Invasive infections caused by
C. krusei has been associated with adverse outcome [
23,
24]. Poor response to treament may lead to extended hospitalization and economical burden. Therefore, control of emergence of
C. krusei and other resistant fungal pathogens should be a priorioty. Understanding of risk factors and routes of transmission should help clinicians to prevent infections or to deal with a cluster of infections by
C. krusei.
It has been shown that cross-contamination of both health care workers and patients by multiple strains of
C. albicans is possible [
25].
C. parapsilosis has also been shown to colonize hands of health care workers which may lead to clonal spread of the pathogen to vulnerable patients [
19]. Our patients, that were positive for
C. krusei in their pharyngeal or rectal samples, did not have
C. krusei growth on their hands. Health care workers at the ward were also screened and
C. krusei was not isolated from any pharyngeal or rectal samples. In addition, careful analysis of environmental samples for
C. krusei did not reveal any significant positive results. The incoming water sources were negative for
C. krusei and we speculate that the
C. krusei growth in the two sewage samples was an unlikely source of infection. These data do not support the possibile route of clonal transmission by hand contact or from a single environmental source. It must be appreciated, however, that the negative culture results may not rule out occasional exposure of patients or health care workers to
C. krusei in the ward. Although we were unable demonstrate transmission by hand contact, we continue to emphasize the importance of stringent hand hygiene measures at the ward.
Prophylactic use of fluconazole has been associated with invasive infection or colonization by
C. krusei although opposing views has been presented [
4,
11,
12,
15]. In our study, about half of the patients with acute leukaemia, that were infected or colonized by
C. krusei, were exposed to fluconazole. The same proportion of leukaemia patients that were negative for
C. krusei, had been exposed to fluconazole. We have also examined the possible association between the occurrence of
C. krusei and the use of antifungal agents or drugs used for the treatment of leukaemia. Overall, we were unable to demonstrate any association between the medications and occurrence of
C. krusei. It is possible that higher number of cases might have revealed such a relationship.
In a previous study, molecular typing of
C. krusei isolates suggested that clonal spread of a single strain caused an outbreak [
4]. Genetic analysis of our
C. krusei isolates from individual patients suggests mainly for an unrelated origin. Genotyping of several sequential isolates from five patients revealed that each patient harboured their own strain or a slightly altered variant throughout the study period (Figure ). Some clustering of the genotypes, however, could be observed. Interestingly, the
C. krusei clones isolated from blood cultures (Figure , patients 1–6) were within the same genetic cluster suggesting that those strains may share properties with each other. According to genotyping, we conclude that several different
C. krusei strains are capable of colonizing the intestinal tract that may serve as an origin of the infection [
26].
Most of our patients with C. krusei invasion had significant injury of mucosa from which the infection was most likely acquired. Surveillance of mucosal colonization by C. krusei was continued until no new invasive infections occurred. Thereafter, we have not found any new cases despite of the high number of samples that have been collected whenever fungal infection was suspected. We speculate that cessation of antifungal prophylaxis with fluconazole and an increased awareness of infection control measures, e.g. hand hygiene and cohorting of the patients, may have been beneficial although we were unable to demonstrate the significance of any single measure.