Fatal case of endocarditis due to Weissella confusa

Characterization of Weissella Species during a 3-Year Observational Study - An Emerging Threat

Weissella species are mistaken for Lactobacillus or Leuconostoc because of their Gram-staining property and resistance to vancomycin. In this study, we aimed to evaluate the demographic pattern, presenting symptoms, risk factors, associated pathologies, and clinical outcomes in patients with Weissella infection. We also analyzed the antibiotic susceptibility pattern of the Weissella species isolated. This retrospective observational study was done from January 2021 to August 2023 in a tertiary care referral center in Uttar Pradesh. All Weissella species isolated from blood cultures or cerebrospinal fluid (CSF) samples during this period were included in the study. Twenty-four-hour growth from a positive blood culture or CSF sample was identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Demographic and clinical details of the patients were extracted from the hospital information system. Kirby-Bauer disk diffusion was used for antibiotic susceptibility testing. During the 3-year study, 13 isolates of Weissella species were identified in our laboratory. Among the patients, male predominance was seen. The age range of the patients was 5-53 years. The samples were blood samples (n = 11) and CSF samples (n = 2). Of these isolates, 12 (92.3%) were identified as Weissella confusa and 1 (7.69%) was identified as Weissella viridescens. Common risk factors were anemia, prolonged hospital stay, indwelling catheter, chemotherapy, and chronic kidney disease. All the isolates in this study were sensitive to amikacin, daptomycin, amoxicillin-clavulanate, minocycline, and linezolid. Death was attributed to Weissella infection in three patients. Weissella species are opportunistic organisms that need to be identified quickly and precisely to guarantee the right course of treatment.

The Controversial Nature of Some Non-Starter Lactic Acid Bacteria Actively Participating in Cheese Ripening

This mini review deals with some controversial non-starter lactic acid bacteria (NSLAB) species known to be both human and animal pathogens but also health-promoting and probiotic. The focus is on Lactococcus garvieae, two Streptococcus species (S. uberis and S. parauberis), four Weissella species (W. hellenica, W. confusa, W. paramesenteroides, and W. cibaria), and Mammalicoccus sciuri, which worldwide, are often found within the microbiotas of different kinds of cheese, mainly traditional artisanal cheeses made from raw milk and/or relying on environmental bacteria for their ripening. Based on literature data, the virulence and health-promoting effects of these bacteria are examined, and some of the mechanisms of these actions are reviewed. Additionally, their possible roles in cheese ripening are also discussed. The analysis of the literature data available so far showed that, in general, the pathogenic and the beneficial strains, despite belonging to the same species, show somewhat different genetic constitutions. Yet, when the safety of a given strain is assessed, genomic analysis on its own is not enough, and a polyphasic approach including additional physiological and functional tests is needed.

A Case of Weissella confusa Isolated from Blood of a Patient with Coronary Heart Disease Complicated with Gastrointestinal Bleeding

Introduction

W. confusa has been known to cause various human infections. It is naturally resistant to vancomycin and is difficult to identify using traditional methods, which may lead to misidentification and delay treatment.

Case Presentation

We present a case of a 42-year-old male patient with gastrointestinal bleeding and coronary heart disease who developed sepsis caused by Weissella confusa. The patient's blood cultures showed the presence of gram-positive coccobacilli, later identified as W. confusa through matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Antimicrobial susceptibility testing revealed that W. confusa had low minimum inhibitory concentrations (MICs) for some drugs (eg, ampicillin) and higher MICs for others (eg, cefotaxime). Empirical treatment with vancomycin was initially started, but after obtaining the identification and susceptibility results, the treatment was switched to meropenem combined with daptomycin, resulting in a successful outcome.

Conclusion

Weissella confusa bacteremia is relatively rare, and accurate pathogenic diagnosis is essential for effective clinical treatment.

A Novel Case of Weissella confusa Infective Endocarditis of a Bio-Prosthetic Valve: Management and Treatment

Weissella confusa is a rare gram-positive, non-spore-forming, catalase-negative, gram-positive coccobacillus, and a pleomorphic gram-positive rod (GPR) often misidentified as Lactobacillus genus. It was first discovered in 1993 and is becoming identified due to the increasing use of DNA sequencing. The true incidence of this species has likely been underestimated and it has been implicated in poly-microbial bacteremia. We present an exceedingly rare case of its presentation found incidentally in a patient with a bio-prosthetic aortic and mitral valve that was successfully managed and treated.

Weissella confusa Causing Vancomycin-Resistant Septicemia Infection in a Pediatric Patient: A Case Report From a University Teaching Hospital in North India

Weissella confusa is a Gram-positive coccus usually found in the microbiota of humans and the environment. Different studies quote that it has caused infections in humans under unfavourable conditions. A case report causing septicemia in an 11-year-old male patient diagnosed with acute pancreatitis and having acute respiratory distress syndrome (ARDS) is presented. The patient was successfully treated with ceftazidime and a piperacillin-tazobactam combination after confirmation of bacteria by matrix-assisted laser desorption and ionisation-time of flight (MALDI-TOF-MS) and antimicrobial sensitivity testing (AST) performed as per the latest Clinical and Laboratory Standard Institute (CLSI) guidelines. The patient was discharged asymptomatically after drainage of fluid and was managed conservatively. Correct identification by the automated method is important for this species and also to find its mode of infection. Because of its similarities to other vancomycin-resistant cocci, isolates of this species might be difficult to identify, leading to drug resistance. A literature review in tabulated form is summarised.

The Weissella Genus: Clinically Treatable Bacteria with Antimicrobial/Probiotic Effects on Inflammation and Cancer

Weissella is a genus earlier considered a member of the family Leuconostocaceae, which was reclassified into the family Lactobacillaceae in 1993. Recently, there have been studies emphasizing the probiotic and anti-inflammatory potential of various species of Weissella, of which W. confusa and W. cibaria are the most representative. Other species within this genus include: W. paramesenteroides, W. viridescens, W. halotolerans, W. minor, W. kandleri, W. soli, W. ghanensis, W. hellenica, W. thailandensis, W. fabalis, W. cryptocerci, W. koreensis, W. beninensis, W. fabaria, W. oryzae, W. ceti, W. uvarum, W. bombi, W. sagaensis, W. kimchi, W. muntiaci, W. jogaejeotgali, W. coleopterorum, W. hanii, W. salipiscis, and W. diestrammenae. Weissella confusa, W. paramesenteroides, W. koreensis, and W. cibaria are among the few species that have been isolated from human samples, although the identification of these and other species is possible using metagenomics, as we have shown for inflammatory bowel disease (IBD) and healthy controls. We were able to isolate Weissella in gut-associated bacteria (post 24 h food deprivation and laxatives). Other sources of isolation include fermented food, soil, and skin/gut/saliva of insects/animals. With the potential for hospital and industrial applications, there is a concern about possible infections. Herein, we present the current applications of Weissella on its antimicrobial and anti-inflammatory mechanistic effects, the predisposing factors (e.g., vancomycin) for pathogenicity in humans, and the antimicrobials used in patients. To address the medical concerns, we examined 28 case reports focused on W. confusa and found that 78.5% of infections were bacteremia (of which 7 were fatal; 1 for lack of treatment), 8 were associated with underlying malignancies, and 8 with gastrointestinal procedures/diseases of which 2 were Crohn’s disease patients. In cases of a successful resolution, commonly administered antibiotics included: cephalosporin, ampicillin, piperacillin-tazobactam, and daptomycin. Despite reports of Weissella-related infections, the evolving mechanistic findings suggest that Weissella are clinically treatable bacteria with emerging antimicrobial and probiotic benefits ranging from oral health, skin care, obesity, and inflammatory diseases to cancer.

Watch out for the Saurkraut: Weissella confusa endocarditis in a liver transplant candidate

Content available: Audio Recording.

Weissella confusa with thermostable β-hemolytic exopolysaccharide

Consuming cooked meat contaminated with bacteria that carry thermostable hemolytic exopolysaccharide (ESP), could lead to severe diseases. Culture of a 5- h boiled sample of meat goulash on blood agar showed growth of a gram positive rod-shaped, mucoid and hemolytic bacterium. Biochemical tests and amplification of 1500 bp product of 16S rDNA and sequencing revealed bacterial identity as Weissella confusa. After 1 h boiling of bacterial suspension, they were alive and hemolytic, increased in volume and aggregated. After 8 h boiling of bacterial suspension with coverslip, live bacteria showed hemolysis, clustered and adhered to coverslip. Bacterial bacteriocin and hemolytic activities remained unchanged upon autoclaving. Purified bacterial EPS retained hemolytic activity after autoclaving. Boiling contaminated meat had no negative impact on viability of heat-stable W. confusa and its hemolytic EPS. Thermostable hemolytic EPS protected W. confusa from excessive heat. Hygienic practice in butcheries and kitchens are necessary to eliminate bacterial contaminants.

Diversity and Antimicrobial Activity towards Listeria spp. and Escherichia coli among Lactic Acid Bacteria Isolated from Ready-to-Eat Seafood

Biopreservation is a food preservation technology using microorganisms and/or their inherent antimicrobial metabolites to inhibit undesirable microorganisms. The aim of the present study was to explore the diversity and antimicrobial activity of lactic acid bacteria (LAB) strains (n = 99) isolated from ready-to-eat (RTE) seafood (cold-smoked salmon (CSS), gravlax, and sushi) towards two strains of Listeria monocytogenes (CCUG 15527, F11), Listeria innocua (CCUG 15531) and Escherichia coli (CCUG 38079). The LAB strains were assigned to five different genera (Carnobacterium spp., Lactobacillus spp., Leuconostoc spp., Weissella spp., and Enterococcus sp.) by sequencing a 1150 bp stretch of the 16S rRNA gene. A significant association between the seafood source and the distribution of LAB genera was found (p < 0.001), of which Leuconostoc spp. were most prevalent in sushi and Carnobacterium sp. and Lactobacillus sp. were most frequently isolated from CSS and gravlax. Antimicrobial activity among the LAB was significantly affected by LAB genera (F= 117.91, p < 0.001, one-way ANOVA), product of origin (F = 3.47, p < 0.05), and target (F = 4.64, p = 0.003). LAB isolated from sushi demonstrated a significantly higher antimicrobial effect than LAB from CSS and gravlax (p < 0.05). In general, a significantly higher antimicrobial activity was found towards Listeria spp. than E. coli (p < 0.05). However, Leuconostoc spp. demonstrated similar antimicrobial effects towards E. coli and Listeria spp., except for L. monocytogenes F11 being more sensitive (p < 0.05). This study suggested that seafood-derived LAB strains could be selected for technological application in RTE seafood systems.

Safety demonstration of a microbial species for use in the food chain: Weissella confusa

Due to their traditional use in food fermentation process for centuries, microbial food cultures are considered to have a safe history of use. A specific microbial risk assessment is therefore rarely conducted for fermented foods and their food cultures, inoculated or naturally present. Some of those food cultures have been also considered for their potential health effect as probiotic strain candidates, for which a specific safety demonstration process has been proposed by a joint expert report of FAO and WHO. The European Food Safety Authority (EFSA) Biohazard panel also provides an approach for evaluating the safety of a strain to be added in the food chain, the Qualified Presumption of Safety (QPS). Weissella confusa, former taxon Lactobacillus confusus, is a food culture characterized in the fermentation process of sourdough. Some strains have been recently proposed for their probiotic potential. The species is also documented in recent infection case reports. It is considered nevertheless to be opportunistic as underlying factors have been suggested to explain the infection. We report here the microbial risk assessment of the species, by studying a collection of 26 food and 17 clinical isolates of Weissella confusa. The phenotypic study, genomic characterization and bibliographical survey will allow us to conclude about the safety of the species and confirm its use for food fermentation and consider specific strains for demonstration of their respective health effects as probiotic candidates.

A case report of polymicrobial bacteremia with Weissella confusa and comparison of previous treatment for successful recovery with a review of the literature

Weissella confusa is a Gram-positive coccus and a commensal bacterium of the human gastrointestinal tract with a potential to cause invasive infections. We report the presence of W. confusa in the blood of a 25-year-old male patient with Crohn’s disease, short bowel syndrome treated with home parenteral nutrition, and a history of recurrent bloodstream infections, admitted to our hospital with fever and malaise. A polymicrobial culture of W. confusa and Aeromonas hydrophila was identified from blood, for which treatment with meropenem and metronidazole was initiated. The literature was searched for previous cases of infection with W. confusa. In total, 14 reports describing infection of 28 patients were found, most cases presenting with bacteremia. The previous reports have described variable susceptibility to antibiotics; however, all were reported to be vancomycin resistant. Because of its similarities to other vancomycin-resistant cocci, isolates of W. confusa might be difficult to identify with traditional methods. Infection may be facilitated by its natural vancomycin resistance, leading to severe infection in hosts with underlying diseases. We describe the treatment of previous cases of infection and suggest treatment methods shown effective in other cases. Vancomycin is often used as treatment of infection with Gram-positive organisms, but this may need to be reevaluated, as several pathogenic bacteria are intrinsically vancomycin resistant. A review on reported treatments of bacteremia by W. confusa suggests the use of daptomycin, amoxicillin-clavulanate or piperacillin/tazobactam as recommendable antibiotic regimens.

Isolation and Preliminary Screening of a Weissella confusa Strain from Giant Panda (Ailuropoda melanoleuca)

Weissella confusa has recently received attention for its probiotic potential. Some W. confusa and Weissella cibaria strains isolated from fermented foods show favorable probiotic effects. However, the probiotic properties of W. confusa isolated from giant panda remain unreported to date. Thus, this study isolated a W. confusa strain from giant panda feces and then investigated its characteristics and probiotic properties. A lactic acid bacteria strain was isolated from giant panda fecal samples. The isolated strain was screened by in vitro probiotic property tests, including in vitro antimicrobial test, antioxidant test, surface hydrophobicity, and stress resistance. On the basis of biochemical identification and 16S rDNA sequencing, the W. confusa strain was identified as BSP201703. This Weissella confusa strain can survive at pH 2 and 0.3% (w/v) concentration of bile salt environment and inhibit common intestinal pathogens. It also possesses an in vitro antioxidant capacity, a high auto-aggregation ability, and a high surface hydrophobicity. BSP201703 might serve as a probiotic to giant pandas.

Genome Sequence of a Weissella confusa Strain Isolated from the First Reported Case of Neonatal Sepsis in an Equid

The genome of a Weissella confusa strain isolated from a foal with sepsis is reported. Weissella confusa inhabits feces and causes disease in immunocompromised humans and animals. It is important for veterinarians to be aware of the pathogenic ability of these bacteria due to the unknown potential for zoonotic transmission.

The genome of a Weissella confusa strain isolated from a foal with sepsis is reported. Weissella confusa inhabits feces and causes disease in immunocompromised humans and animals. It is important for veterinarians to be aware of the pathogenic ability of these bacteria due to the unknown potential for zoonotic transmission.

Literature-based safety assessment of an agriculture- and animal-associated microorganism: Weissella confusa

Although Weissella confusa was established as a species over 25 years ago, it has been understudied until very recently. Several independent observations have driven the recent interest in this important microorganism. First, this Leuconostoc-like species of Lactic Acid Bacteria is associated with agricultural environments, many spontaneous food fermentations-especially carbohydrate-rich vegetable fermentations-and silage. Second, Weissella confusa are members of the autochthonous microbiota of healthy humans and livestock. Third, Weissella confusa-in a strain-specific fashion-are postulated to be good candidates for the development of novel direct-fed microbial products. Fourth, Weissella confusa-in a strain-specific fashion-have been described as opportunistic pathogens-especially in immunocompromised individuals. Last, a distantly related species (Weissella ceti) is the etiologic agent of weissellosis, a disease that affects farmed fish that are important for commercial aquaculture. The purpose of this literature-based safety assessment is to consolidate findings from primary research related to Weissella confusa and its natural associations with and effects on animals, humans, and their agricultural environments. Based on these assessments, it is reasonable to conclude that many Weissella confusa are safe for use in direct-fed microbial products for poultry.

Why Are Weissella spp. Not Used as Commercial Starter Cultures for Food Fermentation?

Among other fermentation processes, lactic acid fermentation is a valuable process which enhances the safety, nutritional and sensory properties of food. The use of starters is recommended compared to spontaneous fermentation, from a safety point of view but also to ensure a better control of product functional and sensory properties. Starters are used for dairy products, sourdough, wine, meat, sauerkraut and homemade foods and beverages from dairy or vegetal origin. Among lactic acid bacteria, Lactobacillus, Lactococcus, Leuconostoc, Streptococcus and Pediococcus are the majors genera used as starters whereas Weissella is not. Weissella spp. are frequently isolated from spontaneous fermented foods and participate to the characteristics of the fermented product. They possess a large set of functional and technological properties, which can enhance safety, nutritional and sensory characteristics of food. Particularly, Weissella cibaria and Weissella confusa have been described as high producers of exo-polysaccharides, which exhibit texturizing properties. Numerous bacteriocins have been purified from Weissella hellenica strains and may be used as bio-preservative. Some Weissella strains are able to decarboxylate polymeric phenolic compounds resulting in a better bioavailability. Other Weissella strains showed resistance to low pH and bile salts and were isolated from healthy human feces, suggesting their potential as probiotics. Despite all these features, the use of Weissella spp. as commercial starters remained non-investigated. Potential biogenic amine production, antibiotic resistance pattern or infection hazard partly explains this neglecting. Besides, Weissella spp. are not recognized as GRAS (Generally Recognized As Safe). However, Weissella spp. are potential powerful starters for food fermentation as well as Lactococcus, Leuconostoc or Lactobacillus species.

Effects of maturity stage and lactic acid bacteria on the fermentation quality and aerobic stability of Siberian wildrye silage

It is difficult to make good quality of silage from alpine gramineous from the Qinghai Tibetan plateau. The effects of lactic acid bacteria (LAB) on the fermentation quality and aerobic stability of Siberian wildrye silage were studied in southeast of the Qinghai Tibetan plateau. Siberian wildrye materials were freshly cut at the sprouting stage, flowering stage, and milky stage. Silage was prepared by using a small‐scale silage fermentation system (bag silos). Lactobacillus plantarum (LP, 5 × 10⁸ cfu/kg FM), Lactobacillus buchneri (LB, 5 × 10⁸ cfu/kg FM) and their mixture (LP+LB, 5 × 10⁸ cfu/kg FM) as silage additives were separately added to ensiled forages, and no additive served as control (CK). These bag silos were kept at room temperature (<15°C), and the silage qualities were analyzed after 60 days of ensiling. The number of indigenous LAB on fresh materials was less than that of yeasts and molds, and LAB species showed specification adapted to low temperature. LAB inoculated silages had lower (P < 0.05) pH value, NH₃‐N/TN and butyric acid content compared with control silage. Silage treated with LB had higher contents of acetic acid, propionic acid, WSC and CP. However, the aerobic stability of silages inoculated with LAB did not differ significantly between stages (P > 0.05). When fermentation characteristics, chemical composition, and aerobic stability were considered, treatment with L. plantarum resulted in high quality of Siberian wildrye silage harvested at the flowering stage in the alpine region.

Comparative genome analysis of Weissella ceti, an emerging pathogen of farm-raised rainbow trout

Background

The genus Weissella belongs to the lactic acid bacteria and includes 18 currently identified species, predominantly isolated from fermented food but rarely from cases of bacteremia in animals. Recently, a new species, designated Weissella ceti, has been correlated with hemorrhagic illness in farm-raised rainbow trout in China, Brazil, and the USA, with high transmission and mortality rates during outbreaks. Although W. ceti is an important emerging veterinary pathogen, little is known about its genomic features or virulence mechanisms. To better understand these and to characterize the species, we have previously sequenced the genomes of W. ceti strains WS08, WS74, and WS105, isolated from different rainbow trout farms in Brazil and displaying different pulsed-field gel electrophoresis patterns. Here, we present a comparative analysis of the three previously sequenced genomes of W. ceti strains from Brazil along with W. ceti NC36 from the USA and those of other Weissella species.

Results

Phylogenomic and orthology-based analyses both showed a high-similarity in the genetic structure of these W. ceti strains. This structure is corroborated by the highly syntenic order of their genes and the neutral evolution inferred from Tajima’s D. A whole-genome multilocus sequence typing analysis distinguished strains WS08 and NC36 from strains WS74 and WS105. We predicted 10 putative genomic islands (GEI), among which PAIs 3a and 3b are phage sequences that occur only in WS105 and WS74, respectively, whereas PAI 1 is species specific.

Conclusions

We identified several genes putatively involved in the basic processes of bacterial physiology and pathogenesis, including survival in aquatic environment, adherence in the host, spread inside the host, resistance to immune-system-mediated stresses, and antibiotic resistance. These data provide new insights in the molecular epidemiology and host adaptation for this emerging pathogen in aquaculture.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-2324-4) contains supplementary material, which is available to authorized users.

Identification and significance of Weissella species infections

Weissella spp. are non-spore forming, catalase-negative, gram-positive coccobacilli. They are often misidentified by traditional and commercial phenotypic identification methods as Lactobacillus spp. or Lactobacillus-like organisms. Weissella spp. were previously grouped along with Lactobacillus spp., Leuconostoc spp., and Pediococcus spp. Utilization of more sensitive methods like DNA sequencing or Matrix-Assisted Laser Desorption/Ionization Time of Flight Mass Spectrometry (MALDI-TOF MS) has facilitated identification of Weissella as a unique genus. Nineteen species have been identified to date. W. confusa, W. cibaria, and W. viridescens are the only species isolated from humans. The true prevalence of Weissella spp. continues to be probably underestimated. Weissella spp. strains have been isolated from a wide range of habitats including raw milk, feces, fermented cereals, and vegetables. Weisella is believed to be a rare cause of usually nonfatal infections in humans, and is often considered a contaminant. However, in recent years, Weissella spp. have been implicated in bacteremia, abscesses, prosthetic joint infections, and infective endocarditis. Alterations of the gut flora from surgery or chemotherapy are believed to facilitate translocation of Weissella spp. due to disruption of the mucosal barrier, predisposing the host to infection with this organism. Implications of the isolation of Weissella spp. from blood must be interpreted in context of underlying risk factors. Weissella spp. are inherently resistant to vancomycin. Therefore, early consideraton of the pathogenic role of this bacteria and choice of alternate therapy is important to assure better outcomes.

The controversial nature of the Weissella genus: technological and functional aspects versus whole genome analysis-based pathogenic potential for their application in food and health

Despite the use of several Weissella (W.) strains for biotechnological and probiotic purposes, certain species of this genus were found to act as opportunistic pathogens, while strains of W. ceti were recognized to be pathogenic for farmed rainbow trout. Herein, we investigated the pathogenic potential of weissellas based on in silico analyses of the 13 whole genome sequences available to date in the NCBI database. Our screening allowed us to find several virulence determinants such as collagen adhesins, aggregation substances, mucus-binding proteins, and hemolysins in some species. Moreover, we detected several antibiotic resistance-encoding genes, whose presence could increase the potential pathogenicity of some strains, but should not be regarded as an excluding trait for beneficial weissellas, as long as these genes are not present on mobile genetic elements. Thus, selection of weissellas intended to be used as starters or for biotechnological or probiotic purposes should be investigated regarding their safety aspects on a strain to strain basis, preferably also by genome sequencing, since nucleotide sequence heterogeneity in virulence and antibiotic resistance genes makes PCR-based screening unreliable for safety assessments. In this sense, the application of W. confusa and W. cibaria strains as starter cultures or as probiotics should be approached with caution, by carefully selecting strains that lack pathogenic potential.

The genus Weissella: taxonomy, ecology and biotechnological potential

Bacteria assigned to the genus Weissella are Gram-positive, catalase-negative, non-endospore forming cells with coccoid or rod-shaped morphology (Collins et al., 1993; Björkroth et al., 2009, 2014) and belong to the group of bacteria generally known as lactic acid bacteria. Phylogenetically, the Weissella belong to the Firmicutes, class Bacilli, order Lactobacillales and family Leuconostocaceae (Collins et al., 1993). They are obligately heterofermentative, producing CO2 from carbohydrate metabolism with either d(-)-, or a mixture of d(-)- and l(+)- lactic acid and acetic acid as major end products from sugar metabolism. To date, there are 19 validly described Weissella species known. Weissella spp. have been isolated from and occur in a wide range of habitats, e.g., on the skin and in the milk and feces of animals, from saliva, breast milk, feces and vagina of humans, from plants and vegetables, as well as from a variety of fermented foods such as European sourdoughs and Asian and African traditional fermented foods. Thus, apart from a perceived technical role of certain Weissella species involved in such traditional fermentations, specific Weissella strains are also receiving attention as potential probiotics, and strain development of particularly W. cibaria strains is receiving attention because of their high probiotic potential for controlling periodontal disease. Moreover, W. confusa and W. cibaria strains are known to produce copius amounts of novel, non-digestible oligosaccharides and extracellular polysaccharides, mainly dextran. These polymers are receiving increased attention for their potential application as prebiotics and for a wide range of industrial applications, predominantly for bakeries and for the production of cereal-based fermented functional beverages. On the detrimental side, strains of certain Weissella species, e.g., of W. viridescens, W. cibaria and W. confusa, are known as opportunistic pathogens involved in human infections while strains of W. ceti have been recently recongnized as etiological agent of "weissellosis," which is a disease affecting farmed rainbow trouts. Bacteria belonging to this species thus are important both from a technological, as well as from a medical point of view, and both aspects should be taken into account in any envisaged biotechnological applications.

Complete Genome Sequences of Fish Pathogenic Weissella ceti Strains WS74 and WS105

We describe here the genome sequencing and annotation of Weissella ceti strains WS74 and WS105, isolated from diseased rainbow trout in Brazil. The two genomes were sequenced with an Ion Torrent personal genome machine (PGM) using a fragment library. The genomes of strains WS74 and WS105 consist of circular chromosomes 1,389,513 bp and 1,390,396 bp long, respectively, both presenting a G+C content of 40.75%.

A confusing case - Weissella confusa prosthetic joint infection: A case report and review of the literature

This article describes a case involving a 94-year-old woman with an infection of her knee, which had previously undergone total knee arthroplasty. Following culture of aspirate from the knee, the causative organism was tentatively identified as a Lactobacillus species. The infection was later determined to be caused by Weissella confusa. The authors discuss the difficulties in identifying W confusa and present a literature review of infections caused by the species.

The authors describe the first case of Weissella confusa infection of a prosthetic joint. Identification of the pathogen required 16S ribosomal RNA sequencing of isolates obtained on two separate occasions during the assessment of an elderly woman with a painful, swollen knee following total knee arthroplasty. A review of reported human infections due to W confusa are summarized, and risk factors and pitfalls in the application of empirical antimicrobial therapy pending definitive microbiological identification are discussed.

Weissella confusa: problems with identification of an opportunistic pathogen that has been found in fermented foods and proposed as a probiotic

Weissella confusa is found in fermented foods and has been suggested as a probiotic, but also causes sepsis and other serious infections in humans and animals. The incidence of human infections is underestimated partly due to confusion with viridans streptococci and partly due to difficulty making a definitive identification, even if the organism is recognized to belong to another genus, owing to the inability of commercial organism systems to identify it. We report our experiences identifying W. confusa isolated from two immune-compromised patients, both of whom developed sepsis with this organism. Two MicroScan gram positive combination panels, could not identify the organism because they did not have W. confusa in their data bases, but did not provide a false identification. Other laboratorians have reported failure to identify or false identifications of W. confusa with other commercial systems. W. confusa is in the data base of the RapID™ Str panel (Remel), which gave three incorrect, high probability results (≥95%). 16S rDNA sequencing identified the isolates as W. confusa. Maldi-Tof, performed by two of our reference laboratories, also correctly identified both isolates. Use of W. confusa as a probiotic should be approached with caution because its true incidence as an opportunisitic pathogen is unknown.

Recovery and identification of bacterial DNA from illicit drugs

Bacterial infections, including Bacillus anthracis (anthrax), are a common risk associated with illicit drug use, particularly among injecting drug users. There is, therefore, an urgent need to survey illicit drugs used for injection for the presence of bacteria and provide valuable information to health and forensic authorities. The objectives of this study were to develop a method for the extraction of bacterial DNA from illicit drugs and conduct a metagenomic survey of heroin and methamphetamine seized in the Australian Capital Territory during 2002-2011 for the presence of pathogens. Trends or patterns in drug contamination and their health implications for injecting drug users were also investigated. Methods based on the ChargeSwitch(®)gDNA mini kit (Invitrogen), QIAamp DNA extraction mini kit (QIAGEN) with and without bead-beating, and an organic phenol/chloroform extraction with ethanol precipitation were assessed for the recovery efficiency of both free and cellular bacterial DNA. Bacteria were identified using polymerase chain reaction and electrospray ionization-mass spectrometry (PCR/ESI-MS). An isopropanol pre-wash to remove traces of the drug and diluents, followed by a modified ChargeSwitch(®) method, was found to efficiently lyse cells and extract free and cellular DNA from Gram-positive and Gram-negative bacteria in heroin and methamphetamine which could then be identified by PCR/ESI-MS. Analysis of 12 heroin samples revealed the presence of DNA from species of Comamonas, Weissella, Bacillus, Streptococcus and Arthrobacter. No organisms were detected in the nine methamphetamine samples analysed. This study develops a method to extract and identify Gram-positive and Gram-negative bacteria from illicit drugs and demonstrates the presence of a range of bacterial pathogens in seized drug samples. These results will prove valuable for future work investigating trends or patterns in drug contamination and their health implications for injecting drug users as well as enabling forensic links between seizures to be examined.

Weissella confusa septicemia in a foal

Weissella confusa is a Gram-positive bacterium that has been identified in environmental and food samples from around the world. Rare cases of bacteremia in immunocompromised people have been reported. A 2-day-old foal was presented for weakness and suspected sepsis. Blood culture yielded pure growth of a Gram-positive coccobacillus, which was identified as W. confusa through sequencing of the 16S ribosomal DNA. Although the foal initially responded to antimicrobial therapy with ceftiofur and metronidazole, it later developed septic complications of the right tarsocrural joint and right digital flexor tendon sheath and was euthanized. Postmortem examination and histology revealed subcutaneous icterus, severe diffuse interstitial pneumonia, septic synovitis, necrotizing vasculitis with marked thrombosis and hemorrhage in the medial digital vessels of the right hind limb, and ischemic necrosis of the right hind hoof laminae. Gram-positive, coccobacilli were observed in the vascular lesion.

Genome Sequence of Weissella ceti NC36, an Emerging Pathogen of Farmed Rainbow Trout in the United States

Novel Weissella sp. bacteria have recently been reported to be associated with disease outbreaks in cultured rainbow trout (Oncorhynchus mykiss) at commercial farms in China, Brazil, and the United States. Here we present the first genome sequence of this novel Weissella species, isolated from the southeastern United States.

Weissella sp. outbreaks in commercial rainbow trout (Oncorhynchus mykiss) farms in Brazil

The genus Weissella contains 14 bacterial species that usually occur in nutrient-rich environments and in fermented foods and beverages. Outbreaks of hemorrhagic septicemia were reported in three commercial rainbow trout (Oncorhynchus mykiss) farms in Brazil in 2008 and 2009. Seventy-seven Gram-positive isolates were obtained from 41 diseased fish from these farms. The bacterial strains were identified as Weissella at the genus level using biochemical tests, Weissella genus-specific PCR, and 16S rRNA sequencing. To evaluate potential routes of infection, rainbow trout juveniles were experimentally infected with the pathogen. In addition, the resistance of the pathogen to five antibiotics was tested, and provisional epidemiological cut-off values were calculated using the normalized resistance interpretation (NRI). All isolates presented similar phenotypic profiles and positive reactions for Weissella genus-specific PCR. The 16S rRNA sequences of the Brazilian strains showed 100% similarity with sequences of Chinese isolates that previously were identified as the first case of Weissella sp. infection in fish. The disease was successfully reproduced in the laboratory by intraperitoneal injection, immersion, and cohabitation between diseased and healthy fish. All isolates were resistant to sulfonamide, and based on NRI analysis, one, two, and three isolates were classified as non-wild-type (NWT) for erythromycin, oxytetracycline, and norfloxacin, respectively. This is the first description of multiple cases of Weissella sp. infection in rainbow trout farms outside of China, of infectious routes for the disease, and of provisional epidemiological cut-off values for resistance of these bacteria to four antibiotics.

Weissella confusa: a rare cause of vancomycin-resistant Gram-positive bacteraemia

We describe a case of bacteraemia caused by Weissella confusa in a 48-year-old male who was operated on for adenocarcinoma of the gastro-oesophageal junction and maintained on total parenteral nutrition. Blood cultures were positive for a vancomycin-resistant streptococcus-like organism which was identified as W. confusa by 16S rRNA gene sequencing.

Weissella confusa bacteremia in a liver transplant patient with hepatic artery thrombosis

A 54-year-old man with a history of nonalcoholic steatohepatitis and hepatocellular carcinoma presented 2 months after an orthotopic liver transplant with fever and abdominal pain. Two weeks earlier, he had an hepatic artery thrombosis and a biliary stricture, for which an hepatic artery stent and a biliary stent were placed. Laboratory workup was significant for leukocyte count of 7800/mcL with 92% segmented neutrophils, hemoglobin 9.4 g/dL, alanine aminotransferase 98 U/L, aspartate aminotransferase 72 U/L, alkaline phosphatase 358 U/L, albumin 2.8 mg/dL, and total bilirubin 1.6 mg/dL. A computed tomography scan of the abdomen and pelvis revealed multiple small fluid collections in the liver consistent with bilomas, and an hepatic angiogram showed complete occlusion of the common hepatic artery. Two sets of blood cultures were positive for an organism initially identified by MicroScan(®) analysis as an α-hemolytic Streptococcus species that was resistant to vancomycin. Further testing confirmed the organism as Weissella confusa 2 days later. W. confusa is a gram-positive coccobacillus that may be misidentified as a Lactobacillus when cultured. It is commonly found in sewage, carrots, sugar cane, fermented foods, and intestinal flora. Although only 4 cases of clinical infection with W. confusa have been described previously, W. confusa has been isolated from the stool of liver transplant patients, and may be an underreported cause of infection owing to improper identification. As it can cause clinical infection in these immunosuppressed hosts, identification of this organism is paramount because it is vancomycin resistant, and incorrect identification could lead to improper antimicrobial selection and ultimately worsened patient morbidity or mortality.

Weissella confusa: an unexpected cause of vancomycin-resistant gram-positive bacteremia in immunocompromised hosts

We report the first case of Weissella confusa bacteremia in an allogeneic hematopoietic stem cell transplant patient. After engraftment and discharge, the patient returned with fever and graft failure and was started on an empiric regimen of aztreonam and vancomycin. A blood culture grew an alpha-hemolytic, gram-positive coccus forming pairs and chains, originally thought to be a viridans Streptococcus and a skin contaminant. The isolation of the organism from multiple blood cultures, and the presence of vancomycin resistance prompted identification and additional susceptibility testing. The RapID(™) Str panel, which has W. confusa in its database, provided multiple incorrect identifications. The MicroScan WalkAway 96 SI, using PC-20 or -29 panels, also did not identify this bacterium, because it is not in their database. The organism was identified as W. confusa by 16S rDNA sequencing. Antibiotic susceptibility determination by Etest revealed vancomycin resistance and daptomycin susceptibility. Therapy was changed to daptomycin, and the infection resolved. Additionally, W. confusa sepsis, with multiple positive blood cultures, developed in a patient in the burn unit at our medical center. The patient's blood cultures remained positive until vancomycin was discontinued and daptomycin therapy initiated. Infections with vancomycin-resistant, gram-positive cocci are emerging among immuno compromised hosts. Under appropriate circumstances, clinicians need to request that the laboratory perform susceptibility testing and accurate identification, by nucleic acid sequencing if necessary. Sequencing of 16S rDNA is an important tool in the accurate identification of unusual pathogens.

Bacteraemia caused by Weissella confusa at a university hospital in Taiwan, 1997-2007

Human infections caused by Weissella confusa are rarely reported. Ten patients with bacteraemia caused by W. confusa who were treated at a tertiary-care hospital in Taiwan during 1997-2007 were studied. All isolates were initially misidentified as various Lactobacillus and Leuconostoc species by two commercial automated identification methods, and were confirmed to be W. confusa by 16S rRNA sequencing analysis. MICs of these isolates for ten antimicrobial agents were determined by the agar dilution method. The characteristics of these patients included underlying malignancy (n = 4), presence of a central catheter (n = 6), surgery within the previous 3 months (n = 4) and concomitant polymicrobial bacteraemia (n = 5, 50%). Mortality was directly attributed to bacteraemia in two patients. All isolates exhibited high trimethoprim-sulphamethoxazole and ceftazidime MICs (≥ 128 mg/L) and were inhibited by linezolid, daptomycin, ceftobiprole and tigecycline at 4, 0.12, 2 and 0.12 mg/L, respectively. In conclusion, W. confusa should be included in the list of organisms causing bacteraemia in immunocompromised hosts. Novel antibiotics, including daptomycin, moxifloxacin, doripenem and tigecycline, exert good activity against W. confusa.

Polyphasic taxonomic studies of lactic acid bacteria associated with Tunisian fermented meat based on the heterogeneity of the 16S-23S rRNA gene intergenic spacer region

The objective of this work was to investigate the structure and diversity of lactic acid bacteria (LAB) communities in traditionally fermented meat collected from different areas of Tunisia. A polyphasic study, which involves phenotypic tests and ribosomal DNA-based techniques, was used to identify Gram-positive and catalase-negative isolates. PCR amplification of the 16S-23S rDNA ISR of 102 isolates and other reference LAB strains gave (1) one type of rrn operon (M-ISR) for lactococci, (2) two types of rrn operon (S-ISR and M-ISR) for enterococci, (3) two types of rrn operon (S-ISR and L-ISR) for Lactobacilli, and (4) three PCR amplicons (S-ISR, M-ISR, and L-ISR) obtained for Pediococcus spp. and Weissella genus. The clustering and comparison of ISR-RFLP profiles given by the isolates with those given by reference LAB strains, allowed their identification as Lactococcus lactis, Enterococcus faecium, Enterococcus faecalis, Enterococcus sanguinicola, Enterococcus hawaiiensis, Lactobacillus sakei, Lactobacillus curvatus, Lactobacillus plantarum, Lactobacillus alimentarius, Pediococcus pentosaceus, and Weissella confusa. Combined 16S-23S rDNA ISR and RFLP patterns can be considered as a good potential target for a rapid and reliable differentiation between isolates of LAB and provided further information on the organization of their rrn operons.

Identification of lactic acid bacteria isolated from human blood cultures

Fifteen lactic acid bacterial strains were isolated from blood cultures from 15 different patients in the Faculty Hospital in Brno, Czech Republic. All strains were identified using biochemical tests and repetitive PCR using the (GTG)5 primer. Doubtful identification results were confirmed by whole-cell protein analysis. The strains were assigned to the genera Lactobacillus (eight strains representing seven species), Leuconostoc (six strains representing four species) and Weissella (one strain). Antibiotic susceptibility testing was performed using the E-test and revealed high-level resistance to cotrimoxazol, metronidazole, vancomycin and teicoplanin, but nearly all strains were susceptible to erythromycin, clindamycin, ampicillin and penicillin.

Bacterial diversity in aortic aneurysms determined by 16S ribosomal RNA gene analysis

BACKGROUND

Aortic aneurysms are common vascular conditions that cause considerable morbidity and mortality. Understanding of the mechanisms involved in the pathogenesis of the condition remains limited. Recently, infection has been suggested as possible contributor in the development of the disease. The aim of the present study was to examine aortic aneurysms for the presence of bacterial DNA using polymerase chain reaction (PCR) targeting the 16S ribosomal RNA (rRNA) gene, followed by cloning and sequencing.

METHODS

Universal eubacterial primers were used to amplify 16S rRNA bacterial genes in 10 specimens from arterial walls of aortic aneurysms. Subsequently, PCR amplicons were cloned into Escherichia coli and sequencing of the cloned inserts was used to determine species identity or closest relatives by comparison with known sequences in GenBank.

RESULTS

Sequences of Stenotrophomonas spp., including S. maltophilia (formerly Pseudomonas homology group V) were detected in six aneurysm samples. Propionibacterium acnes was identified in five samples, and Brevundimonas diminuta (formerly P. diminuta) in four samples. Other species previously assigned to the Pseudomonas genus such as Comamonas testosteroni, Delftia acidovorans, Burkholderia cepacia, Herbaspirillum sp., and Acidovorax sp. were also detected. Some clones fell into other environmental species, including Methylobacterium sp. and Bradyrhizobium elkanii, and others represented bacteria that have not yet been cultivated. DNA sequences from oral bacteria, including Streptococcus sanguinis, Tannerella forsythia, and Leptotrichia buccalis were detected. Sequences from Prevotella melaninogenica and Lactobacillus delbrueckii, which are commonly found in both mouth and gastrointestinal tract, were also detected. Additional species included Dermacoccus spp. and Corynebacterium vitaeruminis.

CONCLUSIONS

A wide variety of bacteria, including oral bacteria, was found to colonize aortic aneurysms and may play a role in their development. Several of these microorganisms have not yet been cultivated.

CLINICAL RELEVANCE

Although Chlamydophila pneumoniae has been detected in aneurysmal walls, its exact role in the condition remains inconclusive. Overall, there is scarce information about the role of microorganisms in aneurysmal disease. In the present study, we used molecular genetics to detect a diversity of bacteria in arterial walls of aortic aneurysms. The presence of multiple microorganisms in aneurysmal disease may have implications for chemoprophylaxis and antibiotic treatment if directed only at C.pneumoniae.

Severe infective endocarditis of native valves caused by Weissella confusa detected incidentally on echocardiography

Weissella confusa is gram-positive, catalase-negative, short rod or coccobacillus that has been isolated from a wide variety of habitats. We describe a rare, severe infective endocarditis of native valves caused by W. confusa that was detected incidentally on echocardiography. The patient recovered completely with valvular replacement plus antibiotic therapy.

Potential application of ribosomal intergenic spacer analysis to the microbial community analysis of agronomic products

Ribosomal intergenic spacer analysis (RISA) has been applied to the microbial community analysis of agronomic products in combination with a simple and rapid DNA extraction method, consisting of a one-step extraction and two-step purification, for a variety of agronomic products. RISA appears to be a useful tool for the study of the community structures of food-associated microbes and their use as a unique fingerprinting signature for each agronomic product. Sequencing analyses of amplicons generated from RISA suggest that this method can detect conventional microbes. In the case of RISA of wasabi paste DNA, the sequences of the amplicons showed high similarity to the plant pathogen Xanthomonas campestris and the soil bacterium Bacillus subtilis, whereas several food-associated bacteria (Lactococcus lactis, Lactococcus raffinolactis, and Lactococcus sakei) were detected using this technique in sausage DNA. Unexpectedly, the sequencing analyses also revealed the presence of several microbes that possessed high similarity to human bacterial pathogens such as Weissella confusa and Yersinia pestis. The results suggest that RISA will be a useful method for routine microbial community analysis in agronomic products.