scholarly journals Impact of Glutamine Transporters on Pneumococcal Fitness under Infection-Related Conditions

2010 ◽  
Vol 79 (1) ◽  
pp. 44-58 ◽  
Author(s):  
Tobias Härtel ◽  
Matthias Klein ◽  
Uwe Koedel ◽  
Manfred Rohde ◽  
Lothar Petruschka ◽  
...  

ABSTRACTThe genomic analysis ofStreptococcuspneumoniaepredicted six putative glutamine uptake systems, which are expressed underinvitroconditions, as shown here by reverse transcription-PCR. Four of these operons consist ofglnHPQ, while two lackglnH, which encodes a soluble glutamine-binding protein. Here, we studied the impact of two of these glutamine ATP-binding cassette transporters onS.pneumoniaeD39 virulence and phagocytosis, which consist of GlnQ and a translationally fused protein of GlnH and GlnP. Mice infected intranasally with D39Δgln0411/0412showed significantly increased survival times and a significant delay in the development of pneumococcal pneumonia compared to those infected with D39, as observed in real time using bioluminescent pneumococci. In a mouse sepsis model, the mutant D39Δgln0411/0412showed only moderate but significant attenuation. In contrast, the D39Δgln1098/1099knockout strain was massively attenuated in the pneumonia and septicemia mouse infection model. To cause pneumonia or sepsis with D39Δgln1098/1099, infection doses 100- to 10,000-fold higher than those used for wild-type strain D39 were required. In an experimental mouse meningitis model, D39Δgln1098/1099produced decreased levels of white blood cells in cerebrospinal fluid and showed decreased numbers of bacteria in the bloodstream compared to D39 and D39Δgln0411/0412. Phagocytosis experiments revealed significantly decreased intracellular survival rates of mutants D39Δgln1098/1099and D39Δgln0411/0412compared to wild-type D39, suggesting that the deficiency of Gln uptake systems impairs resistance to oxidative stress. Taken together, our results demonstrate that both glutamine uptake systems are required for full virulence of pneumococci but exhibit different impacts on the pathogenesis of pneumococci underinvivoconditions.

2019 ◽  
Vol 87 (9) ◽  
Author(s):  
Dereje D. Gudeta ◽  
Mei G. Lei ◽  
Chia Y. Lee

ABSTRACTThe SaeRS two-component system inStaphylococcus aureusis critical for regulation of many virulence genes, includinghla, which encodes alpha-toxin. However, the impact of regulation of alpha-toxin by Sae onS. aureuspathogenesis has not been directly addressed. Here, we mutated the SaeR-binding sequences in thehlaregulatory region and determined the contribution of this mutation tohlaexpression and pathogenesis in strain USA300 JE2. Western blot analyses revealed drastic reduction of alpha-toxin levels in the culture supernatants of SaeR-binding mutant in contrast to the marked alpha-toxin production in the wild type. The SaeR-binding mutation had no significant effect on alpha-toxin regulation by Agr, MgrA, and CcpA. In animal studies, we found that the SaeR-binding mutation did not contribute to USA300 JE2 pathogenesis using a rat infective endocarditis model. However, in a rat skin and soft tissue infection model, the abscesses on rats infected with the mutant were significantly smaller than the abscesses on those infected with the wild type but similar to the abscesses on those infected with asaeRmutant. These studies indicated that there is a direct effect ofhlaregulation by SaeR on pathogenesis but that the effect depends on the animal model used.


2022 ◽  
Author(s):  
Vinay Kumar Nandicoori ◽  
Saba Naz ◽  
Kumar Paritosh ◽  
Priyadarshini Sanyal ◽  
Sidra Khan ◽  
...  

The emergence of drug resistance in Mycobacterium tuberculosis (Mtb) is alarming and demands in-depth knowledge for timely diagnosis. We performed genome-wide association analysis (GWAS) using 2237 clinical strains of Mtb to identify novel genetic factors that evoke drug resistance. In addition to the known direct targets, for the first time, we identified a strong association between the mutations in the DNA repair genes and the multidrug-resistant phenotype. To evaluate the impact of variants identified in the clinical samples in the evolution of drug resistance, we utilized knockouts and complemented strains in Mycobacterium smegmatis (Msm) and Mtb. Results show that variant mutations abrogated the function of MutY and UvrB. MutY variant showed enhanced survival compared with wild-type (Rv) when the Mtb strains were subjected to multiple rounds of ex vivo antibiotic stress. Notably, in an in vivo Guinea pig infection model, the MutY variant outcompeted the wild-type strain. Collectively, we show that novel variant mutations in the DNA repair genes abrogate their function and contribute to better survival under antibiotic/host stress conditions.


2015 ◽  
Vol 59 (5) ◽  
pp. 2855-2866 ◽  
Author(s):  
Seyedmojtaba Seyedmousavi ◽  
Roger J. M. Brüggemann ◽  
Jacques F. Meis ◽  
Willem J. G. Melchers ◽  
Paul E. Verweij ◽  
...  

ABSTRACTAzole resistance is an emerging problem inAspergillus fumigatuswhich translates into treatment failure. Alternative treatments with new azoles may improve therapeutic outcome in invasive aspergillosis (IA) even for strains with decreased susceptibility to current azoles. Thein vivoefficacy of 0.25, 1, 4, 16, 64, 128, 256, and 512 mg/kg of body weight/day prodrug isavuconazonium sulfate (BAL8557) (isavuconazole [ISA]-equivalent doses of 0.12, 0.48, 1.92, 7.68, 30.7, 61.4, 122.9, and 245.8 mg/kg/day, respectively) administered by oral gavage was assessed in an immunocompetent murine model of IA against four clinicalA. fumigatusisolates: a wild-type isolate (ISA MICEUCAST, 0.5 mg/liter) and three azole-resistant isolates harboring substitutions in thecyp51Agene: G54W (ISA MICEUCAST, 0.5 mg/liter), M220I (ISA MICEUCAST, 4 mg/liter), and TR34/L98H (ISA MICEUCAST, 8 mg/liter). The maximum effect (100% survival) was reached at a prodrug isavuconazonium sulfate dose of 64 mg/kg for the wild-type isolate, 128 mg/kg for the G54W mutant, and 256 mg/kg two times per day (q12) for the M220I mutant. A maximum response was not achieved with the TR34/L98H isolates with the highest dose of prodrug isavuconazonium sulfate (256 mg/kg q12). For a survival rate of 50%, the effective AUC0–24/MICEUCASTratio for ISA total drug was 24.73 (95% confidence interval, 22.50 to 27.18). The efficacy of isavuconazole depended on both the drug exposure and the isavuconazole MIC of the isolates. The quantitative relationship between exposure and effect (AUC0–24/MIC) can be used to optimize the treatment of human infections byA. fumigatus, including strains with decreased susceptibility.


2016 ◽  
Vol 84 (6) ◽  
pp. 1917-1929 ◽  
Author(s):  
Carolyn B. Ibberson ◽  
Corey P. Parlet ◽  
Jakub Kwiecinski ◽  
Heidi A. Crosby ◽  
David K. Meyerholz ◽  
...  

Staphylococcus aureusis a leading cause of chronic biofilm infections. Hyaluronic acid (HA) is a large glycosaminoglycan abundant in mammalian tissues that has been shown to enhance biofilm formation in multiple Gram-positive pathogens. We observed that HA accumulated in anS. aureusbiofilm infection using a murine implant-associated infection model and that HA levels increased in a mutant strain lacking hyaluronidase (HysA).S. aureussecretes HysA in order to cleave HA during infection. Throughin vitrobiofilm studies with HA, thehysAmutant was found to accumulate increased biofilm biomass compared to the wild type, and confocal microscopy showed that HA is incorporated into the biofilm matrix. Exogenous addition of purified HysA enzyme dispersed HA-containing biofilms, while catalytically inactive enzyme had no impact. Additionally, induction ofhysAexpression prevented biofilm formation and also dispersed an established biofilm in the presence of HA. These observations were corroborated in the implant model, where there was decreased dissemination from anhysAmutant biofilm infection compared to theS. aureuswild type. Histopathology demonstrated that infection with anhysAmutant caused significantly reduced distribution of tissue inflammation compared to wild-type infection. To extend these studies, the impact of HA andS. aureusHysA on biofilm-like aggregates found in joint infections was examined. We found that HA contributes to the formation of synovial fluid aggregates, and HysA can disrupt aggregate formation. Taken together, these studies demonstrate that HA is a relevant component of theS. aureusbiofilm matrix and HysA is important for dissemination from a biofilm infection.


Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 4765-4765
Author(s):  
Michelle L Sotak ◽  
Mihaela Marin ◽  
John Coombs ◽  
Gary J. Schiller ◽  
April Teitelbaum

Abstract Abstract 4765 Introduction: Patients with FLT3-mutated AML have poor prognoses due to shorter survival, a high incidence of relapse, and a lack of effective treatment options. Limited information is published on the burden of illness (BOI) of AML, especially for patients with FLT3-mutated disease. This study reviewed the epidemiologic, clinical, humanistic, and economic literature and estimated the burden of FLT3-mutated AML in the US. Methods: A systematic literature review was conducted in PubMed to identify clinical and economic publications on AML published in English from 2000 to 2011. Data relevant to the burden of FLT3-mutated AML were abstracted. 607 citations were identified in PubMed. 581 abstracts were screened and 35 articles were abstracted. Epidemiologic data were also sought from the Surveillance, Epidemiology and End Results (SEER) database. Areas where information was limited or not available were identified and discussed with clinicians experienced in treating AML. An Excel model was then developed to estimate the population-level BOI of AML by FLT3 status. Resource utilization estimates were obtained from the literature and expert opinion. Direct costs included procedures, hospitalizations, outpatient/office visits, other resource use (home health care, hospice, skilled nursing facility), and medications (including chemotherapy). Indirect costs included lost productivity but did not include costs associated with premature retirement or premature mortality. Results: In patients age <60 years, the literature reported FLT3 mutations in up to 30% of AML cases. Patients with FLT3-mutated AML have poorer prognoses: per the literature, median overall survival estimates of 15.2–15.5 months for FLT3-mutated AML patients <60 years of age was noted compared to 19.3–28.6 months for wild-type AML patients. Five-year survival rates for age <60 years range from 15% for high ITD-mutant levels to 31% in low ITD mutant-levels for FLT3-mutated AML patients vs. 42% for wild-type AML patients. No studies were identified containing estimates for the incidence or prevalence of FLT-3 mutated AML. The prevalence of AML in 2008 was obtained from SEER data and was estimated at 27,813 patients aged ≥20 years. Age- and gender-specific incidence and relative 5-year survival rates were obtained from SEER data. Projections for the prevalence, incidence, and mortality of FLT3-mutated AML through 2020 were calculated based on the SEER estimates, age- and gender-specific US Census population projections, and an assumption of FLT3 mutations in 23% of AML cases. In 2010, it was estimated that 725 patients aged 20–60 years were diagnosed with FLT3-mutated AML, with 572 disease-related deaths. Three studies were identified which reported information on the impact of AML on quality of life (QoL), though none described the QoL impact of FLT-3 mutated AML. One study specifically examined the <60 year old population, noting that AML patients receiving stem cell transplants had significantly worse long-term impact on QoL vs. patients receiving conventional chemotherapy. No studies quantifying the impact of AML on productivity were identified. In our analysis, the overall economic burden of FLT-3 mutated AML in the US was estimated at $244 million in 2010, including $184 million in direct costs and $60 million in indirect costs from lost productivity. Stem cell transplants accounted for 21% of direct costs, inpatient hospitalizations accounted for 44%, and medications for 4%. For AML patients <60 years, the overall cost per newly diagnosed FLT3-mutated AML patient was estimated at $114,198 vs. $105,825 for newly diagnosed FLT3-wild-type AML patients. This is likely an underestimate of the cost as the impacts of early mortality and early retirement were not included in the indirect costs. In addition, the impact of QoL was not included and this may also underestimate costs due to more frequent use of transplantation in the FLT3-mutated AML population. Conclusions: AML poses a large economic burden, both for the healthcare system and society. FLT3-mutated AML potentially represents a greater per-patient burden than FLT3 wild type AML due to shorter survival rates and use of more costly therapies such as stem cell transplants. Investigational treatments targeting the FLT3 mutation may provide an additional therapeutic option for these patients and have the potential to improve clinical outcomes. Disclosures: Sotak: Novartis: Research Funding. Marin:Novartis: Research Funding. Coombs:Novartis: Employment. Schiller:BMS: Research Funding; Celgene: Research Funding; Ambit: Research Funding; Novartis: Research Funding; Sunesis: Research Funding. Teitelbaum:Novartis: Research Funding.


2011 ◽  
Vol 79 (6) ◽  
pp. 2404-2411 ◽  
Author(s):  
Jessica S. Hoff ◽  
Mark DeWald ◽  
Steve L. Moseley ◽  
Carleen M. Collins ◽  
Jovanka M. Voyich

ABSTRACTStreptococcus pyogenesis an important human pathogen with an expansive repertoire of verified and putative virulence factors. Here we demonstrate that a mutant deficient in the production of the streptococcal ADP-ribosyltransferase SpyA generates lesions of reduced size in a subcutaneous mouse infection model. At early stages of infection, when the difference in lesion size is first established, inflamed tissue isolated from lesions of mice infected withspyAmutant bacteria has higher levels of mRNA encoding the chemokines CXCL1 and CCL2 than does tissue isolated from mice infected with wild-type bacteria. In addition, at these early times, the mRNA levels for the gene encoding the intermediate filament vimentin are higher in the mutant-infected tissue. As wound resolution progresses, mRNA levels of the gene encoding matrix metallopeptidase 2 are lower in mutant-infected tissue. Furthermore, we demonstrate that thespyAmutant is internalized more efficiently than wild-type bacteria by HeLa cells. We conclude that SpyA contributes to streptococcal pathogenesis in the mouse subcutaneous infection model. Our observations suggest that the presence of SpyA delays wound healing in this model.


2010 ◽  
Vol 78 (11) ◽  
pp. 4660-4666 ◽  
Author(s):  
Ge Wang ◽  
Susan E. Maier ◽  
Leja F. Lo ◽  
George Maier ◽  
Shruti Dosi ◽  
...  

ABSTRACT An oxidative stress-induced enzyme, peptidoglycan deacetylase (PgdA), in the human gastric pathogen Helicobacter pylori was previously identified and characterized. In this study, we constructed H. pylori pgdA mutants in two mouse-adapted strains, X47 and B128, to investigate the role of PgdA in vivo (to determine the mutants’ abilities to colonize mice and to induce an immune response). H. pylori pgdA mutant cells showed increased sensitivity to lysozyme compared to the sensitivities of the parent strains. We demonstrated that the expression of PgdA was significantly induced (3.5-fold) when H. pylori cells were in contact with macrophages, similar to the effect observed with oxidative stress as the environmental inducer. Using a mouse infection model, we first examined the mouse colonization ability of an H. pylori pgdA mutant in X47, a strain deficient in the major pathway (cag pathogenicity island [PAI] encoded) for delivery of peptidoglycan into host cells. No animal colonization difference between the wild type and the mutant was observed 3 weeks after inoculation. However, the pgdA mutant showed a significantly attenuated ability to colonize mouse stomachs (9-fold-lower bacterial load) at 9 weeks postinoculation. With the cag PAI-positive strain B128, a significant colonization difference between the wild type and the pgdA mutant was observed at 3 weeks postinoculation (1.32 × 104 versus 1.85 × 103 CFU/gram of stomach). To monitor the immune responses elicited by H. pylori in the mouse infection model, we determined the concentrations of cytokines present in mouse sera. In the mice infected with the pgdA mutant strain, we observed a highly significant increase in the level of MIP-2. In addition, significant increases in interleukin-10 and tumor necrosis factor alpha in the pgdA mutant-infected mice compared to the levels in the wild-type H. pylori-infected mice were also observed. These results indicated that H. pylori peptidoglycan deacetylation is an important mechanism for mitigating host immune detection; this likely contributes to pathogen persistence.


2012 ◽  
Vol 57 (4) ◽  
pp. 1577-1582 ◽  
Author(s):  
W. A. Craig ◽  
D. R. Andes

ABSTRACTCeftolozane is a new cephalosporin with potent activity againstPseudomonas aeruginosaandEnterobacteriaceae. A neutropenic murine thigh infection model was used to determine which pharmacokinetic/pharmacodynamic index and magnitude drives the efficacy of ceftolozane with Gram-negative bacilli, to compare the rates ofin vivokilling ofP. aeruginosaby ceftolozane and ceftazidime, and to determine the impact of different ratios of ceftolozane plus tazobactam onEnterobacteriaceaecontaining extended-spectrum β-lactamases (ESBLs). Neutropenic mice had 106.2-7.1CFU/thigh when treated with ceftolozane for 24 h with (i) various doses (3.12 to 1,600 mg/kg) and dosage intervals (3, 6, 12, and 24 h) against twoEnterobacteriaceaestrains, (ii) 0.39 to 800 mg/kg every 6 h for fourEnterobacteriaceaeand fourP. aeruginosastrains, and (iii) 400 or 800 mg/kg with 2:1. 4:1, and 8:1 ratios of tazobactam against fiveEnterobacteriaceaestrains with ESBLs. The pharmacokinetics of ceftolozane at 25, 100, and 400 mg/kg were linear with peak/dose values of 1.0 to 1.4 and half-lives of 12 to 14 min. T>MIC was the primary index driving efficacy. For stasis (1 log kill), T>MIC was 26.3% ± 2.1% (31.6% ± 1.6%) for wild-typeEnterobacteriaceae, 31.1% ± 4.9% (34.8% ± 4.4%) forEnterobacteriaceaewith ESBLs, and 24.0% ± 3.3% (31.5% ± 3.9%) forP. aeruginosa. At 200 mg/kg every 3 h, the rate ofin vivokilling ofP. aeruginosawas faster with ceftolozane than with ceftazidime (−0.34 to −0.41 log10CFU/thigh/h versus −0.21 to −0.24 log10CFU/thigh/h). The 2:1 ratio of ceftolozane with tazobactam was the most potent combination studied. The T>MIC required for ceftolozane is less than with other cephalosporins and may be due to more rapid killing.


2021 ◽  
Vol 9 (12) ◽  
pp. 2564
Author(s):  
Momen Askoura ◽  
Ahmad J. Almalki ◽  
Amr S. Abu Lila ◽  
Khaled Almansour ◽  
Farhan Alshammari ◽  
...  

Salmonella enterica is a common cause of many enteric infections worldwide and is successfully engineered to deliver heterologous antigens to be used as vaccines. Clustered Regularly Interspaced Short Palindromic Repeats (CRISPRs) RNA-guided Cas9 endonuclease is a promising genome editing tool. In the current study, a CRISPR-Cas9 system was used to target S.enterica sdiA that encodes signal molecule receptor SdiA and responds to the quorum sensing (QS) signaling compounds N-acylhomoserine lactones (AHLs). For this purpose, sdiA was targeted in both S.enterica wild type (WT) and the ΔssaV mutant strain, where SsaV has been reported to be an essential component of SPI2-T3SS. The impact of sdiA mutation on S. enterica virulence was evaluated at both early invasion and later intracellular replication in both the presence and absence of AHL. Additionally, the influence of sdiA mutation on the pathogenesis S. enterica WT and mutants was investigated in vivo, using mice infection model. Finally, the minimum inhibitory concentrations (MICs) of various antibiotics against S. enterica strains were determined. Present findings show that mutation in sdiA significantly affects S.enterica biofilm formation, cell adhesion and invasion. However, sdiA mutation did not affect bacterial intracellular survival. Moreover, in vivo bacterial pathogenesis was markedly lowered in S.enterica ΔsdiA in comparison with the wild-type strain. Significantly, double-mutant sdiA and ssaV attenuated the S. enterica virulence and in vivo pathogenesis. Moreover, mutations in selected genes increased Salmonella susceptibility to tested antibiotics, as revealed by determining the MICs and MBICs of these antibiotics. Altogether, current results clearly highlight the importance of the CRISPR-Cas9 system as a bacterial genome editing tool and the valuable role of SdiA in S.enterica virulence. The present findings extend the understanding of virulence regulation and host pathogenesis of Salmonellaenterica.


2018 ◽  
Author(s):  
Neuza Teixeira ◽  
António Jacinto ◽  
Maria de Fátima Silva Lopes

ABSTRACTEnterococcus faecalisis a human opportunist pathogen able to infect and killDrosophila. Previous studies proved thatE. faecaliscarrying the Fsr quorum sensing system are extremely virulent. Fsr is the regulator of two important virulence factors, gelatinase and serine protease, which cause death ofDrosophilaadult flies by decreasing its tolerance to infection. The exact mechanism underlying the toxicity of theseE. faecalisvirulence factors is nevertheless not known, in particular the way they interfere with the host immune response. In the present study, we investigated the influence of Fsr-GelE-SprE bacterial factors on different immunity responses, namely antimicrobial peptide production, phagocytosis and melanization. UsingE. faecalisV583 wild type andE. faecalisV583 ΔfsrBΔgelEΔsprEmutant we showed that both drosomycin production and phagocytosis were activated to similar levels by the two bacterial strains. However, fly pupae infected with the mutant strain showed less melanization and higher survival rates when compared to pupae infected with wild type bacteria. Using adult flies carrying thePPO1ΔPPO2Δmutation, we found that absence of melanization had a different impact in survival of the flies when infected with the twoE. faecalisstrains.PPO1Δ,PPO2Δmutant flies were more tolerant toE. faecalisdeprived of its major virulence factors. By showing that the presence of theE. faecalisproteases completely alters the impact of melanization activation onDrosophilatolerance, this study provides new clues on the interactions betweenE. faecalisvirulence factors and the fly´s immune system. Future studies onDrosophilaimmunity should consider the pathogen genomic content.


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