K. Papavasileiou

Athens State University, Athens, Alabama, United States

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Publications (9)15.15 Total impact

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    ABSTRACT: PURPOSE: Salmonella enterica enterica encodes a variety of virulence factors. Among them, the type III secretion system (TTSS) encoded in the Salmonella pathogenicity islands (SPIs) is required for induction of proinflammatory responses, invasion of intestinal epithelial cells, induction of cell death in macrophages, and elicitation of diarrhea. The presence of the effector protein genes sopB, sopD, sopE, sopE2, avrA, and sptP of the SPIs was analyzed in 194 S. enterica enterica strains belonging to 19 serovars. METHODS: S. enterica enterica strains were collected from children with gastroenteritis, either hospitalized or attending the outpatient clinic, aged 1-14 years. Nineteen different serotypes were included in the study. Serotyping, biofilm formation determination, and antimicrobial resistance of the planktonic as well as the biofilm forms of the strains have been reported previously. RESULTS: At least one virulence gene was present in all Salmonella isolates. Biofilm formation was statistically independent of any of the six genes. Strains lacking sopE and sopE2 were more resistant to all the antimicrobials. CONCLUSIONS: The association of the virulence genes with the antimicrobial resistance of Salmonella in general has been previously reported and is a matter of further investigation. For the clinical expression of pathogenicity in humans, the contribution of these genes is questionable, as some strains bearing only a single gene (either sptP or avrA) were still capable of causing gastroenteritis.
    Molecular diagnosis & therapy. 06/2013;
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    ABSTRACT: Acute bacterial meningitis is one of the most severe infectious diseases, affecting mainly infants and, secondarily, older children and adolescents. Diagnosis in the early stages is often difficult and despite treatment with appropriate antibiotic therapy, the case fatality rate remains high. In the present study, the incidence of bacterial meningitis was registered in a general pediatric hospital in Athens, Greece, during a 9-year period (2000-2008), and the use of molecular methods in the diagnosis of bacterial meningitis versus the conventional cultural methods was evaluated. The impact of vaccination against meningitis-causing bacteria on the incidence of bacterial meningitis was also assessed. From a total of 1833 children hospitalized with suspected clinical symptoms and signs of meningitis, all cerebrospinal fluid (CSF) and blood samples were analyzed by white blood cell (WBC) count, measurement of glucose, protein, and C-reactive protein (CRP) levels, as well as by conventional bacteriologic culture methods. If samples showed altered CSF markers that were consistent with meningitis in general, they were further investigated by PCR for bacterial pathogens. Of the 1833 patients, 289 (15.76%) were found to be positive for meningitis after CSF examination, based on white blood cell count and differentiation, glucose, protein, and CRP. Fifty-six of the 289 (19.37%) had confirmed bacterial meningitis, as diagnosed by either culture and/or PCR. Of these 56 cases, 44 (78.6%) were detected only by PCR, and 12 cases (21.4%) were confirmed by PCR and culture. The predominant microorganism was Neisseria meningitidis serogroup B (n = 40; 71.4%), followed by Streptococcus pneumoniae not typed [NT] (n = 7; 12.5%), Streptococcus spp. (n =4; 7.1%), Haemophilus influenzae NT (n = 2; 3.6%), and S. pneumoniae serotype 3, Streptococcus group B, and S. pneumoniae serotype 18C (each n = 1; 1.8%). In Greece, according to data from the National Meningitis Reference Laboratory, vaccination against N. meningitidis serogroup C since 2001 led to a 10-fold decrease in the incidence of meningitis cases, vaccination against S. pneumoniae serotypes included in the heptavalent conjugate vaccine since 2005 led to a 3.4-fold incidence decrease, and vaccination against H. influenzae type b since 1992 led almost to an absence of cases. In the population of the present study, none of the cases were caused by the above-mentioned vaccine pathogens, except for one S. pneumoniae serotype 18C case with no history of past vaccination. The introduction of vaccination against meningitis-causing bacteria has drastically decreased the emergence of the infection. The improved molecular amplification assays proved to be superior to conventional bacteriologic methods and should be introduced into routine diagnosis, as well as the epidemiologic surveillance of bacterial meningitis.
    Molecular Diagnosis & Therapy 03/2011; 15(2):109-13. · 2.59 Impact Factor
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    ABSTRACT: In the present study, 194 Salmonella enterica strains, isolated from infected children and belonging to various serotypes, were investigated for their ability to form biofilms and the biofilm forms of the isolated strains were compared to their corresponding planktonic forms with respect to the antimicrobial susceptibility. For the biofilm-forming strains, the minimum inhibitory concentration for bacterial regrowth (MICBR) from the biofilm of nine clinically applicable antimicrobial agents was determined, and the results were compared to the respective MIC values of the planktonic forms. One hundred and nine S. enterica strains out of 194 (56%) belonging to 13 serotypes were biofilm-forming. The biofilm forms showed increased antimicrobial resistance compared to the planktonic bacteria. The highest resistance rates of the biofilm bacteria were observed with respect to gentamicin (89.9%) and ampicillin (84.4%), and the lowest rates with respect to ciprofloxacin and moxifloxacin (2.8% for both). A remarkable shift of the MICBR(50) and MICBR(90) toward resistance was observed in the biofilm forms as compared to the respective planktonic forms. The development of new consensus methods for the determination of the antimicrobial susceptibility of biofilm forms seems to be a major research challenge. Further studies are required in order to elucidate the biofilm antimicrobial resistance mechanisms of the bacterial biofilms and their contribution to therapeutic failure in infections with in vitro susceptible bacteria.
    European Journal of Clinical Microbiology 11/2010; 29(11):1401-5. · 3.02 Impact Factor
  • International Journal of Antimicrobial Agents 11/2008; 33(2):183-4. · 4.42 Impact Factor
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    ABSTRACT: A total of 170 Campylobacter jejuni strains isolated from the stool of children with clinical gastroenteritis, aged from 3 months to 14 years, were collected during a two-year period (2004-2005). From the 170 strains 30% were resistant to ciprofloxacin (MIC > or = 4 microg/ml), 55% to tetracycline (MIC > 8 microg/ml), 13% to clindamycin (MIC > or = 8 microg/ml), 4% to ampicillin (MIC > 16 microg/ml), 6% to erythromycin (MIC > or = 8 microg/ml), 4% to coamoxiclav (MIC > or = 16/8 microg/ml) and 0% to gentamicin. Compared to previous reports from Greece, the antimicrobial resistance rates to erythromycin, ampicillin and coamoxiclav remain low, while they are still high for tetracycline and ciprofloxacin. Considering similar reports from many other countries and the high incidence of Campylobacter gastroenteritis worldwide, the value of ciprofloxacin as a first choice drug in the empiric treatment of the infection is questionable.
    European Journal of Epidemiology 01/2007; 22(1):77-8. · 5.12 Impact Factor
  • International Journal of Antimicrobial Agents - INT J ANTIMICROBIAL AGENTS. 01/2007; 29.
  • International Journal of Antimicrobial Agents - INT J ANTIMICROBIAL AGENTS. 01/2007; 29.
  • International Journal of Antimicrobial Agents - INT J ANTIMICROBIAL AGENTS. 01/2007; 29.
  • International Journal of Antimicrobial Agents - INT J ANTIMICROBIAL AGENTS. 01/2007; 29.