Nocardiosis from 1888 to 2017

Pulmonary Nocardiosis Caused by Nocardia exalbida in a Patient with Lung Cancer and Radiation Pneumonitis: A Case Report and Literature Review

We report a case of Nocardia exalbida (N.exalbida)-induced pneumonia in a 70-year old Japanese man with lung cancer and radiation pneumonitis. He initially received doripenem (1.5 g/day) for pneumonia treatment, and N.exalbida was identified by a clone library analysis of bronchoalveolar lavage fluid obtained from the pneumonia lesion. The doripenem dosage was therefore increased to 3.0 g/day with adjunctive trimethoprim/sulfamethoxazole, and his pneumonia improved. N. exalbida is susceptible to antibiotics; thus, in nocardiosis, N. exalbida infection might be associated with a good response to treatment, although its clinical findings are non-specific and similar to those of other Nocardia infections.

Nocardia infections in solid organ transplantation: Guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation

These updated guidelines from the Infectious Diseases Community of Practice of the American Society of Transplantation review the diagnosis, prevention, and management of Nocardia infections after solid organ transplantation (SOT). Nocardia infections have increased in the last two decades, likely due to improved detection and identification methods and an expanding immunocompromised population. The risk of developing nocardiosis after transplantation varies with the type of organ transplanted and the immunosuppression regimen used. Nocardia infection most commonly involves the lung. Disseminated infection can occur, with spread to the bloodstream, skin, or central nervous system. Early recognition of the infection and initial appropriate treatment is important to achieve good outcomes. Species identification and antimicrobial susceptibility testing are strongly recommended, as inter- and intraspecies susceptibility patterns can vary. Sulfonamide is the first-line treatment of Nocardia infections, and combination therapy with at least two antimicrobial agents should be used initially for disseminated or severe nocardiosis. Trimethoprim-sulfamethoxazole (TMP-SMX) prophylaxis may be helpful in preventing Nocardia infection after SOT.

Nocardia cyriacigeorgica and Aspergillus Co-infection in a Patient with Giant-cell Arteritis

Immunosuppressed patients are at greater risk of unusual infections. The authors present the case of a woman with giant-cell arteritis, on oral steroids, who developed cavitating pneumonia due to co-infection with Aspergillus and Nocardia. Reports of such co-infection are rare in the literature. This case highlights the importance of considering rare pathogens in immunosuppressed patients who present with non-specific symptoms, as well as the impact of such pathogens on clinical management. Another important issue is the need for prophylaxis against Nocardia spp. in immunocompromised patients.

LEARNING POINTS

In patients with vasculitis on systemic corticosteroid therapy or other immunosuppressive treatment, suspicion of uncommon infection should increase in parallel with the cumulative dose of these drugs.Obtaining an accurate diagnosis and early treatment is essential, but can be very challenging.Regular prophylactic therapy should be considered. However, more research is needed to determine whether higher doses of TMP/SMX would provide adequate coverage.

Transcriptome analysis of immune-related gene expression in hybrid snakehead (Channa maculata ♀ × Channa argus ♂) after challenge with Nocardia seriolae

Hybrid snakehead fish (Channa maculata ♀ × Channa argus ♂), a new species used in freshwater aquaculture in China, is the common host of an epizootic bacterial infection by Nocardia seriolae. However, the information on the functions and mechanisms of hybrid snakehead immune pathways with the N. seriolae infection is limited. Thus, the peripheral blood lymphocytes from hybrid snakehead were used for transcriptome analysis to understand the host immune response after challenge with N. seriolae. A total of 49,839,332 and 50,059,283 raw reads were obtained from the N. seriolae-challenged group (Ns group) and phosphate-buffered saline control group (Ctr group), respectively. The 75.50% and 74.25% reads from the Ns and Ctr groups were matched to reference genomic sequence after cleaning the raw reads, respectively. Additionally, there were 2892 significant differentially expressed genes (DEGs) among the 17,196 expressed genes between the Ns and Ctr groups, including 1387 upregulated and 1505 downregulated genes. All the DEGs were classified into three gene ontology categories, and 2502 DEGs had significant matches, which were allocated to 246 Kyoto Encyclopedia of Genes and Genomes pathways. Immune-related genes were detected from immune system pathways among the top 20 enriched pathways. Moreover, the regulation of several observed effective genes was confirmed by real-time quantitative polymerase chain reaction. Altogether, this study offers deep-sequence data of hybrid snakehead peripheral blood lymphocyte via transcriptome analysis and lays the foundation for further study on the immunogenetics of hybrid snakehead. Moreover, it provides insights into the pathogenic mechanism of N. seriolae, facilitating the prevention and treatment of fish nocardiosis.

Current taxonomy of Rhodococcus species and their role in infections

Rhodococcus is a genus of obligate aerobic, Gram-positive, partially acid-fast, catalase-positive, non-motile, and none-endospore bacteria. The genus Rhodococcus was first introduced by Zopf. This bacterium can be isolated from various sources of the environment and can grow well in non-selective medium. A large number of phenotypic characterizations are used to compare different species of the genus Rhodococcus, and these tests are not suitable for accurate identification at the genus and species level. Among nucleic acid-based methods, the most powerful target gene for revealing reliable phylogenetic relationships is 16S ribosomal RNA gene (16S rRNA gene) sequence analysis, but this gene is unable to differentiation some of Rhodococcus species. To date, whole genome sequencing analysis has solved taxonomic complexities in this genus. Rhodococcus equi is the major cause of foal pneumonia, and its implication in human health is related to cases in immunocompromised patients. Macrolide family together with rifampicin is one of the most effective antibiotic agents for treatment rhodococcal infections.