Lactobacillus bacteremia, species identification, and antimicrobial susceptibility of 85 blood isolates

Significance of Gut Microbiota on Graves' Disease

Growing research proves gut microbiota and thyroid autoimmunity are linked. Graves' disease (GD), as an autoimmune thyroid disease (AITD), is attributed to the production of thyroid-stimulating hormone receptor (TSHR) autoantibodies that bind to the thyroid follicular endothelial cells. It is well known that genetic factors, environmental factors, and immune disorders count for much in the development of GD. So far, the pathogenesis of GD is not elucidated. Emerging research reveals that the change in gut microbiota composition and its metabolites are related to GD. The gut microbial diversity is reduced in GDs compared with healthy controls (HCs). Firmicutes and Bacteroidetes account for a large proportion at the genus level. It is found that phyla Bacteroidetes increased while phyla Firmicutes decreased in Graves' Disease patients (GD patients). Moreover, gut microbiota modulates the immune system to produce cytokines through bacterial metabolites. This article aims to find out the relation between gut microbiota dysbiosis and the development of GD. As more molecular pathways of bacterial metabolites are revealed, targeting microbiota is expected to the treatment of GD.

Lacticaseibacillus paracasei Bacteremia Associated With Probiotic Use in a Child With Hypoganglionosis: Case Report and Literature Review

Probiotics are generally considered safe and used to improve intestinal function. Here, we report a Lacticaseibacillus paracasei bacteremia case in an 8-month-old girl administered probiotics containing L. paracasei after jejunostomy for hypoganglionosis. The patient had persistent bacteremia with L. paracasei and was treated with antimicrobial therapy. The isolate from the blood culture was genetically indistinguishable to the strain contained in probiotics. Bacteremia risk should be considered before probiotic use in patients with underlying compromised immune systems or intestinal integrity.

Saccharomyces boulardii improves clinical and paraclinical indices in overweight/obese knee osteoarthritis patients: a randomized triple-blind placebo-controlled trial

PURPOSE

This study aimed to determine the effect of the probiotic Saccharomyces boulardii (S. boulardii) in patients with knee osteoarthritis (KOA).

METHODS

In this study, 70 patients with KOA were recruited via outpatient clinics between 2020 and 2021 and randomly assigned to receive probiotics or placebo supplements for 12 weeks. The primary outcome was a change in pain intensity according to the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain score.

RESULTS

Sixty-three patients completed the trial. A linear mixed analysis of covariance (ANCOVA) model analysis showed that probiotic was better than placebo in decreasing the pain intensity measured by visual analogue scale (VAS) [-2.11 (-2.59, -1.62) in probiotic group and -0.90 (-1.32, -0.48) in placebo group, p = 0.002] and WOMAC pain score [-3.57 (-4.66, -2.49) in probiotic group and -1.43 (-2.33, -0.53) in placebo group, p < 0.001]. The daily intake of acetaminophen for pain management significantly decreased in the probiotic group [-267.18 (-400.47, -133.89) mg, p < 0.001] that was significantly better than placebo (p = 0.006). Probiotic significantly decreased the serum levels of high-sensitivity C-reactive protein (hs-CRP) inflammatory index [-2.72 (-3.24, -2.20) µg/ml] and malondialdehyde (MDA) oxidative stress index [-1.61 (-2.11, -1.11) nmol/ml] compared to the placebo (p = 0.002 and p < 0.001, respectively). Probiotic was better than placebo in increasing the scores of role disorder due to physical health (p = 0.023), pain (p = 0.048) and physical health (p = 0.031).

CONCLUSION

Probiotic S. boulardii supplementation in patients with KOA significantly improved pain intensity, some dimensions of QoL, and inflammatory and oxidative stress biomarkers with no severe side effects.

TRIAL REGISTRY

Registered on the Iranian clinical trial website ( http://www.irct.ir : IRCT20161022030424N4) on 2019-09-02.

Investigating Safety and Technological Traits of a Leading Probiotic Species: Lacticaseibacillus paracasei

Lacticaseibacillus spp. are genetically close lactic acid bacteria species widely used in fermented products for their technological properties as well as their proven beneficial effects on human and animal health. This study, the first to include such a large collection of heterogeneous isolates (121) obtained from international collections belonging to Lacticaseibacillus paracasei, aimed to characterize the safety traits and technological properties of this important probiotic species, also making comparisons with other genetically related species, such as Lacticaseibacillus casei and Lacticaseibacillus zeae. These strains were isolated from a variety of heterogeneous sources, including dairy products, sourdoughs, wine, must, and human body excreta. After a preliminary molecular characterization using repetitive element palindromic PCR (Rep-PCR), Random Amplification of Polymorphic DNA (RAPD), and Sau-PCR, particular attention was paid to safety traits, evaluating antibiotic resistance profiles, biogenic amine (BA) production, the presence of genes related to the production of ethyl carbamate and diaminobenzidine (DAB), and multicopper oxidase activity (MCO). The technological characteristics of the strains, such as the capability to grow at different NaCl and ethanol concentrations and different pH values, were also investigated, as well as the production of bacteriocins. From the obtained results, it was observed that strains isolated from the same type of matrix often shared similar genetic characteristics. However, phenotypic traits were strain-specific. This underscored the vast potential of the different strains to be used for various purposes, from probiotics to bioprotective and starter cultures for food and feed production, highlighting the importance of conducting comprehensive evaluations to identify the most suitable strain for each purpose with the final aim of promoting human health.

Catheter-related bloodstream infection caused by Lacticaseibacillus paracasei: A case report and literature review

Catheter-related bloodstream infections (CRBSIs) caused by Lactobacillus spp. and Lacticaseibacillus spp. are rare, and their clinical course and optimal treatment remain uncertain. In this report, we present a 46-year-old male patient who experienced clinically diagnosed Lacticaseibacillus paracasei CRBSI on four separate occasions, despite receiving systemic administration of antibiotics and antimicrobial lock therapy. The patient did not develop L. paracasei bacteremia after catheter removal. This case report furthers our knowledge of CRBSI caused by Lactobacillus and related genera and highlights the need for further research.

Antimicrobial susceptibility testing of anaerobic bacteria causing bacteremia: A 13-year (2010-2022) retrospective study in a tertiary hospital

Infections from anaerobic microorganisms result from breached mucosal barriers, posing a significant mortality risk. A retrospective study at Hospital Universitario La Paz (Madrid) from 2010 to 2022 analyzed 491 (6.17 %) anaerobic bacteremia cases out of 7956 significant bacteremia cases among 171,833 blood culture requests. Bacteroides fragilis was the most frequently isolated species (28.3 %), followed by Clostridium perfringens (13.6 %). B. fragilis showed good susceptibility to amoxicillin/ clavulanic acid (86 %), piperacillin/tazobactam (86 %), and metronidazole (87.7 %). In general, non-fragilis Bacteroides species showed low susceptibility to penicillin (7 %), amoxicillin (17.5 %), and clindamycin (64.9 %). Of our 13 non-perfringens Clostridium isolates, four exhibited resistance to penicillin and four showed resistance to clindamycin. Lactobacillus species were highly susceptible to antibiotics tested. Prevotella spp. showed low susceptibility to penicillin (20 %), amoxicillin (20 %), and clindamycin (40 %). The study contributes valuable data for monitoring and improving anaerobic bacteremia treatment.

Bacteraemia caused by Lactobacillus casei in a patient after cardiac surgery. A case report

BACKGROUND

Bacteria of the Lactobacillus family are a part of the physiological flora of the oral cavity, gastrointestinal tract, and urinary tract. We have used them in the food industry as probiotics and supplements. In some settings, rod-shaped lactic acid bacteria may become pathogenic. It may occur in immunocompromised or heart disease patients after cardiac surgery, patients with disturbed intestinal wall permeability, or those treated with broad-spectrum antibiotics.

CASE PRESENTATION

We present rare bacteraemia induced by the probiotic bacterium Lactobacillus casei in a 63-year-old patient after the attempted removal of ICD electrodes, complicated by acute regurgitation of the tricuspid valve. The patient underwent urgent cardiac surgery, the electrode elements were removed, and the tricuspid valve was replaced with a biological prosthesis. After surgery, the patient required intensive, multidisciplinary treatment with mechanical ventilation, continuous renal replacement therapy, broad-spectrum empirical antibiotic therapy, parenteral nutrition, and blood product transfusion because of multiple organ failure. On the 14th day of hospitalisation, the clinical symptoms of septic shock were observed. The microbiological investigation was performed, and Lactobacillus casei was cultured from a dialysis catheter sample. Dedicated antimicrobials were administered, and the patient was discharged home in good overall condition.

CONCLUSIONS

The present case shows that the promoted use of probiotics must be cautiously administered to patients in severe conditions, especially when accompanied by reduced immune system efficiency symptoms.

The long and winding road of faecal microbiota transplants to targeted intervention for improvement of immune checkpoint inhibition therapy

INTRODUCTION

Immune checkpoint inhibition (ICI) therapy has revolutionized the treatment of cancer. Inhibitory molecules, either on the tumor or on cells of the immune system, are blocked, allowing the immune system of the patient to attack and eradicate the tumor. Not all patients respond to ICI therapy, and response or non-response has been associated with composition of gut microbiota.

AREA COVERED

Fecal microbiota transplantation (FMT) is used as adjunctive therapy in order to improve the outcome of ICI. ClinicalTrials.gov, and other databases were searched (October 2022) for studies dealing with gut microbiota modification and the outcome of ICI.

EXPERT OPINION

There is ample evidence for the beneficial effect of FMT on the outcome of ICI therapy for cancer, especially melanoma. Progress is being made in the unraveling of the mechanisms by which microbiota and their metabolites (butyrate and the tryptophan metabolite indole-3-aldehyde) interact with the mucosal immune system of the host. A better understanding of the mechanisms involved will allow the identification of key bacterial species which mediate the effect of FMT. Promising species are Faecalibacterium prausnitzii, Eubacterium rectale, Bifidobacterium adolescentis, B. bifidum, and B. longum, because they are important direct and indirect butyrate producers.

Lactobacillus Bacteremia and Probiotics: A Review

Lactobacilli are widely found in nature, are commensal microbes in humans, and are commonly used as probiotics. Concerns about probiotic safety have arisen due to reports of bacteremia and other Lactobacillus-associated infections. We reviewed the literature for articles on the pathogenicity of Lactobacillus spp. bacteremia and reports of probiotics in these patients. Our aim is to review these articles and update the present knowledge on the epidemiology of Lactobacillus spp. bacteremia and determine the role of probiotics in Lactobacillus bacteremia. Lactobacillus bacteremia is infrequent but has a higher risk of mortality and risk factors, including severe underlying diseases, immune system suppression, admission to intensive care units, and use of central venous catheters. A variety of Lactobacillus species may cause bacteremia and may or may not be associated with probiotic exposure. To determine if oral probiotics are the source of these infections, the blood isolates and the oral probiotic strain(s) must be compared by sensitive identification methods. The prevalence of Lactobacillus bacteremia is infrequent but is more common in patients taking probiotics compared to those not taking probiotics. Three probiotics (Lacticaseibacillus rhamnosus GG, Lactiplantibacillus plantarum, and Lacticaseibacillus paracasei) were directly linked with blood isolates from bacteremia patients using molecular identification assays.

A Case Report of Bacteremia Due to a Symptomatic and Rare Lactobacillus Rhamnosus Infected Splenic Hematoma and the Ultimate Treatment Model

We present the case of a 76-year-old male who presented to our hospital with a rare infection of Lactobacillus rhamnosus. The patient had a suspected urinary tract infection (UTI) secondary to a chronic indwelling catheter; however, when symptoms did not improve on standard therapy, blood cultures revealed the growth of L. rhamnosus. The patient was found via imaging to have a concurrent infectious splenic hematoma, and aspiration confirmed the presence of L. rhamnosus. The patient resided in an area nursing home and was a poor historian; however, it is conceivable that this infection was acquired via diet or from normal gut flora as the patient did not present on probiotic supplementation. In this case report, we present both pharmaceutical and interventional treatment strategies as well as a timeline of treatment for this rarely-seen infection.

The metabolites of lactic acid bacteria: classification, biosynthesis and modulation of gut microbiota

Lactic acid bacteria (LAB) are ubiquitous microorganisms that can colonize the intestine and participate in the physiological metabolism of the host. LAB can produce a variety of metabolites, including organic acids, bacteriocin, amino acids, exopolysaccharides and vitamins. These metabolites are the basis of LAB function and have a profound impact on host health. The intestine is colonized by a large number of gut microorganisms with high species diversity. Metabolites of LAB can keep the balance and stability of gut microbiota through aiding in the maintenance of the intestinal epithelial barrier, resisting to pathogens and regulating immune responses, which further influence the nutrition, metabolism and behavior of the host. In this review, we summarize the metabolites of LAB and their influence on the intestine. We also discuss the underlying regulatory mechanisms and emphasize the link between LAB and the human gut from the perspective of health promotion.

Gut microbiota and myocardial fibrosis

Myocardial fibrosis (MF) is a pathophysiological condition that accompanies various myocardial diseases and comprises a damaged myocardial matrix repair process. Although fibrosis plays a vital role in repair, it ultimately alters cardiac systolic and diastolic functions. The gut microbiota is a complex and dynamic ecosystem with billions of microorganisms that produce bioactive compounds that influence host health and disease progression. Intestinal microbiota has been shown to correlate with cardiovascular disease, and dysbiosis of the intestinal microbiota is involved in the development of MF. In this review, we discuss the role of intestinal microbiota in the process of MF, including alterations in microbiota composition and the effects of metabolites. We also discuss how diet and medicines can affect cardiac fibrosis by influencing the gut microbiota, and potential future therapies targeting the gut-heart axis. A healthy gut microbiota can prevent disease, but dysbiosis can lead to various symptoms, including the induction of heart disease. In this review, we discuss the relevance of the gut-heart axis and the multiple pathways by which gut microbiota may affect cardiac fibrosis, including inflammatory factors, immune cells, and gut microbiota metabolites, such as trimethylamine-N-oxide (TMAO) and short-chain fatty acids (SCFAs). Finally, we discuss the involvement of gut microbiota in the treatment of cardiac fibrosis, including drugs, fecal microbiota transplantation, and oral probiotics or prebiotics. With future studies on the relationship between the heart and gut microbiota, we hope to find better ways to improve MF through the gut-heart axis.

Meropenem resistant Lactobacillus endocarditis in an immunocompetent patient

Lactobacilli are gram-positive bacteria usually found in the normal flora and are commonly used as probiotic treatments for vaginal candidiasis. Lactobacilli are normally considered non-pathogenic; however, certain risk factors can make a patient susceptible to severe infections. This case describes an immunocompetent 61-year-old female with an automated intracardiac defibrillator who presented with a 10-day history of nausea and vomiting. Furthermore, diagnostic tests, including a transesophageal echocardiography, revealed a large vegetation, and blood cultures were consistently positive for Lactobacillus. The patient was treated with intravenous penicillin and gentamicin, along with removal of the automated intracardiac defibrillator. In patients with significant underlying conditions, physicians should consider Lactobacillus as a causative organism to avoid delays in treatment.

Could paraprobiotics be a safer alternative to probiotics for managing cancer chemotherapy-induced gastrointestinal toxicities?

Clinical oncology has shown outstanding progress improving patient survival due to the incorporation of new drugs. However, treatment success may be reduced by the emergency of dose-limiting side effects, such as intestinal mucositis and diarrhea. Mucositis and diarrhea management is symptomatic, and there is no preventive therapy. Bacterial and fungal-based compounds have been suggested as an alternative for preventing the development of diarrhea in cancer patients. Using probiotics is safe and effective in immunocompetent individuals, but concerns remain during immunosuppressive conditions. Paraprobiotics, formulations composed of non-viable microorganisms, have been proposed to overcome such limitation. The present literature review discusses current evidence regarding the possible use of paraprobiotics as an alternative to probiotics to prevent gastrointestinal toxicity of cancer chemotherapy.

Antimicrobial activity of dominant Ligilactobacillus animalis strains in healthy canine feces and their probiotic potential

The number of companion animals living with humans has continually increased over the last few decades, and so has the interest of owners and stakeholders in the animal food and probiotics industry. Currently, the probiotic bacteria added to the feed of companion animals predominantly originate from the lactic acid bacteria (LAB) used for humans; however, there are differences between the microbiota of humans and that of their companion animals. This study aimed to determine the dominant LAB in dog feces and investigate their functional properties. Ligilactobacillus animalis (formerly called Lactobacillus animalis) was identified as the dominant lactic acid bacterium in dog feces. It displayed various inhibitory effects against pathogenic and enteropathogenic bacteria. This finding suggests that Ligilactobacillus animalis can potentially be used in novel probiotics or as a food additive for dogs.

Comparison between frail and non-frail older adults' gut microbiota: A systematic review and meta-analysis

BACKGROUND

Emerging evidence suggests that the intestinal microbiota (IM) undergoes remodelling as we age, and this impacts the ageing trajectory and mortality in older adults. The aim was to investigate IM diversity differences between frail and non-frail older adults by meta-analysing previous studies.

METHODS

The protocol of this systematic review with meta-analysis was registered on PROSPERO (CRD42021276733). We searched for studies comparing IM diversity of frail and non-frail older adults indexed on PubMed, Embase, Cochrane, and Web of Science in November 2021.

RESULTS

We included 11 studies with 1239 participants, of which 340 were meta-analysed. Frailty was defined by a variety of criteria (i.e. Fried Scale, European Consensus on Sarcopenia). There were no differences in the meta-analyses between the frail and non-frail groups for species richness index (SMD = -0.147; 95% CI = -0.394, 0.100; p = 0.243) and species diversity index (SMD = -0.033; 95% CI = -0.315, 0.250; p = 0.820). However, we identified almost 50 differences between frail and non-frail within the relative abundance of bacteria phyla, families, genera, and species in the primary studies.

CONCLUSIONS

The evidence to prove that there are differences between frail and non-frail IM diversity by meta-analysis is still lacking. The present results suggest that further investigation into the role of specific bacteria, their function, and their influence on the physiopathology of frailty is needed.

Safety Evaluation by Phenotypic and Genomic Characterization of Four Lactobacilli Strains with Probiotic Properties

Probiotic Lactobacillus species are known to exert health benefits in hosts when administered in adequate quantities. A systematic safety assessment of the strains must be performed before the Lactobacillus strains can be designated as probiotics for human consumption. In this study, we selected Lactobacillus fermentum IDCC 3901, L. gasseri IDCC 3101, L. helveticus IDCC 3801, and L. salivarius IDCC 3551 as representative Lactobacilli probiotic strains and investigated their probiotic properties and potential risks through phenotypic and genomic characterization. Various assays including antimicrobial resistance, biogenic amine production, L-/D-lactate production, acute oral toxicity, and antipathogenic effect were performed to evaluate the safety of the four Lactobacillus strains. Genomic analysis using whole genome sequencing was performed to investigate virulence and antibiotic resistance genes in the genomes of the selected probiotic strains. The phenotypes of the strains such as enzymatic activity and carbohydrate utilization were also investigated. As a result, antibiotic resistances of the four Lactobacillus species were detected; however, neither antibiotic resistance-related genes nor virulence genes were found by genomic analysis. Moreover, the four Lactobacillus species did not exhibit hemolytic activity or β-glucuronidase activity. The biogenic amine production and oral acute toxicity were not shown in the four Lactobacillus species, whereas they produced D-lactate with minor ratio. The four Lactobacillus species exhibited antipathogenic effect to five pathogenic microorganisms. This study provides a way to assess the potential risks of four different Lactobacillus species and validates the safety of all four strains as probiotics for human consumption.

Alarming Antibiotic Resistance of Lactobacilli Isolated from Probiotic Preparations and Dietary Supplements

In this study, we screened eight commercially available brands of Lactobacillus-containing probiotic preparations and dietary supplements for resistance towards commonly administered antibiotics of different classes. According to disc diffusion results, most of the isolates were resistant to vancomycin and susceptible to penicillin-type antibiotics (ampicillin and amoxicillin), carbapenems (imipenem, meropenem, and ertapenem), and inhibitors of protein synthesis (chloramphenicol, erythromycin, tetracycline, clarithromycin, and linezolid). However, based on minimum inhibitory concentration (MIC) values, six strains were reconsidered as resistant to tetracycline. All tested lactobacilli were resistant towards amikacin, ciprofloxacin, and norfloxacin. Resistance to cephalosporins was highly variable and decreased in the following order: ceftazidime/cefepime, ceftriaxone, cefotaxime, cefazolin, and cefoperazone. PCR screening for antibiotic resistance determinants in probiotic lactobacilli revealed a wide occurrence of vancomycin resistance gene vanX, ciprofloxacin resistance gene parC, and extended-spectrum β-lactamase gene blaTEM. We also detected the tetK gene for tetracycline resistance in one isolate. Additionally, we identified discrepancies between the claims of the manufacturers and the identified species composition, as well as the enumerated amount of viable bacteria, for several products. The results of this study raise concerns about the safety of lactobacilli for human consumption as probiotics, as they may act as reservoirs of transferable antibiotic resistance genes.

Safety assessment of the indigenous probiotic strain Lactiplantibacillus plantarum subsp. plantarum Kita-3 using Sprague-Dawley rats as a model

Lactiplantibacillus plantarum subsp. plantarum Kita-3 is a candidate probiotic from Halloumi cheese produced by Mazaraat Artisan Cheese, Yogyakarta, Indonesia. This study evaluated the safety of consuming a high dose of L. plantarum subsp. plantarum Kita-3 in Sprague-Dawley rats for 28 days. Eighteen male rats were randomly divided into three groups, such as the control group, the skim milk group, and the probiotic group. Feed intake and body weight were monitored, and blood samples, organs (kidneys, spleen, and liver), and the colon were dissected. Organ weight, hematological parameters, serum glutamic oxaloacetic transaminase (SGOT), and serum glutamic pyruvic transaminase (SGPT) concentrations, as well as intestinal morphology of the rats, were measured. Microbial analyses were carried out on the digesta, feces, blood, organs, and colon. The results showed that consumption of L. plantarum did not negatively affect general health, organ weight, hematological parameters, SGOT and SGPT activities, or intestinal morphology. The number of L. plantarum in the feces of rats increased significantly, indicating survival of the bacterium in the gastrointestinal tract. The bacteria in the blood, organs, and colon of all groups were identified using repetitive-polymerase chain reaction with the BOXA1R primers and further by 16S rRNA gene sequencing analysis, which revealed that they were not identical to L. plantarum subsp. plantarum Kita-3. Thus, this strain did not translocate to the blood or organs of rats. Therefore, L. plantarum subsp. plantarum Kita-3 is likely to be safe for human consumption.

New Potentially Probiotic Strains Isolated from Humans – Comparison of Properties with Strains from Probiotic Products and ATCC Collection

Lactic acid bacteria are used in various types of probiotic products. Due to the constantly growing probiotics market, new strains with pro-health properties are sought. The present study compared 39 strains of Lactobacillus, Lacticaseibacillus, and Lactiplantibacillus, isolated from probiotic products and healthy people. The current research aimed to search for new, potentially probiotic strains. For this purpose the relationship between Lactobacillaceae strains was carried out; moreover, the basic properties of probiotic microorganisms, such as survival at low pH and bile salt environment, antibiotic susceptibility, aggregation and antagonism were estimated. The properties of these isolates were also compared with the properties of probiotic strains from the ATCC collection. In comparing the genetic relationship (PFGE method) between the tested isolates, it was observed that some of them show a high degree of similarity. All tested strains tolerated an environment with a pH value of 3.0, and the addition of 0.3% bile salt; showed auto-aggregation properties and displayed antagonism against pathogenic microorganisms. In the present study, the bacteria were susceptible to tetracycline, chloramphenicol and ampicillin; the resistance to vancomycin

depended on the bacteria type. All the properties were strain-depended. Most of the tested strains had properties comparable to the reference strains. Three L. acidophilus strains isolated from cervical swabs seem to be promising candidates for probiotic strains.

Bacteraemia Caused by Probiotic Strains of Lacticaseibacillus rhamnosus—Case Studies Highlighting the Need for Careful Thought before Using Microbes for Health Benefits

Lactic acid bacteria belonging to Lactobacillus spp. and Lacticaseibacillus spp. are a natural part of fermented milk and other food products, probiotic supplements and human microbiota. They mainly belong to mucosal microflora, especially oral, vaginal and intestinal. Lacticaseibacillus spp. strains included in probiotics are generally characterised as safe microorganisms, and the species are concerned bacteria with very low pathogenic potential. However, infections caused by Lactobacillus spp. and Lacticaseibacillus spp., including bacteraemia and endocarditis, occur occasionally. The aim of the study was to present two cases of bacteraemia due to Lacticaseibacillus rhamnosus associated with the use of a probiotic product. It afflicted patients in intensive care units. The investigation was preliminarily based on clinical and microbiological recognition of the cases. The initial observation was laboratory confirmed with the application of pulsed-field gel electrophoresis (PFGE) results. Identical PFGE patterns were obtained for the evaluated strains and the strains derived from a commercially available probiotic that was administered to those patients. The increasing number of studies describing opportunistic infections due to probiotic strains of Lacticaseibacillus spp. should result in verifying the safety of probiotic formulations used in immunocompromised patients and forming detailed guidelines for the use of probiotics among patients from several risk groups.

Infection prevention requirements for the medical care of immunosuppressed patients: recommendations of the Commission for Hospital Hygiene and Infection Prevention (KRINKO) at the Robert Koch Institute

In Germany, guidelines for hygiene in hospitals are given in form of recommendations by the Commission for Hospital Hygiene and Infection Prevention (Kommission für Krankenhaushygiene und Infektionsprävention, "KRINKO"). The KRINKO and its voluntary work are legitimized by the mandate according to § 23 of the Infection Protection Act (Infektionsschutzgesetz, "IfSG"). The original German version of this document was published in February 2021 and has now been made available to the international professional public in English. The guideline provides recommendations on infection prevention and control for immunocompromised individuals in health care facilities. This recommendation addresses not only measures related to direct medical care of immunocompromised patients, but also management aspects such as surveillance, screening, antibiotic stewardship, and technical/structural aspects such as patient rooms, air quality, and special measures during renovations.

Novel microaerobic agar plate method delivers highly selective and accurate enumeration of probiotic lactobacilli in freeze-dried blends containing bifidobacteria

The enumeration of viable bacteria is an essential metric in the dietary supplement and food industry to ensure quality of probiotic products. However, selective enumeration of lactobacilli in probiotic freeze-dried blends containing bifidobacteria is difficult to achieve with current Lactobacillus-specific agars (i.e., Rogosa and LAMVAB). Using a panel of Bifidobacterium and Lactobacillus commercial probiotic species, we found that Rogosa agar failed to inhibit all bifidobacteria while LAMVAB agar suppressed several lactobacilli. This prompted us to develop an alternative method of selection, hereby referred to as Lactobacillus Micro-Aerobic (LMA) method, which promotes growth under controlled microaerobic conditions (6-12% O₂, 5-8% CO₂) to leverage the different oxygen sensitivities of lactobacilli and bifidobacteria. Validation using pure cultures and multi-strain blends of 4 Bifidobacterium and 10 Lactobacillus species showed that LMA effectively suppressed all bifidobacteria and accurately enumerated all lactobacilli when compared to control methods. These results demonstrate the superior efficacy of modulating the redox environment to select for Lactobacillus within a Bifidobacterium-rich background, as opposed to applying acid and antibiotic pressures.

A Comparative Genomic and Safety Assessment of Six Lactiplantibacillus plantarum subsp. argentoratensis Strains Isolated from Spontaneously Fermented Greek Wheat Sourdoughs for Potential Biotechnological Application

The comparative genome analysis of six Lactiplantibacillus plantarum subsp. argentoratensis strains previously isolated from spontaneously fermented Greek wheat sourdoughs is presented. Genomic attributes related to food safety have been studied according to the European Food Safety Authority (EFSA) suggestions for the use of lactic acid bacteria (LAB) in the production of foods. Bioinformatic analysis revealed a complete set of genes for maltose, sucrose, glucose, and fructose fermentation; conversion of fructose to mannitol; folate and riboflavin biosynthesis; acetoin production; conversion of citrate to oxaloacetate; and the ability to produce antimicrobial compounds (plantaricins). Pathogenic factors were absent but some antibiotic resistance genes were detected. CRISPR and cas genes were present as well as various mobile genetic elements (MGEs) such as plasmids, prophages, and insertion sequences. The production of biogenic amines by these strains was not possible due to the absence of key genes in their genome except lysine decarboxylase associated with cadaverine; however, potential degradation of these substances was identified due to the presence of a blue copper oxidase precursor and a multicopper oxidase protein family. Finally, comparative genomics and pan-genome analysis showed genetic differences between the strains (e.g., variable pln locus), and it facilitated the identification of various phenotypic and probiotic-related properties.

Mortality risk and antibiotic use for COVID-19 in hospitalized patients over 80

INTRODUCTION

Patients over 80 years of age are more prone to develop severe symptoms and die from COVID-19. Antibiotics were massively prescribed in the first days of the pandemic without evidence of super infection. Antibiotics may increase the risk of mortality in cases of viral pneumonia. With age and antibiotic use, the microbiota becomes altered and less protective effect against lethal viral pneumonia. Thus we assessed whether it is safe to prescribe antibiotics for COVID-19 pneumonia to patients over 80 years of age.

METHOD

We conducted a retrospective monocentric study in a 1240-bed university hospital. Our inclusion criteria were patients aged ≥ 80 years, hospitalized in a COVID-19 unit, with either a positive SARS-CoV-2 RT-PCR from a nasopharyngeal swab or a CT scan within 72 h after or prior to hospitalization in the unit suggestive of infection.

RESULTS

We included 101 patients who received antibiotics and 48 who did not. The demographics in the two groups were similar. Overall mortality was higher for the group that received antibiotics than for the other group (36.6% vs 14.6%,). According to univariate COX analysis, the risk of mortality was higher (HR = 1.98 [0.926; 4.23]) but non-significantly for the antibiotic group. In multivariate analysis, independent risk factors of mortality were an increased leukocyte count and decreased oxygen saturation (HR = 1.097 [1.022; 1.178] and HR = 0.927 [0.891; 0.964], respectively).

CONCLUSION

This study raises questions about the interest of antibiotic therapy, its efficacy, and its effect on COVID-19 and encourages further research.

A genomic data resource for predicting antimicrobial resistance from laboratory-derived antimicrobial susceptibility phenotypes

Antimicrobial resistance (AMR) is a major global health threat that affects millions of people each year. Funding agencies worldwide and the global research community have expended considerable capital and effort tracking the evolution and spread of AMR by isolating and sequencing bacterial strains and performing antimicrobial susceptibility testing (AST). For the last several years, we have been capturing these efforts by curating data from the literature and data resources and building a set of assembled bacterial genome sequences that are paired with laboratory-derived AST data. This collection currently contains AST data for over 67 000 genomes encompassing approximately 40 genera and over 100 species. In this paper, we describe the characteristics of this collection, highlighting areas where sampling is comparatively deep or shallow, and showing areas where attention is needed from the research community to improve sampling and tracking efforts. In addition to using the data to track the evolution and spread of AMR, it also serves as a useful starting point for building machine learning models for predicting AMR phenotypes. We demonstrate this by describing two machine learning models that are built from the entire dataset to show where the predictive power is comparatively high or low. This AMR metadata collection is freely available and maintained on the Bacterial and Viral Bioinformatics Center (BV-BRC) FTP site ftp://ftp.bvbrc.org/RELEASE_NOTES/PATRIC_genomes_AMR.txt.

Limosilactobacillus caccae sp. nov., a new bacterial species isolated from the human gut microbiota

Strain Marseille-P3519T isolated from the fecal flora of a 25-year-old healthy French woman was a Gram-positive anaerobic bacterium, non-motile and non-spore forming. The 16S rRNA gene sequence of Marseille-P3519 showed 97.73% of sequence similarity with Limosilactobacillus reuteri DSM 20016, the closest species, phylogenetically. Furthermore, the average nucleotide identity of strain Marseille-3519 with its closest related species was 75.8% that was very below the recommended threshold (>95-96%). Its genome had 2 237 367 bp with 45.42 mol% of G + C content. Major fatty acids were C16:0 (50.8%), C18:1n9 (18.0%), C18:2n6 (9.8%) and C19:1n9 (8.9%). It was catalase negative and fermented glycerol, glucose, fructose, D-maltose, lactose and mannose. These findings support that strain Marseille-P3519 ( = CSURP3519 = CECT 30110) is a new member of the genus Limosilactobacillus for which the name Limosilactobacillus caccae sp. nov., is proposed.

What Is Wrong with Enterococcal Probiotics?

Enterococci, being the common part of indigenous human microbiota and present in numerous fermented food products and probiotics, are often positioned as health-threatening bacterial pathogens. This makes medical community, especially part of it which is not involved in microbiology research, in an uncertainty regarding the legitimacy of using enterococcal probiotics in medical practice or even consuming them in foods such as cheese or salami. However, the difference between the clinical strains and strains used as probiotics is more than significant. The present paper tries to shed light on enterococci based on the contemporary knowledge of molecular microbiology.

Application of probiotics in candidiasis management

Candidiasis (e.g., oral, gastrointestinal, vaginal, urinary tract, systemic) is a worldwide growing problem, since antifungal resistance and immunosuppression states are rising. To address this problem, very few drugs are available for the treatment of Candida spp. infections. Therefore, novel therapeutic strategies are urgently required. Probiotics have been proposed for the prevention and treatment of bacterial infections due to their safety record and efficacy, however, little is still known about their potential role regarding fungal infections. The purpose of this review is to present an updated summary of the evidence of the antifungal effects of probiotics along with a discussion of their potential use as an alternative/complementary therapy against Candida spp. infections. Thus, we performed a literature search using appropriate keywords ("Probiotic + Candida", "Candidiasis treatment", and "Probiotic + candidiasis") to retrieve relevant studies (both preclinical and clinical) with special emphasis on the works published in the last 5 years. An increasing amount of evidence has shown the potential usefulness of probiotics in the management of oral and vulvovaginal candidiasis in recent years. Among other results, we found that, as for bacterial infections, Lactobacillus, Bifidobacterium, and Saccharomyces are the most studied and effective genus for this purpose. However, in other areas, particularly in skincandidiaisis, studies are low or lacking. Thus, further investigation is necessary including in vitro and in vivo studies to establish the usefulness of probiotics in the management of candidiasis.

Severe deep neck space infection caused by Eggerthia catenaformis

A 64-year-old woman was acutely referred to the Department of Otorhinolaryngology, Head and Neck Surgery, Aalborg University Hospital due to rapidly progressing neck swelling, fever and dysphagia. Clinical examination revealed submental swelling, trismus and laryngeal inflammation. A contrast-enhanced CT scan showed infection in the deep neck spaces with multiple abscesses. The patient underwent acute surgery and antimicrobial therapy was initiated and she was transferred to an intensive care unit. Three additional surgical procedures were needed before sufficient drainage was achieved. There was growth of different oral commensals from four separate pus aspirates, while Eggerthia catenaformis was cultured in all samples. Due to the extent of the infection, the patient stayed in the intensive care unit for 16 days, but recovered completely due to adequate surgery and antimicrobial therapy for 4 weeks. Here we present the third reported case of a severe deep neck space infection with multiple abscesses due to E. catenaformis.

Lactobacillus-Associated Spontaneous Bacterial Peritonitis in a Liver Cirrhosis Patient on Probiotics

The efficacy of over the counter probiotics has been an area of scientific debate. While the benefits of probiotics are heavily disputed, probiotics are considered generally safe. We present a case of a liver cirrhosis patient, who presented with hepatic encephalopathy. The patient was taking daily probiotics and receiving weekly therapeutic paracentesis. His workup revealed spontaneous bacterial peritonitis (SBP). Despite starting the patient on empiric ceftriaxone and vancomycin, the patient's leukocytosis did not improve. The paracentesis fluid and blood cultures grew Lactobacillus gasseri. Antibiotics were switched to piperacillin/tazobactam, after which the patient improved clinically. The case highlights the importance of vigilance in using probiotics, especially in liver cirrhosis patients. Also, patients with Lactobacillus-associated SBP may not improve with empiric antibiotic treatment of cephalosporins.

Fatal Lactobacillus endocarditis in a patient with transcatheter aortic valve replacement

Lactobacillus species may translocate from the gastrointestinal tract into systemic circulation from ingested probiotics or commensal flora. Their pathogenic potential is still debated. Lactobacillus endocarditis is a rare entity with only around 120 cases reported in the literature. Here, we report the first case of fatal Lactobacillus endocarditis with involvement of a transcatheter aortic valve replacement with the following goals: to reaffirm the pathological significance of Lactobacillus spp, to demonstrate the potential limitations of the modified Duke criteria in diagnosing infective endocarditis of transcatheter aortic valve replacement, and to urge clinicians to aggressively search for and consider empiric treatment for endocarditis in patients with prosthetic valves who develop Lactobacillus bacteraemia.

Update of Probiotics in Human World: A Nonstop Source of Benefactions till the End of Time

Lactic acid bacteria (LAB) are known for their biotechnological potential. Moreover, LAB are distinguished by amazing criteria: Adjusting the intestinal environment, inhibiting pathogenic microbes in the gastrointestinal tract, ability to reduce pathogen adhesion activity, improving the balance of the microbiota inside the intestine, capabilities of regulating intestinal mucosal immunity, and maintaining intestinal barrier function. The escalating number of research and studies about beneficial microorganisms and their impact on promoting health has attracted a big interest in the last decades. Since antiquity, various based fermented products of different kinds have been utilized as potential probiotic products. Nevertheless, the current upsurge in consumers' interest in bioalternatives has opened new horizons for the probiotic field in terms of research and development. The present review aims at shedding light on the world of probiotics, a continuous story of astonishing success in various fields, in particular, the biomedical sector and pharmaceutical industry, as well as to display the importance of probiotics and their therapeutic potential in purpose to compete for sturdy pathogens and to struggle against diseases and acute infections. Shadows and future trends of probiotics use are also discussed.

Fecal Microbiome Alteration May Be a Potential Marker for Gastric Cancer

Although intestinal microbial dysbiosis was confirmed to be associated with many chronic diseases and health status through complicated interaction with the host, the effect on gastric cancer was less studied. In this study, we sequenced the 16S rRNA and 18S rRNA genes of fecal bacteria and fungi, respectively, in 134 gastric cancer patients and 58 healthy controls matched by age and gender. Propensity score matching (PSM) was adopted for adjusting diet habits and lifestyle, and 44 patients and 44 healthy controls (matching population) were enrolled. Serum antibody to H. pylori and metabolites of the matching population were detected. The positive rates of antibody to H. pylori between the patients and the control group did not reach the statistical difference. LEfSe analysis indicated that bacteria were more stable than fungi when adjusting diet and lifestyle. Veillonella, Megasphaera, and Prevotella 7 genus and Streptococcus salivarius subsp. Salivarius, Bifidobacterium dentium, and Lactobacillus salivarius species in bacteria were related to the risk of gastric cancer and showed a good diagnostic value in distinguishing the patients from healthy controls. Streptococcus mitis showed a risk effect for gastric cancer; however, the effect turned into be protective after PSM. Serum L-alanine, L-threonine, and methionol were positively associated with Veillonella and Streptococcus and several fungi genus. Overall, our findings indicated that fecal microbiome constitution alteration may be associated with gastric cancer through influencing the amino acid metabolism.

The Clinical Microbiology Laboratory and the Opioid Epidemic: Challenges and Opportunities

Increased infections from injection drug use harm patients and are costly to the health care system. The impact on clinical microbiology laboratories is less recognized. Microbiology laboratories face increased test volume and test complexity from the spectrum and burden of pathogens associated with injection drug use, which lead to diagnostic challenges and overtaxed resources. We describe stressed workflows, pathogens that defy protocols, and limits of current technologies. Laboratories may benefit from protocol revisions, additional resources, workflow oversight, and improved communication with clinical providers to optimally meet challenges associated with this public health crisis.

The Postbiotic Activity of Lactobacillus paracasei 28.4 Against Candida auris

Candida auris has emerged as a medically important pathogen with considerable resistance to antifungal agents. The ability to produce biofilms is an important pathogenicity feature of this species that aids escape of host immune responses and antimicrobial agents. The objective of this study was to verify antifungal action using in vitro and in vivo models of the Lactobacillus paracasei 28.4 probiotic cells and postbiotic activity of crude extract (LPCE) and fraction 1 (LPF1), derived from L. paracasei 28.4 supernatant. Both live cells and cells free supernatant of L. paracasei 28.4 inhibited C. auris suggesting probiotic and postbiotic effects. The minimum inhibitory concentration (MIC) for LPCE was 15 mg/mL and ranges from 3.75 to 7.5 mg/mL for LPF1. Killing kinetics determined that after 24 h treatment with LPCE or LPF1 there was a complete reduction of viable C. auris cells compared to fluconazole, which decreased the initial inoculum by 1-logCFU during the same time period. LPCE and LPF1 significantly reduced the biomass (p = 0.0001) and the metabolic activity (p = 0.0001) of C. auris biofilm. There was also a total reduction (~10⁸ CFU/mL) in viability of persister C. auris cells after treatment with postbiotic elements (p < 0.0001). In an in vivo study, injection of LPCE and LPF1 into G. mellonella larvae infected with C. auris prolonged survival of these insects compared to a control group (p < 0.05) and elicited immune responses by increasing the number of circulating hemocytes and gene expression of antimicrobial peptide galiomicin. We concluded that the L. paracasei 28.4 cells and postbiotic elements (LPCE and LPF1) have antifungal activity against planktonic cells, biofilms, and persister cells of C. auris. Postbiotic supplementation derived from L. paracasei 28.4 protected G. mellonella infected with C. auris and enhanced its immune status indicating a dual function in modulating a host immune response.

Safety Assessment of a Nham Starter Culture Lactobacillus plantarum BCC9546 via Whole-genome Analysis

The safety of microbial cultures utilized for consumption is vital for public health and should be thoroughly assessed. Although general aspects on the safety assessment of microbial cultures have been suggested, no methodological detail nor procedural guideline have been published. Herein, we propose a detailed protocol on microbial strain safety assessment via whole-genome sequence analysis. A starter culture employed in traditional fermented pork production, nham, namely Lactobacillus plantarum BCC9546, was used as an example. The strain’s whole-genome was sequenced through several next-generation sequencing techniques. Incomplete plasmid information from the PacBio sequencing platform and shorter chromosome size from the hybrid Oxford Nanopore-Illumina platform were noted. The methods for 1) unambiguous species identification using 16S rRNA gene and average nucleotide identity, 2) determination of virulence factors and undesirable genes, 3) determination of antimicrobial resistance properties and their possibility of transfer, and 4) determination of antimicrobial drug production capability of the strain were provided in detail. Applicability of the search tools and limitations of databases were discussed. Finally, a procedural guideline for the safety assessment of microbial strains via whole-genome analysis was proposed.

Saccharomyces boulardii: What Makes It Tick as Successful Probiotic?

Saccharomyces boulardii is a probiotic yeast often used for the treatment of GI tract disorders such as diarrhea symptoms. It is genetically close to the model yeast Saccharomyces cerevisiae and its classification as a distinct species or a S. cerevisiae variant has long been discussed. Here, we review the main genetic divergencies between S. boulardii and S. cerevisiae as a strategy to uncover the ability to adapt to the host physiological conditions by the probiotic. S. boulardii does possess discernible phenotypic traits and physiological properties that underlie its success as probiotic, such as optimal growth temperature, resistance to the gastric environment and viability at low pH. Its probiotic activity has been elucidated as a conjunction of multiple pathways, ranging from improvement of gut barrier function, pathogen competitive exclusion, production of antimicrobial peptides, immune modulation, and trophic effects. This review summarizes the participation of S. boulardii in these mechanisms and the multifactorial nature by which this yeast modulates the host microbiome and intestinal function.

Renal and perinephric abscesses involving Lactobacillus jensenii and Prevotella bivia in a young woman following ureteral stent procedure

 is a gram-positive bacillus in the female genital tract believed to be a commensal organism that inhibits the growth of more virulent pathogens. Prevotella bivia is a gram-negative bacillus species also typically commensal in the female genital tract. Lactobacillus as the primary causative agent in perinephric abscesses and bacteremia has been documented, albeit very uncommon and opportunistic. Prevotella bivia is not classically associated with perinephric abscesses but has been implicated in rare cases of pelvic inflammatory disease and tubo-ovarian abscesses. In this report, we present a 26-year-old immunocompetent woman with a recent history of nephrolithiasis treated with lithotripsy, ureteral stent placement and removal, and antibiotics who was admitted for fever and severe right flank pain. Imaging showed a right-sided renal and perinephric abscesses colonized by Lactobacillus jensenii and Prevotella bivia. Blood cultures were also positive for Lactobacillus species. Per literature review, intravenous ceftriaxone and metronidazole were administered with successful resolution of abscesses and negative repeat blood cultures. To our knowledge, this is the first case of simultaneous renal system abscesses caused by Lactobacillus and Prevotella species. Nephrolithiasis and prior antibiotics likely contributed to the opportunistic pathogenesis in this otherwise immunocompetent patient.

Antibiotic Resistance of LACTOBACILLUS Strains

The study provides phenotypic and molecular analyses of the antibiotic resistance in 20 Lactobacillus strains including 11 strains newly isolated from fermented plant material. According to the results of disc diffusion method, 90% of tested lactobacilli demonstrated sensitivity to clindamycin and 95% of strains were susceptible to tetracycline, erythromycin, and rifampicin. Ampicillin and chloramphenicol were found to inhibit all bacteria used in this study. The vast majority of tested strains revealed phenotypic resistance to vancomycin, ciprofloxacin, and aminoglycosides. Most of Lactobacillus strains showed high minimum inhibitory concentrations (MICs) of cefotaxime, ceftriaxone, and cefazolin and therefore were considered resistant to cephalosporins. All the strains exhibited multidrug resistance. The occurrence of resistance genes was associated with phenotypic resistance, with the exception of phenotypically susceptible strains that contained genes for tetracycline (tetK, tetL) and erythromycin (ermB, mefA) resistance. The vanX gene for vancomycin resistance was among the most frequently identified among the lactobacilli (75% of strains), but the occurrence of the parC gene for ciprofloxacin resistance was sporadic (20% of strains). Our results mainly evidence the intrinsic nature of the resistance to aminoglycosides in lactobacilli, though genes for enzymatic modification of streptomycin aadA and aadE were found in 20% of tested strains. The occurrence of extended spectrum beta-lactamases (ESBL) was unknown in Lactobacillus, but our results revealed the blaTEM gene in 80% of strains, whereas blaSHV and blaOXA-1 genes were less frequent (20% and 15% of strains, respectively).

Presence of OXA-48 Gene in a Clinical Isolate of Lactobacillus rhamnosus

Lactobacilli are part of the microbiota and are also used as probiotics. However, in recent years they have been associated with invasive infections, especially bacteremia. Lactobacillus spp. are usually susceptible to penicillins, macrolides, and carbapenems, but Lactobacillus rhamnosus is intrinsically resistant to glycopeptides. The aim of this study was to determine the antimicrobial susceptibility profile and resistance mechanism of a clinical isolate of L. rhamnosus isolated from 10 sets of blood cultures of the same patient. The isolate was identified by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry (Bruker Daltonics; BD, Bremen, Germany) and 16S rRNA gene sequencing. In vitro susceptibilities to penicillin, ampicillin, imipenem, vancomycin, erythromycin, clindamycin, and linezolid were determined with gradient test strips (bioMérieux, France) on Mueller-Hinton agar plates supplemented with 5% defibrinated horse blood and 20 mg/L β-NAD. The isolate was resistant to vancomycin and imipenem. Polymerase chain reaction test was positive for blaOXA-48 and the presence of this carbapenemase was confirmed by gene sequencing. Although plasmid analysis suggested that the blaOXA-48 is chromosomal in this isolate, it is still an alarming finding for potential transmission of antibiotic resistance genes to other bacteria in the gut. To our knowledge, this is the first report of the presence of blaOXA-48 in a Lactobacillus spp. and has utmost importance as these bacteria are used as probiotics. The isolation of these bacteria from sterile body sites should not go unnoticed.

Members of the Lactobacillus Genus Complex (LGC) as Opportunistic Pathogens: A Review

Microorganisms belonging to the Lactobacillus genus complex (LGC) are naturally associated or deliberately added to fermented food products and are widely used as probiotic food supplements. Moreover, these bacteria normally colonize the mouth, gastrointestinal (GI) tract, and female genitourinary tract of humans. They exert multiple beneficial effects and are regarded as safe microorganisms. However, infections caused by lactobacilli, mainly endocarditis, bacteremia, and pleuropneumonia, occasionally occur. The relevance of Lactobacillus spp. and other members of the LGC as opportunistic pathogens in humans and related risk factors and predisposing conditions are illustrated in this review article with more emphasis on the species L. rhamnosus that has been more often involved in infection cases. The methods used to identify this species in clinical samples, to distinguish strains and to evaluate traits that can be associated to pathogenicity, as well as future perspectives for improving the identification of potentially pathogenic strains, are outlined.

Rapid Identification and Quantification of Lactobacillus rhamnosus by Real-Time PCR Using a TaqMan Probe

Lactobacillus rhamnosus is a gram-positive, rod-shaped bacterium and is commonly used as a probiotic to maintain intestinal health. Recently, surveillance of Lactobacillus bacteremia was conducted using a biochemical test and conventional PCR assay; however, these assays are unable to quantify the target and might yield a false positive result. In this study, we developed an L. rhamnosus-specific quantitative PCR assay, which yields accurate and reproducible results on the basis of the specificity of a TaqMan probe targeting the unique 16S rDNA sequence of L. rhamnosus. The assay specifically detected the target bacterium, L. rhamnosus, and no nonspecific signals were generated under the assay conditions. With genomic DNA from the cells of L. rhamnosus (10¹ to 10⁶ cells), the threshold cycle values showed a linear dependence (R² = 0.9993). This L. rhamnosus-specific quantitative PCR assay can advance the research into the effects of this microorganism on microflora, microbial infections, and on the host.