Growth and detection of filamentous fungi in the BacT/Alert blood culture system

Scedosporium species and Lomentospora prolificans fungaemia is uniformly fatal in patients with haematological malignancy

Scedosporium and Lomentospora species are environmental moulds that are virulent in immunocompromised hosts and rarely cause bloodstream infection (BSI). Patients with Scedosporium and Lomentospora species BSI were identified by the state public laboratory service in Queensland, Australia, over a 20-year period. Twenty-two incident episodes occurred among 21 residents; one patient had a second episode 321 days following the first. Of these, 18 were Lomentospora prolificans, three were Scedosporium apiospermum complex and one was a nonspeciated Scedosporium species. Seventeen (81%) patients died during their index admission, and all-cause mortality at 30, 90 and 365 days was 73%, 82% and 91% respectively. All 20 patients with haematological malignancy died within 365 days of follow-up with a median time to death of 9 days (interquartile range, 6-20 days) following diagnoses of BSI.

First case report of bloodstream infection by Rhizomucor pusillus in a child with hemophagocytic lymphohistiocytosis

We describe an unusual presentation of fatal infection due to Rhizomucor pusillus bloodstream infection in a 12-year old pediatric patient recently diagnosed with hemophagocytic lymphohistiocytosis. R. pusillus was isolated from one blood culture drawn on Day 11 of hospitalization.

Determination of the optimum incubation period of continuously monitored blood cultures from patients with suspected endocarditis or fungaemia

AIM

It is routine practice to prolong the incubation period of blood cultures from patients with suspected subacute bacterial endocarditis (SBE) or fungal infection. The protocol in this laboratory required 28 days incubation with weekly subcultures. Following the introduction of automated continuously monitored blood culture instruments, the duration of incubation for specimens from these categories of patients was reviewed.

METHOD

In a retrospective study of blood culture specimens submitted from 1 July 1994 to 31 July 1998, the time from collection to a positive signal from the BacT/Alert automated blood culture system, in patients suspected of SBE or fungal infection, was assessed.

RESULTS

From 355 patient episodes, 896 bottles were incubated for up to 28 days, during which time 116 bottles (40 patient episodes) signalled positive. Significant organisms from suspected endocarditis patients were isolated from 87 bottles (87%), with the time to detection ranging from 9 to 96 hours. The data collected from significant isolates obtained from clinically suspected fungaemias were extremely small, prompting a review of the total fungal isolates from all blood culture bottles incubated during the study period. Yeast isolates were obtained from 78 (0.08%) bottles with the detection time ranging from 15 to 144 hours.

CONCLUSION

The practice in this laboratory now is to incubate blood cultures for up to 7 days when the clinical notes indicate the possibility of SBE or a fungal infection.

Identification of rare Candida species and other yeasts by polymerase chain reaction and slot blot hybridization

Invasive candidiasis has become a major cause of morbidity and mortality in immunocompromised hosts. Here we describe a fast and reliable DNA extraction and PCR amplification method in combination with a slot blot hybridization assay. A genus-specific probe was designed that allowed to detect DNA from a broad range of Candida species and 3 other yeasts. In addition, species-specific oligonucleotides for emerging Candida and other yeast species allowed to identify DNA extracted from Candida lusitaniae, Candida humicola, Candida kefyr, Candida inconspicua, Candida solani, Malassezia furfur and Trichosporon cutaneum. A sensitivity of at least 10(1) CFU, corresponding to 100 fg of fungal DNA, was documented for all species-specific probes and the common Candida probe. In addition, the 18S rRNA genes of 7 yeast species (C. humicola, C. kefyr, C. solani, C. inconspicua, C. norvegensis, C. utilis and M. furfur) were completely sequenced. The sequencing primers described bind to highly conserved primer binding sites. Therefore, these primers would allow rapid cycle sequence of additional ribosomal genes throughout the whole kingdom of fungi.