Epidemiological analysis of Malassezia pachydermatis isolates by partial sequencing of the large subunit ribosomal RNA.

The opportunistic yeast Malassezia pachydermatis is commonly recovered from both normal and diseased skin of warm-blooded animals. The diversity of M pachydermatis isolates obtained from a wide range of hosts was investigated by the partial sequencing of the large subunit (LSU) ribosomal RNA. Among 100 isolates examined, seven types (Ia-Ig) were discriminated on the basis of nucleotide sequence diversity. The seven types differed by one to five mutations, all of them corresponding to transitions. The predominant sequence, type Ia, appeared to be ubiquitous since it was observed in isolates recovered from domestic and wild carnivora, from a monkey and from man. In contrast the sequence types Ic, Id and Ig seemed to be more host-specific; they included isolates recovered exclusively from rhinoceros, dogs and ferrets, respectively. None of the seven sequence types correlated with isolation from healthy skin or a particular lesion (otitis externa or other dermatitis). The study indicated that the skin of an animal may be colonised by more than one type of M pachydermatis.