Sub-Inhibitory Concentration of Piperacillin–Tazobactam May be Related to Virulence Properties of Filamentous Escherichia coli

Abstract

Sub-inhibitory concentrations of antibiotics are always generated as a consequence of antimicrobial therapy and the effects of such residual products in bacterial morphology are well documented, especially the filamentation generated by beta-lactams. The aim of this study was to investigate some morphological and pathological aspects (virulence factors) of Escherichia coli cultivated under half-minimum inhibitory concentration (1.0 µg/mL) of piperacillin-tazobactam (PTZ sub-MIC). PTZ sub-MIC promoted noticeable changes in the bacterial cells which reach the peak of morphological alterations (filamentation) and complexity at 16 h of antimicrobial exposure. Thereafter the filamentous cells and a control one, not treated with PTZ, were comparatively tested for growth curve; biochemical profile; oxidative stress tolerance; biofilm production and cell hydrophobicity; motility and pathogenicity in vivo. PTZ sub-MIC attenuated the E. coli growth rate, but without changes in carbohydrate fermentation or in traditional biochemical tests. Overall, the treatment of E. coli with sub-MIC of PTZ generated filamentous forms which were accompanied by the inhibition of virulence factors such as the oxidative stress response, biofilm formation, cell surface hydrophobicity, and motility. These results are consistent with the reduced pathogenicity observed for the filamentous E. coli in the murine model of intra-abdominal infection. In other words, the treatment of E. coli with sub-MIC of PTZ suggests a decrease in their virulence.

Sub-Optimal Treatment of Bacterial Biofilms

“…The morphology of cells can also be altered by exposing planktonic cells to a sub-lethal concentration of antibiotic, causing a direct effect on the ability to form biofilm. For instance, treating E. coli cells with a sub-inhibitory concentration of piperacillin or a combination of piperacillin and tazobactam resulted in filamentation [ 61 , 62 ]. Generation of the filamentous form of E. coli cells was accompanied by the inhibition of virulence factors, biofilm formation, cell surface hydrophobicity and motility, concordant with a reduction in the pathogenicity observed for the filamentous E. coli in a murine model of intra-abdominal infection [ 62 ].…”

AVALIAÇÃO DA TOXICIDADE AGUDA E DA CITOTOXICIDADE DOS EXTRATOS ETANÓLICOS DA MACRÓFITA Hydrocotyle bonariensis LAM (APIACEAE)

“…One reference strain (Bacteroides fragilis ATCC 25285) and two clinically isolated from patients with IAIs were evaluated (named P34 and P50). The clinical strains were isolated, identified and had their susceptibility profile stablished in a previous study (FERREIRA et al, 2016) were then incubated in anaerobic chamber at 37°C and 100 μL aliquots of each bacterial culture were removed in triplicate to read the OD at 550 nm every 3 h up to 72 h (DOS SANTOS et al, 2007;VELOSO et al, 2013;DE ANDRADE et al, 2016). Capsule Detection -The Hiss staining method was used with modifications (NAKANO et al, 2004).…”

“…Resistance to H2O2 -This test was performed using disk diffusion assays (DE ANDRADE et al, 2016). The microplates were incubated in anaerobiosis at 37°C for different times (determined on the growth curve: 30, 48, 72 and 96 h).…”

“…The solution contained in each well was transferred to a new, dry and clean plate. The absorbance was quantified in the spectrophotometer (Thermo Scientific Multiskan® Spectrum, Vantaa, Finland) at a wavelength of 550 nm (DOS SANTOS et al, 2007;FERREIRA et al, 2016). The tests were performed in quadruplicate and repeated on three different occasions.…”

“…It is also able to withstand the reactive oxygen species produced by the host's defenses and persists in oxygenated tissues (TEIXEIRA et al, 2018). VELOSO et al, 2013;DE ANDRADE et al, 2016;CLSI, 2017).…”