Abstract

EXPLORING THE MOLECULAR BASIS AND SUSCEPTIBILITY PATTERNS OF CARBAPENEM-RESISTANT BACTERIA

*Dr. D. Sangeetha, Ms. Ishwarya J.

ABSTRACT

A total of forty (40) bacterial strains were obtained from Helikem Diagnostics and Research laboratory, Tiruchirappalli, Tamil Nadu, India, to investigate the prevalence of Extended-Spectrum β-Lactamase (ESBL) and carbapenem resistance. Biochemical identification was carried out using standard tests such as Indole, Methyl Red, Voges–Proskauer, Citrate utilization, Urease, and Triple Sugar Iron (TSI) reactions. Antimicrobial susceptibility was determined by the Kirby–Bauer disk diffusion method in accordance with Clinical and Laboratory Standards Institute (CLSI, 2007) guidelines. ESBL detection was performed using Ceftazidime (30 µg), Cefotaxime (30 µg), and Ceftriaxone (30 µg) antibiotic discs, while carbapenem resistance was assessed using Imipenem (10 µg), Meropenem (10 µg), and Ertapenem (10 µg). Among the isolates tested, fifteen (37.5%) were confirmed as ESBL producers and eight (20%) exhibited carbapenem resistance. Phenotypic assays confirmed carbapenemase production among resistant strains. Genomic DNA was extracted using the Promega Wizard® Genomic DNA Purification Kit, and DNA purity was verified with a Nanodrop™ spectrophotometer. The 16S rRNA gene was amplified using universal primers 27F and 1492R, producing approximately 1300 bp fragments, which were sequenced and analyzed by BLASTn for molecular identification. The predominant resistant isolates were identified as Klebsiella pneumoniae (n=2), Proteus vulgaris (n=2), Citrobacter koseri (n=1), Streptococcus pneumoniae (n=1) and Pseudomonas aeruginosa (n=2). Phylogenetic analysis using MEGA X software confirmed their taxonomic relationships. The study highlights the occurrence of multidrug-resistant urinary pathogens and emphasizes the need for continuous antimicrobial resistance surveillance and stewardship in clinical laboratories.

Keywords: Carbapenem, Imepenem, Carbapenamase, Resistance, Antimicrobial Strategies.