Background: Lower respiratory tract infections are among the most common infectious diseases of humans worldwide and continue to be a major cause of morbidity in Nigeria. This study focused on determining the microbial agents of lower respiratory tract infections, the effect of age and gender on its prevalence, and the susceptibility profile of bacterial isolates. Methods: Sputum specimens were collected from 1539 patients with symptoms of lower respiratory tract infections. The sputum specimens were processed to recover microbial aetiologic agents and susceptibility profiles of bacterial isolates were determined using standard techniques. Results: An overall prevalence of 18.91% of lower respiratory tract infections was observed in this study. There is no difference in the prevalence of lower respiratory tract infection between the genders (P = 0.649). The prevalence of lower respiratory tract infections increases significantly with age (P < 0.001), with patients 71 years and older having the highest prevalence. Klebsiella pneumoniae was the most predominant isolate causing lower respiratory tract infection while Acinetobacter species were the least predominant isolate. The fluoroquinolones, β-lactams, and gentamicin showed moderate to high activity. Conclusion: Gender did not affect the prevalence, but age did. β-lactams, fluoroquinolones, and gentamicin were the most active antibacterial agents and, therefore, the drugs of choice in treating lower respiratory tract infections in our setting.