Mucins are highly glycosylated proteins that form the structural basis of mucus and represent a key component of innate immunity at mucosal surfaces, particularly in the respiratory tract. Beyond their mechanical barrier function, mucins actively participate in pathogen trapping, regulation of mucociliary clearance, modulation of inflammatory responses, and maintenance of epithelial homeostasis. Dysregulation of mucin synthesis, composition, or transport contributes to mucus hypersecretion, impaired airway clearance, and chronic inflammation in respiratory diseases such as asthma, chronic obstructive pulmonary disease, and cystic fibrosis. This review summarizes current insights into mucin biology, including their biosynthesis, structure, classification, and regulation, with emphasis on the gel-forming mucins MUC5AC and MUC5B. The role of mucins in mechanical protection, host–pathogen interactions, control of inflammation, and coordination of innate immune responses is reviewed. Attention is given to the interplay between mucins, immune cells, and microbial communities in maintaining airway barrier integrity. The article further examines mucoactive therapeutic strategies aimed at restoring mucus barrier function. Expectorants, mucolytics, mucoregulators, and mucokinetic agents are reviewed with respect to their mechanisms of action and clinical relevance. Established drugs, including N-acetylcysteine, carbocysteine, dornase alfa, ambroxol, and hypertonic solutions, are considered alongside emerging molecular targets such as NF-κB-dependent regulation of mucin expression, calcium-activated chloride channels, MARCKS-mediated mucin exocytosis, purinergic signaling pathways, and NO/cGMP signaling. Non-pharmacological approaches, including airway clearance techniques and respiratory rehabilitation, are covered concisely. Conclusions: Overall, this review highlights mucins as dynamic regulators of innate immunity and underscores the need for mechanism-based, personalized mucoactive therapies to improve outcomes in chronic inflammatory airway diseases.

Background: Effective empirical therapy and antimicrobial stewardship rely on up-to-date local data on respiratory pathogens and antimicrobial resistance trends. In Kazakhstan, contemporary microbiological surveillance remains limited, particularly for hospitalized patients with chronic pulmonary disease (COPD) and pneumonia. This study aimed to characterize the microbial profiles and antimicrobial susceptibility patterns in respiratory specimens from these patient groups in Almaty, Kazakhstan. Methods: This retrospective observational study included adult patients hospitalized at a tertiary referral center between January 2024 and December 2025. Respiratory specimens (sputum and bronchoalveolar lavage) underwent bacterial culture, species identification using MALDI-TOF MS, and antimicrobial susceptibility testing via EU-CAST disk diffusion. Susceptibility was interpreted according to EUCAST categories (S, I, R). Group comparisons were performed using Pearson’s chi-square or Fisher’s exact test with Benjamini-Hochberg correction. Results: Among 713 patients (255 COPD exacerbation; 458 pneumonia), Streptococcus pyogenes was the most frequently isolated organism in both groups, followed by viridans group streptococci (VGS) and Streptococcus pneumoniae. Gram-negative isolates included most frequently Klebsiella pneumoniae, Klebsiella aerogenes, and Pseudomonas aeruginosa. After correction for multiple testing, bacterial distribution did not differ significantly between COPD and pneumonia. Streptococcal isolates demonstrated consistently high susceptibility to β-lactams, while susceptibility to macrolides, clindamycin, and doxycycline was lower. Gram-negative organisms demonstrated more variable resistance profiles. MDR phe-notypes were common among K. pneumoniae (16.7% COPD; 31.0% pneumonia) and P. aeruginosa (22.2% COPD; 17.9% pneumonia), with no significant between group dif-ferences. Conclusions: COPD exacerbation and pneumonia patients showed broadly similar bacterial profiles, whereas antimicrobial susceptibility varied substantially across species. High β-lactam activity against streptococci contrasted with complex resistance patterns and notable MDR/XDR phenotypes among Gram-negative organisms. These findings highlight the importance of ongoing institution-specific surveillance to support antimicrobial stewardship and guide empirical treatment decisions.