Vancomycin-resistant Staphylococcus aureus

Source: Wikipedia, the free encyclopedia.
Vancomycin-resistant Staphylococcus aureus
Scanning electron micrograph (SEM) shows a strain of Staphylococcus aureus bacteria taken from a vancomycin-intermediate Staphylococcus aureus (VISA) culture.
SpecialtyMicrobiology
Diagnostic methodDisk diffusion[1]
TreatmentBeta-lactam antibiotic (in combination)[2]

Vancomycin-resistant Staphylococcus aureus (VRSA) are strains of Staphylococcus aureus that have acquired resistance to the glycopeptide antibiotic vancomycin.[3] Bacteria can acquire resistant genes either by random mutation or through the transfer of DNA from one bacterium to another. Resistance genes interfere with the normal antibiotic function and allow a bacteria to grow in the presence of the antibiotic.[4] Resistance in VRSA is conferred by the plasmid-mediated vanA gene and operon.[5] Although VRSA infections are uncommon, VRSA is often resistant to other types of antibiotics and a potential threat to public health because treatment options are limited.[6] VRSA is resistant to many of the standard drugs used to treat S. aureus infections. Furthermore, resistance can be transferred from one bacterium to another.[5]

Mechanism of acquired resistance

Vancomycin-resistant Staphylococcus aureus was first reported in the United States in 2002.[5] To date, documented cases of VRSA have acquired resistance through uptake of a vancomycin resistance gene cluster from Enterococcus (i.e. VRE).[7] The acquired mechanism is typically the vanA gene and operon from a plasmid in Enterococcus faecium or Enterococcus faecalis.[5]

This mechanism differs from strains of vancomycin-intermediate Staphylococcus aureus (VISA), which appear to develop elevated MICs to vancomycin through sequential mutations resulting in a thicker cell wall and the synthesis of excess amounts of D-ala-D-ala residues.[8]

Diagnosis

The diagnosis of vancomycin-resistant Staphylococcus aureus (VRSA) is performed by performing susceptibility testing on a single S. aureus isolate to vancomycin. This is accomplished by first assessing the isolate's minimum inhibitory concentration (MIC) using standard laboratory methods, including disc diffusion, gradient strip diffusion, and automated antimicrobial susceptibility testing systems.[1] Once the MIC is known, resistance is determined by comparing the MIC with established breakpoints [9]

Resistant or "R" designations are assigned based on agreed upon values called breakpoints. Breakpoints are published by standards development organizations such as the U.S. Clinical and Laboratory Standards Institute, the British Society for Antimicrobial Chemotherapy and the European Committee on Antimicrobial Susceptiblity Testing.

Treatment of infection

Rifampicin (Rifampin)

When the

beta-lactam antibiotic).[2]

History

Three classes of vancomycin-resistant S. aureus have emerged that differ in vancomycin susceptibilities: vancomycin-intermediate S. aureus (VISA), heterogeneous vancomycin-intermediate S. aureus (hVISA), and high-level vancomycin-resistant S. aureus (VRSA).[10]

Vancomycin-intermediate S. aureus (VISA)

Vancomycin-intermediate S. aureus (VISA) (

the United Kingdom, France, the U.S., and Brazil. It is also termed GISA (glycopeptide-intermediate Staphylococcus aureus), indicating resistance to all glycopeptide antibiotics. These bacterial strains present a thickening of the cell wall, which is believed to reduce the ability of vancomycin to diffuse into the division septum of the cell required for effective vancomycin treatment.[12]

blood agar

Vancomycin-resistant S. aureus (VRSA)

High-level vancomycin resistance in S. aureus has been rarely reported.

transposon located on a plasmid carried by the VRSA isolate. This transposon, Tn1546, confers vanA-type vancomycin resistance in enterococci.[16]

As of 2019, 52 VRSA strains have been identified in the United States, India, Iran, Pakistan, Brazil, and Portugal.[17]

Heterogeneous vancomycin-intermediate S. aureus (hVISA)

The definition of hVISA according to Hiramatsu et al. is a strain of Staphylococcus aureus that gives resistance to vancomycin at a frequency of 10−6 colonies or even higher.[18]

See also

References

  1. ^
    PMID 20927290
    .
  2. ^
    PMID 21208910
    .
  3. ^ "CDC - VISA / VRSA in Healthcare Settings - HAI". www.cdc.gov. Retrieved 2015-06-11.
  4. PMID 29259602
    .
  5. ^
    PMID 28656013
    .
  6. PMID 32071785
    .
  7. PMID 12672861
    .
  8. PMID 20065327
    .
  9. ^ CLSI (2023). M100 Performance Standards for Antimicrobial Susceptibility Standards (Report) (33 ed.). Wayne PA: Clinical and Laboratory Standards Institute. p. 8.
  10. PMID 17888634
    .
  11. PMID 9249217
    .
  12. PMID 20065327
    .
  13. PMID 21109164
    .
  14. ISBN 9781908230287
    .
  15. ISBN 9781904933243
    .
  16. PMID 16323116
    .
  17. PMID 32071785
    .
  18. ISBN 9780387757216
    .

Further reading

External links
Scholia has a topic profile for Vancomycin-resistant Staphylococcus aureus.
Retrieved from "https://en.wikipedia.org/w/index.php?title=Vancomycin-resistant_Staphylococcus_aureus&oldid=1211471958"