Endotracheal tube biofilm translocation in the lateral Trendelenburg position

The efficacy of telavancin in comparison with linezolid on endotracheal tube biofilm in pigs with methicillin-resistant Staphylococcus aureus pneumonia

BACKGROUND

The effect of systemic treatment of ventilator-associated pneumonia (VAP) with telavancin, a semisynthetic lipoglycopeptide with good penetration in vitro biofilms, has not been tested in vivo during mechanical ventilation. This study examined the efficacy of telavancin compared with linezolid against endotracheal tube (ETT) biofilms in a porcine model of methicillin-resistant Staphylococcus aureus (MRSA) VAP.

METHODS

VAP was induced in 18 pigs by instilling 107 colony-forming units (CFU/mL) of an MRSA strain susceptible to telavancin and linezolid into each pulmonary lobe. Randomization into three groups was done at pneumonia diagnosis: control (IV glucose 0.5% solution q24); linezolid (10 mg/kg q12) and telavancin groups (22.5 mg/kg q24). After 72 h of MV, data regarding bronchoalveolar lavage (BAL), tracheal aspirate (TA), ETT MRSA biofilm load and thickness measured by scanning electron microscopy were obtained.

RESULTS

All 18 pigs completed the study. MRSA was isolated in 100% of ETTs from the control and linezolid groups and in 67% from the telavancin group. Telavancin treatment presented a lower MRSA load compared to the control and linezolid treatments (telavancin median [interquartile range (IQR)] = 1.94 [0.00-5.45], linezolid 3.99 [3.22-4.68] and control 4.93 [4.41-5.15], P = 0.236). Telavancin treatment also resulted in the lowest biofilm thickness according to the SEM (4.04 [2.09-6.00], P < 0.001). We found a positive correlation between ETT and BAL load (rho = 0.511, P = 0.045).

CONCLUSIONS

In our VAP model, systemic telavancin treatment reduced ETT MRSA occurrence, load, and biofilm thickness. Our findings may have a bearing on ICU patients' clinical outcomes.

Endotracheal tube biofilm in critically ill patients during the COVID-19 pandemic : description of an underestimated microbiological compartment

Biofilm (BF) growth is believed to play a major role in the development of ventilator-associated pneumonia (VAP) in the intensive care unit. Despite concerted efforts to understand the potential implication of endotracheal tube (ETT)-BF dispersal, clinically relevant data are lacking to better characterize the impact of its mesostructure and microbiological singularity on the occurrence of VAP. We conducted a multicenter, retrospective observational study during the third wave of the COVID-19 pandemic, between March and May 2021. In total, 64 ETTs collected from 61 patients were included in the present BIOPAVIR study. Confocal microscopy acquisitions revealed two main morphological aspects of ETT-deposited BF: (1) a thin, continuous ribbon-shaped aspect, less likely monobacterial and predominantly associated with Enterobacter spp., Streptococcus pneumoniae or Viridans streptococci, and (2) a thicker, discontinuous, mushroom-shaped appearance, more likely characterized by the association of bacterial and fungal species in respiratory samples. The microbiological characterization of ETT-deposited BF found higher acquired resistance in more than 80% of analyzed BF phenotypes, compared to other colonization sites from the patient's environment. These findings reveal BF as a singular microbiological compartment, and are of added clinical value, with a view to future ETT-deposited BF-based antimicrobial stewardship in critically ill patients. Trial registration NCT04926493. Retrospectively registered 15 June 2021.

Endo-bronchial aerosolized AAV1.SERCA2a gene therapy in a pulmonary hypertension pig model: addressing the lung delivery bottleneck

A disappointing number of new therapies for pulmonary hypertension (PH) have been successfully translated to the clinic. Adeno-associated viral (AAV) gene therapy has the potential to treat the underlying pathology of PH, but the challenge remains in efficient and safe delivery. The aims of this study were i) to test the efficacy of endo-bronchial aerosolization delivery for AAV1-mediated sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (SERCA2a) gene therapy in a PH pig model and ii) to identify the most efficient airway administration modality for in-lung gene therapy in PH. We hypothesized that delivery to the distal bronchi increases lung viral uptake and avoids virus loss in off-target compartments. In part one of the study, PH was induced in pigs by surgically banding the pulmonary veins. Two months post-surgery, 1x1013 viral genomes (vg) of AAV1.SERCA2a or saline was endo-bronchially aerosolized using a bronchoscope. Two months after aerosolization, high vg copies were detected in the lungs, accompanied by functional and morphometrical amelioration of PH. In part two of the study, we directly compared the endo-bronchial aerosolization gene delivery to the intra-tracheal aerosolization in PH pigs. Endo-bronchial delivery demonstrated higher viral expression (6,719 ± 927 vs 1,444 ± 402 vg copy/100ng DNA, p=0.0017), suggesting this delivery modality is a promising method for clinical AAV gene therapy for PH.

Endobronchial Gene Delivery for Pulmonary Hypertension in a Large Animal Model

Pulmonary hypertension (PH) is a devastating disease with high morbidity and mortality. Despite significant progress in the pharmacotherapy, current treatments only ameliorate the symptoms and cannot heal PH. Gene therapy may target the roots of the disease and holds evident promise. The current bottleneck for lung gene therapy is the delivery method. The requirements for the delivery mode are efficiency, safety, and the ability to target the anatomical site of interest, while avoiding off-target effects. Aerosolized gene delivery has been used in several studies and proven to be an efficient mode of administration for lung gene therapy. In this chapter, we describe a protocol of endobronchial aerosolization for PH gene therapy in a large animal model. Testing of a gene therapy in large animals is essential before clinical testing, since the lung anatomy and (patho)physiology differ immensely between humans and rodents, where most of the proof-of-concept studies are tested. The gene delivery vector is being aerosolized in the peripheral bronchi using a sprayer inserted through a flexible bronchoscope. This delivery mode results in efficient lung uptake and less off-target distribution relative to other airway delivery methods.

Bacteriophage Cocktail-Mediated Inhibition of Pseudomonas aeruginosa Biofilm on Endotracheal Tube Surface

Although different strategies to control biofilm formation on endotracheal tubes have been proposed, there are scarce scientific data on applying phages for both removing and preventing Pseudomonas aeruginosa biofilms on the device surface. Here, the anti-biofilm capacity of five bacteriophages was evaluated by a high content screening assay. We observed that biofilms were significantly reduced after phage treatment, especially in multidrug-resistant strains. Considering the anti-biofilm screens, two phages were selected as cocktail components, and the cocktail's ability to prevent colonization of the endotracheal tube surface was tested in a dynamic biofilm model. Phage-coated tubes were challenged with different P. aeruginosa strains. The biofilm growth was monitored from 24 to 168 h by colony forming unit counting, metabolic activity assessment, and biofilm morphology observation. The phage cocktail promoted differences of bacterial colonization; nonetheless, the action was strain dependent. Phage cocktail coating did not promote substantial changes in metabolic activity. Scanning electron microscopy revealed a higher concentration of biofilm cells in control, while tower-like structures could be observed on phage cocktail-coated tubes. These results demonstrate that with the development of new coating strategies, phage therapy has potential in controlling the endotracheal tube-associated biofilm.

Selective digestive decontamination solution used as "lock therapy" prevents and eradicates bacterial biofilm in an in vitro bench-top model

Background

Most preventing measures for reducing ventilator-associated pneumonia (VAP) are based mainly on the decolonization of the internal surface of the endotracheal tubes (ETTs). However, it has been demonstrated that bacterial biofilm can also be formed on the external surface of ETTs. Our objective was to test in vitro the efficacy of selective digestive decontamination solution (SDDs) onto ETT to prevent biofilm formation and eradicate preformed biofilms of three different microorganisms of VAP.

Methods

We used an in vitro model in which we applied, at the subglottic space of ETT, biofilms of either P. aeruginosa ATCC 15442, or E. coli ATCC 25922, or S. aureus ATCC 29213, and the SDDs at the same time (prophylaxis) or after 72 h of biofilm forming (treatment). ETT were incubated during 5 days with a regimen of 2 h-locks. ETT fragments were analyzed by sonication and confocal laser scanning microscopy to calculate the percentage reduction of cfu and viable cells, respectively.

Results

Median (IQR) percentage reduction of live cells and cfu/ml counts after treatment were, respectively, 53.2% (39.4%—64.1%) and 100% (100%–100.0%) for P. aeruginosa, and 67.9% (46.7%–78.7%) and 100% (100%–100.0%) for E. coli. S. aureus presented a complete eradication by both methods. After prophylaxis, there were absence of live cells and cfu/ml counts for all microorganisms.

Conclusions

SDDs used as “lock therapy” in the subglottic space is a promising prophylactic approach that could be used in combination with the oro-digestive decontamination procedure in the prevention of VAP.

Hippocampal Damage During Mechanical Ventilation in Trendelenburg Position: A Secondary Analysis of an Experimental Study on the Prevention of Ventilator-Associated Pneumonia

We previously corroborated benefits of the Trendelenburg position in the prevention of ventilator-associated pneumonia (VAP). We now investigate its potential effects on the brain versus the semirecumbent position. We studied 17 anesthetized pigs and randomized to be ventilated and positioned as follows: duty cycle (TI/TTOT) of 0.33, without positive end-expiratory pressure (PEEP), placed with the bed oriented 30° in anti-Trendelenburg (control group); positioned as in the control group, with TI/TTOT adjusted to achieve an expiratory flow bias, PEEP of 5 cm H2O (IRV-PEEP); positioned in 5° TP and ventilated as in the control group (TP). Animals were challenged into the oropharynx with Pseudomonas aeruginosa. We assessed hemodynamic parameters and systemic inflammation throughout the study. After 72 h, we evaluated incidence of microbiological/histological VAP and brain injury. Petechial hemorrhages score was greater in the TP group (P = 0.013). Analysis of the dentate gyrus showed higher cell apoptosis and deteriorating neurons in TP animals (P < 0.05 vs. the other groups). No differences in systemic inflammation were found among groups. Cerebral perfusion pressure was higher in TP animals (P < 0.001), mainly driven by higher mean arterial pressure. Microbiological/histological VAP developed in 0%, 67%, and 86% of the animals in the TP, control, and IRV-PEEP groups, respectively (P = 0.003). In conclusion, the TP prevents VAP; yet, we found deleterious neural effects in the dentate gyrus, likely associated with cerebrovascular modification in such position. Further laboratory and clinical studies are mandatory to appraise potential neurological risks associated with long-term TP.

Implications of the presence of yeasts in tracheobronchial secretions of critically ill intubated patients

The presence of some microorganisms in the respiratory tract is a known risk factor for the infection of air passages; however, it is not clear whether this holds true for Candida spp. Thus, our objective was to determine the frequency of yeast colonization in the tracheobronchial secretions of critically ill intubated patients and to assess the presence of these yeasts in the infra-cuff region of the endotracheal tube (ET). Patients aged 18 years or older who had been using an endotracheal tube for 48 hours were recruited. Tracheal secretions were collected; after extubation, the ETs were cut into two fragments in the infra-cuff region. One of these fragments was placed in a solution containing antibiotics and sent to the lab for culture and identification of yeasts. The remaining fragment was fixed and subjected to scanning electron microscopy (SEM). In total, 20 patients with an average age of 73.3 years (± 13.1) participated in this study. These patients remained under endotracheal intubation and invasive mechanical ventilation for an average of 6.4 (± 1.8) and 13.5 days (± 15), respectively. Of these patients, 45 % showed respiratory tract colonization by yeasts of the Candida genus, with C. albicans being the most frequently isolated species (66.7 %). Moreover, in almost 90 % of these patients, blastoconidia of the same yeast were found in the infra-cuff portion of the ET, as evidenced by SEM, strongly fixed on the ET surface. Yeasts isolated from both the infra-cuff region and the tracheobronchial secretions were susceptible to amphotericin B and fluconazole. In conclusion, our results show that the frequency of colonization by yeasts of the Candida genus in the tracheobronchial secretions of intubated patients within 48 hours is high, and that these species can also be found as a biofilm on the ET surface.

Prevention of Lung Bacterial Colonization With a Leak-Proof Endotracheal Tube Cuff: An Experimental Animal Study

BACKGROUND

Endotracheal tubes with standard polyvinyl chloride cuffs create folds on inflation into the trachea, which lead to potential leakage of subglottic secretions into the lower airways and cause lung colonization and pneumonia. The use of a double-layer prototype leak-proof cuff has shown effective prevention of the fluid leakage across the cuff. We hypothesized that the use of such a leak-proof cuff could prevent lung bacterial colonization in vivo.

METHODS

To simulate patients in the ICU, 13 pigs were placed in the semirecumbent position, intubated, and mechanically ventilated for 72 h. Five animals were prospectively intubated with an endotracheal tube with a leak-proof cuff (leak-proof cuff group). Data from 8 animals previously intubated with an endotracheal tube with a standard polyvinyl chloride cuff (standard cuff group) were retrospectively analyzed. Leakage of tracheal secretions across the leak-proof cuff was tested by the macroscopic methylene blue evaluation. Arterial blood gas exchanges and microbiology were tested in all the pigs at necropsy.

RESULTS

In the standard cuff group, all the pigs showed heavy bacterial colonization of the lungs after 72 h of mechanical ventilation, with an overall proportion of colonized lung lobes of 92% (44/48 lobes, 8/8 animals) compared with 27% (8/30 lobes, 5/5 animals) in the leak-proof cuff group (P < .001). These results were strengthened by the absence of methylene blue in the tracheal secretions below the leak-proof cuff. Furthermore, no hypoxemia was demonstrated in the pigs in the leak-proof cuff group after the 72-h experiment (P_aO2 /F_IO2 change from baseline, leak-proof cuff group vs standard cuff group; median difference 332, 95% CI 41-389 mm Hg; P = .030).

CONCLUSIONS

A new leak-proof cuff for endotracheal intubation prevented macroscopic leakage of subglottic secretions along the airways. This mechanism led to the reduction of lung bacterial colonization, which could contribute to the prevention of hypoxemia in the pigs on mechanical ventilation while in the semirecumbent position.

Pulmonary Function Diagnosis Based on Respiratory Changes in Lung Density With Dynamic Flat-Panel Detector Imaging: An Animal-Based Study

OBJECTIVES

The aims of this study were to address the relationship between respiratory changes in image density of the lungs and tidal volume, to compare the changes between affected and unaffected lobes, and to apply this new technique to the diagnosis of atelectasis.

MATERIALS AND METHODS

Our animal care committee approved this prospective animal study. Sequential chest radiographs of 4 pigs were obtained under respiratory control with a ventilator using a dynamic flat-panel detector system. Porcine models of atelectasis were developed, and the correlation between the tidal volume and changes in pixel values measured in the lungs were analyzed. The mean difference in respiratory changes in pixel values between both lungs was tested using paired t tests. To facilitate visual evaluation, respiratory changes in pixel values were visualized in the form of a color display, that is, as changes in color scale.

RESULTS

Average pixel values in the lung regions changed according to forced respiration. High linearity was observed between changes in pixel values and tidal volume in the normal models (r = 0.99). Areas of atelectasis displayed significantly reduced changes in pixel values (P < 0.05). Of all atelectasis models with air trapping and air inflow restriction, 92.7% (19/20) were visualized as color-defective or color-marked areas on functional images, respectively.

CONCLUSION

Dynamic chest radiography allows for the relative evaluation of tidal volume, the detection of ventilation defects in the lobe unit, and a differential diagnosis between air trapping and air inflow restriction, based on respiratory changes in image density of the lungs, even without the use of contrast media.

Treatment of Pseudomonas aeruginosa Biofilm Present in Endotracheal Tubes by Poly-l-Lysine

The endotracheal tube (ETT) is an essential interface between the patient and ventilator in mechanically ventilated patients. However, a microbial biofilm is formed gradually on this tube and is associated with the development of ventilator-associated pneumonia. The bacteria present in the biofilm are more resistant to antibiotics, and current medical practices do not make it possible to eliminate. Pseudomonas aeruginosa is one of the leading pathogens that cause biofilm infections and ventilator-associated pneumonia. Poly-l-lysine (pLK) is a cationic polypeptide possessing antibacterial properties and mucolytic activity by compacting DNA. Here, we explored the antibiofilm activity of pLK to treat P. aeruginosa biofilms on ETTs while taking into consideration the necessary constraints for clinical translation in our experimental designs. First, we showed that pLK eradicates a P. aeruginosa biofilm formed in vitro on 96-well microplates. We further demonstrated that pLK alters bacterial membrane integrity, as revealed by scanning electron microscopy, and eventually eradicates biofilm formed either by reference or clinical strains of P. aeruginosa biofilms generated in vitro on ETTs. Second, we collected the ETT from patients with P. aeruginosa ventilator-associated pneumonia. We observed that a single dose of pLK is able to immediately disrupt the biofilm structure and kills more than 90% of bacteria present in the biofilm. Additionally, we did not observe any lung tolerance issue when the pLK solution was instilled into the ETT of ventilated pigs, an animal model particularly relevant to mimic invasive mechanical ventilation in humans. In conclusion, pLK appears as an innovative antibiofilm molecule, which could be applied in the ETT of mechanically ventilated patients.

Assessment of in vivo versus in vitro biofilm formation of clinical methicillin-resistant Staphylococcus aureus isolates from endotracheal tubes

Our aim was to demonstrate that biofilm formation in a clinical strain of methicillin-resistant Staphylococcus aureus (MRSA) can be enhanced by environment exposure in an endotracheal tube (ETT) and to determine how it is affected by systemic treatment and atmospheric conditions. Second, we aimed to assess biofilm production dynamics after extubation. We prospectively analyzed 70 ETT samples obtained from pigs randomized to be untreated (controls, n = 20), or treated with vancomycin (n = 32) or linezolid (n = 18). A clinical MRSA strain (MRSA-in) was inoculated in pigs to create a pneumonia model, before treating with antibiotics. Tracheally intubated pigs with MRSA severe pneumonia, were mechanically ventilated for 69 ± 16 hours. All MRSA isolates retrieved from ETTs (ETT-MRSA) were tested for their in vitro biofilm production by microtiter plate assay. In vitro biofilm production of MRSA isolates was sequentially studied over the next 8 days post-extubation to assess biofilm capability dynamics over time. All experiments were performed under ambient air (O₂) or ambient air supplemented with 5% CO₂. We collected 52 ETT-MRSA isolates (placebo N = 19, linezolid N = 11, and vancomycin N = 22) that were clonally identical to the MRSA-in. Among the ETT-MRSA isolates, biofilm production more than doubled after extubation in 40% and 50% under 5% CO₂ and O₂, respectively. Systemic antibiotic treatment during intubation did not affect this outcome. Under both atmospheric conditions, biofilm production for MRSA-in was at least doubled for 9 ETT-MRSA isolates, and assessment of these showed that biofilm production decreased progressively over a 4-day period after extubation. In conclusion, a weak biofilm producer MRSA strain significantly enhances its biofilm production within an ETT, but it is influenced by the ETT environment rather than by the systemic treatment used during intubation or by the atmospheric conditions used for bacterial growth.

Does animal model on ventilator-associated pneumonia reflect physiopathology of sepsis mechanisms in humans?

Ventilator-associated pneumonia (VAP) is the leading cause of death in critically ill patients in intensive care units. In the last 20 years, different animal models have been a valuable tool for the study of pathophysiology and phenotypic characteristics of different lung infections observed in humans, becoming an essential link between ''in vitro'' testing and clinical studies. Different animal models have been used to study the mechanism of a deregulated inflammatory response and host tissue damage of sepsis in VAP, as well as different infection parameters such as clinical, physiological, microbiological and pathological facts in several large and small mammals. In addition, the dosage of inflammatory modulators and their consequences in local and systemic inflammation, or even the administration of antibiotics, have been evaluated with very interesting results. Although some bronchial inoculation ways do not resemble the common pathophysiologic mechanisms, the experimental model of VAP induced by the inoculation of high concentrations of pathogens in mechanically ventilated animals is useful for studying the local and systemic responses of sepsis in VAP and it reproduces biological mechanisms such as acute lung injury, distress response, cardiac events and immune modulation comparable with clinical studies.

Diagnostic Value of Endotracheal Aspirates Sonication on Ventilator-Associated Pneumonia Microbiologic Diagnosis

Microorganisms are able to form biofilms within respiratory secretions. Methods to disaggregate such biofilms before utilizing standard, rapid, or high throughput diagnostic technologies may aid in pathogen detection during ventilator associated pneumonia (VAP) diagnosis. Our aim was to determine if sonication of endotracheal aspirates (ETA) would increase the sensitivity of qualitative, semi-quantitative, and quantitative bacterial cultures in an animal model of pneumonia caused by Pseudomonas aeruginosa or by methicillin resistant Staphylococcus aureus (MRSA). Material and methods: P. aeruginosa or MRSA was instilled into the lungs or the oropharynx of pigs in order to induce severe VAP. Time point assessments for qualitative and quantitative bacterial cultures of ETA and bronchoalveolar lavage (BAL) samples were performed at 24, 48, and 72 h after bacterial instillation. In addition, at 72 h (autopsy), lung tissue was harvested to perform quantitative bacterial cultures. Each ETA sample was microbiologically processed with and without applying sonication for 5 min at 40 KHz before bacterial cultures. Sensitivity and specificity were determined using BAL as a gold-standard. Correlation with BAL and lung bacterial burden was also determined before and after sonication. Assessment of biofilm clusters and planktonic bacteria was performed through both optical microscopy utilizing Gram staining and Confocal Laser Scanning Microscopy utilizing the LIVE/DEAD^®BacLight kit. Results: 33 pigs were included, 27 and 6 from P. aeruginosa and MRSA pneumonia models, respectively. Overall, we obtained 85 ETA, 69 (81.2%) from P. aeruginosa and 16 (18.8%) from MRSA challenged pigs. Qualitative cultures did not significantly change after sonication, whereas quantitative ETA cultures did significantly increase bacterial counting. Indeed, sonication consistently increased bacterial burden in ETAs at 24, 48, and 72 h after bacterial challenge. Sonication also improved sensitivity of ETA quantitative cultures and maintained specificity at levels previously reported and accepted for VAP diagnosis. Conclusion: The use of sonication in ETA respiratory samples needs to be clinically validated since sonication could potentially improve pathogen detection before standard, rapid, or high throughput diagnostic methods used in routine microbial diagnostics.

Pediatric Ventilator-Associated Infections: The Ventilator-Associated INfection Study

OBJECTIVE

Suspected ventilator-associated infection is the most common reason for antibiotics in the PICU. We sought to characterize the clinical variables associated with continuing antibiotics after initial evaluation for suspected ventilator-associated infection and to determine whether clinical variables or antibiotic treatment influenced outcomes.

DESIGN

Prospective, observational cohort study conducted in 47 PICUs in the United States, Canada, and Australia. Two hundred twenty-nine pediatric patients ventilated more than 48 hours undergoing respiratory secretion cultures were enrolled as "suspected ventilator-associated infection" in a prospective cohort study, those receiving antibiotics of less than or equal to 3 days were categorized as "evaluation only," and greater than 3 days as "treated." Demographics, diagnoses, comorbidities, culture results, and clinical data were compared between evaluation only and treated subjects and between subjects with positive versus negative cultures.

SETTING

PICUs in 47 hospitals in the United States, Canada, and Australia.

SUBJECTS

All patients undergoing respiratory secretion cultures during the 6 study periods.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Treated subjects differed from evaluation-only subjects only in frequency of positive cultures (79% vs 36%; p < 0.0001). Subjects with positive cultures were more likely to have chronic lung disease, tracheostomy, and shorter PICU stay, but there were no differences in ventilator days or mortality. Outcomes were similar in subjects with positive or negative cultures irrespective of antibiotic treatment. Immunocompromise and higher Pediatric Logistic Organ Dysfunction scores were the only variables associated with mortality in the overall population, but treated subjects with endotracheal tubes had significantly lower mortality.

CONCLUSIONS

Positive respiratory cultures were the primary determinant of continued antibiotic treatment in children with suspected ventilator-associated infection. Positive cultures were not associated with worse outcomes irrespective of antibiotic treatment although the lower mortality in treated subjects with endotracheal tubes is notable. The necessity of continuing antibiotics for a positive respiratory culture in suspected ventilator-associated infection requires further study.

Biofilms in ventilator-associated pneumonia

Biofilms develop rapidly following endotracheal intubation and represent a persistent source of unnecessary pathogens in the critically ill patient. Overall, the imbalance in the lung microbiome caused by an endotracheal tube and its role in biofilm formation and in ventilator-associated pneumonia is still unclear. Although endotracheal tube–biofilm preventive measures are being tested, no outcome impact has ever been demonstrated, and therefore no approach has been clinically recommended. Nonetheless, an accurate description of the actual biofilm morphology in vivo could be useful to implement effective preventive measures. The combined use of in vitro biofilm models, in vivo animal models and clinical research is vitally important to the attainment of a comprehensive understanding of biofilms in ventilator-associated pneumonia in the near future.