Modulation of Haemophilus influenzae interaction with hydrophobic molecules by the VacJ/MlaA lipoprotein impacts strongly on its interplay with the airways

Abstract

Airway infection by nontypeable Haemophilus influenzae (NTHi) associates to chronic obstructive pulmonary disease (COPD) exacerbation and asthma neutrophilic airway inflammation. Lipids are key inflammatory mediators in these disease conditions and consequently, NTHi may encounter free fatty acids during airway persistence. However, molecular information on the interplay NTHi-free fatty acids is limited, and we lack evidence on the importance of such interaction to infection. Maintenance of the outer membrane lipid asymmetry may play an essential role in NTHi barrier function and interaction with hydrophobic molecules. VacJ/MlaA-MlaBCDEF prevents phospholipid accumulation at the bacterial surface, being the only system involved in maintaining membrane asymmetry identified in NTHi. We assessed the relationship among the NTHi VacJ/MlaA outer membrane lipoprotein, bacterial and exogenous fatty acids, and respiratory infection. The vacJ/mlaA gene inactivation increased NTHi fatty acid and phospholipid global content and fatty acyl specific species, which in turn increased bacterial susceptibility to hydrophobic antimicrobials, decreased NTHi epithelial infection, and increased clearance during pulmonary infection in mice with both normal lung function and emphysema, maybe related to their shared lung fatty acid profiles. Altogether, we provide evidence for VacJ/MlaA as a key bacterial factor modulating NTHi survival at the human airway upon exposure to hydrophobic molecules.

Evolution toward maximum transport capacity of the Ttg2 ABC system inPseudomonas aeruginosa

“…In Burkholderia cepacia complex species mla genes are required for swarming motility and serum resistance 28 . Furthermore, in nontypeable Haemophilus influenzae (NTHi), it is considered a key factor for bacterial survival in the human airway upon exposure to hydrophobic antibiotics 27 . In S. flexneri , B. pseudomallei and NTHi the role of the mla operon in virulence has been inferred from mutants for the gene vacJ ( mlaA ) 72, 73 .…”

“…MlaC would then transport the phospholipids across the periplasm and deliver them to MlaD for active internalization through the IM 23 . Deletion of the genes of this system is known to destabilize the OM, and bacterial strains lacking any of the Mla components are more susceptible to membrane stress agents 19, 24, 25, 26, 27, 28, 29, 30 . More recently, the retrograde transport hypothesis has been questioned and a new role for this system in anterograde phospholipid transport has been suggested 29, 31 .…”

Preclinical Evaluation of the Antimicrobial-Immunomodulatory Dual Action of Xenohormetic Molecules against Haemophilus influenzae Respiratory Infection

“…A mouse model of NTHi lung infection was used as previously described [42]. CD1 female mice (18-20 g) aged 4-5 weeks purchased from Charles River Laboratories (France) were housed under pathogen-free conditions at the Institute of Agrobiotechnology facilities (registration number ES/31-2016-000002-CR-SU-US).…”

“…Based on these observations, quercetin was shortlisted to next assess its modulatory effect on the NTHi-host airway interplay. NTHi375 was used for this purpose, given that it has been previously used in host-pathogen interaction studies [42,[47][48][49].…”

Pharmacokinetic-Pharmacodynamic Characterization of Omadacycline against Haemophilus influenzae Using a One-Compartment In Vitro Infection Model

“…However, PK-PD evaluations for H. influenzae using in vivo infection models are challenging. This is primarily due to the fact that H. influenzae does not grow well and auto clears in murine infection models [15,16], even the neutropenic thigh infection model, the workhorse infection model that has been used to characterize the PK-PD of essentially on August 15, 2020 by guest http://aac.asm.org/ Downloaded from all classes of antimicrobial agents to-date [17,18]. In such cases, in vitro infection models have allowed for the characterization of PK-PD of a given antimicrobial agent against H. influenzae [19,20,21,22].…”