Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been suggested as a reliable method for bacterial identification from cultures. Direct analysis of clinical samples might increase the usefulness of this method, shortening the time for microorganism identification. We compared conventional methods for the diagnosis of urinary tract infections (UTIs) and identification of the urinary tract pathogens (automated screening, plate cultures, and identification based on biochemical characteristics) and a fast method based on conventional screening and MALDI-TOF MS. For this latter method, 4 ml of urine was centrifuged at a low-revolution setting (2,000 ؋ g) to remove leukocytes and then at high revolutions (15,500 ؋ g) to collect bacteria. The pellet was washed and then applied directly to the MALDI-TOF MS plate. Two hundred sixty urine samples, detected as positive by the screening device (UF-1000i), were processed by culture and MALDI-TOF MS. Twenty samples were positive in the screening device but negative in culture, and all of them were also negative by MALDI-TOF MS. Two-hundred thirty-five samples displayed significant growth of a single morphological type in culture. Two-hundred twenty of them showed bacterial growth of >10 5 CFU/ml. Microorganism identifications in this group were coincident at the species level in 202 cases (91.8%) and at the genus level in 204 cases (92.7%). The most frequent microorganism was Escherichia coli (173 isolates). MALDI-TOF MS identified this microorganism directly from the urine sample in 163 cases (94.2%).Our results show that MALDI-TOF MS allows bacterial identification directly from infected urine in a short time, with high accuracy, and especially when Gram-negative bacteria with high bacterial counts are involved.Urinary tract infections (UTIs) are among the most common human bacterial infections. More than 80% of uncomplicated UTIs are caused by Escherichia coli (9). Other common uropathogens include Staphylococcus saprophyticus in uncomplicated UTIs and Gram-negative rods (enterobacteria other than E. coli or Pseudomonas aeruginosa) and Gram-positive cocci in complicated UTIs (9). UTIs affect an estimated 1 out of 3 women before the age of 24 (7). Up to 40 to 50% of the female population will develop a symptomatic UTI at some time during their life, and about 33% of women with acute uncomplicated UTIs have frequent recurrences (7).Several tests are available for screening patients for UTIs, including urine dipstick testing, urinalysis, Gram staining, and urine culture. Urine culture is the "gold standard" for defining the diagnosis of UTIs, because it allows the quantification and identification of the uropathogenic species. However, this method is time-consuming and expensive. Up to 70% of urine cultures are negative, with high costs for unnecessary testing (4). Thus, automated analyzers for UTI screening to rapidly identify negative samples that can be reported promptly to clinicians are now widely used. Samples positive in t...

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) allows a fast and reliable bacterial identification from culture plates. Direct analysis of clinical samples may increase its usefulness in samples in which a fast identification of microorganisms can guide empirical treatment, such as blood cultures (BC). Three hundred and thirty BC, reported as positive by the automated BC incubation device, were processed by conventional methods for BC processing, and by a fast method based on direct MALDI-TOF MS. Three hundred and eighteen of them yield growth on culture plates, and 12 were false positive. The MALDI-TOF MS-based method reported that no peaks were found, or the absence of a reliable identification profile, in all these false positive BC. No mixed cultures were found. Among these 318 BC, we isolated 61 Gram-negatives (GN), 239 Gram-positives (GP) and 18 fungi. Microorganism identifications in GN were coincident with conventional identification, at the species level, in 83.3% of BC and, at the genus level, in 96.6%. In GP, identifications were coincident with conventional identification in 31.8% of BC at the species level, and in 64.8% at the genus level. Fungaemia was not reliably detected by MALDI-TOF. In 18 BC positive for Candida species (eight C. albicans, nine C. parapsilosis and one C. tropicalis), no microorganisms were identified at the species level, and only one (5.6%) was detected at the genus level. The results of the present study show that this fast, MALDI-TOF MS-based method allows bacterial identification directly from presumptively positive BC in a short time (<30 min), with a high accuracy, especially when GN bacteria are involved.

Matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) is a fast and reliable technology for the identification of microorganisms with proteomics approaches. Here, we compare an intact cell method and a protein extraction method before application on the MALDI plate for the direct identification of microorganisms in both urine and blood culture samples from clinical microbiology laboratories. The results show that the intact cell method provides excellent results for urine and is a good initial method for blood cultures. The extraction method complements the intact cell method, improving microorganism identification from blood culture. Thus, we consider that MALDI-TOF MS performed directly on urine and blood culture samples, with the protocols that we propose, is a suitable technique for microorganism identification, as compared with the routine methods used in the clinical microbiology laboratory.

BackgroundMALDI-TOF mass spectrometry (MS) is a reliable method for bacteria identification. Some databases used for this purpose lack reference profiles for Brucella species, which is still an important pathogen in wide areas around the world. We report the creation of profiles for MALDI-TOF Biotyper 2.0 database (Bruker Daltonics, Germany) and their usefulness for identifying brucellae from culture plates and blood cultures.Methodology/Principal FindingsWe created MALDI Biotyper 2.0 profiles for type strains belonging to B. melitensis biotypes 1, 2 and 3; B. abortus biotypes 1, 2, 5 and 9; B. suis, B. canis, B ceti and B. pinnipedialis. Then, 131 clinical isolates grown on plate cultures were used in triplicate to check identification. Identification at genus level was always correct, although in most cases the three replicates reported different identification at species level. Simulated blood cultures were performed with type strains belonging to the main human pathogenic species (B. melitensis, B. abortus, B. suis and B. canis), and studied by MALDI-TOF MS in triplicate. Identification at genus level was always correct.Conclusions/SignificanceMALDI-TOF MS is reliable for Brucella identification to the genus level from culture plates and directly from blood culture bottles.

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Family Rhizobiaceae includes fast growing bacteria currently arranged into three genera, Rhizobium, Ensifer and Shinella, that contain pathogenic, symbiotic and saprophytic species. The identification of these species is not possible on the basis of physiological or biochemical traits and should be based on sequencing of several genes. Therefore alternative methods are necessary for rapid and reliable identification of members from family Rhizobiaceae. In this work we evaluated the suitability of Matrix-Assisted Laser Desorption Ionization-Time-of-Flight Mass Spectrometry (MALDI-TOF MS) for this purpose. Firstly, we evaluated the capability of this methodology to differentiate among species of family Rhizobiaceae including those closely related and then we extended the database of MALDI Biotyper 2.0 including the type strains of 56 species from genera Rhizobium, Ensifer and Shinella. Secondly, we evaluated the identification potential of this methodology by using several strains isolated from different sources previously identified on the basis of their rrs, recA and atpD gene sequences. The 100% of these strains were correctly identified showing that MALDI-TOF MS is an excellent tool for identification of fast growing rhizobia applicable to large populations of isolates in ecological and taxonomic studies.

Several components of milk fat globule membranes (MFGMs) have been reported to display beneficial health properties and some of them have been implicated in the defense of newborns against pathogens. These observations prompted us to determine the glycosphingolipid content of MFGMs and their interaction with pathogens. A comparative study with whole milk components was also carried out. Milk fat globules and MFGMs were isolated from milk. Gangliosides and neutral glycosphingolipids were obtained from MFGMs and whole milk and their fatty acid contents were determined by gas chromatography-mass spectrometry (GC-MS). MFGMs and whole milk showed similar ganglioside and neutral glycosphingolipid contents, with whole milk having more GM3 and glucosylceramide and less GD3, O-acetyl GD3, O-acetyl GT3, and lactosylceramide. The fatty acid content of gangliosides from both sources showed a similar composition. However, the neutral glycosphingolipid fatty acid content seemed to be quite different. Whole milk had fewer very-long-chain fatty acids (18.1% vs. 46.4% in MFGMs) and more medium-chain and unsaturated C18:1 and C18:2 fatty acids. Milk fat globules, MFGMs, lactosylceramide, and gangliosides GM3 and GD3 were observed to bind enterotoxigenic Escherichia coli strains. Furthermore, bacterial hemagglutination was inhibited by MFGMs and glycosphingolipids.

We pretreated with SDS 71 urine samples with bacterial counts of >10 5 CFU/ml and matrix-assisted laser desorption ionization-time of flight (MALDI-TOF) identification scores of <2, in order to minimize failure rates. Identification improved in 46.5% of samples, remained unchanged in 49.3%, and worsened in 4.2%. The improvement was more evident for Gram-negative (54.3%) than for Gram-positive (32%) bacteria. Urinary tract infections (UTIs) are among the most common human bacterial infections (1).Tests developed for UTI screening include urine dipstick testing, urinalysis, and Gram staining. The urine culture remains the "gold standard," but the use of this method, without any previous screening procedure, is time-consuming and expensive, because of the high cost of unnecessary testing of negative samples (2).Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) has been shown as a fast and reliable method for bacterial identification both from culture plates (3,4) and from blood cultures vials (5, 6), and also from some other samples, such as infected urine, especially when Gram-negative bacteria with high bacteria counts are involved (7).We described recently a procedure for processing urine samples (7) which begins with a centrifugation step (2,000 ϫ g for 30 s) to remove leukocytes. Thus, the 7 to 8% of identification failures reported in culture-positive samples might be associated with the removal of intraleukocytic microorganisms in these first steps of processing. We have developed a further study, including a sample pretreatment with SDS, because this compound can lysate cells and then release microorganisms, thereby increasing method sensitivity.Processing of urine samples. We analyzed 71 urine clinical samples with bacterial counts of Ն10 5 CFU/ml on blood agar after 18 h of incubation in an aerobic atmosphere at 37°C and with a score of Ͻ2 in MALDI-TOF MS identification. Samples showing mixed cultures were discarded.Routine urine samples were initially processed for direct microorganism identification with MALDI-TOF MS, according to previously reported methods (7). An aliquot of each sample was stored at 4°C. When the bacterial count was Ն10 5 CFU/ml and the MALDI-TOF MS identification score value was Ͻ2, the stored aliquot was spread again on blood agar for checking that bacterial count had not changed significantly (count modifications of Ͻ5% were considered acceptable) and processed again for MALDI-TOF MS identification, after SDS pretreatment, always before 24 h of storage. Comparison between improvement rates in Gram-positive and Gram-negative bacteria was performed by using the Fisher exact test with the mid-P method. Statistical significance was considered when the P value was Ͻ0.01. Differential procedure. (i) MALDI-TOF MS.Samples were processed as described before (7). Briefly, urine (3 ml) was centrifuged at 2,000 ϫ g for 30 s to remove leukocytes. The supernatant was centrifuged at 15,500 ϫ g for 5 min to collect bacteria. The pellet was washed once wit...