The Positive Predictive Value of Isolating Coagulase-Negative Staphylococci from Blood Cultures

Abstract

We used four criteria to define true bloodstream infections after isolation of coagulase-negative staphylococci (CNS) from Isolator (Wampole Laboratories, Cranbury, NJ) blood cultures: (1) the patient's temperature was > or = 38 degrees C, (2) appropriate treatment was administered, (3) the physician diagnosed bloodstream infection or criteria for nosocomial bloodstream infection were met, and (4) at least one clinical sign or laboratory value was consistent with infection. Sixty (26.4%) of 227 episodes met these four criteria. By logistic regression, variables associated with meeting the definition of infection were admission to a service other than the surgical intensive care unit, the biotype of the Staphylococcus epidermidis isolates, the log of the weighted average of the total number of bacteria per milliliter of blood in all positive cultures, resistance to at least six antimicrobial agents, and the positivity of a BACTEC blood culture specimen that was drawn with the first positive Isolator culture specimen. In a high-risk population, 26% of Isolator blood cultures positive for CNS represented infections, a rate two to four times greater than that reported in the literature. Information regarding the species, biotype, antibiogram, and number of organisms per milliliter of blood might help physicians distinguish between CNS bloodstream infections and contamination.

Comparison of methods for the identification of coagulase-negative staphylococci

“…Some studies have suggested an association between S. epidermidis and nosocomial infections (Vuong & Otto 2002) with this species being identified in 74 to 92% of patients with bacteremias caused by CNS (Martin et al 1989). However, other studies have reported a series of infections caused by other CNS species (Herwaldt et al 1996), mainly S. haemolyticus which Simple scheme for the identification of human Staphylococcus species; +: positive; -: negative; +, -: positive or negative; ±: weak is the second most frequently detected species (Bannerman 2003). Since CNS are the etiological agents of a series of infectious processes, identification of these microorganisms is important for the determination of their physiopathological characteristics and clinical importance and for epidemiological studies, and has led to the publication of various studies analyzing identification methods for these bacteria (Knapp & Washington 1989, Bannerman et al 1993, Piccolomini et al 1994, Renneberg et al 1995, Ieven 1995, De Paulis et al 2003.…”

Current Practice of Management of Bacteremic Sepsis: A Study in a Tertiary Care Teaching Hospital in Japan.

“…An urgent need also is the implementation of central- and clinically defined sepsis was present, and the other reason being that the prevalence of bloodstream infection due to CNS, i.e. Staphylococcus epidermidis, has been increasingly associated with clinically relevant episodes of bloodstream infections (19,(22)(23)(24). Pittet et al (22) and others have reported that candidal fungemia and polymicrobial infection are microbiological predictors of mortality in patients with hospital-acquired bloodstream infection (2,19,25).…”

Utility of obtaining blood cultures in febrile neutropenic patients undergoing bone marrow transplantation

“…A bloodstream infection was defined using previous guidelines from the Centers of Disease Control and Prevention (CDC) modified for the occurrence of coagulase-negative Staphylococci. 30 …”