Involvement of multiple genetic determinants in high-level methicillin resistance in Staphylococcus aureus

Murakami, Kazuhisa; Tomasz, Alexander

doi:10.1128/jb.171.2.874-879.1989

Cited by 155 publications

(129 citation statements)

References 23 publications

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“…The complete deletion of psr could remove the stronger promoter but also other sequences in the ORF or downstream of the ORF which might contribute to attenuation of pbp5 gene transcription. Regulation of PBP expression by genetic elements has also been reported to occur in E. coli (2,31) and in methicillinresistant staphylococci (3,19,25,26), but the mechanism by which such control is exerted has not been elucidated. In E. coli, the synthesis of PBPs lb and 3 appears to be negatively controlled by mre genes, which are located at a distance of 60 min from these PBP genes in the chromosome map (31), whereas overproduction of PBPs 2 and 5 is caused by mutation in the rodA gene, which is located in the same operon as these PBP genes (2).…”

Section: Resultsmentioning

confidence: 99%

Identification of a genetic element (psr) which negatively controls expression of Enterococcus hirae penicillin-binding protein 5

1993

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Enterococcus hirae ATCC 9790 produces a penicillin-binding protein (PBP5) of low penicillin affinity which under certain conditions can take over the functions of all the other PBPs. The 7.1-kb EcoRI fragment containing the pbp5 gene of this strain and of two mutants, of which one (E. hirae R40) overproduces PBP5 and the other (E. hirae Revl4) does not produce PBP5, was cloned in pUC18 and sequenced. In (4,7,12,23,30). These PBPs share several properties: they can be produced by the cells in large amounts, have similar molecular masses (about 75,000 Da), have an unusually low affinity for beta-lactam antibiotics, and play an important role in the mechanism of resistance to these antibiotics in enterococci and staphylococci.In enterococci, the low-affinity PBPs either are components of the normal PBP pattern or are generated by mutations in genes of the normal PBPs (1,12,21,32,33), whereas in staphylococci their synthesis is due to the acquisition of an additional gene (mec) which is practically identical in Staphylococcus aureus and several coagulase-negative species (22,27,29).In contrast to the evident and well-documented role of the low-affinity PBPs in the mechanism of resistance of grampositive cocci to beta-lactam antibiotics, very little is known about the role these proteins play in cell physiology. The most accepted hypothesis is that these proteins are multifunctional PBPs which are not essential for cell growth, at least under laboratory conditions, and can synthesize peptidoglycans under conditions which impair the activity of the other PBPs (4-6, 12, 13). Such an alternative system of peptidoglycan synthesis would represent an interesting and novel aspect of bacterial physiology.Previous studies of the low-affinity PBP of Enterococcus hirae ATCC 9790 (PBP5) based on mutants with a cell division defect and mutants with altered synthesis (either overproduction or lack) of PBP5 have elucidated certain aspects of the role of low-affinity PBPs in cell physiology (5, * Corresponding author. 6, 12, 13). Recently, the E. hirae PBP5-encoding gene (pbp5) has been cloned and sequenced (9), thus making possible investigations into the function of this PBP by a genetic approach.In this study, we sequenced the 7.1-kb EcoRI fragment, containing thepbp5 gene, cloned from chromosomal DNA of the wild-type E. hirae ATCC 9790, the PBP5 overproducer mutant E. hirae R40, and the PBP5 nonproducer mutant E. hirae Revl4. We found that the overproducer phenotype was associated with an 87-bp deletion in a genetic element, which we calledpsr (PBP5 synthesis repressor), located 1 kb upstream of the pbp5 gene, whereas the lack of PBP5 synthesis in E. hirae Revl4 was found to be caused by a nucleotide substitution in the coding frame of the protein which converted the 42nd codon, TCA, to the stop codon, TAA. MATERIALS AND METHODSBacterial strains and plasmids. The relevant properties of E. hirae strains and the recombinant plasmids constructed in this study are listed in Table 1. E. hirae strains were grown in brain heart infu...

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Section: Resultsmentioning

confidence: 99%

Identification of a genetic element (psr) which negatively controls expression of Enterococcus hirae penicillin-binding protein 5

1993

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“…Many studies have used randomly generated mutants of methicillin-resistant S. aureus (MRSA) strains that demonstrate a reduction in the methicillin MIC, followed by biochemical analysis, to define the genes linked to cell wall biosynthesis (65,66,164,217). A large number of genes appear to be involved in staphylococcal cell wall precursor production (66).…”

Section: Understanding Vancomycin Resistance: the Staphylococcal Cellmentioning

confidence: 99%

Reduced Vancomycin Susceptibility inStaphylococcus aureus, Including Vancomycin-Intermediate and Heterogeneous Vancomycin-Intermediate Strains: Resistance Mechanisms, Laboratory Detection, and Clinical Implications

et al. 2010

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SUMMARY The emergence of vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) over the past decade has provided a challenge to diagnostic microbiologists to detect these strains, clinicians treating patients with infections due to these strains, and researchers attempting to understand the resistance mechanisms. Recent data show that these strains have been detected globally and in many cases are associated with glycopeptide treatment failure; however, more rigorous clinical studies are required to clearly define the contribution of hVISA to glycopeptide treatment outcomes. It is now becoming clear that sequential point mutations in key global regulatory genes contribute to the hVISA and VISA phenotypes, which are associated predominately with cell wall thickening and restricted vancomycin access to its site of activity in the division septum; however, the phenotypic features of these strains can vary because the mutations leading to resistance can vary. Interestingly, changes in the staphylococcal surface and expression of agr are likely to impact host-pathogen interactions in hVISA and VISA infections. Given the subtleties of vancomycin susceptibility testing against S. aureus, it is imperative that diagnostic laboratories use well-standardized methods and have a framework for detecting reduced vancomycin susceptibility in S. aureus.

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“…A comienzos de los años 1980 se observó que si bien todas las células de MRSA en una población dada poseían el gen mecA, la CIM de meticilina variaba desde unos pocos microgramos por mililitro por encima del punto de corte de susceptibilidad hasta niveles cientos de veces más altos, hecho que se atribuye a la expresión diferencial de otros determinantes genéticos involucrados en la resistencia, tales como el gen femA (51). Se postula que el uso de carbapenems y cefalosporinas de tercera generación para tratar estas cepas MRSA heterogéneas, que al principio aparecían susceptibles, condujo a la selección de las subpoblaciones más resistentes y al predominio de MRSA homogéneo (52).…”

Section: Resistencia Intermedia Heterogénea a Vancomicina: Cepas Hvisaunclassified

Staphylococcus aureus resistente a vancomicina.

Rodríguez¹,

Vesga

2005

biomedica

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Objetivo. Revisar la evolución y mecanismos moleculares de la resistencia de Staphylococcus aureus a vancomicina. Fuente de los datos. Se consultó la base de datos MEDLINE y se seleccionaron artículos tipo reportes de caso, estudios bioquímicos, de microscopía electrónica y biología molecular pertinentes. Síntesis. Después de casi 40 años de eficacia ininterrumpida de la vancomicina, en 1997 se reportaron los primeros casos de fracaso terapéutico debido a cepas de Staphylococcus aureus con resistencia intermedia, denominadas VISA (concentración inhibitoria mínima, CIM, 8 a 16 µg/ml), así como a cepas con resistencia heterogénea hVISA (CIM global = 4 µg/ml, pero con subpoblaciones VISA), en las cuales la resistencia está mediada por engrosamiento de la pared celular y disminución de su entrecruzamiento, lo que afecta la llegada del antibiótico al blanco principal, los monómeros del peptidoglicano en la membrana plasmática. En 2002 se aisló la primera de las 3 cepas reportadas hasta la fecha con resistencia total al antibiótico, denominadas VRSA (CIM>32 µg/ml), en las que se encontró el transposón Tn1546 proveniente de Enterococcus spp, responsable del reemplazo de la terminación D-Ala-D-Ala por D-Ala-Dlactato en los precursores de la pared celular con pérdida de la afinidad por el glicopéptido. Conclusiones. La resistencia a vancomicina es una realidad en S. aureus, mediada en el caso de VISA por alteraciones en la pared celular que atrapan el antibiótico antes de llegar al sitio de acción, y en el caso de VRSA, por transferencia desde Enterococcus spp. de genes que llevan a la modificación del blanco molecular.Palabras clave: Staphylococcus aureus, peptidoglicano, biosíntesis, antibióticos glicopéptidos, vancomicina, resistencia microbiana a drogas, resistencia a vancomicina. Vancomycin-resistant Staphylococcus aureusThe evolution and molecular mechanisms of vancomycin resistance in Staphylococcus aureus were reviewed. Case reports and research studies on biochemestry, electron microscopy and molecular biology of Staphylococcus aureus were selected from Medline database and summarized in the following review. After almost 40 years of successful treatment of S. aureus with vancomycin, several cases of clinical failures have been reported (since 1997). S. aureus strains have appeared with intermediate susceptibility (MIC 8-16 µg/ml), as well as strains with heterogeneous resistance (global MIC ≤ 4 µg/ml), but with subpopulations of intermediate susceptibility. In these cases, resistance is mediated by cell wall thickening with reduced cross linking. This traps the antibiotic before it reaches its major target, the murein monomers in the cell membrane. In 2002, a total vancomycin resistant strain (MIC ≥ 32 µg/ml) was reported with vanA genes from Enterococcus spp. These genes induce the change of D-Ala-D-Ala terminus for D-Ala-D-lactate in the cell wall precursors, leading to loss of affinity for glycopeptides. Vancomycin resistance in S. aureus has appeared; it is mediated by cell wall modifications that trap the ...

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Involvement of multiple genetic determinants in high-level methicillin resistance in Staphylococcus aureus

Cited by 155 publications

References 23 publications

Identification of a genetic element (psr) which negatively controls expression of Enterococcus hirae penicillin-binding protein 5

Identification of a genetic element (psr) which negatively controls expression of Enterococcus hirae penicillin-binding protein 5

Reduced Vancomycin Susceptibility inStaphylococcus aureus, Including Vancomycin-Intermediate and Heterogeneous Vancomycin-Intermediate Strains: Resistance Mechanisms, Laboratory Detection, and Clinical Implications

Staphylococcus aureus resistente a vancomicina.

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