scholarly journals The lipopolysaccharide outer core transferase genes pcgD and hptE contribute differently to the virulence of Pasteurella multocida in ducks

2021 ◽  
Vol 52 (1) ◽  
Author(s):  
Xinxin Zhao ◽  
Hui Shen ◽  
Sheng Liang ◽  
Dekang Zhu ◽  
Mingshu Wang ◽  
...  
Keyword(s):  
Membrane Permeability ◽  
Outer Membrane ◽  
Type Strain ◽  
Pasteurella Multocida ◽  
Wild Type Strain ◽  
Outer Core ◽  
High Dose ◽  
Wild Type ◽  
Virulence Attenuation ◽  
Outer Membrane Permeability

AbstractFowl cholera caused by Pasteurella multocida exerts a massive economic burden on the poultry industry. Lipopolysaccharide (LPS) is essential for the growth of P. multocida genotype L1 strains in chickens and specific truncations to the full length LPS structure can attenuate bacterial virulence. Here we further dissected the roles of the outer core transferase genes pcgD and hptE in bacterial resistance to duck serum, outer membrane permeability and virulence in ducks. Two P. multocida mutants, ΔpcgD and ΔhptE, were constructed, and silver staining confirmed that they all produced truncated LPS profiles. Inactivation of pcgD or hptE did not affect bacterial susceptibility to duck serum and outer membrane permeability but resulted in attenuated virulence in ducks to some extent. After high-dose inoculation, ΔpcgD showed remarkably reduced colonization levels in the blood and spleen but not in the lung and liver and caused decreased injuries in the spleen and liver compared with the wild-type strain. In contrast, the ΔhptE loads declined only in the blood, and ΔhptE infection caused decreased splenic lesions but also induced severe hepatic lesions. Furthermore, compared with the wild-type strain, ΔpcgD was significantly attenuated upon oral or intramuscular challenge, whereas ΔhptE exhibited reduced virulence only upon oral infection. Therefore, the pcgD deletion caused greater virulence attenuation in ducks, indicating the critical role of pcgD in P. multocida infection establishment and survival.

scholarly journals The role of Zur-regulated lipoprotein A in bacterial morphology, antimicrobial susceptibility, and production of outer membrane vesicles in Acinetobacter baumannii

2021 ◽  
Vol 21 (1) ◽  
Author(s):  
Nayeong Kim ◽  
Hyo Jeong Kim ◽  
Man Hwan Oh ◽  
Se Yeon Kim ◽  
Mi Hyun Kim ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Outer Membrane ◽  
Mutant Strain ◽  
Antimicrobial Susceptibility ◽  
Type Strain ◽  
Wild Type Strain ◽  
Membrane Vesicles ◽  
Outer Membrane Vesicles ◽  
Wild Type ◽  
Bacterial Morphology

Abstract Background Zinc uptake-regulator (Zur)-regulated lipoprotein A (ZrlA) plays a role in bacterial fitness and overcoming antimicrobial exposure in Acinetobacter baumannii. This study further characterized the zrlA gene and its encoded protein and investigated the roles of the zrlA gene in bacterial morphology, antimicrobial susceptibility, and production of outer membrane vesicles (OMVs) in A. baumannii ATCC 17978. Results In silico and polymerase chain reaction analyses showed that the zrlA gene was conserved among A. baumannii strains with 97–100% sequence homology. Recombinant ZrlA protein exhibited a specific enzymatic activity of D-alanine-D-alanine carboxypeptidase. Wild-type A. baumannii exhibited more morphological heterogeneity than a ΔzrlA mutant strain during stationary phase. The ΔzrlA mutant strain was more susceptible to gentamicin than the wild-type strain. Sizes and protein profiles of OMVs were similar between the wild-type and ΔzrlA mutant strains, but the ΔzrlA mutant strain produced 9.7 times more OMV particles than the wild-type strain. OMVs from the ΔzrlA mutant were more cytotoxic in cultured epithelial cells than OMVs from the wild-type strain. Conclusions The present study demonstrated that A. baumannii ZrlA contributes to bacterial morphogenesis and antimicrobial resistance, but its deletion increases OMV production and OMV-mediated host cell cytotoxicity.

scholarly journals In VivoEfficacy of Human Simulated Regimens of Carbapenems and Comparator Agents against NDM-1-Producing Enterobacteriaceae

2013 ◽  
Vol 58 (3) ◽  
pp. 1671-1677 ◽  
Author(s):  
Dora E. Wiskirchen ◽  
Patrice Nordmann ◽  
Jared L. Crandon ◽  
David P. Nicolau
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Similar Efficacy ◽  
Infection Model ◽  
High Dose ◽  
Wild Type ◽  
Prolonged Infusion ◽  
Content Type

ABSTRACTDoripenem and ertapenem have demonstrated efficacy against several NDM-1-producing isolatesin vivo, despite having high MICs. In this study, we sought to further characterize the efficacy profiles of humanized regimens of standard (500 mg given every 8 h) and high-dose, prolonged infusion of doripenem (2 g given every 8 h, 4-h infusion) and 1 g of ertapenem given intravenously every 24 h and the comparator regimens of ceftazidime at 2 g given every 8 h (2-h infusion), levofloxacin at 500 mg every 24 h, and aztreonam at 2 g every 6 h (1-h infusion) against a wider range of isolates in a murine thigh infection model. An isogenic wild-type strain and NDM-1-producingKlebsiella pneumoniaeand eight clinical NDM-1-producing members of the familyEnterobacteriaceaewere tested in immunocompetent- and neutropenic-mouse models. The wild-type strain was susceptible to all of the agents, while the isogenic NDM-1-producing strain was resistant to ceftazidime, doripenem, and ertapenem. Clinical NDM-1-producing strains were resistant to nearly all five of the agents (two were susceptible to levofloxacin). In immunocompetent mice, all of the agents produced ≥1-log10CFU reductions of the isogenic wild-type and NDM-1-producing strains after 24 h. Minimal efficacy of ceftazidime, aztreonam, and levofloxacin against the clinical NDM-1-producing strains was observed. However, despitein vitroresistance, ≥1-log10CFU reductions of six of eight clinical strains were achieved with high-dose, prolonged infusion of doripenem and ertapenem. Slight enhancements of doripenem activity over the standard doses were obtained with high-dose, prolonged infusion for three of the four isolates tested. Similar efficacy observations were noted in neutropenic mice. These data suggest that carbapenems are a viable treatment option for infections caused by NDM-1-producingEnterobacteriaceae.

scholarly journals Oral Immunization with an rfaH Mutant Elicits Protection against Salmonellosis in Mice

2004 ◽  
Vol 72 (7) ◽  
pp. 4297-4301 ◽  
Author(s):  
Gábor Nagy ◽  
Ulrich Dobrindt ◽  
Jörg Hacker ◽  
Levente Emödy
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Lethal Dose ◽  
Fold Increase ◽  
Oral Immunization ◽  
Oral Infection ◽  
Wild Type ◽  
Virulence Attenuation ◽  
Serovar Typhimurium

ABSTRACT Loss of the transcriptional antiterminator RfaH results in virulence attenuation (>104-fold increase in 50% lethal dose) of the archetypal Salmonella enterica serovar Typhimurium strain SL1344 by both orogastric and intraperitoneal routes of infection in BALB/c mice. Oral immunization with the mutant efficiently protects mice against a subsequent oral infection with the wild-type strain. Interestingly, in vitro immunoreactivity is not confined to strain SL1344; rather, it is directed also towards other serovars of S. enterica and even Salmonella bongori strains.

scholarly journals Role of β-Lactamases and Porins in Resistance to Ertapenem and Other β-Lactams in Klebsiella pneumoniae

2004 ◽  
Vol 48 (8) ◽  
pp. 3203-3206 ◽  
Author(s):  
George A. Jacoby ◽  
Debra M. Mills ◽  
Nancy Chow
Keyword(s):  
Klebsiella Pneumoniae ◽  
Outer Membrane ◽  
Type Strain ◽  
Wild Type Strain ◽  
Outer Membrane Proteins ◽  
Wild Type ◽  
Resistant Mutants ◽  
High Level ◽  
Level Resistance

ABSTRACT High-level resistance to ertapenem was produced by β-lactamases of groups 1, 2f, and 3 in a strain of Klebsiella pneumoniae deficient in Omp35 and Omp36. From a wild-type strain producing ACT-1 β-lactamase, ertapenem-resistant mutants for which the ertapenem MICs were up to 128 μg/ml and expression of outer membrane proteins was diminished could be selected.

scholarly journals Role of aspartate ammonia-lyase in Pasteurella multocida

2020 ◽  
Vol 20 (1) ◽  
Author(s):  
Zui Wang ◽  
Li Li ◽  
Peng Liu ◽  
Chen Wang ◽  
Qin Lu ◽  
...  
Keyword(s):  
Mutant Strain ◽  
Bacterial Growth ◽  
Type Strain ◽  
Pasteurella Multocida ◽  
Wild Type Strain ◽  
Luria Bertani ◽  
Economic Losses ◽  
Wild Type ◽  
Mueller Hinton ◽  
Significant Difference

Abstract Background Pasteurella multocida is responsible for a highly infectious and contagious disease in birds, leading to heavy economic losses in the chicken industry. However, the pathogenesis of this disease is poorly understood. We recently identified an aspartate ammonia-lyase (aspA) in P. multocida that was significantly upregulated under iron-restricted conditions, the protein of which could effectively protect chicken flocks against P. multocida. However, the functions of this gene remain unclear. In the present study, we constructed aspA mutant strain △aspA::kan and complementary strain C△aspA::kan to investigate the function of aspA in detail. Result Deletion of the aspA gene in P. multocida resulted in a significant reduction in bacterial growth in LB (Luria-Bertani) and MH (Mueller-Hinton) media, which was rescued by supplementation with 20 mM fumarate. The mutant strain △aspA::kan showed significantly growth defects in anaerobic conditions and acid medium, compared with the wild-type strain. Moreover, growth of △aspA::kan was more seriously impaired than that of the wild-type strain under iron-restricted conditions, and this growth recovered after supplementation with iron ions. AspA transcription was negatively regulated by iron conditions, as demonstrated by quantitative reverse transcription-polymerase chain reaction. Although competitive index assay showed the wild-type strain outcompetes the aspA mutant strain and △aspA::kan was significantly more efficient at producing biofilms than the wild-type strain, there was no significant difference in virulence between the mutant and the wild-type strains. Conclusion These results demonstrate that aspA is required for bacterial growth in complex medium, and under anaerobic, acid, and iron-limited conditions.

scholarly journals Novel Toluene Elimination System in a Toluene-Tolerant Microorganism

2000 ◽  
Vol 182 (22) ◽  
pp. 6451-6455 ◽  
Author(s):  
Hideki Kobayashi ◽  
Katsuyuki Uematsu ◽  
Hisako Hirayama ◽  
Koki Horikoshi
Keyword(s):  
Membrane Proteins ◽  
Cell Membrane ◽  
Outer Membrane ◽  
Parent Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Outer Membrane Proteins ◽  
Membrane Vesicles ◽  
Wild Type ◽  
Sensitive Mutant

ABSTRACT In studies of Pseudomonas putida IH-2000, a toluene-tolerant microorganism, membrane vesicles (MVs) were found to be released from the outer membrane when toluene was added to the culture. These MVs were found to be composed of phospholipids, lipopolysaccharides (LPS), and very low amounts of outer membrane proteins. The MVs also contained a higher concentration of toluene molecules (0.172 ± 0.012 mol/mol of lipid) than that found in the cell membrane. In contrast to the wild-type strain, the toluene-sensitive mutant strain 32, which differs from the parent strain in LPS and outer membrane proteins, did not release MVs from the outer membrane. The toluene molecules adhering to the outer membrane are eliminated by the shedding of MVs, and this system appears to serve as an important part of the toluene tolerance system of IH-2000.

scholarly journals OpnS, an Outer Membrane Porin of Xenorhabdus nematophila, Confers a Competitive Advantage for Growth in the Insect Host

2009 ◽  
Vol 191 (17) ◽  
pp. 5471-5479 ◽  
Author(s):  
Ransome van der Hoeven ◽  
Steven Forst
Keyword(s):  
Competitive Advantage ◽  
Outer Membrane ◽  
Type Strain ◽  
Wild Type Strain ◽  
Entomopathogenic Nematode ◽  
Growth Defect ◽  
Insect Host ◽  
Xenorhabdus Nematophila ◽  
Wild Type ◽  
Defined Culture

ABSTRACT The gammaproteobacterium Xenorhabdus nematophila engages in a mutualistic association with an entomopathogenic nematode and also functions as a pathogen toward different insect hosts. We studied the role of the growth-phase-regulated outer membrane protein OpnS in host interactions. OpnS was shown to be a 16-stranded β-barrel porin. opnS was expressed during growth in insect hemolymph and expression was elevated as the cell density increased. When wild-type and opnS deletion strains were coinjected into insects, the wild-type strain was predominantly recovered from the insect cadaver. Similarly, an opnS-complemented strain outcompeted the ΔopnS strain. Coinjection of the wild-type and ΔopnS strains together with uncolonized nematodes into insects resulted in nematode progeny that were almost exclusively colonized with the wild-type strain. Likewise, nematode progeny recovered after coinjection of a mixture of nematodes carrying either the wild-type or ΔopnS strain were colonized by the wild-type strain. In addition, the ΔopnS strain displayed a competitive growth defect when grown together with the wild-type strain in insect hemolymph but not in defined culture medium. The ΔopnS strain displayed increased sensitivity to antimicrobial compounds, suggesting that deletion of OpnS affected the integrity of the outer membrane. These findings show that the OpnS porin confers a competitive advantage for the growth and/or the survival of X. nematophila in the insect host and provides a new model for studying the biological relevance of differential regulation of porins in a natural host environment.

scholarly journals Leptospira interrogans lpxDHomologue Is Required for Thermal Acclimatization and Virulence

2015 ◽  
Vol 83 (11) ◽  
pp. 4314-4321 ◽  
Author(s):  
Azad Eshghi ◽  
Jeremy Henderson ◽  
M. Stephen Trent ◽  
Mathieu Picardeau
Keyword(s):  
Outer Membrane ◽  
Type Strain ◽  
Lipid A ◽  
Wild Type Strain ◽  
Infection Model ◽  
Leptospira Interrogans ◽  
Wild Type ◽  
Content Type ◽  
Physiological Temperature ◽  
Animal Infection

ABSTRACTLeptospirosis is an emerging disease with an annual occurrence of over 1 million human cases worldwide. PathogenicLeptospirabacteria are maintained in zoonotic cycles involving a diverse array of mammals, with the capacity to survive outside the host in aquatic environments. Survival in the diverse environments encountered byLeptospiralikely requires various adaptive mechanisms. Little is known aboutLeptospiraouter membrane modification systems, which may contribute to the capacity of these bacteria to successfully inhabit and colonize diverse environments and animal hosts.Leptospirabacteria carry two genes annotated as UDP-3-O-[3-hydroxymyristoyl] glucosamineN-acyltransferase genes (la0512 and la4326 [lpxD1andlpxD2]) that in other bacteria are involved in the early steps of biosynthesis of lipid A, the membrane lipid anchor of lipopolysaccharide. Inactivation of only one of these genes, la0512/lpxD1, imparted sensitivity to the host physiological temperature (37°C) and rendered the bacteria avirulent in an animal infection model. Polymyxin B sensitivity assays revealed compromised outer membrane integrity in thelpxD1mutant at host physiological temperature, but structural analysis of lipid A in the mutant revealed only minor changes in the lipid A moiety compared to that found in the wild-type strain. In accordance with this, anin transcomplementation restored the phenotypes to a level comparable to that of the wild-type strain. These results suggest that the gene annotated aslpxD1inLeptospira interrogansplays an important role in temperature adaptation and virulence in the animal infection model.

scholarly journals Role of vimA in cell surface biogenesis in Porphyromonas gingivalis

Microbiology ◽  
2010 ◽  
Vol 156 (7) ◽  
pp. 2180-2193 ◽  
Author(s):  
Devon O. Osbourne ◽  
Wilson Aruni ◽  
Francis Roy ◽  
Christopher Perry ◽  
Lawrence Sandberg ◽  
...  
Keyword(s):  
Cell Surface ◽  
Outer Membrane ◽  
Porphyromonas Gingivalis ◽  
Type Strain ◽  
Wild Type Strain ◽  
Phenotypic Expression ◽  
Surface Proteins ◽  
Wild Type ◽  
In The Wild

The Porphyromonas gingivalis vimA gene has been previously shown to play a significant role in the biogenesis of gingipains. Further, in P. gingivalis FLL92, a vimA-defective mutant, there was increased auto-aggregation, suggesting alteration in membrane surface proteins. In order to determine the role of the VimA protein in cell surface biogenesis, the surface morphology of P. gingivalis FLL92 was further characterized. Transmission electron microscopy demonstrated abundant fimbrial appendages and a less well defined and irregular capsule in FLL92 compared with the wild-type. In addition, atomic force microscopy showed that the wild-type had a smoother surface compared with FLL92. Western blot analysis using anti-FimA antibodies showed a 41 kDa immunoreactive protein band in P. gingivalis FLL92 which was missing in the wild-type P. gingivalis W83 strain. There was increased sensitivity to globomycin and vancomycin in FLL92 compared with the wild-type. Outer membrane fractions from FLL92 had a modified lectin-binding profile. Furthermore, in contrast with the wild-type strain, nine proteins were missing from the outer membrane fraction of FLL92, while 20 proteins present in that fraction from FLL92 were missing in the wild-type strain. Taken together, these results suggest that the VimA protein affects capsular synthesis and fimbrial phenotypic expression, and plays a role in the glycosylation and anchorage of several surface proteins.

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