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Nocardiosis, caused by Nocardia seriolae, has been a prominent disease in Southeast Asian aquaculture in the last three decades. This granulomatous disease reported in various fish species is responsible for significant economic losses. This study investigated the pathogenicity of N. seriolae in three cultured species in Taiwan: Nile tilapia (omnivore), milkfish (herbivore) and Asian seabass (carnivore). Administration of an infective dose of 1 × 106 CFU/ fish in tilapia, seabass and milkfish demonstrated mortalities of 100%, 90% and 75%, respectively. Additionally, clinical signs namely, granuloma and lesions displayed varying intensities between the groups and pathological scores. Polymerase chain reaction (PCR) amplification specific for N. seriolae was confirmed to be positive (432 bp) using NS1/NG1 primers. Post‐mortem lesions revealed the absence of granulomas in tilapia and milkfish and their presence in the seabass. Interestingly, the gut in tilapia showed an influx of eosinophils suggesting its role during the acute stages of infection. However, post‐challenge, surviving milkfish exhibited granulomatous formations, while surviving seabass progressed toward healing and tissue repair within sampled tissues. Overall, in conclusion, these results demonstrate the versatility in the immunological ability of individual Perciformes to contain this pathogen as a crucial factor that influences its degree of susceptibility. [ABSTRACT FROM AUTHOR]

Nocardia seriolae causes chronic nocardiosis in various marine and freshwater aquatic animals; however, grouper species have rarely been investigated. This study evaluated the pathogenicity of nocardiosis following N. seriolae infection in the orange‐spotted grouper Epinephelus coioides. Nine identified genetic isolates of N. seriolae were tested in vivo using the intraperitoneal method and observed daily for 35 days. The most virulent isolate was then used to evaluate transmission through different routes (intraperitoneal IP, intramuscular IM, oral OR, and immersion IS) in the same fish model and was observed daily for 42 days. The results showed mild variation in virulence among N. seriolae isolates. AOD107132‐2 K and OT103003‐N11 strains displayed the highest and lowest risk virulence, respectively, based on the accumulation and kinetics of mortality. IM and IP administrations showed an early phase response with early mortality by 5 dpc (30%–100%), while slower kinetics of nocardiosis occurred in the OR and IS routes with slow mortality at 35 dpc (4%–8%). Histopathology revealed typical granulomas, confirming the progression of nocardiosis in the diseased fish. These results provide the basis for further studies on the virulence profile of N. seriolae in Taiwan and a well‐suited route of administration in orange‐spotted groupers for further prevention development. [ABSTRACT FROM AUTHOR]

Chronic disease following Nocardia seriolae infection in a wide range of aquatic animals has been reported in many Asian countries and recently in America and Mexico. This study aimed to investigate the epidemiological relationship among N. seriolae isolates in Taiwan by investigating their genotype and enzymatic activities. A total of 66 strains isolated from 14 known and four unknown host fish from five sites in Taiwan were characterized using five combined methods. High genotypic diversity was recognized among the isolates with 10 pulsotypes being identified from the pulsed‐field gel electrophoresis method and 21 reptypes from the repetitive extragenic palindromic amplification method; however, no natural plasmids were detected in this bacterial population. Pulsotypes A8 and RI analysed by PFGE and repPCR, respectively, were found to be predominant within five sites in Taiwan over 17 years of isolation. Enzymatically, the majority of isolates displayed high leucine arylamidase, β‐glucosidase and α‐glucosidase activities but were negative for lipase, α‐galactosidase, β‐glucuronidase, N‐acetyl‐glucosaminidase, α‐mannosidase and α‐fucosidase activities. We identified a strong association between genotype and enzymatic activity since the majority of pulsotypes displayed the same type of enzymatic profile. This study provides comprehensive and potential epidemiological data, which will aid the fish farming activities and prevention method development. [ABSTRACT FROM AUTHOR]

Background: The study aimed to assess the clinical characteristics of patients with nocardiosis, to evaluate the in vitro susceptibility of antimicrobial agents against Nocardia species, and to explore changes in antimicrobial susceptibilities in this era of multidrug resistance.Methods: Nocardia isolates were identified to the species level using matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) and 16S rRNA, hsp65, and secA1 gene sequencing, and minimum inhibitory concentrations (MICs) of 15 antimicrobial agents were assessed with the broth microdilution method.Results: Eighty-nine isolates from 68 patients were identified to species level. The most common species were Nocardia brasiliensis (n = 28, 31.5%), followed by N. farcinica (n = 24, 27%) and N. cyriacigeorgica (n = 16, 18%). Skin and soft tissue were the most common sites of nocardiosis. In multivariate analysis, cutaneous infection (OR, 0.052; p = 0.009), immunosuppressant use (OR, 16.006; p = 0.013) and Charlson combidity index (OR, 1.522; p = 0.029) were significant predictors for death. In total, 98.9% isolates were susceptible to trimethoprim-sulfamethoxazole and linezolid. Further, the MIC range and resistance rate of all Nocardia species to ceftriaxone, imipenem, and amoxicillin-clavulanic acid were found to generally increase over time.Conclusion: Considering that trimethoprim-sulfamethoxazole is effective against most Nocardia species, it is the antibiotic of choice in Taiwan. Besides, amikacin, tigecycline, and linezolid showed high activity against Nocardia species and are thus good alternatives or additional therapies to treat nocardiosis, depending on patient's underlying conditions and site of infection. [ABSTRACT FROM AUTHOR]

The identification and antimicrobial susceptibility of Nocardia spp. are essential for guiding antibiotic treatment. We investigated the species distribution and evaluated the antimicrobial susceptibility of Nocardia species collected in southern Taiwan from 2012 to 2020. A total of 77 Nocardia isolates were collected and identified to the species level using multi-locus sequence analysis (MLSA). The susceptibilities to 15 antibiotics for Nocardia isolates were determined by the broth microdilution method, and the MIC50 and MIC90 for each antibiotic against different species were analyzed. N. cyriacigeorgica was the leading isolate, accounting for 32.5% of all Nocardia isolates, and the prevalence of Nocardia isolates decreased in summer. All of the isolates were susceptible to trimethoprim/sulfamethoxazole, amikacin, and linezolid, whereas 90.9% were non-susceptible to cefepime and imipenem. The phylogenic tree by MLSA showed that the similarity between N. beijingensis and N. asiatica was as high as 99%, 73% between N. niigatensis and N. crassostreae, and 86% between N. cerradoensis and N. cyriacigeorgica. While trimethoprim/sulfamethoxazole, amikacin, and linezolid remained fully active against all of the Nocardia isolates tested, 90.9% of the isolates were non-susceptible to cefepime and imipenem. [ABSTRACT FROM AUTHOR]

Nocardia seriolae is a common pathogen that causes significant economic losses in cultured fish. An outbreak of this pathogen occurred in Taiwan in November 2018, causing cumulative mortality of 0.86% (300 out of 35,000) in a red snapper, Lutjanus erythropterus, population within 20 days. Another outbreak occurred in January 2019, causing cumulative mortality of 8.29% (2,900 out of 35,000) in an East Asian four finger threadfin, Eleutheronema rhadinum, population within 50 days. The most significant gross pathological changes were white nodules, of varying size, in the spleen, kidney and liver. Additionally, ulcers and skin lesions were found in some East Asian four finger threadfin individuals. Identification of microorganisms isolated from the internal organs was verified using 16S rDNA gene analysis and showed 100% sequence identity with N. seriolae (GenBank accession number AF254417 and AY846841). The antidrug profiles of two N. seriolae isolates showed sensitivity to oxytetracycline, doxycycline, lincomycin, erythromycin and florfenicol. Experimental infection with the isolated strains showed highly similar disease symptoms to naturally infected fish for both N. seriolae strains and caused 100% mortality in red snapper within 13 days. The results revealed that N. seriolae isolated from the field was pathogenic to both East Asian four finger threadfin and red snapper. [ABSTRACT FROM AUTHOR]

Abstract: To observe the clinicopathologic and resistance profiles of the Nocardia brasiliensis causing cutaneous nocardiosis in Taiwan, 12 N. brasiliensis isolates were prospectively collected from patients with cutaneous nocardiosis in a hospital during 2002–2012. Clinicopathologic data were obtained, and isolates were identified by biochemical methods and 16S rRNA sequencing. Susceptibilities to 14 antimicrobial compounds were tested. Isolates were further genotyped by sequencing of 16S rRNA, secA1, hsp65, and gyrB genes. The nodulopustular pyoderma associated with sporotrichoid spreading was the most common skin presentations caused by N. brasiliensis. All of the isolates were susceptible to amikacin, gentamicin, tobramycin, piperacillin/tazobactam, and trimethoprim/sulfamethoxazole and resistant to kanamycin, erythromycin, and oxacillin, while susceptibilities to imipenem, vancomycin, penicillin-G, tetracycline, clindamycin, and ciprofloxacin varied among the 12 isolates. GyrB genotyping delineated the 12 isolates into 2 major groups, which was coincident with different single nucleotide substitutions at position 160 (G versus T) of 16S rRNA, different levels of imipenem minimum inhibition concentration (4–32 versus 0.25–0.75 mg/L), and prevalence of lymphadenitis (66.7 versus 16.7%). We have noted that tiny pustular lesions can be the first sign of cutaneous nocardiosis, which we believe has not been previously emphasized. No resistance to trimethoprim and sulfamethoxazole was found; therefore, sulphonamide drugs remain effective for treatment of cutaneous nocardiosis in Taiwan. [Copyright &y& Elsevier]

This multicenter study in Taiwan investigated the clinical presentations of various Nocardia species infections based on 16S rRNA sequence analysis. Patients with nocardiosis in four large medical centers from 1998 to 2010 were included. A total of 100 preserved nonduplicate isolates causing human infection were identified as Nocardia species. Sequencing analysis of 16S rRNA confirmed that 35 of 36 N. asteroides isolates identified by conventional tests were non- asteroides Nocardia species, and that two of 50 N. brasiliensis isolates had also been initially misidentified. N. brasiliensis (50%) was the most common pathogen, followed by N. cyriacigeorgica (18%). In addition, several rare pathogens were identified, including N. asiatica, N. rhamnosiphila, N. abscessus, N. transvalensis, N. elegans, and N. carnea. Primary cutaneous infection was the most common presentation, noted in 55 (55%) patients, while pulmonary infection presented in 26 (26%) patients. The crude mortality rate was 6.7% (6/89), and was lowest for primary cutaneous infection (2.2%) and highest for disseminated disease and pulmonary infection (16.7%). In conclusion, N. brasiliensis and N. cyriacigeorgica were the most common pathogens causing nocardiosis in Taiwan. Molecular methods for identifying Nocardia to the species level are mandatory for better understanding the epidemiology and clinical characteristics of patients with nocardiosis. [ABSTRACT FROM AUTHOR]

Clin Microbiol Infect 2010; 16: 966–972 The genus of Nocardia is rapidly expanding and the species distribution varies with different geographical locations. We retrospectively reviewed the laboratory records of the bacteriology laboratory at National Taiwan University Hospital from January 1998 to June 2008 to identify patients with nocardiosis. During the study period, 164 isolates of Nocardia spp. were identified from 134 patients but only 113 patients had Nocardia infection. Nocardia brasiliensis ( n = 54) was the most common pathogen, followed by N.  asteroides ( n = 36), N. farcinica ( n = 7), N.  flavorosea ( n = 4) , N.  otitidiscaviarum ( n = 3) , N.  nova ( n = 3), N.  beijingensis ( n = 2) and one each of N.  puris, N.  jinanensis and N.  takedensis. The major types of infection were cutaneous infection (56.6%), pulmonary infection (33.6%) and disseminated infection (7.1%). Eighty-eight patients received sulfonamide-containing antibiotic and eight of 100 patients with available data on outcomes died during the episode of nocardiosis. In conclusion, the clinical and microbiological manifestations of Nocardiosis vary with the different Nocardia species. Accurate identification of the species is crucial to make the diagnosis. [ABSTRACT FROM AUTHOR]

Abstract: The phenotypic and genetic characterizations of 92 isolates of fish pathogen Nocardia seriolae from grey mullet (Mugil cephalus), striped bass (Morone saxatilis), crimson snapper (Lutjanus erythropterus), sea bass (Lateolabrax japonicus), largemouth bass (Micropterus salmoides), grouper (Epinephelus spp.), jarbua terapon (Terapon jarbua), snubnose pompano (Trachinotus blochii), and spotted scaf (Scatophagus argus) isolated in Taiwan during 1997–2007 were examined to investigate the epidemiological relationship among isolates. The phenotypic and genetic characterizations were determined by API ZYM and pulsed-field gel electrophoresis (PFGE) analysis, respectively. In the API ZYM test, N. seriolae were divided into alpha-glucosidase-positive and alpha-glucosidase-negative strains. The alpha-glucosidase activity was also investigated by inoculating N. seriolae in a medium containing substrate 4-nitrophenyl-alpha-d-glucopyranoside. Results of the alpha-glucosidase activity obtained by both methods indicate that all the strains had positive reaction with some exception. In PFGE analysis, digestions with restriction enzymes Xba I and Ase I produced 12 and 9 restriction patterns, respectively. The alpha-glucosidase positive strains were assigned to pulsotypes X1–10 and A1–7. Predominant pulsotypes X1 and A1 were obtained from >79% of strains (73 and 78 strains of 92 strains by Xba I and Ase I, respectively), demonstrating a clonal dissemination of N. seriolae in Taiwan. On the other hand, alpha-glucosidase-negative strains were assigned to X11–12 and A8–9, which differed from those of alpha-glucosidase-positive strains in Taiwan. [Copyright &y& Elsevier]

An epizootic in pond cultured three striped tigerfish, Terapon jarbua, in Taiwan was caused by Nocardia seriolae. Diseased fish first showed clinical signs and mortalities in February and March 2003. The cumulative mortality within 2 months was 2.4% (1200 of 50 000) and affected fish were 7 months old with total lengths from 18 to 25 cm. Most affected fish were pale and lethargic with haemorrhages and ulcers on the skin. The most significant gross pathological changes were varying degrees of ascites and enlargement of the spleen, kidney and liver. Obvious white nodules, varying in size, were found in these organs. Bacteria were either coccal or filamentous in appearance, with bead-like forms. Isolates from diseased fish were characterized using the API ZYM (Analytical profile index; Bio Mérieux, France) systems and conventional tests and identified as Nocardia sp. The isolate was designated NS127 and was confirmed as N. seriolae by a polymerase chain reaction assay that gave the expected specific 432 bp amplicon. In addition, its 16S rDNA sequence gave 100% sequence identity with N. seriolae. A partial sequence of the 16S rRNA gene, heat shock protein gene and RNA polymerase gene (rpo B) of NS127 and the type strain of N. seriolae BCRC 13745 formed a monophyletic clade with a high sequence similarity and bootstrap value of 99.9%. White nodules induced in experimental fish were similar to naturally infected cases and N. seriolae was re-isolated on brain heart infusion agar. This is the first report of N. seriolae-infection in three striped tigerfish in aquaculture. [ABSTRACT FROM AUTHOR]