The relationship between MRSA pneumonia mortality and serum levels of vancomycin, vancomycin minimum inhibitory concentration

WANG Ying; LIU Ying-yu; HAO Ying-yan

doi:10.3969/j.issn.1002-1949.2016.06.015

Abstract：Objective To investigate the relationship between molecular markers such as the Agr Ⅱ genes, serum vancomycin levels and vancomycin minimum inhibitory concentration ( MIC) , and the 30 - day mortality rate of patients with nosocomial methicillin - resistant Staphylococcus aureus (MRSA) pneumonia in an intensive care unit (ICU). Methods 213 patients with MRSA hospital-acquired pneumonia in ICU of our hospital from 2013 June to 2015 December. The MIC for vancomycin was determined by using the E-test and broth microdilution methods. Variables analyzed included age, sex, comorbid conditions, serum vancomycin trough concentration, the acute physiology and chronic health evaluation Ⅱ ( APACHE Ⅱ) score and the presence of the Agr Ⅱ gene. The primary outcome was mortality at 30 days. Results 90 patients (42. 3%) died within 30 days after MRSA culture. Multiple regression analysis showed that only APACHEⅡscore associated with 30-day mortality ( P=0. 02). E-test results showed that 18 patients with isolates exhibiting an MIC≥1. 5 μg/mL died, 27 patients (12. 7%) survived (P = 0. 74). The broth microdilution results showed that 28 patients (13. 1%) with isolates exhibiting an MIC 1. 0 μg/mL died, 47 patients ( 22. 1%) survived ( P =0. 90). The median APACHE Ⅱ score of survival patients were 22. 7, and the median APACHE Ⅱ <br> score of death patients were 25. 2 (P=0. 02). The presence of the Agr Ⅱ gene was not related to the 30-day mortality rate. Conclusion The hospital-acquired MRSA patients who MIC≤1. 5 μg / mL (E test method) or MIC≤1. 0 μg/mL (the broth microdilution method) had higher 30-day mortality. The APACHE Ⅱ scores which provides an overall estimate of ICU mortality were independently associated with mortality, regardless of the MICs determined. Molecular markers, such as the Agr Ⅱgene, were not associated with higher mortality in the present study.