P E Varaldo

Università Politecnica delle Marche, Ancona, The Marches, Italy

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Publications (134)683.3 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: The activity of levofloxacin and ulifloxacin on biofilm formation and persistence was evaluated on microorganisms isolated from urinary double-J-stents. We analyzed 51 bacterial strains and their susceptibility to different antimicrobial classes was determined. We evaluated the bacterial ability to form biofilm and the effects of different concentrations of levofloxacin and ulifloxacin on bacterial adhesion and biofilm persistence. Most of the strains were biofilm producers with no relevant difference in biofilm production at 24 or 48 hours. The fluoroquinolones were able to prevent biofilm formation, but not to eradicate the preformed biofilm. On the basis of our data we advise that antibiotic prophylaxis with fluoroquinolones may be most helpful if given at the time of stent insertion and at high dosage.
    Journal of chemotherapy (Florence, Italy) 05/2008; 20(2):195-201. · 0.83 Impact Factor
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    Antimicrobial Agents and Chemotherapy 01/2008; 51(12):4535; author reply 4535-6. · 4.57 Impact Factor
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    Antimicrobial Agents and Chemotherapy 09/2007; 51(8):3042-3. · 4.57 Impact Factor
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    ABSTRACT: During 2000-2002, 20 clinical microbiology centres collected 1623 Streptococcus pneumoniae isolates. Susceptibility to penicillin, amoxicillin, amoxicillin/clavulanic acid, cefaclor, cefuroxime, cefotaxime, clarithromycin, ciprofloxacin, levofloxacin, rifampicin and teicoplanin was determined locally by the Etest and/or by the microdilution method by three co-ordinating centres. Total resistance to penicillin increased from 15.2% to 16.1% and macrolide resistance increased from 37.9% to 43.7%. Overall, the most effective drugs (>99% susceptible strains) were amoxicillin, amoxicillin/clavulanic acid, levofloxacin and rifampicin. The most frequent serotypes were: 23F (15.8%), 3 (10.8%) 14 (9.1%), 19F (9.1%), 6B (7.2%), 19A (6.9%) and 6A (4.8%). In conclusion, penicillin and macrolide resistance is increasing in Italy, whilst fluoroquinolone currently remains active. The most common serotypes circulating are included in the heptavalent conjugate vaccine, with the exception of type 3.
    International Journal of Antimicrobial Agents 08/2005; 26(2):138-45. · 4.42 Impact Factor
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    ABSTRACT: Prulifloxacin, a new fluoroquinolone, is a prodrug whose active compound, ulifloxacin, is derived from its transformation after oral administration and intestinal absorption. Based on early pharmacokinetic and pharmacodynamic data, the following MIC breakpoints have tentatively been proposed: < or = 1 microg/ml, susceptible; 2 microg/ml, intermediate; and > or = 4 microg/ml, resistant. In this report, ulifloxacin MIC vs. zone diameter scattergrams and discrepancy rates were analyzed in 461 freshly isolated clinical strains (237 Enterobacteriaceae, 101 nonfermenters, and 123 Gram-positive bacteria). In agreement with the guidelines of the National Committee for Clinical Laboratory Standards, a modification of the error rate-bounded method was used to select disk diffusion test breakpoints. The following zone diameter breakpoints were chosen and are proposed herein for the interpretation of ulifloxacin disk (5 microg) test results: < or = 15 and > or = 19 mm for Enterobacteriaceae, < or = 16 and > or = 20 mm for nonfermenters, and < or = 14 and > or = 18 mm for Gram-positive bacteria. By applying these breakpoint values, no very major errors were detected, while major and minor errors were largely below the accepted discrepancy rates.
    Journal of chemotherapy (Florence, Italy) 05/2005; 17(2):138-42. · 0.83 Impact Factor
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    S Stefani, P E Varaldo
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    ABSTRACT: Methicillin-resistant staphylococci are mostly resistant not only to all beta-lactams but also to a wide range of other antibiotics, and have emerged as major nosocomial pathogens during the past two decades. Considerable variations in the prevalence of methicillin-resistant Staphylococcus aureus (MRSA) exist between institutions and between geographic areas. In Europe, in general, a north-south gradient is observed, MRSA strains being rare in Scandinavian hospitals (<2%) and far more prevalent in Mediterranean hospitals (>40%). Whether low or high, the rates of MRSA prevalence in European countries have remained approximately the same during the last decade. Recent findings suggest that MRSA might also be emerging as a community-acquired pathogen. The first stage in the emergence of MRSA is its acquisition by methicillin-susceptible S. aureus, and the integration into its chromosome, of the mecA gene, which, together with the other mec genes, is carried on a mobile genetic element, the staphylococcal chromosomal cassette mec (SCCmec). The origin of SCCmec elements as well as the mechanisms of their acquisition remain unknown. Molecular epidemiology studies using different techniques clearly indicate that the massive geographic spread of MRSA results from the dissemination of relatively few highly epidemic clones. Five major lineages (the so-called Iberian, Brazilian, Hungarian, New York/Japan and pediatric pandemic MRSA clones) have been defined. In Europe, the Iberian clone has been reported in several countries; the Brazilian, pediatric and Hungarian clones have also been detected, but less frequently. A unique Italian clone is predominant in Italy. As with S. aureus, coagulase-negative staphylococci (CNS) represent a serious concern in hospital-acquired infections. Despite marked geographic variations, in some areas of Europe high proportions (60-70%) of CNS are methicillin resistant. The formation of biofilm is a key virulence factor of S. epidermidis, the prominent CNS pathogen, which is the most common cause of bacteremia in device-related infections. Another emerging nosocomial pathogen, S. hemolyticus, is characterized by a tendency to develop multiple antibiotic resistances, with a unique predisposition to glycopeptide resistance.
    Clinical Microbiology and Infection 12/2003; 9(12):1179-86. · 4.58 Impact Factor
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    ABSTRACT: Antibodies are in several instances a reliable marker indicating vigorous immune response against infectious agents and in several viral diseases presence in the blood of specific anti-viral antibodies indicates an effective protection. However, this is not always true. For example, in the case of hepatitis C virus (HCV) an important human pathogen considered the causative agent of the nonA- nonB hepatitis, in spite of an intense antibody response there is no protection against a new infection and in the majority of infected individuals the virus overcomes host defences establishing a persistent infection. Here we describe how the dissection of the humoral immune response against HCV glycoprotein E2 of infected patients was useful for a better comprehension of the virus-host interplay. Cross-reactive antibodies directed against E2 are produced by the HCV-infected patient, but not all of them are protective, and some could even result to be detrimental for the patient. The cross-reactive anti-HCV/E2 humoral antibody response is complex and not necessarily completely beneficial to the host.
    Journal of biological regulators and homeostatic agents 01/2003; 17(2):125-7. · 5.18 Impact Factor
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    ABSTRACT: In mating experiments, the erythromycin resistance methylase gene erm(A) was successfully transferred from erm(A)-positive clinical isolates of Streptococcus pyogenes to macrolide-susceptible recipients of S. pyogenes, Enterococcus faecalis and Listeria innocua. Compared with the SmaI macrorestriction pattern of the S. pyogenes recipient, the patterns of S. pyogenes transconjugants shared the lack of a fragment and the appearance of a new, larger fragment. This is the first experimental evidence that the erm(A) gene can be transferred from erythromycin-resistant S. pyogenes to macrolide-susceptible S. pyogenes as well as to other Gram-positive recipients.
    Journal of Antimicrobial Chemotherapy 09/2002; 50(2):249-52. · 5.34 Impact Factor
  • Journal of Hepatology - J HEPATOL. 01/2002; 36:221-221.
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    ABSTRACT: Six putative novel human papillomavirus (HPV) types were detected by using general primers for a conserved L1 HPV region in patients examined in gynecologic centers. One of the isolates, detected in samples from 4 patients with koilocytic atypia at cervical cytology (3 of whom were also infected with human immunodeficiency virus type 1), was completely sequenced, identified as a new HPV genotype, and designated candidate HPV87 (candHPV87) by the Reference Center for Human Papillomavirus. candHPV87 shows the classic HPV genome organization and the absence of a functional E5 coding region. Phylogenetic analysis documented that the candHPV87 genome clusters within the A3 group of HPVs, together with HPV61, HPV72, HPV83, HPV84 and candHPV86, which have been completely sequenced, and a number of other putative novel genotypes (two of which are described in this work), which have been partially characterized. To address the growth-enhancing potential of candHPV87, the E6 and E7 putative coding regions were cloned and expressed in tissue cultures. The data indicate that both proteins stimulate cell division in tissue cultures more than those of low-risk HPVs, though not as much as those of HPV16. Taken together, the clinical, molecular, and biological data suggest that the novel papillomavirus characterized in the present study is a low- to intermediate-risk HPV.
    Journal of Virology 01/2002; 75(23):11913-9. · 5.08 Impact Factor
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    M P Montanari, M Mingoia, P E Varaldo
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    ABSTRACT: AF 3013, the active metabolite of prulifloxacin, was tested to determine its inhibitory and bactericidal activities against 396 nosocomial and 258 community Italian isolates. Compared with that of ciprofloxacin, its activity (assessed in MIC and minimal bactericidal concentration tests) was generally similar or greater against gram-positive bacteria and greater against gram-negative bacteria. In time-kill assays using selected isolates, its bactericidal activity was comparable to that of ciprofloxacin.
    Antimicrobial Agents and Chemotherapy 01/2002; 45(12):3616-22. · 4.57 Impact Factor
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    ABSTRACT: In a 1-year multicenter study the microbial colonization of 1154 central venous catheters (CVCs) was investigated. Catheters explanted either from immunocompromised or immunocompetent patients were collected and analyzed by five clinical microbiology laboratories located in Ancona, Aviano, Catania, Pavia and Rome, Italy. A further aim was to investigate, by scanning electron microscopy, the features of currently used catheters, both new and explanted from patients, analyzing their surface quality, the influence of the host protein biofilm on their microbial colonization, the modifications caused by their permanence in the body and the relationship between these factors and the occurrence of infections.
    Journal of chemotherapy (Florence, Italy) 12/2001; 13 Spec No 1(1):251-62. · 0.83 Impact Factor
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    ABSTRACT: Clinical and experimental evidence indicates that the hepatitis C virus (HCV) E2 glycoprotein (HCV/E2) is the most promising candidate for the development of an effective anti-HCV vaccine. Identification of the human epitopes that are conserved among isolates and are able to elicit protective antibodies would constitute a significant step forward. This work describes the mapping of the B-cell epitopes present on the surface of HCV/E2, as recognized by the immune system during infection, by the analysis of the reciprocal interactions of a panel of human recombinant Fabs derived from an HCV-infected patient. Three unrelated epitopes recognized by antibodies with no neutralization-of-binding (NOB) activity were identified; a fourth, major epitope was defined as a clustering of minor epitopes recognized by Fabs endowed with strong NOB activity.
    Journal of Virology 11/2001; 75(20):9986-90. · 5.08 Impact Factor
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    ABSTRACT: An increase in erythromycin resistance rates among group A streptococci has been reported in some European countries. These bacteria, long thought to be extracellular pathogens, can be efficiently internalised by, and survive within, human cells of respiratory-tract origin. Macrolide antibiotics enter eukaryotic cells, whereas beta-lactams are essentially confined to the extracellular fluid. A protein encoded by gene prtF1 is required for efficient entry of group A streptococci into epithelial cells. We investigated isolates of group A streptococci from children with pharyngitis in Italy for the presence of prtF1 and cell-invasion efficiency. We investigated 74 erythromycin-resistant and 52 erythromycin-susceptible isolates collected throughout Italy in 1997-98 from children with pharyngitis. Erythromycin-resistance phenotypes (constitutive, inducible, and M) were assessed by the triple-disc test and resistance determinants (ermB, ermTR, and mefA) by PCR. All strains were examined for the presence of prtF1 by PCR and for their ability to enter cultured human respiratory cells. The proportion of prtF1-positive strains was significantly higher among erythromycin-resistant than susceptible strains (66 [89%] vs 11 [21%]; difference 68% [95% CI 52-84]). All erythromycin-resistant strains without prtF1 were of the M phenotype. The proportion of highly cell-invasive isolates (invasion efficiency >10%) was significantly higher among erythromycin-resistant than among susceptible strains (59 [80%] vs five [10%]; difference 70% [57-83]). The unsuspected association between erythromycin resistance and cell invasiveness in group A streptococci raises serious concern. Strains combining erythromycin resistance and ability to enter human respiratory-tract cells may be able to escape both beta-lactams by virtue of intracellular location and macrolides by virtue of resistance.
    The Lancet 08/2001; 358(9275):30-3. · 39.21 Impact Factor
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    ABSTRACT: Two Enterococcus gallinarum isolates distinguished by different colony sizes were recovered from the same blood culture from a woman with acute myeloid leukemia. They were designated E31 (the one with larger colonies) and E32 (the one with smaller colonies). Both isolates were glycopeptide resistant, but the MICs of vancomycin and teicoplanin for E31 (32 and 2 microg/ml, respectively, consistent with the VanC phenotype) and E32 (128 and 16 microg/ml, respectively, consistent with the VanA phenotype) were different. E31 and E32 had the same plasmid profile and showed identical pulsed-field gel electrophoresis patterns after digestion of total DNA with NotI and a two-band variation after digestion with SmaI. Polymerase chain reaction experiments showed that both isolates had both the vanC-1 and vanA genes and carried a Tn1546-related transposon lacking orf1, vanY, and vanZ. The absence of these three genes was confirmed by Southern analysis with appropriate probes. Southern hybridization experiments using a vanA probe showed that this atypical Tn1546-related element appeared to be located on the chromosome. In both E31 and E32, the vanA probe hybridized to EcoRV and HindIII fragments larger in size than the hybridizing fragments observed in the VanA prototype strain Enterococcus faecium BM4147, suggesting the lack of the relevant EcoRV and HindIII restriction sites.
    European Journal of Clinical Microbiology 06/2001; 20(5):309-14. · 3.02 Impact Factor
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    ABSTRACT: Laboratory differentiation of erythromycin resistance phenotypes is poorly standardized for pneumococci. In this study, 85 clinical isolates of erythromycin-resistant (MIC > or = 1 microg/ml) Streptococcus pneumoniae were tested for the resistance phenotype by the erythromycin-clindamycin double-disk test (previously used to determine the macrolide resistance phenotype in Streptococcus pyogenes strains) and by MIC induction tests, i.e., by determining the MICs of macrolide antibiotics without and with pre-exposure to 0.05 microg of erythromycin per ml. By the double-disk test, 65 strains, all carrying the erm(AM) determinant, were assigned to the constitutive macrolide, lincosamide, and streptogramin B resistance (cMLS) phenotype, and the remaining 20, all carrying the mef(E) gene, were assigned to the recently described M phenotype; an inducible MLS resistance (iMLS) phenotype was not found. The lack of inducible resistance to clindamycin was confirmed by determining clindamycin MICs without and with pre-exposure to subinhibitory concentrations of erythromycin. In macrolide MIC and MIC-induction tests, whereas homogeneous susceptibility patterns were observed among the 20 strains assigned to the M phenotype by the double-disk test, two distinct patterns were recognized among the 65 strains assigned to the cMLS phenotype by the same test; one pattern (n = 10; probably that of the true cMLS isolates) was characterized by resistance to rokitamycin also without induction, and the other pattern (n = 55; designated the iMcLS phenotype) was characterized by full or intermediate susceptibility to rokitamycin without induction turning to resistance after induction, with an MIC increase by more than three dilutions. A triple-disk test, set up by adding a rokitamycin disk to the erythromycin and clindamycin disks of the double-disk test, allowed the easy differentiation not only of pneumococci with the M phenotype from those with MLS resistance but also, among the latter, of those of the true cMLS phenotype from those of the iMcLS phenotype. While distinguishing MLS from M resistance in pneumococci is easily and reliably achieved, the differentiation of constitutive from inducible MLS resistance is far more uncertain and is strongly affected by the antibiotic used to test inducibility.
    Journal of Clinical Microbiology 04/2001; 39(4):1311-5. · 4.07 Impact Factor
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    ABSTRACT: Two ketolides, telithromycin and HMR 3004, were evaluated for their in vitro activity against erythromycin-susceptible and -resistant strains of Streptococcus pyogenes and Streptococcus pneumoniae. On the basis of their resistance to macrolide, lincosamide and streptogramin (MLS) antibiotics, erythromycin-resistant test strains were assigned to the constitutive resistance (cMLS) phenotype, the inducible resistance (iMLS) phenotype or the M phenotype. iMLS S. pyogenes strains were further subdivided into the three recently described subtypes iMLS-A, -B and -C. Telithromycin and HMR 3004 were uniformly and highly active against pneumococci (regardless of their susceptibility or resistance to erythromycin and/or penicillin), erythromycin-susceptible S. pyogenes and erythromycin-resistant S. pyogenes strains of the M phenotype (in which resistance is mediated by an efflux system) or iMLS-B or -C phenotype (in which resistance is mediated by a methylase encoded by the ermTR gene). Both ketolides were less active against erythromycin-resistant S. pyogenes strains with the cMLS phenotype or the iMLS-A subtype (where resistance is mediated by a methylase encoded by the ermAM gene), these strains ranging in phenotype from the upper limits of susceptibility to low-level resistant.
    Journal of Antimicrobial Chemotherapy 01/2001; 46(6):905-8. · 5.34 Impact Factor
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    ABSTRACT: High rates of erythromycin resistance among Streptococcus pyogenes strains have been reported in Italy in the last few years. In this study, 370 erythromycin-resistant (MIC, > or = 1 microg/mL) Italian isolates of this species obtained in 1997-1998 from throat swabs from symptomatic patients were typed by analyzing SmaI macrorestriction fragment patterns by pulsed-field gel electrophoresis (PFGE). Among the typable isolates (n = 341; the genomic DNA of the remaining 29 isolates was not restricted by SmaI), 48 distinct PFGE types were recognized, of which 31 were recorded in only one isolate (one-strain types). Fifty-two percent of typable isolates fell into three type clusters and 75% into six, suggesting that erythromycin-resistant group A streptococci circulating in Italy are polyclonal, but the majority of them probably derives from the spread of a limited number of clones. In parallel experiments, the 370 test strains were characterized for the macrolide resistance phenotype: 80 were assigned to phenotype cMLS, 89 to phenotype iMLS-A, 33 to phenotype iMLS-B, 11 to phenotype iMLS-C, and 157 to phenotype M. There was a close correlation between these phenotypic data and the genotypic results of PFGE analysis, the vast majority of the isolates assigned to individual PFGE classes belonging usually to a single phenotype of macrolide resistance. All of the 29 untypable isolates belonged to the M phenotype. Further correlations were observed with tetracycline resistance.
    Microbial Drug Resistance 01/2001; 7(1):65-71. · 2.36 Impact Factor
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    ABSTRACT: Twelve clinical strains of Staphylococcus haemolyticus (eight methicillin resistant and three methicillin susceptible), isolated from blood cultures between 1982 and 1997, were investigated for teicoplanin and vancomycin susceptibility profiles. On the basis of conventional MIC tests and breakpoints, four isolates were susceptible (MICs, 1 to 8 microgram/ml) and eight were resistant (MICs, 32 to 64 microgram/ml) to teicoplanin while all were susceptible to vancomycin (MICs, 1 to 2 microgram/ml). All four strains for which the conventional teicoplanin MICs were within the range of susceptibility expressed heterogeneous resistance to teicoplanin and homogeneous vancomycin susceptibility. Of the eight strains for which the conventional teicoplanin MICs were within the range of resistance, six expressed heterogeneous and two expressed homogeneous teicoplanin resistance while seven showed heterogeneous vancomycin resistance profiles (with subpopulations growing on 8 microgram of the drug per ml at frequencies of >/=10(-6) for six strains and 10(-7) for one) and one demonstrated homogeneous vancomycin susceptibility. Of six bloodstream isolates of other staphylococcal species (S. aureus, S. epidermidis, and S. simulans), for all of which the conventional teicoplanin MICs were >/=4 microgram/ml and the vancomycin MICs were </=2 microgram/ml, none exhibited heterogeneous susceptibility profiles for teicoplanin while three showed homogeneous and three showed heterogeneous susceptibility profiles for vancomycin (with subpopulations growing on 8 microgram of the drug per ml found for only one strain). The results of this study indicate that a heterogeneous response to glycopeptides is a common feature of S. haemolyticus isolates and suggest that susceptibility to glycopeptides as determined by conventional MIC tests may not be predictive of the outcome of glycopeptide therapy.
    Antimicrobial Agents and Chemotherapy 11/2000; · 4.57 Impact Factor
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    ABSTRACT: A multicenter survey was performed to evaluate a new semi-automated human immunodeficiency virus fourth generation antibodies and antigen simultaneous assay. This assay showed a sensitivity of 100% and specificity of 99.6% among sera obtained from hospitalized patients or blood donors. Sera obtained from commercially available as well as in-house seroconversions were tested showing that HIV DUO is able to reveal an infected state in 11 out of 14 cases earlier than conventional tests. This new assay improves old test performances in terms of sensitivity, maintaining specificity at very high levels.
    The New Microbiologica: official journal of the Italian Society for Medical Virology (SIVIM) 11/2000; 23(4):357-65. · 1.67 Impact Factor

Publication Stats

2k Citations
683.30 Total Impact Points


  • 2005
    • Università Politecnica delle Marche
      Ancona, The Marches, Italy
  • 1980–2005
    • Università degli Studi di Genova
      Genova, Liguria, Italy
  • 2003
    • University of Catania
      Catania, Sicily, Italy
  • 2001
    • Istituto Superiore di Sanità
      Roma, Latium, Italy
    • University of Camerino
      Camerino, The Marches, Italy
  • 1996–2000
    • Università degli Studi di Trieste
      Trst, Friuli Venezia Giulia, Italy
    • University of Washington Seattle
      • Department of Pathology
      Seattle, WA, United States
  • 1992–2000
    • Università degli Studi di Siena
      Siena, Tuscany, Italy
  • 1998
    • Molecular and Cellular Biology Program
      Seattle, Washington, United States
  • 1993–1997
    • Catholic University of the Sacred Heart
      • Institute of Microbiology
      Roma, Latium, Italy
  • 1991
    • University of Padova
      • Department of Biology
      Padova, Veneto, Italy
  • 1989
    • CRO Centro di Riferimento Oncologico di Aviano
      Aviano, Friuli Venezia Giulia, Italy