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Your search keyword '"Beres, Stephen B."' showing total 31 results
Start Over Author "Beres, Stephen B." Publisher american society for microbiology
31 results on '"Beres, Stephen B."'

5. Population Genomic Molecular Epidemiological Study of Macrolide-Resistant Streptococcus pyogenes in Iceland, 1995 to 2016: Identification of a Large Clonal Population with a pbp2x Mutation Conferring Reduced In Vitro β-Lactam Susceptibility

Author

Southon, Sara B., Beres, Stephen B., Kachroo, Priyanka, Saavedra, Matthew Ojeda, Erlendsdóttir, Helga, Haraldsson, Gunnsteinn, Yerramilli, Prasanti, Pruitt, Layne, Zhu, Luchang, Musser, James M., Kristinsson, Karl G., Læknadeild (HÍ), Faculty of Medicine (UI), Heilbrigðisvísindasvið (HÍ), School of Health Sciences (UI), Háskóli Íslands, and University of Iceland

Subjects
Antibiotic resistance, Streptococcus pyogenes, Molecular epidemiology, Sýkingar, Macrolides, Population genomics, Erfðarannsóknir, Sýklalyf
Abstract

Publisher's version (útgefin grein), Resistance to macrolide antibiotics is a global concern in the treatment of Streptococcus pyogenes (group A Streptococcus [GAS]) infections. In Iceland, since the detection of the first macrolide-resistant isolate in 1998, three epidemic waves of macrolide-resistant GAS infections have occurred, with peaks in 1999, 2004, and 2008. We conducted whole-genome sequencing of all 1,575 available GAS macrolide-resistant clinical isolates of all infection types collected at the national reference laboratory in Reykjavik, Iceland, from 1998 to 2016. Among 1,515 erythromycin-resistant isolates, 90.3% were of only three emm types, emm4 (n = 713), emm6 (n = 324), and emm12 (n = 332), with each being predominant in a distinct epidemic peak. The antibiotic efflux pump genes, mef(A) and msr(D), were present on chimeric mobile genetic elements in 99.3% of the macrolide-resistant isolates of these emm types. Of note, in addition to macrolide resistance, virtually all emm12 isolates had a single amino acid substitution in penicillin-binding protein PBP2X that conferred a 2-fold increased penicillin G and ampicillin MIC among the isolates tested. We conclude that each of the three large epidemic peaks of macrolide-resistant GAS infections occurring in Iceland since 1998 was caused by the emergence and clonal expansion of progenitor strains, with macrolide resistance being conferred predominantly by inducible Mef(A) and Msr(D) drug efflux pumps. The occurrence of emm12 strains with macrolide resistance and decreased beta-lactam susceptibility was unexpected and is of public health concern., This study was supported in part by the Fondren Foundation, Houston Methodist Hospital and Research Institute, and National Institutes of Health grants AI139369 and AI146771 (to J.M.M.).

Published
2020

6. Reduced in vitro susceptibility of Streptococcus pyogenes to beta-lactam antibiotics associated with mutations in the pbp2x gene is geographically widespread

Author

Musser, James M., Beres, Stephen B., Zhu, Luchang, Olsen, Randall J., Vuopio, Jaana, Hyyryläinen, Hanne-Leena, Gröndahl-Yli-Hannuksela, Kirsi, Kristinsson, Karl G., Darenberg, Jessica, Henriques-Normark, Birgitta, Hoffmann, Steen, Caugant, Dominque A., Smith, Andrew J., Lindsay, Diane S.J., Boragine, David, and Palzkill, Timothy

Abstract

Recently two related Streptococcus pyogenes strains with reduced susceptibility to ampicillin, amoxicillin and cefotaxime, antibiotics commonly used to treat S. pyogenes infections were reported. The two strains had the same nonsynonymous (amino acid-substituting) mutation in the pbp2x gene encoding penicillin-binding protein 2X (PBP2X). This concerning report led us to investigate our library of 7,025 genome sequences of type emm1, emm28, and emm89 S. pyogenes clinical strains recovered from intercontinental sources for mutations in pbp2x. We identified 137 strains that combined had 37 nonsynonymous mutations in 36 codons in pbp2x. Although to a lesser magnitude than the two previously published isolates, many of our strains had decreased susceptibility in vitro to multiple beta-lactam antibiotics. Many pbp2x mutations were found only in single strains, but 16 groups of two or more isolates of the same emm type had an identical amino acid replacement. Phylogenetic analysis showed that with one exception, strains of the same emm type with the same amino acid replacement were clonally related by descent. This finding indicates that strains with some amino acid changes in PBP2X can successfully spread to new human hosts and cause invasive infections. Mapping of the amino acid changes onto a three-dimensional structure of the related Streptococcus pneumoniae PBP2X suggests that some substitutions are located in regions functionally important in related pathogenic bacterial species. Decreased beta-lactam susceptibility is geographically widespread in strains of numerically common emm gene subtypes. Enhanced surveillance and further epidemiological and molecular genetic study of this potential emergent antimicrobial problem are warranted.

Published
2020

8. In vitro serial passage of Staphylococcus aureus: changes in psysiology, virulence factor production, and agr nucleotide sequence

Author

Somerville, Greg A., Beres, Stephen B., Fitzgerald, J. Ross, DeLeo, Frank R., Cole, Robert L., Hoff, Jessica S., and Musser, James M.

Subjects
Bacteriology -- Research, Nucleotides -- Physiological aspects, Staphylococcus aureus -- Genetic aspects, Toxic shock syndrome -- Causes of, Biological sciences
Abstract

Research has been conducted on Staphylococcus aureus strains, recovered from the patient with toxic shock syndrome, which have high aconitase activity. The hypothesis that the aconitase specific activity decreases over time during the in vitro passage has been examined and the effect of the serial passage on the growth and virulence factor production has been investigated.

Published
2002

10. Population Genomic Molecular Epidemiological Study of Macrolide-Resistant Streptococcus pyogenes in Iceland, 1995 to 2016: Identification of a Large Clonal Population with a pbp2x Mutation Conferring Reduced In Vitro β-Lactam Susceptibility

Author

Southon, Sara B., primary, Beres, Stephen B., additional, Kachroo, Priyanka, additional, Saavedra, Matthew Ojeda, additional, Erlendsdóttir, Helga, additional, Haraldsson, Gunnsteinn, additional, Yerramilli, Prasanti, additional, Pruitt, Layne, additional, Zhu, Luchang, additional, Musser, James M., additional, and Kristinsson, Karl G., additional

Published
2020
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11. Reduced In Vitro Susceptibility of Streptococcus pyogenes to β-Lactam Antibiotics Associated with Mutations in the pbp2x Gene Is Geographically Widespread

Author

Musser, James M., primary, Beres, Stephen B., additional, Zhu, Luchang, additional, Olsen, Randall J., additional, Vuopio, Jaana, additional, Hyyryläinen, Hanne-Leena, additional, Gröndahl-Yli-Hannuksela, Kirsi, additional, Kristinsson, Karl G., additional, Darenberg, Jessica, additional, Henriques-Normark, Birgitta, additional, Hoffmann, Steen, additional, Caugant, Dominque A., additional, Smith, Andrew J., additional, Lindsay, Diane S. J., additional, Boragine, David M., additional, and Palzkill, Timothy, additional

Published
2020
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12. The serotype of type Ia and III group B streptococci is determined by the polymerasxe gene within the polycistronic capsule operon

Author

Chaffin, Donald O., Beres, Stephen B., Yim, Harry H., and Rubens, Craig E.

Subjects
Streptococcus agalactiae -- Genetic aspects, Microbial polysaccharides -- Physiological aspects, Immunospecificity -- Analysis, Genetic regulation -- Analysis, Biological sciences
Abstract

Results show that cpsIaH and cpsIIIH genes encode Ia and III capsular polysaccharide polymerases respectively, leading to the synthesis of type-specific capsular polysaccharides. Data point out that these polysaccharides aid in host immune defence mechanism in Streptococcus agalactiae.

Published
2000

16. Genomic Landscape of Intrahost Variation in Group A Streptococcus: Repeated and Abundant Mutational Inactivation of the fabT Gene Encoding a Regulator of Fatty Acid Synthesis

Author

Eraso, Jesus M., primary, Olsen, Randall J., additional, Beres, Stephen B., additional, Kachroo, Priyanka, additional, Porter, Adeline R., additional, Nasser, Waleed, additional, Bernard, Paul E., additional, DeLeo, Frank R., additional, and Musser, James M., additional

Published
2016
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17. Transcriptome Remodeling Contributes to Epidemic Disease Caused by the Human Pathogen Streptococcus pyogenes

Author

Beres, Stephen B., primary, Kachroo, Priyanka, additional, Nasser, Waleed, additional, Olsen, Randall J., additional, Zhu, Luchang, additional, Flores, Anthony R., additional, de la Riva, Ivan, additional, Paez-Mayorga, Jesus, additional, Jimenez, Francisco E., additional, Cantu, Concepcion, additional, Vuopio, Jaana, additional, Jalava, Jari, additional, Kristinsson, Karl G., additional, Gottfredsson, Magnus, additional, Corander, Jukka, additional, Fittipaldi, Nahuel, additional, Di Luca, Maria Chiara, additional, Petrelli, Dezemona, additional, Vitali, Luca A., additional, Raiford, Annessa, additional, Jenkins, Leslie, additional, and Musser, James M., additional

Published
2016
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18. The Majority of 9,729 Group A Streptococcus Strains Causing Disease Secrete SpeB Cysteine Protease: Pathogenesis Implications

Author

Olsen, Randall J., primary, Raghuram, Anjali, additional, Cantu, Concepcion, additional, Hartman, Meredith H., additional, Jimenez, Francisco E., additional, Lee, Susan, additional, Ngo, Ashley, additional, Rice, Kelsey A., additional, Saddington, Deborah, additional, Spillman, Hannaka, additional, Valson, Chandni, additional, Flores, Anthony R., additional, Beres, Stephen B., additional, Long, S. Wesley, additional, Nasser, Waleed, additional, and Musser, James M., additional

Published
2015
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20. Clinical Laboratory Response to a Mock Outbreak of Invasive Bacterial Infections: a Preparedness Study

Author

Olsen, Randall J., primary, Fittipaldi, Nahuel, additional, Kachroo, Priyanka, additional, Sanson, Misu A., additional, Long, S. Wesley, additional, Como-Sabetti, Kathryn J., additional, Valson, Chandni, additional, Cantu, Concepcion, additional, Lynfield, Ruth, additional, Van Beneden, Chris, additional, Beres, Stephen B., additional, and Musser, James M., additional

Published
2014
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28. In Vitro Serial Passage of Staphylococcus aureus: Changes in Physiology, Virulence Factor Production,a nd agr Nucleotide Sequence.

Author

Somerville, Greg A., Beres, Stephen B., Fitzgerald, J. Ross, DeLeo, Frank R., Cole, Robert L., Hoff, Jessica S., and Musser, James M.

Subjects
*PHENOTYPES, *STAPHYLOCOCCUS aureus, *GENES
Abstract

Examines the phenotypic and genotypic changes of Staphylococcus aureus during in vitro serial passage. Presence of aconitase activity in S. coccus strains; Influence of in vitro passage on acotinase specific activity; Regulation of beta-hemolytic activity by cell density-sensing accessory gene regulatory.

Published
2002
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29. Genetic Basis Underlying the Hyperhemolytic Phenotype of Streptococcus agalactiae Strain CNCTC10/84.

Author

Luchang Zhu, Beres, Stephen B., Yerramilli, Prasanti, Pruitt, Layne, Cantu, Concepcion C., Olsen, Randall J., and Musser, James M.

Abstract

Streptococcus agalactiae (group B streptococcus [GBS]) is a major cause of infections in newborns, pregnant women, and immunocompromised patients. GBS strain CNCTC10/84 is a clinical isolate that has high virulence in animal models of infection and has been used extensively to study GBS pathogenesis. Two unusual features of this strain are hyperhemolytic activity and hypo-CAMP factor activity. These two phenotypes are typical of GBS strains that are functionally deficient in the CovR-CovS two-component regulatory system. A previous whole-genome sequencing study found that strain CNCTC10/84 has intact covR and covS regulatory genes. We investigated CovR-CovS regulation in CNCTC10/84 and discovered that a single-nucleotide insertion in a homopolymeric tract in the covR promoter region underlies the strong hemolytic activity and weak CAMP activity of this strain. Using isogenic mutant strains, we demonstrate that this single-nucleotide insertion confers significantly decreased expression of covR and covS and altered expression of CovR-CovS-regulated genes, including that of genes encoding ß-hemolysin and CAMP factor. This single-nucleotide insertion also confers significantly increased GBS survival in human whole blood ex vivo. [ABSTRACT FROM AUTHOR]

Published
2020
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30. Genome-Wide Transposon Mutagenesis Screens Identify Group A Streptococcus Genes Affecting Susceptibility to ß-Lactam Antibiotics.

Author

Luchang Zhu, Eraso, Jesus M., Mangham, Regan E., Saavedra, Matthew Ojeda, Olsen, Randall J., Beres, Stephen B., and Musser, James M.

Abstract

Group A streptococcus (GAS) is a Gram-positive human bacterial pathogen responsible for more than 700 million infections annually worldwide. Beta-lactam antibiotics are the primary agents used to treat GAS infections. Naturally occurring GAS clinical isolates with decreased susceptibility to beta-lactam antibiotics attributed to mutations in PBP2X have recently been documented. This prompted us to perform a genome-wide screen to identify GAS genes that alter beta-lactam susceptibility in vitro. Using saturated transposon mutagenesis, we screened for GAS gene mutations conferring altered in vitro susceptibility to penicillin G and/or ceftriaxone, two beta-lactam antibiotics commonly used to treat GAS infections. In the aggregate, we found that inactivating mutations in 150 GAS genes are associated with altered susceptibility to penicillin G and/or ceftriaxone. Many of the genes identified were previously not known to alter beta-lactam susceptibility or affect cell wall biosynthesis. Using isogenic mutant strains, we confirmed that inactivation of clpX (Clp protease ATP-binding subunit) or cppA (CppA proteinase) resulted in decreased in vitro susceptibility to penicillin G and ceftriaxone. Deletion of murA1 (UDP-N-acetylglucosamine 1-carboxyvinyltransferase) conferred increased susceptibility to ceftriaxone. Our results provide new information about the GAS genes affecting susceptibility to beta-lactam antibiotics. [ABSTRACT FROM AUTHOR]

Published
2022
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31. Functional Insights into the High-Molecular-Mass Penicillin-Binding Proteins of Streptococcus agalactiae Revealed by Gene Deletion and Transposon Mutagenesis Analysis.

Author

Luchang Zhu, Yerramilli, Prasanti, Pruitt, Layne, Mishra, Abhishek, Olsen, Randall J., Beres, Stephen B., Waller, Andrew S., and Musser, James M.

Abstract

High-molecular-mass penicillin-binding proteins (PBPs) are enzymes that catalyze the biosynthesis of bacterial cell wall peptidoglycan. The Gram-positive bacterial pathogen Streptococcus agalactiae (group B streptococcus [GBS]) produces five high-molecular-mass PBPs, namely, PBP1A, PBP1B, PBP2A, PBP2B, and PBP2X. Among these, only PBP2X is essential for cell viability, whereas the other four PBPs are individually dispensable. The biological function of the four nonessential PBPs is poorly characterized in GBS. We deleted the pbp1a, pbp1b, pbp2a, and pbp2b genes individually from a genetically well-characterized serotype V GBS strain and studied the phenotypes of the four isogenic mutant strains. Compared to the wild-type parental strain, (i) none of the pbp isogenic mutant strains had a significant growth defect in Todd-Hewitt broth supplemented with 0.2% yeast extract (THY) rich medium, (ii) isogenic mutant Δpbp1a and Δpbp1b strains had significantly increased susceptibility to penicillin and ampicillin, and (iii) isogenic mutant Δpbp1a and Δpbp2b strains had significantly longer chain lengths. Using saturated transposon mutagenesis and transposon insertion site sequencing, we determined the genes essential for the viability of the wild-type GBS strain and each of the four isogenic pbp deletion mutant strains in THY rich medium. The pbp1a gene is essential for cell viability in the pbp2b deletion background. Reciprocally, pbp2b is essential in the pbp1a deletion background. Moreover, the gene encoding RodA, a peptidoglycan polymerase that works in conjunction with PBP2B, is also essential in the pbp1a deletion background. Together, our results suggest functional overlap between PBP1A and the PBP2B-RodA complex in GBS cell wall peptidoglycan biosynthesis. [ABSTRACT FROM AUTHOR]

Published
2021
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