The impact of multidrug resistance on outcomes in ventilator-associated pneumonia

Early prediction of ventilator-associated pneumonia with machine learning models: A systematic review and meta-analysis of prediction model performance✰

BACKGROUND

Machine learning-based prediction models can catalog, classify, and correlate large amounts of multimodal data to aid clinicians at diagnostic, prognostic, and therapeutic levels. Early prediction of ventilator-associated pneumonia (VAP) may accelerate the diagnosis and guide preventive interventions. The performance of a variety of machine learning-based prediction models were analyzed among adults undergoing invasive mechanical ventilation.

METHODS

This systematic review and meta-analysis was conducted in accordance with the Cochrane Collaboration. Machine learning-based prediction models were identified from a search of nine multi-disciplinary databases. Two authors independently selected and extracted data using predefined criteria and data extraction forms. The predictive performance, the interpretability, the technological readiness level, and the risk of bias of the included studies were evaluated.

RESULTS

Final analysis included 10 static prediction models using supervised learning. The pooled area under the receiver operating characteristics curve, sensitivity, and specificity for VAP were 0.88 (95 % CI 0.82-0.94, I2 98.4 %), 0.72 (95 % CI 0.45-0.98, I2 97.4 %) and 0.90 (95 % CI 0.85-0.94, I2 97.9 %), respectively. All included studies had either a high or unclear risk of bias without significant improvements in applicability. The care-related risk factors for the best performing models were the duration of mechanical ventilation, the length of ICU stay, blood transfusion, nutrition strategy, and the presence of antibiotics.

CONCLUSION

A variety of the prediction models, prediction intervals, and prediction windows were identified to facilitate timely diagnosis. In addition, care-related risk factors susceptible for preventive interventions were identified. In future, there is a need for dynamic machine learning models using time-depended predictors in conjunction with feature importance of the models to predict real-time risk of VAP and related outcomes to optimize bundled care.

A Narrative Review on the Approach to Antimicrobial Use in Ventilated Patients with Multidrug Resistant Organisms in Respiratory Samples—To Treat or Not to Treat? That Is the Question

Multidrug resistant organisms (MDRO) are commonly isolated in respiratory specimens taken from mechanically ventilated patients. The purpose of this narrative review is to discuss the approach to antimicrobial prescription in ventilated patients who have grown a new MDRO isolate in their respiratory specimen. A MEDLINE and PubMed literature search using keywords “multidrug resistant organisms”, “ventilator-associated pneumonia” and “decision making”, “treatment” or “strategy” was used to identify 329 references as background for this review. Lack of universally accepted diagnostic criteria for ventilator-associated pneumonia, or ventilator-associated tracheobronchitis complicates treatment decisions. Consideration of the clinical context including signs of respiratory infection or deterioration in respiratory or other organ function is essential. The higher the quality of respiratory specimens or the presence of bacteremia would suggest the MDRO is a true pathogen, rather than colonization, and warrants antimicrobial therapy. A patient with higher severity of illness has lower safety margins and may require initiation of antimicrobial therapy until an alternative diagnosis is established. A structured approach to the decision to treat with antimicrobial therapy is proposed.

Clinical and microbiological outcomes, by causative pathogen, in the ASPECT-NP randomized, controlled, Phase 3 trial comparing ceftolozane/tazobactam and meropenem for treatment of hospital-acquired/ventilator-associated bacterial pneumonia

OBJECTIVES

In the ASPECT-NP trial, ceftolozane/tazobactam was non-inferior to meropenem for treating nosocomial pneumonia; efficacy outcomes by causative pathogen were to be evaluated.

METHODS

Mechanically ventilated participants with hospital-acquired/ventilator-associated bacterial pneumonia were randomized to 3 g ceftolozane/tazobactam (2 g ceftolozane/1 g tazobactam) q8h or 1 g meropenem q8h. Lower respiratory tract (LRT) cultures were obtained ≤36 h before first dose; pathogen identification and susceptibility were confirmed at a central laboratory. Prospective secondary per-pathogen endpoints included 28 day all-cause mortality (ACM), and clinical and microbiological response at test of cure (7-14 days after the end of therapy) in the microbiological ITT (mITT) population.

RESULTS

The mITT population comprised 511 participants (264 ceftolozane/tazobactam, 247 meropenem). Baseline LRT pathogens included Klebsiella pneumoniae (34.6%), Pseudomonas aeruginosa (25.0%) and Escherichia coli (18.2%). Among baseline Enterobacterales isolates, 171/456 (37.5%) were ESBL positive. For Gram-negative baseline LRT pathogens, susceptibility rates were 87.0% for ceftolozane/tazobactam and 93.3% for meropenem. For Gram-negative pathogens, 28 day ACM [52/259 (20.1%) and 62/240 (25.8%)], clinical cure rates [157/259 (60.6%) and 137/240 (57.1%)] and microbiological eradication rates [189/259 (73.0%) and 163/240 (67.9%)] were comparable with ceftolozane/tazobactam and meropenem, respectively. Per-pathogen microbiological eradication for Enterobacterales [145/195 (74.4%) and 129/185 (69.7%); 95% CI: -4.37 to 13.58], ESBL-producing Enterobacterales [56/84 (66.7%) and 52/73 (71.2%); 95% CI: -18.56 to 9.93] and P. aeruginosa [47/63 (74.6%) and 41/65 (63.1%); 95% CI: -4.51 to 19.38], respectively, were also comparable.

CONCLUSIONS

In mechanically ventilated participants with nosocomial pneumonia owing to Gram-negative pathogens, ceftolozane/tazobactam was comparable with meropenem for per-pathogen 28 day ACM and clinical and microbiological response.

Prophylactic application of antibiotics selects extended-spectrum β-lactamase and carbapenemases producing Gram-negative bacteria in the oral cavity

Prophylactic administration of broad-spectrum antibiotics in surgery can change the oral microbiome and induce colonization of oral cavity with Gram-negative bacteria including multidrug (MDR) or extensively drug resistant (XDR) organisms which can lead to lower respiratory tract infections. The aim of the study was to analyse the Gram-negative isolates obtained from oral cavity of the mechanically ventilated patients in ICUs, after prophylactic application of antibiotics and their resistance mechanisms and to compare them with the isolates obtained from tracheal aspirates from the same patients. The antibiotic susceptibility was determined by broth dilution method. PCR was applied to detect genes encoding β-lactamases. Marked diversity of Gram-negative bacteria and resistance mechanisms was found. High resistance rates and high rate of bla_CTX-M and carbapenemase encoding genes (bla_VIM-1 , bla_OXA-48 ) were found among Klebsiella pneumoniae. Pseudomonas aeruginosa was found to harbour bla_VIM and in one strain bla_PER-1 gene, whereas Acinetobacter baumannii produced OXA-23-like and OXA-24/40-like oxacillinases and was XDR in all except one case. All XDR isolates belong to international clonal lineage II (IC II). The main finding of the study is that the prophlylactic application of antibiotics in surgery intensive care units (ICUs) is associated with the colonization of oral cavity and lower respiratory tract with Gram-negative bacteria. The identity of Gram-negative bacteria in oral cavity reflected those found in endotracheal aspirates leading to conclusion that oral swab as non-invasive specimen can predict the colonization of lower respiratory tract with resistant Gram-negative organisms and the risk for development of ventilator-associated pneumonia.

A comparison of diagnostic algorithms and clinical parameters to diagnose ventilator-associated pneumonia: a prospective observational study

Background

Suspicion and clinical criteria continue to serve as the foundation for ventilator-associated pneumonia (VAP) diagnosis, however the criteria used to diagnose VAP vary widely. Data from head-to-head comparisons of clinical diagnostic algorithms is lacking, thus a prospective observational study was performed to determine the performance characteristics of the Johanson criteria, Clinical Pulmonary Infection Score (CPIS), and Centers for Disease Control and Prevention’s National Healthcare Safety Network (CDC/NHSN) criteria as compared to Hospital in Europe Link for Infection Control through Surveillance (HELICS) reference standard.

Methods

A prospective observational cohort study was performed in three mixed medical-surgical ICUs from one academic medical center from 1 October 2016 to 30 April 2018. VAP diagnostic criteria were applied to each patient including CDC/NHSN, CPIS, HELICS and Johanson criteria. Tracheal aspirate cultures (TAC) and serum procalcitonin values were obtained for each patient.

Results

Eighty-five patients were enrolled (VAP 45, controls 40). Using HELICS as the reference standard, the sensitivity and specificity for each of the assessed diagnostic algorithms were: CDC/NHSN (Sensitivity 54.2%; Specificity 100%), CPIS (Sensitivity 68.75%; Specificity 95.23%), Johanson (Sensitivity 67.69%; Specificity 95%). The positive TAC rate was 81.2%. The sensitivity for positive TAC with the serum procalcitonin level > 0.5 ng/ml was 51.8%.

Conclusion

VAP remains a considerable source of morbidity and mortality in modern intensive care units. The optimal diagnostic method remains unclear. Using HELICS criteria as the reference standard, CPIS had the greatest comparative diagnostic accuracy, whereas the sensitivity of the CDC/NHSN was only marginally better than a positive TAC plus serum procalcitonin > 0.5 ng/ml. Algorithm accuracy was improved by adding serum procalcitonin > 0.5 ng/ml, but not positive quantitative TAC.

Trial Registration: Not indicated for this study type.

Pharmacodynamics of once- versus twice-daily dosing of nebulized amikacin in an in vitro Hollow-Fiber Infection Model against 3 clinical isolates of Pseudomonas aeruginosa

This study aims to compare the bacterial killing of once- versus twice-daily nebulized amikacin against Pseudomonas aeruginosa and to determine the optimal duration of therapy. Three clinical P. aeruginosa isolates (amikacin MICs 2, 8, and 64 mg/L) were exposed to simulated epithelial lining fluid exposures of nebulized amikacin with dosing regimens of 400 mg and 800 mg once- or twice-daily up to 7-days using the in vitro hollow-fiber infection model. Quantitative cultures were performed. Simulated amikacin dosing regimens of 400 mg twice-daily and 800 mg once-daily achieved ≥2-log reduction in the bacterial burden within the first 24-hours of therapy for all isolates tested. No dosing regimen suppressed the emergence of amikacin resistance. No difference in bacterial killing or regrowth was observed between 3- and 7-days of amikacin. Amikacin doses of 800 mg once-daily for up to 3-days may be considered for future clinical trials.

Risk Factors of Multidrug-Resistant Bacteria in Lower Respiratory Tract Infections: A Systematic Review and Meta-Analysis

Background

Multidrug-resistant (MDR) bacteria are the main cause of lower respiratory tract infections (LRTIs) with high mortality. The purpose of this study is to identify the risk factors associated with MDR by performing a systematic review and meta-analysis.

Methods

PubMed, EMBASE (via Ovid), and Cochrane Library were systematically searched for studies on the risk factors for MDR bacteria in LRTIs as of November 30, 2019. Literature screening, data abstraction, and quality assessment of the eligible studies were performed independently by two researchers.

Results

A total of 3,607 articles were retrieved, of which 21 articles representing 20 cohort studies published in English were included after title/abstract and full-text screening. Among the 21 articles involving 7,650 patients and 1,360 MDR organisms, ten reported the risk factors for MDR Gram-positive bacteria (GPB) and Gram-negative bacteria (GNB), ten for MDR GNB, and one for MDR GPB. The meta-analysis results suggested that prior antibiotic treatment, inappropriate antibiotic therapy, chronic lung disease, chronic liver disease and cerebral disease, prior MDR and PA infection/colonization, recent hospitalization, longer hospitalization stay, endotracheal tracheostomy and mechanical ventilation, tube feeding, nursing home residence, and higher disease severity score were independent risk factors for MDR bacteria.

Conclusions

This review identified fourteen clinical factors that might increase the risk of MDR bacteria in patients with LRTIs. Clinicians could take into account these factors when selecting antibiotics for patients and determine whether coverage for MDR bacteria is required. More well-designed studies are needed to confirm the various risk factors for MDR bacteria in the future.

Impact of multi-drug resistant bacteria on economic and clinical outcomes of healthcare-associated infections in adults: Systematic review and meta-analysis

Background

Infections with multidrug resistant (MDR) bacteria in hospital settings have substantial implications in terms of clinical and economic outcomes. However, due to clinical and methodological heterogeneity, estimates about the attributable economic and clinical effects of healthcare-associated infections (HAI) due to MDR microorganisms (MDR HAI) remain unclear. The objective was to review and synthesize the evidence on the impact of MDR HAI in adults on hospital costs, length of stay, and mortality at discharge.

Methods and findings

Literature searches were conducted in PubMed/MEDLINE, and Google Scholar databases to select studies that evaluated the impact of MDR HAI on economic and clinical outcomes. Eligible studies were conducted in adults, in order to ensure homogeneity of populations, used propensity score matched cohorts or included explicit confounding control, and had confirmed antibiotic susceptibility testing. Risk of bias was evaluated, and effects were measured with ratios of means (ROM) for cost and length of stay, and risk ratios (RR) for mortality. A systematic search was performed on 14^th March 2019, re-run on the 10^th of June 2019 and extended the 3^rd of September 2019. Small effect sizes were assessed by examination of funnel plots. Sixteen articles (6,122 patients with MDR HAI and 8,326 patients with non-MDR HAI) were included in the systematic review of which 12 articles assessed cost, 19 articles length of stay, and 14 mortality. Compared to susceptible infections, MDR HAI were associated with increased cost (ROM 1.33, 95%CI [1.15; 1.54]), prolonged length of stay (ROM 1.27, 95%CI [1.18; 1.37]), and excess in-hospital mortality (RR 1.61, 95%CI [1.36; 1.90]) in the random effects models. Risk of publication bias was only found to be significant for mortality, and overall study quality good.

Conclusions

MDR HAI appears to be strongly associated with increases in direct cost, prolonged length of stay and increased mortality. However, further comprehensive studies in this setting are warranted.

Trial registration

PROSPERO (CRD42019126288).

Incidence and Risk Factors Associated with Multi-Drug-Resistant Pathogens in a Critically Ill Trauma Population: A Retrospective Cohort Study

Background: Multi-drug resistance is considered a serious health threat particularly in the intensive care unit (ICU) setting. Studies evaluating multi-drug-resistant (MDR) pathogens in critically ill trauma patients are limited. The objectives were to describe the incidence of MDR, extensive-drug-resistant (XDR), and pan-drug-resistant (PDR) organism growth in ICU patients admitted with traumatic injuries and to identify any risk factors associated with MDR growth. Patients and Methods: This was a retrospective single-center cohort study of all ICU adult patients identified via the institution's trauma registry from January 1, 2016 to August 31, 2017. Patients were included if they had positive culture growth with susceptibility data taken during the index hospitalization. Patients were excluded if their cultures were drawn within 48 hours of emergency department triage. Study groups were defined based on the presence of at least one MDR pathogen during the index hospitalization. Results: A total of 2,578 charts were reviewed and 95 patients (mean age, 60 years; 66 males [69%]) with 201 total cultures were included. The majority of positive cultures were from respiratory (69%) and urinary (16%) sources. Of the 201 positive cultures, the majority of species identified was Enterobacteriaceae (47%), Staphylococcus (32%), Enterococcus (7%), Acinetobacter (5%), and Pseudomonas (3%). Of the 95 patients with positive cultures, the incidence of MDR, XDR, and PDR organisms was found to be 31%, 17%, and 0%, respectively. Augmented renal clearance (ARC) was the only risk factor associated with an increased risk for MDR organism growth (adjusted odds ratio 9.78, 95% confidence interval [CI] 2.56-37.41; p = 0.001). Conclusions: In this cohort of critically ill trauma patients, the incidence of an MDR pathogen occurred in 31% of patients. This is the first study to find an association of ARC and multi-drug resistance, which should be further validated as a potential cause for MDR organisms.

Why don't we have more inhaled antibiotics to treat ventilator-associated pneumonia?

BACKGROUND

The increasing prevalence of ventilator-associated pneumonia (VAP) due to either multidrug-resistant (MDR) organisms or infections with limited treatment options (i.e. susceptible to only aminoglycosides or colisitin) coupled with a dearth of new antimicrobials has led clinicians to pursue alternative management strategies including the use of inhaled antibiotics (IA).

OBJECTIVES

To review the evidence surrounding the use of IA in the treatment of VAP with a focus on establishing a path whereby adjunctive IA could become a standard therapy for the treatment of specific VAP patient populations.

SOURCES

A meta-analysis performed by the 2016 IDSA/ATS Hospital-acquired Pneumonia Guideline Committee; a PubMed and clinicaltrials.gov search for subsequent trials of IA for the treatment of VAP.

CONTENT

Based on a meta-analysis of nine studies (RR 1.29; 95% CI 1.13-1.47), the 2016 IDSA/ATS Hospital-acquired Pneumonia Guideline Committee recommended that adjunctive IA be used to treat VAP due to Gram-negative bacilli that are susceptible to only aminoglycosides or polymyxins. Two subsequent randomized trials of adjunctive IA for the treatment of mechanically ventilated patients with pneumonia failed to demonstrate a benefit. Despite these results, an updated meta-analysis (n = 11) including these two recent trials suggests a benefit of adjunctive IA for the treatment of VAP due to MDR and difficult-to-treat infections (RR 1.2; 95% CI 1.05-1.57).

IMPLICATIONS

Patients with VAP and limited intravenous antibiotic options are the individuals most likely to benefit from adjunctive IA and should be the focus of future investigative studies. Although vibrating mesh nebulizers predominate in pharmaceutical company-sponsored trials, these devices have not been directly compared with the traditional jet nebulizers in terms of efficacy or safety.

Estimating the burden of antimicrobial resistance: a systematic literature review

Background

Accurate estimates of the burden of antimicrobial resistance (AMR) are needed to establish the magnitude of this global threat in terms of both health and cost, and to paramaterise cost-effectiveness evaluations of interventions aiming to tackle the problem. This review aimed to establish the alternative methodologies used in estimating AMR burden in order to appraise the current evidence base.

Methods

MEDLINE, EMBASE, Scopus, EconLit, PubMed and grey literature were searched. English language studies evaluating the impact of AMR (from any microbe) on patient, payer/provider and economic burden published between January 2013 and December 2015 were included. Independent screening of title/abstracts followed by full texts was performed using pre-specified criteria. A study quality score (from zero to one) was derived using Newcastle-Ottawa and Philips checklists. Extracted study data were used to compare study method and resulting burden estimate, according to perspective. Monetary costs were converted into 2013 USD.

Results

Out of 5187 unique retrievals, 214 studies were included. One hundred eighty-seven studies estimated patient health, 75 studies estimated payer/provider and 11 studies estimated economic burden. 64% of included studies were single centre. The majority of studies estimating patient or provider/payer burden used regression techniques. 48% of studies estimating mortality burden found a significant impact from resistance, excess healthcare system costs ranged from non-significance to $1 billion per year, whilst economic burden ranged from $21,832 per case to over $3 trillion in GDP loss. Median quality scores (interquartile range) for patient, payer/provider and economic burden studies were 0.67 (0.56-0.67), 0.56 (0.46-0.67) and 0.53 (0.44-0.60) respectively.

Conclusions

This study highlights what methodological assumptions and biases can occur dependent on chosen outcome and perspective. Currently, there is considerable variability in burden estimates, which can lead in-turn to inaccurate intervention evaluations and poor policy/investment decisions. Future research should utilise the recommendations presented in this review.

Trial registration

This systematic review is registered with PROSPERO (PROSPERO CRD42016037510).

Treatment of infected lungs by ex vivo perfusion with high dose antibiotics and autotransplantation: A pilot study in pigs

The emergence of multi-drug resistant bacteria threatens to end the era of antibiotics. Drug resistant bacteria have evolved mechanisms to overcome antibiotics at therapeutic doses and further dose increases are not possible due to systemic toxicity. Here we present a pilot study of ex vivo lung perfusion (EVLP) with high dose antibiotic therapy followed by autotransplantation as a new therapy of last resort for otherwise incurable multidrug resistant lung infections. Severe Pseudomonas aeruginosa pneumonia was induced in the lower left lungs (LLL) of 18 Mini-Lewe pigs. Animals in the control group (n = 6) did not receive colistin. Animals in the conventional treatment group (n = 6) received intravenous application of 2 mg/kg body weight colistin daily. Animals in the EVLP group (n = 6) had their LLL explanted and perfused ex vivo with a perfusion solution containing 200 μg/ml colistin. After two hours of ex vivo treatment, autotransplantation of the LLL was performed. All animals were followed for 4 days following the initiation of treatment. In the control and conventional treatment groups, the infection-related mortality rate after five days was 66.7%. In the EVLP group, there was one infection-related mortality and one procedure-related mortality, for an overall mortality rate of 33.3%. Moreover, the clinical symptoms of infection were less severe in the EVLP group than the other groups. Ex vivo lung perfusion with very high dose antibiotics presents a new therapeutic option of last resort for otherwise incurable multidrug resistant pneumonia without toxic side effects on other organs.

Development and validation of an automated ventilator-associated event electronic surveillance system: A report of a successful implementation

BACKGROUND

Surveillance is an important tool for infection control; however, this task can often be time-consuming and take away from infection prevention activities. With the increasing availability of comprehensive electronic health records, there is an opportunity to automate these surveillance activities. The objective of this article is to describe the implementation of an electronic algorithm for ventilator-associated events (VAEs) at a large academic medical center METHODS: This article reports on a 6-month manual validation of a dashboard for VAEs. We developed a computerized algorithm for automatically detecting VAEs and compared the output of this algorithm to the traditional, manual method of VAE surveillance.

RESULTS

Manual surveillance by the infection preventionists identified 13 possible and 11 probable ventilator-associated pneumonias (VAPs), and the VAE dashboard identified 16 possible and 13 probable VAPs. The dashboard had 100% sensitivity and 100% accuracy when compared with manual surveillance for possible and probable VAP. We report on the successfully implemented VAE dashboard. Workflow of the infection preventionists was simplified after implementation of the dashboard with subjective time-savings reported.

CONCLUSIONS

Implementing a computerized dashboard for VAE surveillance at a medical center with a comprehensive electronic health record is feasible; however, this required significant initial and ongoing work on the part of data analysts and infection preventionists.

Antibiotic dosing for multidrug-resistant pathogen pneumonia

PURPOSE OF REVIEW

Nosocomial pneumonia caused by multidrug-resistant pathogens is increasing in the ICU, and these infections are negatively associated with patient outcomes. Optimization of antibiotic dosing has been suggested as a key intervention to improve clinical outcomes in patients with nosocomial pneumonia. This review describes the recent pharmacokinetic/pharmacodynamic data relevant to antibiotic dosing for nosocomial pneumonia caused by multidrug-resistant pathogens.

RECENT FINDINGS

Optimal antibiotic treatment is challenging in critically ill patients with nosocomial pneumonia; most dosing guidelines do not consider the altered physiology and illness severity associated with severe lung infections. Antibiotic dosing can be guided by plasma drug concentrations, which do not reflect the concentrations at the site of infection. The application of aggressive dosing regimens, in accordance to the antibiotic's pharmacokinetic/pharmacodynamic characteristics, may be required to ensure rapid and effective drug exposure in infected lung tissues.

SUMMARY

Conventional antibiotic dosing increases the likelihood of therapeutic failure in critically ill patients with nosocomial pneumonia. Alternative dosing strategies, which exploit the pharmacokinetic/pharmacodynamic properties of an antibiotic, should be strongly considered to ensure optimal antibiotic exposure and better therapeutic outcomes in these patients.

Population Genomic Analysis of 1,777 Extended-Spectrum Beta-Lactamase-Producing Klebsiella pneumoniae Isolates, Houston, Texas: Unexpected Abundance of Clonal Group 307

Klebsiella pneumoniae is a major human pathogen responsible for high morbidity and mortality rates. The emergence and spread of strains resistant to multiple antimicrobial agents and documented large nosocomial outbreaks are especially concerning. To develop new therapeutic strategies for K. pneumoniae, it is imperative to understand the population genomic structure of strains causing human infections. To address this knowledge gap, we sequenced the genomes of 1,777 extended-spectrum beta-lactamase-producing K. pneumoniae strains cultured from patients in the 2,000-bed Houston Methodist Hospital system between September 2011 and May 2015, representing a comprehensive, population-based strain sample. Strains of largely uncharacterized clonal group 307 (CG307) caused more infections than those of well-studied epidemic CG258. Strains varied markedly in gene content and had an extensive array of small and very large plasmids, often containing antimicrobial resistance genes. Some patients with multiple strains cultured over time were infected with genetically distinct clones. We identified 15 strains expressing the New Delhi metallo-beta-lactamase 1 (NDM-1) enzyme that confers broad resistance to nearly all beta-lactam antibiotics. Transcriptome sequencing analysis of 10 phylogenetically diverse strains showed that the global transcriptome of each strain was unique and highly variable. Experimental mouse infection provided new information about immunological parameters of host-pathogen interaction. We exploited the large data set to develop whole-genome sequence-based classifiers that accurately predict clinical antimicrobial resistance for 12 of the 16 antibiotics tested. We conclude that analysis of large, comprehensive, population-based strain samples can assist understanding of the molecular diversity of these organisms and contribute to enhanced translational research.IMPORTANCEKlebsiella pneumoniae causes human infections that are increasingly difficult to treat because many strains are resistant to multiple antibiotics. Clonal group 258 (CG258) organisms have caused outbreaks in health care settings worldwide. Using a comprehensive population-based sample of extended-spectrum beta-lactamase (ESBL)-producing K. pneumoniae strains, we show that a relatively uncommon clonal type, CG307, caused the plurality of ESBL-producing K. pneumoniae infections in our patients. We discovered that CG307 strains have been abundant in Houston for many years. As assessed by experimental mouse infection, CG307 strains were as virulent as pandemic CG258 strains. Our results may portend the emergence of an especially successful clonal group of antibiotic-resistant K. pneumoniae.

Timeline of health care-associated infections and pathogens after burn injuries

BACKGROUND

Infections are an important cause of morbidity and mortality after burn injuries. Here, we describe the time line of infections and pathogens after burns.

METHODS

A retrospective study was performed in a large tertiary care burn center from 2004-2013. Analyses were performed on health care-associated infections (HAIs) meeting Centers for Disease Control and Prevention criteria and on all positive cultures. Incidence rates per 1,000 days were calculated for specific HAI categories and pathogens and across hospitalization time (week 1, weeks 2-3, and week ≥4).

RESULTS

Among 5,524 patients, the median burn size was 4% of total body surface area (interquartile range, 2%-10%). Of the patients, 7% developed an HAI, of whom 33% had >1 HAI episode. Gram-positive bacteria were isolated earlier, and gram-negative bacteria were isolated later during hospitalization. Of 1,788 bacterial isolates, 44% met criteria for multidrug resistance, and 23% met criteria for extensive drug resistance. Bacteria tended to become increasingly resistant to antibiotics as time from admission increased.

CONCLUSIONS

We observed differences in infection type, pathogen, and antibiotic-resistant bacterium risk across time of hospitalization. These results may guide infection prevention in various stages of the postburn admission.

Emerging drugs for nosocomial pneumonia

INTRODUCTION

Hospital-acquired pneumonia (HAP) is one of the leading nosocomial infections worldwide and is associated with an elevated morbidity and mortality and increased hospital costs. Nevertheless, prompt and adequate antimicrobial treatment is mandatory following VAP development, especially in the face of multidrug resistant pathogens.

AREAS COVERED

We searched Pubmed and ClinicalTrials.gov site reports in English language of phase III clinical trials, between 2000-2016 referring to the antibiotic treatment of nosocomial pneumonia. We provide a summary of latest approved drugs for HAP and emerging drugs with potential indication nosocomial pneumonia.

EXPERT OPINION

There are several promising compounds on their way, as tedizolid-a new oxazolidone, iclaprim-a novel drug, related to trimethoprim, plazomicin-a new aminoglycoside and two combinations of ceftazidime/avibactam and ceftolozane/tazobactam against MDR bacteria, especially against MRSA and Gram-negative ESBL bacteria.

Spectrum of excess mortality due to carbapenem-resistant Klebsiella pneumoniae infections

Patients infected or colonized with carbapenem-resistant Klebsiella pneumoniae (CRKp) are often chronically and acutely ill, which results in substantial mortality unrelated to infection. Therefore, estimating excess mortality due to CRKp infections is challenging. The Consortium on Resistance against Carbapenems in K. pneumoniae (CRACKLE) is a prospective multicenter study. Here, patients in CRACKLE were evaluated at the time of their first CRKp bloodstream infection (BSI), pneumonia or urinary tract infection (UTI). A control cohort of patients with CRKp urinary colonization without CRKp infection was constructed. Excess hospital mortality was defined as mortality in cases after subtracting mortality in controls. In addition, the adjusted hazard ratios (aHR) for time-to-hospital-mortality at 30 days associated with infection compared with colonization were calculated in Cox proportional hazard models. In the study period, 260 patients with CRKp infections were included in the BSI (90 patients), pneumonia (49 patients) and UTI (121 patients) groups, who were compared with 223 controls. All-cause hospital mortality in controls was 12%. Excess hospital mortality was 27% in both patients with BSI and those with pneumonia. Excess hospital mortality was not observed in patients with UTI. In multivariable analyses, BSI and pneumonia compared with controls were associated with aHR of 2.59 (95% CI 1.52-4.50, p <0.001) and 3.44 (95% CI 1.80-6.48, p <0.001), respectively. In conclusion, in patients with CRKp infection, pneumonia is associated with the highest excess hospital mortality. Patients with BSI have slightly lower excess hospital mortality rates, whereas excess hospital mortality was not observed in hospitalized patients with UTI.

Treatment of Gram-negative pneumonia in the critical care setting: is the beta-lactam antibiotic backbone broken beyond repair?

Beta-lactam antibiotics form the backbone of treatment for Gram-negative pneumonia in mechanically ventilated patients in the intensive care unit. However, this beta-lactam antibiotic backbone is increasingly under pressure from emerging resistance across all geographical regions, and health-care professionals in many countries are rapidly running out of effective treatment options. Even in regions that currently have only low levels of resistance, the effects of globalization are likely to increase local pressures on the beta-lactam antibiotic backbone in the near future. Therefore, clinicians are increasingly faced with a difficult balancing act: the need to prescribe adequate and appropriate antibiotic therapy while reducing the emergence of resistance and the overuse of antibiotics. In this review, we explore the burden of Gram-negative pneumonia in the critical care setting and the pressure that antibiotic resistance places on current empiric therapy regimens (and the beta-lactam antibiotic backbone) in this patient population. New treatment approaches, such as systemic and inhaled antibiotic alternatives, are on the horizon and are likely to help tackle the rising levels of beta-lactam antibiotic resistance. In the meantime, it is imperative that the beta-lactam antibiotic backbone of currently available antibiotics be supported through stringent antibiotic stewardship programs.

Ventilator-Associated Pneumonia (VAP) with Multidrug-Resistant (MDR) Pathogens: Optimal Treatment?

Ventilator-associated pneumonia (VAP) due to multidrug-resistant bacteria (MDR) is an emerging problem worldwide. Both gram-negative and gram-positive microorganisms are associated with VAP. We first describe the magnitude of the problem of MDR VAP followed by its clinical impact on survival outcomes, with the primary aim to review the optimal antibiotic choices to treat patients with MDR VAP. We discuss the challenges of intravenous and inhaled antibiotic treatments, as well as of monotherapy and combination antimicrobial therapies.