Abstract
<title>Abstract</title> <p> <bold>Background:</bold> Respiratory tract infections (RTIs) remain an important cause of morbidity and healthcare utilisation worldwide, and their management is increasingly complicated by antimicrobial resistance (AMR). This study aimed to describe the distribution of bacterial pathogens causing RTIs among patients at King Khalid Hospital, Najran, Saudi Arabia, and to evaluate their antimicrobial resistance profiles. <bold>Methods:</bold> A cross-sectional study was conducted over a 10-month period in 2023. A total of 229 respiratory specimens were collected from patients with clinical features suggestive of RTIs. Specimens included sputum, endotracheal secretion cultures, tracheal secretion cultures and bronchoalveolar lavage samples. Bacterial identification and antimicrobial susceptibility testing were performed using standard microbiological procedures and the BD Phoenix 100 automated system. Data were analysed descriptively using frequencies and percentages. <bold>Results:</bold> Among 229 bacterial isolates recovered from respiratory specimens, <italic>Klebsiella pneumoniae</italic> was the most frequently identified organism (n=91, 39.7%), followed by <italic>Acinetobacter baumannii</italic> (n=63, 27.5%), <italic>Pseudomonas aeruginosa</italic> (n=47, 20.5%) and <italic>Escherichia coli</italic> (n=28, 12.2%). Most patients were recruited from the intensive care unit (ICU) (n=181, 79.0%), and sputum was the most frequently collected respiratory specimen (n=100, 43.7%). High resistance rates were reported for ampicillin (100%), colistin (98.3%) and ceftriaxone (96.9%). XDR isolates represented the largest resistance group (n=93, 40.6%), followed by PDR isolates (n=81, 35.4%) and MDR isolates (n=55, 24.0%). The combined ESBL+CRE+colistin resistance phenotype accounted for the largest proportion of isolates (n=182, 79.5%). XDR isolates accounted for the largest proportion in the 10–19 years group (56.5%) and 40–49 years group (53.3%), while PDR isolates accounted for 38.9% of isolates in the 30–39 years group and 37.7% in the ≥50 years group. <bold>Conclusion:</bold> This study identified a high proportion of XDR and PDR Gram-negative respiratory isolates, particularly among ICU specimens. The findings highlight the need for continued local antimicrobial resistance surveillance, regular review of empirical antibiotic guidelines, strengthened antimicrobial stewardship and targeted infection prevention measures in critical care settings. </p>