oalib
Search Results: 1 - 10 of 100 matches for " "
All listed articles are free for downloading (OA Articles)
Page 1 /100
Display every page Item
Selection for Phase Variation of LOS Biosynthetic Genes Frequently Occurs in Progression of Non-Typeable Haemophilus influenzae Infection from the Nasopharynx to the Middle Ear of Human Patients  [PDF]
Kate L. Fox, John M. Atack, Yogitha N. Srikhanta, Anja Eckert, Laura A. Novotny, Lauren O. Bakaletz, Michael P. Jennings
PLOS ONE , 2014, DOI: 10.1371/journal.pone.0090505
Abstract: Surface structures in Haemophilus influenzae are subject to rapid ON/OFF switching of expression, a process termed phase variation. We analyse tetranucleotide repeats controlling phase variation in lipo-oligosaccharide (LOS) genes of H. influenzae in paired isolates from both the nasopharynx and middle ears of paediatric patients with chronic or recurrent otitis media. A change in expression of at least one of the seven phase variable LOS biosynthesis genes was seen in 12 of the 21 strain pairs. Several strains showed switching of expression in multiple LOS genes, consistent with a key role for phase variable LOS biosynthetic genes in human infection.
Occurrence of Haemophilus influenzae strains in three Brazilian states since the introduction of a conjugate Haemophilus influenzae type b vaccine
de Almeida, A.E.C.C.;de Filippis, I.;Abreu, A.O. de;Ferreira, D.G.;Gemal, A.L.;Marzochi, K.B.F.;
Brazilian Journal of Medical and Biological Research , 2005, DOI: 10.1590/S0100-879X2005000500016
Abstract: few vaccines in history have induced such a dramatic decline in incidence over such a short period of time as the haemophilus influenzae type b (hib) conjugate. this vaccine was introduced in 1988 in the united states, but only in 1999 was hib immunization introduced by the brazilian ministry of health as part of the routine infant national immunization program. the authors analyzed 229 h. influenzae (hi) isolates from public health laboratories in three brazilian states: pernambuco (northeast, n = 54), santa catarina (south, n = 19), and rio de janeiro (southeast, n = 156). the isolates were collected from brazilian children 0-10 years of age with meningitis and other infections from 1990 to 2003 and were part of the research collection of the national institute of quality control in health, fiocruz. bacterial strains were characterized by serotyping and biotyping. during the pre-vaccination period the prevalence infection due to hib was of 165 isolates and only 2 non-b hi among all the notified meningitis infections caused by hi. our results showed a significant decrease in the prevalence of hib meningitis from 165 to 33 isolates after 1999. however, during the post-vaccination period of 2001-2003 we observed an increase in the number of non-b hi isolates: only 2 non-b strains isolated from 1990 to 1999 and 29 from 1999 to 2003. based on the present data, the authors emphasize the need for more sensitive epidemiological and bacteriological studies aiming the improvement of the available hib vaccine, in order to protect the susceptible population to infections due to other serological types of hi and the reevaluation of immunization schedules used by the national immunization program.
Occurrence of Haemophilus influenzae strains in three Brazilian states since the introduction of a conjugate Haemophilus influenzae type b vaccine  [cached]
de Almeida A.E.C.C.,de Filippis I.,Abreu A.O. de,Ferreira D.G.
Brazilian Journal of Medical and Biological Research , 2005,
Abstract: Few vaccines in history have induced such a dramatic decline in incidence over such a short period of time as the Haemophilus influenzae type b (Hib) conjugate. This vaccine was introduced in 1988 in the United States, but only in 1999 was Hib immunization introduced by the Brazilian Ministry of Health as part of the routine infant National Immunization Program. The authors analyzed 229 H. influenzae (Hi) isolates from Public Health Laboratories in three Brazilian states: Pernambuco (Northeast, N = 54), Santa Catarina (South, N = 19), and Rio de Janeiro (Southeast, N = 156). The isolates were collected from Brazilian children 0-10 years of age with meningitis and other infections from 1990 to 2003 and were part of the research collection of the National Institute of Quality Control in Health, FIOCRUZ. Bacterial strains were characterized by serotyping and biotyping. During the pre-vaccination period the prevalence infection due to Hib was of 165 isolates and only 2 non-b Hi among all the notified meningitis infections caused by Hi. Our results showed a significant decrease in the prevalence of Hib meningitis from 165 to 33 isolates after 1999. However, during the post-vaccination period of 2001-2003 we observed an increase in the number of non-b Hi isolates: only 2 non-b strains isolated from 1990 to 1999 and 29 from 1999 to 2003. Based on the present data, the authors emphasize the need for more sensitive epidemiological and bacteriological studies aiming the improvement of the available Hib vaccine, in order to protect the susceptible population to infections due to other serological types of Hi and the reevaluation of immunization schedules used by the National Immunization Program.
Assessment of Four Factors That Affect Viability of Lyophilized Haemophilus influenzae Strains
Olga Aulet de Saab,Olga Aulet de Saab,Marta Cecilia de Castillo
Asian Journal of Information Technology , 2012,
Abstract: The present work assesses four factors to determine their influence on the viability of lyophilized Haemophilus influenzae strains and their -lactamase production: different suspension media, rehydration media, rehydration time and initial inoculum concentration. Three strains were obtained from inpatients from a state hospital, one of which was a -lactamase producing (TEM-1) strain. H. influenzae ATCC 10211 and ATCC 35056 were used as control strains for the culture medium and -lactamase production respectively. The media assayed were: 1) Brain Heart Infusion broth (BHI) was used as suspension medium with or without supplement of 6% lactose (BHI+L) or 10% sucrose (BHI+S), both cryo-protective agents, and 2) 10% skim milk with addition of 5% glutamate (SM+G). Different types of rehydration agents were assayed: BHI, BHI+L, BHI+S, water (H2O) and physiological solution (PS). Furthermore, different rehydration times were assayed (0-12 h), as well as the initial cell concentration (1016 to 102 CFU/ml). Highest viability of lyophilized H.influenzae strains was obtained with initial cell concentrations 1016 CFU/ml (45%?0.10), in BHI supplemented with cryoprotective agents: BHI+L (51%?0.02) or BHI+S (45.5%?0,10), rehydration with water (61%?0.09) at room temperature for 15 min (59.9%?0.47). Enzyme activity was not modified in any of the cases.
Characterization and modeling of the Haemophilus influenzae core and supragenomes based on the complete genomic sequences of Rd and 12 clinical nontypeable strains
Justin S Hogg, Fen Z Hu, Benjamin Janto, Robert Boissy, Jay Hayes, Randy Keefe, J Christopher Post, Garth D Ehrlich
Genome Biology , 2007, DOI: 10.1186/gb-2007-8-6-r103
Abstract: We derived high depth genomic coverage of nine nontypeable Haemophilus influenzae (NTHi) clinical isolates, bringing to 13 the number of sequenced NTHi genomes. Clustering identified 2,786 genes, of which 1,461 were common to all strains, with each of the remaining 1,328 found in a subset of strains; the number of clusters ranged from 1,686 to 1,878 per strain. Genic differences of between 96 and 585 were identified per strain pair. Comparisons of each of the NTHi strains with the Rd strain revealed between 107 and 158 insertions and 100 and 213 deletions per genome. The mean insertion and deletion sizes were 1,356 and 1,020 base-pairs, respectively, with mean maximum insertions and deletions of 26,977 and 37,299 base-pairs. This relatively large number of small rearrangements among strains is in keeping with what is known about the transformation mechanisms in this naturally competent pathogen.A finite supragenome model was developed to explain the distribution of genes among strains. The model predicts that the NTHi supragenome contains between 4,425 and 6,052 genes with most uncertainty regarding the number of rare genes, those that have a frequency of <0.1 among strains; collectively, these results support the DGH.Haemophilus influenzae is a Gram-negative bacterium that colonizes the human nasopharynx and is also etiologically associated with a spectrum of acute and chronic diseases. There are six recognized capsular serotypes (a-f), but the majority of clinical strains are unencapsulated and are referred to as nontypeable H. influenzae (NTHi). The type b polysaccharide capsular variants (Hib) are associated with invasive disease, particularly meningitis; however, the introduction of a highly effective vaccine has nearly eliminated this pathogen from developed countries. Recent studies have demonstrated that the NTHi form biofilms on the respiratory mucosa of humans and other mammals and it has been hypothesized that this contributes to the chronicity of these i
Antimicrobial resistance among invasive Haemophilus influenzae strains: results of a Brazilian study carried out from 1996 through 2000
Casagrande, S.T.;Landgraf, I.M.;Kobata, A.M.M.;Zanella, R.C.;Bokermann, S.;
Brazilian Journal of Medical and Biological Research , 2002, DOI: 10.1590/S0100-879X2002001100006
Abstract: a total of 1712 strains of haemophilus influenzae isolated from patients with invasive diseases were obtained from ten brazilian states from 1996 to 2000. ?-lactamase production was assessed and the minimum inhibitory concentrations (mic) of ampicillin, chloramphenicol, ceftriaxone and rifampin were determined using a method for broth microdilution of haemophilus test medium. the prevalence of strains producing ?-lactamase ranged from 6.6 to 57.7%, with an overall prevalence of 18.4%. high frequency of ?-lactamase-mediated ampicillin resistance was observed in distrito federal (25%), s?o paulo (21.7%) and paraná (18.5%). of the 1712 strains analyzed, none was ?-lactamase negative, ampicillin resistant. a total of 16.8% of the strains were resistant to chloramphenicol, and 13.8% of these also presented resistance to ampicillin, and only 3.0% were resistant to chloramphenicol alone. all strains were susceptible to ceftriaxone and rifampin and the mic90 were 0.015 μg/ml and 0.25 μg/ml, respectively. ceftriaxone is the drug of choice for empirical treatment of bacterial meningitis in pediatric patients who have not been screened for drug susceptibility. the emergence of drug resistance is a serious challenge for the management of invasive h. influenzae disease, which emphasizes the fundamental role of laboratory-based surveillance for antimicrobial resistance.
Antimicrobial resistance among invasive Haemophilus influenzae strains: results of a Brazilian study carried out from 1996 through 2000  [cached]
Casagrande S.T.,Landgraf I.M.,Kobata A.M.M.,Zanella R.C.
Brazilian Journal of Medical and Biological Research , 2002,
Abstract: A total of 1712 strains of Haemophilus influenzae isolated from patients with invasive diseases were obtained from ten Brazilian states from 1996 to 2000. -Lactamase production was assessed and the minimum inhibitory concentrations (MIC) of ampicillin, chloramphenicol, ceftriaxone and rifampin were determined using a method for broth microdilution of Haemophilus test medium. The prevalence of strains producing -lactamase ranged from 6.6 to 57.7%, with an overall prevalence of 18.4%. High frequency of -lactamase-mediated ampicillin resistance was observed in Distrito Federal (25%), S o Paulo (21.7%) and Paraná (18.5%). Of the 1712 strains analyzed, none was -lactamase negative, ampicillin resistant. A total of 16.8% of the strains were resistant to chloramphenicol, and 13.8% of these also presented resistance to ampicillin, and only 3.0% were resistant to chloramphenicol alone. All strains were susceptible to ceftriaxone and rifampin and the MIC90 were 0.015 μg/ml and 0.25 μg/ml, respectively. Ceftriaxone is the drug of choice for empirical treatment of bacterial meningitis in pediatric patients who have not been screened for drug susceptibility. The emergence of drug resistance is a serious challenge for the management of invasive H. influenzae disease, which emphasizes the fundamental role of laboratory-based surveillance for antimicrobial resistance.
Ribotyping, biotyping and capsular typing of Haemophilus influenzae strains isolated from patients in Campinas, southeast Brazil
Lancellotti, Marcelo;Pace, Fernanda de;Stehling, Eliana Guedes;Villares, Maria Cecília Barisson;Brocchi, Marcelo;Silveira, Wanderley Dias da;
Brazilian Journal of Infectious Diseases , 2008, DOI: 10.1590/S1413-86702008000500015
Abstract: forty-five haemophilus influenzae strains isolated from patients were characterized based on biochemical characteristics. their capsular types were determined by polymerase chain reaction (pcr); they were compared, using two molecular methods [ribotyping with a specific dna probe amplified from the 16s rdna region from h. influenzae and through restriction fragment length polymorphism (rlfp) of an amplified 16s dna region]. the strains were better discriminated by the ribotyping technique that used the 16s probe and by the combination of both techniques. biotypes i and iv were the most common, followed by biotypes vi, viii and iii. biotypes ii and vii were not found. most of the capsular samples were nontypable (89%), with capsular types a and b found in 2 and 9% of the samples, respectively. we concluded that there is a very close genetic identity among pathogenic and non-pathogenic strains.
Trend in Antibiotic Resistance of Streptococcus Pneumoniae and Haemophilus Influenzae Strains Isolated from Community Acquired Respiratory Tract Infections in Dakar, Senegal Between 2005 and 2008
A. Guèye Ndiaye, Hounkponou Edwige, Fatou Bintou Guèye and Cheikh Saad Bouh Boye
Microbiology Insights , 2012, DOI: 10.4137/MBI.S3819
Abstract: Development of antibiotic resistance among common respiratory pathogens is a major cause of concern worldwide. Streptococcus pneumoniae and Haemophilus influenzae are among the most common respiratory pathogens. In this study, representative samples obtained from 3 different medical centers in Dakar, Senegal were subjected to antibiotic susceptibility testing. The samples were collected from 2005 to 2008 and the data obtained was compared to establish resistance patterns between the two years (i.e. 2005–2006 to 2007–2008). S. pneumoniae exhibited a significant increase in the resistance to azithromycin and the intermediate susceptibility to penicillin G and cotrimoxazole. H. influenzae also exhibited a significant increase in resistance to azithromycin and intermediate susceptibility to chloramphenicol. None of H. influenzae samples were resistant to amoxicillin/clavulanic acid, cephalosporin and fluroquinolones and most of the S. pneumoniae isolates demonstrated high susceptibility to the antibiotics tested. Results from this study will provide greater insights to antibiotic therapy during respiratory tract infections in Dakar, Senegal. This study also establishes the importance of continuous monitoring of antibiotic susceptibility patterns that are often region-specific.
Trend in Antibiotic Resistance of Streptococcus Pneumoniae and Haemophilus Influenzae Strains Isolated from Community Acquired Respiratory Tract Infections in Dakar, Senegal Between 2005 and 2008
A. Guèye Ndiaye,Hounkponou Edwige,Fatou Bintou Guèye,Cheikh Saad Bouh Boye
Microbiology Insights , 2010,
Abstract: Development of antibiotic resistance among common respiratory pathogens is a major cause of concern worldwide. Streptococcus pneumoniae and Haemophilus influenzae are among the most common respiratory pathogens. In this study, representative samples obtained from 3 different medical centers in Dakar, Senegal were subjected to antibiotic susceptibility testing. The samples were collected from 2005 to 2008 and the data obtained was compared to establish resistance patterns between the two years (i.e. 2005–2006 to 2007–2008). S. pneumoniae exhibited a significant increase in the resistance to azithromycin and the intermediate susceptibility to penicillin G and cotrimoxazole. H. influenzae also exhibited a significant increase in resistance to azithromycin and intermediate susceptibility to chloramphenicol. None of H. influenzae samples were resistant to amoxicillin/clavulanic acid, cephalosporin and fluroquinolones and most of the S. pneumoniae isolates demonstrated high susceptibility to the antibiotics tested. Results from this study will provide greater insights to antibiotic therapy during respiratory tract infections in Dakar, Senegal. This study also establishes the importance of continuous monitoring of antibiotic susceptibility patterns that are often region-specific.
Page 1 /100
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.