In vitro Effects of Antimicrobial Agents on Planktonic and Biofilm Forms of Staphylococcus saprophyticus Isolated From Patients With Urinary Tract Infections.

Katheryne Benini Martins,Adriano Martison Ferreira,Maria De Lourdes Ribeiro De Souza Da Cunha Cunha,Luiza Pinheiro,Valéria Cataneli Pereira,Adilson De Oliveira

doi:10.3389/fmicb.2019.00040

Katheryne Benini Martins, Adriano Martison Ferreira + Show 4 more

Open Access

https://doi.org/10.3389/fmicb.2019.00040

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Abstract

Bacterial biofilms play an important role in urinary tract infections (UTIs), being responsible for persistent infections that lead to recurrences and relapses. Staphylococcus saprophyticus is one of the main etiological agents of UTIs, however, little is known about biofilm production in this species and especially about its response to the antimicrobial agents used to treat UTIs when a biofilm is present. For this reason, the aim of this work was to evaluate the response of S. saprophyticus biofilms to five antimicrobial agents. Staphylococcus saprophyticus was evaluated for antimicrobial susceptibility in its planktonic form by means of minimum inhibitory concentration (MIC) and in biofilms by means of minimum inhibitory concentration in biofilm (MICB) against the following antimicrobial agents by the microdilution technique: vancomycin, oxacillin, trimethoprim/sulfamethoxazole, ciprofloxacin, and norfloxacin. Of the 169 S. saprophyticus studied, 119 produced a biofilm as demonstrated by the polystyrene plate adherence method. Biofilm cells of S. saprophyticus exhibited a considerable increase in MICB when compared to the planktonic forms, with an increase of more than 32 times in the MICB of some drugs. Some isolates switched from the category of susceptible in the planktonic condition to resistant in the biofilm state. Statistical analysis of the results showed a significant increase in MICB (p < 0.0001) for all five drugs tested in the biofilm state compared to the planktonic form. Regarding determination of the minimum bactericidal concentration in biofilm (MBCB), there were isolates for which the minimum bactericidal concentration of all drugs was equal to or higher than the highest concentration tested.

Highlights

In order to survive in hostile environments such as in host tissues or on an inert surface where they are exposed to inhospitable conditions (UV light, desiccation, heat, cold), bacteria adapt by forming adherent populations organized in a structure called biofilm (Mah and O’Toole, 2001).Li et al (2005) demonstrated that biofilm formation in Staphylococcus spp. depends on Polysaccharide Intercellular Adhesin (PIA), whose biosynthesis is mediated by the ica operon
Statistical analysis of the results showed a significant increase in minimum inhibitory concentration in biofilm (MICB) (p < 0.0001) for all five drugs tested in the biofilm state compared to the planktonic forms (Figure 2)
Antimicrobial susceptibility testing for antibiotic selection continues to be performed using planktonic cells, a fact that impairs evaluation of the efficacy of the antimicrobial tested since these bacteria are protected by the biofilm in the patient and the response will not be the same as obtained in the tests

Summary

Introduction

Li et al (2005) demonstrated that biofilm formation in Staphylococcus spp. depends on Polysaccharide Intercellular Adhesin (PIA), whose biosynthesis is mediated by the ica operon. This operon contains the icaADBC genes and the regulatory icaR gene, which is transcribed in the direction opposite to the ica operon. In the case of the icaR gene, some studies have suggested that its product is a transcription repressor that plays an adaptive role in the regulation of the expression of the ica operon according to environmental conditions. In addition to PIA, the existence of ica-independent mechanisms for biofilm formation in Staphylococcus spp., such as proteins and DNA, has been highlighted (Mendoza-Olazarán et al, 2015)

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