title: Small-Colony Variants in Persistent and Recurrent Staphylococcus aureus Bacteremia.
abstract: The small-colony variant (SCV) phenotype of Staphylococcus aureus is associated with intracellular persistence and reduced antimicrobial susceptibility, which can lead to therapeutic failure. Since SCVs grow slowly and have a confusing morphology, the identification of infections due to SCV is difficult. We have identified SCVs in two patients who presented with persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia complicated by surgical site infections after cardiothoracic surgery. Nine blood isolates were collected from the two patients for species identification, antimicrobial susceptibility testing, and phenotypic and genotypic characterization. Colonies on Columbia blood agar were pinpoint, nonpigmented, nonhemolytic, and reverted to normal colonies after 48 hr of incubation on Schaedler agar. Auxotrophy assays revealed hemin dependence. Susceptibility to vancomycin (minimal inhibitory concentrations 1.0 μg/mL) was confirmed by E-test and broth microdilution test. All the isolates were identified as MRSA by multiplex polymerase chain reaction specific for the mecA, femA, and 16S rRNA genes, and all had the same genotype: Multilocus sequence typing ST5, SCCmec type II, agr type II, and spa type t2460. Moreover pulsed-field gel electrophoresis typing revealed that all nine isolates belonged to the same clone. Mutations in the relA gene were not found, and none of the isolates was identified as hVISA by population analysis profiling-AUC ratio. A high level of suspicion is required to detect SCVs, and although it is not common, the possibility of the SCV phenotype has to be considered in persistent S. aureus bacteremia.
authors.affiliation: 1 Department of Internal Medicine, Seoul National University College of Medicine , Seoul, Republic of Korea.
authors.forename: Nak-Hyun
authors.initials: NH
authors.lastname: Kim
authors.affiliation: 1 Department of Internal Medicine, Seoul National University College of Medicine , Seoul, Republic of Korea.
authors.forename: Yu Min
authors.initials: YM
authors.lastname: Kang
authors.affiliation: 2 Division of Infectious Diseases, Seoul National University Bundang Hospital , Seongnam, Republic of Korea.
authors.forename: Woong Dae
authors.initials: WD
authors.lastname: Han
authors.affiliation: 3 Department of Laboratory Medicine, Seoul National University College of Medicine , Seoul, Republic of Korea.
authors.forename: Kyoung Un
authors.initials: KU
authors.lastname: Park
authors.affiliation: 4 Department of Thoracic Surgery, Seoul National University College of Medicine , Seoul, Republic of Korea.
authors.forename: Kay-Hyun
authors.initials: KH
authors.lastname: Park
authors.affiliation: 5 Division of Antimicrobial Resistance, Center for Infectious Diseases, Korea National Institute of Health , Cheongwon, Republic of Korea.
authors.forename: Jae Il
authors.initials: JI
authors.lastname: Yoo
authors.affiliation: 6 Vaccine Bio Research Institute, Catholic University of Korea , Seoul, Republic of Korea.
authors.forename: Dong-Gun
authors.initials: DG
authors.lastname: Lee
authors.affiliation: 6 Vaccine Bio Research Institute, Catholic University of Korea , Seoul, Republic of Korea.
authors.forename: Chulmin
authors.initials: C
authors.lastname: Park
authors.affiliation: 1 Department of Internal Medicine, Seoul National University College of Medicine , Seoul, Republic of Korea.|2 Division of Infectious Diseases, Seoul National University Bundang Hospital , Seongnam, Republic of Korea.
authors.forename: Kyoung-Ho
authors.initials: KH
authors.lastname: Song
authors.affiliation: 1 Department of Internal Medicine, Seoul National University College of Medicine , Seoul, Republic of Korea.|2 Division of Infectious Diseases, Seoul National University Bundang Hospital , Seongnam, Republic of Korea.
authors.forename: Eu Suk
authors.initials: ES
authors.lastname: Kim
authors.affiliation: 1 Department of Internal Medicine, Seoul National University College of Medicine , Seoul, Republic of Korea.
authors.forename: Sang Won
authors.initials: SW
authors.lastname: Park
authors.affiliation: 1 Department of Internal Medicine, Seoul National University College of Medicine , Seoul, Republic of Korea.
authors.forename: Nam Joong
authors.initials: NJ
authors.lastname: Kim
authors.affiliation: 1 Department of Internal Medicine, Seoul National University College of Medicine , Seoul, Republic of Korea.
authors.forename: Myoung-Don
authors.initials: MD
authors.lastname: Oh
authors.affiliation: 1 Department of Internal Medicine, Seoul National University College of Medicine , Seoul, Republic of Korea.|2 Division of Infectious Diseases, Seoul National University Bundang Hospital , Seongnam, Republic of Korea.
authors.forename: Hong Bin
authors.initials: HB
authors.lastname: Kim
mesh_terms: D000368:Aged; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D016470:Bacteremia / Q000188:drug therapy / Q000382:microbiology* / Q000473:pathology; D015373:Bacterial Typing Techniques; D002999:Clone Cells; D016521:Electrophoresis, Gel, Pulsed-Field; D005798:Genes, Bacterial; D005838:Genotype; D006801:Humans; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000187:drug effects / Q000235:genetics* / Q000302:isolation & purification; D058885:Multilocus Sequence Typing; D010641:Phenotype; D012008:Recurrence; D013203:Staphylococcal Infections / Q000188:drug therapy / Q000382:microbiology* / Q000473:pathology; D013530:Surgical Wound Infection / Q000188:drug therapy / Q000382:microbiology* / Q000473:pathology; D014640:Vancomycin / Q000494:pharmacology
chemical_list: D000900:Anti-Bacterial Agents; D014640:Vancomycin
keywords: Staphylococcus aureus; persistent bacteremia; small-colony variant