Despite the unique phenotypic properties and clinical importance of Penicillium marneffei, the polyketide synthase genes in its genome have never been characterized. Twenty‐three putative polyketide synthase genes and two putative polyketide synthase nonribosomal peptide‐synthase hybrid genes were identified in the P. marneffei genome, a diversity much higher than found in other pathogenic thermal dimorphic fungi, such as Histoplasma capsulatum (one polyketide synthase gene) and Coccidioides immitis (10 polyketide synthase genes). These genes were evenly distributed on the phylogenetic tree with polyketide synthase genes of Aspergillus and other fungi, indicating that the high diversity was not a result of lineage‐specific gene expansion through recent gene duplication. The melanin‐biosynthesis gene cluster had gene order and orientations identical to those in the Talaromyces stipitatus (a teleomorph of Penicillium emmonsii) genome. Phylogenetically, all six genes of the melanin‐biosynthesis gene cluster in P. marneffei were also most closely related to those in T. stipitatus, with high bootstrap supports. The polyketide synthase gene of the melanin‐biosynthesis gene cluster (alb1) in P. marneffei was knocked down, which was accompanied by loss of melanin pigment production and reduced ornamentation in conidia. The survival of mice challenged with the alb1 knockdown mutant was significantly better than those challenged with wild‐type P. marneffei (P < 0.005). The sterilizing doses of hydrogen peroxide, leading to a 50% reduction in survival of conidia, were 11 min for wild‐type P. marneffei and 6 min for the alb1 knockdown mutant of P. marneffei, implying that the melanin‐biosynthesis gene cluster contributed to virulence through decreased susceptibility to killing by hydrogen peroxide.

Sinopulmonary and rhinocerebral zygomycosis has been increasingly found in patients with hematological malignancies and bone marrow transplantation, but intestinal zygomycosis remains very rare in the literature. We investigated an outbreak of intestinal infection due to Rhizopus microsporus in 12 patients on treatment for hematological malignancies over a period of 6 months in a teaching hospital. The intake of allopurinol during hospitalization (P < 0.001) and that of commercially packaged ready-to-eat food items in the preceding 2 weeks (P < 0.001) were found to be independently significant risk factors for the development of intestinal zygomycosis. A total of 709 specimens, including 378 environmental and air samples, 181 food samples, and 150 drug samples, were taken for fungal culture. Among them, 16 samples of allopurinol tablets, 3 prepackaged ready-to-eat food items, and 1 pair of wooden chopsticks were positive for Rhizopus microsporus, which was confirmed by ITS1-5.8S-ITS2 rRNA gene cluster (internal transcribed spacer [ITS]) sequencing. The mean viable fungal counts of allopurinol obtained from wards and pharmacy were 4.22 ؋ 10 3 CFU/g of tablet (range, 3.07 ؋ 10 3 to 5.48 ؋ 10 3 ) and 3.24 ؋ 10 3 CFU/g of tablet (range, 2.68 ؋ 10 3 to 3.72 ؋ 10 3 ), respectively, which were much higher than the mean count of 2 ؋ 10 2 CFU/g of food. Phylogenetic analysis by ITS sequencing showed multiple clones from isolates of contaminated allopurinol tablets and ready-to-eat food, of which some were identical to patients' isolates, and with one isolate in the cornstarch used as an excipient for manufacture of this drug. We attempted to type the isolates by random amplification of polymorphic DNA analysis, with limited evidence of clonal distribution. The primary source of the contaminating fungus was likely to be the cornstarch used in the manufacturing of allopurinol tablets or ready-to-eat food. Rhizopus microsporus is thermotolerant and can multiply even at 50°C. The long holding time of the intermediates during the manufacturing process of allopurinol amplified the fungal load. Microbiological monitoring of drugs manufactured for highly immunosuppressed patients should be considered.Zygomycosis has become an important emerging infection in patients with hematological malignancy undergoing chemotherapy or bone marrow transplantation (24), especially with the availability of voriconazole as antifungal prophylaxis (25,28,44). Breakthrough zygomycosis in patients on voriconazole prophylactic treatment is usually manifested as sinopulmonary or rhinocerebral disease, since the fungal spores are ubiquitously found in the environment and could therefore be acquired through inhalation or traumatic inoculation through the skin or mucosa. Gastrointestinal zygomycosis has been a rare clinical entity (50, 54), but cases or outbreaks of tongue, gastric, or cutaneous zygomycosis due to Rhizopus microsporus after exposure to contaminated wooden tongue depressors have been reported (23,26,33).The Rhizopus microsporus species gr...

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Dirofilariasis is globally the commonest manifestation of zoonotic filariasis. We report the detection of a novel canine species causing human and canine dirofilariasis in Hong Kong. Three human cases occurring over 10 months were identified, one presenting with cervical lymphadenopathy, one with an abdominal subcutaneous mass, and one with a subconjunctival nodule. Transected worms recovered from the resected abdominal subcutaneous mass were morphologically compatible with Dirofilaria. The cox1 gene sequences of the three human isolates were identical; however, they were only 96.2% and 89.