bacteria etiological agents causing lower respiratory tract infections and their resistance patterns

background: lower respiratory tract infections (ltris) are among the most common infectious diseases with potential life-threatening complications. methods: the study consisted of 426 patients with suspected ltris from mid and far western region of nepal between september 2011 and july 2014. the specimens were collected and processed according to the standard microbiological methods at the central laboratory of microbiology of nepalgunj medical college, nepal. results: among the isolated gram-positive organisms, streptococcus pneumonia (n = 30, 51.7%) was the most predominant pathogen, followed by staphylococcus aureus (n = 28, 48.3%). among the isolated gram-negative organisms, pseudomonas aeruginosa (n = 71, 35.32%) was the most predominant pathogen, followed by haemophilus influenzae (n = 68, 33.83%), klebsiella pneumonia (n = 36, 17.19%), and escherichia coli (n = 26, 12.94%). the pattern of resistance varied regarding the bacteria species, and there were multi-resistant isolates. also, a significant difference (p < 0.05) was observed between males and females for each type of bacterial species. among 259 isolates, 86 (33.20%) were from children aged 1-10 years, which were statistically significant (p < 0.05) compared to the other age groups. conclusions: p. aeruginosa and h. influenzae (gram-negative) and s. pnemoniae (gram-positive) were the most common bacterial isolates recovered from ltris. age group of 1-10 years old was at a higher risk. many isolates showed appreciable levels of antibiotic resistance due to antibiotic abuse. there is a need to increase surveillance and develop better strategies to curb the increasing prevalence of lrti in this region of nepal.