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Viridans Group Streptococci (VGS) species-level identification is fundamental for patients management. Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been used for VGS identification but discrimination within the Mitis group resulted difficult. In this study, VGS identifications with two MALDI-TOF instruments, the Biotyper (Bruker) and the VITEK MS (bioMérieux) have been compared to those derived from tuf, soda and rpoB genes sequencing. VGS isolates were clustered and a dendrogram constructed using the Biotyper 3.0 software (Bruker). RpoB gene sequencing resulted the most sensitive and specific molecular method for S. pneumonia identification and was used as reference method. The sensitivity and the specificity of the VITEK MS in S. pneumonia identification were 100%, while the Biotyper resulted less specific (92.4%). In non pneumococcal VGS strains, the group-level correlation between rpoB and the Biotyper was 100%, while the species-level correlation was 61% after database upgrading (than 37% before upgrading). The group-level correlation between rpoB and the VITEK MS was 100%, while the species-level correlation was 36% and increases at 69% if isolates identified as S. mitis/S. oralis are included. The less accurate performance of the VITEK MS in VGS identification within the Mitis group was due to the inability to discriminate between S. mitis and S. oralis. Conversely, the Biotyper, after the release of the upgraded database, was able to discriminate between the two species. In the dendrogram, VGS strains from the same group were grouped into the same cluster and had a good correspondence with the gene-based clustering reported by other authors, thus confirming the validity of the upgraded version of the database. Data from this study demonstrated that MALDI-TOF technique can represent a rapid and cost saving method for VGS identification even within the Mitis group but improvements of spectra database are still recommended.

Background Viridans group streptococci of the Streptococcus mitis-oralis subgroup are important endovascular pathogens. They can rapidly develop high-level and durable non-susceptibility to daptomycin both in vitro and in vivo upon exposure to daptomycin. Two consistent genetic adaptations associated with this phenotype (i.e., mutations in cdsA and pgsA ) lead to the depletion of the phospholipids, phosphatidylglycerol and cardiolipin, from the bacterial membrane. Such alterations in phospholipid biosynthesis will modify carbon flow and change the bacterial metabolic status. To determine the metabolic differences between daptomycin-susceptible and non-susceptible bacteria, the physiology and metabolomes of S. mitis-oralis strains 351 (daptomycin-susceptible) and 351-D10 (daptomycin non-susceptible) were analyzed. S. mitis-oralis strain 351-D10 was made daptomycin non-susceptible through serial passage in the presence of daptomycin. Results Daptomycin non-susceptible S. mitis-oralis had significant alterations in glucose catabolism and a re-balancing of the redox status through amino acid biosynthesis relative to daptomycin susceptible S. mitis-oralis . These changes were accompanied by a reduced capacity to generate biomass, creating a fitness cost in exchange for daptomycin non-susceptibility. Conclusions S. mitis-oralis metabolism is altered in daptomycin non-susceptible bacteria relative to the daptomycin susceptible parent strain. As demonstrated in Staphylococcus aureus , inhibiting the metabolic changes that facilitate the transition from a daptomycin susceptible state to a non-susceptible one, inhibits daptomycin non-susceptibility. By preventing these metabolic adaptations in S. mitis-oralis , it should be possible to deter the formation of daptomycin non-susceptibility .

In hepatitis C virus infection, the progression of the clinical stage is associated with gut dysbiosis, even if patients are asymptomatic. Overgrowth of viridans streptococci can contribute to the production of ammonia in chronic hepatitis and liver cirrhosis. Abstract Background Little is known about the effect of hepatitis C virus (HCV) infection on gut microbiota and the relationship between alteration of gut microbiota and chronic hepatitis C (CHC) progression. We performed a comparative study of gut microbiota composition between CHC patients and healthy individuals. Methods Fecal samples from 166 CHC patients were compared with those from 23 healthy individuals; the gut microbiota community was analyzed using 16S ribosomal RNA gene sequencing. CHC patients were diagnosed with persistently normal serum alanine aminotransferase without evidence of liver cirrhosis (LC) (PNALT, n = 18), chronic hepatitis (CH, n = 84), LC (n = 40), and hepatocellular carcinoma in LC (n = 24). Results Compared with healthy individuals, bacterial diversity was lower in persons with HCV infection, with a decrease in the order Clostridiales and an increase in Streptococcus and Lactobacillus. Microbiota dysbiosis already appeared in the PNALT stage with the transient increase in Bacteroides and Enterobacteriaceae. Predicted metagenomics of microbial communities showed an increase in the urease gene mainly encoded by viridans streptococci during CHC progression, consistent with a significantly higher fecal pH in CH and LC patients than in healthy individuals or those in the PNALT stage. Conclusions HCV infection is associated with gut dysbiosis, even in patients with mild liver disease. Additionally, overgrowth of viridans streptococci can account for hyperammonemia in CH and LC. Further studies would help to propose a novel treatment strategy because the gut microbiome can be therapeutically altered, potentially reducing the complications of chronic liver disease.

Objective: The aim of this study was to established diagnostic approaches to dental caries using polymerase chain reaction technology. Methods: PCR series. 60 samples of oral bacteria were collected between 8/6/2023 and 12/1/2023, where 27 teeth showed a growth rate for bacterial culture (45%). The bacterial isolates under study were characterized. The sensitivity of the bacterial isolates of Streptococcus viridans under study to eight antibiotics was tested. The results of the current study showed that the resistance rates were as follows: 71.4% for tetracycline, 57% for augmentin, 57% for ciprofloxacin, 28% for clindamycin, 57% for erythromycin, 57% for doxycycline, and 28% for doxycycline for clarithromycin. Results: The minimum inhibitory concentration (MIC) for the bacterial isolates under study was determined for the tetracycline antibiotic. S. viridansisolates showed resistance to this antibiotic through a sensitivity test using the disk method, as the MIC value.  for the isolates ranged from (1024-8) micrograms/m l. The percentage of S. viridans isolates producing virulence factors was as follows: protease enzyme 42%, and membrane protease. Bioactive 71%, bacteriocin 14%, hemolycin 57%, DNAase 71%, capsule 28%, and lipase 28%. Conclusion: The total DNA of all bacterial isolates under study was extracted, after which a polymerase chain reaction (PCR) was performed for the S. viridans resistant to tetracycline and with an MIC value higher than 64 µg/ml using specialized primers targeting the specific sequence of the tetM gene with a size of 1,862bp. When the amplified products were migrated on an agarose gel, one band appeared in all tracks in the gel at the same level for all samples. The results showed that the presence of the tetM gene was 100%.

In this study, the performances of two matrix-assisted laser desorption ionization–time of flight mass spectrometry (MALDI-TOF MS) systems, MALDI Biotyper (Bruker Daltonics) and VITEK MS (bioMérieux), were evaluated in the identification of viridans group streptococci. Two collections of isolates were tested with both methods. From a panel of type collection strains ( n  = 54), MALDI Biotyper gave correct species-level identification for 51/54 (94 %) strains and 37/54 (69 %) strains for the VITEK MS in vitro diagnostic (IVD) method. Additionally, a collection of blood cultures isolates which had been characterized earlier with partial sequencing of 16S rRNA ( n  = 97) was analyzed. MALDI Biotyper classified 89 % and VITEK MS 93 % of these correctly to the group level. Comparison of species-level identification from the blood culture collection was possible for 36 strains. MALDI Biotyper identified 75 % and VITEK MS 97 % of these strains consistently. Among the clinical isolates, MALDI Biotyper misidentified 36 strains as Streptococcus pneumoniae . Nevertheless, our results suggest that the current MALDI-TOF methods are a good alternative for the identification of viridans streptococci and do perform as well as or better than commercial phenotypical methods.

With long delays observed between sampling and availability of results, the usefulness of blood cultures in the context of emergency infectious diseases has recently been questioned. Among methods that allow quicker bacterial identification from growing colonies, matrix-assisted laser desorption ionisation time-of-flight (MALDI-TOF) mass spectrometry was demonstrated to accurately identify bacteria routinely isolated in a clinical biology laboratory. In order to speed up the identification process, in the present work we attempted bacterial identification directly from blood culture bottles detected positive by the automate. We prospectively analysed routine MALDI-TOF identification of bacteria detected in blood culture by two different protocols involving successive centrifugations and then lysis by trifluoroacetic acid or formic acid. Of the 562 blood culture broths detected as positive by the automate and containing one bacterial species, 370 (66%) were correctly identified. Changing the protocol from trifluoroacetic acid to formic acid improved identification of Staphylococci, and overall correct identification increased from 59% to 76%. Lack of identification was observed mostly with viridans streptococci, and only one false positive was observed. In the 22 positive blood culture broths that contained two or more different species, only one of the species was identified in 18 samples, no species were identified in two samples and false species identifications were obtained in two cases. The positive predictive value of bacterial identification using this procedure was 99.2%. MALDI-TOF MS is an efficient method for direct routine identification of bacterial isolates in blood culture, with the exception of polymicrobial samples and viridans streptococci. It may replace routine identification performed on colonies, provided improvement for the specificity of blood culture broths growing viridans streptococci is obtained in the near future.

Intensive chemotherapy directed against acute myeloid leukemia of childhood is followed by profound neutropenia and high risk for bacterial and fungal infections, including viridans group streptococci as a common cause for gram-positive septicemia. Few retrospective studies have shown the efficacy of various antibiotic prophylactic regimens in children. We retrospectively studied 50 pediatric patients treated on the AML-BFM 2004 protocol between 2005 and 2015 at St. Anna Children’s Hospital and assessed the effect of antibiotic prophylaxis on the frequency of febrile neutropenia and bacterial sepsis. Fifty pediatric patients underwent 199 evaluable chemotherapy cycles. Viridans sepsis occurred after none of 98 cycles with prophylactic administration of teicoplanin/vancomycin in comparison to 12 cases of viridans sepsis among 79 cycles without systemic antibacterial prophylaxis (0 vs. 15 %, p  < 0.0001). In addition, there were significantly fewer episodes of febrile neutropenia in the teicoplanin/vancomycin group (44 % vs. no prophylaxis 82 %, p  < 0.0001). Severity of infection seemed to be worse when no antibiotic prophylaxis had been administered with a higher rate of intensive care unit treatment (0/98, 0 %, vs. 4/79, 5 %, p  = 0.038). So far, no increase of vancomycin-resistant enterococcus isolates in surveillance cultures was noticed. Antibiotic prophylaxis with teicoplanin (or vancomycin) appears safe and feasible and resulted in eradication of viridans sepsis and decreased incidence of febrile neutropenia in pediatric AML patients. The possibility to administer teicoplanin on alternate days on an outpatient basis or at home could contribute to patient’s quality of life and decrease health care costs.

Viridans group streptococci bloodstream infections (VGS BSI) remain a significant cause of mortality and morbidity in patients with severe neutropenia. The goal of our study was to evaluate clinical course and microbiological susceptibility of VGS BSI at our center. Retrospective analysis of all microbiologically documented bloodstream infections caused by VGS during the 9-year time period (from January 2006 until December 2014) was carried out. Only patients with severe neutropenia (< 500/μL) were included in the study. Clinical outcome and microbiological susceptibility pattern of isolates were recorded. Fifty-one individual patients with episode of VGS BSI were identified. The most frequent agent was Streptococcus mitis (23/51 cases, 45.1%). 88.2% (45/51) of patients were on recommended ciprofloxacin prophylaxis. 20/51 (39.2%) of patients suffered from mucositis at the time of diagnosis (10 patients had oral mucositis, 2 patients had bowel mucositis, and 8 patients both). Twenty-six patients (51.0%) had clinically relevant lung damage caused by VGS BSI (i.e., acute lung injury or acute respiratory distress syndrome). Twenty-four (47.0%) patients presented with bilateral lung infiltrated upon chest imaging, and two (4.0%) patients had unilateral lung infiltrates. Three patients (5.9%) died due to VGS BSI until day 28 of observation. No difference in signs of shock syndrome was observed in the patients during transplantation procedures compared to patients without transplantation as well as in a group received previous high-dose chemotherapy with cytosinarabinoside or in patients with mucositis. Only 3/51 of isolates (5.9%) were resistant to penicillin. All isolates were susceptible to empirical treatment. While the penicillin resistance of VGS remains low in middle Europe, initial antibiotic therapy of febrile neutropenia are still effective in most cases. The mortality and complication rates of VGS BSI were comparable to other studies, and no specific risk factor of shock presence could be identified.

Background Methods for assigning strains to bacterial species are cumbersome and no longer fit for purpose. The concatenated sequences of multiple house-keeping genes have been shown to be able to define and circumscribe bacterial species as sequence clusters. The advantage of this approach (multilocus sequence analysis; MLSA) is that, for any group of related species, a strain database can be produced and combined with software that allows query strains to be assigned to species via the internet. As an exemplar of this approach, we have studied a group of species, the viridans streptococci, which are very difficult to assign to species using standard taxonomic procedures, and have developed a website that allows species assignment via the internet. Results Seven house-keeping gene sequences were obtained from 420 streptococcal strains to produce a viridans group database. The reference tree produced using the concatenated sequences identified sequence clusters which, by examining the position on the tree of the type strain of each viridans group species, could be equated with species clusters. MLSA also identified clusters that may correspond to new species, and previously described species whose status needs to be re-examined. A generic website and software for electronic taxonomy was developed. This site http://www.eMLSA.net allows the sequences of the seven gene fragments of a query strain to be entered and for the species assignment to be returned, according to its position within an assigned species cluster on the reference tree. Conclusion The MLSA approach resulted in the identification of well-resolved species clusters within this taxonomically challenging group and, using the software we have developed, allows unknown strains to be assigned to viridans species via the internet. Submission of new strains will provide a growing resource for the taxonomy of viridans group streptococci, allowing the recognition of potential new species and taxonomic anomalies. More generally, as the software at the MLSA website is generic, MLSA schemes and strain databases for other groups of related species can be hosted at this website, providing a portal for microbial electronic taxonomy.

Streptococcus suis (S. suis) is a swine pathogen that can cause sepsis, meningitis, endocarditis, and other infectious diseases; it is also a zoonotic pathogen that has caused a global surge in fatal human infections. The widespread prevalence of multidrug-resistant S. suis strains and the decline in novel antibiotic candidates have necessitated the development of alternative antimicrobial agents. In this study, AVPL, the Aerococcus viridans (A. viridans) phage lysin, was found to exhibit efficient bactericidal activity and broad lytic activity against multiple serotypes of S. suis. A final concentration of 300 μg/mL AVPL reduced S. suis counts by 4–4.5 log10 within 1 h in vitro. Importantly, AVPL effectively inhibited 48 h S. suis biofilm formation and disrupted preformed biofilms. In a mouse model, 300 μg/mouse AVPL protected 100% of mice from infection following the administration of lethal doses of multidrug-resistant S. suis type 2 (SS2) strain SC19, reduced the bacterial load in different organs, and effectively alleviated inflammation and histopathological damage in infected mice. These data suggest that AVPL is a valuable candidate antimicrobial agent for treating S. suis infections.