Identify of Granulicatella adiacens from blood cultures of a patient bearer of prosthetic valve

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Raffaele Gargiulo *
Carla Sabia
Stefano Giordani
Virginia Agnoletto
Agostino Barozzi
Sandra Fregni
Anna Mucci
Maria Olga Zirilli
Mario Sarti
(*) Corresponding Author:
Raffaele Gargiulo | r.gargiulo@ausl.mo.it

Abstract

The clinical case studied concerns a woman 81 years old, with a history of prosthetic valve and mitral insufficiency, admitted to internal medicine ward of NOCSAE hospital as a result of a recurrent fever. Due to the suspicion of endocarditis and with the aim to identify the presence of aerobic/anaerobic microorganisms, two set of blood cultures collected within 24 hours were sent to the Laboratory of microbiology. All the bottles were incubated into the Bact-Alert 3D System (bioMérieux). After an 19 hours incubation time, the samples were identified as positive by the automated system; consequently they cultured on a blood agar and selective media, according to our laboratory operational protocol. In the same time Gram stain of the cultural broth revealed the presence of Gram positive cocci arranged in chains different in length. Since there wasn’t an evident microbial growth on solid media after 24-48 hours of incubation, a new culture was carried out on blood and chocolate agar after the addition of Staphylococcus aureus ATCC 25923. After 24 hours of incubation it was possible appreciate the growth of tiny colonies around the S. aureus ones. These colonies were identified by Vitek2 and Api Rapid 32 Strep (bioMérieux) as Granulicatella adiacens. The results were confirmed by PCR and sequencing of the groESL gene. MIC values obtained by the means of E-test (bioMérieux) were: 0.016mg/L for penicillin, 0.125mg/L for cefotaxime, 1mg/L for both vancomicin and levofloxacin. Resistance was observed for cloramphenicol (MIC=16mg/L). The timely communication of these findings, supported by clinical data like the appearance of vegetation on mitral valve highlighted by trans-oesophageal echocardiography, allowed to establish an adequate antibiotic therapy, rapid resolution of fever and normalisation of inflammatory parameters.

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