title: Pneumonia Caused by Methicillin-Resistant Staphylococcus aureus: Does Vancomycin Heteroresistance Matter?
abstract: Vancomycin remains the mainstay treatment for methicillin-resistant Staphylococcus aureus (MRSA) infections, including pneumonia. There is concern regarding the emergence of vancomycin tolerance, caused by heterogeneous vancomycin-intermediate S. aureus (hVISA), and subsequent vancomycin treatment failure. Pneumonia is associated with high morbidity and mortality, especially with delays in appropriate therapy. This study evaluated the clinical outcomes of patients with hVISA pneumonia compared to those with vancomycin-susceptible S. aureus (VSSA) pneumonia. A retrospective cohort of patients with MRSA pneumonia from 2005 to 2014 was matched at a ratio of 2:1 VSSA to hVISA infections to compare patient characteristics, treatments, and outcomes. hVISA was determined by the 48-h population analysis profile area under the curve. Characteristics between VSSA and hVISA infections were compared by univariate analysis and multivariable logistic regression analysis to determine independent risk factors of inpatient mortality. Eighty-seven patients were included, representing 29 hVISA and 58 VSSA cases of pneumonia. There were no significant differences in demographics or baseline characteristics. Sequential organ failure assessment (SOFA) scores were a median of 7 (interquartile ratio [IQR], 5 to 8) in hVISA patients and 5 (IQR, 3 to 8) in VSSA (P = 0.092) patients. Inpatient mortality was significantly higher in hVISA patients (44.8% versus 24.1%; P = 0.049). Predictors of inpatient mortality upon multivariable regression were SOFA score (adjusted odds ratio [aOR], 1.36; 95% confidence interval [CI], 1.08 to 1.70), Panton-Valentine leukocidin (PVL) positivity (aOR, 6.63; 95% CI, 1.79 to 24.64), and hVISA phenotype (aOR, 3.95; 95% CI, 1.18 to 13.21). Patients with hVISA pneumonia experienced significantly higher inpatient mortality than those with VSSA pneumonia. There is a need to consider the presence of vancomycin heteroresistance in pneumonia caused by MRSA in order to potentially improve clinical outcomes.
authors.affiliation: Anti-Infective Research Laboratory, Department of Pharmacy Practice, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan, USA.
authors.forename: Kimberly C
authors.initials: KC
authors.lastname: Claeys
authors.affiliation: Anti-Infective Research Laboratory, Department of Pharmacy Practice, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan, USA.
authors.forename: Abdalhamid M
authors.initials: AM
authors.lastname: Lagnf
authors.affiliation: Anti-Infective Research Laboratory, Department of Pharmacy Practice, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan, USA.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Hallesy
authors.affiliation: Anti-Infective Research Laboratory, Department of Pharmacy Practice, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan, USA.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Compton
authors.affiliation: Anti-Infective Research Laboratory, Department of Pharmacy Practice, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan, USA.
authors.forename: Alison L
authors.initials: AL
authors.lastname: Gravelin
authors.affiliation: Anti-Infective Research Laboratory, Department of Pharmacy Practice, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan, USA Department of Pharmacy Services, Henry Ford Health-System, Detroit, Michigan, USA.
authors.forename: Susan L
authors.initials: SL
authors.lastname: Davis
authors.affiliation: Anti-Infective Research Laboratory, Department of Pharmacy Practice, Eugene Applebaum College of Pharmacy and Health Sciences, Wayne State University, Detroit, Michigan, USA School of Medicine, Wayne State University, Detroit, Michigan, USA aa1592@wayne.ed.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Rybak
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000627:therapeutic use*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D010641:Phenotype; D011014:Pneumonia / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality; D012189:Retrospective Studies; D013203:Staphylococcal Infections / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality; D016896:Treatment Outcome; D014640:Vancomycin / Q000627:therapeutic use*; D020713:Vancomycin Resistance
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin