title: Evaluation of matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) for identification and clustering of Neisseria gonorrhoeae.
abstract: BACKGROUND
  The sexually transmitted infection gonorrhea remains a public health concern for becoming resistant to drug treatments available. The purpose of this study was to evaluate the usefulness of the matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) to identify and cluster Neisseria gonorrhoeae. From a current monitoring in Italy, as part of the European Gonococcal Antimicrobial Surveillance Programme (EURO-GASP), 93 gonococci collected from 2007 to 2012 susceptible (44 isolates) and resistant (49 isolates) to cefixime were selected. Minimum Inhibitory Concentration (MIC) values for cefixime was assessed by Etest carried out in agreement with the manufacturer's instructions and interpreted referring to European Committee on Antimicrobial Susceptibility testing (EUCAST) clinical breakpoints criteria. Data obtained by N. gonorrhoeae multiantigen sequence typing (NG-MAST) and the dendrogram based on the concatenation of porB and tbpB genes were evaluated. MALDI-TOF MS, to reconfirm gonorrhea identification, analyzed single colonies from freshly grown isolates and applied directly on a ground-steel MALDI target plate. For the MALDI-TOF dendrogram cluster analysis, MSPs (Main Spectrum Profile) from each isolate were created acquiring 5000 shots from 10 technical replicates obtained from bacteria extraction.
  
  
  RESULTS
  Molecular typing by NG-MAST showed 28 sequence types (STs); G1407 was the predominant accounting for 75 gonococci. All the 93 gonococci, except one, were correctly identified at species level by MALDI-TOF MS and G1407 isolates were divided into two clusters.
  
  
  CONCLUSIONS
  MALDI-TOF MS for a real-time detection and cluster analysis of gonorrhea is a promising tool for surveillance purposes. Moreover, additional studies are required to collect more data on the performance of MALDI-TOF MS for gonococci.
authors.affiliation: Departmentof Infectious, Parasitic & Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, Italy. anna.carannante@iss.it.
authors.forename: Anna
authors.initials: A
authors.lastname: Carannante
authors.affiliation: Istituto di Microbiologia, Università Cattolica del Sacro Cuore, Rome, Italy. elena.decarolis@unicatt.it.
authors.forename: Elena
authors.initials: E
authors.lastname: De Carolis
authors.affiliation: Departmentof Infectious, Parasitic & Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, Italy. paola.vacca@iss.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Vacca
authors.affiliation: Istituto di Microbiologia, Università Cattolica del Sacro Cuore, Rome, Italy. antonella.vella05@gmail.com.
authors.forename: Antonietta
authors.initials: A
authors.lastname: Vella
authors.affiliation: Unit of Clinical Microbiology, CRREM Laboratory, St. Orsola-Malpighi, University Hospital, Bologna, Italy. cate.vocale@gmail.com.
authors.forename: Caterina
authors.initials: C
authors.lastname: Vocale
authors.affiliation: Dipartimento di Medicina Molecolare e Traslazionale, Sezione di Microbiologia, University of Brescia, Brescia, Italy. maria.defrancesco@unibs.it.
authors.forename: Maria Antonia
authors.initials: MA
authors.lastname: De Francesco
authors.affiliation: Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy. m.cusini@policlinico.mi.it.
authors.forename: Marco
authors.initials: M
authors.lastname: Cusini
authors.affiliation: Microbiology and Virology Laboratory, Infectious Diseases, Amedeo di Savoia Hospital, Turin, Italy. simodelre@yahoo.it.
authors.forename: Simonetta
authors.initials: S
authors.lastname: Del Re
authors.affiliation: MD, Dip-GUM. STI Clinic, Department of Infectious Diseases, Amedeo di Savoia Hospital, Turin, Italy. ivano.dalconte@aslto2.piemonte.it.
authors.forename: Ivano
authors.initials: I
authors.lastname: Dal Conte
authors.affiliation: San Gallicano Dermatologic Institute-IRCSS-Rome, Rome, Italy. cristaudo@ifo.it.
authors.forename: Antonio
authors.initials: A
authors.lastname: Cristaudo
authors.affiliation: Microbiology and Virology Laboratory, Santa Chiara Hospital, Trento, Italy. patrizia.ober@apss.tn.it.
authors.forename: Patrizia
authors.initials: P
authors.lastname: Ober
authors.affiliation: Istituto di Microbiologia, Università Cattolica del Sacro Cuore, Rome, Italy. msanguinetti@rm.unicatt.it.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Sanguinetti
authors.affiliation: Departmentof Infectious, Parasitic & Immune-mediated Diseases, Istituto Superiore di Sanità, Rome, Italy. paola.stefanelli@iss.it.
authors.forename: Paola
authors.initials: P
authors.lastname: Stefanelli
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology; D001431:Bacteriological Techniques / Q000379:methods*; D020682:Cefixime / Q000494:pharmacology; D016000:Cluster Analysis; D005838:Genotype; D006801:Humans; D007558:Italy; D008826:Microbial Sensitivity Tests; D058885:Multilocus Sequence Typing; D009344:Neisseria gonorrhoeae / Q000737:chemistry / Q000145:classification* / Q000187:drug effects / Q000302:isolation & purification*; D010641:Phenotype; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization / Q000379:methods*
chemical_list: D000900:Anti-Bacterial Agents; D020682:Cefixime