BACTERIAL PATHOGENS AND THEIR ANTIBIOTIC RESISTANCE PATTERN FROM LOWER RESPIRATORY TRACT INFECTIONS IN A TERTIARY CARE HOSPITAL

Abstract

Background: Lower respiratory tract infections (LRTIs) are a major cause of
morbidity and mortality, particularly among hospitalized and immunocompromised
patients. The increasing prevalence of multidrug-resistant (MDR) bacterial pathogens
complicates treatment and highlights the need for continuous surveillance. This study
aimed to identify predominant bacterial pathogens in LRTIs, assess their antibiotic
resistance patterns, and evaluate their clinical and epidemiological implications in a
tertiary care hospital setting.
Methods: A hospital-based observational study was conducted at Konaseema
Institute of Medical Sciences and Research Foundation, Amalapuram. A total of 830
respiratory samples (sputum, endotracheal aspirates, bronchoalveolar lavage, and
pleural fluid) were collected from patients with suspected LRTIs. Bacterial
identification was performed using standard microbiological methods, including
culture, Gram staining, and biochemical tests, with confirmation through automated
systems where necessary. Antibiotic susceptibility testing (AST) was conducted
using the Kirby-Bauer disk diffusion method, following CLSI guidelines. Chi-square
tests, Fisher’s exact test, and Z-tests for proportions were applied to compare
bacterial prevalence and resistance patterns. Spearman’s rank correlation analysis
was used to explore relationships between resistance patterns, and 95% confidence
intervals were calculated to assess the precision of susceptibility estimates.
Results: Among the 830 respiratory samples, 423 (52.2%) were culture-positive,
with Klebsiella spp. (28.8%) being the most frequently isolated pathogen, followed
by Pseudomonas spp. (21.0%), Streptococcus spp. (15.4%), Staphylococcus aureus
(13.8%), Acinetobacter spp. (11.8%), and E. coli (6.7%). Chi-square analysis showed
a significant difference (p = 0.018) in prevalence between Klebsiella spp. and
Pseudomonas spp., while Fisher’s exact test confirmed a significantly higher
prevalence of Acinetobacter spp. compared to E. coli (p = 0.008).
In Enterobacterales (E. coli and Klebsiella spp.), susceptibility to Meropenem was
74% and 68%, respectively, with no significant difference (p = 0.435). NonFermenters (Pseudomonas and Acinetobacter spp.) exhibited high susceptibility to
Piperacillin-Tazobactam (79%) and Meropenem (73%), while Acinetobacter spp.
showed 96% susceptibility to Cefoperazone-Sulbactam, with a tight confidence
interval (95% CI: 90.6–100%). Among Gram-positive cocci, S. aureus demonstrated
high susceptibility to Vancomycin (85%) and Linezolid (95%) but showed low
Cefoxitin susceptibility (16%), suggesting a high prevalence of MRSA.
Conclusion: The study highlights the significant burden of MDR bacterial pathogens
in LRTIs, particularly among Gram-negative organisms such as Klebsiella and
Pseudomonas spp. The high prevalence of MRSA and carbapenem-resistant isolates
underscores the need for strict antimicrobial stewardship and infection control
strategies. The highly reliable Cefoperazone-Sulbactam susceptibility in
Acinetobacter spp. suggests its potential as a treatment option. Continuous
surveillance of resistance patterns and tailored empirical therapy are critical to
improving patient outcomes and preventing further resistance escalation.