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

Pseudomonas aeruginosa senses and responds to epithelial potassium flux via Kdp operon to promote biofilm

Mucosa-associated biofilms are associated with many human disease states, but the host mechanisms promoting biofilm remain unclear. In chronic respiratory diseases like cystic fibrosis (CF), Pseudomonas aeruginosa establishes chronic infection through biofilm formation. P. aeruginosa can be attracted to interspecies biofilms through potassium currents emanating from the biofilms. We hypothesized that P. aeruginosa could, similarly, sense and respond to the potassium efflux from human airway epithelial cells (AECs) to promote biofilm. Using respiratory epithelial co-culture biofilm imaging assays of P. aeruginosa grown in association with CF bronchial epithelial cells (CFBE41o-), we found that P. aeruginosa biofilm was increased by potassium efflux from AECs, as examined by potentiating large conductance potassium channel, BKCa (NS19504) potassium efflux. This phenotype is driven by increased bacterial attachment and increased coalescence of bacteria into aggregates. Conversely, biofilm formation was reduced when AECs were treated with a BKCa blocker (paxilline). Using an agar-based macroscopic chemotaxis assay, we determined that P. aeruginosa chemotaxes toward potassium and screened transposon mutants to discover that disruption of the high-sensitivity potassium transporter, KdpFABC, and the two-component potassium sensing system, KdpDE, reduces P. aeruginosa potassium chemotaxis. In respiratory epithelial co-culture biofilm imaging assays, a KdpFABCDE deficient P. aeruginosa strain demonstrated reduced biofilm growth in association with AECs while maintaining biofilm formation on abiotic surfaces. Furthermore, we determined that the Kdp operon is expressed in vivo in people with CF and the genes are conserved in CF isolates. Collectively, these data suggest that P. aeruginosa biofilm formation can be increased by attracting bacteria to the mucosal surface and enhancing coalescence into microcolonies through aberrant AEC potassium efflux sensed by the KdpFABCDE system. These findings suggest host electrochemical signaling can enhance biofilm, a novel host-pathogen interaction, and potassium flux could be a therapeutic target to prevent chronic infections in diseases with mucosa-associated biofilms, like CF.

Clinical and microbiological evaluation of ventilator-associated pneumonia in an intensive care unit in Vietnam

Background

The increasing incidence of multidrug-resistant Gram-negative bacteria causing ventilator-associated pneumonia (VAP) is a global concern. A better understanding of the epidemiology of VAP in Southeast Asia is essential to optimise treatments and patient outcomes.

Methods

VAP epidemiology in an intensive care unit in Vietnam was investigated. A prospective cohort study was conducted. Patients who were ventilated for >48 hours, diagnosed with VAP, and had a positive respiratory culture between October 2015 and March 2017 were included. Whole-genome sequencing (WGS) was performed on Acinetobacter baumannii isolates.

Results

We identified 125 patients (137 episodes) with VAP from 1,699 admissions. Twelve patients had 2 VAP episodes. The median age was 60 years (interquartile range: 48-70), and 68.8% of patients were male. Diabetes mellitus was the most frequent comorbidity (N=35, 28%). Acinetobacter baumannii was most frequently isolated in the first VAP episode (N=84, 67.2%) and was multiply resistant to meropenem, levofloxacin, and amikacin. The 30-day mortality rate was 55.2% (N=69) and higher in patients infected with A. baumannii (N=52, 65%). WGS results suggested a complex spread of multiple clones.

Conclusions

In an intensive care unit in Vietnam, VAP due to A. baumannii had a high mortality rate, and A. baumannii and K. pneumoniae were multidrug resistant, with carbapenem resistance of 97% and 70%, respectively.

Effect of mechanical ventilation under intubation on respiratory tract change of bacterial count and alteration of bacterial flora

Background: The most common 'second strike' in mechanically ventilated patients is a pulmonary infection caused by the ease with which bacteria can invade and colonize the lungs due to mechanical ventilation. At the same time, metastasis of lower airway microbiota may have significant implications in developing intubation mechanical ventilation lung inflammation. Thus, we establish a rat model of tracheal intubation with mechanical ventilation and explore the effects of mechanical ventilation on lung injury and microbiological changes in rats. To provide a reference for preventing and treating bacterial flora imbalance and pulmonary infection injury caused by mechanical ventilation of tracheal intubation. Methods: Sprague-Dawley rats were randomly divided into Control, Mechanical ventilation under intubation (1, 3, 6 h) groups, and Spontaneously breathing under intubation (1, 3, 6 h). Lung histopathological injury scores were evaluated. 16SrDNA sequencing was performed to explore respiratory microbiota changes, especially, changes of bacterial count and alteration of bacterial flora. Results: Compared to groups C and SV, critical pathological changes in pulmonary lesions occurred in the MV group after 6 h (p < 0.05). The Alpha diversity and Beta diversity of lower respiratory tract microbiota in MV6, SV6, and C groups were statistically significant (p < 0.05). The main dominant bacterial phyla in the respiratory tract of rats were Proteobacteria, Firmicutes, Bacteroidetes, and Cyanobacteria. Acinetobacter radioresistens in group C was significant, Megaonas in group MV6 was significantly increased, and Parvibacter in group SV6 was significantly increased. Anaerobic, biofilm formation, and Gram-negative bacteria-related functional genes were altered during mechanical ventilation with endotracheal intubation. Conclusion: Mechanical ventilation under intubation may cause dysregulation of lower respiratory microbiota in rats.

Use of polymyxin B with different administration methods in the critically ill patients with ventilation associated pneumonia: a single-center experience

Background: Whether nebulized polymyxin B should be used as an adjunctive therapy or substitution strategy to intravenous polymyxin B for the treatment of ventilator-associated pneumonia (VAP) remains controversial. This study's aim is to evaluate the efficacy and safety of different administration ways of polymyxin B in the treatment of ventilator-associated pneumonia caused by extensively drug-resistant Gram-negative bacteria(XDR-GNB). Methods: This retrospective cohort study enrolled ventilator-associated pneumonia patients caused by XDR-GNB treated with polymyxin B in the intensive care unit. Patients were categorized by the administration methods as intravenous (IV) group, inhaled (IH) group, and the intravenous combined with inhaled (IV + IH) group. Microbiological outcome and clinical outcome were compared in each group. The side effects were also explored. Results: A total of 111 patients were enrolled and there was no difference in demographic and clinical characteristics among the three groups. In terms of efficacy, clinical cure or improvement was achieved in 21 patients (55.3%) in the intravenous group, 19 patients (50%) in the IH group, and 20 patients (57.1%) in IV + IH group (p = 0.815). All three groups showed high success rates in microbiological eradication, as 29 patients with negative cultures after medication in inhaled group. Among all the patients who had negative bacterial cultures after polymyxin B, the inhaled group had significantly shorter clearance time than the intravenous group (p = 0.002), but with no significant difference in 28-day mortality. Compared with intravenous group, a trend towards a lower risk of acute kidney injury was observed in inhaled group (p = 0.025). Conclusion: From the perspective of minimal systemic renal toxicity, nebulized polymyxin B as a substitution strategy to intravenous polymyxin B for the treatment of ventilator-associated pneumonia caused by XDR-GNB is feasible.

Infection in systemic lupus erythematosus-associated diffuse alveolar hemorrhage: a potential key to improve outcomes

OBJECTIVES

This study aimed to investigate the clinical characteristics, outcomes, and associated factors of patients with systemic lupus erythematosus-associated diffusive alveolar hemorrhage (SLE-DAH) stratified by infection status in a national representative cohort.

METHODS

This single-center retrospective study included 124 consecutive patients with SLE-DAH in a tertiary care center between 2006 and 2021. The diagnosis of DAH was made based on a comprehensive evaluation of clinical manifestations, laboratory and radiologic findings, and bronchoalveolar lavage. Demographics, clinical features, and survival curves were compared between patients with bacterial, non-bacterial, and non-infection groups. Univariate and multivariate logistic regression analyses were performed to determine the factors independently associated with bacterial infection in SLE-DAH.

RESULTS

Fifty-eight patients with SLE-DAH developed bacterial infection after DAH occurrence, thirty-two patients developed fungal and/or viral infection, and thirty-four patients were categorized as non-infection. The bacterial infection group have a worse prognosis (OR 3.059, 95%CI 1.469-6.369, p = 0.002) compared with the other two groups, with a mortality rate of 60.3% within 180 days after DAH occurrence. Factors independently associated with bacterial infections in SLE-DAH included hematuria (OR 4.523, 95%CI 1.068-19.155, p = 0.040), hemoglobin drop in the first 24 h after DAH occurred (OR 1.056, 95%CI 1.001-1.115, p = 0.049), and anti-Smith antibody (OR 0.167, 95%CI 0.052-0.535, p = 0.003). Glucocorticoid pulse therapy and cyclophosphamide were administered in more than 50% of patients regardless of their infectious status. According to clinical experience at our hospital and in previous studies, we recommended a comprehensive management algorithm for SLE-DAH based on infection stratification.

CONCLUSION

Infection, especially bacterial infection, is a severe complication and prognostic factor of SLE-DAH. Comprehensive management strategies, including diagnosis, evaluation, treatment, and monitoring, based on infection stratification may fundamentally improve outcomes of patients with SLE-DAH. Key Points • Bacterial infection is an important, but neglected, prognosis factor of systemic lupus erythematosus (SLE)-associated diffusive alveolar hemorrhage (DAH). • Hematuria, hemoglobin drop, and anti-Smith antibody can independently predict bacterial infections in SLE-DAH. • We put forward a comprehensive management algorithm based on infection stratification for SLE-DAH.

Clinical Efficacy and In Vitro Drug Sensitivity Test Results of Azithromycin Combined With Other Antimicrobial Therapies in the Treatment of MDR P. aeruginosa Ventilator-Associated Pneumonia

Objective: The aim of the research was to study the effect of azithromycin (AZM) in the treatment of MDR P. aeruginosa VAP combined with other antimicrobial therapies.

Methods: The clinical outcomes were retrospectively collected and analyzed to elucidate the efficacy of different combinations involving azithromycin in the treatment of MDR-PA VAP. The minimal inhibitory concentration (MIC) of five drugs was measured by the agar dilution method against 27 isolates of MDR-PA, alone or in combination.

Results: The incidence of VAP has increased approximately to 10.4% (961/9245) in 5 years and 18.4% (177/961) caused by P. aeruginosa ranking fourth. A total of 151 cases of MDR P. aeruginosa were included in the clinical retrospective study. Clinical efficacy results are as follows: meropenem + azithromycin (MEM + AZM) was 69.2% (9/13), cefoperazone/sulbactam + azithromycin (SCF + AZM) was 60% (6/10), and the combination of three drugs containing AZM was 69.2% (9/13). The curative effect of meropenem + amikacin (MEM + AMK) was better than that of the meropenem + levofloxacin (MEM + LEV) group, p = 0.029 (p < 0.05). The curative effect of cefoperazone/sulbactam + amikacin (SCF + AMK) was better than that of the cefoperazone/sulbactam + levofloxacin (SCF + LEV) group, p = 0.025 (p < 0.05). There was no significant difference between combinations of two or three drugs containing AZM, p > 0.05 (p = 0.806). From the MIC results, the AMK single drug was already very sensitive to the selected strains. When MEM or SCF was combined with AZM, the sensitivity of them to strains can be significantly increased. When combined with MEM and AZM, the MIC₅₀ and MIC₉₀ of MEM decreased to 1 and 2 ug/mL from 8 to 32 ug/mL. When combined with SCF + AZM, the MIC₅₀ of SCF decreased to 16 ug/mL, and the curve shifted obviously. However, for the combination of SCF + LEV + AZM, MIC₅₀ and MIC₉₀ could not achieve substantive changes. From the FIC index results, the main actions of MEM + AZM were additive effects, accounting for 72%; for the combination of SCF + AZM, the additive effect was 40%. The combination of AMK or LEV with AZM mainly showed unrelated effects, and the combination of three drugs could not improve the positive correlation between LEV and AZM.

Conclusion: AZM may increase the effect of MEM or SCF against MDR P. aeruginosa VAP. Based on MEM or SCF combined with AMK or AZM, we can achieve a good effect in the treatment of MDR P. aeruginosa VAP.

Retrospective Assessment of Ventilator-Associated Pneumonias due to Acinetobacter baumannii in an Oncology Hospital

Objectives:

Ventilator-associated pneumonia (VAP) is associated with significant morbidity and mortality in critically ill patients and leads to increases in health-care costs. However, it is preventable, and hospitals can decrease VAP rates. This study aims to retrospectively assess VAP rates in the intensive care unit of Dr. Abdurrahman Yurtaslan Ankara Oncology Training and Research Hospital of the University of Health Sciences, with reference to Acinetobacter baumannii, one of the causative organisms.

Methods:

This study enrolled a total of 2277 patients hospitalized between the years of 2011 and 2015. The required data were collected by reviewing medical files of the patients through computerized hospital databases. VAP rate and ventilator utilization (VU) ratio were calculated using the United States Center for Disease Control National Healthcare Safety Network methodology.

Results:

Of the study patients, 302 (13.26%) were seen to have developed VAP. Among these patients, 191 (63.25%) were microbiologically diagnosed VAP caused by A. baumannii. Pooled means of VU ratio and VAP rate were 0.70 and 22.91, respectively.

Conclusion:

The results of this study will motivate the infection control committee of the study hospital to assess current infection control program and strategies so that high VAP rate in the study intensive care unit can be reduced to the minimum possible level.

Ventilator-associated pneumonia in adults: a narrative review

Ventilator-associated pneumonia (VAP) is one of the most frequent ICU-acquired infections. Reported incidences vary widely from 5 to 40% depending on the setting and diagnostic criteria. VAP is associated with prolonged duration of mechanical ventilation and ICU stay. The estimated attributable mortality of VAP is around 10%, with higher mortality rates in surgical ICU patients and in patients with mid-range severity scores at admission. Microbiological confirmation of infection is strongly encouraged. Which sampling method to use is still a matter of controversy. Emerging microbiological tools will likely modify our routine approach to diagnosing and treating VAP in the next future. Prevention of VAP is based on minimizing the exposure to mechanical ventilation and encouraging early liberation. Bundles that combine multiple prevention strategies may improve outcomes, but large randomized trials are needed to confirm this. Treatment should be limited to 7 days in the vast majority of the cases. Patients should be reassessed daily to confirm ongoing suspicion of disease, antibiotics should be narrowed as soon as antibiotic susceptibility results are available, and clinicians should consider stopping antibiotics if cultures are negative.

Incidence and costs of ventilator-associated pneumonia in the adult intensive care unit of a tertiary referral hospital in Mexico

BACKGROUND

Ventilator-associated pneumonia (VAP) is defined as pneumonia that occurs after 48 hours of endotracheal intubation and initiation of mechanical ventilation. The aim of this work was to use a micro-costing method to calculate the costs generated in 2017 for the care of patients with VAP at the Hospital Juárez de México.

METHODS

We performed a cross-sectional, retrospective, analytical, and observational study of the databases of the registry of health care-associated infections (HAIs) in 2017, in addition to a micro-costing study.

RESULTS

We studied 48 VAP cases in an adult intensive care unit (AICU). In this period, 1668 ventilator days were identified, with an incidence rate of 28.8 per 1000 days. All cases were caused by multidrug-resistant (MDR) bacteria and the costs of their care exceeded the average costs for the use of antimicrobials. By calculating the profit on return as an association measure, we found that VAP caused by MDR bacteria confers 9 times the risk of increasing the costs of care above the expected average.

CONCLUSIONS

The cost for a case of VAP in the AICU is high and has an impact on the institutional budget. Control measures to prevent the spread of bacteria, particularly MDR bacteria, must be put into place in order to avoid increases in hospital stay costs and mortality.

Emergence and molecular characterization of multidrug-resistant Klebsiella pneumoniae isolates harboring bla CTX-M-15 extended-spectrum β-lactamases causing ventilator-associated pneumonia in China

Background

Ventilator-associated pneumonia (VAP) is a common nosocomial infection associated with high morbidity due to multidrug-resistant (MDR) pathogens. The purpose of this study was to determine the occurrence of extended-spectrum β-lactamase (ESBL) genes, especially bla_CTX-M-15, in Klebsiella pneumoniae (K. pneumoniae)-associated VAP and to investigate the antimicrobial resistance patterns and molecular epidemiological characteristics of K. pneumoniae strains.

Materials and methods

From January 2013 to December 2015, we retrospectively collected 89 VAP-causing K. pneumoniae isolates from tertiary-care hospitals in China, among which ESBL-producing strains were assessed for antimicrobial susceptibility. Several antibiotic resistance genes of clinical relevance in K. pneumonia isolates producing ESBL were investigated. Polymerase chain reaction (PCR) and DNA sequencing were employed to characterize the genetic contexts of bla_CTX-M-15. Conjugative plasmids carrying bla_CTX-M-15 were obtained by mating and further subjected to replicon typing. The genetic relatedness of isolates was assessed by pulsed-field gel electrophoresis (PFGE) and multilocus sequence typing.

Results

All of the 30 ESBL-producing isolates identified displayed MDR phenotype, with bla_SHV, bla_CTX-M, bla_OXA, and bla_TEM detected in 21, 21, 1, and 20 isolates, respectively. bla_CTX-M-15 was the most prevalent ESBL gene (19/30, 63.33%), and ISEcp1 was detected 48 bp upstream of 15 bla_CTX-M-15 genes. Based on S1-PFGE analyses, 25 isolates exhibited different plasmid profiles, ranging from ~70 to 320 kb. The bla_CTX-M-15 with bla_TEM and qnr genes and the ISEcp1 element from eight isolates were co-transferrable to recipients via conjugation, with IncFIB, IncFIC, and IncFII being the most prevalent replicons. Twenty different PFGE patterns and 11 sequence types were identified, with ST304 being dominant.

Conclusion

This work reports the emergence of bla_CTX-M-15 in K. pneumoniae-induced VAP in China. We showed that IncFIB, IncFIC, and/or IncFII plasmids carrying bla_CTX-M-15 with bla_TEM, qnr resistance genes, and the ISEcp1 element mediate the local prevalence in K. pneumoniae-associated VAP.

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.