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. 2019 Oct 21;19(1):228.
doi: 10.1186/s12866-019-1596-2.

Microbial biofilm correlates with an increased antibiotic tolerance and poor therapeutic outcome in infective endocarditis

Enea Gino Di Domenico  1 , Sara Giordana Rimoldi  2 , Ilaria Cavallo  3 , Giovanna D'Agosto  3 , Elisabetta Trento  3 , Giovanni Cagnoni  4 , Alessandro Palazzin  2 , Cristina Pagani  2 , Francesca Romeri  2 , Elena De Vecchi  5 , Monica Schiavini  6 , Daniela Secchi  2 , Carlo Antona  4 , Giuliano Rizzardini  6 , Rita Barbara Dichirico  2 , Luigi Toma  7 , Daniela Kovacs  8 , Giorgia Cardinali  8 , Maria Teresa Gallo  3 , Maria Rita Gismondo  2 , Fabrizio Ensoli  3
Affiliations

Microbial biofilm correlates with an increased antibiotic tolerance and poor therapeutic outcome in infective endocarditis

Enea Gino Di Domenico et al. BMC Microbiol. .

Abstract

Background: Infective endocarditis (IE) is associated with high rates of mortality. Prolonged treatments with high-dose intravenous antibiotics often fail to eradicate the infection, frequently leading to high-risk surgical intervention. By providing a mechanism of antibiotic tolerance, which escapes conventional antibiotic susceptibility profiling, microbial biofilm represents a key diagnostic and therapeutic challenge for clinicians. This study aims at assessing a rapid biofilm identification assay and a targeted antimicrobial susceptibility profile of biofilm-growing bacteria in patients with IE, which were unresponsive to antibiotic therapy.

Results: Staphylococcus aureus was the most common isolate (50%), followed by Enterococcus faecalis (25%) and Streptococcus gallolyticus (25%). All microbial isolates were found to be capable of producing large, structured biofilms in vitro. As expected, antibiotic treatment either administered on the basis of antibiogram or chosen empirically among those considered first-line antibiotics for IE, including ceftriaxone, daptomycin, tigecycline and vancomycin, was not effective at eradicating biofilm-growing bacteria. Conversely, antimicrobial susceptibility profile of biofilm-growing bacteria indicated that teicoplanin, oxacillin and fusidic acid were most effective against S. aureus biofilm, while ampicillin was the most active against S. gallolyticus and E. faecalis biofilm, respectively.

Conclusions: This study indicates that biofilm-producing bacteria, from surgically treated IE, display a high tolerance to antibiotics, which is undetected by conventional antibiograms. The rapid identification and antimicrobial tolerance profiling of biofilm-growing bacteria in IE can provide key information for both antimicrobial therapy and prevention strategies.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Confocal microscopy analysis of biofilms. Representative images of biofilms developed on polystyrene pegs following 24 h incubation at 37 °C. Green indicates viable bacteria, and red dead bacteria. Orthogonal sections displaying horizontal (z) and side views (x and y) of reconstructed 3D biofilm images are shown. The eight bacterial isolates (N1–8) are classified into Moderate (M) or High (H) biofilm-producers according to cBRT
See this image and copyright information in PMC

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