Low Utility of Pediatric Isolator Blood Culture System for Detection of Fungemia in Children: a 10-Year Review

Abstract

fThe use of the Wampole Isolator 1.5-ml pediatric blood culture tube for the detection of fungemia in children was assessed by a 10-year retrospective review at two pediatric hospitals, The Hospital for Sick Children in Toronto, Canada, and the Children's Medical Center of Dallas, Texas. Over this period, a total of 9,442 pediatric Isolator specimens were processed, with yeast or yeast-like organisms recovered in 297 (3.1%) of the specimens (151 [1.6%] unique clinical episodes) and filamentous or dimorphic fungi recovered in 31 (0.3%) of the specimens (25 unique clinical episodes). Only 18 of the 151 clinical episodes of fungemia attributable to yeast were not detected by automated blood culture systems. The majority of isolated yeast were Candida spp., which were usually detected by automated systems, whereas the most common non-Candida yeast was Malassezia furfur, which the automated system failed to detect. Filamentous or dimorphic fungi were detected in 25 episodes, of which only 9 (36%) episodes were deemed clinically significant after chart review, indicating that in the majority of cases (16/25, 64%) fungal isolation represented contamination. In five of the nine clinically significant episodes, the isolated fungus (Histoplasma capsulatum, Coccidioides immitis/posadasii, Fusarium oxysporum, Aspergillus spp., and Bipolaris spp.) was also identified in other clinical specimens. Over the 10-year study period, the use of the pediatric Isolator system, at the discretion of the treating physician, only rarely provided useful clinical information for the diagnosis of fungemia in children, with the exception of M. furfur and possibly endemic mycoses. The optimal method for detection of fungi from blood in cases of suspected fungemia or disseminated fungal infection in pediatric patients remains unclear, despite the importance of establishing such a diagnosis, particularly among immunocompromised patients (1, 2). In the past, dedicated systems such as a manual biphasic brain heart infusion (BHI) broth/agar system for the recovery of fungi (including yeasts) from the bloodstream were necessary. Today, however, Candida spp., which make up the overwhelming majority of fungal isolates recovered from the blood, are efficiently recovered from automated blood culture systems within a typical 5-day incubation period (3-5). This efficient recovery of Candida spp. does, however, rely on multiple cultures since a single blood culture may only detect 65% of episodes of candidemia (6). Much less commonly isolated from automated systems are non-Candida fungi, including yeast-like fungi such as Geotrichum spp. and Trichosporon spp., or certain filamentous fungi such as Fusarium spp., Scedosporium spp., or Exophiala spp., which may represent up to 10% of all fungemias (7).To overcome the poor recovery of non-Candida fungi, other blood culture systems have been developed, such as the Isolator system (Wampole Laboratories, Cranbury, NJ) (8). There is a single published manuscript on the efficacy of the pediatric Isolator for detect...

Fungal infections in children with haematologic malignancies and stem cell transplant recipients

“…though are of low utility in the diagnosis of invasive mould infections besides those caused by Fusarium spp. (Campigotto et al ., ).…”

Malassezia: Zoonotic Implications, Parallels and Differences in Colonization and Disease in Humans and Animals

“…The diagnosis of Malassezia -associated fungemia is challenging due to its special needs for growth including lipid dependency. It is recommended to directly culture blood or central venous catheter tips on lipid-rich culture media via blood culture specimen tubes and not to use an automated blood culture system [ 14 , 313 , 349 ]. In addition, since human blood can have inhibitory and toxic effects on yeasts, the addition of 3% palmitic acid may favor positive detection [ 350 ].…”

Blood culture procedures and diagnosis of Malassezia furfur bloodstream infections: Strength and weakness

“…1 BSIs caused by lipid-dependent Malassezia species are detected either using systems preenriched with lipid substrates 15,16 or by direct isolation using the Isolator system (DuPont Co., Wilmington, DE, USA). 1,17,18 Although the automated blood culture system BacT/Alert (bioMérieux, Marcy l'Etoile, France) is worldwide used in many laboratories for the detection of bacterial and fungal pathogens, its failure to detect M. furfur has been reported through a retrospective clinical review. 17 In this study, the occurrence of Malassezia spp.…”