Streptococcus bovis infection of the central nervous system in adults: Report of 4 cases and literature review.

OBJECTIVES: To describe the clinical features, history and association with intestinal disease in central nervous system (CNS) S. bovis infections. METHODS: Four cases of S. bovis CNS infections from our institution are presented. Additionally a systematic literature review of articles published between 1975 and 2021 in PubMed/MEDLINE was conducted. RESULTS: 52 studies with 65 cases were found; five were excluded because of incomplete data. In total 64 cases were analyzed including our four cases: 55 with meningitis and 9 with intracranial focal infections. Both infections were frequently associated with underlying conditions (70.3%) such as immunosuppression (32.8%) or cancer (10.9%). In 23 cases a biotype was identified, with biotype II being the most frequent (69.6%) and S. pasteurianus the most common within this subgroup. Intestinal diseases were found in 60.9% of cases, most commonly neoplasms (41.0%) and Strongyloides infestation (30.8%). Overall mortality was 17.1%, with a higher rate in focal infection (44.4% vs 12.7%; p=0.001). CONCLUSIONS: CNS infections due to S. bovis are infrequent and the most common clinical form is meningitis. Compared with focal infections, meningitis had a more acute course, was less associated with endocarditis and had a lower mortality. Immunosuppression and intestinal disease were frequent in both infections.

Transcriptional control of carbohydrate catabolism by the CcpA protein in the ruminal bacterium Streptococcus bovis.

As a potent, pleiotropic regulatory protein in Gram-positive bacteria, catabolite control protein A (CcpA) mediates the transcriptional control of carbohydrate metabolism in Streptococcus bovis, a lactate-producing bacterium that plays an essential role in rumen acidosis in dairy cows. Although the rumen uptake of carbohydrates is multi-substrate, the focus of S. bovis research thus far has been on the glucose. With the aid of gene deletion, whole-genome sequencing, and transcriptomics, we have unraveled the role of CcpA in carbohydrate metabolism, on the one hand, and acidosis, on the other, and we show that the S. bovis strain S1 encodes "Carbohydrate-Active Enzymes" and that ccpA deletion slows the organism's growth rate and modulates the organic acid fermentation pathways toward lower lactate, higher formate, and acetate in the maltose and cellobiose. Furthermore, this study revealed the different regulatory functions of the CcpA protein in rumen metabolism and acidosis.IMPORTANCEThis study is important as it illustrates the varying regulatory role of the Streptococcus bovis catabolite control protein A protein in carbohydrate metabolism and the onset of acidosis in dairy cattle.

Improved identification of Streptococcus bovis-Streptococcus equinus-complex species and subspecies by MALDI-TOF MS using a novel library.

OBJECTIVES: To develop an in-house matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) library for improved identification of species and subspecies of the Streptococcus bovis/Streptococcus equinus-complex (SBSEC). METHODS: A total of 236 SBSEC isolates from blood stream infections and culture collections, determined by whole genome sequencing to subspecies level, were grown in brain heart infusion broth. Mass spectra were collected using the Bruker MALDI Biotyper system after ethanol-formic acid extraction. Main spectral profiles from 117 isolates were used to create the "SBSEC-CMRS library." The remaining 119 spectra were used for evaluation of Bruker MALDI Biotyper (MBT) Compass Library Revision K (2022) and the SBSEC-CMRS library. RESULTS: The Bruker library correctly identified species and subspecies in 72 of 119 (61 %) isolates, while the SBSEC-CMRS library identified 116 of 119 (97 %), using a cutoff score of ≥2.0. CONCLUSIONS: The SBSEC-CMRS library showed sufficient diagnostic accuracy, and can be implemented in clinical practice for SBSEC species and subspecies identification.

Characterization of two lytic bacteriophages, infecting Streptococcus bovis/equinus complex (SBSEC) from Korean ruminant.

Streptococcus bovis/equinus complex (SBSEC) is one of the most important lactic acid-producing rumen bacteria causing subacute ruminal acidosis. Despite the significance of the ruminal bacteria, lytic bacteriophages (phages) capable of infecting SBSEC in the rumen have been rarely characterized. Hence, we describe the biological and genomic characteristics of two lytic phages (designated as vB_SbRt-pBovineB21 and vB_SbRt-pBovineS21) infecting various SBSEC species, including the newly reported S. ruminicola. The isolated SBSEC phages were morphologically similar to Podoviridae and could infect other genera of lactic acid-producing bacteria, including Lactococcus and Lactobacillus. Additionally, they showed high thermal- and pH-stability, and those characteristics induce strong adaptation to the ruminal environment, such as the low pH found in subacute ruminal acidosis. Genome-based phylogeny revealed that both phages were related to Streptococcus phage C1 in the Fischettivirus. However, they had a lower nucleotide similarity and distinct genomic arrangements than phage C1. The phage bacteriolytic activity was evaluated using S. ruminicola, and the phages efficiently inhibited planktonic bacterial growth. Moreover, both phages could prevent bacterial biofilms of various SBSEC strains and other lactic acid-producing bacteria in vitro. Thus, the newly isolated two SBSEC phages were classified as new Fischettivirus members and could be considered as potential biocontrol agents against ruminal SBSEC bacteria and their biofilms.

The interaction between liver cirrhosis, infection by Streptococcus bovis, and colon cancer.

Whether cirrhotic patients with Streptococcus bovis bacteremia have an increased risk of colorectal neoplasm is uncertain. A multicentric retrospective cohort study was conducted investigating associations between S. bovis biotype and species, cirrhosis, and colorectal neoplasm. Out of 779 patients with S. bovis bacteremia, 69 (8.7%) had cirrhosis. No differences were found in the prevalence of colorectal neoplasm between cirrhotic and non-cirrhotic patients undergoing colonoscopy. Among cirrhotic patients, prevalence of colorectal neoplasms was higher in S. bovis biotype I (S. gallolyticus) bacteremia (80%) than in S. bovis biotype II (33.3%; p < 0.007). In conclusion, risk of colorectal neoplasm is high among cirrhotic patients with S. gallolyticus bacteremia.

Comparative Evaluation of Current Biochemical-, Sequencing-, and Proteomic-Based Identification Methods for the Streptococcus bovis Group.

The Streptococcus bovis group (previously group D streptococci) consists of seven distinct species and subspecies. Definitive identification within the group is important, as certain organisms have been associated with gastrointestinal carcinoma, bacteremia, infective endocarditis, meningitis, biliary tract disease, and carcinoma, among others. Definitive identification, however, remains elusive due to limitations and inconsistencies across commonly used identification platforms in the United States. Here, we compared the performance of standard biochemical (Trek Gram-positive identification [GPID] plate, Vitek 2 GPID), sequencing (16S rDNA, sodA) databases (NCBI, RDP, CDC MicrobeNet), and matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) platforms (Vitek MS, Bruker Biotyper MS) using a set of eight type strains representing all seven strains within the S. bovis group. Despite the evaluation of contemporary methods, no single platform was able to definitively identify all type strains within the S. bovis group. Vitek MS (85.7%, 7/8) provided the most accurate definitive identifications, followed by sodA sequencing (75%, 6/8). Vitek 2 and Bruker Biotyper RUO platforms performed the next best (62.5%, 5/8). All remaining platforms failed to adequately differentiate type strains within the S. bovis group (range, 0 to 37.5%). Laboratorians and clinicians should be aware of the identification limitations of routine testing algorithms and incorporate reflex testing, when appropriate, to platforms such as Vitek MS and/or sodA sequencing that are more able to definitively identify S. bovis group organisms. Further clinical evaluation was conducted using 65 clinical isolates from three geographically distinct U.S. institutions. Future improvements in identification platforms may reveal new clinical and epidemiological trends for members of the S. bovis group.

Species and biotypes of Streptococcus bovis causing infective endocarditis.

INTRODUCTION: Streptococcus bovis/equinus complex (SBEC) is a major cause of infective endocarditis (IE), although its incidence varies greatly depending on the geographical area. The characteristics of IE caused by Streptococcus gallolyticus susp. gallolyticus are well known; there are hardly any descriptions of IE caused by other species or biotypes. METHODS: Retrospective cohort study, from 1990 to 2019, of all SBEC IE in adults in three Spanish hospitals, Lugo (LH), Barcelona (BH) and Ferrol (FH) where the population is mainly rural, urban and mixed, respectively. The incidence of IE was analyzed in 3 areas. Clinical characteristics of IE (277 cases, 258 biotyped) were compared according to SBEC species and biotypes. RESULTS: There are significant differences between the incidence of SBEC IE in HL (27.9/106) vs. HF and HB (8.8 and 7,1, respectively, p<0.001). We found significant differences (SbI vs. SbII) in mean age (68.5 vs. 73 years; p<0.01), duration of symptoms before diagnosis (46.9±46.5 vs. 30.4±40.9 days; p<0.01), presence of comorbidities: 39.1% (78) vs. 54.2% (32; p<0.04), predisposing heart illness:62.3% (124) vs. 81.3% (48; p<0.006), particularly, prosthetic or intravascular devices IE: 24.6% (49) vs. 52.4% (31; p<0.001), bi-valve involvement:23.6% (47) vs. 11.8% (7; p<0.05) and heart failure: 24.6% (49) vs. 38.9% (23; p<0.03). There were no significant differences in embolic events, need for surgery or mortality. The association with CRC was high in both groups: 77.7% vs. 66.6%. CONCLUSIONS: IE due to SBEC has geographical variations in incidence and different clinical characteristics among biotypes. The association with CRC was high.

A Case of Postoperative Endophthalmitis Caused by Streptococcus Bovis.

PURPOSE: To report a case of postoperative endophthalmitis caused by Streptococcus bovis (S. bovis). METHODS: Retrospective case report. RESULTS: A 50-year-old healthy man presented with endophthalmitis 16 hours after silicone oil removal. Vitreous cultures remained positive for S. bovis. In addition to vitreous and anterior chamber lavage, the patient received five intravitreal injections in total. All the above aggressive measures did not effectively prevent the deterioration of the disease and the patient was discharged with a final outcome of retinal detachment and atrophia bulbi with no light perception. CONCLUSIONS: To the best of our knowledge, this is the first report of postoperative endophthalmitis caused by S. bovis.

Platelet Activation and Aggregation Induced by Streptococcus bovis/Streptococcus equinus Complex.

Streptococcus bovis/Streptococcus equinus complex (SBSEC) is a common cause of infective endocarditis (IE). For IE-pathogens, the capacity to activate and aggregate platelets is believed to be an important virulence mechanism. While the interactions between bacteria and platelets have been described in detail for many Gram-positive pathogens, little research has been carried out with SBSEC in this respect. Twenty-six isolates of the four most common species and subspecies of SBSEC identified in bacteremia were collected, and interactions with platelets were investigated in platelet rich plasma (PRP) from three donors. Aggregation was studied using light-transmission aggregometry and platelet activation using flow cytometry detecting surface upregulation of CD62P. Platelets and serum were treated with different inhibitors to determine mechanisms involved in platelet aggregation and activation. Twenty-two of 26 isolates induced aggregation in at least one donor, and four isolates induced aggregation in all three donors. In PRP from donor 1, isolate SL1 induced a rapid aggregation with a median time of 70 s to reach 50% aggregation. Blockade of the platelet Fc-receptor or enzymatic cleavage of IgG abolished platelet activation and aggregation. The capacity for bacteria-induced platelet aggregation was also shown to be transferable between donors through serum. SBSEC mediates platelet aggregation in an IgG and IgG-Fc-receptor dependent manner. Bacterial activation of platelets through this pathway is common for many bacteria causing IE and could be a potential therapeutic target for the prevention and treatment of this infection. IMPORTANCE The capacity of bacteria to activate and aggregate platelets is believed to contribute to the pathogenesis of IE. The Streptococcus bovis/Streptococcus equinus complex (SBSEC) contains known IE-pathogens, but there is limited research on the different subspecies ability to interact with platelets and what signaling pathways are involved. This study reports that 22 of 26 tested isolates of different subspecies within SBSEC can induce aggregation, and that aggregation is host dependent. The Fc-IgG-receptor pathway was shown essential for platelet activation and aggregation. To the best of our knowledge, this is the first study that reports on platelet interactions of SBSEC-isolates other than Streptococcus gallolyticus subspecies gallolyticus as well as the first study to report of mechanisms of platelet interaction of SBSEC-isolates. It adds SBSEC to a group of bacteria that activate and aggregate platelets via the platelet Fc-receptor. This could be a potential therapeutic target for prevention of IE.

Streptococcus ruminicola sp. nov., new species of the Streptococcus bovis/Streptococcus equinus complex (SBSEC) isolated from the rumen of Korean domestic ruminants.

A total of three Gram-positive, and oxidase and catalase-negative facultative anaerobic non-motile bacteria were isolated from the rumen fluid of cows and goats and these strains were designated CNU_G2T, CNU_77-61, and CNU_G3. They grew at 20-45 °C, pH 6.5-7, and 0-6.5% NaCl (w/v). The G + C contents (%) of the three isolates were 37.9, 37.8 and 37.8, respectively. Phylogenomic analysis indicated that these strains were distinct from other Streptococcus species. The average nucleotide identity between the isolates and the closest strain S. infantarius subsp. infantarius ATCC BAA-102T was 94.0-94.5%, while the digital DNA-DNA hybridization (dDDH) values between the isolates and the aforementioned related strain were 58.2-61.4%, respectively. Fatty acid analysis revealed higher proportions of C16:0 (> 28%) in all three isolates, while the proportion of C18:0 was higher in CNU_G2T (25.8%); however, it was less than 12% in all the representing strains used in the study. The C14:0 composition of strains CNU_77-61 (22.1%) and CNU_G3 (24.1%) was higher than that of type strains of CNU_G2T (8.1%). Based on the morphological, biochemical, and molecular phylogenetic features of the three novel isolates, they represent a novel species of the genus Streptococcus, for which we propose as Streptococcus ruminicola sp. nov. The type strain is CNU_G2T (= KCTC 43308T = GDMCC 1.2785T).

Bacteraemia and infective endocarditis with Streptococcus bovis-Streptococcus equinus-complex: a retrospective cohort study.

BACKGROUND: Streptococcus bovis/equinus complex (SBSEC) comprise several species and subspecies and is a common cause of infective endocarditis (IE). S. gallolyticus subsp. gallolyticus (Sg gallolyticus) accounts for a majority of SBSEC IE, but the risk of IE for other subspecies is largely unknown. We aimed to investigate the clinical presentation of bacteraemia, and proportion of patients with IE in bacteraemia with the most common subspecies. METHODS: A retrospective cohort study of SBSEC-bacteraemia identified in clinical laboratory databases, in Skåne Region, Sweden, 2003-2018. Bacteraemia with Sg gallolyticus, S. gallolyticus subsp. pasteurianus (Sg pasteurianus), S. lutetiensis and S. infantarius subsp. infantarius (Si infantarius) were included. Subspecies was identified by whole genome sequencing. Medical charts were reviewed according to a predetermined protocol, IE was defined by the criteria from European Society of Cardiology. RESULTS: In total, 210 episodes of SBSEC-bacteraemia were included. Definite IE was identified in 28/210 (13%) episodes. Of these, 7/28 (25%) were prosthetic valve-IE, 1/28 (4%) related to a cardiovascular implantable electronic device and 10/28 (36%) required heart valve surgery. The proportions of IE among different subspecies were: Sg gallolyticus 17/52 (33%), Si infantarius 5/31 (16%), Sg pasteurianus 4/83 (5%) and S. lutetiensis 2/44 (5%) (p < 0.001). Sg pasteurianus and S. lutetiensis were more often associated with intra-abdominal- and polymicrobial infection. CONCLUSION: The proportion of IE in SBSEC-bacteraemia varies substantially depending on subspecies. Echocardiography should always be considered in bacteraemia with Sg gallolyticus and Si infantarius, and can sometimes be omitted in bacteraemia with Sg pasteurianus and S. lutetiensis.

Regulation of CcpA on the growth and organic acid production characteristics of ruminal Streptococcus bovis at different pH.

BACKGROUND: Catabolite control protein A (CcpA) regulates the transcription of lactate dehydrogenase and pyruvate formate-lyase in Streptococcus bovis, but knowledge of its role in response to different pH is still limited. In this study, a ccpA-knockout strain of S. bovis S1 was constructed and then used to examine the effects of ccpA gene deletion on the growth and fermentation characteristics of S. bovis S1 at pH 5.5 or 6.5. RESULTS: There was a significant interaction between strain and pH for the maximum specific growth rate (µmax) and growth lag period (λ), which caused a lowest µmax and a longest λ in ccpA-knockout strain at pH 5.5. Deletion of ccpA decreased the concentration and molar percentage of lactic acid, while increased those of formic acid. Strains at pH 5.5 had decreased concentrations of lactic acid and formic acid compared to pH 6.5. The significant interaction between strain and pH caused the highest production of total organic acids and acetic acid in ccpA-knockout strain at pH 6.5. The activities of α-amylase and lactate dehydrogenase decreased in ccpA-knockout strain compared to the wild-type strain, and increased at pH 5.5 compared to pH 6.5. There was a significant interaction between strain and pH for the activity of acetate kinase, which was the highest in the ccpA-knockout strain at pH 6.5. The expression of pyruvate formate-lyase and acetate kinase was higher in the ccpA-knockout strain compared to wild-type strain. The lower pH improved the relative expression of pyruvate formate-lyase, while had no effect on the relative expression of acetate kinase. The strain × pH interaction was significant for the relative expression of lactate dehydrogenase and α-amylase, both of which were highest in the wild-type strain at pH 5.5 and lowest in the ccpA-knockout strain at pH 6.5. CONCLUSIONS: Overall, low pH inhibited the growth of S. bovis S1, but did not affect the fermentation pattern. CcpA regulated S. bovis S1 growth and organic acid fermentation pattern. Moreover, there seemed to be an interaction effect between pH and ccpA deletion on regulating the growth and organic acids production of S. bovis S1.

Laboratory identification and clinical characteristics of Streptococcus bovis/Streptococcus equinus complex bacteremia: a retrospective, multicenter study in Hiroshima, Japan.

BACKGROUND: Bacteremia due to the Streptococcus bovis/Streptococcus equinus complex (SBSEC) is associated with specific diseases, such as colorectal cancer and infective endocarditis. This study aimed to evaluate the clinical characteristics of SBSEC bacteremia and the accuracy of identification of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and phenotypic identification systems for SBSEC isolates. METHODS: We analyzed patients with SBSEC bacteremia retrospectively between 2012 and 2019 at three hospitals in Japan. We re-identified each SBSEC isolate using sequencing superoxide dismutase (sodA) analysis, MALDI-TOF MS using the MALDI Biotyper, and phenotypic identification using the VITEK2. RESULTS: During the study period, 39 patients with SBSEC bacteremia were identified. S. gallolyticus subsp. pasteurianus (SGSP, n = 29), S. gallolyticus subsp. gallolyticus (SGSG, n = 5), S. lutetiensis (SL, n = 4), and S. infantarius subsp. infantarius (n = 1) were identified using sodA sequencing analysis. Primary bacteremia (36%) was the most common cause of bacteremia, followed by infective endocarditis (26%) and biliary tract infections (23%). Colorectal cancer was associated significantly with SGSG bacteremia, while the sources of bacteremia were similar in each SBSEC subspecies. The MALDI Biotyper was significantly more accurate in identifying the SBSEC isolates at the subspecies level compared to the VITEK2 (92% vs. 67%, P = 0.010). In contrast, there were no significant differences in the rates of correct identification of the SBSEC isolates at the species level between the MALDI Biotyper and the VITEK2 (100% vs. 87%, P = 0.055). CONCLUSIONS: Bacteremia with SGSG was associated with colorectal cancer, and the sources of bacteremia were similar in each SBSEC subspecies. The MALDI-TOF MS was significantly more accurate in identifying SBSEC isolates at the subspecies level than the phenotypic identification systems. The accurate identification of SBSEC isolates using the MALDI-TOF MS and phenotypic identification systems was sufficient at the species level, but it was insufficient at the subspecies level. Therefore, it may be reasonable for clinicians to perform echocardiographies and colonoscopies in all patients with SBSEC bacteremia.

Development of Electrochemical DNA Biosensor for Equine Hindgut Acidosis Detection.

The pH drop in the hindgut of the horse is caused by lactic acid-producing bacteria which are abundant when a horse's feeding regime is excessively carbohydrate rich. This drop in pH below six causes hindgut acidosis and may lead to laminitis. Lactic acid-producing bacteria Streptococcus equinus and Mitsuokella jalaludinii have been found to produce high amounts of L-lactate and D-lactate, respectively. Early detection of increased levels of these bacteria could allow the horse owner to tailor the horse's diet to avoid hindgut acidosis and subsequent laminitis. Therefore, 16s ribosomal ribonucleic acid (rRNA) sequences were identified and modified to obtain target single stranded deoxyribonucleic acid (DNA) from these bacteria. Complementary single stranded DNAs were designed from the modified target sequences to form capture probes. Binding between capture probe and target single stranded deoxyribonucleic acid (ssDNA) in solution has been studied by gel electrophoresis. Among pairs of different capture probes and target single stranded DNA, hybridization of Streptococcus equinus capture probe 1 (SECP1) and Streptococcus equinus target 1 (SET1) was portrayed as gel electrophoresis. Adsorptive stripping voltammetry was utilized to study the binding of thiol modified SECP1 over gold on glass substrates and these studies showed a consistent binding signal of thiol modified SECP1 and their hybridization with SET1 over the gold working electrode. Cyclic voltammetry and electrochemical impedance spectroscopy were employed to examine the binding of thiol modified SECP1 on the gold working electrode and hybridization of thiol modified SECP1 with the target single stranded DNA. Both demonstrated the gold working electrode surface was modified with a capture probe layer and hybridization of the thiol bound ssDNA probe with target DNA was indicated. Therefore, the proposed electrochemical biosensor has the potential to be used for the detection of the non-synthetic bacterial DNA target responsible for equine hindgut acidosis.

PCR screening reveals abundance of bovicin-like bacteriocins among ruminal Streptococcus spp. isolated from beef and dairy cattle.

AIMS: To investigate the inhibitory activity and the distribution of biosynthetic genes encoding bovicin-like bacteriocins among ruminal Streptococcus isolated from beef and dairy cattle. METHODS AND RESULTS: Most isolates were classified as Streptococcus equinus and Streptococcus lutetiensis based on 16S rRNA sequencing. The antimicrobial activity of 150 ruminal streptococci isolated from beef and dairy cattle were tested by deferred inhibition assays and their genetic diversity was characterized by BOX-PCR. The frequency of biosynthetic genes associated with the biosynthesis of bovicin-like bacteriocins (bovicin HC5 and bovicin 255) was investigated by PCR screening. Approximately 33% of the ruminal streptococci isolated from Nellore heifers showed inhibitory activity in vitro with the majority harbouring genes for bacteriocin biosynthesis. In contrast, streptococci from Holstein cows showed limited inhibitory activity and a lower frequency of bacteriocin biosynthetic genes. CONCLUSIONS: Streptococcus from the rumen of beef and dairy cattle exhibit remarkable differences in inhibitory activity and distribution of genes associated with the biosynthesis of prototypical bovicins (bovicin HC5 and bovicin 255). SIGNIFICANCE AND IMPACT OF THE STUDY: Our findings demonstrate that bovicin HC5 is distributed among ruminal streptococci from different breeds of cattle. The high degree of conservation of the bovicin HC5 structural gene among strains of ruminal streptococci suggests that random genetic drift is not a dominant force in the evolution of this bacteriocin.

Assessing the inactivation capabilities of two commercially available platelet component pathogen inactivation systems: effectiveness at end of shelf life.

BACKGROUND AND OBJECTIVES: The inactivation capabilities of the two current commercially available pathogen inactivation (PI) systems for platelet components (PC), Mirasol and Intercept, were investigated by determination of the absence of viable bacteria at the end of shelf life by testing the entire contents of the PC by enrichment culture (terminal sterility). METHODS: A pool-and-split method was used, with two treated units and one untreated control per inoculum concentration. Pairs of PC bags were inoculated with a single bacterial species. Three concentrations (n = 2 per concentration), which incremented tenfold, were tested initially based on published data from the manufacturer. Dependent on these results, the concentrations subsequently tested were either increased or decreased until the inactivation capability of the system was derived. Bacterial count was determined post-spiking, immediately prior to treatment (2 h from spiking), immediately after treatment and at the end of shelf life (day seven). Enrichment culture was performed immediately prior to treatment, after treatment and at the end of shelf life. RESULTS: The inactivation capabilities, in CFU/ml, of Intercept and Mirasol, respectively, at the end of PC shelf life were as follows: Staphylococcus aureus ≥ 107 , <101 ; Staphylococcus epidermidis ≥106 , <102 ; Klebsiella pneumoniae 105 , <101 ; Streptococcus bovis ≥107 , 101 , Escherichia coli ≥106 , <101 ; Streptococcus pneumoniae ≥106 , 103 ; Streptococcus mitis ≥107 , 101 ; Listeria monocytogenes ≥107 , 101 ; Streptococcus dysgalactiae ≥107 , <101 ; Serratia marcescens 103 , <101 ; Pseudomonas aeruginosa 103 , Mirasol not tested; and Bacillus cereus < 102 , Mirasol not tested. CONCLUSION: The inactivation capability of Intercept was greater than that of Mirasol. Inactivation capability (by terminal sterility) is the most meaningful measure to evaluate a PI system for bacteria, rather than logarithmic reduction assessed immediately after treatment by plate count. PI offers a possible alternative to bacterial screening if treatment is performed at an appropriate time dependent on the inactivation capabilities of the system.

Intestinal microbiota and its association with colon cancer and red/processed meat consumption.

The human colon harbors a high number of microorganisms that were reported to play a crucial role in colorectal carcinogenesis. In the recent decade, molecular detection and metabolomic techniques have expanded our knowledge on the role of specific microbial species in promoting tumorigenesis. In this study, we reviewed the association between microbial dysbiosis and colorectal carcinoma (CRC). Various microbial species and their association with colorectal tumorigenesis and red/processed meat consumption have been reviewed. The literature demonstrated a significant abundance of Fusobacterium nucleatum, Streptococcus bovis/gallolyticus, Escherichia coli, and Bacteroides fragilis in patients with adenoma or adenocarcinoma compared to healthy individuals. The mechanisms in which each organism was postulated to promote colon carcinogenesis were collated and summarized in this review. These include the microorganisms' ability to adhere to colon cells; modulate the inhibition of tumor suppressor genes, the activations of oncogenes, and genotoxicity; and activate downstream targets responsible for angiogenesis. The role of these microorganisms in conjugation with meat components including N-nitroso compounds, heterocyclic amines, and heme was also evident in multiple studies. The outcome of this review supports the role of red meat consumption in modulating CRC progression and the possibility of gut microbiome influencing the relationship between CRC and diet. The study also demonstrates that microbiota analysis could potentially complement existing screening methods when detecting colonic lesions.

Stimulation of Bovicin HC5 Production and Selection of Improved Bacteriocin-Producing Streptococcus equinus HC5 Variants.

Bovicin HC5 is a peptide that has inhibitory activity against various pathogenic microorganisms and food spoilage bacteria. Aiming to improve the productivity of this bacteriocin, we evaluated several potential factors that could stimulate the synthesis of bovicin HC5 and selected variants of Streptococcus equinus (Streptococcus bovis) HC5 with enhanced bacteriocin production by adaptive laboratory evolution (ALE). The highest production of the bacteriocin (1.5-fold) was observed when Strep. equinus HC5 was cultivated with lactic acid (100 mmol/L). For the ALE experiment, Strep. equinus HC5 cells were subjected to acid-shock (pH 3.0 for 2 h) and maintained in continuous culture for approximately 140 generations (40 days) in media with lactic acid (100 mmol/L) and pH-controlled at 5.5 ± 0.2. An adapted variant was selected showing a distinct phenotype (sedimentation, pigmentation) compared with the parental strain. Bacteriocin production increased 2-fold in this adapted Strep. equinus HC5 variant, which appears to be associated with changes in the cell envelope of the adapted variant and enhanced bacteriocin release into the culture media. In addition, the adapted variant showed higher levels of expression of all bovicin HC5 biosynthetic genes compared with the parental strain during the early and late stages of growth. Results presented here indicate that ALE is a promising strategy for selecting strains of lactic acid bacteria with increased production of bacteriocins.

Extensive bacteriocin gene shuffling in the Streptococcus bovis/Streptococcus equinus complex reveals gallocin D with activity against vancomycin resistant enterococci.

Streptococcus gallolyticus LL009 produces gallocin D, a narrow spectrum two component bacteriocin with potent activity against vancomycin-resistant enterococci. Gallocin D is distinct from gallocin A, a separate two component bacteriocin produced by S. gallolyticus. Although the gene clusters encoding gallocin A and gallocin D have a high degree of gene synteny, the structural genes are highly variable and appear to have undergone gene shuffling with other streptococcal species. Gallocin D was analysed in laboratory-based experiments. The mature peptides are 3,343 ± 1 Da and 3,019 ± 1 Da and could be readily synthesized and display activity against a vancomycin resistant Enterococcus strain EC300 with a MIC value of 1.56 µM. Importantly, these bacteriocins could contribute to the ability of S. gallolyticus to colonize the colon where they have been associated with colorectal cancer.