Effect of subinhibitory concentrations of tigecycline and ciprofloxacin on the expression of biofilm-associated genes and biofilm structure of Staphylococcus epidermidis

Abstract

Staphylococcus epidermidis is a leading cause of foreign body-associated infections. This is related to the bacterium's ability to form biofilms on synthetic materials. Bacteria within a biofilm may be exposed to subinhibitory concentrations (sub-MICs) of antibiotics because of an agent's limited penetration into the biofilm core. Here, we investigated the effect of sub-MICs of tigecycline and ciprofloxacin on the expression of biofilm-associated genes, i.e. icaA, altE and sigB, and the biofilm structure of five clinical isolates of S. epidermidis. For most tested isolates, the expression of these genes increased after exposure to 0.25 MIC and 0.5 MIC tigecycline. A slight decrease in icaAmRNA levels was observed only in two isolates in the presence of 0.25 MIC tigecycline. The effect of ciprofloxacin exposure was isolate-dependent. At 0.5 MIC, ciprofloxacin induced an increase of sigB and icaAmRNA levels in three of the five tested isolates. At the same time, expression of the altE gene increased in all isolates (from 1.3-fold to 42-fold, depending on the strain). Confocal laser scanning microscopy analysis indicated that sub-MIC ciprofloxacin decreased biofilm formation, whereas tigecycline stimulated this process. Our data suggest that sub-MIC tigecycline may have bearing on the outcome of infections.

<p>Effects of sub-inhibitory concentrations of meropenem and tigecycline on the expression of genes regulating pili, efflux pumps and virulence factors involved in biofilm formation by<em> Acinetobacter baumannii</em></p>

“…Inconsistent with our results, Maestre et al33 and Chen et al34 reported that tigecycline at its sub-inhibitory concentrations interfered with forming biofilm by E. faecalis and A. baumannii strains, respectively. However, in contrast to our results, Szczuka et al35 and Weiser et al36 indicated that tigecycline induced forming biofilm by S. epidermidis through overexpression of extracellular matrix binding protein (Embp) and other biofilm-associated genes, suggesting that the effects of sub-MICs of tigecycline are almost dependent on bacterial species. In our study, tigecycline at sub-MICs decreased significantly the biofilm formation in these four representative strains whereas meropenem decreased significantly the biofilm formation only in two representative strains, suggesting that tigecycline rather than meropenem can interfere with the induction of biofilm formation in A. baumannii strains.…”

Characterization of biofilm production in different strains of Acinetobacter baumannii and the effects of chemical compounds on biofilm formation

“…In this study, tannic acid and LL-37 at a concentration below its MIC can decrease biofilm formation, which might occur by causing structural damage to the A. baumannii biofilm (Shi et al, 2014). One previous study has demonstrated increased biofilm formation of Staphylococcus epidermidis after sub-MIC tigecycline treatment (both at 0.25 and 0.5 MIC) by producing increased expression of the icaA (production of transmembrane protein), altE (encoding autolysin related with adhesion) and sigB (biofilm stability) genes and by affecting biofilm architecture in the isolates (Szczuka, Jablonska & Kaznowski, 2017). To explore the mechanism by which sub-MIC tigecycline increased the biofilm formation of A. baumannii, more future relevant studies are needed.…”

Clinical Impact of Antibiotics for the Treatment of Pseudomonas aeruginosa Biofilm Infections

“…The use of daptomycin-lock therapy (50 mg/ml) also showed a therapeutic advantage for the 24 h-treatment of a long-term catheter-related bloodstream infections by coagulase-negative S. epidermidis in a rabbit model (Basas et al, 2018). Similarly, subinhibitory concentrations of fluoroquinolones were able to reduce the number of sessile cells to prevent the adhesion of the corresponding S. epidermidis strains and to alter biofilm morphology (Szczuka et al, 2017).…”