First Case of Psychrobacter sanguinis Bacteremia in a Korean Patient / 대한임상미생물학회지

Psychrobacter sanguinis has been described as a Gram-negative, aerobic coccobacilli originally isolated from environments and seaweed samples. To date, 6 cases of P. sanguinis infection have been reported. A 53-year-old male was admitted with a generalized tonic seizure lasting for 1 minute with loss of consciousness and a mild fever of 37.8℃. A Gram stain revealed Gram-negative, small, and coccobacilli-shaped bacteria on blood culture. Automated microbiology analyzer identification using the BD BACTEC FX (BD Diagnostics, Germany) and VITEK2 (bioMérieux, France) systems indicated the presence of Methylobacterium spp., Aeromonas salmonicida, and the Moraxella group with low discrimination. The GenBank Basic Local Alignment Search Tool and an Ez-Taxon database search revealed that the 16S rRNA gene sequence of the isolate showed 99.30% and 99.88% homology to 859 base-pairs of the corresponding sequences of P. sanguinis, respectively (GenBank accession numbers JX501674.1 and HM212667.1). To the best of our knowledge, this is the first human case of P. sanguinis bacteremia in Korea. It is notable that we identified a case based on blood specimens that previously had been misidentified by a commercially automated identification analyzer. We utilized 16S rRNA gene sequencing as a secondary method for correctly identifying this microorganism.

Molecular characterization of tetracycline- and quinolone-resistant Aeromonas salmonicida isolated in Korea

The antibiotic resistance of 16 Aeromonas (A.) salmonicida strains isolated from diseased fish and environmental samples in Korea from 2006 to 2009 were investigated in this study. Tetracycline or quinolone resistance was observed in eight and 16 of the isolates, respectively, based on the measured minimal inhibitory concentrations. Among the tetracycline-resistant strains, seven of the isolates harbored tetA gene and one isolate harbored tetE gene. Additionally, quinolone-resistance determining regions (QRDRs) consisting of the gyrA and parC genes were amplified and sequenced. Among the quinolone-resistant A. salmonicida strains, 15 harbored point mutations in the gyrA codon 83 which were responsible for the corresponding amino acid substitutions of Ser83-->Arg83 or Ser83-->Asn83. We detected no point mutations in other QRDRs, such as gyrA codons 87 and 92, and parC codons 80 and 84. Genetic similarity was assessed via pulsed-field gel electrophoresis, and the results indicated high clonality among the Korean antibiotic-resistant strains of A. salmonicida.

Development and evaluation of a multiplex PCR assay for simultaneous detection of Flavobacterium psychrophilum, Yersinia ruckeri and Aeromonas salmonicida subsp. salmonicida in culture fisheries

Bacterial cold water disease, enteric red mouth disease and frunculosis are the common bacterial diseases of fish worldwide. The etiologic agents of these diseases are Flavobacterium (F.) psychrophilum, Yersinia (Y.) ruckeri and Aeromonas (A.) salmonicida subsp. salmonicida, respectively. In this study, a multiplex polymerase chain reaction (m-PCR) method with YER8/10-Fer3/4-FP1/3 primer pairs which can identify these fish pathogens simultaneously was developed and optimized. In optimized conditions, neither false specific nor nonspecific amplification occurred. The detection limits of the m-PCR method using DNA extracts from dilutions of pure cultures of bacteria were 35 pg for Y. ruckeri and F. psychrophilum and 70 pg for A. salmonicida subsp. salmonicida. It was determined that 15 CFU Y. ruckeri and F. psychrophilum and 30 CFU A. salmonicida subsp. salmonicida could be detected by m-PCR developed using genomic DNA extracted from dilutions of the suspensions. The detection limits in the presence of tissue debris were 125 CFU for Y. ruckeri and F. psychrophilum and 250 CFU for A. salmonicida subsp. salmonicida. In conclusion, we submit that the m-PCR method developed and optimized in this study can be used for accurate and rapid identification of these bacteria.

Avaliação de bacterina e Lactobacillus plantarum frente à infecção experimental por Vibrio harveyi em pós-larvas de Litopenaeus vannamei / Evaluation of bacterin and Lactobacillus plantarum front an experimental infection of Vibrio harveyi in pos-larvae of Litoenaeus vannamei

Objetivou-se averiguar o efeito da bactéria Lactobacillus plantarum e células inativas das bactérias Vibrio alginolyticus, Aeromonas salmonicida e Pasteurella multocida na sobrevivência larval de Litoenaeus vannamei, no teste de estresse e infecção experimental com Vibrio harveyi. Foram utilizados tanques cônicos de 30 L, povoados com 400 larvas cada, no estádio de pós-larva cinco. Tratamentos em triplicatas foram consistidos de: 1: ração comercial (controle), 2: ração comercial + bacterina via oral na artemia, 3: ração comercial + bacterina via imersãoe 4: ração comercial com inóculo de Lactobacillus plantarum. A aplicação da bacterina ocorreu seis horas antes da infecção e do teste de estresse; enquanto o Lactobacillus plantarum foi administrado por 15 dias antes dos desafios. As pós-larvas do tratamento 4 (ração suplementada com L. plantarum) obtiveram maior índice de sobrevivência no teste de estresse (87,86 ± 2,35%), seguido dos tratamentos 2 e 3 (bacterina via imersão e oral) com 81,54±1,50% e 80,16 ± 2,15% respectivamente, superiores ao índice do controle (72,63 ± 3,34%).Já no desafio com V. harveyi, os animais do grupo tratado com a adição de bacterina via imersão apresentaram maior sobrevivência(79,60 ± 7,12%). As pós-larvas dos tratamentos com bacterina via oral na artêmia e alimentadas com o probiótico L. plantarum,apresentaram sobrevivências de 65,60 ± 5,18% e 69,60 ± 10,43 %,respectivamente, sendo superiores ao controle (56,4 ± 5,58%), quando desafiados com V. harveyi. Os resultados demonstram que ouso de ração com L. plantarum e bacterina aumentam a sobrevivência das pós-larvas de L. vannamei frente aos testes de estresse e infecções experimentais com V. harveyi.

This study aimed to verify the effect of probiotics and inactivated cells of bacterias such as Vibrio alginolyticus, Aeromonas salmonicida and Pasteurella multocida in larvae survival of Litopenaeus vannamei, in stress test and experimental infection with Vibrio harveyi. Conic tanks of 30L, were stocked with 400 post-larvae stage five. Four experimental treatments with triplicates consisted of: 1: commercial feed (control),2: commercial feed plus bacterin by oral administration in artemia, 3:commercial feed plus bacterin by immersion administration, 4:commercial feed with Lactobacillus plantarum inoculation. Bacterin application was conducted 6h before the infection and stress test, while probiotic administration was for 15 days before challenges. In stress test, post-larvae of treatment 4 (commercial feed supplemented with Lactobacillus plantarum) with reached the highest survival rate(87,86 ± 2,35%) followed by the ones of treatment 3 and 2 (bacterimby immersion and bacterim by oral administration in artemia) with 81,54±1, 50% and 80,16 ± 2,15%, respectively, which were superior to the control treatment (72,63 ± 3,34%). Next to V. harveyi challenge, animals from treatment 3 presented the highest survival rate (79,60 ±7,12%) followed by treatments 4 (69,60 ± 10,43%), 2 (65,60 ± 5,18%)and control (56,4 ± 5,58%). All treatments were different from control. The present results demonstrate the possible use of L. plantarum and bacterin as promoters in survival rates of L. vannamei post-larvae in the stress tests and challenges with Vibrio harveyi.