Transposon-Derived Brucella abortusRough Mutants Are Attenuated and Exhibit Reduced Intracellular Survival

1998 ◽  
Vol 66 (3) ◽  
pp. 1008-1016 ◽  
Author(s):  
Chris A. Allen ◽  
L. Garry Adams ◽  
Thomas A. Ficht
Keyword(s):  
Sequence Analysis ◽  
Polymyxin B ◽  
Intracellular Survival ◽  
Phagocytic Cells ◽  
Gene Encoding ◽  
Amphipathic Peptide ◽  
O Antigen ◽  
Genes Encoding ◽  
Definition Of

ABSTRACT The O antigen of Brucella abortus has been described as a major virulence determinant based on the attenuated survival of fortuitously isolated rough variants. However, the lack of genetic definition of these mutants and the virulence of naturally occurring rough species, Brucella ovis and Brucella canis, has confused interpretation. To better characterize the role of O antigen in virulence and survival, transposon mutagenesis was used to generate B. abortus rough mutants defective in O-antigen presentation. Sequence analysis of DNA flanking the site of Tn5 insertion was used to verify insertion in genes encoding lipopolysaccharide (LPS) biosynthetic functions. Not surprisingly, each of the rough mutants was attenuated for survival in mice, but unexpected differences among the mutants were observed. In an effort to define the basis for the observed differences, the structure of the rough LPS and the sensitivity of these mutants to individual killing mechanisms were examined in vitro. All of the B. abortus rough mutants exhibited a 4- to 5-log-unit increase, compared to the smooth parental strain, in sensitivity to complement-mediated lysis. Little change was evident in the sensitivity of these organisms to hydrogen peroxide, consistent with an inability of O antigen to exclude relatively small molecules. Sensitivity to polymyxin B, which was employed as a model cationic, amphipathic peptide similar to defensins found in phagocytic cells, revealed survival differences among the rough mutants similar to those observed in the mouse. One mutant in particular exhibited hypersensitivity to polymyxin B and reduced survival in mice. This mutant was characterized by a truncated rough LPS. DNA sequence analysis of this mutant revealed a transposon interruption in the gene encoding phosphomannomutase (pmm), suggesting that this activity may be required for the synthesis of a full-length core polysaccharide in addition to O antigen. B. abortus O antigen appears to be essential for extra- and intracellular survival in mice.

scholarly journals An iron-regulated LysR-type element mediates antimicrobial peptide resistance and virulence in Yersinia pseudotuberculosis

Microbiology ◽  
2009 ◽  
Vol 155 (7) ◽  
pp. 2168-2181 ◽  
Author(s):  
Sonia Arafah ◽  
Marie-Laure Rosso ◽  
Linda Rehaume ◽  
Robert E. W. Hancock ◽  
Michel Simonet ◽  
...  
Keyword(s):  
Antimicrobial Peptide ◽  
Yersinia Pseudotuberculosis ◽  
Polymyxin B ◽  
Uptake System ◽  
Mesenteric Lymph Nodes ◽  
Iron Starvation ◽  
Iron Deprivation ◽  
Genes Encoding ◽  
Antimicrobial Peptide Resistance

During the course of its infection of the mammalian digestive tract, the entero-invasive, Gram-negative bacterium Yersinia pseudotuberculosis must overcome various hostile living conditions (notably, iron starvation and the presence of antimicrobial compounds produced in situ). We have previously reported that in vitro bacterial growth during iron deprivation raises resistance to the antimicrobial peptide polymyxin B; here, we show that this phenotype is mediated by a chromosomal gene (YPTB0333) encoding a transcriptional regulator from the LysR family. We determined that the product of YPTB0333 is a pleiotropic regulator which controls (in addition to its own expression) genes encoding the Yfe iron-uptake system and polymyxin B resistance. Lastly, by using a mouse model of oral infection, we demonstrated that YPTB0333 is required for colonization of Peyer's patches and mesenteric lymph nodes by Y. pseudotuberculosis.

scholarly journals The Neisseria meningitidis Capsule Is Important for Intracellular Survival in Human Cells

2007 ◽  
Vol 75 (7) ◽  
pp. 3594-3603 ◽  
Author(s):  
Maria Rita Spinosa ◽  
Cinzia Progida ◽  
Adelfia Talà ◽  
Laura Cogli ◽  
Pietro Alifano ◽  
...  
Keyword(s):  
Neisseria Meningitidis ◽  
Efflux Pump ◽  
Polymyxin B ◽  
Intracellular Survival ◽  
Outer Core ◽  
Human Cells ◽  
In Vitro Assays ◽  
Bacterial Survival ◽  
Innate Defense

ABSTRACT While much data exist in the literature about how Neisseria meningitidis adheres to and invades human cells, its behavior inside the host cell is largely unknown. One of the essential meningococcal attributes for pathogenesis is the polysaccharide capsule, which has been shown to be important for bacterial survival in extracellular fluids. To investigate the role of the meningococcal capsule in intracellular survival, we used B1940, a serogroup B strain, and its isogenic derivatives, which lack either the capsule or both the capsule and the lipooligosaccharide outer core, to infect human phagocytic and nonphagocytic cells and monitor invasion and intracellular growth. Our data indicate that the capsule, which negatively affects bacterial adhesion and, consequently, entry, is, in contrast, fundamental for the intracellular survival of this microorganism. The results of in vitro assays suggest that an increased resistance to cationic antimicrobial peptides (CAMPs), important components of the host innate defense system against microbial infections, is a possible mechanism by which the capsule protects the meningococci in the intracellular environment. Indeed, unencapsulated bacteria were more susceptible than encapsulated bacteria to defensins, cathelicidins, protegrins, and polymyxin B, which has long been used as a model compound to define the mechanism of action of CAMPs. We also demonstrate that both the capsular genes (siaD and lipA) and those encoding an efflux pump involved in resistance to CAMPs (mtrCDE) were up-regulated during the intracellular phase of the infectious cycle.

scholarly journals Interactions of polymyxin B in combination with aztreonam, minocycline, meropenem and rifampicin against Escherichia coli producing NDM and OXA-48-group carbapenemases

2021 ◽  
Author(s):  
Anna Olsson ◽  
Marcus Hong ◽  
Hissa Al-Farsi ◽  
Christian G. Giske ◽  
Pernilla Lagerbäck ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Lipid A ◽  
Time Lapse ◽  
Polymyxin B ◽  
Positive Interactions ◽  
Exact Test ◽  
E Coli ◽  
Genes Encoding ◽  
Severe Infections

Objectives. Carbapenemase-producing Enterobacterales pose an increasing medical threat. Combination therapy is often used for severe infections; however, there is little evidence supporting the optimal selection of drugs. This study aimed to determine the in vitro effects of polymyxin B combinations against carbapenemase-producing Escherichia coli . Methods. The interactions of polymyxin B in combination with aztreonam, meropenem, minocycline or rifampicin against 20 clinical isolates of NDM and OXA-48-group-producing E. coli were evaluated using time-lapse microscopy. 24-h samples were spotted on plates with and without 4 x MIC polymyxin B for viable counts. Whole-genome sequencing was applied to identify resistance genes and mutations. Finally, potential associations between combination effects and bacterial genotypes were assessed using Fisher’s exact test. Results. Synergistic and bactericidal effects were observed with polymyxin B and minocycline against 11/20 strains and with polymyxin B and rifampicin against 9/20 strains. The combinations of polymyxin B and aztreonam or meropenem showed synergy against 2/20 strains. Negligible resistance development against polymyxin B was detected. Synergy with polymyxin B and minocycline was associated with genes involved in efflux (presence of tet(B) , wildtype soxR and the marB mutation H44Q) and lipopolysaccharide synthesis ( eptA C27Y, lpxB mutations and lpxK L323S). Synergy with polymyxin B and rifampicin was associated with sequence variations in arnT , which plays a role in lipid A modification. Conclusion. Polymyxin B in combination with minocycline or rifampicin frequently showed positive interactions against NDM- and OXA-48-group-producing E. coli . Synergy was associated with genes encoding efflux and components of the bacterial outer membrane.

scholarly journals Mutations in Salmonella Pathogenicity Island 2 (SPI2) Genes Affecting Transcription of SPI1 Genes and Resistance to Antimicrobial Agents

1998 ◽  
Vol 180 (18) ◽  
pp. 4775-4780 ◽  
Author(s):  
Jörg Deiwick ◽  
Thomas Nikolaus ◽  
Jaqueline E. Shea ◽  
Colin Gleeson ◽  
David W. Holden ◽  
...  
Keyword(s):  
Type Iii Secretion ◽  
Antimicrobial Agents ◽  
Type Iii Secretion System ◽  
Polymyxin B ◽  
Secretion System ◽  
Effector Proteins ◽  
Secretion Systems ◽  
Type Iii ◽  
Genes Encoding

ABSTRACT The Salmonella typhimurium genome contains two pathogenicity islands (SPI) with genes encoding type III secretion systems for virulence proteins. SPI1 is required for the penetration of the epithelial layer of the intestine. SPI2 is important for the subsequent proliferation of bacteria in the spleens of infected hosts. Although most mutations in SPI2 lead to a strong reduction of virulence, they have different effects in vitro, with some mutants having significantly increased sensitivity to gentamicin and the antibacterial peptide polymyxin B. Previously we showed that certain mutations in SPI2 affect the ability of S. typhimurium to secrete SPI1 effector proteins and to invade cultured eukaryotic cells. In this study, we show that these SPI2 mutations affect the expression of the SPI1 invasion genes. Analysis of reporter fusions to various SPI1 genes reveals highly reduced expression of sipC,prgK, and hilA, the transcriptional activator of SPI1 genes. These observations indicate that the expression of one type III secretion system can be influenced dramatically by mutations in genes encoding a second type III secretion system in the same cell.

scholarly journals Brucella abortus Rough Mutants Are Cytopathic for Macrophages in Culture

2004 ◽  
Vol 72 (1) ◽  
pp. 440-450 ◽  
Author(s):  
Jianwu Pei ◽  
Thomas A. Ficht
Keyword(s):  
Brucella Abortus ◽  
Cytopathic Effect ◽  
Apoptotic Cell ◽  
Morphological Changes ◽  
Annexin V ◽  
Intracellular Survival ◽  
Intracellular Killing ◽  
Vitro Assay ◽  
O Antigen

ABSTRACT Rough mutants of Brucella spp. are attenuated for survival in animal models. However, conflicting in vitro evidence has been obtained concerning the intracellular survival of rough mutants. Transposon-derived rough mutants isolated in our laboratory were previously shown to exhibit small but significant reductions in intracellular survival in a 12-h in vitro assay. Several recent publications report that rough mutants exhibited increased macrophage uptake relative to their smooth parental strains, and a reduction in numbers at the end of the assay has been interpreted as intracellular killing. In an effort to explore the role of O antigen in the interaction between Brucella abortus and macrophages, we have monitored the uptake of rough mutants and survival in vitro by using the murine macrophage cell line J774.A1. The results confirm a 10- to 20-fold-increased uptake of rough mutants over that of smooth organisms under standard conditions. Recovery of the rough mutants persisted up to 8 h postinfection, but at the point when intracellular replication of the smooth organisms was observed, the number of rough organisms recovered declined. Fluorescence microscopy revealed the intracellular multiplication of both smooth and rough organisms, and assays performed in the absence of antibiotic confirmed the replication of the rough organisms. Examination by phase-contrast microscopy revealed the lytic death of macrophages infected with the rough mutants, which was confirmed by the release of lactate dehydrogenase (LDH) from the cell cytoplasm. Thus, the decline in the number of rough organisms was the result of the lysis of macrophages and not from intracellular killing. The cytopathic effect is characterized as necrotic rather than apoptotic cell death based on early LDH release, annexin V and propidium iodide staining, morphological changes of infected cells and nuclei, and glycine protection. The cytopathic effect was observed with macrophages at multiplicities of infection (MOIs) of as low as 20 and was not observed with epithelial cells at MOIs of as high as 2000. These findings suggest a role for O antigen during the early stages of host-agent interaction that is essential in establishing an intracellular niche that maintains and supports persistent intracellular infection resulting in disease.

scholarly journals Casein Kinase 1 Delta Regulates the Pace of the Mammalian Circadian Clock

2009 ◽  
Vol 29 (14) ◽  
pp. 3853-3866 ◽  
Author(s):  
Jean-Pierre Etchegaray ◽  
Kazuhiko K. Machida ◽  
Elizabeth Noton ◽  
Cara M. Constance ◽  
Robert Dallmann ◽  
...  
Keyword(s):  
Circadian Clock ◽  
Perinatal Period ◽  
Casein Kinase ◽  
Gene Encoding ◽  
Exon 2 ◽  
Casein Kinase 1 ◽  
Functional Differences ◽  
Clock Proteins ◽  
Genes Encoding

ABSTRACT Both casein kinase 1 delta (CK1δ) and epsilon (CK1ε) phosphorylate core clock proteins of the mammalian circadian oscillator. To assess the roles of CK1δ and CK1ε in the circadian clock mechanism, we generated mice in which the genes encoding these proteins (Csnk1d and Csnk1e, respectively) could be disrupted using the Cre-loxP system. Cre-mediated excision of the floxed exon 2 from Csnk1d led to in-frame splicing and production of a deletion mutant protein (CK1δΔ2). This product is nonfunctional. Mice homozygous for the allele lacking exon 2 die in the perinatal period, so we generated mice with liver-specific disruption of CK1δ. In livers from these mice, daytime levels of nuclear PER proteins, and PER-CRY-CLOCK complexes were elevated. In vitro, the half-life of PER2 was increased by ∼20%, and the period of PER2::luciferase bioluminescence rhythms was 2 h longer than in controls. Fibroblast cultures from CK1δ-deficient embryos also had long-period rhythms. In contrast, disruption of the gene encoding CK1ε did not alter these circadian endpoints. These results reveal important functional differences between CK1δ and CK1ε: CK1δ plays an unexpectedly important role in maintaining the 24-h circadian cycle length.

scholarly journals Cloning and Sequence Analysis of a Highly Polymorphic Cryptosporidium parvum Gene Encoding a 60-Kilodalton Glycoprotein and Characterization of Its 15- and 45-Kilodalton Zoite Surface Antigen Products

2000 ◽  
Vol 68 (7) ◽  
pp. 4117-4134 ◽  
Author(s):  
William B. Strong ◽  
Jiri Gut ◽  
Richard G. Nelson
Keyword(s):  
Amino Acid ◽  
Sequence Analysis ◽  
Cryptosporidium Parvum ◽  
Diarrheal Disease ◽  
Surface Glycoprotein ◽  
Single Amino Acid ◽  
Gene Encoding ◽  
Single Nucleotide ◽  
Allelic Sequence

ABSTRACT The apicomplexan parasite Cryptosporidium parvum is a major cause of serious diarrheal disease in both humans and animals. No efficacious chemo- or immunotherapies have been identified for cryptosporidiosis, but certain antibodies directed against zoite surface antigens and/or proteins shed by gliding zoites have been shown to neutralize infectivity in vitro and/or to passively protect against, or ameliorate, disease in vivo. We previously used monoclonal antibody 11A5 to identify a 15-kDa surface glycoprotein that was shed behind motile sporozoites and was recognized by several lectins that neutralized parasite infectivity for cultured epithelial cells. Here we report the cloning and sequence analysis of the gene encoding this 11A5 antigen. Surprisingly, the gene encoded a 330-amino-acid, mucin-like glycoprotein that was predicted to contain an N-terminal signal peptide, a homopolymeric tract of serine residues, 36 sites of O-linked glycosylation, and a hydrophobic C-terminal peptide specifying attachment of a glycosylphosphatidylinositol anchor. The single-copy gene lacked introns and was expressed during merogony to produce a 60-kDa precursor which was proteolytically cleaved to 15- and 45-kDa glycoprotein products that both localized to the surface of sporozoites and merozoites. The gp15/45/60 gene displayed a very high degree of sequence diversity among C. parvumisolates, and the numerous single-nucleotide and single-amino-acid polymorphisms defined five to six allelic classes, each characterized by additional intra-allelic sequence variation. The gp15/45/60 single-nucleotide polymorphisms will prove useful for haplotyping and fingerprinting isolates and for establishing meaningful relationships between C. parvum genotype and phenotype.

scholarly journals O-Antigen-Negative Salmonella enterica Serovar Typhimurium Is Attenuated in Intestinal Colonization but Elicits Colitis in Streptomycin-Treated Mice

2009 ◽  
Vol 77 (6) ◽  
pp. 2568-2575 ◽  
Author(s):  
Karin Ilg ◽  
Kathrin Endt ◽  
Benjamin Misselwitz ◽  
Bärbel Stecher ◽  
Markus Aebi ◽  
...  
Keyword(s):  
Salmonella Enterica ◽  
Salmonella Enterica Serovar Typhimurium ◽  
Intestinal Inflammation ◽  
Polymyxin B ◽  
Major Constituent ◽  
O Antigen ◽  
Peptide Mimic ◽  
Serovar Typhimurium ◽  
Important Virulence Factor

ABSTRACT Lipopolysaccharide (LPS) is a major constituent of the outer membrane and an important virulence factor of Salmonella enterica subspecies 1 serovar Typhimurium (serovar Typhimurium). To evaluate the role of LPS in eliciting intestinal inflammation in streptomycin-treated mice, we constructed an O-antigen-deficient serovar Typhimurium strain through deletion of the wbaP gene. The resulting strain was highly susceptible to human complement activity and the antimicrobial peptide mimic polymyxin B. Furthermore, it showed a severe defect in motility and an attenuated phenotype in a competitive mouse infection experiment, where the ΔwbaP strain (SKI12) was directly compared to wild-type Salmonella. Nevertheless, the ΔwbaP strain (SKI12) efficiently invaded HeLa cells in vitro and elicited acute intestinal inflammation in streptomycin-pretreated mice. Our experiments prove that the presence of complete LPS is not essential for in vitro invasion or for triggering acute colitis.

scholarly journals In vitro activity of ceftazidime/avibactam against isolates of carbapenem-non-susceptible Enterobacteriaceae collected during the INFORM global surveillance programme (2015–17)

2019 ◽  
Vol 75 (2) ◽  
pp. 384-391 ◽  
Author(s):  
Iris Spiliopoulou ◽  
Krystyna Kazmierczak ◽  
Gregory G Stone
Keyword(s):  
Antimicrobial Activity ◽  
In Vitro Activity ◽  
Broth Microdilution ◽  
Gene Encoding ◽  
Surveillance Programme ◽  
Genes Encoding ◽  
The Usa ◽  
Report Data ◽  
Pcr Assays

Abstract Objectives To report data for ceftazidime/avibactam and comparators against meropenem-non-susceptible Enterobacteriaceae collected globally (excluding centres in the USA) from 2015 to 2017 as part of the International Network For Optimal Resistance Monitoring (INFORM) surveillance programme. Methods MICs and susceptibility were determined using EUCAST broth microdilution methodology and EUCAST breakpoints. Isolates were screened to detect genes encoding β-lactamases using multiplex PCR assays. MBL-positive isolates were those in which one or more of the IMP, VIM and/or NDM genes were detected. Results A total of 1460 meropenem-non-susceptible isolates were collected and, of the agents on the panel, susceptibility was highest to ceftazidime/avibactam, colistin and tigecycline [73.0%, 77.0% (1081/1403) and 78.1%, respectively]. Ceftazidime/avibactam was not active against MBL-positive isolates (n=367); these isolates showed the highest rates of susceptibility to colistin (92.1%, 303/329), tigecycline (71.9%) and amikacin (46.6%). A total of 394 isolates were resistant to ceftazidime/avibactam and, of the 369 isolates that were screened, 98.4% were found to carry a gene encoding an MBL enzyme. Among isolates that were identified as carbapenemase positive and MBL negative (n=910), susceptibility was highest to ceftazidime/avibactam (99.8%). Susceptibility was also highest to ceftazidime/avibactam among isolates that were carbapenemase negative and MBL negative (94/98, 95.9%). Conclusions These data highlight the need for continued surveillance of antimicrobial activity as well as the need for new antimicrobials to treat infections caused by meropenem-non-susceptible Enterobacteriaceae, for which the options are extremely limited.

scholarly journals Complementation of Brucella abortus RB51 with a Functional wboA Gene Results in O-Antigen Synthesis and Enhanced Vaccine Efficacy but No Change in Rough Phenotype and Attenuation

2000 ◽  
Vol 68 (7) ◽  
pp. 3927-3932 ◽  
Author(s):  
Ramesh Vemulapalli ◽  
Yongqun He ◽  
Larissa S. Buccolo ◽  
Stephen M. Boyle ◽  
Nammalwar Sriranganathan ◽  
...  
Keyword(s):  
Brucella Abortus ◽  
Brucella Melitensis ◽  
Virulent Strain ◽  
Polymyxin B ◽  
Gamma Interferon ◽  
T Cell Response ◽  
Bacterial Cells ◽  
O Antigen

ABSTRACT Brucella abortus RB51 is a stable rough, attenuated mutant vaccine strain derived from the virulent strain 2308. Recently, we demonstrated that the wboA gene in RB51 is disrupted by an IS711 element (R. Vemulapalli, J. R. McQuiston, G. G. Schurig, N. Srirauganathan, S. M. Halling, and S. M. Boyle, Clin. Diagn. Lab. Immunol. 6:760–764, 1999). Disruption of the wboA gene in smooth, virulent B. abortus, Brucella melitensis, and Brucella suis results in rough, attenuated mutants which fail to produce the O polysaccharide (O antigen). In this study, we explored whether the wboA gene disruption is responsible for the rough phenotype of RB51. We complemented RB51 with a functionalwboA gene, and the resulting strain was designated RB51WboA. Colony and Western blot analyses indicated that RB51WboA expressed the O antigen; immunoelectron microscopy revealed that the O antigen was present in the cytoplasm. Crystal violet staining, acryflavin agglutination, and polymyxin B sensitivity studies indicated that RB51WboA had rough phenotypic characteristics similar to those of RB51. Bacterial clearance studies of BALB/c mice indicated no increase in the survival ability of RB51WboA in vivo compared to that of RB51. Vaccination of mice with live RB51WboA induced antibodies to the O antigen which were predominantly of the immunoglobulin G2a (IgG2a) and IgG3 isotypes. After in vitro stimulation of splenocytes with killed bacterial cells, quantitation of gamma interferon in the culture supernatants indicated that RB51WboA immunization induced higher levels of gamma interferon than immunization with RB51. Mice vaccinated with RB51WboA were better protected against a challenge infection with the virulent strain 2308 than those vaccinated with RB51. These studies indicate that in addition to the disruption of the wboAgene there is at least one other mutation in RB51 responsible for its rough phenotype. These studies also suggest that the expressed O antigen in RB51WboA is responsible either directly or indirectly for the observed enhancement in the T-cell response.

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