Natural Transformation Identified in Acinetobacter baumannii

2016 ◽  
Vol 11 (8) ◽  
pp. 340-340
Keyword(s):  
Acinetobacter Baumannii ◽  
Natural Transformation

scholarly journals Serum Albumin and Ca2+Are Natural Competence Inducers in the Human Pathogen Acinetobacter baumannii

2016 ◽  
Vol 60 (8) ◽  
pp. 4920-4929 ◽  
Author(s):  
German Matias Traglia ◽  
Brettni Quinn ◽  
Sareda T. J. Schramm ◽  
Alfonso Soler-Bistue ◽  
Maria Soledad Ramirez
Keyword(s):  
Acinetobacter Baumannii ◽  
Natural Transformation ◽  
Hospital Environment ◽  
Human Pathogen ◽  
Nosocomial Pathogen ◽  
Natural Competence ◽  
Exogenous Dna ◽  
Content Type ◽  
Resistance Determinants ◽  
Main Protein

ABSTRACTThe increasing frequency of bacteria showing antimicrobial resistance (AMR) raises the menace of entering into a postantibiotic era. Horizontal gene transfer (HGT) is one of the prime reasons for AMR acquisition.Acinetobacter baumanniiis a nosocomial pathogen with outstanding abilities to survive in the hospital environment and to acquire resistance determinants. Its capacity to incorporate exogenous DNA is a major source of AMR genes; however, few studies have addressed this subject. The transformation machinery as well as the factors that induce natural competence inA. baumanniiare unknown. In this study, we demonstrate that naturally competent strain A118 increases its natural transformation frequency upon the addition of Ca2+or albumin. We show thatcomEAandpilQare involved in this process since their expression levels are increased upon the addition of these compounds. An unspecific protein, like casein, does not reproduce this effect, showing that albumin's effect is specific. Our work describes the first specific inducers of natural competence inA. baumannii. Overall, our results suggest that the main protein in blood enhances HGT inA. baumannii, contributing to the increase of AMR in this threatening human pathogen.

scholarly journals Interplay between meropenem and human serum albumin on expression of carbapenem resistance genes and natural competence in Acinetobacter baumannii

2021 ◽  
Author(s):  
Camila Pimentel ◽  
Casin Le ◽  
Marisel Romina Tuttobene ◽  
Tomas Subils ◽  
Brent Nishimura ◽  
...  
Keyword(s):  
Human Serum Albumin ◽  
Serum Albumin ◽  
Human Serum ◽  
Acinetobacter Baumannii ◽  
Resistance Genes ◽  
Natural Transformation ◽  
Natural Competence ◽  
Expression Levels ◽  
Carbapenem Resistant ◽  
Synergistic Enhancement

Acinetobacter baumannii A118, a mostly susceptible strain, and AB5075, carbapenem-resistant, were cultured in L-broth or L-broth with different supplements: 3.5% human serum albumin (HSA), human serum (HS), meropenem, or meropenem plus 3.5% HSA. Natural transformation levels were enhanced in A. baumannii A118 and AB5075 cultured in medium supplemented with 3.5 % HSA. Addition of meropenem plus 3.5% HSA caused synergistic enhancement of natural transformation inA. baumannii A118. Medium containing 3.5% HSA or meropenem enhanced the expression levels of the competence and type IV pilus associated genes. The combination meropenem plus 3.5% HSA produced a synergistic augmentation in the expression levels of many of these genes. The addition of HS, which has a high content of HSA, was also an inducer of these genes. Cultures in medium supplemented with HS or 3.5% HSA also affected resistance genes, which were expressed at higher or lower levels depending on the modification required to enhance resistance. The inducing or repressing activity of these modulators also occurred in three more carbapenem-resistant strains tested. An exception was the A. baumanniiAMA16 blaNDM-1 gene, which was repressed in the presence of 3.5% HSA. In conclusion, HSA produces an enhancement of natural transformation and a modification in expression levels of competence genes and antibiotic resistance. Furthermore, when HSA is combined with carbapenems, which may produce stronger cellular stress, the A. baumannii responds increasing the levels of expression of genes involved in natural competence. This process may favor the acquisition of foreign DNA and accelerate evolution.

scholarly journals Interplay between meropenem and human serum albumin on expression of carbapenem resistance genes and natural competence in Acinetobacter baumannii

2021 ◽  
Author(s):  
Casin Le ◽  
Camila Pimentel ◽  
Marisel R. Tuttobene ◽  
Tomas Subils ◽  
Brent Nishimura ◽  
...  
Keyword(s):  
Human Serum ◽  
Acinetobacter Baumannii ◽  
Resistance Genes ◽  
Natural Transformation ◽  
Expression Levels ◽  
Carbapenem Resistant ◽  
Synergistic Enhancement ◽  
Expression Of Genes ◽  
Foreign Dna ◽  
Accelerate Evolution

Acinetobacter baumannii A118, a mostly susceptible strain and AB5075, carbapenem-resistant, were cultured in Lysogeny broth (LB) or LB with different supplements: 3.5% human serum albumin (HSA), human serum (HS), meropenem, or meropenem plus 3.5% HSA. Natural transformation levels were enhanced in A. baumannii A118 and AB5075 cultured in medium supplemented with 3.5% HSA. Addition of meropenem plus 3.5% HSA caused synergistic enhancement of natural transformation in A. baumannii A118. Medium containing 3.5% HSA or meropenem enhanced the expression levels of the competence and type IV pilus associated genes. The combination meropenem plus 3.5% HSA produced a synergistic enhancement in the expression levels of many of these genes. The addition of HS, which has a high content of HSA, was also an inducer of these genes. Cultures grown in medium supplemented with HS or 3.5% HSA also affected resistance genes, which were expressed at higher or lower levels depending on the modification required to enhance resistance. The inducing or repressing activity of these modulators also occurred in three more carbapenem-resistant strains tested. An exception was the A. baumannii AMA16 bla NDM-1 gene, which was repressed in the presence of 3.5% HSA. In conclusion, HSA produces an enhancement of natural transformation and a modification in expression levels of competence genes and antibiotic resistance. Furthermore, when HSA is combined with carbapenems, which may increase the stress response, the expression of genes involved in natural competence is increased in A. baumannii . This process may favor the acquisition of foreign DNA and accelerate evolution. Importance Acinetobacter baumannii causes a variety of nosocomial- and community-infections that are usually resistant to multiple antimicrobial agents. As new strains acquire more resistance genes, these infections become more difficult to treat and mortality can reach up to 39%. The high genomic plasticity exhibited by A. baumannii must be the consequence of numerous mechanisms that include acquiring foreign DNA and recombination. Here, we describe the ability of A. baumannii to induce competence genes when exposed to environments that resemble those found in the human body during untreated infection or after administration of carbapenems. In this latter scenario expression of genes related to resistance also modify their expression levels such that resistance is increased. The contributions of this article are two-fold. Firstly, when A. baumannii is exposed to products present during infection, it responds, augmenting the ability to capture DNA and accelerate evolution. Secondly, in those conditions, the bacterium also modifies the expression of resistance genes to increase its resistance levels. In summary, recognition of substances that are naturally (e.g., HSA) or artificially (treatment with carbapenems) induces A. baumannii to enhance expression of resistance determinants and genes regulating competence.

scholarly journals Involvement of H-NS in Acinetobacter baumannii’s Natural Transformation

2021 ◽  
Author(s):  
Casin Le ◽  
Camila Pimentel ◽  
Marisel Romina Tuttobene ◽  
Tomás Subils ◽  
Jenny Escalante ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Wild Type Strain ◽  
Natural Transformation ◽  
Regulatory Elements ◽  
Wild Type ◽  
Regulation Of Expression ◽  
Expression Levels ◽  
Expression Of Genes ◽  
Foreign Dna

Most Acinetobacter baumannii strains are naturally competent. Although some information is available about factors that enhance or reduce the frequency of transformation of this bacterium, the regulatory elements and mechanisms are barely understood. In this article, we describe studies on the role of H-NS in the regulation of expression of genes related to natural competency and the ability to uptake foreign DNA. The expression levels of the natural transformation-related genes pilA, pilT, pilQ, comEA, comEC, comF, and drpA were significantly increased in a Δhns derivative of Acinetobacter baumannii A118. Complementation of the mutant with a recombinant plasmid harboring hns restored expression levels of six of these genes (pilT remained expressed at high levels) to those of the wild-type strain. The transformation frequency of the A. baumannii A118 Δhns strain was significantly higher than that of the wild-type. Similar, albeit not identical, effects occurred when hns was deleted from the hypervirulent A. baumannii AB5075 strain. Reduction of gene expression in a few cases was not as pronounced as to reach wild-type levels, and expression of comEA was enhanced further. In conclusion, the expression of all seven transformation-related genes was enhanced after deleting hns in A. baumannii A118 and AB5075, and these modifications are accompanied by an increase in the cells’ transformability. The results demonstrate a role of H-NS in A. baumannii’s natural competence.

scholarly journals Understanding the Role of Host Human Products on the Acquisition of Resistance Traits Through Natural Transformation in Acinetobacter baumannii

2016 ◽  
Vol 3 (suppl_1) ◽  
Author(s):  
Brettni Quinn ◽  
German Matias Traglia ◽  
Meaghan Nguyen ◽  
Alonso Soler Bistue ◽  
Maria Soledad Ramirez
Keyword(s):  
Acinetobacter Baumannii ◽  
Natural Transformation ◽  
Resistance Traits

The effect of sub-inhibitory concentrations of antibiotics on natural transformation in Acinetobacter baumannii

2018 ◽  
Vol 51 (5) ◽  
pp. 809-810 ◽  
Author(s):  
Brettni Quinn ◽  
Jasmine Martinez ◽  
Christine Liu ◽  
Meaghan Nguyen ◽  
Maria Soledad Ramirez
Keyword(s):  
Acinetobacter Baumannii ◽  
Natural Transformation

scholarly journals Acinetobacter baumannii Strain M2 Produces Type IV Pili Which Play a Role in Natural Transformation and Twitching Motility but Not Surface-Associated Motility

mBio ◽  
2013 ◽  
Vol 4 (4) ◽  
Author(s):  
Christian M. Harding ◽  
Erin N. Tracy ◽  
Michael D. Carruthers ◽  
Philip N. Rather ◽  
Luis A. Actis ◽  
...  
Keyword(s):  
Experimental Evidence ◽  
Acinetobacter Baumannii ◽  
Natural Transformation ◽  
Genetic Manipulation ◽  
Opportunistic Pathogen ◽  
Type Iv Pili ◽  
Clinical Isolates ◽  
Twitching Motility ◽  
Content Type ◽  
Type Iv

ABSTRACTAcinetobacter baumanniiis a Gram-negative, opportunistic pathogen. Recently, multipleA. baumanniigenomes have been sequenced; these data have led to the identification of many genes predicted to encode proteins required for the biogenesis of type IV pili (TFP). However, there is no experimental evidence demonstrating thatA. baumanniistrains actually produce functional TFP. Here, we demonstrated thatA. baumanniistrain M2 is naturally transformable and capable of twitching motility, two classical TFP-associated phenotypes. Strains were constructed with mutations inpilA,pilD, andpilT, genes whose products have been well characterized in other systems. These mutants were no longer naturally transformable and did not exhibit twitching motility. These TFP-associated phenotypes were restored when these mutations were complemented. More PilA was detected on the surface of thepilTmutant than the parental strain, and TFP were visualized on thepilTmutant by transmission electron microscopy. Thus,A. baumanniiproduces functional TFP and utilizes TFP for both natural transformation and twitching motility. Several investigators have hypothesized that TFP might be responsible, in part, for the flagellum-independent surface-associated motility exhibited by manyA. baumanniiclinical isolates. We demonstrated that surface-associated motility was not dependent on the products of thepilA,pilD, andpilTgenes and, by correlation, TFP. The identification of functional TFP inA. baumanniilays the foundation for future work determining the role of TFP in models of virulence that partially recapitulate human disease.IMPORTANCESeveral investigators have documented the presence of genes predicted to encode proteins required for the biogenesis of TFP in manyA. baumanniigenomes. Furthermore, some have speculated that TFP may play a role in the unique surface-associated motility phenotype exhibited by manyA. baumanniiclinical isolates, yet there has been no experimental evidence to prove this. Unfortunately, progress in understanding the biology and virulence ofA. baumanniihas been slowed by the difficulty of constructing and complementing mutations in this species. Strain M2, a recently characterized clinical isolate, is amenable to genetic manipulation. We have established a reproducible system for the generation of marked and/or unmarked mutations using a modified recombineering strategy as well as a genetic complementation system utilizing a modified mini-Tn7element in strain M2. Using this strategy, we demonstrated that strain M2 produces TFP and that TFP are not required for surface-associated motility exhibited by strain M2.

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