Predicting mortality in burn patients with bacteraemia

Challenges Facing Two Outbreaks of Carbapenem-Resistant Acinetobacter baumannii: From Cefiderocol Susceptibility Testing to the Emergence of Cefiderocol-Resistant Mutants

Carbapenem-resistant Acinetobacter baumannii (CRAB) infections are associated with poor outcomes depending on patient's conditions, clinical severity and type of infection, and treatment is challenging given the limited therapeutic options available. The aim of this study was to describe the clinical and microbiological characteristics of two outbreaks caused by CRAB in an intensive care unit (ICU). In addition, the mechanisms of resistance detected in these strains and the treatment chosen according to the available therapeutic options were analyzed. Overall, 28 patients were included. Ten patients (35.71%) had ventilator-associated pneumonia (VAP), ten (35.71%) had a bloodstream infection (BSI), and eight (28.57%) were only colonized. Recurrent infection occurred in 25% (5/20) of infected patients. Two different strains of A. baumannii were isolated from the index patient of the first outbreak. The first strain belonged to the ST85 and carried the blaNDM-1 carbapenemase gene, while the second belonged to the ST2 and carried blaOXA-23, and blaOXA-66 carbapenemase genes. The phylogenetic analysis revealed that the ST2 strain was the cause of the major outbreak, and mutations in the AmpC gene were related to progressive increasing minimum inhibitory concentration (MIC) and finally, cefiderocol-resistance in one strain. The CRAB isolates from the second outbreak were also identified as ST2. Cefiderocol-resistant strains tests identified by the disc diffusion method were involved in 24% (6/25) of nosocomial infections. Using broth microdilution (BMD) ComASP® only, 33.3% (2/6) of these strains were cefiderocol-resistant. All-cause ICU mortality was 21.4%. Conclusions: Cefiderocol is the first approved siderophore cephalosporin for the treatment of CRAB infections. Cefiderocol-resistant strains were related with blaNDM-1 carbapenemase and mutations in the AmpC gene. Cefiderocol-resistant strains or that cannot be properly interpreted by disk diffusion, should be retested using BMD for definitive categorization.

Epidemiology and clinical significance of persistent bacteremia in severely burned patients

BACKGROUND

The utility of follow-up blood cultures (FUBC) for gram-negative bloodstream infections (BSIs) are controversial due to low rates of positivity. However, recent studies suggest higher rates of positivity in critically ill patients. The utility of FUBC in gram-negative BSI in patients with severe burn injuries is unknown.

METHODS

Patients ≥ 18 years old admitted to the US Army Institute of Surgical Research Burn Center for combat-related thermal burns from 1/2003-6/2014 with a monomicrobial BSI were included. FUBC were defined as repeat cultures 1-5 days from index BSI. Persistent BSI (pBSI) was defined as isolation of the same organism from initial and FUBC. The primary endpoint was all-cause in-hospital mortality in patients with gram-negative pBSI.

RESULTS

Of 126 patients meeting inclusion criteria with BSI, 53 (42%) had pBSI. Compared to patients without persistence, patients with pBSI had more severe burns with median total body surface area (TBSA) burns of 47% ([IQR 34-63] vs. 35.3% [IQR 23.3-56.6], p = 0.02), increased mortality (38 vs. 11%, p = 0.001) compared to those with non-persistent BSI. On multivariate analysis, pBSI was associated with an odds ratio for mortality of 5.3 [95% CI 1.8-15.8, p = 0.003). Amongst gram-negative pathogens, persistence rates were high and associated with increased mortality (41% vs. 11%, p = 0.001) compared to patients without pBSI.

CONCLUSION

In this cohort of military patients with combat-related severe burns, pBSI was more common than in other hospitalized populations and associated with increased mortality. Given this high frequency of persistence in patients with burn injuries and associated mortality, FUBC are an important diagnostic and prognostic study in this population.

Modified Nutrition Risk in Critically ill is an effective nutrition risk screening tool in severely burned patients, compared with Nutrition Risk Screening 2002

Objective

The present study aimed to evaluate the value of Modified Nutrition Risk in Critically ill (mNUTRIC) and Nutrition Risk Screening 2002 (NRS2002) in the prognosis of severely burned patients.

Methods

The retrospective cohort study used medical data of severely burned patients admitted to the burn center of Shanghai Ruijin Hospital between January 2015 and September 2021. Demographics, clinical characteristics, laboratory nutritional indicators, mNUTRIC score and NRS2002 score were collected and analyzed in evaluation the value of two nutrition risk screening tools. Spearman correlation analysis was carried out to show the correlation between variables. The area under receiver operating characteristic (ROC) curve was used to assess the ability of mNUTRIC and NRS2002 to predict mortality. Kaplan-Meier survival curves and log-rank tests were conducted to compare the overall survival (OS). Multivariate Cox proportional hazard regression model was used to identify risk factors for 28-day mortality of severely burned patients.

Results

A total of 429 adult patients with burn area larger than 30% total body surface area (TBSA) were included in this study. Incidence of nutrition risk was detected in 52.21% by mNUTRIC and 20.51% by NRS2002. However, mNUTRIC was superior to NRS2002 in predicting 28-day mortality (area under ROC curve: 0.795 vs. 0.726). Multivariate Cox regression analysis showed that high mNUTRIC [hazard ratio (HR) = 4.265, 95% CI = 1.469-12.380, P = 0.008] and TBSA (HR = 1.056, 95% CI = 1.033-1.079, P < 0.001) were independent predictors for 28-day mortality. After adjusting for covariates, high NRS2002 was not associated with 28-day mortality (P = 0.367).

Conclusion

The present study illustrated the effectiveness of mNUTRIC as nutrition risk screening tool among severely burned patients. Early identification of nutrition risk may help to maximize benefits of nutritional therapy by providing more aggressive nutritional therapy for patients at nutrition risk.

Murine burn lesion model for studying acute and chronic wound infections

Acute wounds, such as thermal injury, and chronic wounds are challenging for patients and the healthcare system around the world. Thermal injury of considerable size induces immunosuppression, which renders the patient susceptible to wound infections, but also in other foci like the airways and urinary tract. Infected thermal lesions can progress to chronic wounds with biofilm making them more difficult to treat. While animal models have their limitations, murine wound models are still the best tool at the moment to identify strategies to overcome these challenges. Here, we present a murine burn model, which has been developed to study biofilm formation, the significance of wound healing, and for identifying novel treatment candidates. Investigating the effect of a thermal injury in mice, we observed that 48 h after introduction of the injury, the mice showed a reduction in polymorphonuclear neutrophil granulocytes (PMNs) and a reduced capacity for phagocytosis and oxidative burst. Regarding the chronic wound, Pseudomonas aeruginosa biofilm arrested wound healing and kept the wound in an inflammatory state, but suppressing PMN function by means of the PMN factor S100A8/A9, corresponding to observations in human venous leg ulcers. Monotherapy and dual treatment with S100A8/A9 and ciprofloxacin on P. aeruginosa biofilm-infected murine wounds have been investigated. In combination, S100A8/A9 and ciprofloxacin reduced the bacterial quantity, lowered the proinflammatory response, and increased anti-inflammatory cytokines after 4 days of treatment. When the treatment was prolonged, an additional prevention of resistance development was detected in all the dual-treated mice. In the present review, we provide data on using the murine model for research with the aim of better understanding pathophysiology of wounds and for identifying novel treatments for humans suffering from these lesions.

Potential of lytic bacteriophages as disinfectant to control of Pseudomonas aeruginosa on fomites

PURPOSE

Nosocomial infections can be transmitted by contaminated hospital surfaces with resistant pathogens. Pseudomonas aeruginosa (P. aeruginosa) is an opportunistic pathogen that causes public healthcare issues. Conventional sanitation is not efficiently contributing to removing resistant pathogens. Bacteriophages suggest safe and specific decontamination. Bacteriophages are a promising alternative strategy to chemical biocides. This research aimed to evaluate the potential of phage in controlling P. aeruginosa in infected hard surfaces.

METHODS

Bacteriophage was isolated from hospital wastewater. The efficiency lytic activity of phage against P. aeruginosa was assessed on various infected hard surfaces as plastic and ceramic. 50 µl of the phage lysate (2 × 10¹² PFU/mL) and 50 µl of 70% Ethanol solution separately were spread on the different infected surfaces. After 15 min, 1, 3, 6, and 24 h, surfaces were directly sampled by contact plates. The bacterial load was evaluated by enumerating plate CFU.

RESULTS

Cystoviridae phages with titer (2 × 10¹² PFU/mL) efficiently can reduce P. aeruginosa on contaminated surfaces. The treated surfaces with 70% Ethanol solution and phage showed an evident drop in bacterial cell number.

CONCLUSIONS

Bacteriophages can be used as a new option for the development of biological products aimed at the control and deletion of pathogens on contaminated hard surfaces.

Application of mNGS to describe the clinical and microbial characteristics of severe burn a tanker explosion at a tertiary medical center: a retrospective study patients following

Background

Multiple organ dysfunction syndrome secondary to infection is the leading cause of death in burn patients. Bloodstream infection (BSI) and the prognosis of burn patients are negatively correlated. Metagenomic next-generation sequencing (mNGS) can detect many potential pathogens and may be more valuable for patients with severe burns.

Methods

We retrospectively explored the utility of mNGS in describing the clinical and microbial characteristics of severely burned patients with BSI. We compared mNGS with blood culture.

Results

Fourteen patients (127 blood samples) developed 71 episodes of BSIs with 102 unique causative pathogens. The median total body surface area was 93%. The overall 90-day mortality was 43%. In total, 17 (23.9%) episodes were polymicrobial, and 61 (86.1%) episodes originated from the wound. In total, 62/71 cases (87%) showed positive findings by mNGS, while 42/71 cases (59%) showed positive findings using blood culture. We found that mNGS outperformed culture, especially in terms of fungi (27% vs. 6%, p < 0.0001).

Conclusions

The incidence of BSI and polymicrobial in patients with large-area severe burns is high. mNGS has potential value in the diagnosis of fungal infections and coinfections in such patients. In addition, mNGS may provide unique guidance for antibiotic therapy in complicated BSI.

Trichoderma longibrachiatum and Aspergillus fischeri Infection as a Cause of Skin Graft Failure in a Patient with Critical Burns after Liver Transplantation

Infectious complications are responsible for the majority of mortalities and morbidities of patients with critical burns. Although bacteria are the predominant etiological agents in such patients, yeasts and fungi have become relatively common causes of infections over the last decade. Here, we report a case of a young man with critical burns on 88% TBSA (total body surface area) arising as a part of polytrauma. The patient's history of orthotopic liver transplantation associated with the patient's need to use combined immunosuppressant therapy was an additional complication. Due to deep burns in the forearm region, we have (after a suitable wound bed preparation) applied a new bi-layered dermal substitute. The patient, however, developed a combined fungal infection in the region of this dermal substitute caused by Trichoderma longibrachiatum and Aspergillus fischeri (the first case ever reported). The infection caused the loss of the split-thickness skin grafts (STSGs); we had to perform repeated hydrosurgical and mechanical debridement and a systemic antifungal treatment prior to re-application of the STSGs. The subsequent skin transplant was successful.

Pseudomonas aeruginosa device associated - healthcare associated infections and its multidrug resistance at intensive care unit of University Hospital: polish, 8.5-year, prospective, single-centre study

BACKGROUND

Pseudomonas aeruginosa has recently shown to be one of the most important strains of bacteria and alert pathogens in Europe among Intensive Care Unit patients that provide serious therapeutic problems because of its multidrug resistance.

METHODS

The purpose of this microbiological study was data analysis of device associated- healthcare associated infections (DA-HAIs) in an ICU in terms of the incidents of P.aeruginosa strain infections and its susceptibility within an 8.5-year observation.

RESULTS

Among 919 isolated strains responsible for 799 DA-HAIs (17,62 ± 1,98/1000 patient-days) in 4010 ICU patients P.aeruginosa was the pathogen in 108/799 (13.52%) cases. Incidence rate (density) of: VAP/1000 MV- days, UTI /1000 UC- days and CLA-BSI/1000 CL- days were 11,15 ± 2.5, 6.82 ± 0.81, 2.35 ± 1.54.respectivelly. P.aeruginosa was the pathogen most frequently responsible for VAP 69/108 (63.88%). Mean frequency of VAP, UTI and CLA-BSI with P.aeruginosa etiology was 69/493 (14.28%), 32/299 (11.1%) and 7/127 (5.77%) respectively. The mean density of P.aeruginosa infection amounted to 2.43/1000 patient-days. The decrease was observed in the total number of DA-HAIs caused by the P.aeruginosa from 15.75% and 3.23/1000 patient-days in 2011 to 5.0% and 1.17/1000 in 2016 (p = 0.0104, p = 0.0348). Starting from 2016 to 2019 incidence and density of P.aeruginosa DA-HAIs increased to 12.33% and 2.63/1000 (p = 0.1388, p = 0.0818). P.aeruginosa was susceptible to ceftazidime, cefepime, amikacin, meropenem, ciprofloxacin, colistin, in 55.55, 58.33, 70.37, 53.73, 50, and 100% respectively. MDR characterised it in 40% in 2011 and 66.7% in 2019, (p = 0.177).

CONCLUSIONS

The study revealed a changeable prevalence of P. aeruginosa strain infections; however their frequency was never highest in our ICU patients as it presented in the last years in Europe. The study showed a significant decrease in 2016 and increase in 2019, a nearly 3-fold increase of P.aeruginosa infections among Gram-negative strain infections, and a 2-fold increase of the P.aeruginosa DA-HAIs frequency between 2016 and 2019 as well as an increased resistance. Microbiological analysis of DA-HAIs in each hospital should be a standard method used in hospital infection control and antibiotic policy. In the case of P.aeruginosa, in order to minimize transmission, preventive infection methods should be assessed mainly in case of VAP.

Outcomes in Burn-Injured Patients Who Develop Sepsis

This study examines health outcomes in burn patients with sepsis. We hypothesized that burn patients with sepsis would have an increased odds risk for in-hospital death and longer intensive care unit (ICU) stays. This was a retrospective cohort of consecutive patients admitted to the burn ICU with total BSA (TBSA) ≥10% and/or inhalation injury between January 2008 and March 2015. Overall 407 burn patients were included; the case-rate for sepsis was 39.1% (n = 159); 20.1% (n = 82) patients were septic and 18.9% (n = 77) patients experienced septic shock. Patients with septic shock had the highest mortality rate (13.31% no sepsis vs 3.7% sepsis vs 49.4% septic shock, P < .01). Median 28-day ICU-free days was higher in patients without sepsis (23 days [Interquartile range (IQR) 14-27] no sepsis vs 0 days [IQR 0-10] sepsis vs 0 days [IQR 0-0] septic shock, P < .01). Sepsis (with or without shock) increased odds of in-hospital death (odds ratio 7.04, 95% confidence interval 1.93-25.7) in reference to the no sepsis group. With each incremental Sequential Organ Failure Assessment (SOFA) score or 10% TBSA increase, the odds risk for in-hospital death increased by 56 and 75%, respectively. Our study characterized outcomes in patients with sepsis after severe burn injury. The odds risk for in-hospital death was greater in patients with sepsis, increasing burn severity according to TBSA and SOFA score.

Difficult to Treat Infections in the Burn Patient

Background: Unusual infections can lead to complications in more severely burned patients and pose major challenges in treatment. Methods: The published literature of retrospective reviews and case series of the uncommon infections of osteomyelitis, polymicrobial bacteremia, recurrent bacteremia, endocarditis, central nervous system (CNS), and rare fungal infections in burned patients have been summarized and presented. Results: When compared with infections occurring in the non-burn population, these infections in burn patients are more likely to be because of gram-negative bacteria or fungi. Because of hyperdynamic physiology and changes in immunomodulatory response secondary to burns, the clinical presentation of these infections in a patient with major burns differs from that of the non-burn patient and may not be identified until the post-mortem examination. Some of these infections (osteomyelitis, endocarditis, CNS, rare fungal infections) may necessitate surgical intervention in addition to antimicrobial therapy to achieve cure. The presence of the burn and allograft can also present unique challenges for surgical management. Conclusions: These difficult and unusual infections in the severely burned patient necessitate an index of suspicion, appropriate diagnosis, identification and sensitivities of the putative pathogen, effective systemic antimicrobial therapy, and appropriate surgical intervention if recovery is to be achieved.

Bacterial infection profile and predictors among patients admitted to a burn care center: A retrospective study

BACKGROUND

Infection is the main cause of mortality and complications in burn patients. The present study was the first to examine the local profile and antecedents of bacterial infections among patients admitted to a Lebanese burn care center.

METHODS

The present study was a retrospective analysis of the occurrence and recurrence of infection, its characteristics as well as antimicrobial susceptibility among 475 patients admitted to the Burn Centre at the Lebanese Geitaoui Hospital between January 2014 and December 2018.

RESULTS

55% of patients contracted at least one infection during their hospitalization. Length of stay (LOS), sepsis, wound dressing under anesthesia, blood transfusion and female sex independently and positively predicted infection in burn patients. Infection was predominately caused by Staphylococcus aureus (48.7%), followed by Pseudomonas aeruginosa (22.6%) and Acinetobacter baumannii (15.7%). Bacterial isolates were predominately multi-drug or extensively drug resistant and showed variable antimicrobial susceptibility patterns. Recurrent infections occurred in 44.1% of infected burn patients, and were independently predicted by LOS (p = 0.004), sepsis (p = 0.001), surgery (p = 0.003), burn excision and skin grafting (p = 0.019), and central line insertion (p = 0.004).

CONCLUSION

Existing burn management and infection control measures must be revised in order to reduce the incidence and improve the treatment of infections in burn patients.

Survival analysis and mortality predictors of hospitalized severe burn victims in a Malaysian burns intensive care unit

Background

Prognostic measures to determine burn mortality are essential in evaluating the severity of individual burn victims. This is an important process of triaging patients with high risk of mortality that may be nursed in the acute care setting. Malaysian burn research is lacking with only one publication identified which describes the epidemiology of burn victims. Therefore, the objective of this study was to go one step further and identify the predictors of burn mortality from a Malaysian burns intensive care unit (BICU) which may be used to triage patients at higher risk of death.

Methods

This is a retrospective cohort study of all admissions to Hospital Sultan Ismail’s BICU from January 2010 till October 2015. Admission criteria were in accordance with the American Burn Association guidelines, and risk factors of interest were recorded. Data was analyzed using simple logistic regression to determine significant predictors of mortality. Survival analysis with time to death event was performed using the Kaplan-Meier survival curve with log-rank test.

Results

Through the 6-year period, 393 patients were admitted with a male preponderance of 73.8%. The mean age and length of stay were 35.6 (±15.72) years and 15.3 (±18.91) days. There were 48 mortalities with an overall mortality rate of 12.2%. Significant risk factors identified on simple logistic regression were total body surface area (TBSA) > 20% (p < 0.001), inhalation injury (p < 0.001) and presence of early systemic inflammatory response syndrome (SIRS) (p < 0.001). Survival analysis using Kaplan-Meier survival curve showed similar results with TBSA > 20%, presence of SIRS, mechanical ventilation and inhalation injury which were associated with poorer survival (p < 0.001).

Conclusion

The predictors of mortality identified in a Malaysian BICU were TBSA > 20%, early SIRS, mechanical ventilation and inhalation injury which were associated with poorer survival outcome. The immunological response differs from individual patients and influenced by the severity of burn injury. Early SIRS on admission is an important predictor of death and may represent the severity of burn injury. Patients who required mechanical ventilation were associated with mortality and it is likely related to the severity of pulmonary insults sustained by individual patients. This data is important for outcome prognostication and mortality risk counselling in severely burned patients.

Progress Toward the Elusive Pseudomonas aeruginosa Vaccine

Background: The gram-negative bacterial pathogen Pseudomonas aeruginosa causes a wide range of infections, mostly in hospitalized and immunocompromised patients, those with burns, surgical wounds, or combat-related wounds, and in people with cystic fibrosis. The increasing antibiotic resistance of P. aeruginosa confers a pressing need for vaccines, yet there are no P. aeruginosa vaccines approved for human use, and recent promising candidates have failed in large clinical trials. Discussion: In this review, we summarize recent clinical trials and pre-clinical studies of P. aeruginosa vaccines and provide a suggested framework for the makeup of a future successful vaccine. Murine models of infection suggest that antibodies, specifically opsonophagocytic killing antibodies (OPK), antitoxin antibodies, and anti-attachment antibodies, combined with T cell immunity, specifically T_H17 responses, are needed for broad and potent protection against P. aeruginosa infection. A better understanding of the human immune response to P. aeruginosa infections, and to vaccine candidates, will eventually pave the way to a successful vaccine for this wily pathogen.

Rose Bengal-Mediated Photoinactivation of Multidrug Resistant Pseudomonas aeruginosa Is Enhanced in the Presence of Antimicrobial Peptides

Due to the overuse of antibiotics in medicine and food production, and their targeted mechanism of action, an increasing rate in spreading of antibiotic resistance genes has been noticed. This results in inefficient therapy outcomes and higher mortality all over the world. Pseudomonas aeruginosa (carbapenem-resistant) is considered one of the top three critical species according to the World Health Organization’s priority pathogens list. This means that new drugs and/or treatments are needed to tackle infections caused by this bacterium. In this context search for new/alternative approaches that would overcome resistance to classical antimicrobials is of prime importance. The use of antimicrobial photodynamic inactivation (aPDI) and antimicrobial peptides (AMPs) is an efficient strategy to treat localized infections caused by multidrug-resistant P. aeruginosa. In this study, we have treated P. aeruginosa cells photodynamically in the presence and in the absence of AMP (CAMEL or pexiganan). The conditions for aPDI were as follows: rose bengal (RB) as a photosensitizing agent at 1–10 μM concentration, and subsequent irradiation with 514 nm-LED at 23 mW/cm² irradiance. The analysis of cell number after the treatment has shown that the combined action of RB-mediated aPDI and cationic AMPs reduced the number of viable cells below the limit of detection (<1log₁₀ CFU/ml). This was in contrast to no reduction or partial reduction after aPDI or AMP applied separately. Students t-test was applied to test the statistical significance of the results. Noteworthy, our treatment proved to be effective against all 35 clinical isolates of P. aeruginosa tested within this study, including those characterized as multiresistant. Moreover, we demonstrated that such treatment is safe and does not violate the growth dynamics of human keratinocytes (77.3–97.64% survival depending on the concentration of the studied compounds or their mixtures).

Epidemiology and outcomes of bloodstream infections in 177 severe burn patients from an industrial disaster: a multicentre retrospective study

OBJECTIVES

To determine the characteristics of bloodstream infections (BSIs) and to evaluate the impact of BSIs on mortality in severe burn patients.

METHODS

A retrospective observational study was conducted in 20 tertiary hospitals. A total of 185 patients who experienced a massive dust explosion in eastern China were included.

RESULTS

After exclusion, 177 patients were analysed. The median total body surface area (TBSA) burned was 95% (interquartile range 85%-98%). Inhalation injuries occurred in 97.2%. The overall 90-day mortality was 35% (62/177). During the study period, 120 (67.8%) patients developed 253 episodes of BSI with 323 unique causative pathogens. Sixty-six episodes were polymicrobial infections. Catheter-related BSIs (CRBSIs) accounted for 41.5% of the episodes. Acinetobacter baumannii (19.5%), Klebsiella pneumoniae (13.9%) and Candida (12.7%) were the most common organisms. Antimicrobial resistance was found in 63.5% of the isolates, particularly in Gram-negative bacteria. Patients who developed BSIs had a greater illness severity at admission to the intensive care unit, and worse outcomes. After adjusting for demographics, severity of illness and treatment characteristics in a multivariate logistic model, there was a trend toward BSI increasing the risk of 90-day mortality (adjusted OR 3.4; 95% CI 0.9-12.9; p=0.069). In subgroup analyses, CRBSIs (adjusted OR 5.7; 95% CI 1.3-24.9; p=0.021 versus no BSI) and polymicrobial BSIs (adjusted OR 6.1; 95% CI 1.3-28.1; p=0.020 versus no BSI) had greater risk of 90-day mortality.

CONCLUSIONS

A strikingly high rate of BSIs was observed in severe burn patients. Gram-negative organisms and fungi were the leading causes. CRBSIs and polymicrobial BSIs were associated with high mortality.