Targeted dose delivery of Mycobacterium tuberculosis in mice using silicon antifoaming agent via aerosol exposure system

Abstract

Mycobacterium tuberculosis (Mtb) is an intracellular pathogen that forms aggregates (clumps) on solid agar plates and in liquid media. Detergents such as Tween 80/Tyloxapol are considered the gold standard to disrupt clump formation in Mtb cultures. The presence of detergent, however, may generate foam and hinder Mtb aerosolization thus requiring addition of an antifoam agent for optimal Mtb aerosol-based procedures. Aerosol inhalation can be technically challenging, in particular to achieve a reproducible inhaled target dose. In this study, the impact of an antifoam, the silicon antifoaming agent (SAF), on Mtb aerosolization and whole-body mouse aerosol infection was investigated. A comparative study using SAF in a liquid suspension containing Mycobacterium bovis BCG (M. bovis BCG) or Mtb H37Rv did not cause any adverse effect on bacterial viability. Incorporation of SAF during mycobacteria inhalation procedures revealed that aerosolized mycobacterial strains were maintained under controlled environmental conditions such as humidity, temperature, pressure, and airflow inside the aerosol chamber. In addition, environmental factors and spray factors were not affected by the presence of SAF in mycobacterial cultures during aerosolization. Spray factor was significantly less during aerosol procedures with a low-input dose of mycobacteria in comparison to high-dose, as predicted. The mycobacterial load recovered in the biosampler (AGI) was ~2–3 logs lower than nebulizer or input bacterial load. A consistent Mtb bacillary load determined in mouse lungs indicates that SAF does not affect mycobacteria aerosolization during the aerosol generation process. These data confirmed that 1) SAF prevents formation of excessive foam during aerosolization, 2) SAF had no negative impact on mycobacterial viability within aerosol droplets, 3) Mtb droplets within aerosol-generated particles are well within the range required for reaching and depositing deep into lung tissue, and 4) SAF had no negative impact on achieving a target dose in mice exposed to Mtb aerosol.

Novel Experimental Mouse Model to Study the Pathogenesis and Therapy of Actinobacillus pleuropneumoniae Infection

“…The number of APP in the liver and spleen was higher than other organs because bacterial clearance mainly occurred there [19]. The data are consistent with the infection of other lung bacteria, including M. tuberculosis [20,21], Burkholderia pseudomallei [22], M. abscessus [23], and Pseudomonas aeruginosa [24]. From a histological perspective, mice with an aerosol-mediated APP infection developed similar lung pathogenesis as those infected with APP via intranasal or intraperitoneal administrations in terms of alveolar rupture, pulmonary congestion, and the infiltration of inflammatory cells into the lungs [11][12][13]18,25].…”

Histopathologic differences in granulomas of Mycobacterium bovis bacille Calmette Guérin (BCG) vaccinated and non-vaccinated cattle with bovine tuberculosis

“…The vaccination dose and challenge dose varied slightly between experimental groups, however as these were < 1 log, we felt it was an acceptable range. Enumeration of Mycobacterium bovis in liquid culture is difficult due to the propensity of the bacilli to clump ( Gautam et al, 2022 ). As a result, simple optical density (OD) readings are not reliable, and due to the lengthy culture time, exact dosages are often determined retrospectively.…”

Towards More Precise Targeting of Inhaled Aerosols to Different Areas of the Respiratory System

“…Foaming also increases the so-called residual volume (the amount of liquid remaining inside the nebulizer at the end of nebulization), since the liquid is embedded in the foam that sticks to the walls of the vessel. Some reports of adding antifoaming agents to improve the nebulization of surface-active formulations are available in the literature [ 102 , 103 ].…”