Abstract
Escherichia coli is the most frequent agent of urinary tract infections in humans. The emergence of uropathogenic multidrug-resistant (MDR) E. coli strains that produce extended spectrum β-lactamases (ESBL) has created additional problems in providing adequate treatment of urinary tract infections. We have previously reported the antimicrobial activity of 1,8-cineole, one of the main components of Rosmarinus officinalis volatile oil, against Gram negative bacteria during planktonic growth. Here, we evaluated the antibiofilm activity of 1,8-cineole against pre-formed mature biofilms of MDR ESBL-producing uropathogenic E. coli clinical strains by carrying out different technical approaches such as counting of viable cells, determination of biofilm biomass by crystal violet staining, and live/dead stain for confocal microscopy and flow cytometric analyses. The plant compound showed a concentration- and time-dependent antibiofilm activity over pre-formed biofilms. After a 1 h treatment with 1% (v/v) 1,8-cineole, a significant decrease in viable biofilm cell numbers (3-log reduction) was observed. Biofilms of antibiotic-sensitive and MDR ESBL-producing E. coli isolates were sensitive to 1,8-cineole exposure. The phytochemical treatment diminished the biofilm biomass by 48-65% for all four E. coli strain tested. Noteworthy, a significant cell death in the remaining biofilm was confirmed by confocal laser scanning microscopy after live/dead staining. In addition, the majority of the biofilm-detached cells after 1,8-cineole treatment were dead, as shown by flow cytometric assessment of live/dead-stained bacteria. Moreover, phytochemical-treated biofilms did not fully recover growth after 24 h in fresh medium. Altogether, our results support the efficacy of 1,8-cineole as a potential antimicrobial agent for the treatment of E. coli biofilm-associated infections.
Highlights
Uropathogenic Escherichia coli is the most common cause of urinary tract infections, accounting for approximately 80% of infections [1]
Urinary tract infections caused by multidrug-resistant (MDR) E. coli strains that produce extended spectrum β-lactamases (ESBL) have become an increasing health problem
An additional virulence factor reported for uropathogenic E. coli strains is biofilm formation [1]
Summary
Uropathogenic Escherichia coli is the most common cause of urinary tract infections, accounting for approximately 80% of infections [1]. The routine therapy of urinary tract infections is based on the use of antibiotics such as β-lactams, trimethoprim, nitrofurantoin and quinolones in many countries. Over-use and misuse of these antibiotics increase the development of resistant bacteria [2]. The emergence of uropathogenic multidrug-resistant (MDR) E. coli strains that produce extended spectrum β-lactamases (ESBL) is a serious global health problem, since it can cause prolonged hospital stay, increasing morbidity, mortality, and health care costs [3]. Resistance genes coding for β-lactamases are often located on plasmids which harbor resistance genes for non- β-lactam antibiotics such as aminoglycosides and trimethoprim-sulfamethoxazole [4]. ESBL producing bacteria are commonly MDR, leaving limited antibacterial options
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