Antibiotic resistance and biofilm formation of Acinetobacter baumannii isolated from high risk effluent water in tertiary hospitals in South Africa

Acinetobacter baumannii has become a serious threat to human health due to its extreme antibiotic resistance, environmental persistence, and capacity to survive within the host. Two A. baumannii strains, A118 and AB5075, commonly used as model systems, and three carbapenem-resistant strains, which are becoming ever more dangerous due to the multiple drugs they can resist, were exposed to 3.5% human serum albumin (HSA) and human serum (HS) to evaluate their response with respect to antimicrobial resistance, biofilm formation, and quorum sensing, all features responsible for increasing survival and persistence in the environment and human body. Expression levels of antibiotic resistance genes were modified differently when examined in different strains. The cmlA gene was upregulated or downregulated in conditions of exposure to 3.5% HSA or HS depending on the strain. Expression levels of pbp1 and pbp3 tended to be increased by the presence of HSA and HS, but the effect was not seen in all strains. A. baumannii A118 growing in the presence of HS did not experience increased expression of these genes. Aminoglycoside-modifying enzymes were also expressed at higher or lower levels in the presence of HSA or HS. Still, the response was not uniform; in some cases, expression was enhanced, and in other cases, it was tapered. While A. baumannii AB5075 became more susceptible to rifampicin in the presence of 3.5% HSA or HS, strain A118 did not show any changes. Expression of arr2, a gene involved in resistance to rifampicin present in A. baumannii AMA16, was expressed at higher levels when HS was present in the culture medium. HSA and HS reduced biofilm formation and production of N-Acyl Homoserine Lactone, a compound intimately associated with quorum sensing. In conclusion, HSA, the main component of HS, stimulates a variety of adaptative responses in infecting A. baumannii strains.

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Plasmid-encoded H-NS controls extracellular matrix composition in a modern Acinetobacter baumannii urinary isolate

Journal of Bacteriology ◽

10.1128/jb.00277-21 ◽

2021 ◽

Author(s):

Saida Benomar ◽

Gisela Di Venanzio ◽

Mario F. Feldman

Keyword(s):

Extracellular Matrix ◽

Antibiotic Resistance ◽

Acinetobacter Baumannii ◽

Gene Cluster ◽

Biofilm Formation ◽

Therapeutic Potential ◽

Matrix Composition ◽

Type Vi Secretion System ◽

Gram Negative ◽

Conjugative Plasmids

Acinetobacter baumannii is emerging as a multidrug-resistant (MDR) nosocomial pathogen of increasing threat to human health worldwide. The recent MDR urinary isolate UPAB1 carries the plasmid pAB5, a member of a family of large conjugative plasmids (LCP). LCP encode several antibiotic resistance genes and repress the type VI secretion system (T6SS) to enable their dissemination, employing two TetR transcriptional regulators. Furthermore, pAB5 controls the expression of additional chromosomally encoded genes, impacting UPAB1 virulence. Here we show that a pAB5-encoded H-NS transcriptional regulator represses the synthesis of the exopolysaccharide PNAG and the expression of a previously uncharacterized three-gene cluster that encodes a protein belonging to the CsgG/HfaB family. Members of this protein family are involved in amyloid or polysaccharide formation in other species. Deletion of the CsgG homolog abrogated PNAG production and CUP pili formation, resulting in a subsequent reduction in biofilm formation. Although this gene cluster is widely distributed in Gram-negative bacteria, it remains largely uninvestigated. Our results illustrate the complex cross-talks that take place between plasmids and the chromosomes of their bacterial host, which in this case can contribute to the pathogenesis of Acinetobacter . IMPORTANCE The opportunistic human pathogen Acinetobacter baumannii displays the highest reported rates of multidrug resistance among Gram-negative pathogens. Many A. baumannii strains carry large conjugative plasmids like pAB5. In recent years, we have witnessed an increase in knowledge about the regulatory cross-talks between plasmids and bacterial chromosomes. Here we show that pAB5 controls the composition of the bacterial extracellular matrix, resulting in a drastic reduction in biofilm formation. The association between biofilm formation, virulence, and antibiotic resistance is well-documented. Therefore, understanding the factors involved in the regulation of biofilm formation in Acinetobacter has remarkable therapeutic potential.

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Genomic analysis reveals high virulence and antibiotic resistance amongst phage susceptible Acinetobacter baumannii

Scientific Reports ◽

10.1038/s41598-020-73123-y ◽

2020 ◽

Vol 10 (1) ◽

Author(s):

Udomluk Leungtongkam ◽

Rapee Thummeepak ◽

Thawatchai Kitti ◽

Kannipa Tasanapak ◽

Jintana Wongwigkarn ◽

...

Keyword(s):

Antibiotic Resistance ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Antibiotic Resistance Genes ◽

Genomic Analysis ◽

Multidrug Resistant ◽

Copper Tolerance ◽

Virulence Determinants ◽

Genome Sequences ◽

High Virulence

Abstract In this study, we examined the association between antimicrobial resistance, CRISPR/Cas systems and virulence with phage susceptibility in Acinetobacter baumannii and investigated draft genomes of phage susceptible multidrug resistant A. baumannii strains from Thailand. We investigated 230 A. baumannii strains using 17 lytic A. baumannii phages and the phage susceptibility was 46.5% (107/230). Phage susceptibility was also associated with resistance to numerous antibiotics (p-value < 0.05). We also found association between biofilm formation and the presence of ompA gene among phage susceptible A. baumannii strains (p-value < 0.05). A. baumannii isolates carrying cas5 or combinations of two or three other cas genes, showed a significant increase in phage resistance. Whole-genome sequences of seven phage susceptible A. baumannii isolates revealed that six groups of antibiotic resistance genes were carried by all seven phage susceptible A. baumannii. All strains carried biofilm associated genes and two strains harbored complete prophages, acquired copper tolerance genes, and CRISPR-associated (cas) genes. In conclusion, our data exhibits an association between virulence determinants and biofilm formation among phage susceptible A. baumannii strains. These data help to understand the bacterial co-evolution with phages.

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Comparative analysis of carbapenemases, RND family efflux pumps and biofilm formation potential among Acinetobacter baumannii strains with different carbapenem susceptibility

BMC Infectious Diseases ◽

10.1186/s12879-021-06529-2 ◽

2021 ◽

Vol 21 (1) ◽

Author(s):

Yanpeng Zhang ◽

Bing Fan ◽

Yong Luo ◽

Zhiyuan Tao ◽

Yongbo Nie ◽

...

Keyword(s):

Cell Division ◽

Comparative Analysis ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Carbapenem Resistance ◽

Efflux Pumps ◽

Relative Expression ◽

Formation Potential ◽

Tertiary Hospitals

Abstract Aim This study has conducted a comparative analysis of common carbapenemases harboring, the expression of resistance-nodulation-cell division (RND) family efflux pumps, and biofilm formation potential associated with carbapenem resistance among Acinetobacter baumannii (A. baumannii) strains with different carbapenem susceptibility. Methods: A total of 90 isolates of A. baumannii from two tertiary hospitals of China were identified and grouped as carbapenem susceptible A. baumannii (CSAB) strains and carbapenem non-susceptible A. baumannii (CnSAB) strains based on the susceptibility to imipenem. Harboring of carbapenemase genes, relative expression of RND family efflux pumps and biofilm formation potential were compared between the two groups. Result: Among these strains, 12 (13.3 %) strains were divided into the CSAB group, and 78 (86.7 %) strains into the CnSAB group. Compared with CSAB strains, CnSAB strains increased distribution of blaOXA−23 (p < 0.001) and ISAba1/blaOXA−51−like (p = 0.034) carbapenemase genes, and a 6.1-fold relative expression of adeB (p = 0.002), while CSAB strains led to biofilm formation by 1.3-fold than CnSAB strains (p = 0.021). Conclusions Clinically, harboring more blaOXA−23−like and ISAba1/blaOXA−51−like complex genes and overproduction of adeABC are relevant with carbapenem resistance, while carbapenem susceptible strains might survive the stress of antibiotic through their ability of higher biofilm formation.

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Proteomic and Systematic Functional Profiling Unveils Citral Targeting Antibiotic Resistance, Antioxidant Defense, and Biofilm-Associated Two-Component Systems of Acinetobacter baumannii To Encumber Biofilm and Virulence Traits

mSystems ◽

10.1128/msystems.00986-20 ◽

2020 ◽

Vol 5 (6) ◽

Author(s):

Anthonymuthu Selvaraj ◽

Alaguvel Valliammai ◽

Pandiyan Muthuramalingam ◽

Sivasamy Sethupathy ◽

Ganapathy Ashwinkumar Subramenium ◽

...

Keyword(s):

Antibiotic Resistance ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Antioxidant Defense ◽

Time Of Flight ◽

Differentially Expressed ◽

Secretion Systems ◽

Content Type ◽

Network Analyses ◽

Wide Range

ABSTRACT Acinetobacter baumannii has been reported as a multidrug-resistant bacterium due to biofilms and antimicrobial resistance mechanisms. Hence, novel therapeutic strategies are necessary to overcome A. baumannii infections. This study revealed that citral at 200 μg/ml attenuated A. baumannii biofilms by up to 90% without affecting viability. Furthermore, microscopic analyses and in vitro assays confirmed the antibiofilm efficacy of citral. The global effect of citral on A. baumannii was evaluated by proteomic, transcriptional, and in silico approaches. Two-dimensional (2D) gel electrophoresis and matrix-assisted laser desorption ionization–time of flight/time of flight (MALDI-TOF/TOF) analyses were used to assess the effect of citral on the A. baumannii cellular proteome. Quantitative real-time PCR (qPCR) analysis was done to validate the proteomic data and identify the differentially expressed A. baumannii genes. Protein-protein interactions, gene enrichment, and comparative gene network analyses were performed to explore the interactions and functional attributes of differentially expressed proteins of A. baumannii. Global omics-based analyses revealed that citral targeted various mechanisms such as biofilm formation, antibiotic resistance, antioxidant defense, iron acquisition, and type II and type IV secretion systems. The results of antioxidant analyses and antibiotic sensitivity, blood survival, lipase, and hemolysis assays validated the proteomic results. Cytotoxicity analysis showed a nontoxic effect of citral on peripheral blood mononuclear cells (PBMCs). Overall, the current study unveiled that citral has multitarget efficacy to inhibit the biofilm formation and virulence of A. baumannii. IMPORTANCE Acinetobacter baumannii is a nosocomial-infection-causing bacterium and also possesses multidrug resistance to a wide range of conventional antibiotics. The biofilm-forming ability of A. baumannii plays a major role in its resistance and persistence. There is an alarming need for novel treatment strategies to control A. baumannii biofilm-associated issues. The present study demonstrated the strong antibiofilm and antivirulence efficacy of citral against A. baumannii. In addition, proteomic analysis revealed the multitarget potential of citral against A. baumannii. Furthermore, citral treatment enhances the susceptibility of A. baumannii to the host innate immune system and reactive oxygen species (ROS). Cytotoxicity analysis revealed the nonfatal effect of citral on human PBMCs. Therefore, citral could be the safest therapeutic compound and can be taken for further clinical evaluation for the treatment of biofilm-associated infections by A. baumannii.

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Clinical Significance, Antibiotic Resistance and Biofilm Formation of Acinetobacter baumannii: Review.

Clinical Microbiology Open Access ◽

10.4172/2327-5073.1000315 ◽

2018 ◽

Vol 07 (04) ◽

Author(s):

Sasidhar Sindhu

Keyword(s):

Antibiotic Resistance ◽

Acinetobacter Baumannii ◽

Clinical Significance ◽

Biofilm Formation

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Biofilm-Formation in Clonally Unrelated Multidrug-Resistant Acinetobacter baumannii Isolates

Pathogens ◽

10.3390/pathogens9080630 ◽

2020 ◽

Vol 9 (8) ◽

pp. 630 ◽

Cited By ~ 1

Author(s):

Aisha M. Alamri ◽

Afnan A. Alsultan ◽

Mohammad A. Ansari ◽

Amani M. Alnimr

Keyword(s):

Tissue Culture ◽

Antibiotic Resistance ◽

Acinetobacter Baumannii ◽

Congo Red ◽

Biofilm Formation ◽

Multidrug Resistant ◽

Control Measures ◽

Infection Control Measures ◽

Culture Plate ◽

Tissue Culture Plate

This study analyzed the genotype, antibiotic resistance, and biofilm formation of Acinetobacter baumannii strains and assessed the correlation between biofilm formation, antibiotic resistance, and biofilm-related risk factors. A total of 207 non-replicate multi-drug-resistant A. baumannii strains were prospectively isolated. Phenotypic identification and antimicrobial susceptibility testing were carried out. Isolate biofilm formation ability was evaluated using the tissue culture plate (TCP), Congo red agar, and tube methods. Clonal relatedness between the strains was assessed by enterobacterial repetitive intergenic consensus-PCR genotyping. Of the 207 isolates, 52.5% originated from an intensive care unit setting, and pan resistance was observed against ceftazidime and cefepime, with elevated resistance (99–94%) to piperacillin/tazobactam, imipenem, levofloxacin, and ciprofloxacin. alongside high susceptibility to tigecycline (97.8%). The Tissue culture plate, Tube method, and Congo red agar methods revealed that 53.6%, 20.8%, and 2.7% of the strains were strong biofilm producers, respectively, while a significant correlation was observed between biofilm formation and device-originating respiratory isolates (p = 0.0009) and between biofilm formation in colonized vs. true infection isolates (p = 0.0001). No correlation was detected between antibiotic resistance and biofilm formation capacity, and the majority of isolates were clonally unrelated. These findings highlight the urgent need for implementing strict infection control measures in clinical settings.

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Relationship between Antibiotic Resistance, Biofilm Formation, and Biofilm-Specific Resistance in Acinetobacter baumannii

Frontiers in Microbiology ◽

10.3389/fmicb.2016.00483 ◽

2016 ◽

Vol 7 ◽

Cited By ~ 86

Author(s):

Lihua Qi ◽

Hao Li ◽

Chuanfu Zhang ◽

Beibei Liang ◽

Jie Li ◽

...

Keyword(s):

Antibiotic Resistance ◽

Acinetobacter Baumannii ◽

Biofilm Formation ◽

Specific Resistance

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Defining Gene-Phenotype Relationships in Acinetobacter baumannii through One-Step Chromosomal Gene Inactivation

mBio ◽

10.1128/mbio.01313-14 ◽

2014 ◽

Vol 5 (4) ◽

Cited By ~ 67

Author(s):

Ashley T. Tucker ◽

Emily M. Nowicki ◽

Joseph M. Boll ◽

Gregory A. Knauf ◽

Nora C. Burdis ◽

...

Keyword(s):

Oxidative Stress ◽

Antibiotic Resistance ◽

Acinetobacter Baumannii ◽

Genome Editing ◽

Biofilm Formation ◽

Content Type ◽

Stress Protection ◽

Biocide Resistance ◽

Hospital Acquired ◽

Oxidative Stress Protection

ABSTRACTRates of infection with hospital-acquiredAcinetobacter baumanniihave exploded over the past decade due to our inability to limit persistence and effectively treat disease.A. baumanniiquickly acquires antibiotic resistance, and its genome encodes mechanisms to tolerate biocides and desiccation, which enhance its persistence in hospital settings. With depleted antibiotic options, new methods to treatA. baumanniiinfections are desperately needed. A comprehensive understanding detailingA. baumanniicellular factors that contribute to its resiliency at genetic and mechanistic levels is vital to the development of new treatment options. Tools to rapidly dissect theA. baumanniigenome will facilitate this goal by quickly advancing our understanding ofA. baumanniigene-phenotype relationships. We describe here a recombination-mediated genetic engineering (recombineering) system for targeted genome editing ofA. baumannii. We have demonstrated that this system can perform directed mutagenesis on wide-ranging genes and operons and is functional in various strains ofA. baumannii, indicating its broad application. We utilized this system to investigate key gene-phenotype relationships inA. baumanniibiology important to infection and persistence in hospitals, including oxidative stress protection, biocide resistance mechanisms, and biofilm formation. In addition, we have demonstrated that both the formation and movement of type IV pili play an important role inA. baumanniibiofilm.IMPORTANCEAcinetobacter baumanniiis the causative agent of hospital-acquired infections, including pneumonia and serious blood and wound infections.A. baumanniiis an emerging pathogen and has become a threat to public health because it quickly develops antibiotic resistance, making treatment difficult or impossible. While the threat ofA. baumanniiis well recognized, our understanding of even its most basic biology lags behind. Analysis ofA. baumanniicellular functions to identify potential targets for drug development has stalled due in part to laborious genetic techniques. Here we have pioneered a novel recombineering system that facilitates efficient genome editing inA. baumanniiby single PCR products. This technology allows for rapid genome editing to quickly ascertain gene-phenotype relationships. To demonstrate the power of recombineering in dissectingA. baumanniibiology, we use this system to establish key gene-phenotype relationships important to infection and persistence in hospitals, including oxidative stress protection, biocide resistance, and biofilm formation.

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