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| Author(s): |
Juliana Regina Barreiro
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | Pirassununga. |
| Institution: | Universidade de São Paulo (USP). Faculdade de Medicina Veterinária e Zootecnia (FMVZ/SBD) |
| Defense date: | 2011-01-19 |
| Examining board members: |
Marcos Veiga dos Santos;
Felipe Perecin;
Marco Aurélio de Felício Porcionato
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| Advisor: | Marcos Veiga dos Santos |
| Abstract | |
Rapid and efficient diagnosis of subclinical mastitis is important to reduce the persistence of the disease and its losses. This study aimed to evaluate the technique of mass spectrometry (MS) and desorption ionization by matrix assisted laser time-offlight (MALDI-TOF) for identification of bacteria causing bovine subclinical mastitis by two methods: 1) from bacteria isolated by microbiological culture, 2) from bacteria recovered directly from milk, to eliminate completely the need for microbiological culture for identification of pathogens. The study consisted of two experiments (1 and 2).In experiment 1, 33 milk samples from Gir and Holstein animals collected in four dairy farms were used for microbiological identification and MALDI-TOF MS. The samples with different results were confirmed by sequencing the 16S rRNA. These samples were identified by microbiological culture as Staphylococcus aureus (n = 13), Streptococcus agalactiae (n = 10) and Staphylococcus coagulase negative (SCN) (n = 10). For all strains of Streptococcus agalactiae, similar results were observed for microbiological identification and MALDI-TOF MS. From 13 isolates of Staphylococcus aureus, 11 were also identified by MALDI-TOF, one isolate was identified as Staphylococcus haemolyticus by 16S rRNA sequencing , and the other discrepant sample was charactezided a mixed culture of Staphylococcus aureus and Enterococcus faecalis. Regarding the SCN samples, all samples of this group were identified by MALDI-TOF at gender level (S. simulans, S. epidermidis, S. haemolyticus, S. Chromogens and S. aureus coagulase negative). In experiment 2, we evaluated the method of recovery of bacteria present in milk and their identification by MALDI-TOF MS using experimental method of contamination of milk with Escherichia coli, Enterococcus faecalis and Staphylococcus aureus. The identification of pathogens recovered directly from milk was possible when the concentration of E. faecalis and S. aureus was 106 ufc/mL and 107 ufc/mL for E.coli. We conclude that the use of MALDI-TOF MS can accelerate the identification of pathogens causing bovine subclinical mastitis may contribute to the adoption of control measures and appropriate treatment. (AU) | |
| FAPESP's process: | 09/12751-5 - Fingerprinting for mass spectrometry for diagnosis of pathogens in mastitis |
| Grantee: | Juliana Regina Barreiro |
| Support Opportunities: | Scholarships in Brazil - Master |