scholarly journals The Role of graRS in Regulating Virulence and Antimicrobial Resistance in Methicillin-Resistant Staphylococcus aureus

2021 ◽  
Vol 12 ◽  
Author(s):  
Le Chen ◽  
Zihui Wang ◽  
Tao Xu ◽  
Hongfei Ge ◽  
Fangyue Zhou ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Type Strain ◽  
Bacterial Resistance ◽  
Wild Type Strain ◽  
Lysine Biosynthesis ◽  
Infection Model ◽  
Wild Type ◽  
Methicillin Resistant

Methicillin-resistant Staphylococcus aureus (MRSA) is a common cause of both community- and hospital-associated infections. The antibiotic resistance and virulence characteristics of MRSA are largely regulated by two-component signal transduction systems (TCS) including the graRS TCS. To make a relatively comprehensive insight into graRS TCS in MRSA, the bioinformatics analysis of dataset GSE26016 (a S. aureus HG001 WT strain vs. the ΔgraRS mutant) from Gene Expression Omnibus (GEO) database was performed, and a total of 563 differentially expressed genes (DEGs) were identified. GO analysis revealed that the DEGs were mainly enriched in the “de novo” IMP biosynthetic process, lysine biosynthetic process via diaminopimelate, and pathogenesis; and they were mainly enriched in purine metabolism, lysine biosynthesis, and monobactam biosynthesis in KEGG analysis. WGCNA suggested that the turquoise module was related to the blue module, and the genes in these two modules were associated with S. aureus virulence and infection. To investigate the role of graRS in bacterial virulence, a graRS knockout mutant (ΔgraRS) was constructed using MRSA USA500 2,395 strain as a parent strain. Compared to the wild-type strain, the USA500ΔgraRS showed reduced staphyloxanthin production, retarded coagulation, weaker hemolysis on blood agar plates, and a decreased biofilm formation. These altered phenotypes were restored by the complementation of a plasmid-expressed graRS. Meanwhile, an expression of the virulence-associated genes (coa, hla, hlb, agrA, and mgrA) was downregulated in the ΔgraRS mutant. Consistently, the A549 epithelial cells invasion of the ΔgraRS mutant was 4-fold lower than that of the USA500 wild-type strain. Moreover, on the Galleria mellonella infection model, the survival rate at day 5 post infection in the USA500ΔgraRS group (55%) was obviously higher than that in the USA500 group (20%), indicating graRS knockout leads to a decreased virulence in vivo. In addition, the deletion of the graRS in the MRSA USA500 strain resulted in its increased susceptibilities to ampicillin, oxacillin, vancomycin, and gentamicin. Our work suggests that the graRS TCS plays an important role in regulating S. aureus virulence in vitro and in vivo and modulate bacterial resistance to various antibiotics.

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 Discovery of Brominated Alboflavusins With Anti-MRSA Activities

2021 ◽  
Vol 12 ◽  
Author(s):  
Chao Li ◽  
Wuyundalai Bao ◽  
Haoyue Zhang ◽  
Zhitang Lyu ◽  
Yihua Chen ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Human Health ◽  
Type Strain ◽  
Wild Type Strain ◽  
Production Medium ◽  
Wild Type ◽  
Methicillin Resistant ◽  
New Antibiotics ◽  
Mrsa Strains ◽  
New Compounds

As methicillin-resistant Staphylococcus aureus (MRSA) is becoming a serious pathogenic threaten to human health worldwide, there is an urgent need to discover new antibiotics for the treatment of MRSA infections. Alboflavusins (AFNs) are a group of halogenated cyclohexapeptides with anti-MRSA activities. In this study, two novel brominated AFN congeners (compounds 1 and 2) were isolated from the wild-type strain Streptomyces alboflavus sp. 313 that was fermented in the production medium supplemented with NaBr; two new (compounds 3 and 5) and a known (compound 4) dehelogenated AFN congeners were isolated from S. alboflavus ΔafnX, in which the tryptophan halogenase gene afnX was inactivated. The structures of these compounds were assigned by careful NMR and MS analyses. The anti-MRSA activities of varied AFN congeners were assessed against different MRSA strains, which revealed that compounds 1 and 2 with bromine displayed effective activities against the tested MRSA strains. Especially, compound 2 showed good anti-MRSA activity, while compounds 3, 4, and 5 without halogen exhibited weak anti-MRSA activities, outlining the influence of halogen substitution to the bioactivities of AFNs.

scholarly journals The RNA Chaperone Hfq Promotes Fitness of Actinobacillus pleuropneumoniae during Porcine Pleuropneumonia

2013 ◽  
Vol 81 (8) ◽  
pp. 2952-2961 ◽  
Author(s):  
Sargurunathan Subashchandrabose ◽  
Rhiannon M. Leveque ◽  
Roy N. Kirkwood ◽  
Matti Kiupel ◽  
Martha H. Mulks
Keyword(s):  
Biofilm Formation ◽  
Type Strain ◽  
Wild Type Strain ◽  
Actinobacillus Pleuropneumoniae ◽  
Wild Type ◽  
Content Type ◽  
Porcine Pleuropneumonia ◽  
Porcine Lungs

ABSTRACTActinobacillus pleuropneumoniaeis the etiological agent of porcine pleuropneumonia, an economically important disease of pigs. Thehfqgene inA. pleuropneumoniae, encoding the RNA chaperone and posttranscriptional regulator Hfq, is upregulated during infection of porcine lungs. To investigate the role of thisin vivo-induced gene inA. pleuropneumoniae, anhfqmutant strain was constructed. Thehfqmutant was defective in biofilm formation on abiotic surfaces. The level ofpgaCtranscript, encoding the biosynthesis of poly-β-1,6-N-acetylglucosamine (PNAG), a major biofilm matrix component, was lower and PNAG content was 10-fold lower in thehfqmutant than in the wild-type strain. When outer membrane proteins were examined, cysteine synthase, implicated in resistance to oxidative stress and tellurite, was not found at detectable levels in the absence of Hfq. Thehfqmutant displayed enhanced sensitivity to superoxide generated by methyl viologen and tellurite. These phenotypes were readily reversed by complementation with thehfqgene expressed from its native promoter. The role of Hfq in the fitness ofA. pleuropneumoniaewas assessed in a natural host infection model. Thehfqmutant failed to colonize porcine lungs and was outcompeted by the wild-type strain (median competitive index of 2 × 10−5). Our data demonstrate that thein vivo-induced genehfqis involved in the regulation of PNAG-dependent biofilm formation, resistance to superoxide stress, and the fitness and virulence ofA. pleuropneumoniaein pigs and begin to elucidate the role of anin vivo-induced gene in the pathogenesis of pleuropneumonia.

scholarly journals Role of Mrx Fimbriae of Xenorhabdus nematophila in Competitive Colonization of the Nematode Host

2011 ◽  
Vol 77 (20) ◽  
pp. 7247-7254 ◽  
Author(s):  
Holly Snyder ◽  
Hongjun He ◽  
Heather Owen ◽  
Chris Hanna ◽  
Steven Forst
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Infective Juvenile ◽  
Xenorhabdus Nematophila ◽  
Wild Type ◽  
Content Type ◽  
Mutant Strains ◽  
Phenotypic Variant

ABSTRACTXenorhabdus nematophilaengages in mutualistic associations with the infective juvenile (IJ) stage of specific entomopathogenic nematodes. Mannose-resistant (Mrx) chaperone-usher-type fimbriae are produced when the bacteria are grown on nutrient broth agar (NB agar). The role of Mrx fimbriae in the colonization of the nematode host has remained unresolved. We show thatX. nematophilagrown on LB agar produced flagella rather than fimbriae. IJs propagated onX. nematophilagrown on LB agar were colonized to the same extent as those propagated on NB agar. Further, progeny IJs were normally colonized bymrxmutant strains that lacked fimbriae both when bacteria were grown on NB agar and when coinjected into the insect host with aposymbiotic nematodes. Themrxstrains were not competitively defective for colonization when grown in the presence of wild-type cells on NB agar. In addition, a phenotypic variant strain that lacked fimbriae colonized as well as the wild-type strain. In contrast, themrxstrains displayed a competitive colonization defectin vivo. IJ progeny obtained from insects injected with comixtures of nematodes carrying either the wild-type or themrxstrain were colonized almost exclusively with the wild-type strain. Likewise, when insects were coinjected with aposymbiotic IJs together with a comixture of the wild-type andmrxstrains, the resulting IJ progeny were predominantly colonized with the wild-type strain. These results revealed that Mrx fimbriae confer a competitive advantage during colonizationin vivoand provide new insights into the role of chaperone-usher fimbriae in the life cycle ofX. nematophila.

scholarly journals Detailed In Vivo Analysis of the Role of Helicobacter pylori Fur in Colonization and Disease

2010 ◽  
Vol 78 (7) ◽  
pp. 3073-3082 ◽  
Author(s):  
Shana Miles ◽  
M. Blanca Piazuelo ◽  
Cristina Semino-Mora ◽  
Mary Kay Washington ◽  
Andre Dubois ◽  
...  
Keyword(s):  
Helicobacter Pylori ◽  
Mongolian Gerbil ◽  
Type Strain ◽  
Wild Type Strain ◽  
Temporal Analysis ◽  
Wild Type ◽  
Invasive Adenocarcinoma ◽  
H Pylori

ABSTRACT Helicobacter pylori persistently colonizes the harsh and dynamic environment of the stomach in over one-half of the world's population and has been identified as a causal agent in a spectrum of pathologies that range from gastritis to invasive adenocarcinoma. The ferric uptake regulator (Fur) is one of the few regulatory proteins that has been identified in H. pylori. Fur regulates genes important for acid acclimation and oxidative stress and has been shown to be important for colonization of H. pylori in both murine and Mongolian gerbil models of infection. To more thoroughly define the role of Fur in vivo, we conducted an extensive temporal analysis of the location of, competitive ability of, and resultant pathology induced by a Δfur strain in the Mongolian gerbil model of infection and compared the results to results for its wild-type parent. We found that at the earliest time points postinfection, significantly more Δfur bacteria than wild-type bacteria were recovered. However, this trend was reversed by day 3, when there was significantly increased recovery of the wild-type strain. The increased recovery of the Δfur strain at 1 day postinfection reflected increased recovery from both the corpus and the antrum of the stomach. When the wild-type strain was allowed to colonize first, the Δfur strain was unable to compete for colonization at any time postinfection. However, when the Δfur strain was allowed to colonize first, the wild type efficiently outcompeted the Δfur strain only at early times postinfection. Finally, we demonstrated that there was a delay in the development and severity of inflammation and pathology of the Δfur strain in the gastric mucosa even after comparable levels of colonization occurred. Together, these data indicate that H. pylori Fur is most important at early stages of infection and illustrate the importance of the ability of H. pylori to adapt to its constantly fluctuating environment when it is establishing infection, inflammation, and disease.

scholarly journals Bactericidal Activities of BMS-284756, a Novel Des-F(6)-Quinolone, against Staphylococcus aureus Strains with Topoisomerase Mutations

2002 ◽  
Vol 46 (1) ◽  
pp. 191-195 ◽  
Author(s):  
Laura E. Lawrence ◽  
MaryBeth Frosco ◽  
Brenda Ryan ◽  
Susan Chaniewski ◽  
Hyekyung Yang ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Type Strain ◽  
Wild Type Strain ◽  
Wild Type ◽  
In Vivo Efficacy ◽  
Mutant Strains ◽  
Bactericidal Activities ◽  
Time Kill

ABSTRACT The antistaphylococcal activities of BMS-284756 (T-3811ME), levofloxacin, moxifloxacin, and ciprofloxacin were compared against wild-type and grlA and grlA/gyrA mutant strains of Staphylococcus aureus. BMS-284756 was the most active quinolone tested, with MICs and minimal bactericidal concentrations against S. aureus wild-type strain MT5, grlA mutant MT5224c4, and grlA/gyrA mutant EN8 of 0.03 and 0.06, 0.125 and 0.125, and 4 and 4 μg/ml, respectively. In the time-kill studies, BMS-284756 and levofloxacin exhibited rapid killing against all strains. Ciprofloxacin, however, was not bactericidal for the double mutant, EN8. BMS-284756 and levofloxacin were bactericidal (3 log10 decrease in CFU/ml) against the MT5 and MT5224c4 strains at two and four times the MIC within 2 to 4 h. Against EN8, BMS-284756 was bactericidal within 4 h at two and four times the MIC, and levofloxacin achieved similar results within 4 to 6 h. Both the wild-type strain MT5 and grlA mutant MT5224c4 should be considered susceptible to both BMS-284756 and levofloxacin, and both quinolones are predicted to have clinical efficacy. The in vivo efficacy of BMS-284756, levofloxacin, and moxifloxacin against S. aureus strain ISP794 and its single mutant 2C6(1)-1 directly reflected the in vitro activity: increased MICs correlated with decreased in vivo efficacy. The 50% protective doses of BMS-284756 against wild-type and mutant strains were 2.2 and 1.6 mg/kg of body weight/day, respectively, compared to the levofloxacin values of 16 and 71 mg/kg/day and moxifloxacin values of 4.7 and 61.6 mg/kg/day. BMS-284756 was more potent than levofloxacin and equipotent with moxifloxacin against ISP794 both in vitro and in vivo, while BMS-284756 was more potent than levofloxacin and moxifloxacin against 2C6(1)-1.

Low-proline environments impair growth, proline transport and in vivo survival of Staphylococcus aureus strain-specific putP mutants

Microbiology ◽  
2004 ◽  
Vol 150 (4) ◽  
pp. 1055-1061 ◽  
Author(s):  
William R. Schwan ◽  
Keith J. Wetzel ◽  
Timothy S. Gomez ◽  
Melissa A. Stiles ◽  
Brian D. Beitlich ◽  
...  
Keyword(s):  
Staphylococcus Aureus ◽  
Mutant Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Aureus Strain ◽  
Insertion Mutation ◽  
Wild Type ◽  
Proline Transport ◽  
High Affinity

Staphylococcus aureus is a common cause of disease in humans, particularly in hospitalized patients. This species needs to import several amino acids to survive, including proline. Previously, it was shown that an insertion mutation in the high-affinity proline uptake gene putP in strain RN6390 affected proline uptake by the bacteria as well as reducing their ability to survive in vivo. To further delineate the effect of the putP mutation on growth of S. aureus strain RN6390, a proline uptake assay that spanned less than 1 min was done to measure transport. An eightfold difference in proline levels was observed between the wild-type strain and the high-affinity proline transport mutant strain after 15 s, indicating that the defect was only in proline transport and not a combination of proline transport, metabolism and accumulation that would have been assessed with longer assays. A putP mutant of S. aureus strain RN4220 was then grown in minimal medium with different concentrations of proline. When compared to the wild-type strain, the putP mutant strain was significantly growth impaired when the level of proline was decreased to 1·74 μM. An assessment of proline concentrations in mouse livers and spleens showed proline concentrations of 7·5 μmol per spleen and 88·4 μmol per liver. To verify that the effects on proline transport and bacterial survival were indeed caused solely by a mutation in putP, the putP mutation was complemented by cloning a full-length putP gene on a plasmid that replicates in S. aureus. Complementation of the putP mutant strains restored proline transport, in vitro growth in low-proline medium, and in vivo survival within mice. These results show that the mutation in putP led to attenuated growth in low-proline media and by corollary low-proline murine organ tissues due to less efficient transport of proline into the bacteria.

scholarly journals Critical Role of LuxS in the Virulence of Campylobacter jejuni in a Guinea Pig Model of Abortion

2011 ◽  
Vol 80 (2) ◽  
pp. 585-593 ◽  
Author(s):  
Paul Plummer ◽  
Orhan Sahin ◽  
Eric Burrough ◽  
Rachel Sippy ◽  
Kathy Mou ◽  
...  
Keyword(s):  
Guinea Pig ◽  
Campylobacter Jejuni ◽  
Type Strain ◽  
Wild Type Strain ◽  
Critical Role ◽  
Wild Type ◽  
Direct Role ◽  
Content Type

ABSTRACTPrevious studies onCampylobacter jejunihave demonstrated the role of LuxS in motility, cytolethal distending toxin production, agglutination, and intestinal colonization; however, its direct involvement in virulence has not been reported. In this study, we demonstrate a direct role ofluxSin the virulence ofC. jejuniin two different animal hosts. The IA3902 strain, a highly virulent sheep abortion strain recently described by our laboratory, along with its isogenicluxSmutant andluxScomplement strains, was inoculated by the oral route into both a pregnant guinea pig virulence model and a chicken colonization model. In both cases, the IA3902luxSmutant demonstrated a complete loss of ability to colonize the intestinal tract. In the pregnant model, the mutant also failed to induce abortion, while the wild-type strain was highly abortifacient. Genetic complementation of theluxSgene fully restored the virulent phenotype in both models. Interestingly, when the organism was inoculated into guinea pigs by the intraperitoneal route, no difference in virulence (abortion induction) was observed between theluxSmutant and the wild-type strain, suggesting that the defect in virulence following oral inoculation is likely associated with a defect in colonization and/or translocation of the organism out of the intestine. These studies provide the first direct evidence that LuxS plays an important role in the virulence ofC. jejuniusing anin vivomodel of natural disease.

scholarly journals Effect of rpoS Mutation on the Stress Response and Expression of Virulence Factors in Pseudomonas aeruginosa

1999 ◽  
Vol 181 (13) ◽  
pp. 3890-3897 ◽  
Author(s):  
Sang-Jin Suh ◽  
Laura Silo-Suh ◽  
Donald E. Woods ◽  
Daniel J. Hassett ◽  
Susan E. H. West ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Stress Response ◽  
Parent Strain ◽  
Type Strain ◽  
Wild Type Strain ◽  
Infection Model ◽  
Gram Negative Bacteria ◽  
Wild Type ◽  
Gram Negative

ABSTRACT The sigma factor RpoS (ςS) has been described as a general stress response regulator that controls the expression of genes which confer increased resistance to various stresses in some gram-negative bacteria. To elucidate the role of RpoS inPseudomonas aeruginosa physiology and pathogenesis, we constructed rpoS mutants in several strains of P. aeruginosa, including PAO1. The PAO1 rpoS mutant was subjected to various environmental stresses, and we compared the resistance phenotype of the mutant to that of the parent. The PAO1rpoS mutant was slightly more sensitive to carbon starvation than the wild-type strain, but this phenotype was obvious only when the cells were grown in a medium supplemented with glucose as the sole carbon source. In addition, the PAO1 rpoS mutant was hypersensitive to heat shock at 50°C, increased osmolarity, and prolonged exposure to high concentrations of H2O2. In accordance with the hypersensitivity to H2O2, catalase production was 60% lower in the rpoS mutant than in the parent strain. We also assessed the role of RpoS in the production of several exoproducts known to be important for virulence of P. aeruginosa. TherpoS mutant produced 50% less exotoxin A, but it produced only slightly smaller amounts of elastase and LasA protease than the parent strain. The levels of phospholipase C and casein-degrading proteases were unaffected by a mutation in rpoS in PAO1. The rpoS mutation resulted in the increased production of the phenazine antibiotic pyocyanin and the siderophore pyoverdine. This increased pyocyanin production may be responsible for the enhanced virulence of the PAO1 rpoS mutant that was observed in a rat chronic-lung-infection model. In addition, the rpoSmutant displayed an altered twitching-motility phenotype, suggesting that the colonization factors, type IV fimbriae, were affected. Finally, in an alginate-overproducing cystic fibrosis (CF) isolate, FRD1, the rpoS101::aacCI mutation almost completely abolished the production of alginate when the bacterium was grown in a liquid medium. On a solid medium, the FRD1rpoS mutant produced approximately 70% less alginate than did the wild-type strain. Thus, our data indicate that although some of the functions of RpoS in P. aeruginosa physiology are similar to RpoS functions in other gram-negative bacteria, it also has some functions unique to this bacterium.

scholarly journals The Intracellular Pathogen Rhodococcus equi Produces a Catecholate Siderophore Required for Saprophytic Growth

2007 ◽  
Vol 190 (5) ◽  
pp. 1631-1637 ◽  
Author(s):  
Raúl Miranda-CasoLuengo ◽  
John F. Prescott ◽  
José A. Vázquez-Boland ◽  
Wim G. Meijer
Keyword(s):  
Type Strain ◽  
Wild Type Strain ◽  
Iron Acquisition ◽  
Rhodococcus Equi ◽  
Infection Model ◽  
Intracellular Pathogen ◽  
Wild Type ◽  
Mouse Infection Model ◽  
Iron Concentrations

ABSTRACT Little is known about the iron acquisition systems of the soilborne facultative intracellular pathogen Rhodococcus equi. We previously reported that expression of iupABC, encoding a putative siderophore ABC transporter system, is iron regulated and required for growth at low iron concentrations. Here we show that disruption of iupA leads to the concomitant accumulation of catecholates and a chromophore with absorption maxima at 341 and 528 nm during growth under iron-replete conditions. In contrast, the wild-type strain produces these compounds only in iron-depleted medium. Disruption of iupU and iupS, encoding nonribosomal peptide synthetases, prevented growth of the corresponding R. equi SID1 and SID3 mutants at low iron concentrations. However, only R. equi SID3 did not produce the chromophore produced by the wild-type strain during growth at low iron concentrations. The phenotype of R. equi SID3, but not that of R. equi SID1, could be rescued by coculture with the wild type, allowing growth at low iron concentrations. This strongly suggests that the product of the iupS gene is responsible for the synthesis of a diffusible compound required for growth at low iron concentrations. Transcription of iupU was constitutive, but that of iupS was iron regulated, with an induction of 3 orders of magnitude during growth in iron-depleted compared to iron-replete medium. Neither mutant was attenuated in vivo in a mouse infection model, indicating that the iupU- and iupS-encoded iron acquisition systems are primarily involved in iron uptake during saprophytic life.

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