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Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria
14:04

Biosensor for Detection of Antibiotic Resistant Staphylococcus Bacteria

Published on: May 8, 2013

Effect of duplicate isolates of methicillin-susceptible and methicillin-resistant Staphylococcus aureus on

Rebecca T Horvat1, Neil E Klutman, Melinda K Lacy

  • 1Department of Pathology and Laboratory Medicine, University of Kansas, Kansas City, Kansas 66160, USA. rhorvat@kumc.edu

Journal of Clinical Microbiology
|October 9, 2003
PubMed

Insights

Duplicate Staphylococcus aureus isolates significantly impact annual antimicrobial resistance data. Removing duplicate isolates from methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA) analyses reveals different infection rates.

Area of Science:

  • Microbiology
  • Infectious Diseases
  • Clinical Pharmacy

Background:

  • Accurate antimicrobial resistance surveillance is crucial for effective treatment strategies.
  • Duplicate isolates from the same patient can skew annual antibiogram data, potentially misrepresenting true resistance rates.
  • Understanding the prevalence and impact of duplicate Staphylococcus aureus isolates is essential for refining epidemiological studies.

Purpose of the Study:

  • To determine the impact of multiple Staphylococcus aureus isolates from individual patients on annual antibiogram data.
  • To evaluate how duplicate isolates affect the calculated rates of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible Staphylococcus aureus (MSSA).

Main Methods:

  • Analysis of 4,844 Staphylococcus aureus isolates from 3,227 patients over a 6-year period (1996-2001).
  • Comparison of annual MRSA and MSSA rates calculated with and without duplicate isolates.
  • Evaluation of isolate ratios per patient (>1.0 indicates duplicates) and comparison of phenotypic antibiogram patterns for duplicate MRSA isolates.

Main Results:

  • 39% of MRSA and 23% of MSSA patients had duplicate isolates.
  • 91% of patients with duplicate isolates retained the same strain type (MRSA or MSSA).
  • MRSA rates differed significantly (P < 0.05) in 4 out of 6 years when duplicate isolates were removed. The 6-year MRSA ratio was 1.90 isolates/patient, and MSSA was 1.35.
  • 88% of patients with duplicate MRSA isolates had phenotypically identical isolates.

Conclusions:

  • Duplicate Staphylococcus aureus isolates can alter perceived annual antimicrobial resistance rates.
  • Excluding duplicate isolates provides a more accurate representation of MRSA and MSSA prevalence.
  • Antimicrobial resistance surveillance methodologies should account for duplicate isolates to ensure data integrity.

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