Glycopeptide resistance in Staphylococcus aureus: is it a real threat?

Gemmell, C. G.

doi:10.1007/s10156-004-0307-5

Cited by 39 publications

(20 citation statements)

References 46 publications

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“…The data are representative of two separate experiments (SEM ,6 % for each). MSSA strains (Gemmell, 2004). Our findings with ATCC strains of MRSA and MSSA and the hVISA strains isolated from our patients further confirm that glycopeptide resistance and cell-wall thickening do not result in altered opsonophagocytosis and killing in the presence of a high concentration (10 %) of serum.…”

Section: Discussionsupporting

confidence: 84%

Phagocytosis and intracellular killing of heterogeneous vancomycin-intermediate Staphylococcus aureus strains

Méhes

Taskó

Székely

et al. 2012

Journal of Medical Microbiology

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Section: Discussionsupporting

confidence: 84%

Phagocytosis and intracellular killing of heterogeneous vancomycin-intermediate Staphylococcus aureus strains

Méhes

Taskó

Székely

et al. 2012

Journal of Medical Microbiology

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“…After the first reports of VISA and hVISA from Japan, it did not take long for this resistance phenotype to be recognized around the world. Strains of S. aureus (predominately MRSA) demonstrating the hVISA or VISA phenotype have now been reported for many countries including the United States, Japan, Australia, France, Scotland, Brazil, South Korea, Hong Kong, South Africa, Thailand, Israel, and others (22,67,69,77,79,82,94,158,167,194,195,206,258,284,300,326,327,331,352,354,366,373). A retrospective analysis of stored isolates detected previously unrecognized hVISA/VISA strains at least back to 1987 in the United States and back to a similar period in France, Spain, and Germany (11,22,39,276,288); however, there has been some concern about the potential loss of resistance during prolonged storage, which could impact results of such retrospective analyses.…”

Section: Global Epidemiology and Associated Features Of Hvisa And Visamentioning

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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“…While some microbiology, infectious disease, and public health personnel have focused concern on VISA and vancomycin-resistant S. aureus characterized as such by conventional test methods, others consider the in vitro phenomenon of unstable vancomycin heteroresistance an explanation for the therapeutic failure of vancomycin in humans (1,3,4,7,11,14,17). Further evidence is needed to confirm this association, since not all patients harboring unstably hetero-VISA strains fail therapy.…”

Section: Downloaded Frommentioning

confidence: 99%

Unstable Vancomycin Heteroresistance Is Common among Clinical Isolates of Methiciliin-Resistant Staphylococcus aureus

et al. 2005

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We tested 109 unique, vancomycin-susceptible, methicillin-resistant Staphylococcus aureus (MRSA) strains for vancomycin heteroresistance by a selection method, i.e., step-wise exposure of large inoculums to increasing concentrations of vancomycin. Although no strains demonstrated stable heteroresistance, 81 strains (74%) demonstrated unstable heteroresistance. Unstable heteroresistance is common among clinical isolates of MRSA and may represent a cause of therapeutic failure.Heteroresistant vancomycin-intermediate Staphylococcus aureus (hetero-VISA) strains are those for which MICs are conventional (Յ4 g/ml) except when high-density inocula are used; with such inocula, there are minority subpopulations for which MICs are in the intermediate range (8 to 16 g/ml) (13). The detection of hetero-VISA requires inocula containing Ͼ10 6 total bacterial cells, since resistant clones can occur infrequently, being perhaps 1 in 1,000,000 (15). The MICs for the selected, stably heteroresistant clones are conventional, in the 4-to 8-g/ml range (7,17). In addition, unstable heteroresistance can be detected (12, 13). S. aureus clones demonstrating unstable heteroresistance grow in the presence of high concentrations of vancomycin (Ͼ4 g/ml), as shown by step-wise exposure of large inoculums to increasing levels of drug, though conventional MICs for such clones are not elevated; i.e., nonsusceptible clones rapidly revert to normal phenotypes. Unstably hetero-VISA is not detected by usual laboratory antimicrobial tests. Our study was designed to determine the frequency of stable and unstable heteroresistance to vancomycin among unselected methicillin-resistant Staphylococcus aureus (MRSA) strains from adult and pediatric patients at two Chicago tertiary care hospitals.Altogether, 109 MRSA strains from unique patients were randomly collected over a 1-year period, from 15 December 1998 to 14 December 1999. A total of 69 strains were from Evanston Northwestern Healthcare (two adult hospitals), and 40 strains were from the Children's Memorial Hospital.All catalase-positive, gram-positive cocci in clusters were identified as MRSA by yielding positive results in an agglutination test for coagulase/protein A (Murex Biotech Ltd., Dartford, United Kingdom) and growing on 6-g/ml oxacillin agar screening plates (Remel, Lenexa, Kans.). Vancomycin MIC testing was performed on the original unselected strains and the corresponding selected MRSA strains that grew on screening plates containing Ն16 g/ml of vancomycin. MIC testing was performed with Microscan Pos MIC panels (Dade Behring, West Sacramento, Calif.) according to NCCLS methods (10). All panels were read after 24 h of incubation and, for all induced strains, again after 48 h.MRSA strains were subcultured onto 5% sheep blood agar plates and incubated overnight at 35°C. A 0.1-ml sample from a McFarland 2.0 suspension in saline taken from overnight growth was spread evenly on brain heart infusion (BHI) agar containing 2-g/ml vancomycin (Sigma Chemical Co., St. Louis, Mo.) and 4% NaCl, and ...

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Glycopeptide resistance in Staphylococcus aureus: is it a real threat?

Cited by 39 publications

References 46 publications

Phagocytosis and intracellular killing of heterogeneous vancomycin-intermediate Staphylococcus aureus strains

Phagocytosis and intracellular killing of heterogeneous vancomycin-intermediate Staphylococcus aureus strains

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

Unstable Vancomycin Heteroresistance Is Common among Clinical Isolates of Methiciliin-Resistant Staphylococcus aureus

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