Bacteriological Spectrum and Antibiotic Utilization in Community-Acquired Pneumonia: An Observational Study at a...

Community-acquired pneumonia (CAP) is a leading cause of hospitalization and infectious disease mortality. Regional data on pathogen distribution, antimicrobial susceptibility, and antibiotic utilization patterns are essential for rational prescribing. The COVID-19 pandemic has further altered the epidemiology of respiratory infections and antibiotic prescribing practices in many settings. This study aimed to characterize the bacteriological profile, antibiotic susceptibility patterns, and antimicrobial utilization trends, including defined daily dose (DDD) and antibiotic consumption index (ACI), in hospitalized CAP patients at a tertiary care center.

A prospective observational study was conducted from September 2019 to March 2020 at Sarojini Naidu Medical College, Agra, involving 130 adult CAP patients. Sputum cultures and Kirby-Bauer disk diffusion susceptibility testing were performed. Antibiotic prescriptions were analyzed using the Anatomical Therapeutic Chemical (ATC)/DDD methodology, and ACI was calculated per 100 bed-days.

A causative organism was identified in 101 of 130 cases (77.6%). Streptococcus pneumoniae (n=40, 30.8%) was the most common pathogen, followed by Klebsiella pneumoniae (n=27, 20.8%), Escherichia coli (n=24, 18.5%), Staphylococcus aureus (n=8, 6.2%), and Pseudomonas aeruginosa (n=2, 1.5%). Linezolid (100%) and carbapenems demonstrated the highest sensitivity; ampicillin and amoxicillin-clavulanic acid showed the highest resistance. Amoxicillin-clavulanic acid was the predominant empirical antibiotic (n=73, 56.2%; ACI: 14.4 DDD/100 bed-days), while levofloxacin was the most prescribed definitive agent (n=33, 25.4%; ACI: 14.8 DDD/100 bed-days). A paired analysis of antibiotics with complete empirical and definitive tracking data (n=7) showed no statistically significant overall shift in consumption volume (paired t-test, p=0.5948), though prescribing shifted markedly from frontline oral agents toward restricted broad-spectrum agents. Poly-antibiotic prescriptions were used in 115 of 130 patients (88.4%).

A significant proportion of isolates demonstrated resistance to commonly used antibiotics such as beta-lactams. Streptococcus pneumoniae remains the dominant pathogen, but the substantial burden of Gram-negative organisms with high resistance to first-line agents underscores the need for culture-guided therapy.