IMPACT OF VARYING INCUBATION TEMPERATURES ON THE ANTIMICROBIAL SUSCEPTIBILITY OF BACTERIAL ISOLATES

Abstract

Background: Temperature influences bacterial physiology, affecting membrane fluidity, enzyme activity, gene regulation, and antibiotic susceptibility. This study compared antimicrobial resistance (AMR) among bacteria isolated from different thermal environments. Methods: A comparative experimental study was conducted at the Sheikh Zayed Microbiology Laboratory over four months. A total of 150 bacterial isolates were collected from cold (4°C, n=50), moderate (25–37°C, n=50), and hot (50–60°C, n=50) environments. Bacteria were identified using Gram staining and biochemical tests. Antimicrobial susceptibility was assessed against 25 antibiotics from nine drug classes using the Kirby-Bauer disk diffusion method according to CLSI guidelines. Data were analyzed using Pearson's chi-square and Kruskal-Wallis tests. Results: Multidrug resistance (MDR) was detected in 84% of isolates, with the highest prevalence in cold-environment bacteria (98%), followed by hot (80%) and moderate (74%) isolates (χ²=11.607, p=0.003). Significant differences in resistance patterns were observed for 12 antibiotics and overall resistance (Kruskal-Wallis H=24.16, p<0.001). Cold-environment isolates showed greater resistance to aminoglycosides, fluoroquinolones, and vancomycin. Hot-environment isolates were more resistant to macrolides and linezolid, while moderate-temperature isolates displayed the widest variety of resistance traits, particularly to tetracycline and nitrofurantoin. Conclusion: Environmental temperature significantly influences antimicrobial resistance patterns. Cold-adapted bacteria exhibited the highest MDR, whereas hot-adapted bacteria showed characteristic resistance to macrolides and oxazolidinones. These findings highlight the importance of considering thermal adaptation in AMR surveillance, antibiotic stewardship, and food safety.