A Retrospective Analysis Of Antifungal Susceptibilities Of Candida Bloodstream Isolates From Singapore Hospitals

October 2008, Vol. 37 No. 10

Candidaemia in Singapore Hospitals—Thean Yen Tan et al 835

A Retrospective Analysis of Antifungal Susceptibilities of Candida Bloodstream

Isolates From Singapore Hospitals

Thean Yen Tan,1MB.BCh, MRCPath, Ai Ling Tan,2MBBS, Dip Bact, FRCPA, Nancy WS Tee,3MBBS, FRCPA,

Lily SY Ng,1DQE (Bacteriology), SpDip (Microbiology)

Introduction

Nosocomial infection with Candida species is increasing

in significance worldwide. A recent review of positive

blood cultures noted the relative increase in importance of

fungal bloodstream infections (BSI),1 and Candida was

reported as the fourth most common blood stream pathogen

in the United States.2 Candida BSI is associated with a very

high crude mortality of over 60%,3 while the attributable

mortality may be as high as 49%.4

C. albicans remains the predominant pathogen associated

with BSI caused by Candida spp. Population-based studies

in Europe5 and the United States6 demonstrate that

approximately 95% of candidaemia is caused by 4 species:

C. albicans, C. glabrata, C. parasilosis and C. tropicalis.

There has been a documented increase in the proportion of

infections caused by other non-albicans sp.,7 particularly

C. glabrata. In addition to this shift in species distribution,

geographic variations are apparent in the distribution of

Candida species implicated in BSI,7 emphasising the

importance of knowing local epidemiological patterns.

1 Division of Laboratory Medicine, Changi General Hospital, Singapore

2 Department of Pathology, Singapore General Hospital, Singapore

3 Laboratory, KK Women and Children’s Hospital, Singapore

Address for Correspondence: Dr Thean Yen Tan, Division of Laboratory Medicine, Changi General Hospital, 2 Simei Street 3, Singapore 529889.

Email: [e-mail]

Abstract

Introduction: Worldwide, Candida albicans is the most common Candida species implicated in

bloodstream infections. However, the proportion of non-albicans bloodstream infections is

increasing. Fluconazole resistance is known to be more common in non-albicans species, but is

also reported in C. albicans. This retrospective study was performed to determine the species

epidemiology of Candida bloodstream infections in Singapore hospitals, and to perform susceptibility

testing to a range of antifungal drugs. Materials and Methods: Candida spp. isolated from

bloodstream infections from October 2004 to December 2006 were collected from 3 participating

hospitals: a tertiary referral hospital (Singapore General Hospital), a secondary referral hospital

(Changi General Hospital) and an obstetrics/paediatric hospital [KK Women’s and Children’s

Hospital (KKWCH)]. Isolate collection was also retrospectively extended to January 2000 for

KKWCH because of the limited number of cases from this hospital. Isolates were identified by

a common protocol, and antifungal susceptibility testing was performed by microbroth dilution

(Sensititre One, Trek Diagnostics, United Kingdom). Results: The most common isolates were C.

albicans (37%), C. tropicalis (27%) and C. glabrata (16%). There were differences in species

distribution between institutions, with C. parapsilosis and C. albicans predominant in KKWCH,

and C. albicans and C. tropicalis predominant in the other 2 institutions. Fluconazole resistance

was detected in 3.2% of all Candida spp., and 85.3% were classified as susceptible. All C. albicans

and C. parapsilosis were susceptible to fluconazole and voriconazole, while susceptibility to

fluconazole was much more variable for C. glabrata and C. krusei. Conclusion: This study shows

that C. albicans remains the predominant Candida species isolated from bloodstream infections

in the 3 participating hospitals. However, non-albicans species accounted for nearly two-thirds

of all cases of candidaemia. Resistance to fluconazole was uncommon, and was generally confined

to C. krusei and C. glabrata.

Ann Acad Med Singapore 2008;37:835-40

Key words: Antifungal agents, Antifungal drug resistance, Fungaemia

Original Article

836

Annals Academy of Medicine

Candidaemia in Singapore Hospitals—Thean Yen Tan et al

Fluconazole has remained the mainstay of empiric antifungal

therapy since its introduction in the early 1990’s,

because of favourable pharmacokinetic and side effect

profiles. However, C. glabrata and C. krusei exhibit reduced

susceptibilities or frank resistance to fluconazole.8 In

addition, there is documented increasing fluconazole

resistance in all Candida