Human Serum Supplementation Promotes Streptococcus mitis Growth and Induces Specific Transcriptomic Responses.

Streptococcus mitis is a normal member of the human oral microbiota and a leading opportunistic pathogen causing infective endocarditis (IE). Despite the complex interactions between S. mitis and the human host, understanding of S. mitis physiology and its mechanisms of adaptation to host-associated environments is inadequate, especially compared with other IE bacterial pathogens. This study reports the growth-promoting effects of human serum on S. mitis and other pathogenic streptococci, including S. oralis, S. pneumoniae, and S. agalactiae. Using transcriptomic analyses, we identified that, with the addition of human serum, S. mitis downregulates uptake systems for metal ions and sugars, fatty acid biosynthetic genes, and genes involved in stress response and other processes related with growth and replication. S. mitis upregulates uptake systems for amino acids and short peptides in response to human serum. Zinc availability and environmental signals sensed by the induced short peptide binding proteins were not sufficient to confer the growth-promoting effects. More investigation is required to establish the mechanism for growth promotion. Overall, our study contributes to the fundamental understanding of S. mitis physiology under host-associated conditions. IMPORTANCE S. mitis is exposed to human serum components during commensalism in the human mouth and bloodstream pathogenesis. However, the physiological effects of serum components on this bacterium remain unclear. Using transcriptomic analyses, S. mitis biological processes that respond to the presence of human serum were revealed, improving the fundamental understanding of S. mitis physiology in human host conditions.

Emerging issues on Staphylococcus aureus endocarditis and the role in therapy of daptomycin plus fosfomycin.

INTRODUCTION: Methicillin-resistant and -susceptible Staphylococcus aureus (MRSA/MSSA) infections are a major global health-care problem. Bacteremia with S. aureus exhibits high rates of morbidity and mortality and can cause complicated infections such as infective endocarditis (IE). The emerging resistance profile of S. aureus is worrisome, and several international agencies have appealed for new treatment approaches to be developed. AREAS COVERED: Daptomycin presents a rapid bactericidal effect against MRSA and has been considered at least as effective as vancomycin in treating MRSA bacteremia. However, therapy failure is often related to deep-seated infections, e.g. endocarditis, with high bacterial inocula and daptomycin regimens <10 mg/kg/day. Current antibiotic options for treating invasive S. aureus infections have limitations in monotherapy. Daptomycin in combination with other antibiotics, e.g. fosfomycin, may be effective in improving clinical outcomes in patients with MRSA IE. EXPERT OPINION: Exploring therapeutic combinations has shown fosfomycin to have a unique mechanism of action and to be the most effective option in preventing the onset of resistance to and optimizing the efficacy of daptomycin, suggesting the synergistic combination of fosfomycin with daptomycin is a useful alternative treatment option for MSSA or MRSA IE.

Molecular Analysis With 16S rRNA PCR/Sanger Sequencing and Molecular Antibiogram Performed on DNA Extracted From Valve Improve Diagnosis and Targeted Therapy of Infective Endocarditis: A Prospective Study.

BACKGROUND: Molecular analysis (MA) on heart valve (HV) improves the microbiologic diagnosis of infectious endocarditis (IE). The main drawback of MA is the lack of antimicrobial susceptibility information. METHODS: We conducted a prospective cohort observational study of consecutive adult patients from April 2012 to May 2021 who underwent valve surgery at our hospital. The performance of MA, blood cultures (BC) and valve cultures (VC), and the diagnostic and therapeutic impact of MA were evaluated. Molecular antibiogram results were compared to culture-based antimicrobial susceptibility testing (AST). RESULTS: A total of 137 patients with definite IE and 52 patients with no IE were enrolled in the study. Among IE cases BC, VC, and MA were positive in 75 (55%), 30 (22%), and 120 (88%) of IE cases, respectively. Among 62 cases of BC-negative IE (BCNE), 57 achieved diagnosis with MA. MA led to a change of antimicrobial therapy in 92% of BCNE. MA was negative in 100% of patients with no IE. Molecular antibiogram performed on 17 valve specimens that resulted positive for pathogens potential carrier of genes encoding for multidrug resistant mechanisms showed 100% concordance with AST. CONCLUSIONS: MA showed a high specificity and sensitivity in etiological diagnosis of IE. Molecular antibiogram could overcome the major limitation of MA that is the lack of susceptibility testing. We advocate for the inclusion of MA among diagnostic criteria for IE and for a more extensive use of molecular antibiogram when the culture result is negative, and MA is the only positive test.

Sarocladium and Acremonium infections: New faces of an old opportunistic fungus.

The genera Acremonium and Sarocladium comprise a high diversity of morphologically and genetically related fungi generally found in the environment, although a few species, mainly Sarocladium kiliense and Acremonium egyptiacum, can also be involved in many human infections. Clinical management of opportunistic infections caused by these fungi is very complex, since their correct identification is unreliable, and they generally show poor antifungal response. More than 300 clinical cases involving a broad range of Acremonium/Sarocladium infections have so far been published, and with this review we aim to compile and provide a detailed overview of the current knowledge on Acremonium/Sarocladium human infections in terms of presentation, diagnosis, treatments and prognoses. We also aim to summarise and discuss the data currently available on their antifungal susceptibility, emphasising the promising results obtained with voriconazole as well as their impact in terms of animal infections.

The First Report of Calcified Amorphous Tumor Associated with Infective Endocarditis: A Case Report and Review of Literature.

BACKGROUND Calcified amorphous tumor (CAT) of the heart is a rare non-neoplastic intracardiac mass, which is composed of calcium deposition surrounded by amorphous fibrous tissue. The clinical presentation of cardiac CAT resembles that of other cardiac tumors or vegetation, though there is no previous report of a CAT complicated with infective endocarditis. CASE REPORT A 67-year-old male with a history of end stage renal failure and gastric cancer who was on adjuvant chemotherapy presented with a cardiac mass. The mass was resected and diagnosed as CAT pathologically. Two separate sets of blood cultures were positive for Enterococcus faecalis, thus, the patient was diagnosed with infective endocarditis. Antibiotic treatment was continued for 6 weeks after surgery, and the patient recovered uneventfully. However, he died from a complication of his gastric cancer 5 months later. CONCLUSIONS This is the first report of CAT associated with infective endocarditis. Blood cultures should be obtained to differentiate infective endocarditis or CAT with infectious endocarditis from CAT alone, because CAT with infective endocarditis may present atypically and may be more likely to require antibiotic treatment along with surgery.

Microbial biofilm correlates with an increased antibiotic tolerance and poor therapeutic outcome in infective endocarditis.

BACKGROUND: Infective endocarditis (IE) is associated with high rates of mortality. Prolonged treatments with high-dose intravenous antibiotics often fail to eradicate the infection, frequently leading to high-risk surgical intervention. By providing a mechanism of antibiotic tolerance, which escapes conventional antibiotic susceptibility profiling, microbial biofilm represents a key diagnostic and therapeutic challenge for clinicians. This study aims at assessing a rapid biofilm identification assay and a targeted antimicrobial susceptibility profile of biofilm-growing bacteria in patients with IE, which were unresponsive to antibiotic therapy. RESULTS: Staphylococcus aureus was the most common isolate (50%), followed by Enterococcus faecalis (25%) and Streptococcus gallolyticus (25%). All microbial isolates were found to be capable of producing large, structured biofilms in vitro. As expected, antibiotic treatment either administered on the basis of antibiogram or chosen empirically among those considered first-line antibiotics for IE, including ceftriaxone, daptomycin, tigecycline and vancomycin, was not effective at eradicating biofilm-growing bacteria. Conversely, antimicrobial susceptibility profile of biofilm-growing bacteria indicated that teicoplanin, oxacillin and fusidic acid were most effective against S. aureus biofilm, while ampicillin was the most active against S. gallolyticus and E. faecalis biofilm, respectively. CONCLUSIONS: This study indicates that biofilm-producing bacteria, from surgically treated IE, display a high tolerance to antibiotics, which is undetected by conventional antibiograms. The rapid identification and antimicrobial tolerance profiling of biofilm-growing bacteria in IE can provide key information for both antimicrobial therapy and prevention strategies.

Acquisition of FKS2 mutation after echinocandin treatment of infective endocarditis by Candida glabrata.

Bloodstream infections caused by non-albicans Candida species are increasing and echinocandins have been extensively used especially in patients with hemodynamic instability, previous antifungal treatment and hospital risk factors for intrinsic or acquired resistance to azoles. Candida glabrata resistance to echinocandins is reported and is generally associated with previous use of echinocandins; FKS gene mutations have been associated with a worse outcome. We report the case of a 65-year-old woman who developed candidemia and endocarditis by C. glabrata with a newly acquired FKS mutation 24 months after successful treatment of infective endocarditis by C. glabrata with a double dosage of anidulafungin (200 mg daily) followed by oral voriconazole. Driven by high echinocandin MICs the strain taken by intraoperative cultures was further analyzed in a referral microbiology laboratory, confirming the new onset of point mutation S633P of the FKS2 gene.

Successful treatment with daptomycin and ceftaroline of MDR Staphylococcus aureus native valve endocarditis: a case report.

OBJECTIVES: The best therapeutic approach for treating MRSA endocarditis remains unknown, particularly in cases of high vancomycin MICs. We report here a case of daptomycin-non-susceptible, ceftaroline-resistant and fosfomycin-resistant MRSA native left valve endocarditis that was successfully treated with valve repair and a combination of high-dose daptomycin and ceftaroline. METHODS: Antimicrobial testing of the clinical strain was performed using Etest and microdilution broth methods. Time-kill and chequerboard methodologies were used to test the activity of antibiotic combinations. RESULTS: By Etest, the MIC of vancomycin was 2 mg/L, the MIC of daptomycin was 2 mg/L, the MIC of fosfomycin was 1024 mg/L and the MIC of ceftaroline was 1.5 mg/L. At the standard inoculum (105 cfu/mL), the three combinations of daptomycin plus ceftaroline, cloxacillin or fosfomycin were synergistic and bactericidal. However, when these combinations were tested using a higher inoculum (108 cfu/mL), all combinations were synergistic, but only daptomycin plus ceftaroline had bactericidal activity. CONCLUSIONS: These results confirmed a synergistic effect between daptomycin plus ceftaroline and increased bactericidal activity against MRSA, suggesting that this combination may be effective for the treatment of invasive MRSA infection. Our experience highlights the potential clinical use of synergy testing to guide difficult treatment decisions in patients with MDR MRSA infection.

Emergence of a dalbavancin induced glycopeptide/lipoglycopeptide non-susceptible Staphylococcus aureus during treatment of a cardiac device-related endocarditis.

In the present study, we demonstrated the emergence of dalbavancin non-susceptible and teicoplanin-resistant Staphylococcus aureus small colony variants which were selected in vivo through long-term treatment with dalbavancin. A 36-year-old man presented with a cardiac device-related S. aureus endocarditis and received long-term therapy with dalbavancin. Consecutively, two glycopeptide/lipoglycopeptide susceptible and two non-susceptible S. aureus isolates were obtained from blood cultures and the explanted pacemaker wire. The isolates were characterized by: standard typing methods, antimicrobial susceptibility testing, auxotrophic profiling, proliferation assays, scanning and transmission electron microscopy, as well as whole genome sequencing. The isolated SCVs demonstrated a vancomycin-susceptible but dalbavancin non-susceptible and teicoplanin-resistant phenotype whereof the respective MICs of the last isolate were 16- and 84-fold higher than the susceptible strains. All four strains were indistinguishable or at least closely related by standard typing methods (spa, MLST, and PFGE), and whole genome sequencing revealed only eight sequence variants. A consecutive increase in cell wall thickness (up to 2.1-fold), an impaired cell separation with incomplete or multiple cross walls and significantly reduced growth rates were observed in the present study. Therefore, the mutations in pbp2 and the DHH domain of GdpP were identified as the most probable candidates due to their implication in the biosynthesis and metabolism of the staphylococcal cell wall. For the first time, we demonstrated in vivo induced dalbavancin non-susceptible/teicoplanin resistant, but vancomycin and daptomycin susceptible S. aureus SCVs without lipopeptide or glycopeptide pretreatment, thus, indicating the emergence of a novel lipoglycopeptide resistance mechanism.

Hypoprothrombinemia and severe perioperative haemorrhagic complications in cardiac surgery patients treated with high-dose cefazolin for infective endocarditis.

Endocarditis is a serious and common disease that requires prolonged antimicrobial therapy. The recent shortage of oxacillin has led to the use of other antimicrobial agents such as cefazolin to treat endocarditis due to methicillin-sensitive Staphylococcus aureus. We describe four cases of life-threatening haemorrhagic complications (fatal in two cases) in patients treated with high-dose cefazolin. All of these patients with major bleeding presented with hypoprothrombinemia secondary to hypovitaminosis K. This adverse event may be due to inhibition of vitamin K epoxide reductase and/or gamma-glutamyl-carboxylase by the 2-methyl-1,2,3-thiadiazol-5-thiol group of cefazolin. This inhibition may result in hypoprothrombinemia by altering the synthesis of vitamin K-dependent coagulation factors. The increasing use of cefazolin, especially at a high dose and for a prolonged period of time, should be accompanied by regular monitoring of coagulation, including prothrombin index, and vitamin K supplementation.

AtlA Mediates Extracellular DNA Release, Which Contributes to Streptococcus mutans Biofilm Formation in an Experimental Rat Model of Infective Endocarditis.

Host factors, such as platelets, have been shown to enhance biofilm formation by oral commensal streptococci, inducing infective endocarditis (IE), but how bacterial components contribute to biofilm formation in vivo is still not clear. We demonstrated previously that an isogenic mutant strain of Streptococcus mutans deficient in autolysin AtlA (ΔatlA) showed a reduced ability to cause vegetation in a rat model of bacterial endocarditis. However, the role of AtlA in bacterial biofilm formation is unclear. In this study, confocal laser scanning microscopy analysis showed that extracellular DNA (eDNA) was embedded in S. mutans GS5 floes during biofilm formation on damaged heart valves, but an ΔatlA strain could not form bacterial aggregates. Semiquantification of eDNA by PCR with bacterial 16S rRNA primers demonstrated that the ΔatlA mutant strain produced dramatically less eDNA than the wild type. Similar results were observed with in vitro biofilm models. The addition of polyanethol sulfonate, a chemical lysis inhibitor, revealed that eDNA release mediated by bacterial cell lysis is required for biofilm initiation and maturation in the wild-type strain. Supplementation of cultures with calcium ions reduced wild-type growth but increased eDNA release and biofilm mass. The effect of calcium ions on biofilm formation was abolished in ΔatlA cultures and by the addition of polyanethol sulfonate. The VicK sensor, but not CiaH, was found to be required for the induction of eDNA release or the stimulation of biofilm formation by calcium ions. These data suggest that calcium ion-regulated AtlA maturation mediates the release of eDNA by S. mutans, which contributes to biofilm formation in infective endocarditis.

Efficacy of Ceftaroline against Methicillin-Susceptible Staphylococcus aureus Exhibiting the Cefazolin High-Inoculum Effect in a Rat Model of Endocarditis.

Certain Staphylococcus aureus strains exhibit an inoculum effect (InE) with cefazolin (CFZ) that has been associated with therapeutic failures in high-inoculum infections. We assessed the in vitro activities of ceftaroline (CPT), CFZ, and nafcillin (NAF) against 17 type A ß-lactamase (ßla)-producing, methicillin-susceptible S. aureus (MSSA) strains, including the previously reported TX0117, which exhibits the CFZ InE, and its ßla-cured derivative, TX0117c. Additionally, we determined the pharmacokinetics of CPT in rats after single intramuscular doses of 20 and 40 mg/kg of body weight and evaluated the activities of CPT (40 mg/kg every 8 h [q8h]), CFZ, and NAF against TX0117 and TX0117c in a rat model of infective endocarditis. No InE was observed for CPT or NAF, whereas a marked InE was detected for CFZ (MIC, 8 to ≥128 µg/ml). CPT and NAF treatment against TX0117 resulted in mean bacterial counts of 2.3 and 2.1 log10 CFU/g in vegetations, respectively, compared to a mean of 5.9 log10 CFU/g in the CFZ-treated group (CPT and NAF versus CFZ, P = 0.001; CPT versus NAF, P = 0.9830). Both CFZ and CPT were efficacious against the ßla-cured derivative, TX0117c, compared to time zero (t0) (P = <0.0001 and 0.0015, respectively). Our data reiterate the in vivo consequences of the CFZ InE and show that CPT is not affected by this phenomenon. CPT might be considered for high-inoculum infections caused by MSSA exhibiting the CFZ InE.

Synergistic Interaction Between Phage Therapy and Antibiotics Clears Pseudomonas Aeruginosa Infection in Endocarditis and Reduces Virulence.

Background: Increasing antibiotic resistance warrants therapeutic alternatives. Here we investigated the efficacy of bacteriophage-therapy (phage) alone or combined with antibiotics against experimental endocarditis (EE) due to Pseudomonas aeruginosa, an archetype of difficult-to-treat infection. Methods: In vitro fibrin clots and rats with aortic EE were treated with an antipseudomonas phage cocktail alone or combined with ciprofloxacin. Phage pharmacology, therapeutic efficacy, and resistance were determined. Results: In vitro, single-dose phage therapy killed 7 log colony-forming units (CFUs)/g of fibrin clots in 6 hours. Phage-resistant mutants regrew after 24 hours but were prevented by combination with ciprofloxacin (2.5 × minimum inhibitory concentration). In vivo, single-dose phage therapy killed 2.5 log CFUs/g of vegetations in 6 hours (P < .001 vs untreated controls) and was comparable with ciprofloxacin monotherapy. Moreover, phage/ciprofloxacin combinations were highly synergistic, killing >6 log CFUs/g of vegetations in 6 hours and successfully treating 64% (n = 7/11) of rats. Phage-resistant mutants emerged in vitro but not in vivo, most likely because resistant mutations affected bacterial surface determinants important for infectivity (eg, the pilT and galU genes involved in pilus motility and LPS formation). Conclusions: Single-dose phage therapy was active against P. aeruginosa EE and highly synergistic with ciprofloxacin. Phage-resistant mutants had impaired infectivity. Phage-therapy alone or combined with antibiotics merits further clinical consideration.

Comparative healthcare-associated costs of methicillin-resistant Staphylococcus aureus bacteraemia-infective endocarditis treated with either daptomycin or vancomycin.

Complex infection with methicillin-resistant Staphylococcus aureus (MRSA) is associated with high healthcare and societal costs; thus, evaluation of the costs and health benefits of interventions is an important consideration in a modern healthcare system. This study estimated the cost consequences of the use of daptomycin compared with vancomycin for the first-line treatment of patients with proven MRSA-induced bacteraemia-infective endocarditis (SAB-IE) with a vancomycin minimum inhibitory concentration (MIC) >1mg/L in the UK. A decision model was developed to assess total healthcare costs of treatment, including inpatient, outpatient and drug costs. Data were sourced from the literature (treatment efficacy and safety), a physician survey (resource use) and publicly available databases (unit costs). Assuming the same length of stay for daptomycin and vancomycin, the total healthcare costs per patient were £17917 for daptomycin and £17165 for vancomycin. However, extrapolating from published studies and supported by a physician survey, daptomycin was found to require fewer therapeutic switches and a shorter length of stay. When the length of stay was reduced from 42 days to 28 days, daptomycin saved £4037 per person compared with vancomycin. In conclusion, daptomycin is an effective and efficient alternative antibiotic for the treatment of SAB-IE. However, the level of cost saving depends on the extent to which local clinical practice allows early discharge of patients before the end of their antibiotic course when responding to treatment.

[Endocarditis and arthritis caused by extended spectrum ß-lactamase-producing non-Typhi Salmonella]. / Endocarditis y artritis séptica por Salmonella no Typhi productora de ß-lactamasas de espectro extendido: A case report.

We present the case of a patient with endocarditis and arthritis caused by extended spectrum ß-lactamase producing non-Typhi Salmonella, with incomplete response (defined as persistence of Salmonella in joint fluid) to initial instituted treatment (trimethoprim-sulfamethoxazole) and posterior recovery with ertapenem. The disease was associated with implantable central venous catheter infection. Five percent of patients with non-Typhi Salmonella gastroenteritis develop bacteremia. Infective endocarditis and joint infection has been reported in 1,4% and less than 1% of cases, respectively.

Endocarditis y artritis séptica por Salmonella no Typhi productora de β-lactamasas de espectro extendido: A case report / Endocarditis and arthritis caused by extended spectrum β-lactamase-producing non-Typhi Salmonella

We present the case of a patient with endocarditis and arthritis caused by extended spectrum β-lactamase producing non-Typhi Salmonella, with incomplete response (defined as persistence of Salmonella in joint fluid) to initial instituted treatment (trimethoprim-sulfamethoxazole) and posterior recovery with ertapenem. The disease was associated with implantable central venous catheter infection. Five percent of patients with non-Typhi Salmonella gastroenteritis develop bacteremia. Infective endocarditis and joint infection has been reported in 1,4% and less than 1% of cases, respectively.

Se presenta el caso de un paciente con endocarditis y artritis séptica por Salmonella no Typhi productora de β-lactamasas de espectro extendido que presentó una respuesta incompleta (definida como la persistencia de Salmonella en el líquido articular) al tratamiento inicial con cotrimoxazol y que posteriormente mejoró con ertapenem. La enfermedad se asoció al uso de un catéter venoso implantable. El 5% de los pacientes con gastroenteritis por Salmonella no Typhi desarrolla una bacteriemia. La endocarditis infecciosa y la artritis ha sido reportada en 1,4-5% de los casos y en menos de 1%; respectivamente.