title: Clinical significance of coryneform Gram-positive rods from blood identified by MALDI-TOF mass spectrometry and their susceptibility profiles - a retrospective chart review.
abstract: With the advent of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS), most Gram-positive rods (GPRs) are readily identified; however, their clinical relevance in blood cultures remains unclear. Herein, we assessed the clinical significance of GPRs isolated from blood and identified in the era of MALDI-TOF MS. A retrospective chart review of patients presenting to the Mayo Clinic, Rochester, MN, from January 1, 2013, to October 13, 2015, was performed. Any episode of a positive blood culture for a GPR was included. We assessed the number of bottles positive for a given isolate, time to positivity of blood cultures, patient age, medical history, interpretation of culture results by the healthcare team and whether infectious diseases consultation was obtained. We also evaluated the susceptibility profiles of a larger collection of GPRs tested in the clinical microbiology laboratory of the Mayo Clinic, Rochester, MN from January 1, 2013, to October 31, 2015. There were a total of 246 GPRs isolated from the blood of 181 patients during the study period. 56% (n = 101) were deemed contaminants by the healthcare team and were not treated; 33% (n = 59) were clinically determined to represent true bacteremia and were treated; and 8% (n = 14) were considered of uncertain significance, with patients prescribed treatment regardless. Patient characteristics associated with an isolate being treated on univariate analysis included younger age (P = 0.02), identification to the species level (P = 0.02), higher number of positive blood culture sets (P < 0.0001), lower time to positivity (P < 0.0001), immunosuppression (P = 0.03), and recommendation made by an infectious disease consultant (P = 0.0005). On multivariable analysis, infectious diseases consultation (P = 0.03), higher number of positive blood culture sets (P = 0.0005) and lower time to positivity (P = 0.03) were associated with an isolate being treated. 100, 83, 48 and 34% of GPRs were susceptible to vancomycin, meropenem, penicillin and ceftriaxone, respectively.
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Ammara
authors.initials: A
authors.lastname: Mushtaq
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Derrick J
authors.initials: DJ
authors.lastname: Chen
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Gregory J
authors.initials: GJ
authors.lastname: Strand
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Brenda L
authors.initials: BL
authors.lastname: Dylla
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Nicolynn C
authors.initials: NC
authors.lastname: Cole
authors.affiliation: Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN 55905, USA.
authors.forename: Jayawant
authors.initials: J
authors.lastname: Mandrekar
authors.affiliation: Division of Clinical Microbiology, Department of Laboratory Medicine and Pathology, Mayo Clinic, Rochester, MN 55905, USA; Division of Infectious Diseases, Department of Medicine, Mayo Clinic, Rochester, MN 55905, USA. Electronic address: patel.robin@mayo.edu.
authors.forename: Robin
authors.initials: R
authors.lastname: Patel
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D016470:Bacteremia / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D001769:Blood / Q000382:microbiology*; D016908:Gram-Positive Bacterial Infections / Q000188:drug therapy / Q000453:epidemiology / Q000382:microbiology*; D016987:Gram-Positive Rods / Q000737:chemistry / Q000187:drug effects* / Q000302:isolation & purification*; D006801:Humans; D008826:Microbial Sensitivity Tests; D012189:Retrospective Studies; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization
chemical_list: D000900:Anti-Bacterial Agents
keywords: Bloodstream infection; Gram-positive rods; MALDI-TOF MS; Species identification; Vancomycin