After exclusion, 136 pediatric patients younger than 18 years were recruited in the study and totally, 482 samples were collected from different sites (oral/nasal discharges, urine and stool). Among them 82 (59.9%) were male. The average age was calculated 7.1 years-old (6 ± 4.69 SD; 4 and 18, minimum and maximum, respectively). Detailed data about sex and patient’s age category is shown in Table 1. As for the primary underlying disease, Acute Lymphoblastic Leukemia (ALL) was the most common oncologic diagnosis (41, 30.1%). Close to 85% (115/136) of the patients had history of recurrent admission (Table 1). The colonization rate was greater in patients with history of recurrent admission (61.7% versus 38.3%). Totally, 39% of patients had long term follow up. Of special note, among children with long term follow up, 71.7% were colonized. In this subgroup of patients, repeated admission was found to be correlated with greater chance of Candida colonization (P-value = 0.014). Common oncological diagnosis and also their colonization status have been shown in Figure 1.
482 samples were collected from different sites and finally 140 positive samples were analyzed (excluding negative cultures). About 80% of patients underwent at least two-time sampling (based on weekly sampling protocol) and more than 20% underwent 3 times or more. Among the collected samples, 195 (40%) were from oral cavity, 220 (46%) from nasal discharges, 44 (9%) from urine, and 24 (5%) from stool. There was no significant difference between colonized and non-colonized patients with regard to age category and sex (P-value = 0.088 and 0.593, respectively).
A. Patient’s colonization status
Candida colonization was found in 59.9% (82/136) of the patients. Most children exhibited oral colonization (67.1%). Oral/Rectal colonization (11%) was the second most common type of colonization among the studied children (Table 2). 72% of the children were colonized with C. albicans, followed by C. krusei (9.8%), C. kefyr (7.3%), C. glabrata (2.4%) and C. parapsilosis (2.4%). Among the studied patients, one had double colonization with C. kefir and C. parapsilosis and another one with C. albicans and C. tropicalis. Data regarding distribution of different colonization sites in colonized children are presented in Table 2. Calculated mean Candida CI was 3.11±0.121 [1:4 (78%), 2:4 (19.5%) and 3:4 (2.4%)]. Colonization site preferences were analyzed by Chi-Square Tests for age, sex, degree of neutropenia, primary oncologic diagnosis and recurrent versus new admission (Table 3), revealing no significant differences (p=0.531, p=0.304, 0.125, 0.551 and 0.797, respectively). Also, Candida CI was investigated for these variables that revealed no significant differences, either (p=0.650, p=0.246, 0.259, 0.701 and 0.307, respectively).
B. Sample’s characteristics
From 140 positive samples (excluding black yeasts), species type was determined in 130 samples (10 samples were not recognized). Oral cavity was the most common site of colonization (Figure 2), followed by nasal cavity and rectum, 98 (75.4%), 12 (9.2%) and 20 (15.4%), respectively (calculated from all positive samples). Of special note, in this study we did not find any urinary candida colonization among the studied children. Regarding sex differences, we did not observe any correlation between colonization status and sex (P-value = 0.593). In terms of age distribution, most of colonized children were over 5 years (53, 63.1%) and the rest 1-5 years (29, 59.2%). Although colonization rate was directly correlated with age category (greater in patients >5 years), the difference was not significant (P-value = 0.088, LR: 0.05). Candida colonization status was investigated based on different underlying oncologic diagnoses. ALL and AML were the most common diagnoses in both colonized and non-colonized children without any significant difference (P-value = 0.432). No statistically significant relationship was found between Candida colonization and the severity of neutropenia during admission (P-value = 0.166).
C. Candida species characteristics
Among the different types of recognized Candida species (140 spp.), C. albicans was the most common (72%), followed by C. krusei (9.8%), C. kefyr (7.3%), C. glabrata (2.4%) and C. parapsilosis (2.4%); data are shown in figure 3. Of the studied patients, one had double colonization with C. kefir and C. parapsilosis and another with C. albicans and C. tropicalis. A small proportion of the species could not be distinguished phenotypically on culture media and was categorized as “Not defined” (10 samples). Detailed data regarding different Candida species in oral and nasal discharges, and stool samples are summarized in Table 4.
D. Monitoring of colonization pattern during patient’s follow up
On average, 53 cases were followed for at least 4 weeks (26.87 days ±SD: 39.6). Follow up duration also was categorized in four-time frame as <30 days, 30-60 days, 60-90 days and >90 days. More than 64% of colonized children were followed for more than 4 weeks (Table 5).
During the study period, 6.1% of monitored cases had changes in their colonization patterns, indicating non-colonization to colonization and vice versa and also change in candida species (Table 6). During repeated sampling, in 2.2% of colonized cases, colonization was not continued (that means negative culture on two occasions at least two weeks apart).
The association between recurrent admissions and any type of colonization status change were assessed by Chi-Square Tests which revealed a significant correlation (p=0.035).