STUDY OF BACTERIA CAUSING RESPIRATORY TRACT INFECTIONS AND THEIR ANTIMICROBIAL SUSCEPTIBILITY

Abstract

This study (from January 2020 to June 2020) aimed to determine the antibacterial susceptibility of respiratory tract disease-causing bacteria to chosen antibiotics using the Kirby–Bauer disk diffusion method. 55 respiratory tract specimens were collected from patients with respiratory illness who visited Jinnah Hospital, Lahore, across different age groups . The samples were labeled and processed  in the Microbiology Laboratory of Allama Iqbal Medical College, Lahore, following standard laboratory operating protocols. Bacterial isolates were identified based on colony morphology, Gram staining, and biochemical properties.

Samples were streaked  on appropriate agar media and cultured them at 37°C for 24 hours to isolate pure colonies. The bacterial isolates in pure colony comprised 75% Gram-negative bacteria and 25% Gram-positive bacteria. The bacteria identified were Escherichia coli, Klebsiella spp., Pseudomonas spp., Acinetobacter spp., Streptococcus spp., and Staphylococcus spp. Antimicrobial susceptibility testing was performed on Mueller–Hinton agar using the Kirby–Bauer disc diffusion method according to CLSI 2020 standards.Ampicillin, Gentamicin, Ciprofloxacin, and Ceftriaxone were tested on all bacterial isolated, but ampicillin-sulbactam was tested against Acinetobacter only . Quality control was performed with ATCC reference strains.

Data were analyzed with GNU PSPP Version 2.1.1. Descriptive statistics and the chi-square test were used. Ampicillin and ciprofloxacin showed highly significant differences between susceptible and resistant isolates (p < 0.001). Ceftriaxone showed no statistically significant difference (p = 0.390). Gentamicin showed a highly significant difference (p = 0.002). Ampicillin-sulbactam also showed a statistically significant difference among the Acinetobacter isolates (p = 0.007).

Ampicillin exhibited low activity against Gram-negative isolates, while ciprofloxacin showed poor activity against Gram-positive isolates. Gentamicin showed good activity against Staphylococcus aureus, and ceftriaxone showed good activity against Streptococcus isolates. Acinetobacter showed poor sensitivity to ampicillin-sulbactam. The findings highlight the need for routine antimicrobial susceptibility testing and proper antibiotic administration to minimize antibiotic resistance.