Comparison of In-vitro Activity of Cefixime to Doxycycline and Minocycline Against Gram-Negative Bacteria Isolated from Patients Suffering from Respiratory Tract Infections at a Tertiary Care Centre in Northern India

Background: Respiratory tract infections (RTI) form a major part of common ailments encountered by a general physicians hailing from a developing country. Antibiotics are used for treating any infection but inappropriate use of antibiotics lead to development of multidrug resistance (MDR). This study was performed to analyze the comparative in-vitro activity of Cefixime and Tetracyclines by antibiotic susceptibility testing (AST) against the pathogens isolated from respiratory samples.

Materials and Methods: We performed a prospective study in the Bacteriology section of the Department of Microbiology at a teaching hospital in Northern India from Jan 2022 to June 2022. Cefixime, Doxycycline, and Minocycline were tested for susceptibility against 100 Gram-negative bacteria from respiratory samples. The antibiotic susceptibility testing for each of the isolates was performed by the Kirby Bauer Disc Diffusion method, according to the CLSI, 2019 guidelines.

Results: Our study cohort included 100 Gram negative isolates with a majority of them obtained from Endotracheal aspirate samples (43, 43%) followed by Sputum (37, 37%) samples. The most common microorganism tested for susceptibility to this drug was Klebsiella pneumoniae (39, 39%) followed by Escherichia coli (33, 33%). Escherichia coli was identified as the most isolated to all the antibiotics and was 12.12% (4/33, 12.12%) susceptible to all three drugs. On overall analysis activity of Doxycycline was better than Cefixime among inducible Enterobacteriaceae and non-fermenter isolate.

Conclusion: Doxycycline is a proficient antimicrobial agent for treating an array of Gram-negative bacteria-associated infections showing better in-vitro activity in comparison to Minocycline and other bactericidal agents like Cefixime.