Pseudomonas aeruginosa displays an altered phenotype in vitro when grown in the presence of mannitol

Administration of dry powders during respiratory supports

Inhaled drugs are routinely used for the treatment of respiratory-supported patients. To date, pressurized metered dose inhalers and nebulizers are the two platforms routinely employed in the clinical setting. The scarce utilization of the dry powder inhaler (DPI) platform is partly due to the lack of in vivo data that proves optimal delivery and drug efficacy are achievable. Additionally, fitting a DPI in-line to the respiratory circuit is not as straightforward as with the other aerosol delivery platforms. Importantly, there is a common misconception that the warm and humidified inspiratory air in respiratory supports, even for a short exposure, will deteriorate powder formulation compromising its delivery and efficacy. However, some recent studies have dispelled this myth, showing successful delivery of dry powders through the humidified circuit of respiratory supports. Compared with other aerosol delivery devices, the use of DPIs during respiratory supports possesses unique advantages such as rapid delivery and high dose. In this review, we presented in vitro studies showing various setups employing commercial DPIs and effects of ventilator parameters on the aerosol delivery. Inclusion of novel DPIs was also made to illustrate characteristics of an ideal inhaler that would give high lung dose with low powder deposition loss in tracheal tubes and respiratory circuits. Clinical trials are urgently needed to confirm the benefits of administration of dry powders in ventilated patients, thus enabling translation of powder delivery into practice.

Does ivacaftor interfere with the antimicrobial activity of commonly used antibiotics against Pseudomonas aeruginosa?-Results of an in vitro study

WHAT IS KNOWN AND OBJECTIVE

Ivacaftor is a novel potentiator of defective cystic fibrosis transmembrane conductance regulator (CFTR) protein, which corrects the gating defect and increases ion-function of activated cell-surface CFTR. Bacteria also regulate their physiology through ion channels. However, little is known about the potential effects of ivacaftor on bacterial ion channels, which, in turn, may have a potential effect on transport across the bacterial cell membrane. Therefore, any change in the ability to transport molecules across cell membranes in bacteria could have an important impact on bacterial transport physiology. One area where this could be particularly important is in the movement of antibiotics, both into and out of the bacterial cell. An in vitro study was therefore performed to examine the influence of ivacaftor at therapeutic concentration on antibiotic susceptibility of 11 commonly used anti-pseudomonal antibiotics against a population of clinical Pseudomonas aeruginosa [PA], from CF and non-CF sources.

METHOD

Pseudomonas aeruginosa (n = 80; including 70 ivacaftor-naïve clinical PA from sputa from adult CF patients and 10 control PA from non-CF clinical blood culture sources) were examined. Antibiotic susceptibility was determined by standard disc diffusion assay using CLSI criteria and measuring zone size (mm), against four classes of anti-pseudomonal antibiotics, including beta-lactams (temocillin, ceftazidime, piperacillin/tazobactam, imipenem, meropenem and aztreonam), aminoglycosides (gentamicin, tobramycin, amikacin), fluoroquinolone (ciprofloxacin) and polymyxin (colistin), in the absence and presence of ivacaftor (5 μmol/L), as previously determined. In addition, all CF and non-CF PA were examined phenotypically in vitro, as previously described, for changes linked to bacterial virulence, including (i) growth density (ii) pigmentation, (iii) presence of adhesins and (iv) change to mucoidy, in the presence/absence of ivacaftor at therapeutic concentration.

RESULTS AND DISCUSSION

Antibiotic susceptibility did not decrease significantly with any of the antibiotics examined with CF PA isolates or with non-CF PA control organisms. There was a statistically significant increase in zone size (CF PA and amikacin, gentamicin, temocillin and ciprofloxacin; Non-CF PA and amikacin, gentamicin and aztreonam). However, at a population level, this did not translate into a shift in CLSI category to a more susceptible phenotype. None of the PA isolates examined were susceptible to ivacaftor alone, and additionally, no changes were noted with the four phenotypic parameters examined in the presence of ivacaftor.

WHAT IS NEW AND CONCLUSION

This study showed that antibiotic susceptibility of commonly used anti-pseudomonal antibiotics was not negatively affected by ivacaftor, in a population of ivacaftor-naive P. aeruginosa.

A Novel In-Line Delivery System to Administer Dry Powder Mannitol to Mechanically Ventilated Patients

BACKGROUND

Mechanically ventilated patients commonly suffer from ventilator-associated pneumonia, hypoxemia, and other lower respiratory tract infection as a result of pathogen colonization and poor sputum clearance. Consequently, there is a high rate of morbidity and mortality in these patients. Dry powder mannitol increases sputum clearance, and therefore, we developed a system to administer it to mechanically ventilated patients without disconnection from the ventilator.

METHODS

The inspiratory line from a ventilator was split by using a three-way valve into two parallel lines where one contains a humidifier for normal breathing cycle and the other line contains a dry powder inhaler (Osmohaler™). The inspiratory air went through the dry powder line and aerosolized the mannitol powder only when its administration to a patient is required. We determined the delivered dose and particle size distributions of emitted aerosols in vitro from 9.5 mm endotracheal and 7.5 mm tracheostomy tubes, with inspiratory airflow of 60, 70, and 80 L/min.

RESULTS

This novel setup was able to deliver 24.6% ± 3.33% of the 160 mg loaded dose mannitol powder (4 × 40 mg capsules) and 26.7% ± 2.19% of the 320 mg dose (4 × 80 mg capsules) when the endotracheal tube was used. With the shorter tracheostomy tube, the delivery dose increased to 35.6% ± 3.01% and 39.5% ± 2.04% of the 160 and 320 mg doses, respectively. The volume median diameters of the aerosols were in the respirable range with the largest value being 5.17 ± 0.87 μm.

CONCLUSIONS

This delivery system has been shown to consistently deliver a high respirable dose of mannitol powder. Since this setup does not require disconnection of patients from the ventilator, it is safer for hypoxemic patients and easier to be adapted in a real clinical use.