Acinetobacter baumannii is one of the most important opportunistic pathogens responsible for hospital acquired infections. It displays multi-drug resistance profile and has the ability to colonize ...surfaces and persist under harsh conditions. A. baumannii two-component signal transduction system BfmRS, consisting of response regulator BfmR and sensor kinase BfmS, has been implicated in the control of various virulence-related traits and has been suggested to act as a global modulator of A. baumannii physiology.
Here, we assessed the role of BfmR regulator in pellicle formation and bacterial competition, features important for the establishment of A. baumannii in clinical environment. We show that BfmR is required for the pellicle formation of A. baumannii, as ΔbfmRS mutant lacked this phenotype. The loss of bfmRS also greatly reduced the secretion of A. baumannii Hcp protein, which is a component of T6SS secretion system. However, T6SS-mediated killing phenotype was not impaired in ΔbfmRS mutant. On the contrary, the same mutation resulted in the transcriptional activation of contact-dependent inhibition (CDI) system, which A. baumannii used to inhibit the growth of another clinical A. baumannii strain and a closely related species Acinetobacter baylyi.
The obtained results indicate that BfmR is not only required for the pellicle phenotype induction in A. baumannii, but also, due to the down-regulation of a CDI system, could allow the incorporation of other A. baumannii strains or related species, possibly increasing the likelihood of the pathogens' survival.
Soil is one of the biggest reservoirs of microbial diversity, yet the processes that define the community dynamics are not fully understood. Apart from soil management being vital for agricultural ...purposes, it is also considered a favorable environment for the evolution and development of antimicrobial resistance, which is due to its high complexity and ongoing competition between the microorganisms. Different approaches to agricultural production might have specific outcomes for soil microbial community composition and antibiotic resistance phenotype. Therefore in this study we aimed to compare the soil microbiota and its resistome in conventional and organic farming systems that are continually influenced by the different treatment (inorganic fertilizers and pesticides vs. organic manure and no chemical pest management). The comparison of the soil microbial communities revealed no major differences among the main phyla of bacteria between the two farming styles with similar soil structure and pH. Only small differences between the lower taxa could be observed indicating that the soil community is stable, with minor shifts in composition being able to handle the different styles of treatment and fertilization. It is still unclear what level of intensity can change microbial composition but current conventional farming in Central Europe demonstrates acceptable level of intensity for soil bacterial communities. When the resistome of the soils was assessed by screening the total soil DNA for clinically relevant and soil-derived antibiotic resistance genes, a low variety of resistance determinants was detected (resistance to β-lactams, aminoglycosides, tetracycline, erythromycin, and rifampicin) with no clear preference for the soil farming type. The same soil samples were also used to isolate antibiotic resistant cultivable bacteria, which were predominated by highly resistant isolates of
and
genera. The resistance of these isolates was largely dependent on the efflux mechanisms, the soil
spp. relying mostly on RND, while
spp. and
spp. on RND and ABC transporters.
Currently,
Acinetobacter baumannii
is considered as one of the most important infectious agents causing hospital acquired infections worldwide. It has been observed that many clinically important ...pathogens express contact-dependent growth inhibition (CDI) phenomenon, which modulates cell–cell and cell–environment interactions, potentially allowing bacteria to adapt to ever-changing conditions. Mainly, these systems are used for the inhibition of the growth of genetically different individuals within the same species. In this work, by performing cell competition assays with three genotypically different (as determined by pulse-field gel electrophoresis) clinical
A. baumannii
isolates II-c, II-a, and II-a1, we show that
A. baumannii
capsule is the main feature protecting from CDI-mediated inhibition. We also observed that for one clinical isolate, the two-component BfmRS system, contributed to the resistance against CDI-mediated inhibition. Moreover, we were able to demonstrate, that the effector protein CdiA is released into the growth media and exhibits its inhibitory activity without the requirement of a cell–cell contact. Lastly, by evaluating the remaining number of the cells pre-mixed with the CdiA and performing live/dead assay, we demonstrate that purified CdiA protein causes a rapid cell growth arrest. Our results indicate, that capsule efficiently protects
A. baumannii
from a CDI-mediated inhibition by a clinical
A. baumannii
V15 strain, which is able to secrete CdiA effector into the growth media and cause target cell growth arrest without a cell–cell contact.
As one of the most diverse habitats of microorganisms, soil has been recognised as a reservoir of both antibiotics and the antibiotic resistance genes (ARGs). Bacteria naturally inhabiting soil or ...water often possess innate ARGs to counteract the chemical compounds produced by competitors living in the same environment. When such bacteria are able to cause infections in immunocompromised patients, their strong innate antibiotic resistance mechanisms make treatment difficult. We generated functional gene libraries using antibiotic-resistant
and
spp. bacteria isolated from agricultural soils in Lithuania to select for the genetic determinants responsible for their resistance. We were able to find novel variants of aminoglycoside and β-lactam resistance genes, with β-lactamases isolated from the
spp. functional gene library, one of which is a variant of IND-like metallo-β-lactamase (MBL) IND-17 and the other of which is a previously uncharacterised MBL we named CHM (
metallo β-lactamase). Our results indicate that soil microorganisms possess a diversity of ARG variants, which could potentially be transferred to the clinical setting.
currently represents one of the most important nosocomial infection agent due to its multidrug-resistance and a propensity for the epidemic spread. The
strains belonging to the international clonal ...lineages I (IC I) and II (IC II) are associated with the hospital outbreaks and a high virulence. However, the intra and inter lineage-specific features of strains belonging to these most worldwide spread
clones are not thoroughly explored. In this study we have investigated a set of cell surface-related features of
IC I (
= 20) and IC II (
= 16) lineage strains, representing 30 distinct pulsed-field gel electrophoresis types in the collection of clinical isolates obtained in Lithuanian tertiary care hospitals. We show that
IC II strains are non-motile, do not form pellicle and display distinct capsular polysaccharide profile compared with the IC I strains. Moreover, in contrast to the overall highly hydrophobic IC I strains, IC II strains showed a greater variation in cell surface hydrophobicity. Within the IC II lineage, hydrophilic strains demonstrated reduced ability to form biofilm and adhere to the abiotic surfaces, also possessed twofold thicker cell wall and exhibited higher resistance to desiccation. Furthermore, these strains showed increased adherence to the lung epithelial cells and were more virulent in nematode and mouse infection model compared with the hydrophobic IC II strains. According to the polymerase chain reaction-based locus-typing, the reduction in hydrophobicity of IC II strains was not capsule or lipooligosaccharide locus type-dependent. Hence, this study shows that the most widespread
clonal lineages I and II markedly differ in the series of cell surface-related phenotypes including the considerable phenotypic diversification of IC II strains at the intra-lineage level. These findings suggest that the genotypically related
strains might evolve the features which could provide an advantage at the specific conditions outside or within the host.
We have previously shown that Acinetobacter baumannii as well as other relevant clinical bacterial pathogens such as Staphylococcus aureus and Pseudomonas aeruginosa, perceive and respond to light at ...37 °C, the normal temperature in mammal hosts. In this work, we present evidence indicating that the two-component system BfmRS transduces a light signal in A. baumannii at this temperature, showing selective involvement of the BfmR and BfmS components depending on the specific cellular process. In fact, both BfmR and BfmS participate in modulation of motility by light, while only BfmR is involved in light regulation of desiccation tolerance in this microorganism. Neither BfmR nor BfmS contain a photoreceptor domain and then most likely, the system is sensing light indirectly. Intriguingly, this system inhibits blsA expression at 37 °C, suggesting antagonistic functioning of both signaling systems. Furthermore, we present evidence indicating that the phosphorylatable form of BfmR represses motility. Overall, we provide experimental evidence on a new biological function of this multifaceted system that broadens our understanding of A. baumannii's physiology and responses to light.
Multidrug resistant Acinetobacter baumannii is one of the major infection agents causing nosocomial pneumonia. Therefore, new therapeutic approaches against this bacterium are needed. Surface-exposed ...proteins from bacterial pathogens are implicated in a variety of virulence-related traits and are considered as promising candidates for vaccine development.
We show in this study that a large Blp1 protein from opportunistic pathogen A. baumannii is encoded in all examined clinical strains of globally spread international clonal lineages I (IC I) and II (IC II). The two blp1 gene variants exhibit lineage-specific distribution profile. By characterization of blp1 deletion mutants and their complementation with blp1 alleles we show that blp1 gene is required for A. baumannii biofilm formation and adhesion to epithelial cells in IC I strain but not in the IC II strain. Nevertheless both alleles are functional in restoring the deficient phenotypes of IC I strain. Moreover, the blp1 gene is required for the establishing of A. baumannii virulence phenotype in nematode and murine infection models. Additionally, we demonstrate that C-terminal 711 amino acid fragment of Blp1 elicits an efficient protection to lethal A. baumannii infection in a murine model using active and passive immunization approaches. Antiserum obtained against Blp1-specific antigen provides opsonophagocytic killing of A. baumannii in vitro.
Lineage-specific variants of surface-exposed components of bacterial pathogens complicate the development of new therapeutic approaches. Though we demonstrated different impact of Blp1 variants on adherence of IC I and IC II strains, Blp1-specific antiserum neutralized A. baumannii strains of both clonal lineages. Together with the observed increased survival rate in vaccinated mice these results indicate that A. baumannii Blp1 protein could be considered as a new vaccine candidate.
is a nosocomial human pathogen of increasing concern due to its multidrug resistance profile. The outer membrane protein A (OmpA) is an abundant bacterial cell surface component involved in
...pathogenesis. It has been shown that the C-terminal domain of OmpA is located in the periplasm and non-covalently associates with the peptidoglycan layer via two conserved amino acids, thereby anchoring OmpA to the cell wall. Here, we investigated the role of one of the respective residues, D268 in OmpA of
clinical strain Ab
, on its virulence characteristics by complementing the Δ
mutant with the plasmid-borne
allele. We show that while restoring the impaired biofilm formation of the Δ
strain, the Ab
mutant tended to form bacterial filaments, indicating the abnormalities in cell division. Moreover, the Ab
OmpA D268-mediated association to peptidoglycan was required for the manifestation of twitching motility, desiccation resistance, serum-induced killing, adhesion to epithelial cells and virulence in a nematode infection model, although it was dispensable for the uptake of β-lactam antibiotics by outer membrane vesicles. Overall, the results of this study demonstrate that the OmpA C-terminal domain-mediated association to peptidoglycan is critical for a number of virulent properties displayed by
outside and within the host.
is one of the major causes of hard to treat multidrug-resistant hospital infections.
features contributing to its spread and persistence in clinical environment are only beginning to be explored. ...Bacterial toxin-antitoxin (TA) systems are genetic loci shown to be involved in plasmid maintenance and proposed to function as components of stress response networks. Here we present a thorough characterization of type II system of
, which is the most ubiquitous TA module present in
plasmids.
of
is a reverse TA (the toxin gene is the first in the operon) and shows little homology to other TA systems of RelE superfamily. It is represented by two variants, which both are functional albeit exhibit strong difference in sequence conservation. The
operon is found on ubiquitous 11 Kb pAB120 plasmid, conferring carbapenem resistance to clinical
isolates and represents a
variant that can be found with multiple sequence variations. We show here that
is capable to confer maintenance of unstable plasmid in
species. HigB2 toxin functions as a ribonuclease and its activity is neutralized by HigA2 antitoxin through formation of an unusually large heterooligomeric complex. Based on the
expression analysis of
reporter gene we propose that HigA2 antitoxin and HigBA2 protein complex bind the
promoter region to downregulate its transcription. We also demonstrate that
is a stress responsive locus, whose transcription changes in conditions encountered by
in clinical environment and within the host. We show elevated expression of
during stationary phase, under iron deficiency and downregulated expression after antibiotic (rifampicin) treatment.
Non-canonical 5'-caps removing RNA hydrolase NudC, along with stress-responsive RNA helicase CsdA, is crucial for 5'-NAD-RNA decapping and bacterial movement.
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