Thermal susceptibility and antibiotic synergism of methicillin-resistant Staphylococcus aureus biofilms

Abstract

Methicillin-Resistant Staphylococcus aureus (MRSA) biofilms are among the most dangerous infections on medical implants, typically requiring surgical explantation and replacement. This study investigated the thermal susceptibility of MRSA biofilms to thermal shocks from 60 to 80 °C for 1–30 min as well as the effect of various antibiotics (most notably methicillin) on thermal mitigation. Pre- and post-shock exposure to three different classes of antibiotics (ciprofloxacin, tobramycin, and methicillin) at concentrations ranging from 0.25 to 128 μg mL⁻¹ were investigated. MRSA biofilms exhibited thermal susceptibility comparable to other common nosocomial pathogens, such as Pseudomonas aeruginosa, though with greater variability. Exposure to antibiotics of any class significantly decreased the degree of thermal shock required for reliable mitigation, including at subclinical concentration. These combined treatments reduced biofilm population more than the sum of thermal and chemical treatments alone, demonstrating synergism, while also indicating a critical population drop of ∼4.5 log₁₀ beyond which the biofilms typically became non-viable.

GRAPHICAL ABSTRACT

Keywords:

• Biofilms
• prosthesis-related infections
• thermal shock
• methicillin
• synergism
• anti-bacterial agents

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was supported in part by the American Heart Association (18IPA34170108) and the National Science Foundation (CBET-1133297). Parnian, Parham is a PhD student supported by both Center for Biocatalysis and Bioprocessing at the University of Iowa, and NIH Predoctoral Training Program in Biotechnology (T32-GM008365).