates strongly differ when compared to several reference strains in the light of colony morphology, cellular density, capsule production, natural transformability and in vivo virulence. These genetic and phenotypic differences between current circulating strains of A. baumannii and established reference strains could hamper the study of A. baumannii as an entity. The broadly used reference strains led to the current state of the art of the A. baumannii field, however, we propose that established reference strains in the A. baumannii field should be carefully used, because of the high genetic and phenotypic heterogeneities. In this study, we generated a collection of high-quality nucleotide sequences of 43 modern and non-redundant clinical isolates with the corresponding multi-level phenotypic characterizations. Beside the contribution of novel fundamental observations generated in this study, the phenotypic and genetic data, along with the bacterial strains themselves, will be further accessible using the first open access online platform called Acinetobase. Therefore, a rational choice of modern strains will be possible to select the ones that suit the needs of specific biological questions.

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Section: Discussioncontrasting

confidence: 97%

What are the reference strains of Acinetobacter baumannii referring to?

Philippe

Valček

Whiteway

et al. 2022

Preprint

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“…However, although there is no resistance genes including aac(6')-lb-cr, msr(E), mph(E), and sul1/sul2, the HM strain shows resistance to ciprofloxacin, clindamycin, erythromycin, and trimethoprim/sulfamethoxazole (Table 1, Supplementary Table 4, and Supplementary Figure 1A). It consists with the previous observation that decreased drug penetration contributes to antibiotic resistance in mucoid A. baumannii isolates (6). Taken together, the HM strain is MDR with poor biofilm-forming ability and high toxicity.…”

Section: Mucoid Phenotype Biofilm-forming Ability and Toxicity Of Aci...supporting

confidence: 85%

“…It is estimated that there are more than 45,000 infections in the United States, and one million cases globally per year caused by such pathogen ( 5 ). Recently, mucoid A. baumannii isolates, often associated with chronic infections, are multidrug resistant (MDR) with altered bacterial virulence ( 6 ). Besides, the increased blood derived isolates suggest the occurrence of phagocytic resistance in A. baumannii ( 7 ).…”

Section: Introductionmentioning

confidence: 99%

“…Due to the overproduction of capsular polysaccharide, mucoidity phenotype is an important adaptive defense response to the external pressure in pathogens ( 6 , 9 ). Previous works have showed that matt (not glossy) A. baumannii strains evolve to the mucoid phenotype in vivo , and antibiotics such as chloramphenicol and erythromycin could promote the bacterial hypermucoid state ( 10 , 11 ).…”

Section: Introductionmentioning

confidence: 99%

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Mucoid Acinetobacter baumannii enhances anti-phagocytosis through reducing C3b deposition

Gong

Zhao

et al. 2022

Front. Med.

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Background: Multidrug resistant (MDR) Acinetobacter baumannii causes serious infections in intensive care units and is hard to be eradicated by antibiotics. Many A. baumannii isolates are identified as the mucoid type recently, but the biological characteristics of mucoid A. baumannii and their interactions with host cells remains unclear.Methods: The mucoid phenotype, antimicrobial susceptibility, biofilmforming ability, acid resistance ability, peroxide tolerance, and in vivo toxicity of clinical ICUs derived A. baumannii isolates were first investigated. Secondly, the phagocytic resistance and invasive capacity of A. baumannii isolates to macrophages (MH-S, RAW264.7) and epithelial cells (A549) were analyzed. Furthermore, the abundance of C3b (complement factor C3 degradation product) deposition on the surface of A. baumannii was investigated. Last, the relationship between C3b deposition and the abundance of capsule in A. baumannii isolates were analyzed.Results: These A. baumannii strains showed different mucoid phenotypes including hyper mucoid (HM), medium mucoid (MM), and low mucoid (LM). All tested strains were MDR with high tolerance to either acid or hydrogen peroxide exposure. Notably, these mucoid strains showed the increase of mortality in the Galleria mellonella infection models. Besides, the HM strain exhibited less biofilm abundance, higher molecular weight (MW) of capsule, and greater anti-phagocytic activity to macrophages than the LM strain. Together with the increased abundance of capsule, high expression of tuf gene (associated with the hydrolysis of C3b), the HM strain effectively inhibits C3b deposition on bacterial surface, resulting in the low-opsonization phenotype.

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“…Mucoid phenotype formation may influence the virulence of pathogenic microorganisms to varying degrees, which has allowed to make significant strides in characterizing the determinants of pathogenic mechanisms in P. aeruginosa and Klebsiella pneumoniae ( Dennis et al, 2018 ; Ding et al, 2022 ). A previous study has demonstrated that mucoid A. baumannii strains were more virulent than non-mucoid isolates ( Shan et al, 2021 ). Therefore, we analyzed the virulence of AP2044 strain by developing a Galleria mellonella infection model.…”

Section: Resultsmentioning

confidence: 99%

Phenotypic and Genotypic Characteristics of a Tigecycline-Resistant Acinetobacter pittii Isolate Carrying blaNDM–1 and the Novel blaOXA Allelic Variant blaOXA–1045

Ding

Zhao

et al. 2022

Front. Microbiol.

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A tigecycline-resistant Acinetobacter pittii clinical strain from pleural fluid carrying a blaNDM–1 gene and a novel blaOXA gene, blaOXA–1045, was isolated and characterized. The AP2044 strain acquired two copies of the blaNDM–1 gene and six antibiotic resistance genes (ARGs) from other pathogens. According to the whole-genome investigation, the GC ratios of ARGs (50–60%) were greater than those of the chromosomal backbone (39.46%), indicating that ARGs were horizontally transferred. OXA-1045 belonged to the OXA-213 subfamily and the amino acid sequence of OXA-1045 showed 89% similarity to the amino acid sequences of OXA-213. Then, blaOXA–1045 and blaOXA–213 were cloned and the minimum inhibitory concentrations (MICs) of β-lactams in the transformants were determined using the broth microdilution method. OXA-1045 was able to confer a reduced susceptibility to piperacillin and piperacillin-tazobactam compared to OXA-213. AP2044 strain exhibited low pathogenicity in Galleria mellonella infection models. The observation of condensed biofilm using the crystal violet staining method and scanning electron microscopy (SEM) suggested that the AP2044 strain was a weak biofilm producer. Quantitative reverse transcription-PCR (qRT-PCR) was used to detect the expression of resistance-nodulation-cell division (RND) efflux pump-related genes. The transcription level of adeB and adeJ genes increased significantly and was correlated with tigecycline resistance. Therefore, our genomic and phenotypic investigations revealed that the AP2044 strain had significant genome plasticity and natural transformation potential, and the emergence of antibiotic resistance in these unusual bacteria should be a concern for future investigations.

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Acquired mucoid phenotype of Acinetobacter baumannii: Impact for the molecular characteristics and virulence

Cited by 12 publications

References 30 publications

What are the reference strains of Acinetobacter baumannii referring to?

What are the reference strains of Acinetobacter baumannii referring to?

Mucoid Acinetobacter baumannii enhances anti-phagocytosis through reducing C3b deposition

Phenotypic and Genotypic Characteristics of a Tigecycline-Resistant Acinetobacter pittii Isolate Carrying blaNDM–1 and the Novel blaOXA Allelic Variant blaOXA–1045

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