Classification of Ralstonia pickettii biovar 3/'thomasii' strains (Pickett 1994) and of new isolates related to nosocomial recurrent meningitis as Ralstonia mannitolytica sp. nov

Novel Ralstonia species from human infections: improved matrix-assisted laser desorption/ionization time-of-flight mass spectrometry-based identification and analysis of antimicrobial resistance patterns

A collection of 161 Ralstonia isolates, including 90 isolates from persons with cystic fibrosis, 27 isolates from other human clinical samples, 8 isolates from the hospital environment, 7 isolates from industrial samples, and 19 environmental isolates, was subjected to matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) identification and yielded confident species level identification scores for only 62 (39%) of the isolates, including four that proved misidentified subsequently. Whole-genome sequence analysis of 32 representative isolates for which no confident MALDI-TOF MS species level identification was obtained revealed the presence of seven novel Ralstonia species, including three and four that were isolated from cystic fibrosis or other human clinical samples, respectively, and provided the basis for updating an in-house MALDI-TOF MS database. A reanalysis of all mass spectra with the updated MALDI-TOF MS database increased the percentage of isolates with confident species level identification up to 77%. The antimicrobial susceptibility of 30 isolates mainly representing novel human clinical and environmental Ralstonia species was tested toward 17 antimicrobial agents and demonstrated that the novel Ralstonia species were generally multi-resistant, yet susceptible to trimethoprim/sulfamethoxazole, ciprofloxacin, and tigecycline. An analysis of genomic antimicrobial resistance genes in 32 novel and publicly available genome sequences revealed broadly distributed beta-lactam resistance determinants.IMPORTANCEThe present study demonstrated that a commercial matrix-assisted laser desorption/ionization time-of-flight mass spectrometry identification database can be tailored to improve the identification of Ralstonia species. It also revealed the presence of seven novel Ralstonia species, including three and four that were isolated from cystic fibrosis or other human clinical samples, respectively. An analysis of minimum inhibitory concentration values demonstrated that the novel Ralstonia species were generally multi-resistant but susceptible to trimethoprim/sulfamethoxazole, ciprofloxacin, and tigecycline.

Quantitative detection of the Ralstonia solanacearum species complex in soil by qPCR combined with a recombinant internal control strain

IMPORTANCE

DNA-based detection and quantification of soil-borne pathogens, such as the Ralstonia solanacearum species complex (RSSC), plays a vital role in risk assessment, but meanwhile, precise quantification is difficult due to the poor purity and yield of the soil DNA retrieved. The internal sample process control (ISPC) strain RsPC we developed solved this problem and significantly improved the accuracy of quantification of RSSC in different soils. ISPC-based quantitative PCR detection is a method especially suitable for the quantitative detection of microbes in complex matrices (such as soil and sludge) containing various PCR inhibitors and for those not easy to lyse (like Gram-positive bacteria, fungi, and thick-wall cells like resting spores). In addition, the use of ISPC strains removes additional workload on the preparation of high-quality template DNA and facilitates the development of high-throughput quantitative detection techniques for soil microbes.

Bioinformatic Analysis Reveals the Role of Translation Elongation Efficiency Optimisation in the Evolution of Ralstonia Genus

Translation efficiency modulates gene expression in prokaryotes. The comparative analysis of translation elongation efficiency characteristics of Ralstonia genus bacteria genomes revealed that these characteristics diverge in accordance with the phylogeny of Ralstonia. The first branch of this genus is a group of bacteria commonly found in moist environments such as soil and water that includes the species R. mannitolilytica, R. insidiosa, and R. pickettii, which are also described as nosocomial infection pathogens. In contrast, the second branch is plant pathogenic bacteria consisting of R. solanacearum, R. pseudosolanacearum, and R. syzygii. We found that the soil Ralstonia have a significantly lower number and energy of potential secondary structures in mRNA and an increased role of codon usage bias in the optimization of highly expressed genes' translation elongation efficiency, not only compared to phytopathogenic Ralstonia but also to Cupriavidus necator, which is closely related to the Ralstonia genus. The observed alterations in translation elongation efficiency of orthologous genes are also reflected in the difference of potentially highly expressed gene' sets' content among Ralstonia branches with different lifestyles. Analysis of translation elongation efficiency characteristics can be considered a promising approach for studying complex mechanisms that determine the evolution and adaptation of bacteria in various environments.

Ralstonia mannitolilytica Bacteremia Stemming From Frequent Outpatient Intravenous Injections at a Local Clinic

An 83-year-old, male patient was admitted with primary bacteremia caused by Ralstonia mannitolilytica. Before onset, he had been receiving regular injections at a local clinic for abnormal liver function. The present case is the first in which regular injections apparently served as the transmission route for R. mannitolilytica causing bacteremia and demonstrates that this disease can occur in clinics as well as hospitals, raising concerns about the hitherto unnoticed risk of excessive or inappropriate treatments at local clinics.

Infection caused by Cupriavidus gilardii in a convalescent COVID-19 patient

Cupriavidus gilardii is an aerobic, gram-negative bacillus that can opportunistically infect immunocompromised patients or those undergoing invasive procedures. We reported a case caused by C. gilardii in a previously basic healthy 78-year-old male, who had COVID-19 and had used corticosteroids recently. The bacterium was identified as C. gilardii by the metagenomic next-generation sequencing from the patient's bronchoalveolar lavage fluid and blood. In addition, this is the first time that we isolated C. gilardii from bronchoalveolar lavage fluid, which provides clinical experience in rare bacterial infections.

The genus Ralstonia: The new kid on the block

The genus Ralstonia comprises of aerobic, gram-negative, oxidase positive, nonfermentative, largely environmental organisms. They are an emerging pathogen in the hospital setting and are increasingly associated with opportunistic infections and outbreaks. We hereby present a case series of six patients diagnosed with bacteraemia caused by Ralstonia spp. and a brief review of literature. These cases highlight that isolation of a nonfermenting gram-negative bacillus from blood culture of a patient admitted in critical care setting should not be ignored as mere contaminant. Clinicians and microbiologists need to work as a team to combat this novel bug.

Spherical pneumonia caused by Ralstonia mannitolilytica: a case report and literature review

BACKGROUND

Spherical pneumonia is an extremely rare condition that is difficult to diagnose. It is a specific type of lung infection that often manifests as a round or round-like mass on chest imaging. Spherical pneumonia is easily misdiagnosed as a pulmonary tumor; therefore, awareness of this disease must be strengthened.

CASE PRESENTATION

The patient was a 29-year-old female who had persistent cough and sputum for approximately 1 month and fever for 5 days. Chest computed tomography (CT) at our hospital revealed a mass in the lower lobe of the right lung near the hilar region, with obstructive pulmonary atelectasis and obstructive pneumonia. Although lung cancer was suspected, Ralstonia mannitolilytica was detected by metagenomic next-generation sequencing (mNGS) of bronchoalveolar lavage fluid, and no cancer cells or Mycobacterium tuberculosis were detected. Finally, the patient was diagnosed with spherical pneumonia caused by R. mannitolilytica. Anti-infective treatment, symptomatic treatment, and administration of a traditional Chinese medicine decoction were performed based on the syndrome differentiation. After 10 days of treatment, chest CT revealed few lesions in the lower lobe of the right lung, which were significantly reduced compared with those in the past.

CONCLUSIONS

Spherical pneumonia caused by R. mannitolilytica has not yet been reported and differential diagnosis is key in clinical diagnosis. When spherical pneumonia is difficult to diagnose, mNGS may be a better alternative.

Ralstonia chuxiongensis sp. nov., Ralstonia mojiangensis sp. nov., and Ralstonia soli sp. nov., isolated from tobacco fields, are three novel species in the family Burkholderiaceae

Eight Gram-negative, aerobic, motile with paired polar flagella and rod-shaped bacteria were isolated from six tobacco fields in Yunnan, PR China. 16S rRNA gene sequence analysis revealed that all the strains belonged to the genus Ralstonia. Among them, strain 22TCCZM03-6 had an identical 16S rRNA sequence to that of R. wenshanensis 56D2T, and the other strains were closely related to R. pickettii DSM 6297T (98.34–99.86%), R. wenshanensis 56D2T (98.70–99.64%), and R. insidiosa CCUG 46789T (97.34–98.56%). Genome sequencing yielded sizes ranging from 5.17 to 5.72 Mb, with overall G + C contents of 63.3–64.1%. Pairwise genome comparisons showed that strain 22TCCZM03-6 shared average nucleotide identity (ANI) and digital DNA–DNA hybridization (dDDH) values above the species cut-off with R. wenshanensis 56D2T, suggesting that strain 22TCCZM03-6 is a special strain of the R. wenshanensis. Five strains, including 21MJYT02-10T, 21LDWP02-16, 22TCJT01-1, 22TCCZM01-4, and 22TCJT01-2, had ANI values >95% and dDDH values >70% when compared with each other. These five strains had ANI values of 73.32–94.17% and dDDH of 22.0–55.20% with the type strains of the genus Ralstonia individually, supporting these five strains as a novel species in the genus Ralstonia. In addition, strains 21YRMH01-3T and 21MJYT02-11T represent two independent species. They both had ANI and dDDH values below the thresholds for species delineation when compared with the type species of the genus Ralstonia. In strains 21YRMH01-3T and 21MJYT02-10T, the main fatty acids were summed features 3, 8, and C16:0; however, strain 21MJYT02-11T contained C16:0, cyclo-C17:0, and summed features 3 as major fatty acids. The main polar lipids, including diphosphatidylglycerol, phosphatidylglycerol, and phosphatidylethanolamine, were identified from strains 21YRMH01-3T, 21MJYT02-10T, and 21MJYT02-11T. The ubiquinones Q-7 and Q-8 were also detected in these strains, with Q-8 being the predominant quinone. Based on the above data, we propose that the eight strains represent one known species and three novel species in the genus Ralstonia, for which the names Ralstonia chuxiongensis sp. nov., Ralstonia mojiangensis sp. nov., and Ralstonia soli sp. nov. are proposed. The type strains are 21YRMH01-3T (=GDMCC 1.3534T = JCM 35818T), 21MJYT02-10T (=GDMCC 1.3531T = JCM 35816T), and 21MJYT02-11T (=GDMCC 1.3532T = JCM 35817T), respectively.

Proposal to classify Ralstonia solanacearum phylotype I strains as Ralstonia nicotianae sp. nov., and a genomic comparison between members of the genus Ralstonia

A Gram-negative, aerobic, rod-shaped, motile bacterium with multi-flagella, strain RS^T, was isolated from bacterial wilt of tobacco in Yuxi city of Yunnan province, China. The strain contains the major fatty acids of C_16:0, summed feature 3 (C_16:1 ω7c and/or C_16:1 ω6c), and summed feature 8 (C_18:1 ω7c and/or C_18:1 ω6c). The polar lipid profile of strain RS^T consists of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, and unidentified aminophospholipid. Strain RS^T contains ubiquinones Q-7 and Q-8. 16S rRNA gene sequence (1,407 bp) analysis showed that strain RS^T is closely related to members of the genus Ralstonia and shares the highest sequence identities with R. pseudosolanacearum LMG 9673^T (99.50%), R. syzygii subsp. indonesiensis LMG 27703^T (99.50%), R. solanacearum LMG 2299^T (99.28%), and R. syzygii subsp. celebesensis LMG 27706^T (99.21%). The 16S rRNA gene sequence identities between strain RS^T and other members of the genus Ralstonia were below 98.00%. Genome sequencing yielded a genome size of 5.61 Mbp and a G + C content of 67.1 mol%. The genomic comparison showed average nucleotide identity (ANIb) values between strain RS^T and R. pseudosolanacearum LMG 9673^T, R. solanacearum LMG 2299^T, and R. syzygii subsp. indonesiensis UQRS 627^T of 95.23, 89.43, and 91.41%, respectively, and the corresponding digital DNA-DNA hybridization (dDDH) values (yielded by formula 2) were 66.20, 44.80, and 47.50%, respectively. In addition, strains belonging to R. solanacearum phylotype I shared both ANIb and dDDH with strain RS^T above the species cut-off values of 96 and 70%, respectively. The ANIb and dDDH values between the genome sequences from 12 strains of R. solanacearum phylotype III (Current R. pseudosolanacearum) and those of strain RS^T were below the species cut-off values. Based on these data, we concluded that strains of phylotype I, including RS^T, represent a novel species of the genus Ralstonia, for which the name Ralstonia nicotianae sp. nov. is proposed. The type strain of Ralstonia nicotianae sp. nov. is RS^T (=GDMCC 1.3533^T = JCM 35814^T).

Postoperative cerebrospinal fluid infection by Ralstonia mannitolilytica: Two case reports and a literature review

Background

Ralstonia species are Gram-negative bacilli that are commonly found in moist environments, such as water and soil. They are opportunistic human pathogens, particularly found among immunocompromised patients, and are an infrequent cause of infection. The difficulty in correctly identifying and differentiating between Ralstonia species members using routine biochemical methods as well as their resistance to many classes of antibiotics poses a specific diagnostic and therapeutic challenge.

Case Description

We report two cases from our neurosurgical unit complicated by postoperative cerebrospinal fluid infection caused by Ralstonia Mannitolilytica that posed a therapeutic challenge.

Conclusion

Our hypothesis is contaminated irrigation fluids might be a significant cause of post-operative meningitis and prolonged hospital stay.

Ralstonia wenshanensis sp. nov., a novel bacterium isolated from a tobacco field in Yunnan, China

A Gram-negative, aerobic, motile with paired polar flagella and rod-shaped bacterium strain (56D2^T) was isolated from tobacco planting soil in Yunnan, PR China. Major fatty acids were C_{16  :  1} ω7c (summed feature 3), C_{16  :  0} and C_{18  :  1}  ω7c (summed feature 8). The polar lipid profile of strain 56D2^T consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, one unidentified aminophospholipid and one unidentified glycolipid. Moreover, strain 56D2^T contained ubiquinone Q-8 as the sole respiratory quinone. 16S rRNA gene sequence analysis showed that strain 56D2^T was closely related to members of the genus Ralstonia and the two type strains with the highest sequence identities were R. mannitolilytica LMG 6866^T (98.36 %) and R. pickettii K-288^T (98.22 %). The 16S rRNA gene sequence identities between strain 56D2^T and other members of the genus Ralstonia were below 98.00 %. Genome sequencing revealed a genome size of 5.87 Mb and a G+C content of 63.7 mol%. The average nucleotide identity values between strain 56D2^T and R. pickettii K-288^T, R. mannitolilytica LMG 6866 ^T and R. insidiosa CCUG 46789^T were less than 95 %, and the in silico DNA-DNA hybridization values (yielded by formula 2) were less than 70 %. Based on these data, we conclude that strain 56D2^T represents a novel species of the genus Ralstonia, for which the name Ralstonia wenshanensis sp. nov. is proposed. The type strain of Ralstonia wenshanensis sp. nov. is 56D2^T (=CCTCC AB 2021466^T=GDMCC 1.2886^T=JCM 35178^T).

Ralstonia mannitolilytica: an emerging multidrug-resistant opportunistic pathogen in a tertiary care hospital setting

Introduction.

Ralstonia mannitolilytica is a rare opportunistic pathogen capable of causing a serious infection in immunocompromised patients. Our objective was to describe all cases of R. mannitolilytica bloodstream infection identified within 2 years at our tertiary care centre, focusing on clinical characteristics, risk factors, antibiotic sensitivity patterns, management and outcomes.

Case Series.

We compiled a descriptive case series including 14 non-duplicate R. mannitolilytica isolates obtained from bloodstream infection samples from the microbiology laboratory of a tertiary care centre from June 2019 to June 2021. All isolates were initially identified based on their morphological properties and biochemical reactions, and then underwent matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) examination for confirmation of identity. Antibiotic susceptibility testing was performed using the Kirby–Bauer disc diffusion method and Vitek 2. All 14 patients presented with symptoms of fever and/or chills, and a positive blood culture for R. mannitolilytica. After 48 h of incubation, no Ralstonia growth was reported from any of the current environmental or pharmaceutical water samples. Chemotherapy (9/14), mechanical ventilation (4/14), steroid use (2/14) and diabetes mellitus (1/14) were associated risk factors in our patients. The antibiotic sensitivity panel showed maximum resistance to aminoglycosides (64.3%) and no resistance to cefoperazone/sulbactum. Patients received treatment with cefoperazone/sulbactum and meropenem or ceftazidime. Thirteen patients recovered with antibiotic therapy and one patient succumbed to his illness.

Conclusion.

R. mannitolilytica can cause bloodstream infections in immunocompromised patients. It is likely to be missed or underreported due to lack of clinical awareness. MALDI-TOF MS is helpful in rapid identification. R. mannitolilytica is resistant to many routinely used antibiotics, including carbapenems.

Ralstonia pickettii bacteremia in a cardiac surgery patient in Belgrade, Serbia

Ralstonia pickettii is an opportunistic bacterium found in the water environment with an increasing incidence as a nosocomial pathogen. The objectives of this study were to describe R. pickettii bacteremia in a cardiac surgery patient and to evaluate its ability to grow in a saline solution and to form biofilm. The patient in this study underwent mitral and aortic valve replacement surgery with two aortocoronary bypasses. She developed signs of respiratory and renal failure, therefore hemodialysis was started. After 25 days in an intensive care unit, the patient had recurrent episodes of fever with signs of bacteremia. R. pickettii was identified from blood cultures by MALDI-TOF MS. Antimicrobial susceptibility testing was performed using disc diffusion and broth microdilution methods in accordance with EUCAST methodology and results were interpreted following clinical breakpoints for Pseudomonas spp. The isolate was susceptible to all tested antimicrobial agents except aminoglycosides and colistin. Survival of R. pickettii was analyzed in saline solution with four different starting concentrations at 25 °C and 37 °C for six days. Biofilm capacity was tested using the microtiter plate method. R. pickettii showed substantial growth in saline solution, with starting concentration of 2 CFU ml-1 reaching 107 CFU ml-1 after six days. There was no significant difference between growth at 25 °C and 37 °C. This indicates that storage of contaminated solutions at room temperature can enhance the count of R. pickettii. Our strain did not show the capacity to form biofilm. The patient responded well to adequate treatment with ceftazidime, and after 48 days in ICU she was discharged to convalesce.

Ralstonia mannitolilytica sepsis after elective cesarean delivery: a case report

Background

Ralstonia mannitolilytica, a newly emerging opportunistic pathogen worldwide, has been reported to be responsible for human pneumonia, septicemia and meningitis. This is the first report of a case of Ralstonia mannitolilytica sepsis after elective cesarean delivery.

Case presentation

A 25-year-old woman, gravida 1 para 0, was scheduled for an elective cesarean delivery at 39^+ 1 weeks of gestation. Sudden high fever and decreased blood pressure occurred a short time after the operation. Ralstonia mannitolilytica was identified in her blood culture 5 days after the operation. Based on the presence of sepsis and septic shock, massive fluid replacement, blood transfusion, vasoactive agents, imipenem/cilastatin and cefoperazone sulbactam sodium were applied. She was discharged after intensive care without complications.

Conclusions

Although the incidence of sepsis due to Ralstonia mannitolilytica is relatively low, once infection occurs in a puerpera, severe symptoms develop abruptly. Thus, prompt diagnosis and appropriate treatment are key to the cure.

Outbreak of Ralstonia mannitolilytica bacteraemia in patients undergoing haemodialysis at a tertiary hospital in Pretoria, South Africa

Background

Ralstonia species are Gram-negative bacilli of low virulence. These organisms are capable of causing healthcare associated infections through contaminated solutions. In this study, we aimed to determine the source of Ralstonia mannitolilytica bacteraemia in affected patients in a haemodialysis unit.

Methods

Our laboratory noted an increase in cases of bacteraemia caused by Ralstonia mannitililytica between May and June 2016. All affected patients underwent haemodialysis at the haemodialysis unit of an academic hospital. The reverse osmosis filter of the haemodialysis water system was found to be dysfunctional. We collected water for culture at various points of the dialysis system to determine the source of the organism implicated. ERIC-PCR was used to determine relatedness of patient and environmental isolates.

Results

Sixteen patients were found to have Ralstonia mannitolilytica bacteraemia during the outbreak period. We cultured Ralstonia spp. from water collected in the dialysis system. This isolate and patient isolates were found to have the identical molecular banding pattern.

Conclusions

All patients were septic and received directed antibiotic therapy. There was 1 mortality. The source of the R. mannitolilytica infection in these patients was most likely the dialysis water as the identical organism was cultured from the dialysis water and the patients. The hospital management intervened and repaired the dialysis water system following which no further cases of R. mannitolilytca infections were detected. A multidisciplinary approach is required to control healthcare associated infections such as these. Routine maintenance of water systems in the hospital is essential to prevent clinical infections with R.mannitolilytica.

Ralstonia mannitolilytica sepsis: a case report

Background

Ralstonia mannitolilytica is an emerging opportunistic pathogen that is associated with severe disease, including septic shock, meningitis, and renal transplant infections. Reports on this pathogen are limited, however, especially on the African continent.

Case presentation

A 2-year-old Akan child was presented to a hospital in the northeastern part of Ghana with a 1-week history of fever and chills. We identified Ralstonia mannitolilytica in her blood culture using both conventional and 16S ribosomal deoxyribonucleic acid (rDNA) techniques. The patient’s condition improved clinically upon treatment with cefuroxime.

Conclusion

Our report highlights the potential of Ralstonia mannitolilytica to cause sepsis and thus emphasizes the need for improved laboratory diagnosis and evidence for use of appropriate antibiotics in rural settings of Africa, where presumptive treatment using antimicrobial agents is rife.

Outbreak of nonfermentative Gram-negative bacteria (Ralstonia pickettii and Stenotrophomonas maltophilia) in a hemodialysis center

We report a case series of seven patients with nonfermentative Gram-negative bacteria infections in a single dialysis center; four patients with Ralstonia pickettii and three patients with Stenotrophomonas maltophilia. Two of the seven patients were admitted to hospital for intravenous antibiotic treatment, while the rest were treated with oral antibiotics at home. Both the admitted patients had temporary vascular catheter infections from the aforementioned pathogens. We conclude that the outbreak is due to colonization of treated reverse osmosis water, presumably through contamination via polluted filters and compounded by the usage of reprocessed dialysers in the dialysis center. This is especially relevant because contaminated treated water is directly introduced into the blood compartment of the dialysers during reprocessing. In addition, there seems to be a propensity for both organisms to cause prolonged febrile reactions in patients with temporary vascular catheters, likely through the early development of biofilm. Intensification of general sterilization procedures, servicing and replacement of old decrepit components of the water treatment system and temporary cessation of dialyser reuse practice seem to have halted the outbreak. Due to the virulent nature and difficult resistant profile of nonfermentative Gram-negative bacteria, we strongly recommend meticulous vigilance in the surveillance of culture isolates in routine microbiological specimens from dialysis centers, especially if there is a senescent water treatment system and a practice of reprocessing dialysers.

Parvibium lacunae gen. nov., sp. nov., a new member of the family Alcaligenaceae isolated from a freshwater pond

A bacterial strain designated KMB9^T was isolated from a freshwater pond in Taiwan and characterized using a polyphasic taxonomy approach. Cells of strain KMB9^T were Gram-stain-negative, aerobic, poly-β-hydroxybutyrate-accumulating, motile by means of a monopolar flagellum, non-spore-forming and rods surrounded by a thick capsule and forming white-coloured colonies. Growth occurred at 20-40 °C (optimum, 25-37 °C), at pH 6.5-7.5 (optimum, pH 7.0) and with 0-0.5 % NaCl (optimum, 0 %). Phylogenetic analyses based on 16S rRNA gene and four housekeeping gene sequences (recA, rpoA, rpoB and atpD) showed that strain KMB9^T forms a distinct phyletic line within the family Alcaligenaceae, and the levels of 16S rRNA gene sequence similarity to its closest relatives with validly published names were less than 93.3 %. The predominant fatty acids were summed feature 3 (comprising C16 : 1ω7c and/or C16 : 1ω6c), C16 : 0 and C18 : 1ω7c. The major isoprenoid quinone was Q-8. The major polyamine was putrescine. The polar lipid profile revealed the presence of phosphatidylethanolamine, phosphatidylglycerol and several uncharacterized aminophospholipids, aminolipids, phospholipids and lipids. The genomic DNA G+C content of strain KMB9^T was 54.5 mol%. On the basis of the genotypic and phenotypic data, strain KMB9^T represents a novel species of a new genus in the family Alcaligenaceae, for which the name Parvibium lacunae gen. nov., sp. nov. is proposed. The type strain is KMB9^T (=BCRC 81053^T=LMG 30055^T=KCTC 52814^T).

First case report of infection caused by Cupriavidus gilardii in a non-immunocompromised Chinese patient

Cupriavidus gilardii was first identified as an aerobic, gram-negative, glucose-nonfermenting rod. C. gilardii has been characterized as an organism with low pathogenicity that causes opportunistic infections and few case reports of infection caused by this organism previously. We encountered the first case of bloodstream infection caused in China by C. gilardii in a 87-year old man without obvious immunodeficiency. The isolate were identified as C. gilardii by 16S rRNA sequencing. The infected patient was treated according to the laboratory’s antibiogram of this strain. Similar to the case report in Japan, this is the second report of an infection caused by this organism without obvious immunodeficiency, suggesting that C. gilardii exerts its pathogenicity both in immunodeficient and immunocompetent hosts.

A rare case of Ralstonia mannitolilytica infection in an end stage renal patient on maintenance dialysis during municipal water contamination

Ralstonia mannitolilytica is a gram negative soil bacterium. Ralstonia infection though rare, has become the emerging nosocomial pathogens in hospital settings. Various clinical manifestations had been described as well as the mode of transmission. Despite its low virulence factor, it is able to survive under harsh condition and this may potentially cause significant morbidity and mortality especially in immunocompromised patients. Outbreak of Ralstonia mannitolilytica infections in the hospital are typically associated with contaminated medical supplies or instruments. We described here a case of Ralstonia mannitolilytica infection in a dialysis patient that occurred during the municipal reservoir water contamination crisis. In this report, we will also describe the behaviour of Ralstonia genus and its 4 main species, namely R. pickettii, R. solanacearum, R. insidiosa, and R. mannitolilytica and the choices of antibiotic therapy based on literature review.

Sonication contribution to identifying prosthetic joint infection with Ralstonia pickettii: a case report and review of the literature

Background

In the context of an increase number of primary and revision total hip and total knee arthroplasty performed yearly, an increased risk of complication is expected. Prosthetic joint infection (PJI) remains the most common and feared arthroplasty complication. Ralstonia pickettii is a Gram-negative bacterium, that has also been identified in biofilms. It remains an extremely rare cause of PJI. There is no report of an identification of R. pickettii on an extracted spacer loaded with antibiotic.

Case presentation

We present the case of an 83-years-old Caucasian male patient, that underwent a right cemented total hip replacement surgery. The patient is diagnosed with an early PJI with no isolated microorganism. A debridement and change of mobile parts is performed. At the beginning of 2016, the patient in readmitted into the Orthopedic Department for sever, right abdominal and groin pain and elevated serum erythrocyte sedimentation rate and C-reactive protein. A joint aspiration is performed with a negative microbiological examination. A two-stage exchange with long interval management is adopted, and a preformed spacer loaded with gentamicin was implanted. In July 2016, based on the proinflammatory markers evolution, a shift a three-stage exchange strategy is decided. In September 2016, a debridement, and changing of the preformed spacer loaded with gentamicin with another was carried out. Bacteriological examination of the tissues sampled intraoperatively was positive for Pseudomonas aeruginosa. From the sonication fluid, no bacteria were isolated on culture or identified using the bbFISH assay. During the hospitalization period, the patient received i.v. ceftazidime 3x2g/day and p.o. ciprofloxacin 2x750mg/day, antibiotic therapy that was continued after discharge with p.o. ciprofloxacin 2x750mg/day for 6 weeks. In February 2017, a reimplantation of a revision prosthesis is performed. The retrieved spacer is sonicated, and after 4 days of incubation of the sonication fluid, R. pickettii is isolated. A long term antibiotic therapy with cotrimoxazole being prescribed.

Conclusions

Bacteria culture of sonication fluid remains the gold standard in diagnosing prosthetic joint infections. R. pickettii remains an extremely rare cause of prosthetic joint infection. Optimal management of R. pickettii prosthetic joint infections of has not been established.

Ralstonia mannitolilytica infections in an oncologic day ward: description of a cluster among high-risk patients

BACKGROUND

Ralstonia spp, an environmental microorganism, has been occasionally associated with healthcare infections. The aim of this study was to investigate an outbreak caused by Ralstonia mannitolilytica in oncology patients.

METHODS

Case definition: Oncology outpatients attending a day ward, with positive blood and/or central venous catheter (CVC) culture for Ralstonia spp from September 2013 - June 2014. We analysed medical records, procedures and environmental samples. R. mannitolilytica was identified by 16S rRNA sequencing, and typed by Pulsed Field Gel Electrophoresis (PFGE); resistance to carbapenemes was investigated by phenotypic and molecular methods.

RESULTS

The patients (N = 22) had different malignancies and received different therapy; all had a CVC and 16 patients presented chills and/or fever. R. mannitolilytica was isolated from both blood and CVC (n = 12) or only blood (n = 6) or CVC tips (n = 4). The isolates had indistinguishable PFGE profile, and showed resistance to carbapenems. All the isolates were negative for carbapenemase genes while phenotypic tests suggests the presence of an AmpC β-lactamase activity,responsible for carbapenem resistance. All patients had had CVC flushed with saline to keep the venous access pervious or before receiving chemotherapy at various times before the onset of symptoms. After the first four cases occurred, the multi-dose saline bottles used for CVC flushing were replaced with single-dose vials; environmental samples were negative for R. mannitolilytica.

CONCLUSIONS

Although the source of R. mannitolilytica remains unidentified, CVC flushing with contaminated saline solution seems to be the most likely origin of R. mannitolilytica CVC colonization and subsequent infections. In order to prevent similar outbreaks we recommend removal of any CVC that is no longer necessary and the use of single-dose solutions for any parenteral treatment of oncology patients.

Ralstonia mannitolilytica in cystic fibrosis: A new predictor of worse outcomes

Background

Patients with Cystic Fibrosis are subject to repeated respiratory tract infections, with recent increasing isolation of unusual pathogens. Ralstonia species have lately been isolated at our institution, an organism historically frequently misidentified as Burkholderia or Pseudomonas. The prevalence of Ralstonia spp. in cystic fibrosis populations has yet to be determined, along with its clinical implications.

Case presentations

Seven patients out of the 301 followed at our cystic fibrosis clinic have had Ralstonia strains identified in their respiratory tract. Most strains identified were multi-drug resistant. After aquisition of Ralstonia spp., the patients' clinical course was characterized by more frequent and more severe respiratory infections along with prolonged hospitalizations, greater decline of lung function, and greater mortality. The mortality rate in this group of patients was 86%. No other factor that could explain such a dramatic evolution was identified upon review of patient data. Some of the strains involved were recognized as clones on Pulse Field Electrophoresis Gel, raising the question of person-to-person transmission.

Conclusion

New pathogens are identified with the evolution of the microbiota in cystic fibrosis respiratory tracts. In our cohort of patients, acquisition of Ralstonia spp. was associated with dramatic outcomes in terms of disease acceleration and raised mortality rates. It is of critical importance to continue to better define the prevalence and clinical impact of Ralstonia in cystic fibrosis populations.

Development of an in vitro Assay, Based on the BioFilm Ring Test®, for Rapid Profiling of Biofilm-Growing Bacteria

Microbial biofilm represents a major virulence factor associated with chronic and recurrent infections. Pathogenic bacteria embedded in biofilms are highly resistant to environmental and chemical agents, including antibiotics and therefore difficult to eradicate. Thus, reliable tests to assess biofilm formation by bacterial strains as well as the impact of chemicals or antibiotics on biofilm formation represent desirable tools for a most effective therapeutic management and microbiological risk control. Current methods to evaluate biofilm formation are usually time-consuming, costly, and hardly applicable in the clinical setting. The aim of the present study was to develop and assess a simple and reliable in vitro procedure for the characterization of biofilm-producing bacterial strains for future clinical applications based on the BioFilm Ring Test® (BRT) technology. The procedure developed for clinical testing (cBRT) can provide an accurate and timely (5 h) measurement of biofilm formation for the most common pathogenic bacteria seen in clinical practice. The results gathered by the cBRT assay were in agreement with the traditional crystal violet (CV) staining test, according to the κ coefficient test (κ = 0.623). However, the cBRT assay showed higher levels of specificity (92.2%) and accuracy (88.1%) as compared to CV. The results indicate that this procedure offers an easy, rapid and robust assay to test microbial biofilm and a promising tool for clinical microbiology.

Decomposition of plant-sourced carbon compounds by heterotrophic betaproteobacteria isolated from a tropical Costa Rican bromeliad

Betaproteobacteria were the most common isolates from the water‐filled tank of a Costa Rican bromeliad. Isolates included eight species from the orders Neisseriales and Burkholderiales, with close relatives recovered previously from tropical soils, wetlands, freshwater, or in association with plants. Compared to close relatives, the isolates displayed high temperature and comparatively low pH optima, reflecting the tropical, acidic nature of the bromeliad tank. Bromeliad‐associated bacteria most closely related to Chromobacterium, Herbaspirillum, and Aquitalea were all isolated exclusively at pH 6, while Ralstonia, Cupriavidus, and three species of Burkholderia were isolated mostly at pH 4. Activity profiles for the isolates suggest pervasive capabilities for the breakdown of plant‐sourced organics, including d‐galacturonic acid, mannitol, d‐xylose, and l‐phenylalanine, also reflecting a niche dominated by decomposition of leaves from the overlying canopy, which become entrained in the tanks. Metabolic activity profiles were overlapping between the Burkholderiales, isolated at pH 4, and the Neisseriales, isolated at pH 6, suggesting that plant material decomposition, which is presumably the underlying process sustaining the tank community and possibly the plant itself, occurs in the tanks at both pH extremes. These results suggest that bromeliad‐associated betaproteobacteria may play an important role in the cycling of carbon in this unusual aquatic habitat.

Antibacterial Activity of Wild Mushroom Extracts on Bacterial Wilt Pathogen Ralstonia solanacearum

In total, 150 protein extracts from 94 different basidiomycete and ascomycete wild mushroom species were tested for antibacterial activity against the quarantine plant-pathogen bacterium Ralstonia solanacearum. In in vitro microtiter plate assays, 15 extracts with moderate to high antibacterial activities were identified: 11 completely inhibited bacterial growth and 4 showed partial inhibition. Of these 15 extracts, 5 were further tested and 3 extracts slowed disease progression and reduced disease severity in artificially inoculated tomato and potato plants. However, the in vitro activities of the extracts did not always correlate with their in vivo activities, which emphasizes the importance of performing early screening tests also in vivo. Testing of selected extracts against 12 R. solanacearum strains identified 6 with potential for broader applicability. Further analysis of extracts from Amanita phalloides and Clitocybe geotropa showed that the active substances are proteins with an approximate size of 180 kDa. To our knowledge, this is the first in vitro and in vivo study that demonstrates that mushroom protein extracts can be promising for treatment of bacterial wilt caused by R. solanacearum.

Phylogenomic analysis of the genus Ralstonia based on 686 single-copy genes

The genus Ralstonia contains species that are devastating plant pathogens, opportunistic human pathogens, and/or important degraders of xenobiotic and recalcitrant compounds. However, significant nomenclature problems exist, especially for the Ralstonia solanacearum species complex which consists of four phylotypes. Phylogenomics of the Ralstonia genus was investigated via a comprehensive analysis of 39 Ralstonia genomes as well as four genomes of Cupriavidus necator (more commonly known by its previous name Ralstonia eutropha). These data revealed 686 single-copy orthologs that could be extracted from the Ralstonia core-genome and used to reconstruct the phylogeny of the genus Ralstonia. The generated tree has strong bootstrap support for almost all branches. We also estimated the in silico DNA-DNA hybridization (isDDH) and the average nucleotide identity (ANI) values between each genome. Our data confirmed that whole genome sequence data provides a powerful tool to resolve the complex taxonomic questions of the genus Ralstonia, e.g. strains of Ralstonia solanacearum phylotype IIA and IIB may represent two subspecies of R. solanacearum, and strains of R. solanacearum phylotype I and III may be classified into two subspecies of Ralstonia pseudosolanacearum. Recently, strains of R. solanacearum phylotype IV were proposed to be reclassified into different subspecies of Ralstonia syzygii; our study, however, showed that phylotype IV strains had high isDDH values (83.8-96.1 %), indicating it may be not appropriate to classify these closely related strains into different subspecies. We also evaluated the performance of six chromosomal housekeeping genes (gdhA, mutS, adk, leuS, rplB and gyrB) used in Ralstonia phylogenetic inference. The multilocus sequence analysis of these six marker genes was able to reliably infer the phylogenetic relationships of the genus Ralstonia.

Genome Sequence of a Carbapenem-Resistant Strain of Ralstonia mannitolilytica

Ralstonia mannitolilytica, a Gram-negative aerobic bacterium, is an opportunistic human pathogen that is becoming more common in cases of nosocomial infections. We report for the first time the whole-genome sequence analysis of R. mannitolilytica strain MRY14-0246, which carries the intrinsic OXA-443/OXA-22-like and OXA-444/OXA-60-like β-lactamase genes and is resistant to meropenem.

Polyphasic taxonomic revision of the Ralstonia solanacearum species complex: proposal to emend the descriptions of Ralstonia solanacearum and Ralstonia syzygii and reclassify current R. syzygii strains as Ralstonia syzygii subsp. syzygii subsp. nov., R. solanacearum phylotype IV strains as Ralstonia syzygii subsp. indonesiensis subsp. nov., banana blood disease bacterium strains as Ralstonia syzygii subsp. celebesensis subsp. nov. and R. solanacearum phylotype I and III strains as Ralstonia pseudosolanacearum sp. nov

The Ralstonia solanacearum species complex has long been recognized as a group of phenotypically diverse strains that can be subdivided into four phylotypes. Using a polyphasic taxonomic approach on an extensive set of strains, this study provides evidence for a taxonomic and nomenclatural revision of members of this complex. Data obtained from phylogenetic analysis of 16S-23S rRNA ITS gene sequences, 16S-23S rRNA intergenic spacer (ITS) region sequences and partial endoglucanase (egl) gene sequences and DNA-DNA hybridizations demonstrate that the R. solanacearum species complex comprises three genospecies. One of these includes the type strain of Ralstonia solanacearum and consists of strains of R. solanacearum phylotype II only. The second genospecies includes the type strain of Ralstonia syzygii and contains only phylotype IV strains. This genospecies is subdivided into three distinct groups, namely R. syzygii, the causal agent of Sumatra disease on clove trees in Indonesia, R. solanacearum phylotype IV strains isolated from different host plants mostly from Indonesia, and strains of the blood disease bacterium (BDB), the causal agent of the banana blood disease, a bacterial wilt disease in Indonesia that affects bananas and plantains. The last genospecies is composed of R. solanacearum strains that belong to phylotypes I and III. As these genospecies are also supported by phenotypic data that allow the differentiation of the three genospecies, the following taxonomic proposals are made: emendation of the descriptions of Ralstonia solanacearum and Ralstonia syzygii and descriptions of Ralstonia syzygii subsp. nov. (type strain R 001(T) = LMG 10661(T) = DSM 7385(T)) for the current R. syzygii strains, Ralstonia syzygii subsp. indonesiensis subsp. nov. (type strain UQRS 464(T) = LMG 27703(T) = DSM 27478(T)) for the current R. solanacearum phylotype IV strains, Ralstonia syzygii subsp. celebesensis subsp. nov. (type strain UQRS 627(T) = LMG 27706(T) = DSM 27477(T)) for the BDB strains and Ralstonia pseudosolanacearum sp. nov. (type strain UQRS 461(T) = LMG 9673(T) = NCPPB 1029(T)) for the strains of R. solanacearum phylotypes I and III.

Phylogenetic analysis of burkholderia species by multilocus sequence analysis

Burkholderia comprises more than 60 species of environmental, clinical, and agro-biotechnological relevance. Previous phylogenetic analyses of 16S rRNA, recA, gyrB, rpoB, and acdS gene sequences as well as genome sequence comparisons of different Burkholderia species have revealed two major species clusters. In this study, we undertook a multilocus sequence analysis of 77 type and reference strains of Burkholderia using atpD, gltB, lepA, and recA genes in combination with the 16S rRNA gene sequence and employed maximum likelihood and neighbor-joining criteria to test this further. The phylogenetic analysis revealed, with high supporting values, distinct lineages within the genus Burkholderia. The two large groups were named A and B, whereas the B. rhizoxinica/B. endofungorum, and B. andropogonis groups consisted of two and one species, respectively. The group A encompasses several plant-associated and saprophytic bacterial species. The group B comprises the B. cepacia complex (opportunistic human pathogens), the B. pseudomallei subgroup, which includes both human and animal pathogens, and an assemblage of plant pathogenic species. The distinct lineages present in Burkholderia suggest that each group might represent a different genus. However, it will be necessary to analyze the full set of Burkholderia species and explore whether enough phenotypic features exist among the different clusters to propose that these groups should be considered separate genera.

Isolation and characterization of a soluble and thermostable phosphite dehydrogenase from Ralstonia sp. strain 4506

Phosphite dehydrogenase (PtxD), which catalyzes the nearly irreversible oxidation of phosphite to phosphate with the concomitant reduction of NAD(+) to NADH, has great potential for NADH regeneration in industrial biocatalysts. Here, we isolated a soil bacterium, Ralstonia sp. strain 4506, that grew at 45°C on a minimal medium containing phosphite as the sole source of phosphorus. A recombinant PtxD of Ralstonia sp. (PtxD(R4506)) appeared in the soluble fraction in Escherichia coli. The purified PtxD(R4506) showed 6.7-fold greater catalytic efficiency (V(max)/K(m)) than the first characterized PtxD of Pseudomonas stutzeri (PtxD(PS)). Moreover, the purified PtxD(R4506) showed maximum activity at 50°C, and its half-life of thermal inactivation at 45°C was 80.5h, which is approximately 3,450-fold greater than that of PtxD(PS). Therefore, we concluded that PtxD(R4506), which shows high catalytic efficiency, solubility, and thermostability, would be useful for NADH regeneration applications.

Ralstonia syzygii, the Blood Disease Bacterium and some Asian R. solanacearum strains form a single genomic species despite divergent lifestyles

The Ralstonia solanacearum species complex includes R. solanacearum, R. syzygii, and the Blood Disease Bacterium (BDB). All colonize plant xylem vessels and cause wilt diseases, but with significant biological differences. R. solanacearum is a soilborne bacterium that infects the roots of a broad range of plants. R. syzygii causes Sumatra disease of clove trees and is actively transmitted by cercopoid insects. BDB is also pathogenic to a single host, banana, and is transmitted by pollinating insects. Sequencing and DNA-DNA hybridization studies indicated that despite their phenotypic differences, these three plant pathogens are actually very closely related, falling into the Phylotype IV subgroup of the R. solanacearum species complex. To better understand the relationships among these bacteria, we sequenced and annotated the genomes of R. syzygii strain R24 and BDB strain R229. These genomes were compared to strain PSI07, a closely related Phylotype IV tomato isolate of R. solanacearum, and to five additional R. solanacearum genomes. Whole-genome comparisons confirmed previous phylogenetic results: the three phylotype IV strains share more and larger syntenic regions with each other than with other R. solanacearum strains. Furthermore, the genetic distances between strains, assessed by an in-silico equivalent of DNA-DNA hybridization, unambiguously showed that phylotype IV strains of BDB, R. syzygii and R. solanacearum form one genomic species. Based on these comprehensive data we propose a revision of the taxonomy of the R. solanacearum species complex. The BDB and R. syzygii genomes encoded no obvious unique metabolic capacities and contained no evidence of horizontal gene transfer from bacteria occupying similar niches. Genes specific to R. syzygii and BDB were almost all of unknown function or extrachromosomal origin. Thus, the pathogenic life-styles of these organisms are more probably due to ecological adaptation and genomic convergence during vertical evolution than to the acquisition of DNA by horizontal transfer.

Identification of unknown ocular pathogens in clinically suspected eye infections using ribosomal RNA gene sequence analysis

DNA sequence-based identification of pathogens from ocular samples of patients with clinically suspected eye infections was accomplished using 16S and internal transcribed spacer (ITS) ribosomal RNA gene sequence analysis. PCR was positive for 24 of 99 samples tested. Both culture and 16S rDNA sequence analysis identified Pseudomonas aeruginosa, streptococci and Enterobacteriaceae. Isolates misidentified as Burkholderia cepacia by biochemical tests were identified as Ralstonia mannitolilytica by 16S rDNA sequence analysis. Sequence analysis identified the following microorganisms from 19 culture-negative samples: Haemophilus influenzae, Sphingomonas sp., Klebsiella pneumoniae, Staphylococcus haemolyticus, Morganella morganii, Mycobacterium sp., Chryseobacterium sp., Pseudomonas saccharophila (Xanthomonas) and the fungus, Phaeoacremonium inflatipes.

The changing microbial epidemiology in cystic fibrosis

Infection of the airways remains the primary cause of morbidity and mortality in persons with cystic fibrosis (CF). This review describes salient features of the epidemiologies of microbial species that are involved in respiratory tract infection in CF. The apparently expanding spectrum of species causing infection in CF and recent changes in the incidences and prevalences of infection due to specific bacterial, fungal, and viral species are described. The challenges inherent in tracking and interpreting rates of infection in this patient population are discussed.

Fatal infection caused by Cupriavidus gilardii in a child with aplastic anemia

Cupriavidus gilardii is a Gram-negative bacterium that has rarely been associated with human infections. We report a fatal case of sepsis caused by C. gilardii in a previously healthy 12-year-old female.

Airway infection with a novel Cupriavidus species in persons with cystic fibrosis

We describe the recovery and identification of a bacterium that represents a new species of the genus Cupriavidus from cultures of respiratory tract specimens from two patients with cystic fibrosis (CF). The elucidation of the role of this species in CF lung disease will require an evaluation of a greater number of cases.

Monoclonal outbreak of catheter-related bacteraemia by Ralstonia mannitolilytica on two haemato-oncology wards

BACKGROUND

Ralstonia mannitolilytica is a non-fermentative, gram-negative bacterium isolated infrequently from clinical samples. However, within a period of 11 weeks five inpatients of the tertiary care hospital of the University of Tübingen developed clinical signs of infection and R. mannitolilytica was cultivated from blood samples of all patients suggesting an outbreak.

METHODS

Blood cultures and one catheter tip were analysed by standard microbiological procedures. Genetic relatedness of the isolates was investigated by pulsed-field gel electrophoresis. To ascertain the possible source of the outbreak, environmental sampling and challenge-recovery experiments to test filters used for multi-dose solution bottles were performed.

RESULTS

In the present study a monoclonal outbreak with R. mannitolilytica causing catheter-related infection of five haematological patients is reported. Underlying severe diseases with consecutive immunosuppression, permanent indwelling intravenous devices, multiple intravenous applications, and chemotherapy were possible risk factors promoting the infection. Challenge-recovery experiments revealed that R. mannitolilytica to a high extent even passed through Mini-spike Plus filters of pore size 0.2 microm.

CONCLUSION

Although the source of the outbreak could not be identified, it is possible that solutions given intravenously were contaminated. Since R. mannitolilytica had never been isolated in our laboratory before and environmental testings performed were negative, it cannot be excluded that commercial products like drugs, saline solutions or infusion systems (filters) were contaminated.

Evolutionary dynamics of Ralstonia solanacearum

We investigated the genetic diversity, extent of recombination, natural selection, and population divergence of Ralstonia solanacearum samples obtained from sources worldwide. This plant pathogen causes bacterial wilt in many crops and constitutes a serious threat to agricultural production due to its very wide host range and aggressiveness. Five housekeeping genes, dispersed around the chromosome, and three virulence-related genes, located on the megaplasmid, were sequenced from 58 strains belonging to the four major phylogenetic clusters (phylotypes). Whereas genetic variation is high and consistent for all housekeeping loci studied, virulence-related gene sequences are more diverse. Phylogenetic and statistical analyses suggest that this organism is a highly diverse bacterial species containing four major, deeply separated evolutionary lineages (phylotypes I to IV) and a weaker subdivision of phylotype II into two subgroups. Analysis of molecular variations showed that the geographic isolation and spatial distance have been the significant determinants of genetic variation between phylotypes. R. solanacearum displays high clonality for housekeeping genes in all phylotypes (except phylotype III) and significant levels of recombination for the virulence-related egl and hrpB genes, which are limited mainly to phylotype strains III and IV. Finally, genes essential for species survival are under purifying selection, and those directly involved in pathogenesis might be under diversifying selection.

Utilization of capsaicin and vanillylamine as growth substrates by Capsicum (hot pepper)-associated bacteria

Capsaicin contributes to the organoleptic attributes of hot peppers. Here, we show that capsaicin is utilized as a growth nutrient by certain bacteria. Enrichment cultures utilizing capsaicin were successfully initiated using Capsicum-derived plant material or leaves of tomato (a related Solanaceae) as inocula. No other sources of inoculum examined yielded positive enrichments. Of 25 isolates obtained from enrichments: all utilized 8-methylnonanoic acid; nine were found capable of degrading capsaicin as sole carbon and energy source; 11 were found capable of utilizing vanillylamine; but only two strains could use either of these latter two compounds as sole nitrogen source. Phylogenetic analysis of capsaicin degraders revealed them to be strains of Variovorax and Ralstonia, whereas the vanillylamine degraders were strains of Pseudomonas and Variovorax. Neither of the two strains isolated from one enrichment culture originally inoculated with dried pepper fruit was capable of using capsaicin as sole carbon and nitrogen source. However, good growth was achieved under such conditions when the two isolates, a strain of Variovorax paradoxusThat degraded capsaicin when provided with ammonium, and a vanillylamine degrading strain of Pseudomonas putida, were cultured together. A cross-feeding of capsaicin-derived carbon and nitrogen between members of pepper-associated consortia is proposed.

Identification of peptides from human pathogens able to cross-activate an HIV-1-gag-specific CD4+ T cell clone

Antigen recognition by T cells is degenerate both at the MHC and the TCR level. In this study, we analyzed the cross-reactivity of a human HIV-1 gag p24-specific CD4(+) T cell clone obtained from an HIV-1-seronegative donor using a positional scanning synthetic combinatorial peptide library (PS-SCL)-based biometrical analysis. A number of decapeptides able to activate the HIV-1 gag-specific clone were identified and shown to correspond to sequences found in other human pathogens. Two of these peptides activated the T cell clone with the same stimulatory potency as the original HIV-1 gag p24 peptide. These findings show that an HIV-1-specific human T helper clone can react efficiently with peptides from other pathogens and suggest that cellular immune responses identified as being specific for one human pathogen (HIV-1) could arise from exposure to other pathogens.

Use of PCR analyses to define the distribution of Ralstonia species recovered from patients with cystic fibrosis

Two new PCR assays (for Ralstonia species and Ralstonia respiraculi), together with previously published PCR assays, were used to assess Ralstonia isolates recovered from 111 cystic fibrosis patients. Ralstonia mannitolilytica accounted for 46% of isolates, while R. respiraculi and Ralstonia pickettii accounted for 19% and 18%, respectively. Ralstonia basilensis and Ralstonia metallidurans, species not previously recovered from human samples, were also identified.

Comparison of bioMerieux API 20NE and Remel RapID NF Plus, identification systems of type strains of Ralstonia pickettii

A : Comparison of two commercial miniaturized rapid systems for the identification of Ralstonia pickettii strains.

METHODS AND RESULTS

Varying identification results were encountered using the bioMérieux API NE system and the Remel IDS RapID NF Plus commercial systems for R. pickettii. To compare these two systems, eight strains of R. pickettii were purchased from different commercial culture collections. Additionally, 32 industrial and eight clinical isolates, initially identified using the Vitek Junior (bioMérieux) were tested. Total number of isolates tested was 48. The API 20NE identified 29 isolates, as R. pickettii but was unsuccessful with 19 isolates. The Remel IDS RapID NF Plus identified 46 isolates as R. pickettii. One clinical and one industrial isolates was identified as non-R. pickettii with both systems.

CONCLUSIONS

The above results indicate that the use of API 20NE system for examining the identification of R. pickettii strains is inconsistent.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study demonstrated that the RapID NF Plus is more accurate as an inexpensive identification system for the identification of R. pickettii, a potential emerging organism of medically and industrial importance.

Characterization of clinically isolated Ralstonia mannitolilytica strains using random amplification of polymorphic DNA (RAPD) typing and antimicrobial sensitivity, and comparison of the classification efficacy of phenotypic and genotypic assays

Ralstonia mannitolilytica strains isolated between February 2002 and March 2004 from 30 episodes of infection in 26 patients at Vienna University Hospital were characterized. Twenty-four of the episodes occurred within a 7 month period, suggesting they were outbreak-related, although no common source of infection was identified. The isolates were assayed using PCR to confirm species identification. Random amplification of polymorphic DNA (RAPD) typing classified the R. mannitolilytica isolates into four distinct genotypes: A/I, B/II, C/III and D/IV (15, 13, 1 and 1 isolates, respectively). API 20NE, VITEK Gram-negative Identification Card plus (GNI+) and VITEK Gram Negative Bacillus Identification (GNB) yielded negative or no acceptable biochemical profile for 4, 11 and 11 isolates, respectively. None of the isolates acidified D-arabitol or mannitol. Two isolates (7 %) were positive for nitrate reduction. All 30 R. mannitolilytica isolates were resistant to desferrioxamine, and 29 were able to grow on BCSA. The most active compounds in vitro were ciprofloxacin and cefepime, whilst only the genotype D/IV isolate was sensitive to gentamicin and amikacin (the remaining 29 isolates being resistant to both).