Contribution of the a-baumannii A1S_0114 gene to the interaction with eukaryotic cells and virulence

Genetic and functional studies showed that some components of the Acinetobacter baumannii ATCC 17978 A1S_0112-A1S_0119 gene cluster are critical for biofilm biogenesis and surface motility. Recently, our group has shown that the A1S_0114 gene was involved in biofilm formation, a process related with pathogenesis. Confirming our previous results, microscopy images revealed that the ATCC 17978 10114 derivative lacking this gene was unable to form a mature biofilm structure. Therefore, other bacterial phenotypes were analyzed to determine the role of this gene in the pathogenicity of A. baumannii ATCC 17978. The interaction of the ATCC 17978 parental strain and the 10114 mutant with A549 human alveolar epithelial cells was quantified revealing that the A1S_0114 gene was necessary for proper attachment to A549 cells. This dependency correlates with the negative effect of the A1S_0114 deletion on the expression of genes coding for surface proteins and pili-assembly systems, which are known to play a role in adhesion. Three different experimental animal models, including vertebrate and invertebrate hosts, confirmed the role of the A1S_0114 gene in virulence. All of the experimental infection assays indicated that the virulence of the ATCC 17978 was significantly reduced when this gene was inactivated. Finally, we discovered that the A1S_0114 gene was involved in the production of a small lipopeptide-like compound herein referred to as acinetin 505 (Ac-505). Ac-505 was isolated from ATCC 17978 spent media and its chemical structure was interpreted by mass spectrometry. Overall, our observations provide novel information on the role of the A1S_0114 gene in A. baumannii’s pathobiology and lay the foundation for future work to determine the mechanisms by which Ac-505, or possibly an Ac-505 precursor, could execute critical functions as a secondary metaboliteS

Two Acinetobacter baumannii Isolates Obtained From a Fatal Necrotizing Fasciitis Infection Display Distinct Genomic and Phenotypic Characteristics in Comparison to Type Strains

Acinetobacter baumannii has been recognized as a critical pathogen that causes severe infections worldwide not only because of the emergence of extensively drug-resistant (XDR) derivatives, but also because of its ability to persist in medical environments and colonize compromised patients. While there are numerous reports describing the mechanisms by which this pathogen acquires resistance genes, little is known regarding A. baumannii's virulence functions associated with rare manifestations of infection such as necrotizing fasciitis, making the determination and implementation of alternative therapeutic targets problematic. To address this knowledge gap, this report describes the analysis of the NFAb-1 and NFAb-2 XDR isolates, which were obtained at two time points during a fatal case of necrotizing fasciitis, at the genomic and functional levels. The comparative genomic analysis of these isolates with the ATCC 19606T and ATCC 17978 strains showed that the NFAb-1 and NFAb-2 isolates are genetically different from each other as well as different from the ATCC 19606T and ATCC 17978 clinical isolates. These genomic differences could be reflected in phenotypic differences observed in these NFAb isolates. Biofilm, cell viability and flow cytometry assays indicate that all tested strains caused significant decreases in A549 human alveolar epithelial cell viability with ATCC 17978, NFAb-1 and NFAb-2 producing significantly less biofilm and significantly more hemolysis and capacity for intracellular invasion than ATCC 19606T. NFAb-1 and NFAb-2 also demonstrated negligible surface motility but significant twitching motility compared to ATCC 19606T and ATCC 17978, likely due to the presence of pili exceeding 2 µm in length, which are significantly longer and different from those previously described in the ATCC 19606T and ATCC 17978 strains. Interestingly, infection with cells of the NFAb-1 isolate, which were obtained from a premortem blood sample, lead to significantly higher mortality rates than NFAb-2 bacteria, which were obtained from postmortem tissue samples, when tested using the Galleria mellonella in vivo infection model. These observations suggest potential changes in the virulence phenotype of the A. baumannii necrotizing fasciitis isolates over the course of infection by mechanisms and cell processes that remain to be identified

Community-Acquired, Extended-Spectrum β-Lactamase-Producing and Extensively Drug-Resistant Escherichia coli in a 28-Year-Old Pyelonephritis Patient Lacking Risk Factors

While Escherichia coli is a common cause of urinary tract infections and pyelonephritis, there are few documented cases of extended-spectrum β-lactamase (ESBL)-producing and extensively drug-resistant (XDR) isolates from the community resulting in infection requiring hospitalization, especially in individuals lacking risk factors. In the United States, exposure to ESBL-producing E. coli is typically nosocomial, whereas patients from developing countries often encounter ESBL-producing E. coli in the community through the consumption of contaminated food or water. Considering the rarity at which XDR E. coli isolates are encountered, there is also a scarcity of literature describing the successful treatment of ESBL-producing XDR E. coli. Here we present a case of an otherwise healthy 28-year-old female delicatessen worker infected with ESBL-producing and XDR E. coli without recent travel, antibiotic use, or healthcare contact, who required admission to the intensive care unit (ICU) with pyelonephritis and septic shock. Treatment with intravenous meropenem through a peripherally inserted central catheter (PICC) line at home was curative and follow up thereafter unremarkable. Given the patient’s lack of obvious exposure to and risk factors for an ESBL-producing XDR E. coli infection and the specific lack of risk factors for severe pyelonephritis requiring hospitalization, this case represents a unique addition to the literature and is of value to clinicians by describing successful treatment

Draft genome of the multidrug-resistant Acinetobacter baumannii strain A155 clinical isolate

Acinetobacter baumannii is a bacterial pathogen with serious implications for human health, due to increasing reports of multidrug-resistant strains isolated from patients. Total DNA from the multidrug-resistant A. baumannii strain A155 clinical isolate was sequenced to greater than 65x coverage, providing high-quality contig assemblies.Fil: Arivett, Brock A.. Miami University; Estados UnidosFil: Fiester, Steven E.. Miami University; Estados UnidosFil: Ream, David C.. Miami University; Estados UnidosFil: Centron, Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Ramirez, Maria Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Investigaciones en Microbiología y Parasitología Médica. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Investigaciones en Microbiología y Parasitología Médica; ArgentinaFil: Tolmasky, Marcelo. Fullerton University; Estados UnidosFil: Actis, Luis A.. Miami University; Estados Unido

Antimicrobial Activity of Gallium Protoporphyrin IX against Acinetobacter baumannii Strains Displaying Different Antibiotic Resistance Phenotypes

A paucity of effective, currently available antibiotics and a lull in antibiotic development pose significant challenges for treatment of patients with multidrug-resistant (MDR) Acinetobacter baumannii infections. Thus, novel therapeutic strategies must be evaluated to meet the demands of treatment of these often life-threatening infections. Accordingly, we examined the antibiotic activity of gallium protoporphyrin IX (Ga-PPIX) against a collection of A. baumannii strains, including nonmilitary and military strains and strains representing different clonal lineages and isolates classified as susceptible or MDR. Susceptibility testing demonstrated that Ga-PPIX inhibits the growth of all tested strains when cultured in cation-adjusted Mueller-Hinton broth, with a MIC of 20 μg/ml. This concentration significantly reduced bacterial viability, while 40 μg/ml killed all cells of the A. baumannii ATCC 19606(T) and ACICU MDR isolate after 24-h incubation. Recovery of ATCC 19606(T) and ACICU strains from infected A549 human alveolar epithelial monolayers was also decreased when the medium was supplemented with Ga-PPIX, particularly at a 40-μg/ml concentration. Similarly, the coinjection of bacteria with Ga-PPIX increased the survival of Galleria mellonella larvae infected with ATCC 19606(T) or ACICU. Ga-PPIX was cytotoxic only when monolayers or larvae were exposed to concentrations 16-fold and 1,250-fold higher than those showing antibacterial activity, respectively. These results indicate that Ga-PPIX could be a viable therapeutic option for treatment of recalcitrant A. baumannii infections regardless of the resistance phenotype, clone lineage, time and site of isolation of strains causing these infections and their iron uptake phenotypes or the iron content of the media

Glyphosate and Polyoxyethyleneamine Ingestion Leading to Renal, Hepatic, and Pulmonary Failure

Glyphosate is an organophosphorus compound and the active ingredient in commonly used herbicides, whereas polyoxyethyleneamine (POEA) is a nonionic surfactant often coupled with glyphosate in these herbicides to increase their efficacy. Cases of glyphosate-POEA ingestion have shown a variety of outcomes, ranging from skin and mucosal surface irritation to death. Here, we report mortality after ingestion of at least 237 mL of an herbicide confirmed to contain both glyphosate and POEA. The decedent\u27s electronic medical record indicates presentation to the emergency department shortly after ingestion and rapid decompensation, with death occurring on the fourth day of admission. The autopsy report showed extensive pulmonary edema and congestion with no alimentary tract abnormalities. Microscopically, airway inflammation, edema, and hemorrhage were shown as well as pericentral necrosis and macrovascular hepatic steatosis. This case is unusual for several reasons including the fatal outcome in a young 30-year-old patient, the large volume of the herbicide consumed, the associated large volume aspirated, and the lung pathology associated with exposure to glyphosate-POEA since inhalation, and in this case, aspiration is an uncommon route of glyphosate-POEA exposure. This report therefore offers rare respiratory tract pathological findings and the clinical course after aspiration of a large volume of glyphosate-POEA

Differential transcription of genes coding for benzoate transport and metabolism functions in response to the presence of mucin.

<p>(A) A1S_1215-A1S_1206 genomic region coding for BenA/B/C/D/E/K/P orthologs. The arrows represent each coding region and its direction of transcription. The grey arrows represent genes up-regulated in response to the presence of mucin. The black arrow indicates the gene (<i>benP</i>, A1S_1209) that was used to confirm the mucin-mediated up-regulation effect by qRT-PCR. Numbers above the arrows represent cognate A1S_ gene annotation numbers, and gene names are indicated below each arrow. (B) qRT-PCR analysis of the differential expression of A1S_1209 in bacterial cells cultured in SB (white bar) or SB+M (grey bar) performed using nine replicates. Significantly different values (<i>P</i> ≤ 0.001) are identified by three asterisks and error bars represent the standard error of each data set.</p

Differential transcription of genes coding for T6SS components in response to the presence of mucin.

<p>(A) ATCC 19606^T genes coding for T6SS components. The arrows represent each coding region and its direction of transcription. The white and grey arrows represent genes constitutively and differentially expressed in response to the presence of mucin, respectively. The black arrow indicates <i>tssH</i> (A1S_1307), which was used to confirm the mucin-mediated up-regulation effect by qRT-PCR. Numbers above the arrows represent cognate A1S_ gene annotation numbers, and gene names are indicated below each arrow. Coding regions A1S_1288/1289, A1S_1293/1294, A1S_1298/1299, and A1S_1302/1303 are each represented as a single coding region since potential nucleotide sequencing errors could have resulted in the annotation of multiple open reading frames. <i>hyp</i>, gene coding for a hypothetical protein. (B) qRT-PCR analysis of the differential expression of A1S_1309 in bacterial cells cultured in SB (white bar) or SB+M (grey bar) was performed using nine replicates. Significantly different values (<i>P</i> ≤ 0.001) are identified by three asterisks and error bars represent the standard error of each data set. (C) Bacterial killing assay using <i>E</i>. <i>coli</i> MG1655-Rif (MR) as a prey and ATCC 19606^T cultured in SB (AbSB) or SB+M (AbSB+M) as a predator. Representative image of experiments performed two times using three different biological samples for each experiment (<i>n</i> = 6) showing differences in the amount of bacterial colonies formed on the surface of the agar plate among the tested samples.</p

<i>A</i>. <i>baumannii</i> ATCC 19606^T metabolic genes with increased expression in the presence of mucin.

<p><i>A</i>. <i>baumannii</i> ATCC 19606^T metabolic genes with increased expression in the presence of mucin.</p

<i>A</i>. <i>baumannii</i> ATCC 19606^T virulence-associated genes with increased expression in the presence of mucin.

<p><i>A</i>. <i>baumannii</i> ATCC 19606^T virulence-associated genes with increased expression in the presence of mucin.</p