Association of secondary and polymicrobial nosocomial bloodstream infections with higher mortality

Clinical evaluation of a multiplex droplet digital PCR for pathogen detection in critically ill COVID-19 patients with bloodstream infections

BACKGROUND

Nosocomial bloodstream infections (nBSI) have emerged as a clinical concern for physicians treating COVID-19 patients. In this study, we aimed to evaluate the effectiveness of a multiplex ddPCR in detecting bacterial pathogens in the blood of COVID-19 critically ill patients.

METHODS

This prospective diagnostic study included RT-PCR-confirmed COVID-19 patients admitted to our hospital from December 2022 to February 2023. A multiplex ddPCR assay was used to detect common bacterial pathogens and AMR genes in blood samples of the patients, along with antimicrobial susceptibility testing (AST). The diagnostic performance of the ddPCR assay was evaluated by comparing the results with those obtained through blood culture and clinical diagnosis. Additionally, the ability of ddPCR in detecting bacterial resistance was compared with the AST results.

RESULTS

Of the 200 blood samples collected from 184 patients, 45 (22.5%) were positive using blood culture, while 113 (56.5%) were positive for bacterial targets using the ddPCR assay. The ddPCR assay outperformed blood culture in pathogen detection rate, mixed infection detection rate, and fungal detection rate. Acinetobacter baumannii and Klebsiella pneumoniae were the most commonly detected pathogens in COVID-19 critically ill patients, followed by Enterococcus and Streptococcus. Compared to blood culture, ddPCR achieved a sensitivity of 75.5%, specificity of 51.0%, PPV of 30.9%, and NPV of 87.8%, respectively. However, there were significant differences in sensitivity among different bacterial species, where Gram-negative bacteria have the highest sensitivity of 90.3%. When evaluated on the ground of clinical diagnosis, the sensitivity, specificity, PPV and NPV of ddPCR were 78.1%, 90.5%, 94.7%, and 65.5%, respectively. In addition, the ddPCR assay detected 23 cases of blaKPC, which shown a better consistent with clinical test results than other detected AMR genes. Compared to blaKPC, there were few other AMR genes detected, indicating that the application of other AMR gene detection in the COVID-19 critically ill patients was limited.

CONCLUSION

The multiplex ddPCR assay had a significantly higher pathogen detection positivity than the blood culture, which could be an effective diagnostic tool for BSIs in COVID-19 patients and to improve patient outcomes and reduce the burden of sepsis on the healthcare system, though there is room for optimization of the panels used.- Adjusting the targets to include E. faecalis and E. faecium as well as Candida albicans and Candida glabrata could improve the ddPCR' s effectiveness. However, further research is needed to explore the potential of ddPCR in predicting bacterial resistance through AMR gene detection.

Treatment of Staphylococcus aureus and Candida albicans polymicrobial biofilms by phloroglucinol-gold nanoparticles

The co-isolation of Staphylococcus aureus and Candida albicans from host tissues and organs and their in vitro and in vivo interaction studies suggest a synergistic relationship in forming polymicrobial biofilms. In particular, during polymicrobial biofilm formation, S. aureus becomes coated in the extracellular matrix secreted by C. albicans, leading to enhanced resistance to antibiotics. Accordingly, understanding the interactions between S. aureus and C. albicans in polymicrobial biofilms is of utmost importance in establishing treatment strategies for polymicrobial infections. As an alternate technique, nanoparticles were used in this investigation to suppress polymicrobial biofilm. The current study aims to manufacture gold nanoparticles (AuNPs) using phloroglucinol (PG), a natural chemical, and test their inhibitory capabilities against S. aureus and C. albicans biofilms in standard and host-mimicking media (like saliva and sputum). PG-AuNPs have a spherical form with an average size of 46.71 ± 6.40 nm. The minimum inhibitory concentration (MIC) values differed when PG-AuNPs were evaluated in the standard and host-mimicking artificial media. The MIC of PG-AuNPs against S. aureus and C. albicans was 2048 μg/mL in both the standard and artificial sputum media. However, the MIC in saliva was only 128 μg/mL. The initial stage polymicrobial biofilm of S. aureus and C. albicans was dramatically decreased at the sub-MIC of PG-AuNPs in both standard and host-mimicking media. S. aureus and C. albicans mature polymicrobial biofilms were more effectively eliminated by MIC and sub-MIC of PG-AuNPs. This study indicates that PG-AuNPs have the ability to limit the formation of polymicrobial biofilms caused by bacterial and fungal diseases.

One population, multiple lifestyles: Commensalism and pathogenesis in the human mycobiome

Candida auris and Candida albicans can result in invasive fungal diseases. And yet, these species can stably and asymptomatically colonize human skin and gastrointestinal tracts. To consider these disparate microbial lifestyles, we first review factors shown to influence the underlying microbiome. Structured by the damage response framework, we then consider the molecular mechanisms deployed by C. albicans to switch between commensal and pathogenic lifestyles. Next, we explore this framework with C. auris to highlight how host physiology, immunity, and/or antibiotic receipt are associated with progression from colonization to infection. While treatment with antibiotics increases the risk that an individual will succumb to invasive candidiasis, the underlying mechanisms remain unclear. Here, we describe several hypotheses that may explain this phenomenon. We conclude by highlighting future directions integrating genomics with immunology to advance our understanding of invasive candidiasis and human fungal disease.

Microbiology and Clinical Outcome of Hospital-Acquired Respiratory Infections in an Italian Teaching Hospital: A Retrospective Study

The burden, microbial etiology and clinical impact of hospital-acquired respiratory infections (HARIs) were determined at an Italian teaching hospital over a 12-month period. For this purpose, overall ordinary hospitalizations ≥ 2 days of subjects over 18 years old with discharge from 1 January 2018 to 31 December 2018 were examined by cross-referencing demographic and clinical data from hospital discharge forms with microbiological data from the computer system of the Microbiology Unit. We identified 329 individuals with HARIs (96 females and 233 males; median age 70 years, range 18−93), who represented ¼ of the total hospital-acquired infections (HAIs) in the period. The inpatient setting was medical and surgical in similar proportions (169 vs. 160, respectively) and the mean hospital stay was 38.9 ± 33.6 days. One hundred and forty patients (42.6% of the total sample) were suffering from one or more chronic diseases. A total of 581 microorganisms (82 antibiotic-resistant and 499 non-resistant) were detected in HARI patients. The most common isolated species were Staphylococcus aureus (16.7%), Klebsiella pneumoniae (13.3%), Pseudomonas spp. (12.6%) and Acinetobacter baumannii (10.5%), followed by Enterobacter spp. (5.3%), Escherichia coli (5.2%) and Enterococcus spp. (4.8%). One hundred and sixty-seven individuals (49.0% of the total) had polymicrobial infections. One hundred thirty-one patients (39.8% of the total) underwent endotracheal intubation and mechanical ventilation and 62.6% of them died, compared to 17.7% of the non-intubated patients. Multivariable analysis confirmed a positive correlation between death and increased age (p = 0.05), surgical MDC (p = 0.007), number of microorganisms over the sample mean (p = 0.001), the presence of chronic diseases (p = 0.046), and intubation and mechanical ventilation (p < 0.0001). A positive correlation between intubation and antibiotic-resistant organisms (p = 0.003) was also found. HARIs are still a major public health problem and require constant surveillance due to their severe clinical outcome.

Postmortem Bacteriology in Forensic Autopsies—A Single Center Retrospective Study in Romania

Postmortem bacteriology examinations have been a controversial topic over the years, though the value of postmortem bacteriology cultures remains promising. The aim of this study was to review the postmortem bacteriological sampling procedures and results in a single centre in Bucharest over a period of 10 years. Material and methods: The present study was a retrospective, single-center study, performed at the Mina Minovici National Institute of Legal Medicine in Bucharest, Romania, from 2011–2020. Results: Postmortem bacteriology was requested 630 forensic autopsies, 245 female (38.9%) and 385 male (61.1%), age range 0 and 94 years, median age of 52 years. Deaths occurred in hospital for 594 cases (94.3%) and out-of-hospital for 36 cases (5.7%—field case). Blood cultures were requested in the majority of cases, followed by tracheal swabs and lung tissue. In-hospital and out of hospital deaths did not differ significantly regarding the number of microorganisms identified in a positive blood culture. Postmortem bacteriology cultures of the respiratory tract showed a statistically significant association to microscopically confirmed lung infections. Conclusions Postmortem sampling for bacteriology testing in our center in Bucharest is heterogeneous with a high variation of patterns. A positive blood culture result for Staphylococcus species without the identification of a specific microorganism is more likely due to postmortem contamination.

In Vitro Incorporation of Helicobacter pylori into Candida albicans Caused by Acidic pH Stress

Yeasts can adapt to a wide range of pH fluctuations (2 to 10), while Helicobacter pylori, a facultative intracellular bacterium, can adapt to a range from pH 6 to 8. This work analyzed if H. pylori J99 can protect itself from acidic pH by entering into Candida albicans ATCC 90028. Growth curves were determined for H. pylori and C. albicans at pH 3, 4, and 7. Both microorganisms were co-incubated at the same pH values, and the presence of intra-yeast bacteria was evaluated. Intra-yeast bacteria-like bodies were detected using wet mounting, and intra-yeast binding of anti-H. pylori antibodies was detected using immunofluorescence. The presence of the H. pylori rDNA 16S gene in total DNA from yeasts was demonstrated after PCR amplification. H. pylori showed larger death percentages at pH 3 and 4 than at pH 7. On the contrary, the viability of the yeast was not affected by any of the pHs evaluated. H. pylori entered into C. albicans at all the pH values assayed but to a greater extent at unfavorable pH values (pH 3 or 4, p = 0.014 and p = 0.001, respectively). In conclusion, it is possible to suggest that H. pylori can shelter itself within C. albicans under unfavorable pH conditions.

Effect of C-Reactive Protein-Guided Antibiotic Treatment Duration, 7-Day Treatment, or 14-Day Treatment on 30-Day Clinical Failure Rate in Patients With Uncomplicated Gram-Negative Bacteremia: A Randomized Clinical Trial

IMPORTANCE

Antibiotic overuse drives antibiotic resistance. Gram-negative bacteremia is a common infection that results in substantial antibiotic use.

OBJECTIVE

To compare the clinical effectiveness of C-reactive protein (CRP)-guided, 7-day, and 14-day antibiotic durations 30, 60, and 90 days after treatment initiation.

DESIGN, SETTING, AND PARTICIPANTS

Multicenter, noninferiority, point-of-care randomized clinical trial including adults hospitalized with gram-negative bacteremia conducted in 3 Swiss tertiary care hospitals between April 2017 and May 2019, with follow-up until August 2019. Patients and physicians were blinded between randomization and antibiotic discontinuation. Adults (aged ≥18 years) were eligible for randomization on day 5 (±1 d) of microbiologically efficacious therapy for fermenting, gram-negative bacteria in blood culture(s) if they were afebrile for 24 hours without evidence for complicated infection (eg, abscess) or severe immunosuppression.

INTERVENTION

Randomization in a 1:1:1 ratio to an individualized CRP-guided antibiotic treatment duration (discontinuation once CRP declined by 75% from peak; n = 170), fixed 7-day treatment duration (n = 169), or fixed 14-day treatment duration (n = 165).

MAIN OUTCOMES AND MEASURES

The primary outcome was the clinical failure rate at day 30, defined as the presence of at least 1 of the following, with a non-inferiority margin of 10%: recurrent bacteremia, local suppurative complication, distant complication (growth of the same organism causing the initial bacteremia), restarting gram-negative-directed antibiotic therapy due to clinical worsening suspected to be due to the initial organism, or death due to any cause. Secondary outcomes included the clinical failure rate on day 90 of follow-up.

RESULTS

Among 504 patients randomized (median [interquartile range] age, 79 [68-86] years; 306 of 503 [61%] were women), 493 (98%) completed 30-day follow-up and 448 (89%) completed 90-day follow-up. Median antibiotic duration in the CRP group was 7 (interquartile range, 6-10; range, 5-28) days; 34 of the 164 patients (21%) who completed the 30-day follow-up had protocol violations related to treatment assignment. The primary outcome occurred in 4 of 164 (2.4%) patients in the CRP group, 11 of 166 (6.6%) in the 7-day group, and 9 of 163 (5.5%) in the 14-day group (difference in CRP vs 14-day group, -3.1% [1-sided 97.5% CI, -∞ to 1.1]; P < .001; difference in 7-day vs 14-day group, 1.1% [1-sided 97.5% CI, -∞ to 6.3]; P < .001). By day 90, clinical failure occurred in 10 of 143 patients (7.0%) in the CRP group, 16 of 151 (10.6%) in the 7-day group, and 16 of 153 (10.5%) in the 14-day group.

CONCLUSIONS AND RELEVANCE

Among adults with uncomplicated gram-negative bacteremia, 30-day rates of clinical failure for CRP-guided antibiotic treatment duration and fixed 7-day treatment were noninferior to fixed 14-day treatment. However, interpretation is limited by the large noninferiority margin compared with the low observed event rate, as well as low adherence and wide range of treatment durations in the CRP-guided group.

TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT03101072.

"It Takes a Village": Mechanisms Underlying Antimicrobial Recalcitrance of Polymicrobial Biofilms

Chronic infections are frequently caused by polymicrobial biofilms. Importantly, these infections are often difficult to treat effectively in part due to the recalcitrance of biofilms to antimicrobial therapy. Emerging evidence suggests that polymicrobial interactions can lead to dramatic and unexpected changes in the ability of antibiotics to eradicate biofilms and often result in decreased antimicrobial efficacy in vitro In this review, we discuss the influence of polymicrobial interactions on the antibiotic susceptibility of biofilms, and we highlight the studies that first documented the shifted antimicrobial susceptibilities of mixed-species cultures. Recent studies have identified several mechanisms underlying the recalcitrance of polymicrobial biofilm communities, including interspecies exchange of antibiotic resistance genes, β-lactamase-mediated inactivation of antibiotics, changes in gene expression induced by metabolites and quorum sensing signals, inhibition of the electron transport chain, and changes in properties of the cell membrane. In addition to elucidating multiple mechanisms that contribute to the altered drug susceptibility of polymicrobial biofilms, these studies have uncovered novel ways in which polymicrobial interactions can impact microbial physiology. The diversity of findings discussed highlights the importance of continuing to investigate the efficacy of antibiotics against biofilm communities composed of different combinations of microbial species. Together, the data presented here illustrate the importance of studying microbes as part of mixed-species communities rather than in isolation. In light of our greater understanding of how interspecies interactions alter the efficacy of antimicrobial agents, we propose that the methods for measuring the drug susceptibility of polymicrobial infections should be revisited.

PIRATE project: point-of-care, informatics-based randomised controlled trial for decreasing overuse of antibiotic therapy in Gram-negative bacteraemia

INTRODUCTION

Antibiotic overuse drives antibiotic resistance. The optimal duration of antibiotic therapy for Gram-negative bacteraemia (GNB), a common community and hospital-associated infection, remains unknown and unstudied via randomised controlled trials (RCTs).

METHODS AND ANALYSIS

This investigator-initiated, multicentre, non-inferiority, informatics-based point-of-care RCT will randomly assign adult hospitalised patients receiving microbiologically efficacious antibiotic(s) for GNB to (1) 14 days of antibiotic therapy, (2) 7 days of therapy or (3) an individualised duration determined by clinical response and 75% reduction in peak C reactive protein (CRP) values. The randomisation will occur in equal proportions (1:1:1) on day 5 (±1) of efficacious antibiotic therapy as determined by antibiogram; patients, their physicians and study investigators will be blind to treatment duration allocation until the day of antibiotic discontinuation. Immunosuppressed patients and those with GNB due to complicated infections (endocarditis, osteomyelitis, etc) and/or non-fermenting bacilli (Acinetobacter spp, Burkholderia spp, Pseudomonas spp) Brucella spp, Fusobacterium spp or polymicrobial growth with Gram-positive organisms will be ineligible. The primary outcome is incidence of clinical failure at day 30; secondary outcomes include clinical failure, all-cause mortality and incidence of Clostridiumdifficile infection in the 90-day study period. An interim safety analysis will be performed after the first 150 patients have been followed for ≤30 days. Given a chosen margin of 10%, the required sample size to determine non-inferiority is roughly 500 patients. Analyses will be performed on both intention-to-treat and per-protocol populations.

ETHICS AND DISSEMINATION

Ethics approval was obtained from the cantonal ethics committees of all three participating sites. Results of the main trial and each of the secondary endpoints will be submitted for publication in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

This trial is registered at www.clinicaltrials.gov (NCT03101072; pre-results).

Decrease of Staphylococcus aureus Virulence by Helcococcus kunzii in a Caenorhabditis elegans Model

Social bacterial interactions are considered essential in numerous infectious diseases, particularly in wounds. Foot ulcers are a common complication in diabetic patients and these ulcers become frequently infected. This infection is usually polymicrobial promoting cell-to-cell communications. Staphylococcus aureus is the most prevalent pathogen isolated. Its association with Helcococcus kunzii, commensal Gram-positive cocci, is frequently described. The aim of this study was to assess the impact of co-infection on virulence of both H. kunzii and S. aureus strains in a Caenorhabditis elegans model. To study the host response, qRT-PCRs targeting host defense genes were performed. We observed that H. kunzii strains harbored a very low (LT50: 5.7 days ± 0.4) or an absence of virulence (LT50: 6.9 days ± 0.5). In contrast, S. aureus strains (LT50: 2.9 days ± 0.4) were significantly more virulent than all H. kunzii (P < 0.001). When H. kunzii and S. aureus strains were associated, H. kunzii significantly reduced the virulence of the S. aureus strain in nematodes (LT50 between 4.4 and 5.2 days; P < 0.001). To evaluate the impact of these strains on host response, transcriptomic analysis showed that the ingestion of S. aureus led to a strong induction of defense genes (lys-5, sodh-1, and cyp-37B1) while H. kunzii did not. No statistical difference of host response genes expression was observed when C. elegans were infected with either S. aureus alone or with S. aureus + H. kunzii. Moreover, two well-characterized virulence factors (hla and agr) present in S. aureus were down-regulated when S. aureus were co-infected with H. kunzii. This study showed that H. kunzii decreased the virulence of S. aureus without modifying directly the host defense response. Factor(s) produced by this bacterium modulating the staphylococci virulence must be investigated.

Outcomes of Nosocomial Bloodstream Infections in Adult Neutropenic Patients: A Prospective Cohort and Matched Case-Control Study

Objective:

To examine the clinical and epidemiologic features, excess length of stay, extra costs, and mortality attributable to bloodstream infection (BSI) in neutropenic patients with hematologic malignancies.

Design:

Prospective cohort and matched case-control study.

Patients:

All adult neutropenic patients with hematologic malignancies admitted to Cologne University Hospital between May 1, 1997, and April 30, 1998, were prospectively observed. Case-patients were defined as patients with nosocomial BSI; control-patients were selected among patients without BSI.

Results:

During the study period, the BSI rate in neutropenic patients was 14.3 per 100 neutropenic episodes. Eighty-four case-patients were included. Matching was successful for 96% of the cohort; 81 matched pairs were studied. The mean total length of stay was significantly longer for patients with BSI than for control-patients (37 vs 29 days;P= .002). Extra costs attributable to the infection averaged $3,200 (U.S.) per patient. The crude mortality rates of case-patients and control-patients were 16% and 4%, respectively (P= .013), with an attributable mortality of 12% (odds ratio, 11). Eighty-seven percent of patients met the criteria for sepsis according to the American College of Chest Physicians/Society of Critical Care Medicine. Severe sepsis or septic shock occurred in 13% of patients and was correlated with mortality (55% vs 10% in patients without severe sepsis or septic shock;P=.01).

Conclusions:

Nosocomial BSI in neutropenic patients is significantly associated with an excess length of hospital stay, extra costs, and excess mortality. Severe sepsis and septic shock are closely correlated with an adverse outcome.

Attributable Cost and Length of Stay for Patients With Central Venous Catheter—Associated Bloodstream Infection in Mexico City Intensive Care Units A Prospective, Matched Analysis

Background.

No information is available about the financial impact of central venous catheter (CVC)-associated bloodstream infection (BSI) in Mexico.

Objective.

To calculate the costs associated with BSI in intensive care units (ICUs) in Mexico City.

Design.

An 18-month (June 2002 through November 2003), prospective, nested case-control study of patients with and patients without BSI.

Setting.

Adult ICUs in 3 hospitals in Mexico City.

Patients and Methods.

A total of 55 patients with BSI (case patients) and 55 patients without BSI (control patients) were compared with respect to hospital, type of ICU, year of hospital admission, length of ICU stay, sex, age, and mean severity of illness score. Information about the length of ICU stay was obtained prospectively during daily rounds. The daily cost of ICU stay was provided by the finance department of each hospital. The cost of antibiotics prescribed for BSI was provided by the hospitals' pharmacy departments.

Results.

For case patients, the mean extra length of stay was 6.1 days, the mean extra cost of antibiotics was $598, the mean extra hospital cost was $11,591, and the attributable extra mortality was 20%.

Conclusions.

In this study, the duration of ICU stay for patients with central venous catheter-associated BSI was significantly longer than that for control patients, resulting in increased healthcare costs and a higher attributable mortality. These conclusions support the need to implement preventive measures for hospitalized patients with central venous catheters in Mexico.

Systemic Staphylococcus aureus infection mediated by Candida albicans hyphal invasion of mucosal tissue

Candida albicans and Staphylococcus aureus are often co-isolated in cases of biofilm-associated infections. C. albicans can cause systemic disease through morphological switch from the rounded yeast to the invasive hyphal form. Alternatively, systemic S. aureus infections arise from seeding through breaks in host epithelial layers although many patients have no documented portal of entry. We describe a novel strategy by which S. aureus is able to invade host tissue and disseminate via adherence to the invasive hyphal elements of Candida albicans. In vitro and ex vivo findings demonstrate a specific binding of the staphylococci to the candida hyphal elements. The C. albicans cell wall adhesin Als3p binds to multiple staphylococcal adhesins. Furthermore, Als3p is required for C. albicans to transport S. aureus into the tissue and cause a disseminated infection in an oral co-colonization model. These findings suggest that C. albicans can facilitate the invasion of S. aureus across mucosal barriers, leading to systemic infection in co-colonized patients.

Pseudomonas aeruginosa bacteremia after burn injury: the impact of multiple-drug resistance

To evaluate the clinical impact of multiple-drug resistance in burn patients with Pseudomonas aeruginosa (Pa) bacteremia. A retrospective cohort study in a 10-bed burn intensive care unit (BICU) was performed. Univariate and multivariate analyses were used to analyze the influence of multiple-drug resistance on mortality and length of BICU stay in Pa bacteremic patients. During a 21-year study period (1989-2009), 87 patients with Pa bacteremia were identified; 45 patients had multiple-drug resistant (MDR) strains and 42 susceptible strains. On comparison of the two populations, one with multiple-drug resistant strains and the other with the susceptible strains, the following parameters were found to be significantly different in the univariate analysis: age (32.7 vs 43.6 years; P = .013), sex (males: 91.1 vs 66.7%; P = .005), intubation status on admission (75.6 vs. 54.8%; P = .041), escharotomy (57.8 vs 33.3%; P = .022), burn size (51.0 vs 35.3% of TBSA; P = .002) and Abbreviated Burn Severity Index score (9.2 vs 8.1; P = .048). In terms of outcome parameters, multiple-drug resistance was not significantly related to mortality (adjusted odds ratio 1.076; 95% confidence interval [CI] 0.356-3.254; P = .897) and length of BICU stay after Pa bacteremia (Kaplan-Meier analysis log-rank test P = .945; Cox's proportional hazards regression hazards ratio, 0.994; 95% CI 0.513-1.925; P = .985) in the univariate and multivariate analyses. The data from this study suggest that multiple-drug resistance is not associated with significant increases in mortality and length of BICU stay among burn patients with Pa bacteremia.

Vacuoles of Candida yeast as a specialized niche for Helicobacter pylori

Helicobacter pylori (H. pylori) are resistant to hostile gastric environments and antibiotic therapy, reflecting the possibility that they are protected by an ecological niche, such as inside the vacuoles of human epithelial and immune cells. Candida yeast may also provide such an alternative niche, as fluorescently labeled H. pylori were observed as fast-moving and viable bacterium-like bodies inside the vacuoles of gastric, oral, vaginal and foodborne Candida yeasts. In addition, H. pylori-specific genes and proteins were detected in samples extracted from these yeasts. The H. pylori present within these yeasts produce peroxiredoxin and thiol peroxidase, providing the ability to detoxify oxygen metabolites formed in immune cells. Furthermore, these bacteria produce urease and VacA, two virulence determinants of H. pylori that influence phago-lysosome fusion and bacterial survival in macrophages. Microscopic observations of H. pylori cells in new generations of yeasts along with amplification of H. pylori-specific genes from consecutive generations indicate that new yeasts can inherit the intracellular H. pylori as part of their vacuolar content. Accordingly, it is proposed that yeast vacuoles serve as a sophisticated niche that protects H. pylori against the environmental stresses and provides essential nutrients, including ergosterol, for its growth and multiplication. This intracellular establishment inside the yeast vacuole likely occurred long ago, leading to the adaptation of H. pylori to persist in phagocytic cells. The presence of these bacteria within yeasts, including foodborne yeasts, along with the vertical transmission of yeasts from mother to neonate, provide explanations for the persistence and propagation of H. pylori in the human population. This Topic Highlight reviews and discusses recent evidence regarding the evolutionary adaptation of H. pylori to thrive in host cell vacuoles.

Sheltering effect and indirect pathogenesis of carbapenem-resistant Acinetobacter baumannii in polymicrobial infection

The role of carbapenem-resistant Acinetobacter baumannii (CRAb) in polymicrobial infection remains elusive. Having observed the ability of CRAb to shelter other susceptible bacteria from carbapenem killing, we sought to determine the factors contributing to this sheltering effect by transforming different recombinant plasmids into recipient A. baumannii cells. The sheltering effects of CRAb were reproduced in recipient A. baumannii cells that highly expressed carbapenem-hydrolyzing class D β-lactamases (CHDLs) through their associated strong promoter. With the use of Western blot analysis and a bioassay, the highly expressed CHDLs were found to be extracellularly released and led to hydrolysis of carbapenem. The level of extracellular CHDLs increased after challenge with a higher concentration of CHDL substrates, such as carbapenem and ticarcillin. This increased CHDL may, in part, be attributed to cell lysis, as indicated by the presence of extracellular gyrase. In the planktonic condition, the sheltering effect for the cocultured susceptible bacteria might represent an indirect and passive effect of the CRAb self-defense mechanism, because coculture with the susceptible pathogen did not augment the amount of the extracellular CHDLs. Polymicrobial infection caused by CRAb and a susceptible counterpart exerted higher pathogenicity than monomicrobial infection caused by either pathogen alone in mice receiving carbapenem therapy. This study demonstrated that CHDL-producing CRAb appears to provide a sheltering effect for carbapenem-susceptible pathogens via the extracellular release of CHDLs and, by this mechanism, can enhance the pathogenesis of polymicrobial infection in the presence of carbapenem therapy.

Polymicrobial bloodstream infections: Epidemiology and impact on mortality

The aim of this study was to investigate the impact of polymicrobial bloodstream infections (pBSIs) on the outcome of sepsis in an area where antimicrobial resistance is of concern. This was a retrospective analysis of data collected prospectively from patients developing BSI outside of an intensive care unit (non-ICU patients) or after ICU admission. Demographics and clinical characteristics were compared for patients with pBSI versus monomicrobial BSI (mBSI) and following stratification by ICU or non-ICU and severity of sepsis status. Possible risk factors for adverse outcome were explored by multivariate analysis, and outcomes were measured by Cox regression analysis. Among 412 patients with BSI, 47 patients (11.4%) with pBSI were recorded; compared with patients with mBSI, they had significantly higher APACHE II scores and presented more frequently with severe sepsis/septic shock. The all-cause 28-day mortality was significantly higher for pBSI versus mBSI (38.3% vs. 24.7%; P=0.033), whereas appropriateness of treatment was comparable (78.7% vs. 86.6%). Primary bacteraemia by combinations of Enterococcus faecalis, Klebsiella pneumoniae and Acinetobacter baumannii was predominant among pBSIs; in mBSIs, urinary tract infections by Escherichia coli, K. pneumoniae or Pseudomonas aeruginosa predominated. Multivariate analysis demonstrated pBSI as a significant contributor to 28-day mortality (HR=1.86; P=0.039), along with presence of two or more co-morbidities (HR=2.35; P=0.004). In conclusion, pBSIs differed epidemiologically from mBSIs, with the emergence of enterococcal species, and portended an almost two-fold increased risk of 28-day mortality. Prospective studies are warranted to elucidate possibly modifiable factors.

Role for the fibrinogen-binding proteins coagulase and Efb in the Staphylococcus aureus-Candida interaction

Staphylococcus aureus and Candida species are increasingly coisolated from implant-associated polymicrobial infections creating an incremental health care problem. Synergistic effects between both genera seem to facilitate the formation of mixed S. aureus-Candida biofilms, which is thought to play a critical role in coinfections with these microorganisms. To identify and characterize S. aureus factors involved in the interaction with Candida species, we affinity-panned an S. aureus phage display library against Candida biofilms in the presence or absence of fibrinogen. Repeatedly isolated clones contained DNA fragments encoding portions of the S. aureus fibrinogen-binding proteins coagulase or Efb. The coagulase binds to prothrombin in a 1:1 ratio thereby inducing a conformational change and non-proteolytic activation of prothrombin, which in turn cleaves fibrinogen to fibrin. Efb has been known to inhibit opsonization. To study the role of coagulase and Efb in the S. aureus-Candida cross-kingdom interaction, we performed flow-cytometric phagocytosis assays. Preincubation with coagulase reduced the phagocytosis of Candida yeasts by granulocytes significantly and dose-dependently. By using confocal laser scanning microscopy, we demonstrated that the coagulase mediated the formation of fibrin surrounding the candidal cells. Furthermore, the addition of Efb significantly protected the yeasts against phagocytosis by granulocytes in a dose-dependent and saturable fashion. In conclusion, the inhibition of phagocytosis of Candida cells by coagulase and Efb via two distinct mechanisms suggests that S. aureus might be beneficial for Candida to persist as it helps Candida to circumvent the host immune system.

Incidence, clinical, microbiological features and outcome of bloodstream infections in patients undergoing hemodialysis

OBJECTIVES

Infection is a common cause of death among hemodialysis patients. The study investigated incidence, risk factors, clinical features and outcome of bloodstream infections (BSIs) in haemodialysis patients.

METHODS

The records of haemodialysis patients from 1999 to 2005 were reviewed. Risk factors were investigated by multivariate analysis.

RESULTS

There were identified 148 bacteremic episodes, in 102 patients. The BSI rate was 0.52 per 1000 patient-days. Of the 148 episodes, 34 occurred in patients with permanent fistulae (0.18/1000 patient-days); 19 in patients with grafts (0.39/1000 patient-days); 28 in patients with permanent tunneled central catheters (1.03/1000 patient-days); and 67 in those with temporary-catheter (3.18/1000 patient-days). With fistula as reference, the BSI ratio was 1.84 with arteriovenous graft (P=.029), 4.85 with permanent central venous catheter (P<.001), and 14.88 with temporary catheter (P <.001). Catheter related were 41 episodes (28%). Gram positive organism were responsible for 96 episodes (65%), with S. aureus ( 55%) the most frequent, followed by S. epidermidis (26%) and Gram-negative for 36 (23%), with E. coli (39%) the most frequent. Infection was polymicrobial in 14 (9.5%). Diabetes (p<0.001), low serum albumin (p=0.040) and low hemoglobin (p<0.001) were significant risk factors. During hospitalization 18 patients (18%) died. Septic shock (p<0.001) and polymicrobial infection (p=0.041) were associated with in-hospital mortality.

CONCLUSION

The risk of BSI in patients undergoing hemodialysis is related to the catheter type and vascular access. Septic shock and polymicrobial infection predispose to unfavourable outcome.

Clinical characteristics and risk factors for mortality in patients with bacteremia caused by Pseudomonas aeruginosa

OBJECTIVE

The mortality rates for bacteremia due to Pseudomonas aeruginosa remain high. In our hospital, we performed retrospective analyses to determine risk factors for mortality among patients with bacteremia caused by P. aeruginosa.

MATERIALS AND METHODS

This retrospective cohort study was conducted among adult patients with bacteremia due to P. aeruginosa at Jikei University Hospital. We analyzed factors, such as age, gender, underlying disease, initial antimicrobial treatment, and primary site of infection to determine which of these were predictive of mortality in patients with P. aeruginosa bacteremia.

RESULTS

One hundred and thirty-four patients with P. aeruginosa bacteremia were identified between April 2003 and March 2010. The 30-day mortality rate among all patients with P. aeruginosa bacteremia was 20.9%. The most common underlying disease was leukemia (20.9%), and the most common primary site of infection was the urinary tract (24.6%). Seventy-one patients (65.7%) were treated with an appropriate initial antimicrobial regimen for P. aeruginosa bacteremia. However, these patients had similar 30-day mortality to that observed in patients not administered appropriate antibiotics. This study revealed that risk factors for the 30-day mortality were thrombocytopenia and polymicrobial P. aeruginosa bacteremia (p<0.01).

CONCLUSION

Thrombocytopenia and polymicrobial bacteremia were associated with a greater incidence of 30-day mortality among patients with P. aeruginosa bacteremia. On the other hand, age, underlying disease, and inappropriate initial empirical antimicrobial treatment did not affect mortality.

Pediatric patients with intravascular devices: polymicrobial bloodstream infections and risk factors

A retrospective study was conducted, including 61 patients with long-term intravascular devices (IVDs) admitted to the Childrens Hospital Los Angeles with diverse underlying diseases, different types of catheters, and culture-proven catheter-related bloodstream infections (BSIs). Within these patients, 125 catheter-related BSIs occurred, and the incidence of monomicrobial and polymicrobial BSIs was evaluated. Risk factors for polymicrobial BSIs were determined. Forty-two BSIs contained more than one pathogen. These polymicrobial BSIs were observed more often in younger patients (<4.1 years versus ≥4.1 years) and less in patients using venous implanted ports. No other associations were found between the occurrences of polymicrobial BSIs and underlying diseases, other types of catheters, host defense status, parenteral nutrition, recurrences, or catheter removal. Patients with long-term IVDs at a younger age have a higher risk of developing a polymicrobial BSI. Future prospective studies should address the issue of polymicrobial infection in IVDs in more detail.

Conventional and molecular techniques for the early diagnosis of bacteraemia

Bloodstream infections account for 30-40% of all cases of severe sepsis and septic shock, and are major causes of morbidity and mortality. Diagnosis of bloodstream infections must be performed promptly so that adequate antimicrobial therapy can be started and patient outcome improved. An ideal diagnostic technology would identify the infecting organism(s) and their determinants of antibiotic resistance, in a timely manner, so that appropriate pathogen-driven therapy could begin promptly. Unfortunately, despite the essential information it provides, blood culture, the gold standard, largely fails in this purpose because time is lost waiting for bacterial or fungal growth. Several efforts have been made to optimise the performance of blood culture, such as the development of technologies to obtain rapid detection of microorganism(s) directly in blood samples or in a positive blood culture. The ideal molecular method would analyse a patient's blood sample and provide all the information needed to immediately direct optimal antimicrobial therapy for bacterial or fungal infections. Furthermore, it would provide data to assess the effectiveness of the therapy by measuring the clearance of microbial nucleic acids from the blood over time. None of the currently available molecular methods is sufficiently rapid, accurate or informative to achieve this. This review examines the principal advantages and limitations of some traditional and molecular methods commercially available to help the microbiologist and the clinician in the management of bloodstream infections.

The interaction between a non-pathogenic and a pathogenic strain synergistically enhances extra-intestinal virulence in Escherichia coli

Finding two or more genotypes of a single species within an infected sample is a not infrequent event. In this work, three Escherichia coli strains of decreasing extra-intestinal virulence (pathogenic B2S and B1S strains, and the avirulent K-12 MG1655 strain) were tested in septicaemia and urinary tract infection (UTI) mouse models, either separately or in pairs. Survival was monitored and bacteria were counted in various organs. Serum interleukin (IL)-6, tumour necrosis factor alpha (TNFα) and IL-10 were measured. We show that a mix of high amounts of B1S or of MG1655 with low amounts of B2S killed more rapidly (B1S), or killed more mice (MG1655), than either high amounts of B1S, high amounts of MG1655 or low amounts of B2S separately in the mouse septicaemia model. This bacterial synergy persisted when high amounts of dead or abnormal-LPS K-12 cells were injected together with a low amount of B2S. In both septicaemia and UTI models, significantly more bacteria were recovered from the organs of mice injected with the MG1655/B2S mix than from those of mice injected with the inocula separately. Consistently, in the septicaemia model, more IL-6 was secreted before death by the mice that were injected with the mix of bacteria than by the mice that were injected with the inocula separately. The synergistically enhanced mortality in the case of co-infection in the septicaemia model persisted in RFcγ(-/-), Myd88(-/-) and IL-6(-/-) knockout mice. This synergistically increased virulence resulting from the interaction between an avirulent and a pathogenic strain of the same bacterial species raises questions about the role of avirulent bacteria in the development of some extra-intestinal infections.

Bacteraemia in neonatal foals: clinicopathological differences between Gram-positive and Gram-negative infections, and single organism and mixed infections

REASONS FOR PERFORMING STUDY

Treatment for bacteraemia in foals must be started before the identity of the causative organism is known. Information aiding selection of effective antimicrobials should improve outcome.

OBJECTIVES

To describe differences in clinical and clinicopathological data and outcome in foals with bacteraemia due to different classes of bacteria.

METHODS

Records of foals with a positive blood culture, age < 10 days and presenting to a university hospital 1995-2004, were reviewed. Bacterial culture results, subject details, historical information, physical examination findings at admission and clinicopathological data generated during the first 48 h of hospitalisation were analysed. Results from foals with Gram-positive or Gram-negative organisms, single or mixed organism bacteraemias, and with bacteraemia due to 3 commonly isolated organisms were compared.

RESULTS

Eighty-five foals met the inclusion criteria. Gram-negative organisms (n = 59) Gram-positive organisms (n = 13) or multiple organisms (n = 19) were cultured from individual foals. Foals with Gram-negative bacteraemia had lower total white blood cell and lymphocyte counts at admission than did those from which only Gram-positive bacteria were cultured. Mixed organism bacteraemia was associated with tachycardia, increased serum concentrations of sodium, chloride and urea nitrogen, acidosis, respiratory distress, recumbency on admission and nonsurvival. Actinobacillus spp. infections were associated with leucopenia, neutropenia, lymphopenia and depression on hospital admission.

CONCLUSIONS AND POTENTIAL RELEVANCE

Recognising particular patterns of clinical and clinicopathological findings associated with infection with specific groups of bacteria may, in the future, aid antimicrobial selection and influence prognosis in bacteraemic foals.

A multi-centre prospective study of febrile neutropenia in Norway: Microbiological findings and antimicrobial susceptibility

The urgent need to treat presumptive bacterial or fungal infections in neutropenic patients has meant that initial therapy is empiric and based on the pathogens most likely to be responsible, and drug resistance. The traditional empirical treatment in Norway has been penicillin G and an aminoglycoside, and this combination has been criticized over recent y. We wished to analyse the microbiological spectrum and susceptibility patterns of pathogens causing bacteraemia in febrile neutropenic patients. This was a prospective multicentre study. During the study period of 2 y, a total of 282 episodes of fever involving 243 neutropenic patients was observed. In 34% of episodes bacteraemia was documented. Overall, 40% of the episodes were caused by Gram-positive organisms, 41% by Gram-negative organisms and 19% were polymicrobial. The most frequently isolated bacteria were Escherichia coli (25.6%), a- and non-haemolytic streptococci (15.6%), coagulase-negative staphylococci (12.4%) and Klebsiella spp. (7.4%). None of the Gram-negative isolates was resistant to gentamicin, meropenem, ceftazidime or ciprofloxacin. Only 5 coagulase-negative staphylococci isolates were resistant to both penicillin G and aminoglycoside. The overall mortality rate was 7%, and 1.2% due to confirmed bacteraemic infection.

Cross-kingdom interactions: Candida albicans and bacteria

Bacteria and fungi are found together in a myriad of environments and particularly in a biofilm, where adherent species interact through diverse signaling mechanisms. Yet, despite billions of years of coexistence, the area of research exploring fungal-bacterial interactions, particularly within the context of polymicrobial infections, is still in its infancy. However, reports describing a multitude of wide-ranging interactions between the fungal pathogen Candida albicans and various bacterial pathogens are on the rise. An example of a mutually beneficial interaction is coaggregation, a phenomenon that takes place in oral biofilms where the adhesion of C. albicans to oral bacteria is considered crucial for its colonization of the oral cavity. In contrast, the interaction between C. albicans and Pseudomonas aeruginosa is described as being competitive and antagonistic in nature. Another intriguing interaction is that occurring between Staphylococcus aureus and C. albicans, which although not yet fully characterized, appears to be initially synergistic. These complex interactions between such diverse and important pathogens would have significant clinical implications if they occurred in an immunocompromised host. Therefore, understanding the mechanisms of adhesion and signaling involved in fungal-bacterial interactions may lead to the development of novel therapeutic strategies for impeding microbial colonization and development of polymicrobial disease.

Matched case-control analysis of polymicrobial bloodstream infection in a neonatal intensive care unit

OBJECTIVE

To compare and contrast the epidemiology of polymicrobial and monomicrobial bloodstream infections (BSIs) in newborn intensive care unit (NICU) patients.

DESIGN

Retrospective, matched case-control study.

SETTING

The Yale-New Haven Hospital NICU from 1989 through 2006.

SUBJECTS

NICU patients with BSIs.

METHODS

Each neonate with polymicrobial BSI (case patient) was matched to one neonate with monomicrobial BSI (control patient), by birth date, weight, and sex; and univariate and multivariate analyses were performed.

RESULTS

One hundred five cases of polymicrobial BSI were identified in 102 infants, representing 10% of all neonatal BSIs in our institution. Coagulase-negative staphylococci were the most common organisms recovered from culture. Infants with polymicrobial BSI had later onset of infection than infants with monomicrobial BSI (mean day of life, 37.5 vs 24.0; P<.001). Polymicrobial BSI occurred more frequently among infants with a severe underlying condition than in those without such a condition (odds ratio [OR], 1.8; 95% confidence interval [CI], 1.1-3.2) and among infants requiring an indwelling central venous catheter for a prolonged duration (mean, 16.9 days, compared with 9.8 days for infants with monomicrobial BSI; P=.001). Multivariate analysis revealed that later onset of infection (adjusted OR [aOR], 1.02; 95% CI, 1.00-1.04) and presence of a severe underlying condition (aOR, 1.91; 95% CI, 1.12-3.38) were independent risk factors for polymicrobial BSI. No differences in outcome or mortality were observed.

CONCLUSIONS

Changes in the microbiology and epidemiology of NICU-related polymicrobial BSI have occurred since the last North American review. In the present study, although differences were observed, most risk factors and outcomes were similar between monomicrobial BSI and polymicrobial BSI. Epidemiologic surveillance is critical to identify trends associated with neonatal polymicrobial BSI, particularly those that may impact preventative strategies, diagnostic measures, and therapeutic interventions.

Bloodstream infection after living donor liver transplantation

There are no detailed studies on the prevalence or clinical magnitude of bloodstream infection (BSI) following living donor liver transplantation (LDLT). The study aimed to assess the incidence and analyze the risk factors for BSI after LDLT. Univariate and multivariate analyses were performed to identify the independent risk factors for postoperative BSI. Postoperatively, 26 episodes of BSI occurred in 21 of 242 studied adult patients by median postoperative d 35. Five patients had primary BSI. The source was unknown in 3 patients and an intravascular catheter in 2. The other 16 patients had secondary BSI. Secondary BSI was caused by surgical site infection in 8 patients, followed by intra-abdominal infection in 5, pneumonia in 2, and both surgical site infection and intra-abdominal infection in 1. The most frequent pathogen isolated was MRSA, which was detected in 4 patients. Surveillance culture detected the same isolates prior to BSI in 14 of 26 (50%) episodes. Diabetes mellitus and serum albumin level less than 2.4 g/dl independently predicted postoperative BSI. Perioperatively, screening for and taking actions against pathogen including MRSA should be performed in LDLT patients.

Fungal colonization and/or infection in non-neutropenic critically ill patients: results of the EPCAN observational study

The purpose of this paper is to determine the incidence of fungal colonization and infection in non-neutropenic critically ill patients and to identify factors favoring infection by Candida spp. A total of 1,655 consecutive patients (>18 years of age) admitted for > or = 7 days to 73 medical-surgical Spanish intensive care units (ICUs) participated in an observational prospective cohort study. Surveillance samples were obtained once a week. One or more fungi were isolated in different samples in 59.2% of patients, 94.2% of which were Candida spp. There were 864 (52.2%) patients with Candida spp. colonization and 92 (5.5%) with proven Candida infection. In the logistic regression analysis risk factors independently associated with Candida spp. infection were sepsis (odds ratio [OR] = 8.29, 95% confidence interval [CI] 5.07-13.6), multifocal colonization (OR = 3.49, 95% CI 1.74-7.00), surgery (OR = 2.04, 95% CI 1.27-3.30), and the use of total parenteral nutrition (OR = 4.37, 95% CI 2.16-8.33). Patients with Candida spp. infection showed significantly higher in-hospital and intra-ICU mortality rates than those colonized or non-colonized non-infected (P < 0.001). Fungal colonization, mainly due to Candida spp., was documented in nearly 60% of non-neutropenic critically ill patients admitted to the ICU for more than 7 days. Proven candidal infection was diagnosed in 5.5% of cases. Risk factors independently associated with Candida spp. infection were sepsis, multifocal colonization, surgery, and the use of total parenteral nutrition.

Epidemiology of bloodstream infections in patients receiving long-term total parenteral nutrition

GOALS

To describe the epidemiology and microbiologic characteristics of bloodstream infections (BSIs) in patients receiving long-term total parenteral nutrition (TPN).

BACKGROUND

Home TPN therapy has been reported as a risk factor for BSI. However, little knowledge exists regarding the epidemiology of BSIs in this patient group.

STUDY

A descriptive, observational epidemiologic study of patients receiving long-term TPN from January 1981 to July 2005 was performed. Variables analyzed include age, gender, time of follow-up, number of BSIs, microbiologic characteristics, underlying disease necessitating long-term TPN, catheter type, complications related to TPN, and clinical outcome.

RESULTS

Forty-seven patients receiving long-term TPN were evaluated. The most frequent indication for long-term TPN was ischemic bowel disease (25.5%). The mean duration of follow-up was 4.5 years. Thirty-eight patients (80.9%) developed 248 BSIs while receiving TPN. More than 1 BSI episode occurred in 78.9% of these patients, and 23.8% of BSI episodes were polymicrobial. The most prevalent pathogen was coagulase negative staphylococci (33.5%). The most frequent complication among patients with BSI was central venous thrombosis (44.7%). Five patients were intravenous drug users. There were 11 deaths among the patients on long-term TPN, 4 of these were related to infection and 4 were related to intravenous drug use.

CONCLUSIONS

The incidence of BSI is high, and a significant proportion of BSIs in long-term TPN patients are polymicrobial and due to multidrug-resistant bacteria and fungi. Careful management of the infusion line is required and interventions are needed to reduce the risk of catheter-related infections in this population.

Sepsis: Still Going Strong

Sepsis definitions help to understand and to better define a group of syndromes secondary to an infectious insult. The hierarchical continuum of inflammatory response leads, in absence of counterregulatory forces, to organ damage and death. We have learned first the response to treatment and afterwards the pathophysiology behind it. This lesson has, of course, not always been followed by a reduction of mortality. The definition, natural history, risk factors, diagnoses, and treatment based on emerging evidence will help to improve patient outcomes and mortality. Standardized care seems to improve survival, and validation and further evaluation of this care is necessary to maximize resources and outcomes.

Comparison of the systemic inflammatory response syndrome between monomicrobial and polymicrobial Pseudomonas aeruginosa nosocomial bloodstream infections

Background

Some studies of nosocomial bloodstream infection (nBSI) have demonstrated a higher mortality for polymicrobial bacteremia when compared to monomicrobial nBSI. The purpose of this study was to compare differences in systemic inflammatory response and mortality between monomicrobial and polymicrobial nBSI with Pseudomonas aeruginosa.

Methods

We performed a historical cohort study on 98 adults with P. aeruginosa (Pa) nBSI. SIRS scores were determined 2 days prior to the first positive blood culture through 14 days afterwards. Monomicrobial (n = 77) and polymicrobial BSIs (n = 21) were compared.

Results

78.6% of BSIs were caused by monomicrobial P. aeruginosa infection (MPa) and 21.4% by polymicrobial P. aeruginosa infection (PPa). Median APACHE II score on the day of BSI was 22 for MPa and 23 for PPa BSIs. Septic shock occurred in 33.3% of PPa and in 39.0% of MPa (p = 0.64). Progression to septic shock was associated with death more frequently in PPa (OR 38.5, CI95 2.9–508.5) than MPa (OR 4.5, CI95 1.7–12.1). Maximal SIR (severe sepsis, septic shock or death) was seen on day 0 for PPa BSI vs. day 1 for MPa. No significant difference was noted in the incidence of organ failure, 7-day or overall mortality between the two groups. Univariate analysis revealed that APACHE II score ≥20 at BSI onset, Charlson weighted comorbidity index ≥3, burn injury and respiratory, cardiovascular, renal and hematologic failure were associated with death, while age, malignant disease, diabetes mellitus, hepatic failure, gastrointestinal complications, inappropriate antimicrobial therapy, infection with imipenem resistant P. aeruginosa and polymicrobial nBSI were not. Multivariate analysis revealed that hematologic failure (p < 0.001) and APACHE II score ≥20 at BSI onset (p = 0.005) independently predicted death.

Conclusion

In this historical cohort study of nBSI with P. aeruginosa, the incidence of septic shock and organ failure was high in both groups. Additionally, patients with PPa BSI were not more acutely ill, as judged by APACHE II score prior to blood culture positivity than those with MPa BSI. Using multivariable logistic regression analysis, the development of hematologic failure and APACHE II score ≥20 at BSI onset were independent predictors of death; however, PPa BSI was not.

Risk factors for mortality resulting from bloodstream infections in a pediatric intensive care unit

BACKGROUND

Bloodstream infections (BSIs) are prevalent in the critical care setting and have high attributable morbidity and mortality. The purpose of this study was to identify factors that significantly contribute to immediate as well as eventual mortality in patients with bloodstream infections at a pediatric intensive care unit (PICU).

METHODS

Retrospective review of 2097 clinical records from admissions to our PICU in a 2-year period. Two separate case-control models were used. In the first model, eventual mortality (EM CASES) reflected those patients with eventual mortality, and EM CONTROLS were those who survived. In the second, infection-related mortality (IRM) cases were those with infection-related mortality, defined as death within 7 days of BSI, and IRM CONTROLS were survivors past 7 days. Logistic regression was used to adjust for differences for 3 categories: patient characteristics, microbiology and treatment variables.

RESULTS

We identified 74 separate episodes of bacteremia. Having an underlying malignancy or immunodeficiency was the only independently significant predictor of eventual mortality for BSI isolated within the PICU. Patients with infection-related mortality more likely had Gram-negative bacteremia and/or fungemia, were older and had inadequate initial empiric antibiotic treatment at the time BSI was diagnosed.

CONCLUSIONS

Targeted and aggressive early interventions should guide the empiric treatment of BSIs, whereas prolonged broad spectrum treatment should be minimized to avoid the emergence of resistant pathogen organisms.

Nosocomial and community-acquired Enterobacter cloacae bloodstream infection: risk factors for and prevalence of SHV-12 in multiresistant isolates in a medical centre

In a medical centre in northern Taiwan, 60 patients had bloodstream infection caused by Enterobacter cloacae from 1 January 2002 to 30 April 2003. Forty (66.7%) were nosocomial and 26 were caused by multiresistant isolates. Twenty patients died due to the infection. Central venous catheterization and mechanical ventilation were relative risks for nosocomial E. cloacae infection. Age and mechanical ventilation were risk factors for multiresistant E. cloacae infection. Mortality was associated with multiresistant isolates and polymicrobial infection. Pulsed-field gel electrophoresis (PFGE) analysis showed, the 26 multiresistant isolates comprised 12 different types, with type A predominating (12 isolates). Excluding the patients infected with PFGE type A, central venous catheterization was a relative risk for infection, and polymicrobial infection was a risk factor for mortality. All but one of the 26 multiresistant isolates had the extended-spectrum beta-lactamase SHV-12. TEM-1 and ampC beta-lactamase genes were also detected in 25 of the 26 multiresistant isolates. Southern blotting indicated that the SHV-12 gene was located on plasmids. Eleven of the 26 multiresistant isolates had minimum inhibitory concentrations (MIC) > or =16 mg/L for cefepime, which was reduced by the addition of sulbactam for most isolates, resulting in susceptibility. The combination of cefepime and sulbactam may be effective in the treatment of multiresistant E. cloacae bloodstream infection.

Nosocomial bloodstream infections in US hospitals: analysis of 24,179 cases from a prospective nationwide surveillance study

BACKGROUND

Nosocomial bloodstream infections (BSIs) are important causes of morbidity and mortality in the United States.

METHODS

Data from a nationwide, concurrent surveillance study (Surveillance and Control of Pathogens of Epidemiological Importance [SCOPE]) were used to examine the secular trends in the epidemiology and microbiology of nosocomial BSIs.

RESULTS

Our study detected 24,179 cases of nosocomial BSI in 49 US hospitals over a 7-year period from March 1995 through September 2002 (60 cases per 10,000 hospital admissions). Eighty-seven percent of BSIs were monomicrobial. Gram-positive organisms caused 65% of these BSIs, gram-negative organisms caused 25%, and fungi caused 9.5%. The crude mortality rate was 27%. The most-common organisms causing BSIs were coagulase-negative staphylococci (CoNS) (31% of isolates), Staphylococcus aureus (20%), enterococci (9%), and Candida species (9%). The mean interval between admission and infection was 13 days for infection with Escherichia coli, 16 days for S. aureus, 22 days for Candida species and Klebsiella species, 23 days for enterococci, and 26 days for Acinetobacter species. CoNS, Pseudomonas species, Enterobacter species, Serratia species, and Acinetobacter species were more likely to cause infections in patients in intensive care units (P<.001). In neutropenic patients, infections with Candida species, enterococci, and viridans group streptococci were significantly more common. The proportion of S. aureus isolates with methicillin resistance increased from 22% in 1995 to 57% in 2001 (P<.001, trend analysis). Vancomycin resistance was seen in 2% of Enterococcus faecalis isolates and in 60% of Enterococcus faecium isolates.

CONCLUSION

In this study, one of the largest multicenter studies performed to date, we found that the proportion of nosocomial BSIs due to antibiotic-resistant organisms is increasing in US hospitals.

Impact of adequate empirical antibiotic therapy on the outcome of patients admitted to the intensive care unit with sepsis

OBJECTIVES

Our primary goal was to evaluate the impact on in-hospital mortality rate of adequate empirical antibiotic therapy, after controlling for confounding variables, in a cohort of patients admitted to the intensive care unit (ICU) with sepsis. The impact of adequate empirical antibiotic therapy on early (<3 days), 28-day, and 60-day mortality rates also was assessed. We determined the risk factors for inadequate empirical antibiotic therapy. DESIGN Prospective cohort study.

SETTING

ICU of a tertiary hospital.

PATIENTS

All the patients meeting criteria for sepsis at admission to the ICU.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Four hundred and six patients were included. Microbiological documentation of sepsis was obtained in 67% of the patients. At ICU admission, sepsis was present in 105 patients (25.9%), severe sepsis in 116 (28.6%), and septic shock in 185 (45.6%). By multivariate analysis, predictors of in-hospital mortality were Sepsis-related Organ Failure Assessment (SOFA) score at ICU admission (odds ratio [OR], 1.29; 95% confidence interval [CI], 1.19-1.40), the increase in SOFA score over the first 3 days in the ICU (OR, 1.40; 95% CI, 1.19-1.65), respiratory failure within the first 24 hrs in the ICU (OR, 3.12; 95% CI, 1.54-6.33), and inadequate empirical antimicrobial therapy in patients with "nonsurgical sepsis" (OR, 8.14; 95% CI, 1.98-33.5), whereas adequate empirical antimicrobial therapy in "surgical sepsis" (OR, 0.37; 95% CI, 0.18-0.77) and urologic sepsis (OR, 0.14; 95% CI, 0.05-0.41) was a protective factor. Regarding early mortality (<3 days), factors associated with fatality were immunosuppression (OR, 4.57; 95% CI, 1.69-13.87), chronic cardiac failure (OR, 9.83; 95% CI, 1.98-48.69) renal failure within the first 24 hrs in the unit (OR, 8.63; 95% CI, 3.31-22.46), and respiratory failure within the first 24 hrs in the ICU (OR, 12.35; 95% CI, 4.50-33.85). Fungal infection (OR, 47.32; 95% CI, 5.56-200.97) and previous antibiotic therapy within the last month (OR, 2.23; 95% CI, 1.1-5.45) were independent variables related to administration of inadequate antibiotic therapy.

CONCLUSIONS

In patients admitted to the ICU for sepsis, the adequacy of initial empirical antimicrobial treatment is crucial in terms of outcome, although early mortality rate was unaffected by the appropriateness of empirical antibiotic therapy.

Use of amplified fragment length polymorphism analysis to identify medically important Candida spp., including C. dubliniensis

Non-Candida albicans Candida species are increasingly being isolated. These species show differences in levels of resistance to antimycotic agents and mortality. Therefore, it is important to be able to correctly identify the causative organism to the species level. Identification of C. dubliniensis in particular remains problematic due to the high degree of phenotypic similarity between this species and C. albicans. The use of amplified fragment length polymorphism (AFLP) analysis as an identification method for medically important Candida species was investigated. Our results show very clear differences among medically important Candida species. Furthermore, when screening a large collection of clinical isolates previously identified on CHROMagar as C. albicans, we found a misidentification rate of 6%. AFLP analysis is universally applicable, and the patterns can easily be stored in a general, accessible database. Therefore, AFLP might prove to be a reliable method for the identification of medically important Candida species.

The Role of Intravascular Devices in Sepsis

Intravascular devices (IVDs) are widely used in modern day health care. Unfortunately, their use is associated with substantial risk of bloodstream infection (BSI) and sepsis, with increased hospitalization and hospital mortality. IVDs are the most common cause of nosocomial BSI. The wider use of new methodologies for diagnosis of IVD-related infection should allow earlier and more focused therapy and, especially, improve the accuracy of surveillance. Of all nosocomial infections, IVD-related BSIs are most amendable to prevention.

Preventing vascular catheter-related infections: current controversies

Prevention of vascular catheter-related infection remains an important priority. This review focuses on salient controversies regarding optimal preventive methods. Intensity of surveillance for nosocomial infections was the single most important predictor of prevention in the Study of the Efficacy of Nosocomial Infection Control (SENIC). Used suboptimally by most hospitals in the SENIC study, surveillance is probably conducted even less today. There has been one randomized trial of the optimal method of aseptic insertion for central venous catheters and none comparing the 2 most frequently used sites. Scheduled replacement did not prevent infection in multiple randomized trials but, according to a recent survey, was still being used frequently. Chlorhexidine preparation of skin before and during catheterization has significantly reduced colonization of catheters in multiple randomized trials and should be used. Impregnation of catheter and/or hub surfaces with antiseptics raises less concern about fostering the development of antibiotic resistance than does the use of antibiotics for this purpose.

Polyclonal bacteremia due to gram-negative rods

The frequency of, risk factors for, and outcome of polyclonal gram-negative bacteremia are still unknown. We investigated them in a prospective cohort study of patients for whom a blood culture yielded >/=1 species of gram-negative aerobic rod. For each patient, pulsed field gel electrophoresis (PFGE) was performed on 4 colonies of each morphologic type. Episodes of bacteremia were considered polyclonal if caused by >1 PFGE type of the same species. Ten (6.5%) of 153 investigated patients had polyclonal bacteremia. Bacteremia due to nonfermenting rods was the single significant risk factor for polyclonal bacteremia. Complications were equally frequent in all patient groups. However, patients with polyclonal bacteremia received more extensive antibiotic therapy than did patients with monoclonal bacteremia. Nearly 20% of episodes of bacteremia due to nonfermenting rods were polyclonal, but it remains unclear why nonfermenting rods were more likely to cause polyclonal bacteremia than were other gram-negative rods.

Outcomes of primary and catheter-related bacteremia. A cohort and case-control study in critically ill patients

We studied a cohort of 2201 patients hospitalized in 15 French intensive care units (ICUs) for > or = 48 h during a 4-mo period to assess the incidence and outcomes of primary and definite catheter-related bloodstream (CRB) or secondary nosocomial bloodstream infection (NBSI). Variables associated with ICU death and duration of stay were determined by logistic regression, and attributable mortality and length of stay (LOS) from a nested matched case-control (96 pairs) study, stratified on the source of bacteremia. Bacteremia occurred in 5% (95% CI 4.1-6%) of patients with > or = 48 h ICU stay. Primary, CRB, and secondary NBSI accounted for 29%, 26%, and 45% of the 111 episodes, respectively. NBSI was associated with a markedly increased risk of death (OR = 4.6; 95% CI 2.9-7.1) and an attributable mortality of 35% (95% CI, 28%-47%). In the case-control study, the excess mortality was 20% (p = 0.03) in patients with primary bacteremia and CRB, and 55% (p < 0.001) for secondary bacteremia; in patients with CRB only, the excess mortality was 11.5%. The median excess ICU LOS in survivors of NBSI was 9.5 d, and was similar, irrespective of its source. The risk of mortality associated with primary and catheter-related bacteremia appears much lower than that of secondary bacteremia, but is sizable, and the excess LOS incurred by the various categories of bacteremia is comparable. Differentiating catheter-related bacteremia from both primary and other secondary bacteremia appears warranted in studies conducted in critically ill patients.

[Candidiasis among non-neutropenic patients: from colonization to infection]

Invasive candidiasis is a dread complication in hospitalized patients, characterized by a mortality comparable to that of septic shock (40% to 60%). Its incidence in hospitalized patients is 0.5/1000 admissions, but it complicates about 10 per 1,000 admissions in critical care where it represents 10% to 15% of all nosocomial infections. Although a high proportion of hospitalized patients may become colonized with Candida spp, the clinical signs of infection manifest only late, rending it difficult to diagnose. A better knowledge of their pathophysiology and the availability of triazoles compounds, less toxic than amphotericin B, allowed the concept of early empirical or preemptive treatment. These strategies are based on the prompt identification of risk factors and require continuous attention from skilled physicians. However, the prescription of triazoles has to be restricted to carefully selected groups of patients to avoid the emergence and the dissemination of resistant strains.

Four year prospective evaluation of nosocomial bacteremia: epidemiology, microbiology, and patient outcome

A prospective study of all patients with clinically significant nosocomial bacteremia at one institution from 1994 to 1997 was performed to: (1) describe the epidemiology and microbiology of nosocomial bacteremias; (2) determine the crude mortality associated with such infections; and (3) identify independent predictors of mortality. Four hundred four episodes of bacteremia occurred in 322 patients; the crude in-hospital mortality was 31%. Coagulase-negative staphylococci, Staphylococcus aureus, and enterococci were the leading pathogens, and intravascular catheters were the most frequently identified source. The highest mortality occurred in patients with candidemia (67%). Independent predictors of mortality included evidence of shock at the time of infection, acquisition of bacteremia in an intensive care unit, a "Do Not Attempt Resuscitation" order, and the presence of certain comorbid conditions (e.g., malignancy, HIV infection). Because many of these infections may be preventable, education of health care providers and strict adherence to established infection control practices are critical.