28 Apr 20:32
by Lenhard JR, Thamlikitkul V, Silveira FP, et al.
<span class="paragraphSection"><strong>Objectives:</strong> The emergence of polymyxin resistance threatens to leave clinicians with few options for combatting drug-resistant <span style="font-style:italic;">Acinetobacter baumannii</span>. The objectives of the current investigation were to define the <span style="font-style:italic;">in vitro</span> emergence of polymyxin resistance and identify a combination regimen capable of eradicating <span style="font-style:italic;">A. baumannii</span> with no apparent drug susceptibilities.<strong>Methods:</strong> Two clonally related, paired, <span style="font-style:italic;">A. baumannii</span> isolates collected from a critically ill patient who developed colistin resistance while receiving colistin methanesulfonate in a clinical population pharmacokinetic study were evaluated: an <span style="font-style:italic;">A. baumannii</span> isolate collected before (03-149.1, polymyxin-susceptible, MIC 0.5 mg/L) and an isolate collected after (03-149.2, polymyxin-resistant, MIC 32 mg/L, carbapenem-resistant, ampicillin/sulbactam-resistant). Using the patient’s unique pharmacokinetics, the patient’s actual regimen received in the clinic was recreated in a hollow-fibre infection model (HFIM) to track the emergence of polymyxin resistance against 03-149.1. A subsequent HFIM challenged the pan-resistant 03-149.2 isolate against polymyxin B, meropenem and ampicillin/sulbactam alone and in two-drug and three-drug combinations.<strong>Results:</strong> Despite achieving colistin steady-state targets of an AUC<sub>0–24</sub> >60 mg·h/L and <span style="font-style:italic;">C</span><sub>avg</sub> of >2.5 mg/L, colistin population analysis profiles confirmed the clinical development of polymyxin resistance. During the simulation of the patient’s colistin regimen in the HFIM, no killing was achieved in the HFIM and amplification of polymyxin resistance was observed by 96 h. Against the polymyxin-resistant isolate, the triple combination of polymyxin B, meropenem and ampicillin/sulbactam eradicated the <span style="font-style:italic;">A. baumannii</span> by 96 h in the HFIM, whereas monotherapies and double combinations resulted in regrowth.<strong>Conclusions:</strong> To combat polymyxin-resistant <span style="font-style:italic;">A. baumannii</span>, the triple combination of polymyxin B, meropenem and ampicillin/sulbactam holds great promise.</span>
25 Apr 15:15
Mohammad J. Nasiri, Mehri Haeili, Mona Ghazi, Hossein Goudarzi, Ali Pormohammad, Abbas A. Imani Fooladi, Mohammad M. Feizabadi
25 Apr 14:19
by Akinori Okano, Nicholas A. Isley and Dale L. Boger
Chemical Reviews
DOI: 10.1021/acs.chemrev.6b00820
20 Apr 22:55
Gut microbes play wide-ranging roles in health and disease, but there has been a lack of tools to probe the relationship between microbial activity and host physiology. Two independent studies in mice published April 20 in the journal Cell have overcome this hurdle, making it possible to simultaneously visualize multiple bacterial strains in the gut by making them express unique combinations of fluorescent proteins. This approach allowed the researchers to pinpoint the location of the bacteria in the gut based on the rainbow of colors they emitted. Additionally, these tools also allowed precise control of the activity of bacterial genes in real time and in specific locations.
23 Mar 20:26
by Wuyu Mao, Lingying Xia, Hexin Xie
Abstract
Antibiotic resistance has become a major challenge to public health worldwide. This crisis is further aggravated by the increasing emergence of bacterial resistance to carbapenems, typically considered as the antibiotics of last resort, which is mainly due to the production of carbapenem-hydrolyzing carbapenemases in bacteria. Herein, the carbapenem-based fluorogenic probe CB-1 with an unprecedented enamine–BODIPY switch is developed for the detection of carbapenemase activity. This reagent is remarkably specific towards carbapenemases over other prevalent β-lactamases. Furthermore, the efficient imaging of live clinically important carbapenemase-producing organisms (CPOs) with CB-1 demonstrates its potential for the rapid detection of antibiotic resistance and timely diagnosis of CPO infections.
Lighting up resistance: A fluorogenic probe for the detection of carbapenemase activity has been developed. The utilization of carbapenem as the enzyme recognition motif in this reagent leads to remarkable specificity for carbapenemases over other prevailing β-lactamases, enabling the rapid detection of carbapenemases.
Yong and -1 others like this
20 Mar 19:10
For decades, the tiny roundworm C. elegans has been a vital tool in the biomedical researcher's toolkit, proving central to groundbreaking discoveries such as green fluorescent protein, the molecular marker used universally across research labs. Now, scientists in the laboratories of Shai Shaham and Eric D. Siggia at Rockefeller University are pushing the envelope even further on what C. elegans can teach us. They are developing technologies to study new aspects of how organs and nervous systems develop in these useful creatures.
03 Mar 20:59
Publication date: April 2017
Source:Current Opinion in Microbiology, Volume 36
Author(s): Manuel Pazos, Katharina Peters, Waldemar Vollmer
In Gram-negative bacteria such as Escherichia coli the peptidoglycan sacculus resides in the periplasm, a compartment that experiences changes in pH value, osmolality, ion strength and other parameters depending on the cell’s environment. Hence, the cell needs robust peptidoglycan growth mechanisms to grow and divide under different conditions. Here we propose a model according to which the cell achieves robust peptidoglycan growth by employing dynamic multi-protein complexes, which assemble with variable composition from freely diffusing sets of peptidoglycan synthases, hydrolases and their regulators, whereby the composition of the active complexes depends on the cell cycle state – cell elongation or division – and the periplasmic growth conditions.
03 Mar 20:56
The World Health Organization outlines critical-, high-, and medium-priority antibiotic development initiatives, calling on the public and private sectors to invest in additional R&D.
22 Feb 12:56
Publication date: June 2017
Source:Trends in Microbiology, Volume 25, Issue 6
Author(s): Roel M. van Harten, Rob J.L. Willems, Nathaniel I. Martin, Antoni P.A. Hendrickx
Over the past two decades infections due to antibiotic-resistant bacteria have escalated world-wide, affecting patient morbidity, mortality, and health care costs. Among these bacteria, Enterococcus faecium and Enterococcus faecalis represent opportunistic nosocomial pathogens that cause difficult-to-treat infections because of intrinsic and acquired resistance to a plethora of antibiotics. In recent years, a number of novel antimicrobial compound classes have been discovered and developed that target Gram-positive bacteria, including E. faecium and E. faecalis. These new antibacterial agents include teixobactin (targeting lipid II and lipid III), lipopeptides derived from nisin (targeting lipid II), dimeric vancomycin analogues (targeting lipid II), sortase transpeptidase inhibitors (targeting the sortase enzyme), alanine racemase inhibitors, lipoteichoic acid synthesis inhibitors (targeting LtaS), various oxazolidinones (targeting the bacterial ribosome), and tarocins (interfering with teichoic acid biosynthesis). The targets of these novel compounds and mode of action make them very promising for further antimicrobial drug development and future treatment of Gram-positive bacterial infections. Here we review current knowledge of the most favorable anti-enterococcal compounds along with their implicated modes of action and efficacy in animal models to project their possible future use in the clinical setting.
21 Feb 13:28
by Ramkumar Iyer, Mark A. Sylvester, Camilo Velez-Vega, Ruben Tommasi, Thomas F. Durand-Reville and Alita A. Miller
ACS Infectious Diseases
DOI: 10.1021/acsinfecdis.6b00197
10 Feb 12:32
Publication date: August 2017
Source:Current Opinion in Biotechnology, Volume 46
Author(s): Jingyan Zhang, Amy D Holdorf, Albertha JM Walhout
Resident microbes of the human body, particularly the gut microbiota, provide essential functions for the host, and, therefore, have important roles in human health as well as mitigating disease. It is difficult to study the mechanisms by which the microbiota affect human health, especially at a systems-level, due to heterogeneity of human genomes, the complexity and heterogeneity of the gut microbiota, the challenge of growing these bacteria in the laboratory, and the lack of bacterial genetics in most microbiotal species. In the last few years, the interspecies model of the nematode Caenorhabditis elegans and its bacterial diet has proven powerful for studying host–microbiota interactions, as both the animal and its bacterial diet can be subjected to large-scale and high-throughput genetic screening. The high level of homology between many C. elegans and human genes, as well as extensive similarities between human and C. elegans metabolism, indicates that the findings obtained from this interspecies model may be broadly relevant to understanding how the human microbiota affects physiology and disease. In this review, we summarize recent systems studies on how bacteria interact with C. elegans and affect life history traits.
07 Feb 14:17
Developing new ways to quickly diagnose illnesses in farm animals – allowing vets to administer effective, targeted treatment – could play a key role in helping to tackle the growing threat of antibiotic resistance, according to a Kingston University microbiology expert.
06 Feb 12:49
by Takuma Kawazura, Kanon Matsumoto, Koki Kojima, Fumiya Kato, Tomomi Kanai, Hironori Niki, Daisuke Shiomi
Summary
Cell polarity determines the direction of cell growth in bacteria. MreB actin spatially regulates peptidoglycan synthesis to enable cells to elongate bidirectionally. MreB densely localizes in the cylindrical part of the rod cell and not in polar regions in Escherichia coli. When treated with A22, which inhibits MreB polymerization, rod-shaped cells became round and MreB was diffusely distributed throughout the cytoplasmic membrane. A22 removal resulted in restoration of the rod shape. Initially, diffuse MreB started to re-assemble, and MreB-free zones were subsequently observed in the cytoplasmic membrane. These MreB-free zones finally became cell poles, allowing the cells to elongate bidirectionally. When MreB was artificially located at the cell poles, an additional pole was created, indicating that artificial localization of MreB at the cell pole induced local peptidoglycan synthesis. It was found that the anionic phospholipids (aPLs), phosphatidylglycerol and cardiolipin, which were enriched in cell poles preferentially interact with monomeric MreB compared with assembled MreB in vitro. MreB tended to localize to cell poles in cells lacking both aPLs, resulting in production of Y-shaped cells. Their findings indicated that aPLs exclude assembled MreB from cell poles to establish cell polarity, thereby allowing cells to elongate in a particular direction.
MreB actin is important to regulate cell polarity in E. coli although the mechanism is unclear. When MreB, which normally localizes to the central cylinder, is localized to cell caps by its mutation, DivIVA fusion or in ΔaPLs cells, cells result in acquisition of a new polarity, yielding branched cells. We found that MreB is excluded from cell caps by anionic phospholipids (aPLs: PG and CL) in wild-type E. coli.
02 Feb 19:48
by Danae Morales Angeles, Yun Liu, Alwin M. Hartman, Marina Borisova, Anabela de Sousa Borges, Niels de Kok, Katrin Beilharz, Jan-Willem Veening, Christoph Mayer, Anna K.H. Hirsch, Dirk-Jan Scheffers
Summary
Peptidoglycan (PG), the major component of the bacterial cell wall, is one large macromolecule. To allow for the different curvatures of PG at cell poles and division sites, there must be local differences in PG architecture and eventually also chemistry. Here we report such local differences in the Gram-positive rod-shaped model organism Bacillus subtilis. Single-cell analysis after antibiotic treatment and labeling of the cell wall with a fluorescent analogue of vancomycin or the fluorescent D-amino acid analogue (FDAA) HCC-amino-D-alanine revealed that PG at the septum contains muropeptides with unprocessed stem peptides (pentapeptides). Whereas these pentapeptides are normally shortened after incorporation into PG, this activity is reduced at division sites indicating either a lower local degree of PG crosslinking or a difference in PG composition, which could be a topological marker for other proteins. The pentapeptides remain partially unprocessed after division when they form the new pole of a cell. The accumulation of unprocessed PG at the division site is not caused by the activity of the cell division specific penicillin-binding protein 2B. To our knowledge, this is the first indication of local differences in the chemical composition of PG in Gram-positive bacteria.
The large macromolecule peptidoglycan, that forms the bacterial cell wall, contains local differences in architecture and chemistry that encode the shape of the wall. We used different probes to label peptidoglycan in combination with antibiotics treatments, to show that peptidoglycan at the cell division site of Bacillus subtilis is enriched in unprocessed stem peptides. This work provides the first indication of non-homogeneous peptidoglycan chemistry in Gram-positive bacteria.
01 Feb 23:34
Three methods identify and activate silent bacterial gene clusters to uncover new drugs
23 Jan 14:49
by Sanne A. M. van Lith, Sander M. J. van Duijnhoven, Anna C. Navis, Edward Dolk, Jos W. H. Wennink, Cornelus F. van Nostrum, Jan C. M. van Hest, William P. J. Leenders, Sanne A. M. van Lith, Sander M. J. van Duijnhoven, Anna C. Navis, William P. J. Leenders, Edward Dolk, Jos W. H. Wennink, Cornelus F. van Nostrum and Jan C. M. van Hest
Bioconjugate Chemistry
DOI: 10.1021/acs.bioconjchem.6b00638
23 Jan 14:45
Person-to-person transmission of carbapenem-resistant Enterobacteriaceae in US hospitals may be occurring without symptoms, a new study suggests.
23 Jan 14:45
Inspired by President-elect Donald Trump's signature hairdo, a biologist named a new species of moth with yellowish-white scales on its head Neopalpa donaldtrumpi.
23 Jan 14:43
by Ranjit, D. K., Jorgenson, M. A., Young, K. D.
Peptidoglycan is a vital component of nearly all cell wall-bearing bacteria and is a valuable target for antibacterial therapy. However, despite decades of work, there remain important gaps in understanding how this macromolecule is synthesized and molded into a three-dimensional structure that imparts specific morphologies to individual cells. Here, we investigate the particularly enigmatic area of how peptidoglycan is synthesized and shaped during the first stages of creating cell shape de novo, that is, in the absence of a pre-existing template. We found that when lysozyme-induced (LI-) spheroplasts of Escherichia coli were allowed to resynthesize peptidoglycan, the cells divided first and then elongated to recreate normal rod shaped morphology. Penicillin binding protein 1B (PBP1B) was critical for the first stage of this recovery process. PBP1B synthesized peptidoglycan de novo and this synthesis required that PBP1B interact with the outer membrane lipoprotein LpoB. Surprisingly, when LpoB was localized improperly to the inner membrane, recovering spheroplasts synthesized peptidoglycan and divided but then propagated as amorphous spheroidal cells, suggesting that regenerating a normal rod shape depends on a particular spatial interaction. Similarly, spheroplasts carrying a PBP1B variant lacking transpeptidase activity or those in which PBP1A was overproduced could synthesize new peptidoglycan and divide, but then grew as oddly shaped spheroids. We conclude that de novo cell wall synthesis requires the glycosyltransferase activity of PBP1B, but that PBP1B transpeptidase activity is needed to assemble cell walls with wild type morphology.
Importance Bacterial cell wall peptidoglycan is synthesized and modified by penicillin binding proteins (PBPs), which are targeted by about half of all currently prescribed antibiotics, including penicillin and its derivatives. Because antibiotic resistance is rising, it has become increasingly urgent that we fill the gaps in our knowledge about how PBPs create and assemble this protective wall. We report here that PBP1B plays an essential role in synthesizing peptidoglycan in the absence of a pre-existing template – its glycosyltransferase activity is responsible for de novo synthesis, while its transpeptidase activity is required to construct cell walls of a specific shape. These results highlight the importance of this enzyme and distinguish its biological roles from those of other PBPs and peptidoglycan synthases.
18 Jan 13:40
by David A. Dik, Teresa Domínguez-Gil, Mijoon Lee, Dusan Hesek, Byungjin Byun, Jennifer Fishovitz, Bill Boggess, Lance M. Hellman, Jed F. Fisher, Juan A. Hermoso and Shahriar Mobashery
Journal of the American Chemical Society
DOI: 10.1021/jacs.6b12819
