Identification and molecular analysis of pathogenic yeasts in droppings of domestic pigeons in Beijing, China.

Feral pigeons are known as reservoirs of pathogenic yeasts that cause opportunistic infections in human. In the outskirts of Beijing, China, pigeons are more frequently raised at homes than are encountered in public areas. Many studies have focused on the presence of pathogenic yeasts in the excreta (fresh or withered) of a variety kinds of birds, pigeon crop and cloacae. One hundred and forty-three samples of fresh droppings were collected from three suburban pigeon-raising homes in an area of northern Beijing, China. The internal transcribed sequences (ITS) of all strains (except for 8 strains of Rhodotorula sp. ) were sequenced and compared with those of the databases of the National Center for Biotechnology Information website ( http://www.ncbi.nlm.nih.gov ) using the Basic Local Alignment Search Tool (BLAST). Yeasts representing 8 genera, Cryptococcus, Filobasidium, Rhodotorula, Candida, Debaryomyces, Saccaromyces, Trichosporon and Sporidiobolus, were identified from 120 isolates. Cryptococcus was the most prolific genera represented by eight species. The populations of yeast species isolated from fresh pigeon droppings were different among homes. Although it is well established that Cryptococcus neoformans exists mainly in old pigeon guano, several C. neoformans strains were still isolated from fresh pigeon excreta, providing a clue that live cryptococcal cells could move through the gastrointestinal tract of the pigeons. Eight genera identified from fresh droppings of domestic pigeons further confirm that pigeons serve as reservoirs, carriers and even spreaders of Cryptococcus species and other medically significant yeasts. The proportion of pathogenic yeasts in all isolates is more than 90 %.