Skip Navigation LinksHome > March 2014 - Volume 22 - Issue 2 > USA600 Methicillin–Resistant Staphylococcus aureus in ICU Pa...
Infectious Diseases in Clinical Practice:
doi: 10.1097/IPC.0b013e318298b81c
Original Articles

USA600 Methicillin–Resistant Staphylococcus aureus in ICU Patients With Pneumonia: A Case-Control Study Design to Evaluate Epidemiology and Outcomes of an Emerging Strain

Arshad, Samia MPH*; Shoyinka, Adenike MD*; Perri, Mary-Beth MT*; Moreno, Daniela MS*; Jacobsen, Gordon MS*; Zervos, Marcus J. MD*† ; and On behalf of the IMPACT-HAP Study Group

Collapse Box

Abstract

Background

Methicillin-resistant Staphylococcus aureus (MRSA) infections are associated with severe necrotizing syndromes and high mortality, accounting for 20% to 40% of all hospital-acquired pneumonia and ventilator-associated pneumonia. There is insufficient data on comparative outcomes by specific strain characteristics in MRSA isolates in patients with pneumonia.

Methods

Clinical outcomes of patients with USA600 (ST45) MRSA strain were compared with other sequence types in MRSA pneumonia from 5 different hospitals in a retrospective case-control study. Patients were identified through review of microbiology laboratory records and through the Improving Medicine through Pathway Assessment of Critical Therapy in Hospital-Acquired Pneumonia database. Pulsed-field gel electrophoresis of SmaI-digested genomic DNA was performed on all isolates using a CHEF-DR III (BioRad). Pulsed-field gel electrophoresis patterns were compared using BioNumerics software (Applied Maths).

Results

Two hundred fifty-one consecutive patients with MRSA pneumonia were evaluable for an all-cause 28-day mortality and 14-day failure outcome. Prevalence of USA600 was 8% (21). Laboratory characteristics of USA600 isolates were 100% (21) Panton-Valentine leukocidin toxin negative, agr I type, 67% (14) heteroresistant to vancomycin, and higher rates of SCCmec type II versus SCCmec type IVa, 95% versus 5%. Twenty-eight–day mortality rates were USA600 (52.4%), USA100 (ST5; 29%), and USA300 (ST8; 32%); and 14-day failure rates were USA600 (50%), USA100 (37%), and USA300 (27%), respectively.

Conclusions

This is the first comparative observational study of its kind, with evidence of a much higher failure rate (>50%) within patients with USA600 MRSA pneumonia. The high mortality rate in this subset warrants further investigation of factors of this emerging strain that may predict mortality and failure outcomes.

Copyright © 2014 by Lippincott Williams & Wilkins

Search for Similar Articles
You may search for similar articles that contain these same keywords or you may modify the keyword list to augment your search.