Aspergillus tanneri sp. nov., a new pathogen that causes invasive disease refractory to antifungal therapy.

The most common cause of invasive aspergillosis (IA) in patients with chronic granulomatous disease (CGD) is Aspergillus fumigatus followed by A. nidulans; other aspergilli rarely cause the disease. Here we review two clinical cases of fatal IA in CGD patients and describe a new etiologic agent of IA refractory to antifungal therapy. Unlike typical IA caused by A. fumigatus, the disease caused by the new species was chronic and spread from the lung to multiple adjacent organs. Mycological characteristics and the phylogenetic relationship with other aspergilli based on the sequence analysis of Mcm7, RPB2, and Tsr1 indicated that the new species, which we named as A. tanneri, belongs to Aspergillus section Circumdati. The species has a higher amphotericin B, voriconazole, and itraconazole MIC and causes more chronic infection in CGD mice than A. fumigatus. This is the first report documenting IA in CGD patients caused by a species belonging to the Aspergillus section Circumdati that is inherently resistant to azoles and amphotericin B. Unlike the results seen with many members of Aspergillus section Circumdati, ochratoxin was not detected in filtrates of cultures grown in various media. Our phenotypic and genetic characterization of the new species and the case reports will assist future diagnosis of infection caused by A. tanneri and lead to more appropriate patient management.

AB5075, a Highly Virulent Isolate of Acinetobacter baumannii, as a Model Strain for the Evaluation of Pathogenesis and Antimicrobial Treatments.

UNLABELLED: Acinetobacter baumannii is recognized as an emerging bacterial pathogen because of traits such as prolonged survival in a desiccated state, effective nosocomial transmission, and an inherent ability to acquire antibiotic resistance genes. A pressing need in the field of A. baumannii research is a suitable model strain that is representative of current clinical isolates, is highly virulent in established animal models, and can be genetically manipulated. To identify a suitable strain, a genetically diverse set of recent U.S. military clinical isolates was assessed. Pulsed-field gel electrophoresis and multiplex PCR determined the genetic diversity of 33 A. baumannii isolates. Subsequently, five representative isolates were tested in murine pulmonary and Galleria mellonella models of infection. Infections with one strain, AB5075, were considerably more severe in both animal models than those with other isolates, as there was a significant decrease in survival rates. AB5075 also caused osteomyelitis in a rat open fracture model, while another isolate did not. Additionally, a Tn5 transposon library was successfully generated in AB5075, and the insertion of exogenous genes into the AB5075 chromosome via Tn7 was completed, suggesting that this isolate may be genetically amenable for research purposes. Finally, proof-of-concept experiments with the antibiotic rifampin showed that this strain can be used in animal models to assess therapies under numerous parameters, including survival rates and lung bacterial burden. We propose that AB5075 can serve as a model strain for A. baumannii pathogenesis due to its relatively recent isolation, multidrug resistance, reproducible virulence in animal models, and genetic tractability. IMPORTANCE: The incidence of A. baumannii infections has increased over the last decade, and unfortunately, so has antibiotic resistance in this bacterial species. A. baumannii is now responsible for more than 10% of all hospital-acquired infections in the United States and has a >50% mortality rate in patients with sepsis and pneumonia. Most research on the pathogenicity of A. baumannii focused on isolates that are not truly representative of current multidrug-resistant strains isolated from patients. After screening of a panel of isolates in different in vitro and in vivo assays, the strain AB5075 was selected as more suitable for research because of its antibiotic resistance profile and increased virulence in animal models. Moreover, AB5075 is susceptible to tetracycline and hygromycin, which makes it amenable to genetic manipulation. Taken together, these traits make AB5075 a good candidate for use in studying virulence and pathogenicity of this species and testing novel antimicrobials.