Bacteremia caused by a novel isolate resembling leptotrichia species in a neutropenic patient.
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ABSTRACT:
SUBMITTER: Patel JB
PROVIDER: S-EPMC85034 | biostudies-literature | 1999 Jun
REPOSITORIES: biostudies-literature
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Project description:An obligately anaerobic, fastidious, slowly growing, spiral, gram-negative bacterium was isolated from the blood of a 75-year-old man with acute onset of pyrexia. The patient responded rapidly to appropriate antibiotic therapy. Extensive investigation failed to detect a focus for the infection. Phenotypically, the organism was consistent with Desulfovibrio species. Microscopic investigation revealed an organism with a vibrioid or spirillioid morphology with rapidly progressive motility by means of a single polar flagellum. Biochemically, the organism produced large amounts of H2S and contained desulfovirdin. The 16S rRNA gene sequence of the organism was found to be most similar to those of members of the genus Desulfovibrio, with identical sequence homology to the newly proposed species described by Tee et al. (W. Tee, M. Dyall-Smith, W. Woods, and D. Eisen, J. Clin. Microbiol. 34:1760-1764, 1996). This is a second unrelated isolation of this novel species from two widely different locations in Australia. The two isolates show some phenotypic differences, indicating that they are different strains of the same species.
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Project description:AIMS:To characterise a strain of Gram negative aerobic straight or slightly curved rods (HKU3) isolated from the blood culture of a 9 year old Chinese boy with neutropenic fever and pseudobacteraemia. METHODS:The isolate was phenotypically investigated by standard biochemical methods using conventional biochemical tests, scanning electron microscopy, and transmission electron microscopy. Genotypically, the 16S rRNA gene of the bacterium was amplified by the polymerase chain reaction (PCR) and sequenced. The sequence of the PCR product was compared with known 16S rRNA gene sequences in the Genbank by multiple sequence alignment. The G + C content was determined by thermal denaturation. A phylogenetic tree was constructed by the PileUp method. RESULTS:The cells of the bacterial strain were aerobic, sporulating, Gram negative straight or slight curved rods. The bacterium grew on horse blood agar as non-haemolytic, grey colonies of 1 mm in diameter after 24 hours of incubation at 37 degrees C in ambient air. No enhancement of growth was seen in 5% CO(2). It grew at 50 degrees C as pinpoint colonies after 72 hours of incubation, but did not grow at 65 degrees C or on MacConkey agar. It was non-motile. It produced catalase (weakly positive) and cytochrome oxidase. It reduced nitrate, produced beta galactosidase, hydrolysed esculin, and utilised sodium acetate. A scanning electron micrograph of the bacterium showed straight or slightly curved rods. A transmission electron micrograph of the cell wall of the bacterium revealed multiple electron dense layers, including the outer membrane, middle murein layer, and inner cytoplasmic membrane, compatible with its Gram smear appearance. 16S rRNA gene sequencing showed that there were 7.7%, 8.0%, 8.2%, and 8.6% differences between the 16S rRNA gene sequence of the bacterium and those of Paenibacillus macerans, Paenibacillus borealis, Bacillus ehimensis, and Paenibacillus amylolyticus, respectively. The mean (SD) G + C content of the bacterium was 47.6 (2.1) mol%. Phylogenetically, it belongs to the genus paenibacillus (previously called group 3 bacillus). CONCLUSIONS:A bacterium that exhibited phenotypic and genotypic characteristics that are very different from closely related members of paenibacillus was the cause of pseudobacteraemia in a patient with neutropenic fever. A new species, Paenibacillus hongkongensis sp. nov. is proposed, for which HKU3 is the type strain.
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Project description:We describe the laboratory identification of Leptotrichia species from clinical isolates collected over a six-year period. Five isolates from blood cultures were identified as Leptotrichia species. Gram stain showed large, fusiform, gram-negative or -variable bacilli. Identification based on biochemical testing was unsuccessful; however, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry proved to be a useful tool for identifying Leptotrichia species to the genus level. Species level identification was successfully achieved by using 16S ribosomal RNA gene sequencing.
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Project description:Leptotrichia spp. are anaerobic, pencil-shaped, Gram-negative rods that are part of the normal oral and intestinal human flora. Although not typically considered pathogenic, invasive Leptotrichia infections have been reported in immunosuppressed patients. A perceived rise in the identification of Leptotrichia spp. at our institution prompted a retrospective evaluation of these infections. Laboratory and clinical records were reviewed to identify Leptotrichia culture-positive patients. Over a 5-year period, 68 Leptotrichia-positive specimens were identified. Of these, 21% (14/68) were identified in original samples submitted from 13 different patients at our institution, and the remainder (79% [54/68]) were unknown isolates referred from outside hospitals for molecular identification. All in-house Leptotrichia were identified from blood cultures. Only 64% (9/14) of these grew on solid media, and 5 were a part of polymicrobial bacteremias containing other enteric pathogens. All local patients were receiving chemotherapy and a majority received hematopoietic stem cell transplant (HSCT) (11/13). All had neutropenic fever with symptoms of mucositis and/or enteritis. Most of the HSCT patients (73% [8/11]) were autologous recipients hospitalized after recent high-dose chemotherapy for multiple myeloma. L. hongkongensis, a novel species, was found in the majority of myeloma cases (63% [5/8]). In conclusion, we suggest that Leptotrichia spp. may be an underappreciated cause of bacteremia, particularly in multiple myeloma patients receiving cytotoxic chemotherapy for autologous HSCT. In our cohort, these infections were associated with neutropenic fever from an enteric source, and most isolates remained sensitive to standard antibiotics.
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Project description:A straight, non-sporulating, Gram-variable bacillus (HKU24(T)) was recovered from the blood culture of a patient with metastatic breast carcinoma. After repeated subculturing in BACTEC Plus Anaerobic/F blood culture broth, HKU24(T) grew on brucella agar as non-hemolytic, pinpoint colonies after 96 h of incubation at 37 degrees C in an anaerobic environment and aerobic environment with 5% CO2. Growth was enhanced with a streak of Staphylococcus aureus. HKU24(T) was non-motile and catalase-negative, but positive for alkaline phosphatase, beta-glucosidase, and alpha-glucosidase. It hydrolyzed phenylphosphonate and reduced resazurin. 16S rRNA, groEL, gyrB, recA, and rpoB sequencing showed that HKU24(T) occupies a distinct phylogenetic position among the Leptotrichia species, being most closely related to Leptotrichia trevisanii. Using HKU24(T) groEL, gyrB, recA, and rpoB gene-specific primers, fragments of these genes were amplified from one of 20 oral specimens. Based on phenotypic and genotypic characteristics, we propose a new species, Leptotrichia hongkongensis sp. nov., to describe this bacterium.
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Project description:This study is conducted to investigate the clinical characteristics of patients with bacteremia caused by Aeromonas species.Patients with bacteremia caused by Aeromonas species during the period 2009 to 2013 were identified from a computerized database of a regional hospital in southern Taiwan. The medical records of these patients were retrospectively reviewed.A total of 91 patients with bacteremia due to Aeromonas species were identified. In addition to 16 (17.6%) primary bacteremia, the most common source of secondary infection is peritonitis (n = 27, 29.7%), followed by biliary tract infection (n = 18, 19.8%), and SSTI (n = 12, 13.2%), pneumonia (n = 9, 9.9%), catheter-related bloodstream infection (n = 5, 5.5%), and genitourinary tract infection (n = 4, 4.4%). A. hydrophila (n = 35, 38.5%) was the most common pathogen, followed by A. veronii biovar sobria (n = 31, 34.1%), A. caviae (n = 14, 15.4%), and A. veronii biovar veronii (n = 9, 9.9%). Forty-three (47.3%) patients were classified as healthcare-associated infections (HCAI) causes by Aeromonas species, and patients with HCAI were more likely to have cancer, and receive immunosuppressant than patients with community-acquired bacteremia. The overall outcomes, including rate of ICU admission, acute respiratory failure, and mortality were 33.3%, 28.6%, and 23.1%, respectively. Multivariate analysis showed that the in-hospital day mortality was significantly associated only with underlying cancer (P <.001), and initial shock (P <.001).Aeromonas species should be considered one of the causative pathogens of healthcare-associated bacteremia, especially in immunocompromised patients. In addition, it can be associated with high fatality. Cancer and initial shock were the poor prognostic factors.
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