Tesi di specializzazione (5 anni)
Identificazione ed antimicogramma rapido di lieviti da emocolture positive.
RICERCA TRASLAZIONALE E DELLE NUOVE TECNOLOGIE IN MEDICINA E CHIRURGIA
Corso di studi
MICROBIOLOGIA E VIROLOGIA
relatore Prof.ssa Ghelardi, Emilia
- MALDI-TOF MS
- identificazione rapida
- antimicogramma rapido
Data inizio appello
Data di rilascio
A general increase in the global trend of deep fungal infections has been reported during the last years. Epidemiological studies indicate that Candida spp. are the fourth most commonly isolated microorganisms from blood cultures (BC). <br>Herein, we performed a retrospective analysis of blood culture samples processed at the Microbiology laboratory of the Pisa University Hospital (AOUP) from January 2015 to June 2017. Our data indicate that yeast were isolated in about 6.6% of positive samples. Almost all the isolates belonged to the Candida genus, being Candida albicans and Candida parapsilosis the most represented species. The majority of the cases was registered in medical departments. <br>Clinical data report that any delay in yeast identification can increase the mortality of patients affected by fungemia, in particular if an inadequate therapy is administered. For this reason, new diagnostic approaches have been developed in order to shorten the lag time occurring from sampling and yeast identification, as well as to reduce the time required for obtaining the antimicrobial susceptibility profile.<br>The traditional diagnosis of fungemia requires 48-96 h for the identification and antifungal susceptibility testing (AFST) of isolated yeast. Different rapid methods have been recently described for being able to directly identify yeast from positive BC, showing 56 to 95.9% concordance with conventional methods. Despite the identification results can provide an indication about empirical antifungal treatment, there is a pressing need for rapid AFST methods. <br>Aim of the present thesis was to assess a rapid and reliable method for the identification and AFST of yeast from positive BC bottles. One hundred and twenty four positive BC collected at the SD Universitaria di Microbiologia of Pisa University Hospital were analysed. For each patient, only the first positive BC that resulted monomicrobial for yeast after Gram staining was included in this study. An aliquot of the pellet of properly treated blood samples was laid on a MALDI-TOF mass spectrometer (MS) target plate and subjected to identification. Next, the pellet was used for assessing the AFST. Identification and AFST results by the rapid method were compared with those obtained by MALDI-TOF and AFST on isolated colonies. <br>The identification results obtained with the rapid method were concordant with those obtained with the conventional method for 107 of 124 (86,3%) BC. Yeast were identified with scores ranging from 1.300 ≤ 1.699 for 41 (33,1%), 1.700 ≤ 1.899 for 43 (33,9%) and ≥ 1.900 for 25 (20,2%) by the rapid method. <br>Rapid AFST gave 100% concordant results with those obtained from yeast isolated on solid media. For only 25,8% of the isolates, a non-significant one two-fold dilution difference was observed.<br>In summary, the rapid method herein described provides accurate and reliable results for the identification and evaluation of the antifungal susceptibility profiles of yeast from positive BC, thus potentially improving the management of patients with invasive yeast infections and rationalizing antifungal drug use.<br><br>
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