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Browsing by Author "Castro, Ana Isabel Rodrigues Pereira de"

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  • Characterisation of staphylococcus aureus circulating in Portugal
    Publication . Castro, Ana Isabel Rodrigues Pereira de; Teixeira, Paula Cristina Maia; Silva, Joana Gabriela Laranjeira da
    Staphylococcus aureus is a pathogen responsible for skin infections and invasive diseases such as meningitis or pulmonary infection and staphylococcal food poisoning (SFP). The main goal of this study was to increase knowledge on S. aureus circulating in Portugal mainly concerning their virulence characteristics and antimicrobial resistance. According to EFSA-ECDC, Portugal is considered to have one of the highest levels of methicillin-resistant S. aureus (MRSA) from bacteraemia in Europe. The frequency of occurrence of S. aureus from different origins was determined. Swab samples were collected from hands and nose of health care professionals and food handlers - noses and hands are niches where S. aureus are likely to be present in humans - and particularly noses of children (3 to 6 years). Presence of S. aureus in food samples was also determined. Collected isolates were further characterized phenotypically and genomically. Nasal carriage of S. aureus was higher in children (48.6%) compared to health care professionals (39.6%) and food handlers (19.8%). The occurrence of S. aureus on the hands of health care professionals and food handlers was 8.9% and 11.1%, respectively. Globally, higher S. aureus occurrence rates were obtained for nasal carriage. The first case of Methicillin-Resistant Staphylococcus aureus (MRSA) was reported in 1961. Since then, it has been considered the leading cause of nosocomial infections, responsible for causing serious morbidity and mortality rates, worldwide. Globally, the occurrence of MRSA strains was higher in hospital health care professionals; no MRSA strains were detected in food handlers, children presented a carriage of 9.7% of MRSA and low occurrence rates were detected in the analysed food samples (between 0.68 and 5.5 %). Other virulence factors have been reported for S. aureus strains including antibiotic resistance and presence of enterotoxins, Panton-Valentine Leukocidin (PVL), haemolysins, exfoliative toxins and numerous factors involved in invasion of host cells among others. In the present study, resistance to oxacillin, penicillin and ampicillin and to antibiotics of classes other than betalactams, namely ciprofloxacin, gentamicin, rifampicinn, vancomycin, tetracycline, erythromycin, nitrofurantoin and chloramphenicol was investigated. As expected, high levels of resistance to ß-lactams were observed. Tested strains showed low resistance rates to gentamicin, chloramphenicol and rifampicin. Regardless of the source of isolates, resistance to erythromycin was evident. Enterotoxin genes sea - sej and tst were evaluated by multiplex PCR. Although sea is considered the most prevalent enterotoxin gene reported all over the world, in the present study this was not verified. tst gene was detected in children, hospital health care professionals and food handlers. PVL genes were analysed in all the MRSA strains collected from various origins, but only one food strain showed the presence of these genes. Typing by SCCmec has been performed and revealed the presence of type IV and V. SCCmec type IV is associated worldwide with PVL positive strains, but which was not verified in this study. PFGE typing was performed on S. aureus strains isolated from hands and from nose of the same individual of the health care professionals and food handlers; 60 and 30% of the individuals, respectively, presented the same S. aureus strain on hands and nose.
    2017-02-27Doctoral thesis Open access Show more