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Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)
12:18

Subcutaneous Infection of Methicillin Resistant Staphylococcus Aureus (MRSA)

Published on: February 9, 2011

Methicillin-resistant Staphylococcus aureus nasal carriage among injection drug users: six years later

G N Al-Rawahi1, A G Schreader, S D Porter

  • 1Department of Pathology and Laboratory Medicine, University of British Columbia, Vancouver, British Columbia, Canada.

Journal of Clinical Microbiology
|November 28, 2007
PubMed

Insights

Methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization significantly increased among injection drug users in Vancouver. The prevalent USA-300 strain is largely Panton-Valentine leukocidin (PVL)-positive and remains susceptible to trimethoprim-sulfamethoxazole (TMP-SMX).

Area of Science:

  • Microbiology
  • Epidemiology
  • Public Health

Background:

  • A 2000 survey found 7.4% MRSA nasal colonization in Vancouver injection drug users (IDUs).
  • Methicillin-resistant Staphylococcus aureus (MRSA) poses a significant public health threat, particularly in vulnerable populations.
  • Understanding current MRSA prevalence and characteristics in IDUs is crucial for targeted interventions.

Purpose of the Study:

  • To determine the current prevalence of MRSA nasal carriage among Vancouver IDUs.
  • To characterize MRSA isolates, including antimicrobial susceptibility and virulence factors.
  • To identify risk factors associated with MRSA colonization in this population.

Main Methods:

  • A point prevalence study involving nasal swab cultures from IDUs.
  • Antimicrobial susceptibility testing of isolated Staphylococcus aureus strains.
  • Detection of mecA and Panton-Valentine leukocidin (PVL) genes.
  • Pulsed-field gel electrophoresis (PFGE) for strain typing.

Main Results:

  • Staphylococcus aureus was isolated from 39.5% of participants; 18.6% had MRSA.
  • The USA-300 strain (CMRSA-10) predominated (75% of MRSA), replacing USA-500 (CMRSA-5).
  • Most USA-300 isolates (97.6%) were PVL-positive, while USA-500 isolates were PVL-negative.
  • USA-300 isolates showed higher susceptibility to trimethoprim-sulfamethoxazole (TMP-SMX) (100%) and clindamycin (54.8%) compared to USA-500.

Conclusions:

  • MRSA nasal colonization has significantly increased in Vancouver IDUs since 2000.
  • The USA-300 strain, often PVL-positive, is now the dominant MRSA strain in this population.
  • While MRSA strains remain susceptible to TMP-SMX, the high prevalence of PVL warrants continued surveillance and targeted prevention strategies.

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