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Clinical Microbiology Reviews Jan 2017Acinetobacter is a complex genus, and historically, there has been confusion about the existence of multiple species. The species commonly cause nosocomial infections,... (Review)
Review
Acinetobacter is a complex genus, and historically, there has been confusion about the existence of multiple species. The species commonly cause nosocomial infections, predominantly aspiration pneumonia and catheter-associated bacteremia, but can also cause soft tissue and urinary tract infections. Community-acquired infections by Acinetobacter spp. are increasingly reported. Transmission of Acinetobacter and subsequent disease is facilitated by the organism's environmental tenacity, resistance to desiccation, and evasion of host immunity. The virulence properties demonstrated by Acinetobacter spp. primarily stem from evasion of rapid clearance by the innate immune system, effectively enabling high bacterial density that triggers lipopolysaccharide (LPS)-Toll-like receptor 4 (TLR4)-mediated sepsis. Capsular polysaccharide is a critical virulence factor that enables immune evasion, while LPS triggers septic shock. However, the primary driver of clinical outcome is antibiotic resistance. Administration of initially effective therapy is key to improving survival, reducing 30-day mortality threefold. Regrettably, due to the high frequency of this organism having an extreme drug resistance (XDR) phenotype, early initiation of effective therapy is a major clinical challenge. Given its high rate of antibiotic resistance and abysmal outcomes (up to 70% mortality rate from infections caused by XDR strains in some case series), new preventative and therapeutic options for Acinetobacter spp. are desperately needed.
Topics: Acinetobacter; Acinetobacter Infections; Anti-Bacterial Agents; Clinical Trials as Topic; Community-Acquired Infections; Cross Infection; Drug Resistance, Multiple, Bacterial; Humans; Time-to-Treatment; Virulence Factors
PubMed: 27974412
DOI: 10.1128/CMR.00058-16 -
Frontiers in Physiology 2022The gastrointestinal tract has been speculated to serve as a reservoir for , however little is known about the ecological fitness of strains in the gut. Likewise, not...
The gastrointestinal tract has been speculated to serve as a reservoir for , however little is known about the ecological fitness of strains in the gut. Likewise, not much is known about the ability of to consume dietary, or host derived nutrients or their capacity to modulate host gene expression. Given the increasing prevalence of in the clinical setting, we sought to characterize how responds to gut-related stressors and identify potential microbe-host interactions. To accomplish these aims, we grew clinical isolates and commercially available strains of in minimal media with different levels of pH, osmolarity, ethanol and hydrogen peroxide. Utilization of nutrients was examined using Biolog phenotypic microarrays. To examine the interactions of with the host, inverted murine organoids where the apical membrane is exposed to bacteria, were incubated with live and gene expression was examined by qPCR. All strains grew modestly at pH 6, 5 and 4; indicating that these strains could tolerate passage through the gastrointestinal tract. All strains had robust growth in 0.1 and 0.5 M NaCl concentrations which mirror the small intestine, but differences were observed between strains in response to 1 M NaCl. Additionally, all strains tolerated up to 5% ethanol and 0.1% hydrogen peroxide. Biolog phenotypic microarrays revealed that strains could use a range of nutrient sources, including monosaccharides, disaccharides, polymers, glycosides, acids, and amino acids. Interestingly, the commercially available strains and one clinical isolate stimulated the pro-inflammatory cytokines , , and while all strains suppressed and . Collectively, these data demonstrate that is well adapted to dealing with environmental stressors of the gastrointestinal system. This data also points to the potential for to influence the gut epithelium.
PubMed: 35685287
DOI: 10.3389/fphys.2022.880024 -
Antibiotics (Basel, Switzerland) Jul 2022Background: Acinetobacter spp. have emerged as troublesome pathogens due to their multi-drug resistance. The majority of the work to date has focused on the antibiotic...
Background: Acinetobacter spp. have emerged as troublesome pathogens due to their multi-drug resistance. The majority of the work to date has focused on the antibiotic resistance profile of Acinetobacter baumannii. Although A. calcoaceticus strains are isolated in the hospital setting, limited information is available on these closely related species. Methods & Results: The computational analysis of antibiotic resistance genes in 1441 Acinetobacter genomes revealed that A. calcoaceticus harbored a similar repertoire of multi-drug efflux pump and beta-lactam resistance genes as A. baumannii, leading us to speculate that A. calcoaceticus would have a similar antibiotic resistance profile to A. baumannii. To profile the resistance patterns of A. calcoaceticus, strains were examined by Kirby−Bauer disk diffusion and phenotypic microarrays. We found that Acinetobacter strains were moderately to highly resistant to certain antibiotics within fluoroquinolones, aminoglycosides, tetracyclines, and other antibiotic classes. These data indicate that A. calcoaceticus has a similar antibiotic resistance profile as A. baumannii ATCC 19606. We also identified that all Acinetobacter species were sensitive to 5-fluoroorotic acid, novobiocin, and benzethonium chloride. Conclusion: Collectively, these data provide new insights into the antibiotic resistance in A. calcoaceticus and identify several antibiotics that could be beneficial in treating Acinetobacter infections.
PubMed: 35884232
DOI: 10.3390/antibiotics11070978 -
Clinical Infectious Diseases : An... May 2023Acinetobacter baumannii-calcoaceticus complex is the most commonly identified species in the genus Acinetobacter and it accounts for a large percentage of nosocomial...
Acinetobacter baumannii-calcoaceticus complex is the most commonly identified species in the genus Acinetobacter and it accounts for a large percentage of nosocomial infections, including bacteremia, pneumonia, and infections of the skin and urinary tract. A few key clones of A. baumannii-calcoaceticus are currently responsible for the dissemination of these organisms worldwide. Unfortunately, multidrug resistance is a common trait among these clones due to their unrivalled adaptive nature. A. baumannii-calcoaceticus isolates can accumulate resistance traits by a plethora of mechanisms, including horizontal gene transfer, natural transformation, acquisition of mutations, and mobilization of genetic elements that modulate expression of intrinsic and acquired genes.
Topics: Humans; Acinetobacter baumannii; Anti-Bacterial Agents; Acinetobacter calcoaceticus; Acinetobacter Infections; Acinetobacter; Bacteremia; Drug Resistance, Multiple, Bacterial
PubMed: 37125466
DOI: 10.1093/cid/ciad109 -
Asian Biomedicine : Research, Reviews... Oct 2020species, particularly those within complex (ACB complex), have emerged as clinically relevant pathogens in hospital environments worldwide. Early and quick detection... (Review)
Review
species, particularly those within complex (ACB complex), have emerged as clinically relevant pathogens in hospital environments worldwide. Early and quick detection and identification of infections is challenging, and traditional culture and biochemical methods may not achieve adequate levels of speciation. Moreover, currently available techniques to identify and differentiate closely related species are insufficient. The objective of this review is to recapitulate the current evolution in phenotypic and automated techniques used to identify the ACB complex. Compared with other automated or semiautomated systems of bacterial identification, matrix-assisted laser desorption-ionization time-of-flight mass spectrometry (MALDI-TOF MS) demonstrates a high level of species identification and discrimination, including newly discovered species and .
PubMed: 37551265
DOI: 10.1515/abm-2020-0026 -
New Biotechnology Mar 2022Rhamnolipids are predominantly produced from the opportunistic pathogen Pseudomonas aeruginosa, which restricts their scaled-up production and biomedical applications....
Rhamnolipids are predominantly produced from the opportunistic pathogen Pseudomonas aeruginosa, which restricts their scaled-up production and biomedical applications. Moreover, the wound healing property of rhamnolipids is mainly focused on either mono- or di-rhamnolipid congeners, which are obtained after extensive and costly purification procedures. Here, crude rhamnolipids from non-pathogenic Acinetobacter calcoaceticus BU-03 have been prepared and characterized and their wound healing potency evaluated in vitro and in vivo. Rhamnolipid extract was produced in a bioreactor by batch fermentation at a concentration of 12.7 ± 1.4 g/L. Characterization of the extract by Fourier Transform Infrared spectroscopy and mass spectrometry revealed characteristic rhamnolipid peaks. Rha-C10-C10 and Rha-Rha-C10-C10 appeared as the predominant congeners along with minor quantities of six more congeners. The rhamnolipid extract obtained from A. calcoaceticus had no toxicity against mouse fibroblast L929 cells and accelerated their migration. Transforming growth factor beta 1 (TGF-β1) has been shown to promote fibroblast migration by activating Smad3. It was found that the rhamnolipid extract enhanced Smad3 phosphorylation in L929 cells. In vivo studies showed that it promoted wound healing in mice with excisional wounds. The protein levels of TGF-β1 and alpha smooth muscle actin (α-SMA), a highly contractile protein, were significantly increased by 2.56- and 1.51-fold, respectively, in extract-treated compared with vehicle control-treated wounds, indicating that the activation of TGF-β1 signaling is possibly involved in the wound healing effect. These results suggest that a rhamnolipid extract obtained from A. calcoaceticus has potential as a wound healing material for topical application in cutaneous wound treatment.
Topics: Acinetobacter calcoaceticus; Animals; Bioreactors; Glycolipids; Mice; Pseudomonas aeruginosa; Wound Healing
PubMed: 34890838
DOI: 10.1016/j.nbt.2021.12.001 -
Future Science OA Jun 2019species have emerged as one of the most clinically important pathogens. The phenotypic techniques which are currently available are insufficient in accurately... (Review)
Review
species have emerged as one of the most clinically important pathogens. The phenotypic techniques which are currently available are insufficient in accurately identifying and differentiating the closely related and clinically important species. Here, we discuss the advantages and limitations of the conventional phenotypic methods, automated identification systems, molecular methods and MALDI-TOF in the precise identification and differentiation of species. More specifically, several species of this genus are increasingly reported to be of high clinical importance. Molecular characterization such as of -like PCR together with sequencing has high discriminatory power over the conventional methods for species identification, especially within the complex.
PubMed: 31285840
DOI: 10.2144/fsoa-2018-0127 -
Journal of Microbiology, Immunology,... Dec 2020To investigate clinical and microbiological response, and 30-day mortality of pneumonia involving multidrug-resistant (MDR) Acinetobacter calcoaceticus-Acinetobacter...
OBJECTIVES
To investigate clinical and microbiological response, and 30-day mortality of pneumonia involving multidrug-resistant (MDR) Acinetobacter calcoaceticus-Acinetobacter baumannii (Acb) complex treated with colistin, and identify associated factors of these outcomes.
METHODS
A retrospective study of 183 adult patients with colistin treatment for at least 7 days between January 2014 and October 2017.
RESULTS
The mean age was 76.8 years, and mean Acute Physiology and Chronic Health Evaluation II score was 17.7. Eighteen (9.8%) and 128 (69.9%) patients had intravenous (IV) colistin alone and inhaled (IH) colistin alone, respectively. Thirty-seven patients had both IV and IH colistin, including 5 (2.7%) with concurrent, and 32 (17.5%) with non-concurrent use of IV and IH colistin. The 30-day mortality rate was 19.1% and 131 (71.6%) patients had clinical response. In the 175 patients with available data, 126 (72%) had microbiological eradication. The multivariate analyses revealed that IH colistin alone was an independent predictor for 30-day survival, clinical response, and microbiological eradication, and IV colistin alone was an independent predictor for clinical failure. Patients with IV colistin alone had a significantly higher nephrotoxicity rate than IH colistin alone (37.5% vs 6.1%, P = 0.001). Sub-group analysis of 52 patients with IV colistin for ≧ 4 days revealed that 14 (26.9%) patients had inappropriate dose, and inappropriate dose was an independent predictor for 30-day mortality.
CONCLUSIONS
IH colistin provided good outcomes with few side effects, and appropriate dosing of IV colistin was important to avoid excess mortality.
Topics: Acinetobacter Infections; Acinetobacter baumannii; Acinetobacter calcoaceticus; Administration, Inhalation; Administration, Intravenous; Aged; Anti-Bacterial Agents; Colistin; Drug Resistance, Multiple, Bacterial; Female; Humans; Male; Microbial Sensitivity Tests; Pneumonia; Treatment Outcome
PubMed: 31607573
DOI: 10.1016/j.jmii.2019.08.007 -
Journal of Microbiology, Immunology,... Feb 2017Patients with Acinetobacter pittii and Acinetobacter nosocomialis bacteremia have lower mortality rates than those with Acinetobacter baumannii bacteremia. However, it... (Comparative Study)
Comparative Study
BACKGROUND/PURPOSE
Patients with Acinetobacter pittii and Acinetobacter nosocomialis bacteremia have lower mortality rates than those with Acinetobacter baumannii bacteremia. However, it is unknown whether these organisms differ in outcomes of bacteremic patients. We conducted this study to answer this question.
METHODS
In this retrospective study conducted at a teaching hospital in Taiwan, we enrolled all 86 patients who had developed A. pittii bacteremia and those with A. nosocomialis bacteremia from 2000 to 2008 while matching for age, sex, Acute Physiology and Chronic Health Evaluation II score, and appropriate antimicrobial therapy. After adjustment, we accessed the clinical characteristics and 14- and 28-day mortalities.
RESULTS
We found that the patients with A. pittii bacteremia had multiple comorbidities less often and received invasive procedures less frequently. The 14-day mortality rate of patients with A. pittii or A. nosocomialis bacteremia was 14% and 7%, respectively, whereas their 28-day mortality rate was 17% and 9%, respectively. Using the mortality rate in patients with A. nosocomialis bacteremia as a reference, the odds ratios for the 14- and 28-day crude morality in those with A. pittii were 2.16 [95% confidence interval (CI), 0.77-6.05] and 2.06 (95% CI, 0.82-5.15), respectively, whereas the adjusted odds ratios for 14- and 28-day mortality were 1.89 (95% CI, 0.56-6.14) and 1.67 (95% CI, 0.59-4.78) respectively.
CONCLUSION
Our 8-year study showed that the mortality rate of A. pittii bacteremia was higher but the difference was not statistically significant.
Topics: Acinetobacter; Acinetobacter Infections; Bacteremia; Female; Hospitals, Teaching; Humans; Male; Middle Aged; Retrospective Studies; Survival Analysis; Taiwan
PubMed: 25735795
DOI: 10.1016/j.jmii.2015.01.003