Assessment of multiple coagulase-negative staphylococci isolated in blood cultures using pulsed-field gel electrophoresis

Abstract

One of the criteria used to determine the clinical importance of coagulase-negative staphylococci (CNS) is the isolation of the bacteria from sequential blood cultures. Sequential isolates of CNS obtained from five immunocompromised patients over three months were genetically characterized by pulsed-field gel electrophoresis (PFGE). This typing method was compared to two first-line typing methods: determination of the species and of antibiotic susceptibility. In four patients the initial clinical evaluation changed because of the PFGE results several episodes of bacteremia would have been wrongly assessed if only the biotype and the antibiotype had been determined. Pulsed-field gel electrophoresis should therefore be used for CNS strains from immunocompromised patients or those suffering from chronic diseases with non-concordant biotype and anti-biotype.

Molecular Analysis of Coagulase‐NegativeStaphylococcusIsolates from Blood Cultures: Prevalence of Genotypic Variation and Polyclonal Bacteremia

“…Generally, the presence of clinical signs of bacteremia, identification of a possible source of infection, and/or repeated isolation of the same organism is considered to be suggestive of bacteremia [2,5,[9][10][11]. In contrast, the isolation of multiple species from у1 culture ordinarily is considered to signify contamination [2,[9][10][11][12].…”

Clonal Diversity in Episodes with Multiple Coagulase-Negative Staphylococcus Bloodstream Isolates Suggesting Frequent Contamination

“…Thus, there are advantages to this approach for both the individual patient and the community. Given the sample size of our study and those in previous reports [5,7,8,11,16], a larger multicenter trial to define the most useful approach for the identification of true CoNS bacteremia is needed. …”

“…We analyzed 38 episodes in which CoNS was recovered from two or more blood cultures within 24 h, a criterion that is generally used by clinicians to identify patients who require treatment for ''true'' CoNS bacteremia [9][10][11].…”

“…A true bacteremia may be more likely if CoNS isolates are recovered from two or more positive sets of blood cultures and the isolates are demonstrated to be the same clone by molecular typing studies. Conversely, if two or more CoNS isolates are shown to be different clones, contamination is likely [2,[11][12][13].…”

“…Different clinical-and/or laboratory-based algorithms have demonstrated variable discriminatory power between true bacteremia and contamination [4][5][6][7][8]. Therefore, in clinical practice, if only one of two or more sets is positive for CoNS, the positive result is presumed to be a contaminant, while if two or more blood cultures yield CoNS, a true bacteremia is assumed [9][10][11] and systemic antimicrobial treatment with vancomycin is initiated [12]. The validity of this commonly used clinical practice is not well defined.…”