title: Isolation ofFrancisella tularensisandYersinia pestisfrom Blood Cultures by Plasma Purification and Immunomagnetic Separation Accelerates Antibiotic Susceptibility Determination.
abstract: The early symptoms of tularemia and plague, which are caused byFrancisella tularensisandYersinia pestisinfection, respectively, are common to other illnesses, resulting in a low index of suspicion among clinicians. Moreover, because these diseases can be treated only with antibiotics, rapid isolation of the bacteria and antibiotic susceptibility testing (AST) are preferable. Blood cultures of patients may serve as a source for bacteria isolation. However, due to the slow growth rates ofF. tularensisandY. pestison solid media, isolation by plating blood culture samples on proper agar plates may require several days. Thus, improving the isolation procedure prior to antibiotic susceptibility determination is a major clinically relevant need. In this study, we developed a rapid, selective procedure for the isolation ofF. tularensisandY. pestisfrom blood cultures. We examined drop-plating and plasma purification followed by immunomagnetic separation (IMS) as alternative isolation methods. We determined that replacing the classical isolation method with drop-plating is advantageous with respect to time at the expense of specificity. Hence, we also examined isolation by IMS. Sub-localization ofF. tularensiswithin blood cultures of infected mice has revealed that the majority of the bacteria are located within the extracellular fraction, in the plasma.Y. pestisalso resides within the plasma. Therefore, the plasma fraction was isolated from blood cultures and subjected to an IMS procedure using polyclonal anti-F. tularensislive vaccine strain (LVS) or anti-Y. pestisantibodies conjugated to 50-nm nano-beads. The time required to reach an inoculum of sufficient bacteria for AST was shortest when using the plasma and IMSs for both bacteria, saving up to 2 days of incubation forF. tularensisand 1 day forY. pestis. Our isolation procedure provides a proof of concept for the clinical relevance of rapid isolation for AST fromF. tularensis-andY. pestis-infected patients.
authors.affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness-Ziona, Israel.
authors.forename: Ronit
authors.initials: R
authors.lastname: Aloni-Grinstein
authors.affiliation: Department of Infectious diseases, Israel Institute for Biological Research Ness-Ziona, Israel.
authors.forename: Ofir
authors.initials: O
authors.lastname: Schuster
authors.affiliation: Department of Infectious diseases, Israel Institute for Biological Research Ness-Ziona, Israel.
authors.forename: Shmuel
authors.initials: S
authors.lastname: Yitzhaki
authors.affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness-Ziona, Israel.
authors.forename: Moshe
authors.initials: M
authors.lastname: Aftalion
authors.affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness-Ziona, Israel.
authors.forename: Sharon
authors.initials: S
authors.lastname: Maoz
authors.affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness-Ziona, Israel.
authors.forename: Ida
authors.initials: I
authors.lastname: Steinberger-Levy
authors.affiliation: Department of Biochemistry and Molecular Genetics, Israel Institute for Biological Research Ness-Ziona, Israel.
authors.forename: Raphael
authors.initials: R
authors.lastname: Ber
keywords: Francisella tularensis; Yersinia pestis; antibiotic susceptibility; bacteremia; blood culture; immunomagnetic separation