Candidaemia in patients with haematological disorders and stem cell transplant.

The incidence of non-albicans species of Candida has recently increased, especially in patients with malignant haematological disorders receiving fluconazole prophylaxis. A retrospective study of patients who developed candidaemia at Riyadh Armed Forces Hospital between January 1992 and December 2002 was carried out. Thirty one episodes of candidaemia occurred in 27 patients with a variety of haematological disorders. Twenty-four episodes were caused by non-albicans species of Candida and only 7 episodes were caused by C.albicans. The most frequent underlying haematological disorders were acute myeloid leukaemia (AML) followed by acute lymphoblastic leukaemia (ALL). The main predisposing factors for the development of candidaemia were: broad spectrum antibiotics, central venous catheters, neutropenia, cytotoxic chemotherapy, coexisting bacterial infections, steroid therapy, relapsing or untreated primary disease and fluconazole prophylaxis.Eight episodes were complicated by chronic disseminated candidiasis. Amphotericin-B and amBisome were used in the treatment of Candida infections. The treatment was successful in 86% of the episodes of C. albicans and 50% of the episodes due to nonalbicans species of Candida. The highest mortality rate was encountered with C.tropicalis infections.Candidaemia is an important cause of mortality and morbidity in patients with malignant haematological disorders and stem cell transplant. The predominance of non-albicans species of Candida especially C.krusei and C.tropicalis is alarming. The early administration of appropriate antifungal therapy and the removal of infected intravascular catheters improve the outcome considerably.

INTRODUCTION

Most fungal infections in hospitalized patients are caused by Candida species. Recently, there has been a substantial shift in the epidemiology of haematogenous candidiasis caused by different species [1-5]. The use of prophylactic fluconazole is known to decrease colonization and subsequent infection with C. albicans [6, 7]. However, the extensive use of this drug in neutropenic patients with leukaemia and stem cell transplant (SCT) has been associated with the emergence of azole-resistant non-albicans species of Candida [3–5, 8–11].

Blood cultures for Candida become positive at a median time of 10 days after the onset of neutropenia [12]. Polymerase chain reactions (PCR) and antigen detection tests are useful in making an early diagnosis of candidaemia [13, 14]. Successful management of candidaemia depends upon the early institution of antifungal therapy, the recovery of neutrophilic count and the early removal of intravascular catheters if present [12, 15, 16].

A previous study done at our institution demonstrated the predominance of non-albicans Candida in the bloodstream isolates in the haematology unit with C. krusei being the commonest Candida species encountered [17]. In view of that study and similar reports on the prevalence of non-albicans species of Candida in neutropenic patients with malignant haematological disorders, this retrospective study was conducted.

PATIENTS, MATERIALS AND METHODS

Riyadh Armed Forces Hospital (RAFH) is a tertiary care center comprising 1200 beds with specialty services including: intensive care, haematology/oncology, SCT and solid organ transplantation. A retrospective study of patients with various haematologic disorders and SCT who developed candidaemia at RAFH between January 1992 and December 2002 was carried out. The medical records and the laboratory data of these patients were reviewed.

DEFINITIONS

Candidaemia: The presence of a clinical illness (eg. fever, hypotension or respiratory insufficiency) associated with the isolation of Candida species from at least one blood culture specimen, without evidence of visceral involvement. An episode was regarded as having at least one positive blood culture set for a single Candida species during one period of hospitalization. All the consecutive positive blood cultures within 72 hours for the same type of Candida during the same period of hospitalization were considered as a single episode. If more than one Candida species were isolated during the same period of hospitalization, infection due to each species was considered a separate episode.

Breakthrough fungaemia: The presence of Candida in the bloodstream of patients who have received prophylactic systemic antifungal therapy for longer than 48 hours.

Persistent infection: The presence of Candida in blood culture specimens 72 hours or longer after starting appropriate antifungal therapy. All patients with persistent fungaemia were evaluated for secondary ocular, cardiovascular or joint infections.

Chronic disseminated candidiasis (CDC): The presence of histopathological evidence (budding yeast or pseudohyphae) of candidiasis in the spleen, the liver and the kidneys and/or radiological evidence (hypodense lesions) of hepatosplenic or renal candidiasis.

Acute disseminated candidiasis (ADC): Patients having evidence of multiple noncontagious organ infection acquired through haematogenous spread i. e. the presence of fungal infection (based on histology or culture) in a certain body organ and having clinical, histopathological or radiological evidence of the same fungal infection in another organ.

Catheter–related candidiasis: Candidaemia was considered to be catheter related if there is no apparent source of infection or if the organism was isolated from both central and peripheral blood culture specimens or if the organism was isolated form both a peripheral blood culture specimen and the tip of the central venous catheter.

Colonization by Candida species: Positivity of surveillance cultures performed from nasal, pharyngeal, rectal, urinary and skin swabs.

Other coexisting infections: The presence of other organisms (eg. bacteria, viruses or other fungal species) causing a clinically significant illness.

Neutropenia: Absolute neutrophilic count (ANC) <500 cells/ mm3 in the peripheral circulation was regarded as neutropenia and ANC <100 cells/mm3 was regarded as profound or severe neutropenia. Duration of neutropenia was defined as the time interval in days form the onset of neutropenia till the detection of Candida species in blood culture specimens.

Febrile illness: More than two successive oral readings of greater than or equal to 38°C within 24 hours period.

Therapeutic response (to both initial and subsequent therapy): The complete resolution of all signs and symptoms of infection and the presence of negative blood cultures for Candida.

Therapeutic failure: Failure of antifungal therapy to eliminate candidaemia within 3 days or no improvement or worsening of clinical manifestations after 3 days of antifungal therapy.

Mortality: Death attributable to fungaemia was considered when patients died with clinical, microbiological or histopathological evidence of active fungal infection in the absence of other identifiable causes of death.

MICROBIOLOGICAL TECHNIQUES

The diagnosis of candidaemia was based on the isolation of the yeast from one or more blood culture sets (aerobic and/or anaerobic bottles) collected from patients with various haematological disorders having febrile illness or clinical evidence of septic shock. Blood cultures were performed using the automated blood culture system (Bactec 9240, Beckton Dickinson, USA]. Presumptive identification was done by the use of germ tube reaction, colony morphology and colour reaction on chrom agar [Chrom Agar Technology, Paris]. Identification to species level was done by the commercial identification system API 20C [Analytic Products, plain view, NY, USA]. For CVC (central venous catheter) tip culture, a semiqunatitative culture method was used where >15 colony forming units were considered significant.

RESULTS

Thirty one episodes of candidaemia were encountered in twentyseven patients over an eleven year period (January 1992 to December 2002). One patient experienced three episodes of candidaemia with different species and two patients developed two episodes of fungaemia each. All the records of these patients were retrieved for analysis. All the positive blood cultures were thought to represent true infection rather than contamination. The distribution of the episodes of candidaemia over the study period of time is shown in Figure 1.

Figure 1

Shows the distribution of the episodes of candidaemia

Of the patients studied, 14 were males and 13 were females. The ages of these patients ranged between 16 and 72 years (mean: 36.8 years). Thirteen patients had AML, 10 had ALL, 2 non– Hodgkin's lymphoma, 1 multiple myeloma and 1 beta-thalassaemia major. Only 5 patients had SCT prior to the candidaemic episodes (4 allogeneic and 1 autologous). The overall incidence of candidaemia at our institution during the period of the study was 10.45% in patients with acute leukaemia and 4.4% in patients with SCT. Breakthrough fungaemia was seen in 15 episodes (2 episodes were caused by C.albicans and 13 episodes were caused by non-albicans species of Candida) during which patients were receiving fluconazole prophylaxis.

Acute disseminated candidiasis complicated one episode of fungaemia caused by C. krusei species. Only three episodes of candidaemia were complicated by persistent fungal infections (two with C. krusei and one with C. tropicalis). Amphotericin-B was used in the treatment of 19 of the episodes of fungaemia. The dose of amphotericin-B used was 1 mg per kg per day intravenously over 4 to 6 hours. Only 3 fungaemic episodes were treated with intralipid formulations of amphotericinB (Abelcet; Enzon). Liposomal amphotericin-B (amBisome) was used in the treatment of 9 episodes of candidaemia and it was predominantly used in case of renal impairment or disseminated fungal infection. The doses of amBisome used were 3 to 5 mg per kg per day intravenously over 30 minutes. The duration of antifungal therapy was 2 to 3 weeks for uncomplicated candidaemia and 2 to 4 months for chronic disseminated candidiasis (CDC). Four cases of CDC were treated with amphotericin-B and 4 cases were treated with amBisome. All the patients who developed candidaemia and were having indwelling intravascular catheters in situ at the time of the fungaemic episode had removal of these devices.

Early removal of intravascular catheters (within 12 hours) was performed in 21 episodes, while late removal was done in the remaining 10 episodes of fungaemia. All 5 episodes of fungaemia due to C. albicans, during which early removal of indwelling intravascular devices was possible, ultimately had successful outcome, while only 10 of 16 episodes of non-albicans candidaemia, during which early removal of intravascular catheters was done, had successful outcomes. The predisposing factors for the development of candidaemia are shown in Table 1.

Table 1

Shows the predisposing factors for candidaemia

Risk Factors	C. albicans	Non-albicans Candida	C. krusei	C.tropicalis	C. parapsilosis	C.glabrate	C.famata	All Species
Chemotherapy:
Not Given	2	3	1	0	1	1	0	5
1-3 Courses	1	9	6	3	0	0	0	10
A or more Courts	4	12	5	3	2	1	1	16
Broad Spectrum AntibEoticE	7	24	12	6	3	2	1	31
Documented Bacterial Infection	5	16	5	6	2	2	1	21
Fluconazole	2	13	9	2	1	1	0	15
Prophylaxis
Steroid Therapy	6	10	6	3	1	0	0	16
Radiotherapy	4	4	2	1	1	0	0	8
Neutropenia	7	21	10	5	3	2	1	28
Central Venous Catheters	7	24	12	6	3	2	1	31
Relapsing Disease	3	11	6	3	1	0	1	14
Other Medical Illnesses	1	7	3	2	1	1	0	8
Old Age	0	4	2	1	0	1	0	4
Mucocutaneous Colonization	5	15	6	4	2	2	1	20

Neutropenia, radiotherapy, steroid therapy and coexisting bacterial infections were more frequent with C. albicans infections while old age, other medical illnesses, relapsing disease, cytotoxic chemotherapy and fluconazole prophylaxis were more frequently encountered in episodes caused by non-albicans species. The coexisting bacterial infections were predominantly caused by gram negative organisms: Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Klebseilla pneumoniae and E. coli. Compared to patients having fungaemia due to other types of nonalbicans Candida, patients with C. krusei had a lower proportion of coexisting bacterial infections (41.7%) and a higher percentage of flunconazole use (75%). Nine patients with candidaemia (33.3%) had surgical intervention prior to the episodes of fungaemia. Twenty episodes of fungaemia (64.5%) were preceeded by mucous membrane colonization. Relapsing primary haematological disorder was found to be a significant risk factor for the development of candidaemia (Fisher's exact, two sided p=0.02). Successful management of the candidaemic episodes was higher in C. albicans than in the other types of Candida (85.7% vs. 50%). Amongst the non-albicans species of Candida, the best outcome of treatment of the episodes of fungaemia was encountered with C. parapsillosis (100%). One year follow up of the 27 patients studied showed that 22 patients died and only 5 patients survived. The details are shown in Table 2.

Table 2

Shows certain characteristics of the candidaemic episodes

Species of Candida	Number of episodes	Septic shock	Artificial ventilation	Outcome of the epi scute	One year survival	Other coexisting infections
C albicans	7	4	3	6 successful	2	6
C. krusei	12	11	6	6 successful	5	11
C. troprcalis	6	5	2	2 successful	1	5
C. parapsilosis	3	2	1	3 successful	1	3
G. glabrvte	2	2	1	1 successful	1	2
C. fernala	1	1	1	0 successful	0	1
Total	31	25	11	18 successful	10	28

Fungaemia was the primary cause of death in 37.5% of patients with non-albicans candidaemia but was the sole cause of death in one patient with C. albicans sepsis. The underlying haematological disorder and the development of other infections were the main causes of death in the deceased patients with C. albicans infections. Eight episodes of fungaemia were complicated by CDC (4 C. albicans and 4 nonalbicans Candida species). In patients with CDC, the liver and the spleen were the most frequently involved internal body organs while involvement of the kidneys was encountered in only two episodes of candidaemia (Table 3).

Table 3

Shows causes of death and disseminated infections

	Candida albicans	Candida krusei	Candida fropicalis	Candida parapsifasts	Candida glabrata	Candida famata	Non-aibicans Candida	All Candida species
Deceased Patients	6	10	6	2	2	1	21	27
Causes of Death
Primary Disease	1	4	0	0	1	0	5	6
Candidaemia	1	6	2	0	1	0	9	10
Primary Disease and Other Infections	3	0	4	2	0	1	7	10
Stem Cell Transplant Complications	1	0	0	0	0	0	0	1
Chronic Disseminated Candidiasis	4	2	1	1	0	0	4	8

DISCUSSION

Candida species are the most common cause of fungal infections and they produce infections that range from non-life threatening mucocutaneous illnesses to invasive processes that may eventually involve any body organ [9, 16]. Candidaemia is a serious complication and an important cause of morbidity and mortality in patients with acute leukaemia, various forms of stem cell and solid organ transplantation [8–10, 16]. The predisposing factors for candidaemia include: malignant haematological disorders specially AML, stem cell and solid organ transplantation, intensive cytotoxic chemotherapy, prolonged neutropenia, intravascular catheters, steroid therapy, broad spectrum antibiotic treatment, antifungal prophylaxis with fluconazole, bacteremia, cytomegalovirus disease, hospitalization and admission to intensive care units, HIV infection, surgical intervention and fetal immaturity [5, 12, 13, 15, 18–21]. Gastrointestinal colonization by Candida species has also been found to play a major role in the development of breakthrough candidaemia [5, 8, 15, 22–24]. In addition, relapsing, untreated and refractory primary disease is an important associated factor for the development of fungaemia [25]. The predominant clinical manifestations of candidaemia are: fever, skin lesions, respiratory symptoms and septic shock [12, 15, 20]. In our study, the main predisposing factors for the development of fungaemia were: malignant haematological disorders specially AML, broad spectrum antibiotics, central venous catheters, neutropenia, cytotoxic chemotherapy, coexisting bacterial infection and steroid therapy. In agreement with similar studies, fluconazole prophylaxis, mucocutaneous colonization by Candida, and relapsing primary malignant haematological disorder were found to be important predisposing factors for candidaemia, particularly in patients with fungaemia due to non-albicans species.

Previously, C. albicans was found to be the commonest cause of candidaemia, but in recent years approximately 50% of the fungaemic episodes were caused by other Candida species [8-10]. Patients with C. albicans sepsis often have other co-existing viral and bacterial infections and septic thrombophlebitis and have a significantly greater overall response to antifungal therapy and to the treatment given for the primary illness [8]. Non-albicans Candida species particularly C. krusei and C. glabrata have recently emerged as important candidaemia among neutropenic cancer or SCT patients who have received fluconazole prophylaxis [5, 8, 10, 22]. They may be intrinsically resistant to fluconazole, but they are very susceptible to amphotericin-B and the new extended spectrum triazoles such as voriconazole and posaconazole [9, 22, 26]. The frequency of non-albicans Candida species as causes of bloodstream isolates and their susceptibilities to fluconazole, vary considerably among different countries worldwide [8, 17, 26, 27]. Fungaemia, due to these organisms, carries high mortality rates in immunocompromised individuals, especially in patients with leukaemia, solid tumors and hepatic disorders [8, 15, 17, 21, 26, 27]. As with reports of increased prevalence of non-albicans species of Candida in neutropenic patients, our study showed predominance of non-albicans species particularly C. krusei and C. tropicalis.

Over the past two decades, there has been a gradual increase in the number of patients with malignant haematological disorders at risk of invasive fungal infections [8, 28, 29]. Although CDC is a life threatening complication in immunocompromised individuals, the mortality rates due to CDC are less than that encountered in candidaemia and invasive aspergillosis [18, 28]. Only one fifth of the cases of CDC have positive blood cultures due to previous exposure to antifungal therapy or prophylaxis [23]. Studies have shown that the liver, the spleen, the lungs and the kidneys are the most frequently involved body organs [18]. Our study showed that disseminated Candida infections were seen more frequently with C. albicans and that the liver, the spleen and the kidneys were the most commonly involved body sites.

In many laboratories, the susceptibility testing of fungi is not considered a routine testing procedure [16]. It is most helpful in dealing with severe and invasive fungal infections due to non-albicans species of Candida [9, 10, 16]. Especially in patients treated with azole antifungal agents, the possibility of microbiological resistance should be taken into consideration [9–11, 16, 26, 27]. Azole resistance for C. albicans has been reported in patients with HIV infection and in patients with invasive candidiasis [9–11, 16].

Despite its adverse effects, conventional amphotericin-B has been the standard agent for the reatment of invasive candidiasis [5, 10,16]. Amphotericin-B related nephrotoxicity and other side effects have been associated with increased mortality, thus making the various lipid formulations of amphotericin-B more appropriate alternatives [16]. Most Candida isolates appear to remain susceptible to amphotericin-B although recent data indicate that C. krusei and C. glabrata may require relatively high doses of amphotericin-B [10, 16]. In patients with febrile neutropenia, amBisome has comparable efficacy to conventional amphotericin-B and is associated with fewer breakthrough fungal infections and less nephrotoxicity and other side effects [30]. Caspofungin is as effective as amphotericin-B in the treatment of candidaemia and invasive Candida infections [31]. Flucytosine is active against many Candida isolates but its adverse effects have limited its use [16]. Despite the recent advances in antifungal therapy, intense efforts are still required to develop more effective antifungal agents for use in the treatment of severe and invasive fungal infections [32]. The late introduction of the new antifungal agents (voriconazole and caspofungin) at our institution and the avoidance of flucytosine use due to its myelotoxicity made various amphotericin-B formulations the cornerstone of therapy for the candidaemic episodes discussed.

In patients with fungaemia, poor prognosis and high mortality rates are associated with: severe underlying illness, old age, prolonged neutropenia, culture of non-albicans species of Candida, septic shock, visceral dissemination and lack of antifungal prophylaxis [2, 15, 33]. The early recognition of candidaemia, the prompt removal of central venous catheters and the early initiation of an appropriate antifungal therapy improve the outcome of patients with candidaemia [15, 34]. In our group of patients: prolonged neutropenia, untreated or relapsing primary disease, septic shock and the presence of non-albicans fungaemia were the leading causes of unsuccessful outcome.

CONCLUSION

Candidaemia is an important cause of morbidity and mortality in patients with malignant haematological disorders and SCT. The use of fluconazole prophylaxis in neutropenic immunocompromised individuals is associated with the emergence of non-albicans species of Candida. Successful outcome of candidaemia depends upon the early administration of appropriate antifungal therapy and the early removal of infected intravascular devices, while the delayed recovery of neutropenia and the culture of nonalbicans species of Candida are associated with poor prognosis. In patients with candidaemia, it is mandatory to perform repeated and thorough clinical assessment and to repeat appropriate serological and radiological investigations to rule out the possibility of disseminated candidiasis.