Antimicrobial Peptide Exposure Selects for Resistant and Fit Stenotrophomonas maltophilia Mutants That Show Cross-Resistance to Antibiotics

ABSTRACT Antimicrobial peptides (AMPs) are essential components of the innate immune system and have been proposed as promising therapeutic agents against drug-resistant microbes. AMPs possess a rapid bactericidal mode of action and can interact with different targets, but bacteria can also avoid their effect through a variety of resistance mechanisms. Apart from hampering treatment by the AMP itself, or that by other antibiotics in the case of cross-resistance, AMP resistance might also confer cross-resistance to innate human peptides and impair the anti-infective capability of the human host. A better understanding of how resistance to AMPs is acquired and the genetic mechanisms involved is needed before using these compounds as therapeutic agents. Using experimental evolution and whole-genome sequencing, we determined the genetic causes and the effect of acquired de novo resistance to three different AMPs in the opportunistic pathogen Stenotrophomonas maltophilia, a bacterium that is intrinsically resistant to a wide range of antibiotics. Our results show that AMP exposure selects for high-level resistance, generally without any reduction in bacterial fitness, conferred by mutations in different genes encoding enzymes, transporters, transcriptional regulators, and other functions. Cross-resistance to AMPs and to other antibiotic classes not used for selection, as well as collateral sensitivity, was observed for many of the evolved populations. The relative ease by which high-level AMP resistance is acquired, combined with the occurrence of cross-resistance to conventional antibiotics and the maintained bacterial fitness of the analyzed mutants, highlights the need for careful studies of S. maltophilia resistance evolution to clinically valuable AMPs. IMPORTANCE Stenotrophomonas maltophilia is an increasingly relevant multidrug-resistant (MDR) bacterium found, for example, in people with cystic fibrosis and associated with other respiratory infections and underlying pathologies. The infections caused by this nosocomial pathogen are difficult to treat due to the intrinsic resistance of this bacterium against a broad number of antibiotics. Therefore, new treatment options are needed, and considering the growing interest in using AMPs as alternative therapeutic compounds and the restricted number of antibiotics active against S. maltophilia, we addressed the potential for development of AMP resistance, the genetic mechanisms involved, and the physiological effects that acquisition of AMP resistance has on this opportunistic pathogen.

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Mechanisms and phenotypic consequences of acquisition of tigecycline resistance by Stenotrophomonas maltophilia

Journal of Antimicrobial Chemotherapy ◽

10.1093/jac/dkz326 ◽

2019 ◽

Vol 74 (11) ◽

pp. 3221-3230 ◽

Cited By ~ 1

Author(s):

Paula Blanco ◽

Fernando Corona ◽

José Luis Martinez

Keyword(s):

Stenotrophomonas Maltophilia ◽

Efflux Pump ◽

Maximum Growth ◽

Opportunistic Pathogen ◽

Resistance Mechanisms ◽

Fitness Cost ◽

Negative Regulator ◽

Cross Resistance ◽

Bacterial Fitness ◽

High Level

Abstract Objectives To elucidate the potential mutation-driven mechanisms involved in the acquisition of tigecycline resistance by the opportunistic pathogen Stenotrophomonas maltophilia. The mutational trajectories and their effects on bacterial fitness, as well as cross-resistance and/or collateral susceptibility to other antibiotics, were also addressed. Methods S. maltophilia populations were submitted to experimental evolution in the presence of increasing concentrations of tigecycline for 30 days. The genetic mechanisms involved in the acquisition of tigecycline resistance were determined by WGS. Resistance was evaluated by performing MIC assays. Fitness of the evolved populations and individual clones was assessed by measurement of the maximum growth rates. Results All the tigecycline-evolved populations attained high-level resistance to tigecycline following different mutational trajectories, yet with some common elements. Among the mechanisms involved in low susceptibility to tigecycline, mutations in the SmeDEF efflux pump negative regulator smeT, changes in proteins involved in the biogenesis of the ribosome and modifications in the LPS biosynthesis pathway seem to play a major role. Besides tigecycline resistance, the evolved populations presented cross-resistance to other antibiotics, such as aztreonam and quinolones, and they were hypersusceptible to fosfomycin, suggesting a possible combination treatment. Further, we found that the selected resistance mechanisms impose a relevant fitness cost when bacteria grow in the absence of antibiotic. Conclusions Mutational resistance to tigecycline was easily selected during exposure to this antibiotic. However, the fitness cost may compromise the maintenance of S. maltophilia tigecycline-resistant populations in the absence of antibiotic.

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Biochemical and molecular characterization of Alternaria alternata isolates highly resistant to procymidone from broccoli and cabbage

Phytopathology Research ◽

10.1186/s42483-021-00092-z ◽

2021 ◽

Vol 3 (1) ◽

Author(s):

Bingran Wang ◽

Tiancheng Lou ◽

Lingling Wei ◽

Wenchan Chen ◽

Longbing Huang ◽

...

Keyword(s):

Alternaria Alternata ◽

Single Point ◽

Sodium Dodecyl ◽

Cross Resistance ◽

Molecular Characteristics ◽

Single Point Mutation ◽

Wide Range ◽

Significant Difference ◽

Leaf Blights ◽

High Level

AbstractAlternaria alternata, a causal agent of leaf blights and spots on a wide range of hosts, has a high risk of developing resistance to fungicides. Procymidone, a dicarboximide fungicide (DCF), has been widely used in controlling Alternaria leaf blights in China for decades. However, the resistance of A. alternata against DCFs has rarely been reported from crucifer plants. A total of 198 A. alternata isolates were collected from commercial fields of broccoli and cabbage during 2018–2019, and their sensitivities to procymidone were determined. Biochemical and molecular characteristics were subsequently compared between the high-level procymidone-resistant (ProHR) and procymidone-sensitive (ProS) isolates, and also between ProHR isolates from broccoli and cabbage. Compared with ProS isolates, the mycelial growth rate, sporulation capacity and virulence of most ProHR isolates were reduced; ProHR isolates displayed an increased sensitivity to osmotic stresses and a reduced sensitivity to sodium dodecyl sulfate (SDS); all ProHR isolates showed a reduced sensitivity to hydrogen peroxide (H2O2) except for the isolate B102. Correlation analysis revealed a positive cross-resistance between procymidone and iprodione, or fludioxonil. When treated with 10 μg/mL of procymidone, both mycelial intracellular glycerol accumulations (MIGAs) and relative expression of AaHK1 in ProS isolates were higher than those in ProHR isolates. Sequence alignment of AaHK1 from ten ProHR isolates demonstrated that five of them possessed a single-point mutation (P94A, V612L, E708K or Q924STOP), and four isolates had an insertion or a deletion in their coding regions. No significant difference in biochemical characteristics was observed among ProHR isolates from two different hosts, though mutations in AaHK1 of the cabbage-originated ProHR isolates were distinct from those of the broccoli-originated ProHR isolates.

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Evidence for Inhibition of Topoisomerase 1A by Gold(III) Macrocycles and Chelates TargetingMycobacterium tuberculosisandMycobacterium abscessus

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01696-17 ◽

2018 ◽

Vol 62 (5) ◽

Cited By ~ 6

Author(s):

Rashmi Gupta ◽

Carolina Rodrigues Felix ◽

Matthew P. Akerman ◽

Kate J. Akerman ◽

Cathryn A. Slabber ◽

...

Keyword(s):

Mycobacterium Abscessus ◽

Cross Resistance ◽

Human Pathogens ◽

Intrinsic Resistance ◽

Content Type ◽

Starting Point ◽

Scalable Synthesis ◽

High Level ◽

Novel Drug

ABSTRACTMycobacterium tuberculosisand the fast-growing speciesMycobacterium abscessusare two important human pathogens causing persistent pulmonary infections that are difficult to cure and require long treatment times. The emergence of drug-resistantM. tuberculosisstrains and the high level of intrinsic resistance ofM. abscessuscall for novel drug scaffolds that effectively target both pathogens. In this study, we evaluated the activity of bis(pyrrolide-imine) gold(III) macrocycles and chelates, originally designed as DNA intercalators capable of targeting human topoisomerase types I and II (Topo1 and Topo2), againstM. abscessusandM. tuberculosis. We identified a total of 5 noncytotoxic compounds active against both mycobacterial pathogens under replicatingin vitroconditions. We chose one of these hits, compound 14, for detailed analysis due to its potent bactericidal mode of inhibition and scalable synthesis. The clinical relevance of this compound was demonstrated by its ability to inhibit a panel of diverseM. tuberculosisandM. abscessusclinical isolates. Prompted by previous data suggesting that compound 14 may target topoisomerase/gyrase enzymes, we demonstrated that it lacked cross-resistance with fluoroquinolones, which target theM. tuberculosisgyrase.In vitroenzyme assays confirmed the potent activity of compound 14 against bacterial topoisomerase 1A (Topo1) enzymes but not gyrase. Novel scaffolds like compound 14 with potent, selective bactericidal activity againstM. tuberculosisandM. abscessusthat act on validated but underexploited targets like Topo1 represent a promising starting point for the development of novel therapeutics for infections by pathogenic mycobacteria.

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Efficacy of Biocides Used in the Modern Food Industry To Control Salmonella enterica, and Links between Biocide Tolerance and Resistance to Clinically Relevant Antimicrobial Compounds

Applied and Environmental Microbiology ◽

10.1128/aem.07534-11 ◽

2012 ◽

Vol 78 (9) ◽

pp. 3087-3097 ◽

Cited By ~ 106

Author(s):

Orla Condell ◽

Carol Iversen ◽

Shane Cooney ◽

Karen A. Power ◽

Ciara Walsh ◽

...

Keyword(s):

Salmonella Enterica ◽

Food Industry ◽

Multidrug Resistant ◽

Cross Resistance ◽

Antimicrobial Compounds ◽

Cross Tolerance ◽

Content Type ◽

Food Grade ◽

High Level

ABSTRACTBiocides play an essential role in limiting the spread of infectious disease. The food industry is dependent on these agents, and their increasing use is a matter for concern. Specifically, the emergence of bacteria demonstrating increased tolerance to biocides, coupled with the potential for the development of a phenotype of cross-resistance to clinically important antimicrobial compounds, needs to be assessed. In this study, we investigated the tolerance of a collection of susceptible and multidrug-resistant (MDR)Salmonella entericastrains to a panel of seven commercially available food-grade biocide formulations. We explored their abilities to adapt to these formulations and their active biocidal agents, i.e., triclosan, chlorhexidine, hydrogen peroxide, and benzalkonium chloride, after sequential rounds ofin vitroselection. Finally, cross-tolerance of different categories of biocidal formulations, their active agents, and the potential for coselection of resistance to clinically important antibiotics were investigated. Six of seven food-grade biocide formulations were bactericidal at their recommended working concentrations. All showed a reduced activity against both surface-dried and biofilm cultures. A stable phenotype of tolerance to biocide formulations could not be selected. Upon exposure ofSalmonellastrains to an active biocidal compound, a high-level of tolerance was selected for a number ofSalmonellaserotypes. No cross-tolerance to the different biocidal agents or food-grade biocide formulations was observed. Most tolerant isolates displayed changes in their patterns of susceptibility to antimicrobial compounds. Food industry biocides are effective against planktonicSalmonella. When exposed to sublethal concentrations of individual active biocidal agents, tolerant isolates may emerge. This emergence was associated with changes in antimicrobial susceptibilities.

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Idification and structural characterisation of a catecholate-type siderophore produced by Stenotrophomonas maltophilia K279a

Microbiology ◽

10.1099/mic.0.001071 ◽

2021 ◽

Vol 167 (7) ◽

Author(s):

Atsushi Hisatomi ◽

Yuh Shiwa ◽

Nobuyuki Fujita ◽

Hiroyuki Koshino ◽

Naoto Tanaka

Keyword(s):

Stenotrophomonas Maltophilia ◽

Type Species ◽

Monomer Unit ◽

Reversed Phase ◽

Negative Bacterium ◽

Content Type ◽

Structural Characterisation ◽

Link Type ◽

Wide Range ◽

C Nmr

Siderophores are produced by several bacteria that utilise iron in various environments. Elucidating the structure of a specific siderophore may have valuable applications in drug development. Stenotrophomonas maltophilia , a Gram-negative bacterium that inhabits a wide range of environments and can cause pneumonia, produces siderophores. However, the structure was unknown, and therefore, in this study, we aimed to elucidate it. We purified siderophores from cultures of S. maltophilia K279a using preparative reversed-phase HPLC. The structure was analysed through LC-MS and 1H and 13C NMR. The results demonstrated that S. maltophilia K279a produces 2,3-dihydroxybenzoylserine (DHBS), a monomer unit of enterobactin. We suggested the uptake of Iron(III) by the DHBS complex. DHBS production by S. maltophilia K279a could be attributed to an incomplete enterobactin pathway. Drugs targeting DHBS synthesis could prevent S. maltophilia infection.

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Spatiotemporal Distribution of Pseudomonas aeruginosa Alkyl Quinolones under Metabolic and Competitive Stress

mSphere ◽

10.1128/msphere.00426-20 ◽

2020 ◽

Vol 5 (4) ◽

Author(s):

Tianyuan Cao ◽

Jonathan V. Sweedler ◽

Paul W. Bohn ◽

Joshua D. Shrout

Keyword(s):

Pseudomonas Aeruginosa ◽

Bacterial Species ◽

Metabolic Stress ◽

Opportunistic Pathogen ◽

Cell Interaction ◽

Chemical Imaging ◽

Carbon Limitation ◽

Bacterial Strains ◽

Content Type ◽

High Level

ABSTRACT Pseudomonas aeruginosa is an opportunistic human pathogen important to diseases such as cystic fibrosis. P. aeruginosa has multiple quorum-sensing (QS) systems, one of which utilizes the signaling molecule 2-heptyl-3-hydroxy-4-quinolone (Pseudomonas quinolone signal [PQS]). Here, we use hyperspectral Raman imaging to elucidate the spatiotemporal PQS distributions that determine how P. aeruginosa regulates surface colonization and its response to both metabolic stress and competition from other bacterial strains. These chemical imaging experiments illustrate the strong link between environmental challenges, such as metabolic stress caused by nutritional limitations or the presence of another bacterial species, and PQS signaling. Metabolic stress elicits a complex response in which limited nutrients induce the bacteria to produce PQS earlier, but the bacteria may also pause PQS production entirely if the nutrient concentration is too low. Separately, coculturing P. aeruginosa in the proximity of another bacterial species, or its culture supernatant, results in earlier production of PQS. However, these differences in PQS appearance are not observed for all alkyl quinolones (AQs) measured; the spatiotemporal response of 2-heptyl-4-hydroxyquinoline N-oxide (HQNO) is highly uniform for most conditions. These insights on the spatiotemporal distributions of quinolones provide additional perspective on the behavior of P. aeruginosa in response to different environmental cues. IMPORTANCE Alkyl quinolones (AQs), including Pseudomonas quinolone signal (PQS), made by the opportunistic pathogen Pseudomonas aeruginosa have been associated with both population density and stress. The regulation of AQ production is known to be complex, and the stimuli that modulate AQ responses are not fully clear. Here, we have used hyperspectral Raman chemical imaging to examine the temporal and spatial profiles of AQs exhibited by P. aeruginosa under several potentially stressful conditions. We found that metabolic stress, effected by carbon limitation, or competition stress, effected by proximity to other species, resulted in accelerated PQS production. This competition effect did not require cell-to-cell interaction, as evidenced by the fact that the addition of supernatants from either Escherichia coli or Staphylococcus aureus led to early appearance of PQS. Lastly, the fact that these modulations were observed for PQS but not for all AQs suggests a high level of complexity in AQ regulation that remains to be discerned.

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Clinical and Microbiologic Outcomes in Patients with Monomicrobial Stenotrophomonas maltophilia Infections

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00788-19 ◽

2019 ◽

Vol 63 (11) ◽

Cited By ~ 1

Author(s):

Cara Nys ◽

Kartik Cherabuddi ◽

Veena Venugopalan ◽

Kenneth P. Klinker

Keyword(s):

Nosocomial Infections ◽

Clinical Cure ◽

Stenotrophomonas Maltophilia ◽

Opportunistic Pathogen ◽

Content Type ◽

High Cure ◽

Resistance Selection ◽

Biofilm Production ◽

Cure Rates

ABSTRACT Stenotrophomonas maltophilia is an opportunistic pathogen observed in nosocomial infections. Due to biofilm production and resistance to numerous antimicrobials, eradication is difficult. This study evaluated outcomes for monomicrobial S. maltophilia infections. Seventy-six patients were included, with 45 patients on trimethoprim-sulfamethoxazole and 31 patients on levofloxacin. Overall clinical cure, microbiological eradication, and 28-day mortality were observed in 79%, 82%, and 14% of patients, respectively. The use of trimethoprim-sulfamethoxazole or levofloxacin resulted in high cure rates; however, a trend toward resistance selection with levofloxacin was identified.

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Analysis of the Functional Contributions of Asn233 in Metallo-β-Lactamase IMP-1

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00340-11 ◽

2011 ◽

Vol 55 (12) ◽

pp. 5696-5702 ◽

Cited By ~ 20

Author(s):

Nicholas G. Brown ◽

Lori B. Horton ◽

Wanzhi Huang ◽

Sompong Vongpunsawad ◽

Timothy Palzkill

Keyword(s):

Amino Acid ◽

Kinetic Parameters ◽

Bacterial Resistance ◽

Content Type ◽

Protein Levels ◽

Dependent Sequence ◽

Wide Range ◽

High Level ◽

Sequence Requirements ◽

Asparagine Residue

ABSTRACTMetallo-β-lactamases, such as IMP-1, are a major global health threat, as they provide for bacterial resistance to a wide range of β-lactam antibiotics, including carbapenems. Understanding the molecular details of the enzymatic process and the sequence requirements for function are essential aids in overcoming β-lactamase-mediated resistance. An asparagine residue is conserved at position 233 in approximately 67% of all metallo-β-lactamases. Despite its conservation, the molecular basis of Asn233 function is poorly understood and remains controversial. It has previously been shown that mutations at this site exhibit context-dependent sequence requirements in that the importance of a given amino acid depends on the antibiotic being tested. To provide a more thorough examination as to the function and sequence requirements at this position, a collection of IMP-1 mutants encoding each of the 19 possible amino acid substitutions was generated. The resistance levels toward four β-lactam antibiotics were measured forEscherichia colicontaining each of these mutants. The sequence requirements at position 233 for wild-type levels of resistance toward two cephalosporins were the most relaxed, while there were more stringent sequence requirements for resistance to ampicillin or imipenem. Enzyme kinetic analysis and determinations of steady-state protein levels indicated that the effects of the substitutions on resistance are due to changes in the kinetic parameters of the enzyme. Taken together, the results indicate that substitutions at position 233 significantly alter the kinetic parameters of the enzyme, but most substituted enzymes are able to provide for a high level of resistance to a broad range of β-lactams.

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Deciphering the Contribution of Human Meningothelial Cells to the Inflammatory and Antimicrobial Response at the Meninges

Infection and Immunity ◽

10.1128/iai.00477-13 ◽

2013 ◽

Vol 81 (11) ◽

pp. 4299-4310 ◽

Cited By ~ 9

Author(s):

Pierre-Joseph Royer ◽

Andrew J. Rogers ◽

Karl G. Wooldridge ◽

Patrick Tighe ◽

Jafar Mahdavi ◽

...

Keyword(s):

Protein Kinase ◽

Intracellular Signaling ◽

Cell Activation ◽

Mitogen Activated Protein Kinase ◽

Meningococcal Infection ◽

Minor Role ◽

Content Type ◽

Wide Range ◽

Mitogen Activated Protein ◽

High Level

ABSTRACTWe have investigated the response of primary human meningothelial cells toNeisseria meningitidis. Through a transcriptome analysis, we provide a comprehensive examination of the response of meningothelial cells to bacterial infection. A wide range of chemokines are elicited which act to attract and activate the main players of innate and adaptive immunity. We showed that meningothelial cells expressed a high level of Toll-like receptor 4 (TLR4), and, using a gene silencing strategy, we demonstrated the contribution of this pathogen recognition receptor in meningothelial cell activation. Secretion of interleukin-6 (IL-6), CXCL10, and CCL5 was almost exclusively TLR4 dependent and relied on MyD88 and TRIF adaptor cooperation. In contrast, IL-8 induction was independent of the presence of TLR4, MyD88, and TRIF. Transcription factors NF-κB p65, p38 mitogen-activated protein kinase (MAPK), Jun N-terminal protein kinase (JNK1), IRF3, and IRF7 were activated after contact with bacteria. Interestingly, the protein kinase IRAK4 was found to play a minor role in the meningothelial cell response toNeisseriainfection. Our work highlights the role of meningothelial cells in the development of an immune response and inflammation in the central nervous system (CNS) in response to meningococcal infection. It also sheds light on the complexity of intracellular signaling after TLR triggering.

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Social mobility will fall for China’s disadvantaged

Emerald Expert Briefings ◽

10.1108/oxan-db244410 ◽

2019 ◽

Keyword(s):

Social Mobility ◽

Urban Areas ◽

Rural Poverty ◽

Credit System ◽

Absolute Poverty ◽

Content Type ◽

Social Credit ◽

The Social ◽

Wide Range ◽

High Level

Subject Social mobility in China. Significance So far, the Communist Party leadership has only addressed the most extreme manifestations of inequality -- high-level corruption and rural poverty. It has not tackled a wide range of social, economic and institutional barriers to social mobility that affect hundreds of millions of people across the country. Impacts Members of China’s middle class are already approaching the limits of their upward mobility. The social credit system could evolve in a way that exacerbates the divide between the economically advantaged and disadvantaged. The campaign to eliminate absolute poverty will do little to address the problem of relative poverty in urban areas.

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