Does the human skin microbiome adapt to antibiotic exposure?

Khan, R

Abstract

Staphylococcus epidermidis is a substantial element of the healthy human skin microflora and can become pathogenic to cause infections, for example, septicaemia and endocarditis. The effects of long-term sub-lethal exposure to antibiotics on the skin microbiota are unknown. How does antibiotic adaptation affect the ability of S. epidermidis to interact with host immune systems, inhibit pathogens and keep a healthy microflora? This project aims to characterise five S. epidermidis bacteria samples isolated from the skin, before and after exposure to antibiotics thus comparing their antibiotic susceptibility pattern (disc diffusion assay), biofilm formation (crystal violet microtitre plate assay) and microbial virulence (G. mellonella infection assay). Serially passaged antibiotic-adapted strains were also assessed for the following characteristics: colony and cell morphology, cross-resistance (to other antibiotics), growth rate and competitive fitness ability. S. epidermidis parent strains were firstly susceptible to antibiotics such as erythromycin and doxycycline, and later formed adaptive resistance. Erythromycin adapted strains were found to be resistant to erythromycin and cross- resistant to doxycycline based on both disk diffusion assay and MIC results. Doxycycline adapted strains formed resistance to doxycycline based on both disk diffusion assay and MIC results. Significant differences (p <0.05) were observed in the mean relative biofilm units and G. mellonella infection assay survival rates of antibiotic-adapted strains of S. epidermidis. Erythromycin adapted strain had significantly enhanced fitness advantage (w value- 1.35, p value- 0.0427) and were significantly virulent (p-value of 0.0065) when compared to the parent strain. Doxycycline adapted strain showed significantly lower fitness advantage (w value- 0.38, p-value 0.0005) yet, they were significantly virulent (p-value of 0.0059) in comparison to the parent strain. These findings highlight the implications of adaptive resistance to antibiotics in the treatment of S. epidermidis infections, and therefore necessitate the development of more sophisticated future treatments for bacterial infections. It is important for the private and public healthcare sectors worldwide to invest in the advancement of new anti-infectives to combat the growing antibiotic resistance.

Citation

Khan, R. Does the human skin microbiome adapt to antibiotic exposure?. (Dissertation). University of Salford

• Thesis Type: Dissertation
• Deposit Date: Dec 18, 2019
• Publicly Available Date: Dec 18, 2019
• Award Date: Jan 1, 2019