Multidrug-resistant Acinetobacter baumannii infections: Current evidence on treatment options and the role of pharmacokinetics/pharmacodynamics in dose optimisation

ABSTRACT Acinetobacter baumannii is an important Gram-negative pathogen in hospital-related infections. However, treatment options for A. baumannii infections have become limited due to multidrug resistance. Bacterial virulence is often associated with capsule genes found in the K locus, many of which are essential for biosynthesis of the bacterial envelope. However, the roles of other genes in the K locus remain largely unknown. From an in vitro evolution experiment, we obtained an isolate of the virulent and multidrug-resistant A. baumannii strain MDR-ZJ06, called MDR-ZJ06M, which has an insertion by the ISAba16 transposon in gnaA (encoding UDP-N-acetylglucosamine C-6 dehydrogenase), a gene found in the K locus. The isolate showed an increased resistance toward tigecycline, whereas the MIC decreased in the case of carbapenems, cephalosporins, colistin, and minocycline. By using knockout and complementation experiments, we demonstrated that gnaA is important for the synthesis of lipooligosaccharide and capsular polysaccharide and that disruption of the gene affects the morphology, drug susceptibility, and virulence of the pathogen.

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Radiation-Inactivated Acinetobacter baumannii Vaccine Candidates

Vaccines ◽

10.3390/vaccines9020096 ◽

2021 ◽

Vol 9 (2) ◽

pp. 96

Author(s):

Stephen J. Dollery ◽

Daniel V. Zurawski ◽

Elena K. Gaidamakova ◽

Vera Y. Matrosova ◽

John K. Tobin ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Treatment Options ◽

Bacterial Pathogen ◽

Multidrug Resistant ◽

Bacterial Cells ◽

Wound Infections ◽

Protein Profiles ◽

Vaccine Candidates ◽

Rich Media ◽

Life Threatening

Acinetobacter baumannii is a bacterial pathogen that is often multidrug-resistant (MDR) and causes a range of life-threatening illnesses, including pneumonia, septicemia, and wound infections. Some antibiotic treatments can reduce mortality if dosed early enough before an infection progresses, but there are few other treatment options when it comes to MDR-infection. Although several prophylactic strategies have been assessed, no vaccine candidates have advanced to clinical trials or have been approved. Herein, we rapidly produced protective whole-cell immunogens from planktonic and biofilm-like cultures of A. baumannii, strain AB5075 grown using a variety of methods. After selecting a panel of five cultures based on distinct protein profiles, replicative activity was extinguished by exposure to 10 kGy gamma radiation in the presence of a Deinococcus antioxidant complex composed of manganous (Mn2+) ions, a decapeptide, and orthophosphate. Mn2+ antioxidants prevent hydroxylation and carbonylation of irradiated proteins, but do not protect nucleic acids, yielding replication-deficient immunogenic A. baumannii vaccine candidates. Mice were immunized and boosted twice with 1.0 × 107 irradiated bacterial cells and then challenged intranasally with AB5075 using two mouse models. Planktonic cultures grown for 16 h in rich media and biofilm cultures grown in static cultures underneath minimal (M9) media stimulated immunity that led to 80–100% protection.

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Colistin heteroresistance and the involvement of the PmrAB regulatory system in Acinetobacter baumannii

10.1101/307132 ◽

2018 ◽

Author(s):

Yannick Charretier ◽

Seydina M. Diene ◽

Damien Baud ◽

Sonia Chatellier ◽

Emmanuelle Santiago-Allexant ◽

...

Keyword(s):

Acinetobacter Baumannii ◽

Population Analysis ◽

Regulatory System ◽

Clinical Problem ◽

Multidrug Resistant ◽

Regulatory Pathway ◽

Colistin Resistance ◽

Bacterial Killing ◽

One Step

AbstractMultidrug-resistant Acinetobacter baumannii infection has recently emerged as a worldwide clinical problem and colistin is increasingly being used as last resort therapy. Despite its favorable bacterial killing, resistance and heteroresistance to colistin have been described. Mutations in the PmrAB regulatory pathway have been already associated with colistin resistance whereas the mechanisms for heteroresistance remain largely unknown. The purpose of the present study is to investigate the role of PmrAB in laboratory-selected mutants representative of global epidemic strains. During brief colistin exposure, colistin resistant and colistin heteroresistant mutants were selected in a one-step strategy. Population Analysis Profiling (PAP) was performed to confirm the suspected phenotype. Upon withdrawal of selective pressure, compensatory mutations were evaluated in another one-step strategy. A trans-complementation assay was designed to delineate the involvement of the PmrAB regulatory system using qPCR and PAP. Mutations in the PmrAB regulatory pathway were associated with colistin resistance and colistin heteroresistance as well. The transcomplementation assay provides a proof for the role played by changes in the PmrAB regulatory pathway. The level of colistin resistance is correlated to the level of expression of pmrC. The resistance phenotype was partially restored since the complemented strain became heteroresistant. This report shows the role of different mutations in the PmrAB regulatory pathway and warns on the development of colistin heteroresistance that could be present but not easily detected with routine testing.

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Shifting Gears: The Future of Polymyxin Antibiotics

Antibiotics ◽

10.3390/antibiotics8020042 ◽

2019 ◽

Vol 8 (2) ◽

pp. 42 ◽

Cited By ~ 8

Author(s):

Lenhard ◽

Bulman ◽

Tsuji ◽

Kaye

Keyword(s):

Treatment Options ◽

Multidrug Resistant ◽

Drug Resistant ◽

Carbapenem Resistant ◽

The Future ◽

Important Addition ◽

Future Strategy ◽

Future Utility ◽

A Current

The manuscripts contained in this special edition of Antibiotics represent a current review of the polymyxins as well as highlights from the 3rd International Polymyxin Conference, which was held in Madrid, Spain, April 25 to 26, 2018. The role of the polymyxin antibiotics has evolved over time based on the availability of alternative agents. After high rates of nephrotoxicity caused the drug class to fall out of favor, polymyxins were once against utilized in the 21st century to combat drug-resistant pathogens. However, the introduction of safer agents with activity against drug-resistant organisms has brought the future utility of polymyxins into question. The present review investigates the future niche of polymyxins by evaluating currently available and future treatment options for difficult-to-treat pathogens. The introduction of ceftazidime-avibactam, meropenem-vaborbactam and plazomicin are likely to decrease polymyxin utilization for infections caused by Enterobacteriaceae. Similarly, the availability of ceftolozane-tazobactam will reduce the use of polymyxins to counter multidrug-resistant Pseudomonas aeruginosa. In contrast, polymyxins will likely continue be an important option for combatting carbapenem-resistant Acinetobacter baumannii until better options become commercially available. Measuring polymyxin concentrations in patients and individualizing therapy may be a future strategy to optimize clinical outcomes while minimizing nephrotoxicity. Inhaled polymyxins will continue to be an adjunctive option for pulmonary infections but further clinical trials are needed to clarify the efficacy of inhaled polymyxins. Lastly, safer polymyxin analogs will potentially be an important addition to the antimicrobial armamentarium.

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Characterization of RelA in Acinetobacter baumannii

Journal of Bacteriology ◽

10.1128/jb.00045-20 ◽

2020 ◽

Vol 202 (12) ◽

Cited By ~ 3

Author(s):

María Pérez-Varela ◽

Aimee R. P. Tierney ◽

Ju-Sim Kim ◽

Andrés Vázquez-Torres ◽

Philip Rather

Keyword(s):

Acinetobacter Baumannii ◽

Galleria Mellonella ◽

Multidrug Resistant ◽

Cell Physiology ◽

Content Type ◽

Content Model ◽

Transposon Insertion ◽

Downstream Effectors

ABSTRACT In response to nutrient depletion, the RelA and SpoT proteins generate the signaling molecule (p)ppGpp, which then controls a number of downstream effectors to modulate cell physiology. In Acinetobacter baumannii strain AB5075, a relA ortholog (ABUW_3302) was identified by a transposon insertion that conferred an unusual colony phenotype. An in-frame deletion in relA (ΔrelA) failed to produce detectable levels of ppGpp when amino acid starvation was induced with serine hydroxamate. The ΔrelA mutant was blocked from switching from the virulent opaque colony variant (VIR-O) to the avirulent translucent colony variant (AV-T), but the rate of AV-T to VIR-O switching was unchanged. In addition, the ΔrelA mutation resulted in a pronounced hypermotile phenotype on 0.35% agar plates. This hypermotility was dependent on the activation of a LysR regulator ABUW_1132, which was required for expression of AbaR, a LuxR family quorum-sensing regulator. In the ΔrelA mutant, ABUW_1132 was also required for the increased expression of an operon composed of the ABUW_3766-ABUW_3773 genes required for production of the surfactant-like lipopeptide acinetin 505. Additional phenotypes identified in the ΔrelA mutant included (i) cell elongation at high density, (ii) reduced formation of persister cells tolerant to colistin and rifampin, and (iii) decreased virulence in a Galleria mellonella model. IMPORTANCE Acinetobacter baumannii is a pathogen of worldwide importance. Due to the increasing prevalence of antibiotic resistance, these infections are becoming increasingly difficult to treat. New therapies are required to combat multidrug-resistant isolates. The role of RelA in A. baumannii is largely unknown. This study demonstrates that like in other bacteria, RelA controls a variety of functions, including virulence. Strategies to inhibit the activity of RelA and the resulting production of ppGpp could inhibit virulence and may represent a new therapeutic approach.

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Possible role of integrase gene polymerase chain reaction as an epidemiological marker: study of multidrug-resistant Acinetobacter baumannii isolated from nosocomial infections

International Journal of Antimicrobial Agents ◽

10.1016/j.ijantimicag.2006.11.014 ◽

2007 ◽

Vol 29 (4) ◽

pp. 446-450 ◽

Cited By ~ 11

Author(s):

Abhishek Gaur ◽

Pradyot Prakash ◽

Shampa Anupurba ◽

Tribhuban M. Mohapatra

Keyword(s):

Polymerase Chain Reaction ◽

Acinetobacter Baumannii ◽

Nosocomial Infections ◽

Multidrug Resistant ◽

Chain Reaction ◽

Integrase Gene ◽

Gene Polymerase Chain Reaction ◽

Marker Study ◽

Polymerase Chain

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Carbapenemase Genes and Multidrug Resistance of Acinetobacter Baumannii: A Cross Sectional Study of Patients with Pneumonia in Southern Vietnam

Antibiotics ◽

10.3390/antibiotics8030148 ◽

2019 ◽

Vol 8 (3) ◽

pp. 148 ◽

Cited By ~ 5

Author(s):

Cuong Hoang Quoc ◽

Thao Nguyen Thi Phuong ◽

Hai Nguyen Duc ◽

Trung Tran Le ◽

Hang Tran Thi Thu ◽

...

Keyword(s):

Antibiotic Resistance ◽

Acinetobacter Baumannii ◽

Demographic Data ◽

Treatment Options ◽

Bacterial Pathogen ◽

Multidrug Resistant ◽

Cross Sectional Study ◽

Cross Sectional ◽

Carbapenem Resistant ◽

Hospital Acquired

Background: Acinetobacter baumannii (Ab) is an opportunistic bacterial pathogen found in hospital-acquired infections including nosocomial pneumonia, especially multidrug-resistant Ab. This study aims to survey the drug resistance profiles of Ab isolated from patients in Thong Nhat Dong Nai General Hospital and assess the relationship between genotypes and antibiotic resistance; Methods: Ninety-seven Ab strains isolated from 340 lower respiratory tract specimens among pneumonia patients were used to screen the most common local carbapenemase genes. Antimicrobial susceptibility testing results and demographic data were collected and minimum inhibitory concentrations (MIC) of colistin were also determined; Results: Over 80% and 90% of Ab strains were determined as carbapenem-resistant and multidrug-resistant (MDR), respectively. Most of the strains carried carbapenemase genes, including blaOXA-51, blaOXA-23-like, blaOXA-58-like, and blaNDM-1, with proportions of 97 (100%), 76 (78.4%), 10 (10.3%), 6 (6.2%), respectively. Amongst these genes, blaOXA-23-like was the only gene which significantly influenced the resistance (p < 0.0001); and Conclusions: The severity of Ab antibiotic resistance is urgent and specifically related to carbapenemase encoding genes. Therefore, screening of MDR Ab and carbapenemase for better treatment options is necessary.

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Noninferior Antibiotics: When Is “Not Bad” “Good Enough”?

Open Forum Infectious Diseases ◽

10.1093/ofid/ofw110 ◽

2016 ◽

Vol 3 (3) ◽

Cited By ~ 5

Author(s):

Mark J. DiNubile

Keyword(s):

Nursing Home ◽

Clinical Practice ◽

Antimicrobial Agents ◽

Treatment Options ◽

Chronically Ill ◽

Multidrug Resistant ◽

Everyday Clinical Practice ◽

Novel Treatment ◽

Efficacious Treatment

Abstract Novel treatment options are urgently needed for patients with serious multidrug-resistant infections seen increasingly in routine everyday clinical practice, both in the hospital and nursing home as well as in the clinic and office setting. Unfortunately, the problem is no longer confined to chronically ill, repeatedly hospitalized patients. This essay explores the role of noninferiorly studies in addressing the pressing need for new antimicrobial agents to combat the emerging “superbugs”, calling attention to the nuances of interpreting their sometimes less-than-straightforward results. The overriding aim is not to find better antibiotics for routinely treatable infections but to identify safe and efficacious treatment options where none presently exist.

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Role of the Myokine Irisin on Bone Homeostasis: Review of the Current Evidence

International Journal of Molecular Sciences ◽

10.3390/ijms22179136 ◽

2021 ◽

Vol 22 (17) ◽

pp. 9136

Author(s):

Amanda Kornel ◽

Danja J. Den Hartogh ◽

Panagiota Klentrou ◽

Evangelia Tsiani

Keyword(s):

Bone Resorption ◽

Treatment Options ◽

Treatment Strategies ◽

Current Treatment ◽

Current Evidence ◽

Signaling Proteins ◽

Bone Homeostasis ◽

Menopausal Women ◽

Post Menopausal

Bone is a highly dynamic tissue that is constantly adapting to micro-changes to facilitate movement. When the balance between bone building and resorption shifts more towards bone resorption, the result is reduced bone density and mineralization, as seen in osteoporosis or osteopenia. Current treatment strategies aimed to improve bone homeostasis and turnover are lacking in efficacy, resulting in the search for new preventative and nutraceutical treatment options. The myokine irisin, since its discovery in 2012, has been shown to play an important role in many tissues including muscle, adipose, and bone. Evidence indicate that irisin is associated with increased bone formation and decreased bone resorption, leading to reduced risk of osteoporosis in post-menopausal women. In addition, low serum irisin levels have been found in individuals with osteoporosis and osteopenia. Irisin targets key signaling proteins, promoting osteoblastogenesis and reducing osteoclastogenesis. The present review summarizes the existing evidence regarding the effects of irisin on bone homeostasis.

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