Clinical presentation of infective endocarditis caused by different groups of non-beta haemolytic streptococci

Treatment of Complicated Gram-Positive Bacteremia and Infective Endocarditis

The Gram-positive cocci Staphylococcus aureus, Streptococcus spp., and Enterococcus spp. are the most frequent causative organisms of bloodstream infections and infective endocarditis. "Complicated bacteremia" is a term used in S. aureus bloodstream infections and originally implied the presence of metastatic infectious foci (i.e. complications of S. aureus bacteremia). These complications demand longer antimicrobial treatment durations and, frequently, interventional source control. Several risk factors for the incidence of bacteremia complications have been identified and are often used for the definition of complicated bacteremia. Here, we discuss management and diagnostic approaches and treatment options for patients with complicated bacteremia, with particular focus on infective endocarditis. We also summarize the available evidence regarding imaging modalities and the choice of antimicrobial mono- or combination therapy according to resistance patterns for these pathogens as well as treatment durations and optimized application routes. Finally, we synopsize current and future areas of research in complicated bacteremia and infective endocarditis.

Clinicomicrobiological risk factors for infective endocarditis in viridans group streptococci bacteraemia

BACKGROUND

When to perform echocardiography to rule out infective endocarditis (IE) in patients with viridans group streptococci (VGS) bloodstream infections (BSIs) is unclear.

OBJECTIVES

We aimed to identify independent risk factors for IE in patients with VGS BSI.

METHODS

This retrospective study conducted at Seoul National University Hospital from January 2013 to December 2022 involved patients with VGS and nutritionally variant streptococcal BSI, excluding single positive blood cultures and polymicrobial BSI cases. Independent risk factors were identified by multivariate logistic regression and sensitivity analyses according to echocardiography results, VGS species or the inclusion of possible IE cases.

RESULTS

Of 845 VGS BSI cases, 349 were analysed and 86 IE cases were identified (24.6%). In the multivariate analysis, heart valve disease [adjusted odds ratio (aOR), 14.14, 95% CI, 6.14-32.58; P < 0.001], persistent bacteraemia (aOR, 5.12, 95% CI, 2.03-12.94; P = 0.001), age (per year, aOR, 0.98; 95% CI, 0.96-1.00; P = 0.015), solid cancer (aOR, 0.26; 95% CI, 0.13-0.53; P < 0.001) and haematologic malignancy (aOR, 0.04; 95% CI, 0.01-0.41; P = 0.006) were independently associated with IE. Sensitivity analyses yielded consistent results; also, infection by a member of the mitis group was independent risk factor for IE (aOR, 6.50; 95% CI, 2.87-14.68; P < 0.001).

CONCLUSIONS

Younger age, heart valve disease, persistent bacteraemia, absence of underlying malignancy and BSI by a member of the mitis group were independent risk factors for IE in patients with VGS BSI. Echocardiographic evaluation could be prudently considered based on these clinicomicrobiological risk factors.

Infective endocarditis is rare in patients with hematologic malignancy and neutropenia

BACKGROUND

Infective endocarditis (IE) is a serious complication of bloodstream infections (BSIs) that occurs at variable rates depending on the pathogen and clinical setting. There is a paucity of data describing the risk of IE in patients with hematologic malignancy who develop bacteremia while neutropenic.

METHODS

Adult patients on the hematology ward from January 2018 to December 2020 with hematologic malignancy and bacteremia were evaluated retrospectively for endocarditis by applying the 2023 Duke-ISCVID criteria. Charts of possible cases were evaluated 90 days after the initial BSI for new infectious complications that could indicate missed IE. Descriptive statistics compared patients admitted for hematopoietic stem cell transplantation (HSCT) to those admitted for alternative reasons (non-HSCT).

RESULTS

Among the 1005 positive blood cultures initially identified, there were 66 episodes in 65 patients with hematologic malignancy and at least grade 3 neutropenia for a mean duration of 11.4 days during their admission. Transthoracic echocardiography (TTE) was performed in 34.8% of BSIs, and transesophageal echocardiography (TEE) in 6.1%. There were no new infectious complications in possible cases 90 days after their initial BSI. No cases of endocarditis were identified.

CONCLUSIONS

Endocarditis is rare amongst patients with hematologic malignancy, bacteremia, and neutropenia, and no cases were identified in this cohort. The use of routine TTE in this setting seems unwarranted, and the addition of TEE is unlikely to improve patient-centered outcomes.

Risk and Outcome of Infective Endocarditis in Streptococcal Bloodstream Infections according to Streptococcal Species

This study aimed to identify which streptococcal species are closely associated with infective endocarditis (IE) and to evaluate risk factors for mortality in patients with streptococcal IE. We performed a retrospective cohort study of all patients with streptococcal bloodstream infection (BSI) from January 2010 to June 2020 in a tertiary hospital in South Korea. We compared clinical and microbiological characteristics of streptococcal BSIs according to the diagnosis of IE. We performed multivariate analysis to evaluate the risk of IE according to streptococcal species and risk factors for mortality in streptococcal IE. A total of 2,737 patients were identified during the study period, and 174 (6.4%) were diagnosed with IE. The highest IE prevalence was in patients with Streptococcus mutans BSI (33% [9/27]) followed by S. sanguinis (31% [20/64]), S. gordonii (23% [5/22]), S. gallolyticus (16% [12/77]), and S. oralis (12% [14/115]). In multivariate analysis, previous IE, high-grade BSI, native valve disease, prosthetic valve, congenital heart disease, and community-onset BSI were independent risk factors for IE. After adjusting for these factors, S. sanguinis (adjusted OR [aOR], 7.75), S. mutans (aOR, 5.50), and S. gallolyticus (aOR, 2.57) were significantly associated with higher risk of IE, whereas S. pneumoniae (aOR, 0.23) and S. constellatus (aOR, 0.37) were associated with lower risk of IE. Age, hospital-acquired BSI, ischemic heart disease, and chronic kidney disease were independent risk factors for mortality in streptococcal IE. Our study points to significant differences in the prevalence of IE in streptococcal BSI according to species. IMPORTANCE Our study of risk of infective endocarditis in patients with streptococcal bloodstream infection demonstrated that Streptococcus sanguinis, S. mutans, and S. gallolyticus were significantly associated with higher risk of infective endocarditis. However, when we evaluated the performance of echocardiography in patients with streptococcal bloodstream infection, patients with S. mutans and S. gordonii bloodstream infection had a tendency of low performance in echocardiography. There are significant differences in the prevalence of infective endocarditis in streptococcal bloodstream infection according to species. Therefore, performing echocardiography in streptococcal bloodstream infection with a high prevalence of, and significant association with, infective endocarditis is desirable.

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.

Streptococcal infective endocarditis: clinical features and outcomes according to species

PURPOSE

Infective endocarditis (IE) is frequently caused by streptococcal species, yet clinical features and mortality are poorly investigated. Our aim was to examine patients with streptococcal IE to describe clinical features and outcomes according to streptococcal species.

METHODS

From 2002 to 2012, we investigated patients with IE admitted to two tertiary Danish heart centres. Adult patients with left-sided streptococcal IE were included. Adjusted multivariable logistic regression analyses were performed, to assess the association between streptococcal species and heart valve surgery or 1-year mortality.

RESULTS

Among 915 patients with IE, 284 (31%) patients with streptococcal IE were included [mean age 63.5 years (SD 14.1), 69% men]. The most frequent species were S. mitis/oralis (21%) and S. gallolyticus (17%). Fever (86%) and heart murmur (81%) were common symptoms, while dyspnoea was observed in 46%. Further, 18% of all cases were complicated by a cardiac abscess/pseudoaneurysm and 25% by an embolic event. Heart valve surgery during admission was performed in 55% of all patients, and S. gallolyticus (OR 0.28 [95% CI 0.11-0.69]) was associated with less surgery compared with S. mitis/oralis. In-hospital mortality was 7% and 1-year mortality 15%, without any difference between species.

CONCLUSION

S. mitis/oralis and S. gallolyticus were the most frequent streptococcal species causing IE. Further, S. gallolyticus IE was associated with less heart valve surgery during admission compared with S. mitis/oralis IE. Being aware of specific symptoms, clinical findings, and complications related to different streptococcal species, may help the clinicians in expecting different outcomes.

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.

Emphysematous cystitis due to Streptococcus salivarius infection in a patient with a neurogenic bladder

Streptococcus salivarius (S. salivarius) is an oral commensal bacterium that rarely causes disease. Here, we report a case of emphysematous cystitis due to S. salivarius infection in a patient with a neurogenic bladder. A 56-year-old woman was hospitalized and managed for left putamen hemorrhage. Afterward, she developed poor oral intake. Although the patient was afebrile, laboratory test results suggested an inflammatory response. Urinalysis revealed pyuria and hematuria. Abdominal computed tomography revealed a thickened urinary bladder wall and intraluminal gas. Additionally, she was diagnosed with a neurogenic bladder as she had approximately 200 mL of residual urine. The patient was diagnosed with emphysematous cystitis, and S. salivarius was isolated from urine culture specimens. The patient's condition improved immediately after treatment, which included bladder drainage and administration of appropriate antibiotics. We could not find any report on S. salivarius causing urinary tract infections, such as emphysematous cystitis. Accordingly, we report this case along with a review of the literature.

Surgery Is Underused in Elderly Patients With Left-Sided Infective Endocarditis: A Nationwide Registry Study

Background

Infective endocarditis is associated with higher mortality in elderly patients, but the role of surgery in this group has not been fully evaluated. The aim of this study was to assess outcomes of left‐sided infective endocarditis in elderly patients and to determine the influence of surgery on mortality in the elderly.

Methods and Results

A nationwide retrospective study was performed of 2186 patients with left‐sided infective endocarditis recorded in the SRIE (Swedish Registry of Infective Endocarditis), divided into patients aged <65 years (n=864), 65 to 79 years (n=806), and ≥80 years (n=516). Survival analysis was performed using the Swedish National Population Registry, and propensity score matching was applied to assess the effect of surgery on survival among patients of all ages. The rate of surgery decreased with increasing age, from 46% in the <65 group to 6% in the ≥80 group. In‐hospital mortality was 3 times higher in the ≥80 group compared with the <65 group (23% versus 7%) and almost twice that of the 65 to 79 group (12%). In propensity‐matched groups, the mortality rate was significantly lower between the ages of 55 and 82 years in patients who underwent surgery compared with patients who did not undergo surgery. Surgery was also associated with better long‐term survival in matched patients who were ≥75 years (hazard ratio, 0.36; 95% CI, 0.24–0.54 [P<0.001]).

Conclusions

The proportion of elderly patients with infective endocarditis who underwent surgery was low compared with that of younger patients. Surgery was associated with lower mortality irrespective of age. In matched elderly patients, long‐term mortality was higher in patients who did not undergo surgery, suggesting that surgery is underused in elderly patients.

Proposal for the use of echocardiography in bloodstream infections due to different streptococcal species

Background

Infective endocarditis (IE) is diagnosed in 7–8% of streptococcal bloodstream infections (BSIs), yet it is unclear when to perform transthoracic (TTE) and transoesophageal echocardiography (TOE) according to different streptococcal species. The aim of this sub-study was to propose a flowchart for the use of echocardiography in streptococcal BSIs.

Methods

In a population-based setup, we investigated all patients admitted with streptococcal BSIs and crosslinked data with nationwide registries to identify comorbidities and concomitant hospitalization with IE. Streptococcal species were divided in four groups based on the crude risk of being diagnosed with IE (low-risk < 3%, moderate-risk 3–10%, high-risk 10–30% and very high-risk > 30%). Based on number of positive blood culture (BC) bottles and IE risk factors (prosthetic valve, previous IE, native valve disease, and cardiac device), we further stratified cases according to probability of concomitant IE diagnosis to create a flowchart suggesting TTE plus TOE (IE > 10%), TTE (IE 3–10%), or “wait & see” (IE < 3%).

Results

We included 6393 cases with streptococcal BSIs (mean age 68.1 years [SD 16.2], 52.8% men). BSIs with low-risk streptococci (S. pneumoniae, S. pyogenes, S. intermedius) are not initially recommended echocardiography, unless they have ≥3 positive BC bottles and an IE risk factor. Moderate-risk streptococci (S. agalactiae, S. anginosus, S. constellatus, S. dysgalactiae, S. salivarius, S. thermophilus) are guided to “wait & see” strategy if they neither have a risk factor nor ≥3 positive BC bottles, while a TTE is recommended if they have either ≥3 positive BC bottles or a risk factor. Further, a TTE and TOE are recommended if they present with both. High-risk streptococci (S. mitis/oralis, S. parasanguinis, G. adiacens) are directed to a TTE if they neither have a risk factor nor ≥3 positive BC bottles, but to TTE and TOE if they have either ≥3 positive BC bottles or a risk factor. Very high-risk streptococci (S. gordonii, S. gallolyticus, S. mutans, S. sanguinis) are guided directly to TTE and TOE due to a high baseline IE prevalence.

Conclusion

In addition to the clinical picture, this flowchart based on streptococcal species, number of positive blood culture bottles, and risk factors, can help guide the use of echocardiography in streptococcal bloodstream infections. Since echocardiography results are not available the findings should be confirmed prospectively with the use of systematic echocardiography.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12879-021-06391-2.

Detection of Streptococcus mutans in symptomatic and asymptomatic infected root canals

OBJECTIVES

To investigate the presence of Streptococcus mutans in root canals of symptomatic necrotic teeth (SNT) and their associated acute apical abscesses (AAA) and in the root canals of asymptomatic necrotic teeth (ANT). It also aimed to investigate the presence of the cnm and cbm genes in specimens that harbored S. mutans.

MATERIALS AND METHODS

DNA was extracted from samples collected from 10 patients presenting pulpal necrosis associated with radiographic evidence of apical periodontitis (ANT) and from 10 patients in need of endodontic therapy due to the presence of pulpal necrosis (SNT) and AAA. The control group consisted of 10 patients with teeth with normal vital pulp and requiring endodontic treatment for prosthetic reasons. The presence of S. mutans was detected by quantitative real-time-PCR (qPCR) using species-specific primers. Samples harboring S. mutans were further evaluated for the presence of CBP genes by qPCR as well.

RESULTS

All studied sites showed a high prevalence of S. mutans, except the control group. Specifically, 60% of ANT and 70% of AAA/SNT paired samples were positive for S. mutans. The cnm gene was detected positive for S. mutans only in ANT samples (66.6%). The cbm gene was not detected in any of the investigated sites.

CONCLUSIONS

S. mutans was found in high prevalence in both asymptomatic and symptomatic endodontic infections, including in abscesses, but it was not detected in the root canals of teeth with normal vital pulp. Interestingly, cnm+ S. mutans was only detected in asymptomatic/chronic primary endodontic infections associated with apical lesion. Therefore, it appears that cnm, and possibly other CBPs, may play an underestimated role in chronic endodontic infections.

CLINICAL RELEVANCE

A high prevalence of Streptococcus mutans cnm+ gene was detected only in asymptomatic primary endodontic infections associated with apical lesion. Therefore, it appears that this collagen-binding protein gene plays an underestimated role in asymptomatic/chronic endodontic infections.

Clinical Features and Outcomes of Streptococcus anginosus Group Infective Endocarditis: A Multicenter Matched Cohort Study

Background

Although Streptococcus anginosus group (SAG) endocarditis is considered a severe disease associated with abscess formation and embolic events, there is limited evidence to support this assumption.

Methods

We performed a retrospective analysis of prospectively collected data from consecutive patients with definite SAG endocarditis in 28 centers in Spain and Italy. A comparison between cases due to SAG endocarditis and viridans group streptococci (VGS) or Streptococcus gallolyticus group (SGG) was performed in a 1:2 matched analysis.

Results

Of 5336 consecutive cases of definite endocarditis, 72 (1.4%) were due to SAG and matched with 144 cases due to VGS/SGG. SAG endocarditis was community acquired in 64 (88.9%) cases and affected aortic native valve in 29 (40.3%). When comparing SAG and VGS/SGG endocarditis, no significant differences were found in septic shock (8.3% vs 3.5%, P = .116); valve disorder, including perforation (22.2% vs 18.1%, P = .584), pseudoaneurysm (16.7% vs 8.3%, P = .108), or prosthesis dehiscence (1.4% vs 6.3%, P = .170); paravalvular complications, including abscess (25% vs 18.8%, P = .264) and intracardiac fistula (5.6% vs 3.5%, P = .485); heart failure (34.7% vs 38.9%, P = .655); or embolic events (41.7% vs 32.6%, P = .248). Indications for surgery (70.8% vs 70.8%; P = 1) and mortality (13.9% vs 16.7%; P = .741) were similar between groups.

Conclusions

SAG endocarditis is an infrequent but serious condition that presents a prognosis similar to that of VGS/SGG.

Capnocytophaga canimorsus tricuspid valve endocarditis

Capnocytophaga canimorsus is an uncommon cause of infective endocarditis (IE) and mainly affects persons with compromised immune-systems who have been in contact with dogs. We describe a case of C. canimorsus tricuspid valve IE in a 70 year-old dog-owner where diagnosis and treatment were delayed. The reason for the delayed diagnosis in this case was likely due to that initial blood cultures were negative due to preceding antibiotic treatment, discrepancies between echocardiographic investigations, and a thymoma and colonic polyps which were thought to explain the symptoms. A multi-diciplinary approach in cases with suspected IE might help to avoid diagnostic delays.

Infective Endocarditis Due to Corynebacterium Species: Clinical Features and Antibiotic Resistance

Background

Corynebacterium species are often dismissed as contaminants in blood cultures, but they can also cause infective endocarditis (IE), which is a severe condition. Antibiotic resistance of corynebacteria is increasing making treatment challenging. Reports on IE caused by Corynebacterium species are scarce and more knowledge is needed.

Methods

Cases of IE caused by Corynebacterium species were identified through the Swedish Registry of Infective Endocarditis. Isolates were collected for species redetermination by matrix-assisted laser desorption ionization-time of flight and for antibiotic susceptibility testing using Etests.

Results

Thirty episodes of IE due to Corynebacterium species were identified between 2008 and 2017. The median age of patients was 71 years (interquartile range, 60–76) and 77% were male. Corynebacterium striatum (n = 11) was the most common IE causing pathogen followed by Corynebacterium jeikeium (n = 5). Surgery was performed in 50% and in-hospital mortality rate was 13%. Patients with IE caused by Corynebacterium species were significantly more likely to have prosthetic valve endocarditis (70%), compared with patients with IE due to Staphylococcus aureus or non-beta-hemolytic streptococci (14% and 26%, respectively) (P < .0001). Vancomycin was active towards all Corynebacterium isolates, whereas resistance towards penicillin G was common.

Conclusions

Corynebacterium species cause IE, where prosthetic valves are mainly affected and surgery is often performed. Corynebacterium striatum is an important causative agent of IE within the genus. Antibiotic resistance of corynebacteria is relatively common but resistance towards vancomycin could not be detected in vitro.

Structure based virtual screening identifies small molecule effectors for the sialoglycan binding protein Hsa

Infective endocarditis (IE) is a cardiovascular disease often caused by bacteria of the viridans group of streptococci, which includes Streptococcus gordonii and Streptococcus sanguinis. Previous research has found that serine-rich repeat (SRR) proteins on the S. gordonii bacterial surface play a critical role in pathogenesis by facilitating bacterial attachment to sialylated glycans displayed on human platelets. Despite their important role in disease progression, there are currently no anti-adhesive drugs available on the market. Here, we performed structure-based virtual screening using an ensemble docking approach followed by consensus scoring to identify novel small molecule effectors against the sialoglycan binding domain of the SRR adhesin protein Hsa from the S. gordonii strain DL1. The screening successfully predicted nine compounds which were able to displace the native ligand (sialyl-T antigen) in an in vitro assay and bind competitively to Hsa. Furthermore, hierarchical clustering based on the MACCS fingerprints showed that eight of these small molecules do not share a common scaffold with the native ligand. This study indicates that SRR family of adhesin proteins can be inhibited by diverse small molecules and thus prevent the interaction of the protein with the sialoglycans. This opens new avenues for discovering potential drugs against IE.

Prevalence of Infective Endocarditis in Streptococcal Bloodstream Infections Is Dependent on Streptococcal Species

BACKGROUND

Streptococci frequently cause infective endocarditis (IE), yet the prevalence of IE in patients with bloodstream infections (BSIs) caused by different streptococcal species is unknown. We aimed to investigate the prevalence of IE at species level in patients with streptococcal BSIs.

METHODS

We investigated all patients with streptococcal BSIs, from 2008 to 2017, in the Capital Region of Denmark. Data were crosslinked with Danish nationwide registries for identification of concomitant hospitalization with IE. In a multivariable logistic regression analysis, we investigated the risk of IE according to streptococcal species adjusted for age, sex, ≥3 positive blood culture bottles, native valve disease, prosthetic valve, previous IE, and cardiac device.

RESULTS

Among 6506 cases with streptococcal BSIs (mean age 68.1 years [SD 16.2], 52.8% men) the IE prevalence was 7.1% (95% CI, 6.5-7.8). The lowest IE prevalence was found with Streptococcus pneumoniae (S pneumoniae) 1.2% (0.8-1.6) and Spyogenes 1.9% (0.9-3.3). An intermediary IE prevalence was found with Sanginosus 4.8% (3.0-7.3), Ssalivarius 5.8% (2.9-10.1), and Sagalactiae 9.1% (6.6-12.1). The highest IE prevalence was found with Smitis/oralis 19.4% (15.6-23.5), Sgallolyticus (formerly Sbovis) 30.2% (24.3-36.7), Ssanguinis 34.6% (26.6-43.3), Sgordonii 44.2% (34.0-54.8), and Smutans 47.9% (33.3-62.8). In multivariable analysis using S pneumoniae as reference, all species except S pyogenes were associated with significantly higher IE risk, with the highest risk found with S gallolyticus odds ratio (OR) 31.0 (18.8-51.1), S mitis/oralis OR 31.6 (19.8-50.5), S sanguinis OR 59.1 (32.6-107), S gordonii OR 80.8 (43.9-149), and S mutans OR 81.3 (37.6-176).

CONCLUSIONS

The prevalence of IE in streptococcal BSIs is species dependent with S mutans, S gordonii, S sanguinis, S gallolyticus, and S mitis/oralis having the highest IE prevalence and the highest associated IE risk after adjusting for IE risk factors.

HANDOC: A Handy Score to Determine the Need for Echocardiography in Non-β-Hemolytic Streptococcal Bacteremia

Background

Non-β-hemolytic streptococci (NBHS) can cause infective endocarditis (IE). Echocardiography is used to diagnose IE, but it is not known which patients with NBHS bacteremia should undergo echocardiography.

Method

Medical records of patients with NBHS bacteremia in southern Sweden from 2012 to 2014 were studied retrospectively. The patients were divided into 2 cohorts. In the first, correlations between the reported data and IE were studied. These variables were used to construct the HANDOC score, which was then validated in the second cohort.

Results

Three hundred thirty-nine patients with NBHS bacteremia were included in the first cohort, of whom 26 fulfilled the criteria for IE. Several factors differed significantly between the patients with IE and those without. Among these variables, the presence of Heart murmur or valve disease; Aetiology with the groups of Streptococcus mutans, Streptococcus bovis, Streptococcus sanguinis, or Streptococcus anginosus; Number of positive blood cultures ≥2; Duration of symptoms of 7 days or more; Only 1 species growing in blood cultures; and Community-acquired infection were chosen to form the HANDOC score. With a cutoff between 2 and 3 points, HANDOC had a sensitivity of 100% and specificity of 73% in the first cohort. When tested in the validation cohort (n = 399), the sensitivity was 100% and the specificity 76%.

Conclusions

HANDOC can be used in to identify patients with NBHS bacteremia who have a risk of IE so low that echocardiography can be omitted; therefore, its implementation might reduce the use of echocardiography.

External validation of the HANDOC score - high sensitivity to identify patients with non-beta-haemolytic streptococcal endocarditis

Background: Invasive infections with non-beta-haemolytic streptococci (NBHS) is quite common and presents the clinicians with difficulties regarding which patients are at risk for infective endocarditis (IE). The HANDOC score was developed to identify patients with NBHS bacteraemia who are at low risk of IE. This study was conducted to validate HANDOC in an external cohort.Methods: Patients with NBHS in blood cultures between March and September 2016 in a Danish centre were included as part of an on-going study. Patient characteristics were collected to classify bacteria according to Dukés criteria and the components of the HANDOC score were collected retrospectively from the patients' medical records.Results: 68 patients were included in the cohort, of which 16 fulfilled Dukés criteria for IE. All patients with IE (16 of 16) had a HANDOC score above the predefined cut-off. Cases of IE were found in patients with. Streptococcus mitis, Streptococcus bovis, Streptococcus mutans, Streptococcus anginosus, and Streptococcus sanguinis group streptococci. The HANDOC score thus had a sensitivity of 100% and a specificity of 62% in this cohort.Conclusions: HANDOC has a sensitivity of 100% and a relatively high specificity (62%) also in a prospectively enrolled cohort of patients from another country than its origin. This indicates that HANDOC can be implemented in clinical practice to identify patients with a low risk of IE in whom echocardiography can be omitted.

The clinical impact of patients with bloodstream infection with different groups of Viridans group streptococci by using matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS)

The accuracy of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for identifying viridans group streptococcus (VGS) was improving. However, the clinical impact of identifying VGS had not been well recognized. Our study had comprehensively studied the clinical manifestations and outcome of VGS blood stream infection by using MALDI-TOF MS for identification.This retrospective study enrolled 312 adult patients with a monomicrobial blood culture positive for VGS. Blood culture was examined through MALDI-TOF MS.The most common VGS species were the Streptococcus anginosus group (38.8%) and Streptococcus mitis group (22.8%). Most species showed resistance to erythromycin (35.6%), followed by clindamycin (25.3%) and penicillin (12.5%). Skin and soft tissue infection and biliary tract infection were significantly related to S. anginosus group bacteremia (P = .001 and P = .005, respectively). S. mitis group bacteremia was related to infective endocarditis and bacteremia with febrile neutropenia (P = .005 and P < .001, respectively). Infective endocarditis was also more likely associated with S. sanguinis group bacteremia (P = .009). S. anginosus group had less resistance rate to ampicillin, erythromycin, clindamycin, and ceftriaxone (P = .019, <.001, .001, and .046, respectively). A more staying in intensive care unit, underlying solid organ malignancy, and a shorter treatment duration were independent risk factors for 30-day mortality. This study comprehensively evaluated different VGS group and their clinical manifestations, infection sources, concomitant diseases, treatments, and outcomes. Categorizing VGS into different groups by MALDI-TOF MS could help clinical physicians well understand their clinical presentations.

Antimicrobial Resistance in Streptococcus spp

The genus Streptococcus includes Gram-positive organisms shaped in cocci and organized in chains. They are commensals, pathogens, and opportunistic pathogens for humans and animals. Most Streptococcus species of veterinary relevance have a specific ecological niche, such as S. uberis, which is almost exclusively an environmental pathogen causing bovine mastitis. In contrast, S. suis can be considered as a true zoonotic pathogen, causing specific diseases in humans after contact with infected animals or derived food products. Finally, Streptococcus species such as S. agalactiae can be sporadically zoonotic, even though they are pathogens of both humans and animals independently. For clarification, a short taxonomical overview will be given here to highlight the diversity of streptococci that infect animals. Several families of antibiotics are used to treat animals for streptococcal infections. First-line treatments are penicillins (alone or in combination with aminoglycosides), macrolides and lincosamides, fluoroquinolones, and tetracyclines. Because of the selecting role of antibiotics, resistance phenotypes have been reported in streptococci isolated from animals worldwide. Globally, the dynamic of resistance acquisition in streptococci is slower than what is experienced in Enterobacteriaceae, probably due to the much more limited horizontal spread of resistance genes. Nonetheless, transposons or integrative and conjugative elements can disseminate resistance determinants among streptococci. Besides providing key elements on the prevalence of resistance in streptococci from animals, this article will also largely consider the mechanisms and molecular epidemiology of the major types of resistance to antimicrobials encountered in the most important streptococcal species in veterinary medicine.

Distribution of streptococcal groups causing infective endocarditis: a descriptive study

The purpose of this study was to describe the distribution of streptococci causing infective endocarditis (IE). A total of 296 patients with definite IE admitted from July 2007 to December 2014 were identified, with microbial identification done by a combination of blood culture, valve culture, and valve polymerase chain reaction (PCR). The overall distribution of streptococci was 76% viridans (n = 224), 17% pyogenic (50), 6% nutritionally variant (17), and 2% anaerobic (5). Sixty-three (21%) viridans group streptococci were not identified further. The distribution of the remaining 161 viridans group streptococci was Streptococcus mitis group 61%, S. bovis group 15%, S. mutans group 13%, S. anginosus group 9%, and S. salivarius group 1%. Of the 50 pyogenic streptococci, 78% were S. agalactiae and 16% were S. dysgalactiae. PCR was significantly more sensitive than culture in identifying streptococci in excised heart valves.

Methods of Biotyping of Streptococcus mutans Species with the Routine Test as a Prognostic Value in Early Childhood Caries

Purpose

In order to investigate the suitability of Streptococcus mutans species biotyping by measuring the activity of selected enzymes from a commercial test, criteria were established for biotyping clinical strains from children with dental caries. In addition, the relationships between the selected biotypes, sensitivity to commonly used antibiotics, and early childhood caries were determined.

Methods

A total of 142 S. mutans isolates from dental plaque of children with caries were divided into different biotypes. Patients were divided into two groups: noncavitated (1-2 in ICDAS) and cavitated (5-6 in ICDAS) lesions. Biotyping criteria were determined based on both the arbitrary method and the clusterization method. The susceptibility of the strains to amoxicillin, cefazolin, erythromycin, and teicoplanin was studied by diluting a solid medium.

Results

Biotype I was the most common. Mean MIC values showed that the strains belonging to biotypes II and IV were the most sensitive to amoxicillin. For predetermined biotypes, observed differences were dependent on the severity of dental caries.

Conclusions

The proposed method of S. mutans strains biotyping is relatively quick and simple to use, provided the application of suitable biotyping criteria, and may contribute to the effective prevention of dental caries induced by S. mutans.

Concerted functions of Streptococcus gordonii surface proteins PadA and Hsa mediate activation of human platelets and interactions with extracellular matrix

A range of Streptococcus bacteria are able to interact with blood platelets to form a thrombus (clot). Streptococcus gordonii is ubiquitous within the human oral cavity and amongst the common pathogens isolated from subjects with infective endocarditis. Two cell surface proteins, Hsa and Platelet adherence protein A (PadA), in S. gordonii mediate adherence and activation of platelets. In this study, we demonstrate that PadA binds activated platelets and that an NGR (Asparagine-Glycine-Arginine) motif within a 657 amino acid residue N-terminal fragment of PadA is responsible for this, together with two other integrin-like recognition motifs RGT and AGD. PadA also acts in concert with Hsa to mediate binding of S. gordonii to cellular fibronectin and vitronectin, and to promote formation of biofilms. Evidence is presented that PadA and Hsa are each reliant on the other's active presentation on the bacterial cell surface, suggesting cooperativity in functions impacting both colonization and pathogenesis.