Review of streptococcal bloodstream infections at a comprehensive cancer care center, 2000–2011

Unveiling the genetic landscape of Streptococcus agalactiae bacteremia: emergence of hypervirulent CC1 strains and new CC283 strains in Tehran, Iran

BACKGROUND

The emergence of Streptococcus agalactiae infections in patients with bacteremia is increasing. It is crucial to investigate the epidemiology, molecular characteristics, biofilm status, and virulence analysis of Streptococcus agalactiae in these patients.

METHODS

In this cross-sectional study, 61 S. agalactiae isolated from blood infection were subjected to characterization through antimicrobial susceptibility tests, biofilm formation, multilocus sequence typing (MLST), and PCR analysis for detecting resistance (tet and erm family) and virulence genes (alp2/3, alp4, bca, bac, eps, rib, lmb, cylE, and pilus island genes).

RESULTS

Overall, 32.7% of the isolates demonstrated an inducible clindamycin resistance phenotype. The results showed that 49.2, 24.6, and 8.2% of confirmed Streptococcus agalactiae strains were classified as strong, intermediate, and weak biofilm-forming strains, respectively. tet(M) (57.1%) was recovered most, followed by tet(M) + tet(L) (14.3%), tet(S) + tet(K) (10.7%), tet(M) + tet(K) (8.9%), tet(M) + tet(K) + tet(O) (5.4%), and tet(S) + tet(L) + tet(O) (3.6%). Three virulence gene profiles of cylE, lmb, bca, rib (24.6%; 15/61), cylE, lmb, rib, alp3 (19.7%; 12/61), and cylE, lmb, bac, rib (16.4%; 10/61) were detected in approximately two-thirds of the isolates. MLST revealed that the 61 isolates belonged to six clonal complexes, including CC1 (49.2%), followed by CC12 (18%), CC19 (13.1%), CC22 (9.8%), CC17 (6.6%), and CC283 (3.3%), and 11 different sequence types (STs), including ST1 (24.6%), ST7 (14.8%), ST918 (13.1%), ST2118 (9.8%), ST19 (9.8%), ST48 (6.6%), ST1372 (4.9%), ST22 (4.9%), ST40 (4.9%), ST734 (3.3%), and ST283 (3.3%). Remarkably, all CC1 and CC12 isolates, three-fourths of CC19, and half of CC22 were confirmed as biofilm producers. Conversely, CC17 and CC28 isolates were found to be nonproducers. The occurrence of strong biofilm formation was limited to specific CCs, namely CC1 (34.4%), CC12 (8.2%), CC19 (3.3%), and CC22 (3.3%).

CONCLUSION

The high prevalence of CC1 and CC12 clones among S. agalactiae strains reflects the emergence of these lineages as successful clones in Iran, which is a serious concern and poses a potential threat to patients.

Predictors of Mortality of Streptococcal Bacteremia and the Role of Infectious Diseases Consultation: A Retrospective Cohort Study

BACKGROUND

Streptococcal bacteremia is associated with high mortality. Thia study aims to identify predictors of mortality among patients with streptococcal bacteremia.

METHODS

This retrospective study was conducted at the Lausanne University Hospital, Switzerland, and included episodes of streptococcal bacteremia among adult patients from 2015 to 2023.

RESULTS

During the study period, 861 episodes of streptococcal bacteremia were included. The majority of episodes were categorized in the Mitis group (348 episodes; 40%), followed by the Pyogenic group (215; 25%). Endocarditis was the most common source of bacteremia (164; 19%). The overall 14-day mortality rate was 8% (65 episodes). The results from the Cox multivariable regression model showed that a Charlson comorbidity index >4 (P .001; hazard ratio [HR], 2.87; confidence interval [CI]: 1.58-5.22), Streptococcus pyogenes (P = .011; HR, 2.54;CI: 1.24-5.21), sepsis (P < .001; HR, 7.48; CI: 3.86-14.47), lower respiratory tract infection (P = .002; HR, 2.62; CI: 1.42-4.81), and absence of source control interventions within 48 hours despite being warranted (P = .002; HR, 2.62; CI: 1.43-4.80) were associated with 14-day mortality. Conversely, interventions performed within 48 hours of bacteremia onset, such as infectious diseases consultation (P < .001; HR, 0.29; CI: .17-.48) and appropriate antimicrobial treatment (P < .001; HR, .28; CI: .14-.57), were associated with improved outcome.

CONCLUSIONS

Our findings underscore the pivotal role of infectious diseases consultation in guiding antimicrobial treatment and recommending source control interventions for patients with streptococcal bacteremia.

Ali G, Alzubaidi K, Ali B, Ismail A, Daghfal J, Almaslamani M, Hadi HA. Microbiological and clinical characteristics of invasive Group B Streptococcal blood stream infections in children and adults from Qatar

INTRODUCTION

Group B Streptococci (GBS) colonize almost one third of human gastrointestinal and genitourinary tracts, particularly in females. The aim of this study is to evaluate the epidemiology, microbiological characteristics, and clinical outcomes of invasive GBS disease in Qatar from all age groups.

METHODS

A retrospective study was conducted on patients with confirmed GBS blood stream infections during the period between January 2015 and March 2019. Microbiological identification was performed using automated BD PhoenixTM system, while additional antimicrobial susceptibility tests were performed using E test and disc diffusion methods.

RESULT

During the four years period, the incidence steadily rose from 1.48 to 2.09 cases per 100.000 population. Out of 196 confirmed cases of invasive GBS infections, the majority were females (63.7%, 125/196) of which 44.8% were pregnant and 53.6% were colonized. Three distinct affected age groups were identified: children ≤ 4 years of age (35.7%), young adults 25-34 (20.9%) and the elderly ≥ 65 year (17.4%). Presenting symptoms were mild with fever in 53% of cases while 89% of cases had Pitt bacteraemia score of ≤ 2. Isolates were universally sensitive to penicillin, ceftriaxone, and vancomycin at 100% but with significant resistance to erythromycin (49%) and clindamycin (28.6%) while 16.8% had inducible clindamycin resistance. Clinical outcomes showed cure rate of 87.25% with complications in (8.76%) and 4% mortality.

CONCLUSION

There is a rising trend of Group B Streptococcal blood stream infections in Qatar with significantly high clindamycin and erythromycin resistance rates. Universal susceptibility rates were demonstrated for penicillin, ceftriaxone, and vancomycin.

Identification of Prognostic Factors in Patients With Streptococcus Bloodstream Infection

Aim

The purpose of this study was to explore prognostic factors of bloodstream infections (BSIs), a common severe infection and a major cause of mortality worldwide, so as to construct a prognosis model of patients with BSI.

Materials and Methods

Clinical and biochemical test data were obtained retrospectively from the medical records of 562 patients with BSI who had been treated at a single center; the end point was 60 days of all-cause death. The chi-square test was used to compare the mortality of patients grouped by the types of antibiotic treatment. The logistic regression analysis was adopted to identify prognostic factors; the Kaplan–Meier survival curve and log-rank test were conducted to compare the survival rate of patients with different prognostic factors; the receiver operating characteristic (ROC) curve was used to estimate the predictive value of different prognostic factors.

Results

Of the 562 patients, 455 survived (80.96%), and 107 died (19.04%). The mortality rate of patients treated with a combination of antibiotics (25.40%) was higher than that treated with a single antibiotic (15.82%). Univariate analysis identified 19 prognostic factors for patients with BSI, including gender, age, diabetes, malignant tumor (non-blood system), total hospitalization time, alanine aminotransferase, aspartate aminotransferase, total protein, albumin, total bilirubin, direct bilirubin, creatinine, ratio of granulocytes, fibrinogen, D-dimer, platelet, C-reactive protein, shock, and respiratory failure (P < 0.05). Multivariate analysis indicated that albumin (odds ratio [OR] = 0.94, 95% confidence interval [CI]: 0.89–0.99), fibrinogen (OR = 0.61, 95%CI: 0.46–0.82), shock (OR = 16.61, 95%CI: 7.00–39.41), and respiratory failure (OR = 47.53, 95%CI: 19.93–133.64) were independent factors. The combination of four indicators demonstrated a favorable predictive value for the 60-day outcome of patients with BSI, with an area under the ROC of 0.96 (95%CI: 0.94–0.99), sensitivity of 90.65%, specificity of 94.95%, and accuracy of 94.13%.

Conclusions

Shock, respiratory failure, albumin, and fibrinogen are potential independent prognostic factors for 60-day mortality.

Infections in Hospitalized Cancer Patients

Cancer patients are at an increased risk of developing infections that are primarily treatment-driven but may also be malignancy-driven. While cancer treatments such as chemotherapy, radiotherapy, and surgery have been known to improve malignancy morbidity and mortality, they also have the potential to weaken immune defenses and induce periods of severe cytopenia. These adverse effects pave the way for opportunistic infections to complicate a hospitalized cancer patient's clinical course. Understanding the risk each patient inherently has for developing a bacterial, fungal, or viral infection is critical to choosing the correct prophylactic treatment in conjunction with their scheduled cancer therapy. This review discusses the most common types of infections found in hospitalized cancer patients as well as the current guidelines for prophylactic and antimicrobial treatment in cancer patients. In addition, it describes the interaction between antibiotics and cancer therapies for consideration when treating infection in a cancer patient.

Burden of invasive group B Streptococcus disease in non-pregnant adults: A systematic review and meta-analysis

Background

Streptococcus agalactiae or group B Streptococcus (GBS) has emerged as an important cause of invasive disease in adults, particularly among the elderly and those with underlying comorbidities. Traditionally, it was recognised as an opportunistic pathogen colonising and causing disease in pregnant women, neonates, and young infants. Reasons for the upsurge of invasive GBS (iGBS) among the elderly remain unclear, although it has been related to risk factors such as underlying chronic diseases, immunosenescence, impaired inflammatory response, and spread of virulent clones. Antibiotics are successfully as treatment or prophylaxis against iGBS. Several candidate vaccines against iGBS are under development.

Objectives

To conduct a systematic review of the current literature on invasive GBS in order to determine disease incidence and case fatality ratio (CFR) among non-pregnant adults. Additionally, information on risk factors, clinical presentation, serotype distribution, and antimicrobial resistance was also retrieved.

Methods

Between January and June 2020, electronic searches were conducted in relevant databases: MEDLINE, EMBASE, Global Health, and SCOPUS. Studies were included in the systematic review if they met the inclusion/exclusion criteria. The authors assessed the selected studies for relevance, risk of bias, outcome measures, and heterogeneity. Meta-analyses on incidence and CFR were conducted after evaluating the quality of methods for assessment of exposure and outcomes.

Results

Pooled estimates of iGBS incidence in non-pregnant adults 15 years and older were 2.86 cases per 100.000 population (95% CI, 1.68–4.34). Incidence rates in older adults were substantially higher, 9.13 (95%CI, 3.53–17.22) and 19.40 (95%CI, 16.26–22.81) per 100.000 population ≥50 and ≥ 65 years old, respectively. Incidence rates ranged from 0.40 (95% CI, 0.30–0.60) in Africa to 5.90 cases per 100.000 population (95% CI, 4.30–7.70) in North America. The overall CFR was and 9.98% (95% CI, 8.47–11.58). CFR was highest in Africa at 22.09% (95% CI, 12.31–33.57). Serotype V was the most prevalent serotype globally and in North America accounting for 43.48% (n = 12926) and 46,72% (n = 12184) of cases, respectively. Serotype Ia was the second and serotype III was more prevalent in Europe (25.0%) and Asia (29.5%). Comorbidities were frequent among non-pregnant adult iGBS cases. Antimicrobial resistance against different antibiotics (i.e., penicillin, erythromycin) is increasing over time.

Conclusions

This systematic review revealed that iGBS in non-pregnant adults has risen in the last few years and has become a serious public health threat especially in older adults with underlying conditions. Given the current serotype distribution, vaccines including serotypes predominant among non-pregnant adults (i.e., serotypes V, Ia, II, and III) in their formulation are needed to provide breadth of protection. Continued surveillance monitoring potential changes in serotype distribution and antimicrobial resistance patterns are warranted to inform public health interventions.

Inflammation and cancer: paradoxical roles in tumorigenesis and implications in immunotherapies

Chronic inflammation caused by persistent infections and metabolic disorders is thought to contribute to the increased cancer risk and the accelerated cancer progression. Oppositely, acute inflammation induced by bacteria-based vaccines or that is occurring after cancer selectively inhibits cancer progression and metastasis. However, the interaction between inflammation and cancer may be more complex than the current explanations for the relationship between chronic and acute inflammation and cancer. In this review, we described the impact of inflammation on cancer on the basis of three perspectives, including inflammation with different durations (chronic and acute inflammation), different scopes (systemic and local inflammation) and different occurrence sequences (inflammation occurring after and before cancer). In addition, we also introduced bacteria/virus-based cancer immunotherapies. We perceive that inflammation may be a double-edged sword with cancer-promoting and cancer-suppressing functions in certain cases. We expect to further improve the understanding of the relationship between inflammation and cancer and provide a theoretical basis for further research on their complex interaction.

Fluoroquinolone treatment as a protective factor for 10-day mortality in Streptococcus pneumoniae bacteremia in cancer patients

To evaluate the prognostic factors in adult cancer patients with pneumococcal bacteremia, describe episode features and the phenotypic characteristics of the isolated strains. We evaluated the episodes in patients admitted to a cancer hospital between 2009 and 2015. The outcomes were defined as 48 h mortality and mortality within 10 days after the episode. The variables evaluated were: age, sex, ethnicity, ECOG, Karnofsky score, SOFA, cancer type, metastasis, chemotherapy, radiotherapy, neutropenia, previous antibiotic therapy, community or healthcare-acquired infection, comorbidities, smoking, pneumococcal vaccination, infection site, presence of fever, polymicrobial infection, antimicrobial susceptibility, serotype and treatment. 165 episodes were detected in 161 patients. The mean age was 61.3 years; solid tumors were the most prevalent (75%). 48 h and 10-day mortality were 21% (34/161) and 43% (70/161) respectively. The 48 h mortality- associated risk factors were SOFA and polymicrobial bacteremia; 10-day mortality-associated risk factors were fever, neutropenia, ECOG 3/4, SOFA and fluoroquinolones as a protective factor. Pneumococcal bacteremia presented high mortality in cancer patients, with prognosis related to intrinsic host factors and infection episodes features. Fluoroquinolone treatment, a protective factor in 10-day mortality, has potential use for IPDs and severe community-acquired pneumonia in cancer patients.

Genetic Basis Underlying the Hyperhemolytic Phenotype of Streptococcus agalactiae Strain CNCTC10/84

Streptococcus agalactiae (group B streptococcus [GBS]) is a major cause of infections in newborns, pregnant women, and immunocompromised patients. GBS strain CNCTC10/84 is a clinical isolate that has high virulence in animal models of infection and has been used extensively to study GBS pathogenesis. Two unusual features of this strain are hyperhemolytic activity and hypo-CAMP factor activity. These two phenotypes are typical of GBS strains that are functionally deficient in the CovR-CovS two-component regulatory system. A previous whole-genome sequencing study found that strain CNCTC10/84 has intact covR and covS regulatory genes. We investigated CovR-CovS regulation in CNCTC10/84 and discovered that a single-nucleotide insertion in a homopolymeric tract in the covR promoter region underlies the strong hemolytic activity and weak CAMP activity of this strain. Using isogenic mutant strains, we demonstrate that this single-nucleotide insertion confers significantly decreased expression of covR and covS and altered expression of CovR-CovS-regulated genes, including that of genes encoding β-hemolysin and CAMP factor. This single-nucleotide insertion also confers significantly increased GBS survival in human whole blood ex vivo IMPORTANCE Group B streptococcus (GBS) is the leading cause of neonatal sepsis, pneumonia, and meningitis. GBS strain CNCTC10/84 is a highly virulent blood isolate that has been used extensively to study GBS pathogenesis for over 20 years. Strain CNCTC10/84 has an unusually strong hemolytic activity, but the genetic basis is unknown. In this study, we discovered that a single-nucleotide insertion in an intergenic homopolymeric tract is responsible for the elevated hemolytic activity of CNCTC10/84.

Genome-Wide Assessment of Streptococcus agalactiae Genes Required for Survival in Human Whole Blood and Plasma

Streptococcus agalactiae (group B streptococcus, or GBS) is a common cause of bacteremia and sepsis in newborns, pregnant women, and immunocompromised patients. The molecular mechanisms used by GBS to survive and proliferate in blood are not well understood. Here, using a highly virulent GBS strain and transposon-directed insertion site sequencing (TraDIS), we performed genome-wide screens to discover novel GBS genes required for bacterial survival in human whole blood and plasma. The screen identified 85 and 41 genes that are required for GBS growth in whole blood and plasma, respectively. A common set of 29 genes was required in both whole blood and plasma. Targeted gene deletion confirmed that (i) genes encoding methionine transporter (metP) and manganese transporter (mtsA) are crucial for GBS survival in whole blood and plasma, (ii) gene W903_1820, encoding a small multidrug export family protein, contributes significantly to GBS survival in whole blood, (iii) the shikimate pathway gene aroA is essential for GBS growth in whole blood and plasma, and (iv) deletion of srr1, encoding a fibrinogen-binding adhesin, increases GBS survival in whole blood. Our findings provide new insight into the GBS-host interactions in human blood.

Streptococcus pneumoniae: distribution of serotypes and antimicrobial susceptibility in patients with cancer

OBJECTIVE

To describe the distribution of pneumococcal serotypes causing infectious diseases in patients with hematological malignancies and solid tumors and their antimicrobial susceptibility before and after introduction of pneumococcal conjugate vaccine (PCV7) in Mexico.

MATERIALS AND METHODS

Consecutive pneumococcal isolates from hospitalized patients from the SIREVA-network were serotyped using the Quellung reaction and antimicrobial susceptibility was performed using the broth microdilution method.

RESULTS

A total of 175 pneumococcal isolates were recovered, 105 from patients with hematological malignancies and 70 with solid tumors. Serotypes 19A (22.7%), 19F (20.4%), and 35B (17.7%) were the most frequent isolates in the first group and serotypes 3 (27.2%) and 19A (28.6%) in the second group. No decreased susceptibility to beta-lactams or TMP/SMX was observed after introduction of PCV7.

CONCLUSIONS

An increase in non-vaccine types is observed without significate changes in antimicrobial susceptibility after introduction of PCV7.

In vitro activity of ceftaroline and comparator agents against Gram-positive and Gram-negative clinical isolates from cancer patients

Bacterial infections are common in cancer patients. Ceftaroline (CFT) is a broad-spectrum cephalosporin with activity against most Gram-positive organisms (GPOs) and many Gram-negative organisms. In this study, the in vitro activity of CFT was compared with vancomycin (VAN), daptomycin (DAP), linezolid (LZD), trimethoprim/sulphamethoxazole (SXT) and tigecycline (TIG) against bacteria (predominantly blood culture isolates) isolated from cancer patients in 2014 and 2015. CFT was active against methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), methicillin-susceptible coagulase-negative staphylococci (MS-CoNS) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) with MIC90 values (minimum inhibitory concentration that inhibited 90% of the isolates) of 0.25, 2.0, 0.12 and 0.5 mg/L, respectively. MIC90 values for other GPOs were: Bacillus spp., >8.0 mg/L; Corynebacterium spp., 2.0 mg/L; Micrococcus spp., <0.06 mg/L; viridans group streptococci, 0.5 mg/L; Streptococcus pneumoniae, 0.25 mg/L; and Streptococcus spp., <0.06 mg/L. Among the comparator agents, VAN, DAP, TIG and LZD were active against the majority of GPOs tested. CFT also had moderate activity against common extended-spectrum β-lactamase (ESBL)-negative Gram-negative bacilli such as Enterobacter cloacae, Escherichia coli, Klebsiella spp., Proteus mirabilis and Serratia spp.

Effect of underlying immune compromise on the manifestations and outcomes of group A streptococcal bacteremia

BACKGROUND

Group A streptococcal bloodstream infection is the most common presentation of invasive group A streptococcal disease. We sought to determine the impact of immunosuppression on severity of disease and clinical outcomes.

METHODS

This retrospective review of 148 patients with at least one positive blood culture for Streptococcus pyogenes from 1/2003 to 3/2013 compared immunocompromised patients with those with no immunocompromise in regards to development of severe complications and mortality.

RESULTS

Twenty-five patients (17%) were immunocompromised; 123 were not. Skin and soft tissue infection occurred in 60% of immunocompromised vs. 38% of non-immunocompromised patients, p = .04. Necrotizing fasciitis and septic shock were significantly more common in immunocompromised patients, p < .0001 and .028, respectively. Mortality at 30 days was 32% in immunocompromised patients vs. 16% in non-immunocompromised patients, p = .05.

CONCLUSION

Patients who are immunocompromised are more likely to develop necrotizing fasciitis and septic shock as complications of group A streptococcal bacteremia and have a higher mortality rate than patients who are not immunocompromised.

Invasive gram-positive bacterial infection in cancer patients

Systematic studies have shown that gram-positive organisms are the leading cause of invasive bacterial disease in patients with cancer. A broad range of gram-positive bacteria cause serious infections in the cancer patient with the greatest burden of disease being due to staphylococci, streptococci, and enterococci. The evolution of cancer therapy and the changing epidemiology of major gram-positive pathogens mean that ongoing efforts are needed to understand and mitigate the impact of these bacteria in patients with malignancy. The development of novel antibacterials, optimization of treatment approaches, implementation of improved vaccines, and manipulation of the microbiome are all active areas of investigation in the goal of improving the survival of the cancer patient through amelioration of the disease burden of gram-positive bacteria.

Spectrum of gram-positive bacteraemia and in vitro activities of daptomycin, linezolid and vancomycin against organisms isolated from cancer patients

Gram-positive organisms are the predominant bacterial pathogens in cancer patients. A survey indicated that coagulase-negative staphylococci (CoNS) (29.5%), Staphylococcus aureus (18.0%), Enterococcus spp. (12.1%) and viridans group streptococci (VGS) (9.1%) are isolated most often. The rate of reduced susceptibility to vancomycin (minimum inhibitory concentration ≥1.0 μg/mL) was 100% for meticillin-susceptible S. aureus and 99% for meticillin-resistant S. aureus, and 100% for meticillin-susceptible CoNS and 98% for meticillin-resistant CoNS. More than 98% of these isolates were susceptible to daptomycin and linezolid. Daptomycin and linezolid had comparable in vitro activity to vancomycin against Bacillus spp., Corynebacterium spp., Rhodococcus spp., Micrococcus spp., Stomatococcus mucilaginosus and VGS. Both agents were active against the majority (95%) of vancomycin-resistant organisms, including vancomycin-resistant enterococci, Pediococcus spp. and Leuconostoc spp. These data suggest that daptomycin and linezolid have an adequate antimicrobial spectrum and potent in vitro activity against Gram-positive isolates from cancer patients and may be considered as alternatives to vancomycin for empirical or targeted therapy in this setting.