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2.  European Emergence of Ciprofloxacin-Resistant Escherichia coli Clonal Groups O25:H4-ST 131 and O15:K52:H1 Causing Community-Acquired Uncomplicated Cystitis▿  
Journal of Clinical Microbiology  2008;46(8):2605-2612.
A total of 148 E. coli strains displaying reduced susceptibility to ciprofloxacin (MIC ≥ 2 μg/ml) and causing uncomplicated urinary tract infections in eight European countries during 2003 to 2006 were studied. Their phylogenetic groups, biochemical profiles, and antibiotic susceptibilities were determined. Determination of the O:H serotype, pulsed-field gel electrophoresis (PFGE), randomly amplified polymorphic DNA (RAPD) PCR, and multilocus sequence typing provided additional discrimination. The majority (82.4%) of the microorganisms (122/148) carried resistance to two or more additional drugs, with the pattern ciprofloxacin-trimethoprim-sufamethoxazole-tetracycline-ampicillin being the most represented (73 strains out of 148; 49.3%). Extended-spectrum beta-lactamase production was detected in 12/148 strains (8.1%), with CTX-M-15 being the most-common enzyme. Six strains out of the whole collection studied (4.0%) contained a qnrB-like gene. Overall, 55 different PFGE or RAPD PCR profiles could be distinguished, indicating a substantial heterogeneity. However, about one-third (51/148) of the strains belonged to two clonal groups: O15:K52:H1 (phylogenetic group B2, lactose-nonfermenting variant, ciprofloxacin MIC of 16 μg/ml) and O25:H4 sequence type 131 (ST-131) (phylogenetic group D, ciprofloxacin MIC of ≥32 μg/ml). With the exception of Poland, strains of these two groups were isolated in samples from all participating countries but more frequently in samples from Spain and Italy. In some representative strains of the two main clonal groups, alterations in GyrA and ParC were the basic mechanism of fluoroquinolone resistance. In some members of the O25:H4 ST-131 group, displaying a ciprofloxacin MIC of >32 μg/ml, additional OmpF loss or pump efflux overexpression was found. In the Mediterranean area, strains belonging to these two clonal groups played a major role in determining the high rate of fluoroquinolone-resistant E. coli strains observed in the community.
PMCID: PMC2519467  PMID: 18579721
3.  Postantibiotic Effect and Delay of Regrowth in Strains Carrying Mutations That Save Proteins or RNA 
Antimicrobial Agents and Chemotherapy  2002;46(12):4022-4025.
The postantibiotic effect (PAE) values found for proteinase-defective (Lon−) Escherichia coli and RNase-defective E. coli exposed to antibiotics were reduced (31 to 60% and 35 to 50%, respectively) in comparison with the control (AB1157), and in the recA13 mutant these values were about 0.4 h with all drugs. Nalidixic acid, under anaerobic conditions, induced no PAE (0 to 0.1 h) in AB1157. A delay in regrowth (0.2 to 0.26 h) was noted with dnaA46(Ts), gyrA43(Ts), and gyrB41(Ts) mutants cultured for 2 h at 43°C. These findings suggest that when proteins and RNA are saved, the cell rapidly resumes the original growth rate.
PMCID: PMC132785  PMID: 12435717
4.  Nasopharyngeal Carriage of Streptococcus pneumoniae in Healthy Children: Implications for the Use of Heptavalent Pnemococcal Conjugate Vaccine 
Emerging Infectious Diseases  2002;8(5):479-484.
We assessed the prevalence of Streptococcus pneumoniae serotypes in the nasopharynx of healthy children, antimicrobial susceptibility patterns, risk factors for carriage, and the coverage of heptavalent pneumococcal conjugate vaccine. In 2,799 healthy infants and children, the S. pneumoniae carrier rate was 8.6% (serotypes 3, 19F, 23F, 19A, 6B, and 14 were most common). Most pneumococci (69.4%) were resistant to one or more antimicrobial classes. The rate of penicillin resistance was low (9.1%); macrolide resistance was high (52.1%). Overall, 63.2% of the isolates belonged to strains covered by the heptavalent pneumococcal vaccine. This percentage was higher in children <2 years old (73.1%) and in those >2-5 years old(68.9%). Sinusitis in the previous 3 months was the only risk factor for carrier status; acute otitis media was the only risk factor for the carriage of penicillin-resistant S. pneumoniae. Most the isolated strains are covered by the heptavalent conjugate vaccine, especially in the first years of life, suggesting that its use could reduce the incidence of pneumococcal disease.
PMCID: PMC2732490  PMID: 11996682
Streptococcus pneumoniae; nasopharyngeal carriage; epidemiology; conjugate vaccine; children
5.  In Vitro Activity of the New Ketolide Telithromycin Compared with Those of Macrolides against Streptococcus pyogenes: Influences of Resistance Mechanisms and Methodological Factors 
Antimicrobial Agents and Chemotherapy  2000;44(11):2999-3002.
One hundred and seven clinical isolates of Streptococcus pyogenes, 80 susceptible to macrolides and 27 resistant to erythromycin A (MIC >0.5 μg/ml), were examined. The erythromycin A-lincomycin double-disk test assigned 7 resistant strains to the M-phenotype, 8 to the inducible macrolide, lincosamide, and streptogramin B resistance (iMLSB) phenotype, and 12 to the constitutive MLSB resistance (cMLSB) phenotype. MICs of erythromycin A, clarithromycin, azithromycin, roxithromycin, and clindamycin were determined by a broth microdilution method. MICs of telithromycin were determined by three different methods (broth microdilution, agar dilution, and E-test methods) in an ambient air atmosphere and in a 5 to 6% CO2 atmosphere. Erythromycin A resistance genes were investigated by PCR in the 27 erythromycin A-resistant isolates. MICs of erythromycin A and clindamycin showed six groups of resistant strains, groups A to F. iMLSB strains (A, B, and D groups) are characterized by two distinct patterns of resistance correlated with genotypic results. A- and B-group strains were moderately resistant to 14- and 15-membered ring macrolides and highly susceptible to telithromycin. All A- and B-group isolates harbored erm TR gene, D-group strains, highly resistant to macrolides and intermediately resistant to telithromycin (MICs, 1 to 16 μg/ml), were all characterized by having the ermB gene. All M-phenotype isolates (C group), resistant to 14- and 15-membered ring macrolides and susceptible to clindamycin and telithromycin, harbored the mefA gene. All cMLSB strains (E and F groups) with high level of resistance to macrolides, lincosamide, and telithromycin had the ermB gene. The effect of 5 to 6% CO2 was remarkable on resistant strains, by increasing MICs of telithromycin from 1 to 6 twofold dilutions against D-E- and F-group isolates.
PMCID: PMC101592  PMID: 11036012
6.  Molecular Epidemiology of Penicillin-Resistant Streptococcus pneumoniae Isolates Recovered in Italy from 1993 to 1996 
Journal of Clinical Microbiology  1998;36(10):2944-2949.
Thirty-nine penicillin-resistant Streptococcus pneumoniae isolates recovered among the approximately 700 pneumococcal strains collected from 1993 to 1996 in central and northern Italy were analyzed for several characteristics, including serotype, antibiotic susceptibility profile, chromosomal relatedness (by using pulsed-field gel electrophoresis [PFGE]), restriction fragment length polymorphism (RFLP) of the penicillin-binding protein (PBP) genes 1A, 2X, and 2B, and the presence of a variety of antibiotic resistance genes (determined by hybridization with appropriate DNA probes). The MICs of penicillin for most of the isolates (30 of 39) were high, in the range of 1 μg/ml or higher, and these 30 isolates carried additional resistance traits to two or more drugs (erythromycin, chloramphenicol, co-trimoxazole, and tetracycline) and expressed serotypes 9, 19, and 23 and three distinct PFGE patterns. More than half (22 of 30) of the isolates for which MICs were high were identified as representatives of two widespread international epidemic clones of S. pneumoniae. The first one of these clones (seven isolates) expressed serotype 23F and possessed all properties characteristic of the widespread Spanish/USA international clone. Seven additional strains with serotype 19 also had the same PFGE pattern, PBP gene, and RFLP polymorphisms, and other properties typical of the serotype 23 Spanish/USA clone, suggesting that these strains were the products of a capsular transformation event (from serotype 23F to serotype 19) in which the Spanish/USA clone was the recipient. The second international clone was represented by eight serotype 9 isolates which were resistant to penicillin and trimethoprim-sulfamethoxazole and had the molecular properties of the French/Spanish epidemic clone. The remaining eight isolates for which penicillin MICs were high appeared to represent a hitherto-undescribed “Italian” clone; they had a novel PFGE type, unique RFLPs for the PBP genes, and resistance to tetracycline, trimethoprim-sulfamethoxazole, and erythromycin, and the penicillin MICs for these isolates were 2 to 4 μg/ml.
PMCID: PMC105092  PMID: 9738048
7.  Characterization of FOX-3, an AmpC-Type Plasmid-Mediated β-Lactamase from an Italian Isolate of Klebsiella oxytoca 
Klebsiella oxytoca 1731, which showed a wide spectrum of resistance to β-lactams, including cefoxitin, was isolated in 1994 from a patient in Genoa, Italy. This strain contained a plasmid-mediated AmpC β-lactamase with a pI of 7.25. Sequencing of the corresponding DNA of K. oxytoca 1731 revealed 96 and 97% identities of the deduced amino acid sequence with FOX-1 and FOX-2, respectively.
PMCID: PMC105438  PMID: 9527810
8.  Development of Coliphage N4: Ultrastructural Studies 
Journal of Virology  1974;13(1):186-196.
The basic properties of bacteriophage N4 development have been investigated in Escherichia coli Hfr 3300 under one-step growth and high cell density conditions. N4r+ -infected bacteria are lysis inhibited in mass culture, burst asynchronously starting 180 min postinfection, and release over 3,000 phage per cell. During lysis inhibition the bacteria continuously elongate, increase in girth, and undergo characteristic morphological changes represented by the appearance of dark spots located at the cell poles. In thin sections, during the late stages of replication and assembly, the phage particles are localized exclusively in restricted areas of the cytoplasm near the polar regions. Large paracrystalline arrays of virions are found in over 7% of the cells before lysis. The most common mechanism of lysis consists in the formation of bulges located at random in the cell circumference; these burst and, without extensive disruption of the cell wall, the phage progeny escapes into the medium.
PMCID: PMC355274  PMID: 4129839

Results 1-8 (8)