Diabetes increases the risk of disease and death due to Staphylococcus aureus bacteremia. A matched case-control and cohort study

Retrospective study to investigate appropriate duration of antibiotic treatment for uncomplicated Staphylococcus aureus bacteremia in patients with immunodeficiency

BACKGROUND

Since the appropriate antibiotic duration for uncomplicated Staphylococcus aureus (S. aureus) bacteremia (u-SAB) in an immunocompromised state is still unclear, physicians are likely to extend antibiotic therapy from 2 weeks to 4-6 weeks. To examine the appropriate duration of antibiotic therapy for u-SAB, we performed this study.

PATIENTS AND METHODS

We reviewed all patients with u-SAB at our institute seen between January 2020 and August 2023. A total of 51 patients were enrolled, and they were divided into the following two groups by antibiotic duration: longer duration group ≥28 days after blood culture negativity, and shorter duration group. Then, the patients were matched by a propensity score using the covariates of age, sex, qSOFA, and CCI. The primary outcome was to identify the prognosis by duration of antibiotic treatment.

RESULTS

After propensity score matching, all-cause 30-day mortality was 0 % in both groups. Hence, there was no significant difference in all-cause 90 days mortality (19.0% vs 9.5%, p = 0.33) or recurrence (9.5%% vs 0%, p = 0.22). Before propensity-score matching, we found that a serum level of CRP 2.0 mg/dL and greater after intravenous antibiotic treatment was one of the poor prognostic factors. The cut-off value of serum CRP level was 2.0 mg/dL with a sensitivity of 82.1% and a specificity of 75.0%.

CONCLUSION

We suggested that 4-6 weeks of antibiotic treatment for immunodeficient u-SAB patients was unnecessary. Moreover, the serum level of CRP after completion of IV antibiotic treatment could be a prognostic marker for u-SAB.

Mortality patterns in patients with Staphylococcus aureus bacteremia during the COVID-19 pandemic: Predictors and insights

Objectives

This paper aims to determine the Staphylococcus aureus bacteremia (SAB) in-hospital mortality rate and its associated risk factors during the COVID-19 pandemic.

Methods

A total of 167 SAB samples were collected between March 2020 and March 2022 at a teaching hospital in Tehran, Iran. The patient's baseline data and antibiograms were collected. The outcome of the study was in-hospital mortality.

Results

The overall in-hospital mortality rate was 41.9 %, with higher mortality observed in patients over 60 years old (P = 0.032), those with community-acquired Staphylococcus aureus bacteremia (P = 0.010), and those admitted to the ICU (P = 0.016). Antibiotic resistance profiles indicated a higher mortality in resistant S.aureus strains but only significant for ciprofloxacin (P = 0.001), methicillin (P = 0.047), and sulfamethoxazole (P = 0.023). Multivariate analysis identified age, sex, ICU admission, and the source of bacteremia as independent predictors of mortality, while COVID-19 coinfection and resistance to antibiotics were not found to be significant predictors.

Conclusion

SAB remains a challenging infection that is amplified by the pandemic. Older age and ICU admission are significant mortality predictors. In settings with a high prevalence of MRSA, factors like age, sex, and quality of care outweigh pathogen-related factors such as antibiotic resistance.

Clinical effects of bacteremia in sepsis patients with community-acquired pneumonia

BACKGROUND

Data regarding the clinical effects of bacteremia on severe community-acquired pneumonia (CAP) are limited. Thus, we investigated clinical characteristics and outcomes of severe CAP patients with bacteremia compared with those of subjects without bacteremia. In addition, we evaluated clinical factors associated with bacteremia at the time of sepsis awareness.

METHODS

We enrolled sepsis patients diagnosed with CAP at emergency departments (EDs) from an ongoing nationwide multicenter observational registry, the Korean Sepsis Alliance, between September 2019 and December 2020. For evaluation of clinical factors associated with bacteremia, we divided eligible patients into bacteremia and non-bacteremia groups, and logistic regression analysis was performed using the clinical characteristics at the time of sepsis awareness.

RESULT

During the study period, 1,510 (47.9%) sepsis patients were caused by CAP, and bacteremia was identified in 212 (14.0%) patients. Septic shock occurred more frequently in the bacteremia group than in the non-bacteremia group (27.4% vs. 14.8%; p < 0.001). In multivariable analysis, hematologic malignancies and septic shock were associated with an increased risk of bacteremia. However, chronic lung disease was associated with a decreased risk of bacteremia. Hospital mortality was significantly higher in the bacteremia group than in the non-bacteremia group (27.3% vs. 40.6%, p < 0.001). The most prevalent pathogen in blood culture was Klebsiella pneumoniae followed by Escherichia coli in gram-negative pathogens.

CONCLUSION

The incidence of bacteremia in severe CAP was low at 14.0%, but the occurrence of bacteremia was associated with increased hospital mortality. In severe CAP, hematologic malignancies and septic shock were associated with an increased risk of bacteremia.

Clinical impact of metformin exposure during Staphylococcus aureus bacteremia in patients with diabetes mellitus

PURPOSE

Increasing evidence has suggested that metformin may play positive roles in a wide range of infectious diseases. This study aimed to investigate the clinical impact of metformin exposure during Staphylococcus aureus bacteremia (SAB) in patients with diabetes.

METHODS

A 3-year observational cohort study of 452 patients (aged ≥ 16 years) with SAB was performed at a tertiary care hospital. Metformin exposure was defined as receiving metformin during SAB, regardless of metformin use before the onset of bacteremia.

RESULTS

Of 452 patients, 51 (11.3%) were classified in Group A (diabetes with metformin exposure), 115 (25.4%) in Group B (diabetes without metformin exposure), and 286 (63.3%) in Group C (no diabetes). The 30-day mortality rate in Group A was significantly lower than that in Group B (3.9% [2/51] versus 14.8% [17/115]; p = 0.04) and lower than that in Group C (3.9% [2/51] versus 17.1% [49/286]; p = 0.02). The mortality rates did not differ between Group B and Group C (14.8% [17/115] versus 17.1% [49/286]; p = 0.57). The rates of persistent and recurrent bacteremia were comparable among the three groups. Multivariate analysis indicated that metformin exposure was significantly associated with reduced mortality (adjusted odds ratio, 0.20; 95% confidence interval, 0.04-0.88; p = 0.03).

CONCLUSIONS

Metformin exposure during SAB appears to be an independent predictor of survival in patients with diabetes.

The characteristics of bacteremia among patients with acute febrile illness requiring hospitalization in Indonesia

Blood culturing remains the "gold standard" for bloodstream infection (BSI) diagnosis, but the method is inaccessible to many developing countries due to high costs and insufficient resources. To better understand the utility of blood cultures among patients in Indonesia, a country where blood cultures are not routinely performed, we evaluated data from a previous cohort study that included blood cultures for all participants. An acute febrile illness study was conducted from July 2013 to June 2016 at eight major hospitals in seven provincial capitals in Indonesia. All participants presented with a fever, and two-sided aerobic blood cultures were performed within 48 hours of hospital admission. Positive cultures were further assessed for antimicrobial resistance (AMR) patterns. Specimens from participants with negative culture results were screened by advanced molecular and serological methods for evidence of causal pathogens. Blood cultures were performed for 1,459 of 1,464 participants, and the 70.6% (1,030) participants that were negative by dengue NS1 antigen test were included in further analysis. Bacteremia was observed in 8.9% (92) participants, with the most frequent pathogens being Salmonella enterica serovar Typhi (41) and Paratyphi A (10), Escherichia coli (14), and Staphylococcus aureus (10). Two S. Paratyphi A cases had evidence of AMR, and several E. coli cases were multidrug resistant (42.9%, 6/14) or monoresistant (14.3%, 2/14). Culture contamination was observed in 3.6% (37) cases. Molecular and serological assays identified etiological agents in participants having negative cultures, with 23.1% to 90% of cases being missed by blood cultures. Blood cultures are a valuable diagnostic tool for hospitalized patients presenting with fever. In Indonesia, pre-screening patients for the most common viral infections, such as dengue, influenza, and chikungunya viruses, would maximize the benefit to the patient while also conserving resources. Blood cultures should also be supplemented with advanced laboratory tests when available.

Molecular Prerequisites for Neutrophil Extracellular Trap Formation and Evasion Mechanisms of Staphylococcus aureus

NETosis is a multi-facetted cellular process that promotes the formation of neutrophil extracellular traps (NETs). NETs as web-like structures consist of DNA fibers armed with granular proteins, histones, and microbicidal peptides, thereby exhibiting pathogen-immobilizing and antimicrobial attributes that maximize innate immune defenses against invading microbes. However, clinically relevant pathogens often tolerate entrapment and even take advantage of the remnants of NETs to cause persistent infections in mammalian hosts. Here, we briefly summarize how Staphylococcus aureus, a high-priority pathogen and causative agent of fatal diseases in humans as well as animals, catalyzes and concurrently exploits NETs during pathogenesis and recurrent infections. Specifically, we focus on toxigenic and immunomodulatory effector molecules produced by staphylococci that prime NET formation, and further highlight the molecular and underlying principles of suicidal NETosis compared to vital NET-formation by viable neutrophils in response to these stimuli. We also discuss the inflammatory potential of NET-controlled microenvironments, as excessive expulsion of NETs from activated neutrophils provokes local tissue injury and may therefore amplify staphylococcal disease severity in hospitalized or chronically ill patients. Combined with an overview of adaptation and counteracting strategies evolved by S. aureus to impede NET-mediated killing, these insights may stimulate biomedical research activities to uncover novel aspects of NET biology at the host-microbe interface.

Modification of physico-chemical surface properties and growth of Staphylococcus aureus under hyperglycemia and ketoacidosis conditions

Diabetes is a widely spread disease affecting the quality of life of millions of people around the world and is associated to a higher risk of developing infections in different parts of the body. The reasons why diabetes enhances infection episodes are not entirely clear; in this study our aim was to explore the changes that one of the most frequently pathogenic bacteria undergoes when exposed to hyperglycemia and ketoacidosis conditions. Physical surface properties such as hydrophobicity and surface electrical charge are related to bacterial growth behavior and the ability of Staphylococcus aureus to form biofilms. The addition of glucose made bacteria more negatively charged and with moderate-intermediate hydrophobicity. Ketone bodies increased hydrophobicity to approximately 75% and pathological concentrations hindered some of the bacterial surface charge by decreasing the negative zeta potential of cells. When both components were present, the bacterial physical surface changes were more similar to those observed in ketone bodies, suggesting a preferential adsorption of ketone bodies over glucose because of the more favorable solubility of glucose in water. Glucose diabetic concentrations gave the highest number of bacteria in the stationary phase of growth and provoked an increase in the biofilm slime index of around 400% in relation to the control state. Also, this situation is related with an increase of bacterial coverage. The combination of a high concentration of glucose and ketone bodies, which corresponds to a poorly controlled diabetic situation, appears associated with an early infection phase; increased hydrophobic attractive force and reduced electrostatic repulsion between cells results in better packing of cells within the biofilm and more efficient retention to the host surface. Knowledge of bacterial response in high amount of glucose and ketoacidosis environments can serve as a basis for designing strategies to prevent bacterial adhesion, biofilm formation and, consequently, the development of infections.

The prevalence of the iutA and ibeA genes in Escherichia coli isolates from severe and non-severe patients with bacteremic acute biliary tract infection is significantly different

Background

Although Escherichia coli is the most frequently isolated microorganism in acute biliary tract infections with bacteremia, data regarding its virulence are limited.

Results

Information on cases of bacteremia in acute biliary tract infection in a retrospective study was collected from 2013 to 2015 at a tertiary care hospital in Japan. Factors related to the severity of infection were investigated, including patient background, phylogenetic typing, and virulence factors of E. coli, such as adhesion, invasion, toxins, and iron acquisition.

In total, 72 E. coli strains were identified in 71 cases, most of which primarily belonged to the B2 phylogroup (68.1%). The presence of the iutA gene (77.3% in the non-severe group, 46.4% in the severe group, P = 0.011) and the ibeA gene (9.1% in the non-severe group, and 35.7% in the severe group, P = 0.012) was significantly associated with the severity of infection. Among the patient characteristics, diabetes mellitus with organ involvement and alkaline phosphatase were different in the severe and non-severe groups.

Conclusions

We showed that bacteremic E. coli strains from acute biliary tract infections belonged to the virulent (B2) phylogroup. The prevalence of the iutA and ibeA genes between the two groups of bacteremia severity was significantly different.

Reduced Mortality of Staphylococcus aureus Bacteremia in a Retrospective Cohort Study of 2139 Patients: 2007-2015

BACKGROUND

Understanding the changing epidemiology of Staphylococcus aureus bacteremia, as well as the variables associated with poor outcomes, can yield insight into potential interventions.

METHODS

This study was a retrospective, observational cohort study of adult patients at an academic medical center in New York City who had S. aureus bloodstream infections between 1 January 2007 and 31 December 2015. Participants were divided into 3 periods: group 1 (2007-2009), group 2 (2010-2012), and group 3 (2013-2015) for trend analysis. All clinical strains were genotyped (spa.). The main outcome was 30-day all-cause mortality.

RESULTS

There were 1264 episodes of methicillin-susceptible S. aureus (MSSA) and 875 episodes of methicillin-resistant S. aureus (MRSA) bacteremia, with a rising proportion due to MSSA (55% group 1; 59% group 2; 63% group 3; P = .03.) There were no significant changes in average age, gender, Charlson score, and distribution of strain genotypes. Mortality in MRSA infection was unchanged (25% group 1; 25% group 2; 26% group 3), while mortality in MSSA infection significantly declined (18% group 1; 18% group 2; 13% group 3). The average time to antistaphylococcal therapy (AST) in MSSA infection declined during the study (3.7 days group 1; 3.5 group 2; 2.2 group 3). In multivariate analysis, AST within 7 days of initial positive MSSA culture was associated with survival.

CONCLUSIONS

Mortality in MSSA bloodstream infection is declining, associated with a decrease in time to targeted therapy. These results emphasize the potential for rapid diagnostics and early optimization of treatment to impact outcomes in MSSA bacteremia.

Chemerin and Dermcidin in Human Milk and Their Alteration in Gestational Diabetes

BACKGROUND

Chemerin and dermcidin, which have antimicrobial properties, are molecules that are also related to insulin resistance and inflammation.

RESEARCH AIMS

The aims were to determine the amounts of chemerin and dermcidin in the milk and blood of mothers with gestational diabetes, and to compare the amounts of chemerin and dermcidin in the milk and blood of mothers with and without diabetes.

METHODS

This was a two-group nonrandomized longitudinal study with a convenience sampling of mothers without gestational diabetes (n = 27) and mothers with gestational diabetes (n = 26). Human milk and blood samples were obtained from these mothers during colostrum, transitional, and mature milk periods. The amount of chemerin and dermcidin in these samples was measured by enzyme-linked immunosorbent assay.

RESULTS

The presence of chemerin and dermcidin was first detected in human milk. The amounts of chemerin and dermcidin in the blood of all the mothers were greater in the colostrum period and lowest in the mature period. The amount of chemerin and dermcidin in the milk of all the mothers was greater than that in the blood. The amounts of chemerin and dermcidin were significantly increased in both blood and human milk within the gestational age samples.

CONCLUSIONS

Chemerin and dermcidin may contribute to the protection of infants from infections during infancy. Increased amounts of these molecules found within the gestational diabetes group may also prevent adverse maternal and fetal outcomes.

Increased risk of diabetes mellitus five years after an episode of Staphylococcus aureus bacteraemia

Background: Diabetes mellitus is a risk factor for infection with Staphylococcus aureus, but it is unclear whether S. aureus infection is a prediabetic condition. Methods: Nationwide population-based matched cohort study. Incidence rate and ratio with 95% confidence interval of diabetes were estimated by negative binomial regression. Results: Of 19,988 individuals with S. aureus bacteraemia and 185,579 population comparators, 667 and 4974 had a primary diagnose of diabetes within five years after discharge of S. aureus bacteraemia corresponding to a more than double risk of diabetes (adjusted incidence rate ratio 2.28 (95% confidence interval: 2.10-2.46)). Other factors associated with an increased risk of diabetes during follow-up were male sex, increasing age and level of comorbidity. Of the S. aureus bacteraemia and population cohort, 422 (2.11%) and 4048 (2.18%), respectively, developed diabetes without complications, while 245 (1.23%) and 926 (0.50%), respectively, developed diabetes with complications. Rates of diabetes without complication were increased for individuals in the S. aureus bacteraemia cohort compared to the population cohort within the first two years after which rates were comparable while rates of diabetes with complications remained higher throughout the five year follow-up period compared to the population cohort. Conclusions: The risk of diabetes was markedly increased up to five years after S. aureus bacteraemia compared to a population cohort. In addition to screening for diabetes during hospital admittance, screening cases of S. aureus bacteraemia for diabetes in the years following S. aureus bacteraemia may allow for earlier detection of diabetes.

Staphylococcus aureus drives expansion of low-density neutrophils in diabetic mice

Diabetic individuals are at considerable risk for invasive infection by Staphylococcus aureus, however, the mechanisms underlying this enhanced susceptibility to infection are unclear. We observed increased mortality following i.v. S. aureus infection in diabetic mice compared with nondiabetic controls, correlating with increased numbers of low-density neutrophils (LDNs) and neutrophil extracellular traps (NETs). LDNs have been implicated in the inflammatory pathology of diseases such as lupus, given their release of large amounts of NETs. Our goal was to describe what drives LDN increases during S. aureus infection in the diabetic host and mechanisms that promote increased NET production by LDNs. LDN development is dependent on TGF-β, which we found to be more activated in the diabetic host. Neutralization of TGF-β, or the TGF-β-activating integrin αvβ8, reduced LDN numbers and improved survival during S. aureus infection. Targeting S. aureus directly with MEDI4893*, an α toxin-neutralizing monoclonal antibody, blocked TGF-β activation, reduced LDNs and NETs, and significantly improved survival. A comparison of gene and protein expression in high-density neutrophils and LDNs identified increased GPCRs and elevated phosphatase and tensin homolog (PTEN) in the LDN subset. Inhibition of PTEN improved the survival of infected diabetic mice. Our data identify a population of neutrophils in infected diabetic mice that correlated with decreased survival and increased NET production and describe 3 therapeutic targets, a bacterial target and 2 host proteins, that prevented NET production and improved survival.

Staphylococcus aureus bacteraemia and endocarditis - epidemiology and outcome: a review

PURPOSE

To review the epidemiology of Staphylococcus aureus bacteraemia (SAB) and endocarditis (SAE), and discuss the short- and long-term outcome.  Materials and methods: A literature review of the epidemiology of SAB and SAE.

RESULTS

The reported incidence of SAB in Western countries is 16-41/100,000 person-years. Increasing incidence has been observed in many regions, in Iceland by 27% during 1995-2008. The increase is believed to depend on changes in population risk factors and possibly better and more frequent utilization of diagnostic procedures. S. aureus is now the leading causes of infective endocarditis (IE) in many regions of the world. It accounts for 15-40% of all IE cases, and the majority of cases in people who inject drugs (PWID). Recently, the incidence of SAE in PWID in Stockholm, Sweden, was found to be 2.5/1000 person-years, with an in-hospital mortality of 2.5% in PWID as compared to 15% in non-drug users. The 30-day mortality associated with SAB amounts to 15-25% among adults in Western countries, but is lower in children (0-9%). Mortality associated with SAE is high (generally 20-30% in-hospital mortality), and symptomatic cerebral embolizations are common (12-35%). The 1-year mortality reported after SAB and SAE is 19-62% and reflects deaths from underlying diseases and complications caused by the infection. In a subset of SAE cases, valvular heart surgery is needed (15-45%), but active intravenous drug use seems to be a reason to refrain from surgery. Despite its importance, there are insufficient data on the optimal management of SAB and SAE, especially on the required duration of antibiotic therapy.  Conclusions: The epidemiology of SAB and SAE has been changing in the past decades. They still carry a substantial morbidity and mortality. Intensified studies on treatment are warranted for improving patient outcome.