VAP Physiology

Ventilator-Associated Pneumonia (VAP) is associated with increased intensive care unit (ICU) stay and mortality with an estimation of increasing the mortality of the underlying disease by ∼30%. The primary route for acquiring endemic VAP is oropharyngeal colonization by the endogenous flora or by pathogens acquired externally from the intensive care unit environment. When patients are kept on tubular mechanical systems, bacteria travel in small droplets both through the endotracheal tube and around the cuff. Often, bacteria colonize the endotracheal or tracheostomy tube and are embolized into the lungs with each breath. Bacteria may also be brought down into the lungs with procedures such as deep suctioning or bronchoscopy, the mucus lining the bronchial tree etc. Ciliary action of the cells lining the trachea drives the mucus superiorly, leading to a build-up of fluids around the inflated cuff where there is little to no airway clearance. The bacteria then colonize readily, reach the alveoli and fill up the sacs with liquids which causes pus and breathing issues. The late-onset VAP is caused by methicillin-resistant S. aureus (MRSA), P.aeruginosa, Acinetobacter baumannii (drug-resistant group) which causes increased morbidity and mortality.

Treatment Strategy

Current Method

The only method to deal with the acquired infections is by administering antibiotics to control the spread of infections. Once the condition is diagnosed, and we have results for the infection microbial profiles, corresponding antibiotics are delivered to the sites of diseases, i.e. alveoli and trachea lining. Usually, most of the infections are polymicrobial and broad-spectrum antibiotics or combinations of antibiotics are given to control the infection. The major pressure of antibiotic resistance comes from this stage where patients are prescribed general antibiotics in ludicrous amounts, leading to quick resistance generation.

Pulmonary Surfactant

Pulmonary surfactant is a surface-active lipoprotein complex formed by type II alveolar cells. It is present at the air/liquid interface to reduce the surface tension within the alveoli. Surfactant is enriched with a relatively unique phospholipid, termed dipalmitoylphosphatidylcholine, and four surfactant-associated proteins, SP-A, SP-B, SP-C, and SP-D. The hydrophobic proteins, SP-B and SP-C, together with dipalmitoylphosphatidylcholine, confer surface tension–lowering properties to the material. The more hydrophilic surfactant components, SP-A and SP-D bind and partake in the clearance of a variety of bacterial, fungal, and viral pathogens and can dampen antigen-induced immune function of effector cells. Also, microbial pathogens in preclinical models impair surfactant synthesis and secretion, and microbial proteases degrade surfactant-associated proteins.

Our Formulation

We propose a surfactant-based formulation containing a cocktail of fusion proteins that shall be used as an endotracheal and endobronchial administration. Surfactant therapy is given to preterm babies/neonates for treatment of respiratory distress syndrome. We intend to use a surfactant to optimize the drug delivery and obtain a more homogeneous distribution of the drug by using rapid bolus installation in combination with appropriate alveolar recruitment techniques. This will involve the administration of the formulation carefully designed according to the microbial diagnosis of each infection. We intend to keep our therapy specific and targeted by providing a unique seekercin for different species, thereby avoiding any collateral damage and reducing the scope of resistance development.

In order to determine precise concentration requirements and dosage, we require data which will be available after the characterisation and efficacy studies of our fusion protein. Surfactant is composed of ∼80–85% phospholipids, 5–10% neutral lipids and 8–10% protein, with 5–6% consisting of the four specific surfactant proteins. Broadly, the formulation has the following composition:

The aqueous liquid containing soluble drugs can be delivered into targeted branches of the lung airway and deposited onto the lung epithelium by instilling a specific microvolume of liquid into the upper airways and moving the plug by programmed air ventilation into a desired area of the lung.

Design Process

Initially, we had researched and decided on delivery of pyocins through nebulizers to intubated/ventilated patients. This becomes clinically relevant in all hospitals; however, in India there is a disproportionately large problem with VAPs in the Newborn Intensive Care Units. (NICU) (60k+ deaths per year). On seeking an expert opinion from a Doctor (NICU/VAP specialist) on our devised strategy, he pointed out that neonates, especially preterm, have underdeveloped lungs that are too delicate for effective nebulizer based treatment. A significant disadvantage of nebulizer therapy is its low delivery efficiency, the majority of the dose is lost in the ETT(deposition of mist on the walls, drug doesn't get misted well, etc.). When delivering by bolus dose, drug loss is no longer an issue, as the liquid itself is injected into the lungs, carrying with it the drug.

Further, patient lungs are deficient in the production of surfactants, which lower the alveolar surface tension and allow breathing, leading to respiratory distress syndrome. Rapid and reliable delivery of bolus-injected surfactant solutions, which contain surfactant-associated proteins such as SP-A to the alveoli demonstrates a good precedent for Seekercin delivery. This method is also more likely to ensure the delivery of high doses (10^12 pyocins per ml) required for an effective treatment as found in in-vivo studies. The dose will reach the alveoli rapidly, and improvement is expected to be observed within seconds to minutes.

References

• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3059826/
• https://erj.ersjournals.com/content/17/5/1034
• http://rc.rcjournal.com/content/50/6/725.short
• https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4577144/
• https://pubmed.ncbi.nlm.nih.gov/3677746/
• https://pediatrics.medresearch.in/index.php/ijpr/article/view/483/959