Sepsis syndrome, bloodstream infections, and device-related infections

Emergency medicine updates: Evaluation and diagnosis of sepsis and septic shock

INTRODUCTION

Sepsis and septic shock are common conditions evaluated and managed in the emergency department (ED), and these conditions are associated with significant morbidity and mortality. There have been several recent updates in the literature, including guidelines, on the evaluation and diagnosis of sepsis and septic shock.

OBJECTIVE

This is the first paper in a two-part series that provides emergency clinicians with evidence-based updates concerning sepsis and septic shock. This first paper focuses on evaluation and diagnosis of sepsis and septic shock.

DISCUSSION

The evaluation, diagnosis, and management of sepsis have evolved since the first definition in 1991. Current guidelines emphasize rapid diagnosis to improve patient outcomes. However, scoring systems have conflicting data for diagnosis, and sepsis should be considered in any patient with infection and abnormal vital signs, evidence of systemic inflammation (e.g., elevated white blood cell count or C-reactive protein), or evidence of end-organ dysfunction. The clinician should consider septic shock in any patient with infection and hypotension despite volume resuscitation or who require vasopressors to maintain a mean arterial pressure ≥ 65 mmHg. There are a variety of sources of sepsis but the most common include pulmonary, urinary tract, abdomen, and skin/soft tissue. Examples of other less common etiologies include the central nervous system (e.g., meningitis, encephalitis), spine (e.g., spinal epidural abscess, osteomyelitis), cardiac (e.g., endocarditis), and joints (e.g., septic arthritis). Evaluation may include biomarkers such as procalcitonin, C-reactive protein, and lactate, but these should not be used in isolation to exclude sepsis. Imaging is a key component of evaluation and should be based on the suspected source.

CONCLUSION

There have been several recent updates in the literature including guidelines concerning sepsis and septic shock; an understanding of these updates can assist emergency clinicians and improve the care of these patients.

Cholic Acid-Derived Amphiphile which Combats Gram-Positive Bacteria-Mediated Infections via Disintegration of Lipid Clusters

Inappropriate and uncontrolled use of antibiotics results in the emergence of antibiotic resistance, thereby threatening the present clinical regimens to treat infectious diseases. Therefore, new antimicrobial agents that can prevent bacteria from developing drug resistance are urgently needed. Selective disruption of bacterial membranes is the most effective strategy for combating microbial infections as accumulation of genetic mutations will not allow for the emergence of drug resistance against these antimicrobials. In this work, we tested cholic acid (CA) derived amphiphiles tethered with different alkyl chains for their ability to combat Gram-positive bacterial infections. In-depth biophysical and biomolecular simulation studies suggested that the amphiphile with a hexyl chain (6) executes more effective interactions with Gram-positive bacterial membranes as compared to other hydrophobic counterparts. Amphiphile 6 is effective against multidrug resistant Gram-positive bacterial strains as well and does not allow the adherence of S. aureus on amphiphile 6 coated catheters implanted in mice. Further, treatment of wound infections with amphiphile 6 clears the bacterial infections. Therefore, the current study presents strategic guidelines in design and development of CA-derived membrane-targeting antimicrobials for Gram-positive bacterial infections.

Silence of long noncoding RNA NEAT1 exerts suppressive effects on immunity during sepsis by promoting microRNA-125-dependent MCEMP1 downregulation

Accumulating studies have recognized microRNAs (miRs) and long noncoding RNAs (lncRNAs) as important molecules involved in the mediation of various biological processes, including innate immunity. In this study, we investigated a novel noncoding RNA regulatory circuitry in the immunity during sepsis. A cecal ligation and puncture-induced sepsis mouse model was established to determine the expression of mast cell expression membrane protein 1 (MCEMP1). The RNA crosstalk among lncRNA nuclear enriched abundant transcript 1 (NEAT1), miR-125, and MCEMP1 was validated. Subsequently, the levels of lncRNA NEAT1, miR-125, and MCEMP1 in T lymphocytes isolated from sepsis mice were up- or downregulated by exogenous transfection in an attempt to investigate their effects on the release of inflammatory factors, the expression of immunoglobulins, the activity of T cell subsets and natural killer (NK) cells, as well as T lymphocyte apoptosis. In sepsis mice, MCEMP1 was highly expressed and verified to be a target gene of miR-125. RNA crosstalk experiment revealed that lncRNA NEAT1 directly inhibited miR-125 to upregulate MCEMP1. We also observed that elevation of miR-125, depletion of MCEMP1, or downregulation of lncRNA NEAT1 resulted in promoted T lymphocyte activity, immunoglobulin expression, and NK cell activity, and inhibited release of inflammatory factors and T lymphocyte apoptosis. Taken together, these findings provided evidence that the downregulation of lncRNA NEAT1 could promote miR-125 to exert an inhibitory effect on the immunity in septic mice by suppressing MCEMP1, highlighting a potential target for the treatment of sepsis. © 2019 IUBMB Life, 2019.

Prediction of Broad-Spectrum Pathogen Attachment to Coating Materials for Biomedical Devices

Bacterial infections in healthcare settings are a frequent accompaniment to both routine procedures such as catheterization and surgical site interventions. Their impact is becoming even more marked as the numbers of medical devices that are used to manage chronic health conditions and improve quality of life increases. The resistance of pathogens to multiple antibiotics is also increasing, adding an additional layer of complexity to the problems of employing safe and effective medical procedures. One approach to reducing the rate of infections associated with implanted and indwelling medical devices is the use of polymers that resist the formation of bacterial biofilms. To significantly accelerate the discovery of such materials, we show how state of the art machine learning methods can generate quantitative predictions for the attachment of multiple pathogens to a large library of polymers in a single model for the first time. Such models facilitate design of polymers with very low pathogen attachment across different bacterial species that will be candidate materials for implantable or indwelling medical devices such as urinary catheters, cochlear implants, and pacemakers.

Catheter-Related Bloodstream Infections in Adults Receiving Home Parenteral Nutrition: Substantial Differences in Incidence Comparing a Strict Microbiological to a Clinically Based Diagnosis

BACKGROUND

A common complication in patients receiving home parenteral nutrition (HPN) is catheter-related bloodstream infections (CRBSIs). The CRBSI incidence has been advocated as an outcome parameter assessing the quality of care. This study aimed to illustrate how the use of different CRBSI definitions affects the reported incidence.

MATERIALS AND METHODS

In an observational study based on the Copenhagen intestinal failure database, all clinically reported CRBSIs from 2002-2013 were compared with data from the affiliated microbiological database according to recommended CRBSI criteria.

RESULTS

Clinically, 1034 CRBSIs were observed in 548 adults receiving HPN for 1410 catheter-years. Thus, the clinically assessed CRBSI incidence was 1.95/1000 catheter-days. However, based on the microbiological evaluation, only 47% of our episodes fulfilled the Centers for Disease Control and Prevention (CDC) and European Society for Clinical Nutrition (ESPEN) CRBSI criteria. Employing a catheter-salvaging strategy, 40% of the CRBSI diagnoses were supported by the paired blood culture positivity criteria and only 6% by a positive catheter tip. In 53%, CRBSIs were categorized as a clinical or "probable CRBSI" diagnosis. In 20% of all episodes, missing information/blood cultures hampered a CDC/ESPEN CRBSI diagnosis. Thereby, according to CDC/ESPEN CRBSI definitions, the incidence was 0.92/1000 days or 46% lower than clinically assessed.

CONCLUSION

This study illustrates the practical and methodological challenges and great variability in reporting of the CRBSI incidence. Nonetheless, it is recommended as a marker of the quality of care. Consensus regarding CRBSI definitions is a prerequisite for a meaningful comparison of this important outcome parameter between HPN centers.

Source Identification and Source Control

Identifying sources of infection and establishing source control is an essential component of the workup and treatment of sepsis. Investigation with history, physical examination, laboratory tests, and imaging can in identifying sources of infection. All organ systems have the potential to develop sources of infection. However, there are inherent difficulties presented by some that require additional diligence, namely, urinalysis, chest radiographs, and intraabdominal infections. Interventions include administration of antibiotics and may require surgical or other specialist intervention. This is highlighted by the Surviving Sepsis Campaign with specific recommendations for time to antibiotics and expeditious time to surgical source control.

Non-culture based diagnostics for intravascular catheter related bloodstream infections

INTRODUCTION

intravascular catheter related bloodstream infection (IVC-BSI) is a leading cause of nosocomial infections and associated with significant morbidity and mortality. Early detection and adequate treatment of causative pathogens is critical for a favourable outcome. However, it takes significant time to receive microbiological results due to the current reference diagnostic method's reliance on microbial growth. Areas covered: This review discusses culture and non-culture based techniques for the diagnosis of non IVC-BSI and IVC-BSI, including molecular methods and biomarkers. Different diagnostic strategies are evaluated and the potential of new generation of diagnostic assays highlighted. Expert commentary: The development of additional diagnostic methods has potential to beneficially supplement conventional culture diagnosis, and molecular techniques have particular potential to fulfil this need. They would also contribute significant new knowledge on the bacterial species present on catheters that are generally missed by diagnosis using traditionally culture-dependent methods. Advances in molecular strategies, together with new biomarkers, might lead to the development of faster, more sensitive and cheaper technologies and instruments. This review aims to provide a platform for the further development of IVCBSI diagnostic techniques.

Risk factors for early onset of catheter-related bloodstream infection in an intensive care unit in China: a retrospective study

Background

Catheter-related bloodstream infection (CRBSI) is a life-threatening condition encountered in patients with long-term central venous catheter (CVC) indwelling. The objective was to investigate the clinical characteristics, treatment, and prognosis of CRBSI in the intensive care unit (ICU) in a Chinese center, as well as the risk factors for early CRBSI.

Material/Methods

A total of 73 CRBSI patients were retrospectively studied in relation to patients’ clinical and epidemiological data, microbiological culture, and treatment. Patients were treated at the Taizhou Hospital of Integrated Traditional Chinese and Western Medicine in Zhejiang (Zhejiang Wenlin, China) between January 2010 and December 2012.

Results

In this Chinese center, the most common pathogens were Gram-positive cocci, followed by Gram-negative bacilli and fungi. A high prevalence of antibiotic-resistant pathogens was detected, and a higher percentage of non-Candida albicans spp. was observed. Multivariate analysis showed that an acute physiology and chronic health evaluation II (APACHE II) score >20 and >3 types of underlying diseases were independent factors associated with CRBSI occurring within 14 days of CVC indwelling. Untimely CVC removal and/or inappropriate use of antibiotics led to significantly longer time to defervescence and time to negative conversion of blood culture (all P<0.05).

Conclusions

In this Chinese center, Gram-positive bacteria are predominantly detected in CRBSI. APACHE II score >20 and the presence of >3 types of diseases were associated with earlier CRBSI onset. Timely removal of CVC and appropriate use of antibiotics resulted in improved outcomes.

The expanding horizon of prosthetic joint infections

Prosthetic joint infection (PJI) is a serious and potentially devastating complication of arthroplasty. Prior arthroplasty, immunosuppression, severe comorbid conditions, and prolonged surgical duration are important risk factors for PJI. More than half of the cases of PJI are caused by Staphylococcus aureus and coagulase-negative staphylococci. The biofilm plays a central role in its pathogenesis. The diagnosis of PJI requires the presence of purulence, sinus tract, evidence of inflammation on histopathology, or positive microbiologic cultures. The use of diagnostic imaging techniques is generally limited but may be helpful in selected cases. The most effective way to prevent PJI is to optimize the health of patients, using antibiotic prophylaxis in a proper and timely fashion. Management of PJI frequently requires removal of all hardware and administration of intravenous antibiotics. This review summarizes and analyzes the results of previous reports of PJI and assesses the prevention and management of this important entity.

Investigation of the case numbers of catheter-related bloodstream infection overestimated by the central line-associated bloodstream infection surveillance definition

BACKGROUND/PURPOSE

Diagnosis of catheter-related bloodstream infection (CRBSI) requires specific laboratory evidence. A simpler definition, central line-associated bloodstream infection (CLABSI), is recommended for surveillance purposes. Because exclusion of all other infection sources is difficult, CRBSI cases may be overestimated by using the CLABSI definition.

METHODS

A retrospective observational study was performed at a regional hospital in southern Taiwan from September 2012 to December 2013. All 106 reported CLABSI cases were assessed. Cases with catheter tip cultures were reviewed. CRBSI was defined as the identification of same organisms from the paired blood and catheter tip cultures (≥15 colony-forming units) without evidence of secondary bacteremia from other infection sources.

RESULTS

Overall, 64 cases were included and 31 (48.4%) were defined as CRBSI cases. In 30 (46.9%) cases, catheter tips were cultured after the corresponding blood cultures were performed. Later tip cultures were significantly more frequent in cases with other catheter types (18/22, 81.8%) than those with central lines (12/42, 28.6%; p < 0.0001). The same significant difference was also found among the CRBSI cases (central lines, 3/17, 17.6%; others, 13/14, 92.9%; p < 0.00005). Twelve bacterial species were identified from the CRBSI cases, with Staphylococcus aureus being the most frequent (13, 41.9%), followed by Pseudomonas aeruginosa (5, 16.1%).

CONCLUSION

The positive predictive value of the CLABSI definition for CRBSI cases was 48.4%. One should be aware of this discrepancy and should interpret the CLABSI surveillance definition with care.

Antifouling polyurethanes to fight device-related staphylococcal infections: synthesis, characterization, and antibiofilm efficacy

In hospital settings, biofilm-based medical device-related infections are considered a threat to patients, the sessile growing bacteria playing a key role in the spreading of healthcare-associated infections. In recent decades, the design of antifouling coatings for medical devices able to prevent microbial adhesiveness has emerged as one of the most promising strategies to face this important issue. In order to obtain suitable antifouling materials, segmented polyurethanes characterized by a hard/soft domain structure, having the same hard domain but a variable soft domain, have been synthesized. The soft domain was constituted by one of the following macrodiols: polypropylenoxide (PPO), polycaprolactide (PCL), and poly-l-lactide (PLA). The effects of the polymer hydrophilicity and the degree of hard/soft domain separation on antifouling properties of the synthesized polyurethanes were investigated. Microbial adherence assays evidenced as the polymers containing PCL or PLA were able to significantly reduce the adhesion of Staphylococcus epidermidis with respect to the PPO-containing polymer.

Bloodstream infection in patients with end-stage renal disease in a teaching hospital in central-western Brazil

INTRODUCTION

Vascular access in patients undergoing hemodialysis is considered a critical determinant of bloodstream infection (BSI) and is associated with high morbidity and mortality. The purpose of this study was to investigate the occurrence of BSI in patients with end-stage renal disease using central venous catheters for hemodialysis.

METHODS

A cohort study was conducted in a public teaching hospital in central-western Brazil from April 2010 to December 2011. For every patient, we noted the presence of hyperemia/exudation upon catheter insertion, as well as fever, shivering, and chills during hemodialysis.

RESULTS

Fifty-nine patients were evaluated. Thirty-fi ve (59.3%) patients started dialysis due to urgency, 37 (62.7%) had BSI, and 12 (20%) died. Hyperemia at the catheter insertion site (64.9%) was a significant clinical manifestation in patients with BSI. Statistical analysis revealed 1.7 times more cases of BSI in patients with hypoalbuminemia compared with patients with normal albumin levels. The principal infective agents identified in blood cultures and catheter-tip cultures were Staphylococcus species (24 cases), non-fermentative Gram-negative bacilli (7 cases of Stenotrophomonas maltophilia and 5 cases of Chryseobacterium indologenes), and Candida species (6). Among the Staphylococci identified, 77.7% were methicillin-resistant, coagulase-negative Staphylococci. Of the bacteria isolated, the most resistant were Chryseobacterium indologenes and Acinetobacter baumannii.

CONCLUSIONS

Blood culture was demonstrated to be an important diagnostic test and identified over 50% of positive BSI cases. The high frequency of BSI and the isolation of multiresistant bacteria were disturbing findings. Staphylococcus aureus was the most frequently isolated microorganism, although Gram-negative bacteria predominated overall. These results highlight the importance of infection prevention and control measures in dialysis units.

Platelets as immune cells in infectious diseases

Platelets have been shown to cover a broad range of functions. Besides their role in hemostasis, they have immunological functions and thus participate in the interaction between pathogens and host defense. Platelets have a broad repertoire of receptor molecules that enable them to sense invading pathogens and infection-induced inflammation. Consequently, platelets exert antimicrobial effector mechanisms, but also initiate an intense crosstalk with other arms of the innate and adaptive immunity, including neutrophils, monocytes/macrophages, dendritic cells, B cells and T cells. There is a fragile balance between beneficial antimicrobial effects and detrimental reactions that contribute to the pathogenesis, and many pathogens have developed mechanisms to influence these two outcomes. This review aims to highlight aspects of the interaction strategies between platelets and pathogenic bacteria, viruses, fungi and parasites, in addition to the subsequent networking between platelets and other immune cells, and the relevance of these processes for the pathogenesis of infections.

Association between prehospital vitamin D status and hospital-acquired bloodstream infections

BACKGROUND

Alterations in immune function can predispose patients to nosocomial infections. Few studies have explored potentially modifiable host factors that may improve immune function and decrease risk of hospital-acquired bloodstream infection (HABSI). Vitamin D is a key regulator of innate and adaptive immune systems that may influence host susceptibility to infections.

OBJECTIVE

We investigated the association between prehospital serum 25-hydroxyvitamin D [25(OH)D] concentrations and risk of HABSI.

DESIGN

We performed a retrospective cohort study of 2135 adult patients from 2 Boston teaching hospitals. All patients had 25(OH)D concentrations measured before hospitalization between 1993 and 2010. The main outcome measure was HABSI, which was defined as positive blood cultures from samples drawn 48 h after hospital admission. Coagulase-negative Staphylococcus isolates were not considered to be bloodstream infections. Associations between 25(OH)D groups and HABSI were estimated by using bivariable and multivariable logistic regression models. Adjusted ORs were estimated with the inclusion of covariate terms thought to plausibly interact with both 25(OH)D concentration and HABSI.

RESULTS

Compared with patients with 25(OH)D concentrations ≥30 ng/mL, patients with concentrations <30 ng/mL had higher odds of HABSI. For 25(OH)D concentrations <10 ng/mL, the OR was 2.33 (95% CI: 1.45, 3.74); for 25(OH)D concentrations from 10 to 19.9 ng/mL, the OR was 1.60 (95% CI: 1.04, 2.46); and for 25(OH)D concentrations from 20 to 29.9 ng/mL, the OR was 1.13 (95% CI: 0.69, 1.84). After adjustment for age, sex, race (nonwhite compared with white), patient type (medical compared with surgical), and Deyo-Charlson index, the ORs of HABSI were 1.95 (95% CI: 1.22, 3.12), 1.36 (95% CI: 0.89, 2.07), and 0.98 (95% CI: 0.60, 1.62), respectively.

CONCLUSIONS

The analysis of 2135 adult patients showed that 25(OH)D concentrations <10 ng/mL before hospitalization were associated with significantly increased odds of developing HABSI. These data support the initiation of randomized trials to test the role of vitamin D supplementation in HABSI prevention.