scholarly journals Septal Class A Penicillin-Binding Protein Activity and LD-Transpeptidases Mediate Selection of Colistin-Resistant Lipooligosaccharide-Deficient Acinetobacter baumannii

mBio ◽  
2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Katie N. Kang ◽  
Misha I. Kazi ◽  
Jacob Biboy ◽  
Joe Gray ◽  
Hannah Bovermann ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Binding Protein ◽  
Clinical Isolates ◽  
Compensatory Mutation ◽  
Penicillin Binding Protein ◽  
Gram Negative ◽  
Content Type ◽  
Class A ◽  
The Impact ◽  
Selection Of

ABSTRACT Despite dogma suggesting that lipopolysaccharide/lipooligosaccharide (LOS) was essential for viability of Gram-negative bacteria, several Acinetobacter baumannii clinical isolates produced LOS− colonies after colistin selection. Inactivation of the conserved class A penicillin-binding protein, PBP1A, was a compensatory mutation that supported isolation of LOS− A. baumannii, but the impact of PBP1A mutation was not characterized. Here, we show that the absence of PBP1A causes septation defects and that these, together with ld-transpeptidase activity, support isolation of LOS− A. baumannii. PBP1A contributes to proper cell division in A. baumannii, and its absence induced cell chaining. Only isolates producing three or more septa supported selection of colistin-resistant LOS− A. baumannii. PBP1A was enriched at the midcell, where the divisome complex facilitates daughter cell formation, and its localization was dependent on glycosyltransferase activity. Transposon mutagenesis showed that genes encoding two putative ld-transpeptidases (LdtJ and LdtK) became essential in the PBP1A mutant. Both LdtJ and LdtK were required for selection of LOS− A. baumannii, but each had distinct enzymatic activities in the cell. Together, these findings demonstrate that defects in PBP1A glycosyltransferase activity and ld-transpeptidase activity remodel the cell envelope to support selection of colistin-resistant LOS− A. baumannii. IMPORTANCE The increasing prevalence of antibiotic treatment failure associated with Gram-negative bacterial infections highlights an urgent need to develop new alternative therapeutic strategies. The last-line antimicrobial colistin (polymyxin E) targets the ubiquitous outer membrane lipopolysaccharide (LPS)/LOS membrane anchor, lipid A, which is essential for viability of most diderms. However, several LOS− Acinetobacter baumannii clinical isolates were recovered after colistin selection, suggesting a conserved resistance mechanism. Here, we characterized a role for penicillin-binding protein 1A in A. baumannii septation and intrinsic β-lactam susceptibility. We also showed that defects in PBP1A glycosyltransferase activity and ld-transpeptidase activity support isolation of colistin-resistant LOS− A. baumannii.

scholarly journals Cefiderocol Resistance in Acinetobacter baumannii: Roles of β-Lactamases, Siderophore Receptors, and Penicillin Binding Protein 3

2020 ◽  
Vol 64 (11) ◽  
Author(s):  
Saquib Malik ◽  
Monica Kaminski ◽  
David Landman ◽  
John Quale
Keyword(s):  
Acinetobacter Baumannii ◽  
Binding Protein ◽  
Receptor Gene ◽  
Multidrug Resistant ◽  
Resistance Mechanisms ◽  
Penicillin Binding Protein ◽  
Gram Negative ◽  
Content Type ◽  
Siderophore Receptors

ABSTRACT Cefiderocol is a siderophore cephalosporin active against many multidrug-resistant (MDR) Gram-negative pathogens. We examined the resistance mechanisms in 12 Acinetobacter baumannii strains with cefiderocol MICs ranging from ≤0.03 to >32 μg/ml. Cefiderocol resistance could not be explained by β-lactamase activity. Cefiderocol resistance was associated with reduced expression of the siderophore receptor gene pirA. Mutations involving PBP3 may have contributed to resistance in one strain. Additional studies are needed to assess the role of other siderophore receptors.

scholarly journals Frequency and Mechanism of Spontaneous Resistance to Sulbactam Combined with the Novel β-Lactamase Inhibitor ETX2514 in Clinical Isolates of Acinetobacter baumannii

2017 ◽  
Vol 62 (2) ◽  
Author(s):  
Sarah M. McLeod ◽  
Adam B. Shapiro ◽  
Samir H. Moussa ◽  
Michele Johnstone ◽  
Robert E. McLaughlin ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Broad Spectrum ◽  
Active Site ◽  
Stringent Response ◽  
Clinical Isolates ◽  
The Novel ◽  
Penicillin Binding Protein ◽  
Content Type ◽  
Sensitive Isolate ◽  
Lactamase Inhibitor

ABSTRACTThe novel diazabicyclooctenone ETX2514 is a potent, broad-spectrum serine β-lactamase inhibitor that restores sulbactam activity against resistantAcinetobacter baumannii. The frequency of spontaneous resistance to sulbactam-ETX2514 in clinical isolates was found to be 7.6 × 10−10to <9.0 × 10−10at 4× MIC and mapped to residues near the active site of penicillin binding protein 3 (PBP3). Purified mutant PBP3 proteins demonstrated reduced affinity for sulbactam. In a sulbactam-sensitive isolate, resistance also mapped to stringent response genes associated with resistance to PBP2 inhibitors, suggesting that in addition to β-lactamase inhibition, ETX2514 may enhance sulbactam activity inA. baumanniivia inhibition of PBP2.

scholarly journals A penicillin-binding protein inhibits selection of colistin-resistant, lipooligosaccharide-deficientAcinetobacter baumannii

2016 ◽  
Vol 113 (41) ◽  
pp. E6228-E6237 ◽  
Author(s):  
Joseph M. Boll ◽  
Alexander A. Crofts ◽  
Katharina Peters ◽  
Vincent Cattoir ◽  
Waldemar Vollmer ◽  
...  
Keyword(s):  
Cell Surface ◽  
Outer Membrane ◽  
Lipid A ◽  
Binding Protein ◽  
Resistance Mechanism ◽  
Multidrug Resistant ◽  
Penicillin Binding Protein ◽  
Gram Negative ◽  
Peptidoglycan Cell Wall ◽  
Selection Of

The Gram-negative bacterial outer membrane fortifies the cell against environmental toxins including antibiotics. Unique glycolipids called lipopolysaccharide/lipooligosaccharide (LPS/LOS) are enriched in the cell-surface monolayer of the outer membrane and promote antimicrobial resistance. Colistin, which targets the lipid A domain of LPS/LOS to lyse the cell, is the last-line treatment for multidrug-resistant Gram-negative infections. Lipid A is essential for the survival of most Gram-negative bacteria, but colistin-resistantAcinetobacter baumanniilacking lipid A were isolated after colistin exposure. Previously, strain ATCC 19606 was the onlyA. baumanniistrain demonstrated to subsist without lipid A. Here, we show that otherA. baumanniistrains can also survive without lipid A, but some cannot, affording a unique model to study endotoxin essentiality. We assessed the capacity of 15 clinicalA. baumanniiisolates including 9 recent clinical isolates to develop colistin resistance through inactivation of the lipid A biosynthetic pathway, the products of which assemble the LOS precursor. Our investigation determined that expression of the well-conserved penicillin-binding protein (PBP) 1A, prevented LOS-deficient colony isolation. The glycosyltransferase activity of PBP1A, which aids in the polymerization of the peptidoglycan cell wall, was lethal to LOS-deficientA. baumannii. Global transcriptomic analysis of a PBP1A-deficient mutant and four LOS-deficientA. baumanniistrains showed a concomitant increase in transcription of lipoproteins and their transporters. Examination of the LOS-deficientA. baumanniicell surface demonstrated that specific lipoproteins were overexpressed and decorated the cell surface, potentially compensating for LOS removal. This work expands our knowledge of lipid A essentiality and elucidates a drug resistance mechanism.

scholarly journals Evaluation of an Immunochromatographic Assay for Rapid Detection of Penicillin-Binding Protein 2a in Human and Animal Staphylococcus intermedius Group, Staphylococcus lugdunensis, and Staphylococcus schleiferi Clinical Isolates

2015 ◽  
Vol 54 (3) ◽  
pp. 745-748 ◽  
Author(s):  
A. R. Arnold ◽  
C.-A. D. Burnham ◽  
B. A. Ford ◽  
S. D. Lawhon ◽  
S. K. McAllister ◽  
...  
Keyword(s):  
Rapid Detection ◽  
Binding Protein ◽  
Clinical Isolates ◽  
Immunochromatographic Assay ◽  
Penicillin Binding Protein ◽  
Beta Lactam ◽  
Staphylococcus Lugdunensis ◽  
Content Type ◽  
Staphylococcus Intermedius ◽  
Detection Assay

The performance of a rapid penicillin-binding protein 2a (PBP2a) detection assay, the Alere PBP2a culture colony test, was evaluated for identification of PBP2a-mediated beta-lactam resistance in human and animal clinical isolates ofStaphylococcus intermediusgroup,Staphylococcus lugdunensis, andStaphylococcus schleiferi. The assay was sensitive and specific, with all PBP2a-negative and PBP2a-positive strains testing negative and positive, respectively.

scholarly journals In Vitro Activity of Cefepime-Zidebactam, Ceftazidime-Avibactam, and Other Comparators against Clinical Isolates of Enterobacterales, Pseudomonas aeruginosa, and Acinetobacter baumannii: Results from China Antimicrobial Surveillance Network (CHINET) in 2018

2020 ◽  
Vol 65 (1) ◽  
pp. e01726-20
Author(s):  
Yang Yang ◽  
Yan Guo ◽  
Dandan Yin ◽  
Yonggui Zheng ◽  
Shi Wu ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Acinetobacter Baumannii ◽  
Clinical Isolates ◽  
Surveillance Network ◽  
Gram Negative ◽  
Content Type ◽  
Highly Active ◽  
Carbapenem Resistant ◽  
Almost All

ABSTRACTThis study evaluated the in vitro activity of cefepime-zidebactam in comparison with that of ceftazidime-avibactam and other comparators against clinically significant Gram-negative bacillus isolates. A total of 3,400 nonduplicate Gram-negative clinical isolates were collected from 45 medical centers across China in the CHINET Program in 2018, including Enterobacterales (n = 2,228), Pseudomonas aeruginosa (n = 657), and Acinetobacter baumannii (n = 515). The activities of cefepime-zidebactam and 20 comparators were determined by broth microdilution as recommended by the Clinical and Laboratory Standards Institute. Cefepime-zidebactam demonstrated potent activity against almost all Enterobacterales (MIC50/90, 0.125/1 mg/liter) and good activity against P. aeruginosa (MIC50/90, 2/8 mg/liter). Among the 373 carbapenem-resistant Enterobacteriaceae isolates, 57.3% (213/373) and 15.3% (57/373) were positive for blaKPC-2 and blaNDM, respectively. Cefepime-zidebactam showed a MIC of ≤2 mg/liter for 92.0% (196/213) of blaKPC-2 producers and 79.7% (47/59) of blaNDM producers. Ceftazidime-avibactam showed good in vitro activity against Enterobacterales (MIC50/90, 0.25/2 mg/liter; 94.0% susceptible) and P. aeruginosa (MIC50/90, 4/16 mg/liter; 86.9% susceptible). Ceftazidime-avibactam was active against 9.1% of carbapenem-resistant Escherichia coli isolates (63.6% were blaNDM producers) and 84.6% of Klebsiella pneumoniae isolates (74.3% were blaKPC producers). Most (90.1%) blaKPC-2 producers were susceptible to ceftazidime-avibactam. Cefepime-zidebactam demonstrated limited activity (MIC50/90, 16/32 mg/liter) against the 515 A. baumannii isolates (79.2% were carbapenem resistant), and ceftazidime-avibactam was less active (MIC50/90, 64/>64 mg/liter). Cefepime-zidebactam was highly active against clinical isolates of Enterobacterales and P. aeruginosa, including blaKPC-2-positive Enterobacterales and blaNDM-positive Enterobacterales and carbapenem-resistant P. aeruginosa. And ceftazidime-avibactam was highly active against blaKPC-2-positive Enterobacterales and carbapenem-resistant P. aeruginosa.

scholarly journals Low-Molecular-Mass Penicillin Binding Protein 6b (DacD) Is Required for Efficient GOB-18 Metallo-β-Lactamase Biogenesis in Salmonella enterica and Escherichia coli

2013 ◽  
Vol 58 (1) ◽  
pp. 205-211 ◽  
Author(s):  
Luciano Brambilla ◽  
Jorgelina Morán-Barrio ◽  
Alejandro M. Viale
Keyword(s):  
Escherichia Coli ◽  
Molecular Mass ◽  
Salmonella Enterica ◽  
Metal Ion ◽  
Binding Protein ◽  
Gram Negative Bacteria ◽  
Penicillin Binding Protein ◽  
Biofilm Growth ◽  
Gram Negative ◽  
Content Type

ABSTRACTMetallo-β-lactamases (MBLs) are Zn2+-containing secretory enzymes of clinical relevance, whose final folding and metal ion assembly steps in Gram-negative bacteria occur after secretion of the apo form to the periplasmic space. In the search of periplasmic factors assisting MBL biogenesis, we found thatdacDnull (ΔdacD) mutants ofSalmonella entericaandEscherichia coliexpressing the pre-GOB-18 MBL gene from plasmids showed significantly reduced resistance to cefotaxime and concomitant lower accumulation of GOB-18 in the periplasm. This reduced accumulation of GOB-18 resulted from increased accessibility to proteolytic attack in the periplasm, suggesting that the lack of DacD negatively affects the stability of secreted apo MBL forms. Moreover, ΔdacDmutants ofS. entericaandE. colishowed an altered ability to develop biofilm growth. DacD is a widely distributed low-molecular-mass (LMM) penicillin binding protein (PBP6b) endowed with lowdd-carboxypeptidase activity whose functions are still obscure. Our results indicate roles for DacD in assisting biogenesis of particular secretory macromolecules in Gram-negative bacteria and represent to our knowledge the first reported phenotypes for bacterial mutants lacking this LMM PBP.

scholarly journals Novel Phage Lysin Capable of Killing the Multidrug-Resistant Gram-Negative Bacterium Acinetobacter baumannii in a Mouse Bacteremia Model

2015 ◽  
Vol 59 (4) ◽  
pp. 1983-1991 ◽  
Author(s):  
Rolf Lood ◽  
Benjamin Y. Winer ◽  
Adam J. Pelzek ◽  
Roberto Diez-Martinez ◽  
Mya Thandar ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Genomic Library ◽  
Multidrug Resistant ◽  
Clinical Isolates ◽  
Gram Negative ◽  
Content Type ◽  
Highly Active ◽  
Genes Encoding

ABSTRACTAcinetobacter baumannii, a Gram-negative multidrug-resistant (MDR) bacterium, is now recognized as one of the more common nosocomial pathogens. Because most clinical isolates are found to be multidrug resistant, alternative therapies need to be developed to control this pathogen. We constructed a bacteriophage genomic library based on prophages induced from 13A. baumanniistrains and screened it for genes encoding bacteriolytic activity. Using this approach, we identified 21 distinct lysins with different activities and sequence diversity that were capable of killingA. baumannii. The lysin (PlyF307) displaying the greatest activity was further characterized and was shown to efficiently kill (>5-log-unit decrease) all testedA. baumanniiclinical isolates. Treatment with PlyF307 was able to significantly reduce planktonic and biofilmA. baumanniibothin vitroandin vivo. Finally, PlyF307 rescued mice from lethalA. baumanniibacteremia and as such represents the first highly active therapeutic lysin specific for Gram-negative organisms in an array of native lysins found inAcinetobacterphage.

scholarly journals In VitroActivity of Aztreonam-Avibactam against a Global Collection of Gram-Negative Pathogens from 2012 and 2013

2015 ◽  
Vol 59 (7) ◽  
pp. 4239-4248 ◽  
Author(s):  
Douglas J. Biedenbach ◽  
Krystyna Kazmierczak ◽  
Samuel K. Bouchillon ◽  
Daniel F. Sahm ◽  
Patricia A. Bradford
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Clinical Isolates ◽  
Broth Microdilution ◽  
Gram Negative ◽  
Content Type ◽  
Class A ◽  
Medical Centers ◽  
Fixed Concentration ◽  
Class B

ABSTRACTThe combination of aztreonam plus avibactam is being developed for use in infections caused by metallo-β-lactamase-producingEnterobacteriaceaestrains that also produce serine β-lactamases. Thein vitroactivities of aztreonam-avibactam and comparator antimicrobials were determined against year 2012 and 2013 clinical isolates ofEnterobacteriaceae,Pseudomonas aeruginosa, andAcinetobacter baumanniiusing the broth microdilution methodology recommended by the Clinical and Laboratory Standards Institute (CLSI). A total of 28,501 unique clinical isolates were obtained from patients in 190 medical centers within 39 countries. MIC90values of aztreonam and aztreonam-avibactam against all collected isolates ofEnterobacteriaceae(n= 23,516) were 64 and 0.12 μg/ml, respectively, with 76.2% of the isolates inhibited by ≤4 μg/ml of aztreonam (the CLSI breakpoint) and 99.9% of the isolates inhibited by ≤4 μg/ml of aztreonam-avibactam using a fixed concentration of 4 μg/ml of avibactam. The MIC90was 32 μg/ml for both aztreonam and aztreonam-avibactam againstP. aeruginosa(n= 3,766). Aztreonam alone or in combination with avibactam had noin vitroactivity against isolates ofA. baumannii. PCR and sequencing were used to characterize 5,076 isolates for β-lactamase genes. Aztreonam was not active against mostEnterobacteriaceaeisolates producing class A or class C enzymes alone or in combination with class B metallo-β-lactamases. In contrast, >99% ofEnterobacteriaceaeisolates producing all observed Ambler classes of β-lactamase enzymes were inhibited by ≤4 μg/ml aztreonam in combination with avibactam, including isolates that produced IMP-, VIM-, and NDM-type metallo-β-lactamases in combination with multiple serine β-lactamases.

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