High-resolution fingerprinting of Candida parapsilosis isolates suggests persistence and transmission of infections among neonatal intensive care unit patients in Kuwait

Abstract

Candida parapsilosis causes ~35% of all candidemia cases in neonates. High-resolution fingerprinting of C. parapsilosis isolates from neonatal intensive care unit (NICU) patients in Maternity Hospital (MH) was performed to identify epidemiologically related strains. Sixty-eight bloodstream/colonizing strains isolated from 59 NICU patients, two isolates from health care workers (HCWs) from MH and 18 bloodstream isolates from two other hospitals were used. Six microsatellite markers were employed, isolates were assigned a numerical microsatellite genotype (MSG), dendrogram was constructed and similarities between genotypes were visualized by minimum spanning tree. Fifty bloodstream isolates from MH yielded 37 MSGs with 20 isolates clustering in 7 MSGs. Duplicate isolates and colonizing strains yielded same/highly similar MSG as bloodstream isolates. Colonizing strains from two non-candidemia patients yielded unique MSGs while others belonged to a cluster. All isolates from HCWs and from two other hospitals belonged to unique MSGs. Cluster isolates came from patients in NICU-1 or from neonates in NICU-1 and other NICUs. Clonal complexes comprising closely related genotypes indicative of microevolution were also detected. Our data show that some C. parapsilosis strains have persisted in MH environment over several years and these endemic genotypes were transmitted to other patients in NICU-1 and/or other nearby NICUs.

Figure 1

An UPGMA-derived dendrogram based on microsatellite fragments from 88 C. parapsilosis isolates. Similarity is presented in percentages using the scale bar in the upper left corner. The columns after the patient number refer to isolate number, date of isolation, hospital unit, source of the isolates and microsatellite-based genotype (MSG).

Figure 2

Minimum spanning tree of 70 C. parapsilosis isolates, from Maternity Hospital only, derived from microsatellite-based genotyping data. Each circle corresponds to a unique genotype, and lines between circles represent relative distance between isolates. The sizes of the circles correspond to the number of isolates in the same MSG. Connecting lines correspond to the number of differences between genotypes, with a solid thick line connecting genotypes that differ in one locus, a solid thin line connecting genotypes that differ in two or three loci, a dashed line connecting genotypes that differ in four loci, and a dotted line connecting genotypes that differ in more than four loci.

Figure 3

Color-coded timeline showing the distribution of 29 C. parapsilosis isolates exhibiting cluster fingerprinting patterns obtained from 29 patients in NICUs of the Maternity Hospital in Kuwait. The patient number (MH1, MH2, MH3 etc.) yielding C. parapsilosis at the indicated time points (vertical colored lines) are shown along with the corresponding cluster microsatellite genotype (MSG) in bold and italicized letters of same color. The location of patients in the four NICUs is indicated by patient number color: red font, patients in NICU-1; green font, patients in NICU-3 and blue font; patients in NICU-4. Colonizing strains are indicated by letter “C” after patient number. The patients yielding isolates belonging to same MSG that were recovered within 62 days of each other are shown in circles (color coded with each MSG) marked ‘A’ to ‘I’.